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Patent US6770346 - Optical recording medium and recording method - Google PatentsSearch Images Maps Play YouTube News Gmail Drive More »Sign in<nobr>Advanced Patent Search</nobr>PatentsAn optical recording medium comprising a recording layer which comprises a phase-change recording material causing a reversible phase change between a crystalline phase and an amorphous phase by irradiation with an electromagnetic wave, wherein the phase-change recording material mainly comprises materials...http://www.google.com/patents/US6770346?utm_source=gb-gplus-sharePatent US6770346 - Optical recording medium and recording methodAdvanced Patent SearchPublication numberUS6770346 B2Publication typeGrantApplication numberUS 10/151,324Publication dateAug 3, 2004Filing dateMay 20, 2002Priority dateMay 21, 2001Fee statusLapsedAlso published asDE60222322D1, DE60222322T2, EP1260973A2, EP1260973A3, EP1260973B1, EP1686575A2, EP1686575A3, EP1703497A2, EP1703497A3, US20030012917Publication number10151324, 151324, US 6770346 B2, US 6770346B2, US-B2-6770346, US6770346 B2, US6770346B2InventorsMakoto Harigaya, Hiroshi Miura, Hiroko Okura, Miku Mizutani, Eiko Hibino, Hajime Yuzurihara, Yoshiyuki Kageyama, Mikiko Abe, Hiroshi Deguchi, Kazunori ItoOriginal AssigneeRicoh Company, Ltd.Export CitationBiBTeX, EndNote, RefManPatent Citations (29), Non-Patent Citations (9), Referenced by (15), Classifications (21), Legal Events (5) External Links: USPTO, USPTO Assignment, EspacenetOptical recording medium and recording methodUS 6770346 B2Abstract An optical recording medium comprising a recording layer which comprises a phase-change recording material causing a reversible phase change between a crystalline phase and an amorphous phase by irradiation with an electromagnetic wave, wherein the phase-change recording material mainly comprises materials expressed by the composition formula XαGeβMnγSbδTeε with each of the components respectively fulfills 0≦α≦5, 1≦β≦5, 1≦γ≦10, 65 ≦δ<80, 15≦ε≦25, and α≦γ (where X expresses at least one of Ga and Sn, α, β, γ, δ, and ε expresses atomic percentage, and fulfills α+β+γ+δ+ε=100).
(where X expresses at least one of Ga and Sn, α, β, γ, δ, and ε expresses atomic percentage, and fulfills α+β+γ+δ+ε=100). 2. An optical recording medium according to claim 1, wherein a crystallization temperature at temperature rise rate of 10� C./min of the recording layer is 150-220� C.
13. An optical recording medium according to claim 11, wherein a statistic Na�Cl structure which is the structure of the crystalline phase of the recording layer is distorted.
14. An optical recording medium according to claim 11, wherein a crystallization temperature at temperature rise rate of 10� C./min of the recording layer is 150-200� C.
15. An optical recording medium according to claim 11, wherein a melting point of the recording layer is 530-560� C.
a recording layer which comprises a phase-change recording material causing a reversible phase change between a crystalline phase and an amorphous phase by irradiation with an electromagnetic wave; wherein the phase-change recording material mainly comprises materials expressed by the composition formula AφDχSbφTeω, and each of the components fulfills following quantities, and a crystallization temperature of the recording layer at temperature rise rate of 10� C./min is less than 240� C.; 2≦φ≦8 3≦χ≦10 60≦φ≦80 15≦ω≦30 (where A expresses at least one element selected from Ge, B and C; D expresses one or a plurality of elements having a ratio of ionicity to Te within the range of 5-28%; φ, χ, φ, and ω each expresses atomic percentage, and φ+χ+φ+ω+=100). 18. An optical recording medium according to claim 17, wherein the element D is selected from Al, Ga, Zn, Mn, Ta, Zr, Y, Mg, Ca, Br and Cl.
As one of optical information recording media which is recordable, reproducible, and erasable of information by irradiation of laser beam, a so-called phase-change optical recording medium utilizing transition between crystal-amorphous phase or crystal�crystal phase is well known. Such recording medium has been utilized as recording medium for computers or image and sound related devices for its capability of overwriting with single beam and for its simple structure compared to an optical system of a drive unit.
The recording materials thereof include GeTe, GeTeSe, GeTeS, GeSeS, GeSeSb, GeAsSe, InTe, SeTe, SeAs, Ge�Te�(Sn, Au, Pd), GeTeSeSb, GeTeSb, Ag�In�Sb�Te, and the like. Particularly, Ag�In�Sb�Te has characteristic of high sensitivity and a clear profile of amorphous part, and is developed as a recording layer for mark edge recording.
In Japanese Patent Application Laid-Open No. 3-231889, for example, a recording layer represented by an I�(III1−γV γ)�VI type general formula wherein I is an element of the group I, III is an element of the group III, V is an element of the group V, and VI is an element of the group VI is disclosed. However, such a recording layer has a problem in repetitive recording property.
When the crystallization rate (or crystallization speed) is too high, however, the amorphous phase is difficult to form. In this case, the medium structure may be arranged to form a quench structure, but the recording power is also required. In Ag�In�Sb�Te series and Sb�Te eutectic series, although the crystallization rate can be increased by increasing Sb quantity, it makes difficult to form the amorphous phase, and also deteriorates the storage property under high-temperature environment of mark, if an increase in the quantity is too much. When the medium structure is arranged to form the quench structure, a problem of deficiency in sensitivity arises. The causes of the deterioration in repetitive recording property in the high-speed recording include deterioration of not only the recording layer but also the upper protection layer located between the recording layer and the reflection layer, or dispersion of the constituting elements in the recording film or cracking of the protection layer by thermal impact, due to repetition of heating under high temperature and cooling in a short time. To cope with the speed up, studying of recording layer material, protection layer material and reflection layer material are required. For the same reason, study of recording method is also necessary.
SUMMARY OF THE INVENTION An object of the present invention is to provide a phase-change optical recording medium which performs a high-density recording at extensive linear velocities ranging from 3.5 m/s to a maximum of about 20 m/s, specifically 2 to 5-fold velocity (7.0-17.5 m/s) of the DVD, and further, to a phase-change optical recording medium easy in initial crystallization and excellent in repetition and storage properties, and a recording method thereof.
BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a cross-sectional view showing a basic structural example of optical recording media according to the present invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention is further described in detail.
Ge can improve the storage property of the recorded mark under high temperature environment although the crystallization rate is low. It has satisfying storage property due to particularly large bonding energy between the Ge�Te and increased crystallization temperature accompanying addition of the Ge. However, since the excessive addition leads to a further rise of crystallization temperature whereas deteriorates the crystallization rate, the adding quantity has a limitation. Accordingly, the Ge quantity β is preferably determined to meet 1≦β≦5.
The elements having the same effect as In includes Ga. Ga increases the crystallization rate as compared with In of the same quantity, however cannot be added so much since the crystallization temperature also increases. When Ge is 5 atomic percentage, and Ga is 6 atomic percentage or more, the crystallization temperature exceeds 200� C. by far and reaches as high as 250� C. or higher. Therefore, in the initialization process for crystallizing the recording layer from the amorphous state, when the reflection ratio is reduced, the reflection ratio distribution of a round of track is increased, thereby causing deterioration of recording property or data error, hence the initialization becomes difficult. Accordingly, Ga preferably does not exceed 5 atomic percentage in combined use with Ge as adopted in this embodiment.
To obtain a recording layer easily initializable and having satisfying recording property, the crystallization temperature at temperature rise rate of 10� C./min is preferably determined within the range of 150-220� C. When the temperature is lower than 150� C., the recording mark is easily erased under high temperature environment. When the temperature exceeds 220� C., a uniform crystalline phase cannot be formed at initialization, and leads to deterioration in the recording property, or unobtainable reflection ratio necessary due to insufficient crystal growth. The crystallization temperature at temperature rise rate of 10� C./min., referred herein means the temperature rise rate in measurement by differential scanning calorimetric analyzing method.
Consequently, Sb�Te bond, Sb�Sb bond, Te�Te bond, Te�Ge bond, Te�Ga bond, and Te�Mn bond are formed. Since bond distance of adjoining atoms around Sb is longer than the bond distance of adjoining atoms around Te on the basis of analysis in the local structure by X-ray or the like, the structure is locally distorted.
When the crystallization temperature at temperature rise rate of 10� C./min is less than 150� C., the storage property deteriorates, and when the crystallization temperature exceeds 200� C., initial crystallization becomes difficult.
When the crystallization rate is high, the sensitivity tends to be insufficient because higher cooling rate is required to obtain the amorphous. In the present invention, however, the sensitivity can be improved without sacrificing other properties for recording materials having melting points of 530-560� C. When the melting point is less than 530� C., the storage property and stability of reproducing light deteriorate, and when the melting point exceeds 560� C., the sensitivity deteriorates.
Although the recording material consisting only of Sb and Te has excellent repetition property when the composition is an eutectic composition of Sb70Te30, however, there is a problem in that the storage property deteriorates because of the crystallization temperature of about 120� C., that the crystallization of the recording mark is caused to erase the mark in the long run.
Thus, when an element (Al, Ga, Zn, Mn, Ta, Zr, Y, Mg, Ca, Br, or Cl) having ionicity to Te within the range of 5-28% was added to the Sb�Te recording material, satisfying result was obtained.
I=1−exp[−1/4(XTe−Xn)2] (where XTe is the electronegativity of Te, and Xn is the electronegativity of the other element).
On the other hand, when the crystallization temperature of the recording layer at temperature rise rate of 10� C./min exceeds 240� C., initial crystallization becomes difficult, and therefore, 220� C. or less is preferred.
Medium was produced by using these upper protection layers, and examined for the storage property of recording mark at 80� C. and 85% RH after recording. Consequently, the mark was erased in case of ZrO2.Y2O3 (mole ratio 97:3). However, the repetitive overwrite property of ZrO2-based ones is satisfying, and the jitter deterioration after 1000 recordings was less than in ZnS.SiO2 (mole ratio 80:20).
EXAMPLES The present invention will be concretely described below using Examples and Comparative Examples, but the present invention should not be construed as limited by these examples.
Examples 1-15 Using polycarbonate substrate having a channel pitch of 0.74 μm, a channel width of 2.5 μm, a channel depth of 25 nm, and a thickness of 0.6 mm, recording medium was produced by laminating each layer thereon by sputtering.
Thereafter, the recording layer was crystallized by using a large aperture LD (1 μm in track direction�196 μm in radial direction) at a linear velocity of 3.5 m/s, a power of 850 mW, and a head feeding speed of 36 μm/r. A pickup head with wavelength 657 nm and objective lens NA 0.65 was used for recording and reproducing so that the recording density becomes 0.267 μm/bit at a linear velocity of 17.5 m/s. Recording data were recorded by (8-16) modulation at a recording power of 19 mW, a bias power of 0.1 mW, and an erasing power of 6 mW.
The jitter rise value (%) in leaving under high-temperature, high-humidity environment at 80� C. and 85% RH for 300 hrs after 10 recordings and the defective ratio after repeating the cycle of retaining at 25� C. and 95% RH for 6 hrs and further retaining at 40� C. and 95% RH for 6 hrs 6 times were examined. The results are shown in Table 1, wherein, as the evaluation criteria for defective ratio, a defective ratio of 10−5 or less is shown as �◯�, and the ones exceeding this value or the presence of a visually confirmable defective is shown as �x�.
Comparative Examples 1-3 Recording medium was formed in the same manner as in Example 1 except that the recording layer was changed to AgInSbTe, AlTi (Comparative Examples 1 and 2) as the reflection layer was used, and providing no second upper protection layer.
The jitter rise value (%) measured in the same condition as in Example 1, and the defective ratio examined in the same condition and evaluated on the basis of the same criteria are also shown in Table 1. The jitter was significantly raised in Comparative Examples 1 and 2, compared with Examples 1-15, and the evaluation of defective ratio was �x� in Comparative Example 3.
Example 16 The recording medium having the layer structure of Example 4 was subjected to recording by a method shown in FIG. 5.
dTtop=�0.1T�n′;
Ttop=(T/12)�n′+0.5�m′;
Tmp=(T/12)�n′+0.5�m′;
T1p=(T/12)�n′+0.5�m′; and
dTc1=0.05T�n′
Comparative Example 4 The recording medium of Comparative Example 1 was subjected to recording in the same condition as in Example 16. The modulation factor was 63%, which was lower than in Example 16, and the jitter was also higher by 2% than in Example 16.
Example 17 The recording was performed in the same manner as in Example 16 except determining the bottom power Pb at 0.7 mW, which is the same rate as the reproducing power Pr. The result is shown in FIG. 9. The jitter was improved by about 1% irrelevant to recording frequency.
Example 18 The recording was performed using the same recording media as in Examples 16 and 17 under the same condition.
Examples 19-26 and Comparative Examples 5-8 A polycarbonate substrate having a track pitch of 0.74 μm, a channel depth of 40 nm, a thickness of 0.6 mm, and a diameter of 120 mm φ was dehydrated at high temperature, and a lower protection layer, a recording layer, an upper protection layer, an upper second protection layer and a reflection layer were successively formed thereon by sputtering (FIG. 2).
The lower protection layer was formed in a thickness of 70 nm by use of a ZnS�SiO2 target.
For the recording layer, an alloy target obtained comprised of prescribed composition ratio, pulverized and sintered was used, and the recording layer was formed in a thickness of 18 nm by sputtering at argon gas pressure of 3�10−3 Torr and RF power of 300 mW.
The upper protection layer was formed in a thickness of 15 nm by use of a ZnS�SiO2 target.
The crystal structure of the recording layer was structurally analyzed by X-ray diffraction method and electron beam diffraction method. The �distorted NaCl-type structure� means a structure having turbulences allowing entrance of every atom constituting the recording layer in Na-site and Cl-site, so that the NaCl-type structure is distorted.
The archival is shown as the increase ratio to initial value of σ after storage at 80� C. for 300 hrs.
For the initial crystallization, �◯� was given when the reflection ratio after initial crystallization is uniform in plane, and �difficult� was entered when the reflection ratio showed distribution.
The crystallization temperature at a temperature increasing rate of 10� C./min was measured by use of a differential scanning calorimetric device.
In Examples 19-26, the recording layer composition was designed so as to have a linear rotation rates of 17/s, a melting point of 530-560� C., and a crystallization temperature of 150-200� C. to form a single film and medium.
The locally distorted structure is conceivably formed since the turbulences allowing the entrance of every atom constituting the recording layer are present in the Na-site and Cl-site, as mentioned earlier, whereby Sb�Te bond, Sb�Sb bond, Te�Te bond, Te�Ga bond, Te�Ge bond, or Te�Mn bond is generated and varies adjacent bonding distances.
This medium was initially crystallized, however the reflection rate after initial crystallization was not uniform in plan. The reason for this phenomenon is presumed that the initial crystallization was difficult due to a high crystallization temperature of 240� C.
80� C., 300 hr
Examples 27-38 and Comparative Examples 9-12 In order to produce recording media having structures shown in Table 5, a lower protection layer, a recording layer, an upper protection layer, and a reflection layer were successively provided by sputtering on a polycarbonate substrate having a track pitch of 0.7 μm, a channel depth of 40 nm, a thickness of 0.6 mm, and a diameter of 120 mm φ.
The storage property was evaluated with the jitter value of the 3T signal of the initial recording (first overwrite) after retaining the initially recorded recording media under 80� C. and 85% RH for 300 hrs.
Note 1: Jitter value of 3T recording mark in first overwriting after retaining at 80� C. and 85% RH for 300 hrs. TABLE 7
Note 1: Jitter value of 3T recording mark in first overwriting after retaining at 80� C., 85% RH for 300 hrs. As is apparent from Tables 6 and 7, in the recording medium of the third embodiment of the present invention, the overwrite property and storage property under a high linear velocity are extremely satisfying when its recording layer is formed of Te, Sb, at least one element selected from B, C and Ge, and at least one element selected from Al, Ga, Zn, Mn, Ta, Zr, Y, Mg, Ca, Br and Cl among elements other then the above elements and having ratios of ionicity to Te within 5-28%.
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examinerClassifications U.S. Classification428/64.1, 430/270.13, 428/64.5, G9B/7.142International ClassificationG11B7/254, G11B7/258, G11B7/125, G11B7/006, B41M5/26, G11B7/0045, G11B7/257, G11B7/24, G11B7/243Cooperative ClassificationG11B2007/24308, G11B7/243, G11B2007/24314, G11B2007/24312, G11B7/0062, G11B2007/24316European ClassificationG11B7/243, G11B7/006SLegal EventsDateCodeEventDescriptionSep 25, 2012FPExpired due to failure to pay maintenance feeEffective date: 20120803Aug 3, 2012LAPSLapse for failure to pay maintenance feesMar 19, 2012REMIMaintenance fee reminder mailedJan 11, 2008FPAYFee paymentYear of fee payment: 4Aug 26, 2002ASAssignmentOwner name: RICOH COMPANY, LTD., JAPANFree format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNORS:HARIGAYA, MAKOTO;MIURA, HIROSHI;OKURA, HIROKO;AND OTHERS;REEL/FRAME:013228/0067;SIGNING DATES FROM 20020528 TO 20020530Owner name: RICOH COMPANY, LTD. 3-6, NAKAMAGOME 1-CHOME OHTA-KFree format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNORS:HARIGAYA, MAKOTO /AR;REEL/FRAME:013228/0067;SIGNING DATES FROM 20020528 TO 20020530RotateOriginal ImageGoogle Home - Sitemap - USPTO Bulk Downloads - Privacy Policy - Terms of Service - About Google Patents - Send FeedbackData provided by IFI CLAIMS Patent Services©2012 Google