U.S. patent application number 10/971142 was filed with the patent office on 2005-05-26 for aluminum-alloy reflection film for optical information-recording, optical information-recording medium, and aluminum-alloy sputtering target for formation of the aluminum-alloy reflection film for optical information-recording.
This patent application is currently assigned to Kabushiki Kaisha Kobe Seiko Sho(Kobe Steel, Ltd.). Invention is credited to Nakai, Junichi, Takagi, Katsutoshi, Tauchi, Yuuki.
Application Number | 20050112019 10/971142 |
Document ID | / |
Family ID | 34420205 |
Filed Date | 2005-05-26 |
United States Patent
Application |
20050112019 |
Kind Code |
A1 |
Nakai, Junichi ; et
al. |
May 26, 2005 |
Aluminum-alloy reflection film for optical information-recording,
optical information-recording medium, and aluminum-alloy sputtering
target for formation of the aluminum-alloy reflection film for
optical information-recording
Abstract
There are provided an aluminum-alloy reflection film for optical
information-recording, having low thermal conductivity, low melting
temperature, and high corrosion resistance, capable of coping with
laser marking, an optical information-recording medium comprising
the reflection film described, and an aluminum-alloy sputtering
target for formation of the reflection film described. The
invention includes (1) an aluminum-alloy reflection film for
optical information-recording, containing an element Al as the main
constituent, 1.0 to 10.0 at. % of at least one element selected
from the group of rare earth elements, and 0.5 to 5.0 at. % of at
least one element selected from the group consisting of elements
Cr, Ta, Ti, Mo, V, W, Zr, Hf, Nb, and Ni, (2) an optical
information-recording medium comprising any of the aluminum-alloy
reflection films described as above, and (3) a sputtering target
having the same composition as that for any of the aluminum-alloy
reflection films described as above.
Inventors: |
Nakai, Junichi; (Kobe-shi,
JP) ; Tauchi, Yuuki; (Kobe-shi, JP) ; Takagi,
Katsutoshi; (Kobe-shi, JP) |
Correspondence
Address: |
OBLON, SPIVAK, MCCLELLAND, MAIER & NEUSTADT, P.C.
1940 DUKE STREET
ALEXANDRIA
VA
22314
US
|
Assignee: |
Kabushiki Kaisha Kobe Seiko
Sho(Kobe Steel, Ltd.)
Kobe-shi
JP
|
Family ID: |
34420205 |
Appl. No.: |
10/971142 |
Filed: |
October 25, 2004 |
Current U.S.
Class: |
420/550 ;
420/552; G9B/7.19 |
Current CPC
Class: |
G11B 7/2585 20130101;
G11B 7/258 20130101; C23C 14/14 20130101; C23C 14/3414
20130101 |
Class at
Publication: |
420/550 ;
420/552 |
International
Class: |
C22C 021/00 |
Foreign Application Data
Date |
Code |
Application Number |
Oct 30, 2003 |
JP |
2003-370740 |
Claims
What is claimed is:
1. An aluminum-alloy reflection film for optical
information-recording, said aluminum-alloy reflection film,
containing: an element Al as the main constituent; 1.0 to 10.0 at.
% of at least one element selected from the group of rare earth
elements; and 0.5 to 5.0 at. % of at least one element selected
from the group consisting of elements Cr, Ta, Ti, Mo, V, W, Zr, Hf,
Nb, and Ni.
2. An aluminum-alloy reflection film for optical
information-recording according to claim 1, wherein the rare earth
elements are elements Nd and/or Y.
3. An aluminum-alloy reflection film for optical
information-recording according to claim 1, containing 1.0 to 5.0
at. % of at least one element selected from the group consisting of
elements Fe, and Co.
4. An aluminum-alloy reflection film for optical
information-recording according to claim 1, containing 1.0 to 10.0
at. % of at least one element selected from the group consisting of
elements. In, Zn, Ge, Cu, and Li.
5. An aluminum-alloy reflection film for optical
information-recording according to claim 1, containing not more
than 5.0 at. % of at least one element selected from the group
consisting of elements Si, and Mg.
6. An optical information-recording medium comprising an
aluminum-alloy reflection film for optical information-recording,
according to claim 1.
7. An optical information-recording medium according to claim 6,
suitable for use in laser marking.
8. An aluminum-alloy sputtering target for formation of an
aluminum-alloy reflection film for optical information-recording,
containing: an element Al as the main constituent; 1.0 to 10.0 at.
% of at least one element selected from the group of rare earth
elements; and 0.5 to 5.0 at. % of at least one element selected
from the group consisting of elements Cr, Ta, Ti, Mo, V, W, Zr, Hf,
Nb, and Ni.
9. An aluminum-alloy sputtering target for formation of an
aluminum-alloy reflection film for optical information-recording,
according to claim 8, containing 1.0 to 5.0 at. % of at least one
element selected from the group consisting of elements Fe, and
Co.
10. An aluminum-alloy sputtering target for formation of an
aluminum-alloy reflection film for optical information-recording,
according to claim 8, containing 1.0 to 10.0 at. % of at least one
element selected from the group consisting of elements In, Zn, Ge,
Cu, and Li.
11. An aluminum-alloy sputtering target for formation of an
aluminum-alloy reflection film for optical information-recording,
according to claim 8, containing not more than 5.0 at. % of at
least one element selected from the group consisting of elements
Si, and Mg.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The invention relates to a technical field concerning an
aluminum-alloy reflection film for optical information-recording,
an optical information-recording medium, and an aluminum-alloy
sputtering target for formation of an aluminum-alloy reflection
film for optical information-recording, and in particular, to a
technical field concerning a reflection film having high
reflectance, together with low thermal conductivity, low melting
temperature, and high corrosion resistance to enable marking of a
disc with the use of a laser, and so forth, after formation of the
disc, in the case of a medium (ROM) for reproducing only,
particularly among optical information-recording media such as CD,
DVD, Blue-ray Disc, HD-DVD, and so forth, a sputtering target for
formation of the reflection film, and an optical
information-recording medium provided with the reflection film.
[0003] 2. Related Art
[0004] There are several kinds of optical discs, and on the basis
of recording reproduction principles, the optical discs are broadly
classified into three kinds, that is, a read only type, write once
type, and rewritable type.
[0005] Among those, an optical disc for reproducing only has a
construction in which a reflection film layer formed of Al, Ag, Au,
and so forth, as a matrix, is provided after forming recording data
at the time of fabrication according to pits and lands provided on
a transparent plastic base body, as shown in FIG. 1 by way of
example, and at the time reading data, data reproducing is executed
by detecting phase difference and reflection difference of a laser
beam emitted to the disc. Further, there is another type of optical
disc for reading data recorded in two layers, fabricated by
laminating two sheets of base members with each other, that is, the
base member with a reflection film layer, and the base member
provided with a translucent reflection layer, over individual
recording pits formed, respectively. With this
recording-reproducing type, a disc face on one side is for data
read only (write and rewrite inhibit), and as an optical disc of
this type, there are cited CD-ROM, DVD-ROM, BD-ROM, HD-DVD-ROM, and
so forth. FIG. 1 is a schematic illustration showing a construction
of an optical disc, in section, and in the figure, reference
numeral 1 denotes a polycarbonate base body, 2 a translucent
reflection layer (Au, Ag alloy, Si), 3 an adhesion layer, 4 a total
reflection film layer (Al alloy), and 5 a UV-curing resin
protection layer.
[0006] Such optical discs for reproducing only are produced on a
large scale by press working using a stamper with an information
pattern formed beforehand at the time when the discs are
fabricated, so that it has been difficult to provide individual
discs with IDs, respectively. However, for the purposes of
prevention of illegal copies of discs, enhancement in traceability
of products in distribution, enhancement in added values, and so
forth, even with the optical discs for reproducing only, there has
been seen a start of a tendency that discs of the level-gate type,
BCA (Burst Cutting Area) type, and so forth, with IDs recorded for
the individual discs, respectively, by use of a dedicated
apparatus, after the formation of the discs, become the norm. At
present, such marking of a disc with an ID is implemented mainly by
a method whereby an aluminum-alloy of a reflection film is melted
by emitting a laser beam to the disc after fabricated, thereby
boring holes in the reflection film.
[0007] For the reflection film of the optical disc for reproducing
only, widespread use has since been made of Al-alloys mainly
according JIS6061 (an Al--Mg alloy), which are large in
distribution quantity as a common structural material, and as such,
are inexpensive.
[0008] However, since the Al-alloys of JIS6061 series are not
material intended for use in applying laser marking thereto, the
following points under (1) and (2) below are yet to be
resolved.
[0009] (1) The Al-alloy is high in thermal conductivity. More
specifically, in order to apply laser marking at a low output, the
thermal conductivity of the reflection film is preferably as low as
possible, however, the Al-alloys of JIS6061 series are too high in
thermal conductivity. Therefore, in the case of applying laser
marking with the use of the Al-alloys of JIS6061 series, in the
present state, there has occurred a problem of the polycarbonate
base body and the reflection film, making up the disc, undergoing
thermal damage because laser output has been excessively large.
[0010] (2) The Al-alloys are low in corrosion resistance. More
specifically, when laser marking is applied, voids are formed after
the laser marking, so that initiation of corrosion occurs to an
Al-alloy film during a constant temperature and moisture test to be
conducted later on.
[0011] As to reduction in thermal conductivity of an Al-alloy
reflection film, there has been disclosed a method of reducing
thermal conductivity by adding elements such as Nb, Ti, Ta, W, Mn,
Mo, and so forth, to Al in, for example, JP-A No. 177639/1992
(Patent document 1) relating to the field of a reflection film for
an opto-magnetic recording. Further, in JP-A No. 12733/1993 (Patent
document 2), there has been disclosed a method of reducing thermal
conductivity by adding at least one element selected from the group
consisting of elements Si, Ti, Ta, Cr, Zr, Mo, Pd, and Pt to Al.
Still further, in JP-A No. 11426/1995 (Patent document 3), there
has been disclosed an alloy film obtained by adding W, or Y to Al.
However, because those reflection films are not developed on the
premise that melting as well as removal of a film is implemented by
emitting a laser beam thereto, there are some which can attain
reduction in thermal conductivity, but, at the same time, rises in
melting temperature while there are others which do not take into
account a problem of the corrosion due to the voids, occurring
after the marking, as described above. Thus, none meeting
requirements as the Al-alloy for use in laser marking has been
provided as yet.
[0012] (Patent document 1) JP-A No. 177639/1992
[0013] (Patent document 2) JP-A No. 12733/1993
[0014] (Patent document 3) JP-A No. 11426/1995
SUMMARY OF THE INVENTION
[0015] As described in the foregoing, the Al-alloy capable of
coping with laser marking needs to have low thermal conductivity,
low melting temperature, and high corrosion resistance.
[0016] However, the Al-alloys of JIS6061 series for use as a
reflection film of an optical disc for reproducing only are high in
thermal conductivity, and low in corrosion resistance, and have
difficulty in coping with laser marking applications in respect of
these points. Further, in the field of the Al alloy reflection film
for the opto-magnetic recording, the Al-alloy reflection films (as
disclosed in Patent documents 1 to 3) so far proposed have
difficulty in coping with the laser marking applications as
described above.
[0017] The present invention has been developed by focusing
attention on those circumstances, and it is therefore an object of
the invention to provide an aluminum-alloy reflection film for
optical information-recording, having low thermal conductivity, low
melting temperature, and high corrosion resistance, and capable of
coping with laser marking, an optical information-recording medium
provided with the aluminum-alloy reflection film, and an
aluminum-alloy sputtering target for formation of the
aluminum-alloy reflection film.
[0018] To that end, the inventor, et al. have continued strenuous
researches, and as a result, have obtained knowledge that a thin
film of an aluminum alloy obtained by causing specific amounts of
specific alloying elements to be contained in aluminum has low
thermal conductivity, low melting temperature, and high corrosion
resistance, and as such, is a reflection thin film layer (metallic
thin film layer) suitable for use as a reflection film for optical
information-recording, capable of coping with laser marking. The
present invention has been developed on the basis of such
knowledge, and the object described as above can be achieved by the
present invention.
[0019] The present invention that has achieved the object described
upon completion as above is concerned with an aluminum-alloy
reflection film for optical information-recording, an optical
information-recording medium, and an aluminum-alloy sputtering
target for formation of the aluminum-alloy reflection film for
optical information-recording. In accordance with a first aspect of
the present invention, there is provided the aluminum-alloy
reflection film for optical information-recording (the
aluminum-alloy reflection film according to first to fifth
inventions), and the present invention in its second aspect
provides the optical information-recording medium (the optical
information-recording medium according to sixth to seventh
inventions), further providing in its third aspect the
aluminum-alloy sputtering target for formation of an aluminum-alloy
reflection film for optical information-recording (the sputtering
target according to eighth to eleventh inventions). Those have the
following makeup, respectively.
[0020] More specifically, the aluminum-alloy reflection film for
optical information-recording according to the first aspect of the
present invention is an aluminum-alloy reflection film for optical
information-recording, serving as an aluminum-alloy reflection film
for use in an optical information-recording medium, said
aluminum-alloy reflection film for optical information-recording,
containing:
[0021] an element Al as the main constituent;
[0022] 1.0 to 10.0 at. % of at least one element selected from the
group of rare earth elements; and
[0023] 0.5 to 5.0 at. % of at least one element selected from the
group consisting of elements Cr, Ta, Ti, Mo, V, W, Zr, Hf, Nb, and
Ni (the first invention).
[0024] With these features, the rare earth elements may be elements
Nd and/or Y (the second invention).
[0025] Any of the aluminum-alloy reflection films for optical
information-recording, described as above, may contain 1.0 to 5.0
at. % of at least one element selected from the group consisting of
elements Fe, and Co (the third invention).
[0026] Any of the aluminum-alloy reflection films for optical
information-recording, described as above, may contain 1.0 to 10.0
at. % of at least one element selected from the group consisting of
elements In, Zn, Ge, Cu, and Li (the fourth invention).
[0027] Any of the aluminum-alloy reflection films for optical
information-recording, described as above, may contain not more
than 5.0 at. % of at least one element selected from the group
consisting of elements Si, and Mg (the fifth invention).
[0028] The optical information-recording medium according to the
second aspect of the present invention comprises any of the
aluminum-alloy reflection films described as above (the sixth
invention).
[0029] The optical information-recording medium described as above
may be suitable for use in laser marking (the seventh
invention).
[0030] The aluminum-alloy sputtering target for formation of an
aluminum-alloy reflection film for optical information-recording,
according to the third aspect of the present invention,
containing:
[0031] an element Al as the main constituent;
[0032] 1.0 to 10.0 at. % of at least one element selected from the
group of rare earth elements; and
[0033] 0.5 to 5.0 at. % of at least one element selected from the
group consisting of elements Cr, Ta, Ti, Mo, V, W, Zr, Hf, Nb, and
Ni (the eighth invention).
[0034] The aluminum-alloy sputtering target for formation of an
aluminum-alloy reflection film for optical information-recording,
described as above, may contain 1.0 to 5.0 at. % of at least one
element selected from the group consisting of elements Fe, and Co
(the ninth invention).
[0035] Any of the aluminum-alloy sputtering targets for formation
of an aluminum-alloy reflection film for optical
information-recording, described as above, may contain 1.0 to 10.0
at. % of at least one element selected from the group consisting of
elements In, Zn, Ge, Cu, and Li (the tenth invention).
[0036] Any of the aluminum-alloy sputtering targets for formation
of an aluminum-alloy reflection film for optical
information-recording, described as above, may contain not more
than 5.0 at. % of at least one element selected from the group
consisting of elements Si, and Mg (the eleventh invention).
[0037] The aluminum-alloy reflection film for optical
information-recording according to the present invention can have
low thermal conductivity, low melting temperature, and high
corrosion resistance, and can be suitably used as a reflection film
for optical information-recording, capable of coping with laser
marking. The optical information-recording medium according to the
present invention comprises the aluminum-alloy reflection film
described, and laser marking can be suitably applied thereto. The
aluminum-alloy sputtering target for formation of an aluminum-alloy
reflection film for optical information-recording, according to the
present invention, can form the aluminum-alloy reflection film
described.
BRIEF DESCRIPTION OF THE DRAWING
[0038] FIG. 1 is a schematic sectional view showing a construction
of an optical disc for reproducing only.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0039] An aluminum-alloy thin-film suitable for laser marking needs
to have low thermal conductivity, low melting temperature, and high
corrosion resistance.
[0040] The inventor, et al. have produced aluminum-alloy sputtering
targets obtained by adding a variety of elements to aluminum,
respectively, and have fabricated aluminum-alloy thin-films of
various compositions by a sputtering method using those sputtering
targets, thereby having examined the composition thereof, and
properties thereof, as a reflection thin film layer, whereupon the
following facts {items (1) to (5) as given below} have been found
out:
[0041] (1) By adding at least one element selected from the group
of rare earth elements, in a range of 1.0 to 10.0 at. % in total,
to aluminum, thermal conductivity can be significantly reduced
without causing a rise in melting temperature (liquid phase line
temperature). If an addition amount of the one element is less than
1.0 at. %, the effect of reduction in thermal conductivity
decreases. If the addition amount of the one element exceeds 10.0
at. %, deterioration in reflectance increases. Among the group of
the rare earth elements, Nd and Y have greater effect of reduction
in thermal conductivity, respectively. Further, as for corrosion
resistance, an advantageous effect obtained by addition of the
above-described rare earth elements only is insufficient.
[0042] (2) By further adding at least one element selected from the
group consisting of elements Cr, Ta, Ti, Mo, V, W, Zr, Hf, Nb, and
Ni, in a range of 0.5 to 5.0 at. % in total, to aluminum while
adding the one element selected from the group of the rare earth
elements, in the range of 1.0 to 10.0 at. % in total, to aluminum,
as above, corrosion resistance can be significantly improved. In
addition, those elements {Cr, Ta, Ti, Mo, V, W, Zr, Hf, Nb, and Ni
(hereinafter referred to also as (Cr to Nb, Ni)) also contribute to
reduction in thermal conductivity. However, because those elements
(Cr to Nb, Ni) cause the melting temperature (liquid phase line
temperature) thereof to considerably rise while causing the
reflectance thereof to deteriorate, an addition amount thereof is
limited, and needs to be not more than 5.0 at. %, preferably not
more than 3.0 at. %. If the addition amount of those elements (Cr
to Nb, Ni) is less than 0.5 at. %, the effect of improvement in
corrosion resistance decreases. Hence, the addition amount is
preferably 1.0 at. % or more. Among those elements (Cr to Nb, Ni),
Cr, Ta, Ti, and Hf are preferably selected in the effect of a
marked improvement in corrosion resistance.
[0043] (3) By adding at least the one element selected from the
group of those elements (Cr to Nb, Ni), in the range of 0.5 to 5.0
at. % in total, to aluminum while at least the one element selected
from the group of the rare earth elements, in the range of 1.0 to
10.0 at. % in total, is added to aluminum, described as above {as
described under item (2) above}, and by further adding thereto at
least one element selected from the group consisting of elements
Fe, and Co, in a range of 1.0 to 5.0 at. % in total, thermal
conductivity can be reduced. If an addition amount of those
elements (Fe, Co) is less than 1.0 at. %, the effect of reduction
in thermal conductivity decreases, and in order to sufficiently
exhibit the effect of reduction in thermal conductivity, not less
than 1.0 at. % of those elements (Fe, Co) are preferably added
thereto. Because of an increase in deterioration of reflectance if
those elements (Fe, Co) are excessively added, and because of ease
with which a sputtering target is produced, the addition amount of
those elements (Fe, Co) is preferably set to not more than 5.0 at.
%.
[0044] (4) By adding at least the one element selected from the
group of those elements (Cr to Nb, Ni), in the range of 0.5 to 5.0
at. % in total, to aluminum while at least the one element selected
from the group of the rare earth elements, in the range of 1.0 to
10.0 at. % in total, is added to aluminum, described as above {as
described under item (2) above}, and by further adding thereto at
least one element selected from the group consisting of elements
In, Zn, Ge, Cu, and Li, in a range of 1.0 to 10.0 at. % in total,
thermal conductivity and melting temperature can be reduced. If an
addition amount of those elements {In, Zn, Ge, Cu, and Li
(hereinafter referred to also as (In to Li)) is less than 1.0 at.
%, the effect of reduction in thermal conductivity, and the effect
of reduction in melting temperature decrease, and in order to
sufficiently exhibit the effect of reduction in thermal
conductivity, and the effect of reduction in melting temperature,
not less than 1.0 at. % of those elements (In to Li) are preferably
added. Because of an increase in deterioration of reflectance if
those elements (In to Li) are excessively added, the addition
amount of those elements (In to Li) is preferably set to not more
than 10.0 at. %.
[0045] (5) By adding at least the one element selected from the
group of those elements (Cr to Nb, Ni), in the range of 0.5 to 5.0
at. % in total, to aluminum while at least the one element selected
from the group of the rare earth elements, in the range of 1.0 to
10.0 at. % in total, is added to aluminum, described as above {as
described under item (2) above}, and by further adding thereto not
more than 5.0 at. % of at least one element selected from the group
consisting of elements Si, and Mg, melting temperature can be
reduced. Further, among those elements (Si, Mg), Si also has the
effect of improvement in corrosion resistance. Further, those
elements (Si, Mg) do not have effect of reduction in thermal
conductivity. In order to sufficiently exhibit the effect of
reduction in melting temperature, not less than 1.0 at. % of those
elements (Si, Mg) are preferably added. Because of an increase in
deterioration of reflectance if those elements (Si, Mg) are
excessively added, and because of ease with which a sputtering
target is produced, an addition amount of those elements (Si, Mg)
is preferably set to not more than 5.0 at. %.
[0046] The invention has been developed based on the knowledge
described as above, and intends to provide an aluminum-alloy
reflection film of the above-described composition, for optical
information-recording, an optical information-recording medium, and
an aluminum-alloy sputtering target for formation of the
aluminum-alloy reflection film for optical
information-recording.
[0047] An embodiment of an aluminum-alloy reflection film for
optical information-recording according to the invention, completed
as described above, is an aluminum-alloy reflection film for use in
the optical information-recording medium, and is an aluminum-alloy
reflection film for optical information-recording, containing Al as
the main constituent, and 1.0 to 10.0 at. % of at least one element
selected from the group of rare earth elements, further containing
0.5 to 5.0 at. % of at least one element selected from the group
consisting of elements Cr to Nb, Ni (Cr, Ta, Ti, Mo, V, W, Zr, Hf,
Nb, and Ni) (a first invention).
[0048] As is evident from the items (1) and (2) above, with the
aluminum-alloy reflection film for optical information-recording,
by adding at least the one element selected from the group of the
rare earth elements, in the range of 1.0 to 10.0 at. % in total,
the thermal conductivity thereof can be significantly reduced
without causing a rise in the melting temperature (liquid phase
line temperature) thereof, and by further adding 0.5 to 5.0 at. %
of at least the one element selected from the group consisting of
elements Cr to Nb, Ni, the corrosion resistance can be
significantly improved, and the thermal conductivity thereof can be
further reduced.
[0049] Accordingly, the aluminum-alloy reflection film for optical
information-recording according to the invention can have low
thermal conductivity, low melting temperature, and high corrosion
resistance, and is capable of excellently coping with laser
marking, so that the same can be used suitably as a reflection film
for optical information recording. That is, since the melting
temperature is low, the laser marking can be easily applied, and
since the thermal conductivity is low, it need only be sufficient
to have low laser output (with no need for excessively increasing
laser output), thereby precluding a possibility of thermal damage
otherwise occurring to disc components (a polycarbonate sheet and
an adhesion layer) due to excessive laser output. Furthermore,
since the same is excellent in corrosion resistance, it is possible
to prevent initiation of corrosion during a constant
temperature-and-moisture test conducted after the laser marking
(corrosion occurring to the aluminum-alloy reflection film, due to
moisture intruding into voids formed after the laser marking).
[0050] With the aluminum-alloy reflection film for optical
information-recording according to the invention, if Nd and/or Y
are used as the rare earth elements, the thermal conductivity can
be more significantly reduced as is evident from the item (1) as
above (a second invention).
[0051] With the aluminum-alloy reflection film for optical
information-recording according to the invention, if 1.0 to 5.0 at.
% of at least the one element selected from the group consisting of
elements Fe, and Co is further contained therein, the thermal
conductivity can be further significantly reduced as is evident
from the item (3) as above (a third invention).
[0052] With the aluminum-alloy reflection film for optical
information-recording according to the invention, if 1.0 to 10.0
at. % of at least the one element selected from the group
consisting of elements In to Li (In, Zn, Ge, Cu, and Li) is further
contained therein, the melting temperature can be reduced and the
thermal conductivity can be still further reduced as is evident
from the item (4) as above (a fourth invention).
[0053] With the aluminum-alloy reflection film for optical
information-recording according to the invention, if not more than
5.0 at. % of at least the one element selected from the group
consisting of elements Si, and Mg, the melting temperature can be
reduced as is evident from the item (5) as above (a fifth
invention). Further, among those elements (Si, Mg), Si also has the
effect of improvement in the corrosion resistance.
[0054] With the invention, the aluminum-alloy reflection film for
optical information-recording is preferably formed to a thickness
in a range of 30 to 200 nm. The reason for this is because although
it is considered that the smaller the film thickness thereof, the
easier the laser marking can be applied, if the film thickness
thereof is as small as less than 30 nm, light is transmitted
therethrough, resulting in deterioration of reflectance while
surface flatness of the film deteriorates as the film thickness
increases, thereby causing light to become prone to scattering, and
with the film thickness in excess of 200 nm, the aluminum-alloy
reflection film for optical information becomes susceptible to
scattering of light. From the viewpoint of checking the
deterioration of reflectance, and the scattering of light, the film
thickness is more preferably set to fall in a range of 40 to 100
nm.
[0055] An embodiment of an optical information-recording medium,
according to the invention, comprises the above-described
aluminum-alloy reflection film for optical information-recording
according to the invention (a sixth invention). The laser marking
can be suitably applied to the optical information-recording
medium. Accordingly, it is possible to prevent thermal damage
otherwise occurring to the disc components (the polycarbonate sheet
and the adhesion layer) due to excessive laser output. Furthermore,
since the aluminum-alloy reflection film is excellent in the
corrosion resistance, the same is insusceptible to initiation of
corrosion during the constant temperature-and-moisture test
conducted after the laser marking (corrosion otherwise occurring to
the aluminum-alloy reflection film, due to moisture intruding into
voids formed after the laser marking). In these respects, the
optical information-recording medium can have excellent
properties.
[0056] As the optical information-recording medium according to the
invention can have the excellent properties as described above, and
the same can be particularly suitably used in laser marking (a
seventh invention).
[0057] An embodiment of an aluminum-alloy sputtering target,
according to the invention, is an aluminum-alloy sputtering target
for formation of the aluminum-alloy reflection film for optical
information-recording, containing Al as the main constituent, and
1.0 to 10.0 at. % of at least the one element selected from the
group of rare earth elements while containing 0.5 to 5.0 at. % of
at least the one element selected from the group consisting of
elements Cr to Nb, Ni (Cr, Ta, Ti, Mo, V, W, Zr, Hf, Nb, and Ni)
(an eighth invention). With the use of the aluminum-alloy
sputtering target, the aluminum-alloy reflection film for optical
information-recording according to the first invention can be
formed.
[0058] If the aluminum-alloy sputtering target, according to the
invention, further contains 1.0 to 5.0 at. % of at least the one
element selected from the group consisting of elements Fe, and Co,
the aluminum-alloy reflection film for optical
information-recording according to the third invention can be
formed (a ninth invention).
[0059] If the aluminum-alloy sputtering target, according to the
invention, still further contains 1.0 to 10.0 at. % of at least the
one element selected from the group consisting of elements In to Li
(In, Zn, Ge, Cu, and Li), the aluminum-alloy reflection film for
optical information-recording according to the fourth invention can
be formed (a tenth invention).
[0060] If the aluminum-alloy sputtering target, according to the
invention, yet further contains not more than 5.0 at. % of at least
the one element selected from the group consisting of elements Si,
and Mg, the aluminum-alloy reflection film for optical
information-recording according to the fifth invention can be
formed (an eleventh invention).
WORKING EXAMPLES
[0061] Working examples, and comparative examples of the present
invention will be described hereinafter. Although the invention has
been described in terms of preferred embodiments, it will be
understood that the invention is not limited thereto, and that
various changes and modifications may be made in the invention
without departing from the spirit and scope thereof. It is
therefore intended to cover in the appended claims all such changes
and modifications as fall within the spirit and scope of
invention.
Working Example 1
[0062] An Al--Nd (an Al alloy containing Nd) thin film, and an
Al--Y (an Al alloy containing Y) thin film were fabricated, having
examined relationships of respective addition amounts (respective
contents) of Nd, Y, with the melting temperature, thermal
conductivity, reflectance of the respective thin films, and BCA
(Burst Cutting Area) marking property, respectively.
[0063] The thin films were fabricated as follows. More
specifically, the Al--Nd thin film, or the Al--Y thin film was
fabricated (formed) on a glass substrate (Corning #1737, substrate
size; 50 mm in diameter, 1 mm in thickness) by DC magnetron
sputtering. At this point in time, there were adopted film forming
conditions of substrate temperature: 22.degree. C., Ar gas
pressure: 2 mTorr, film forming rate: 2 mm/sec, and back pressure:
<5.times.10.sup.-6 Torr. For a sputtering target, use was made
of an aluminum-alloy sputtering target of the same composition as
that for the Al alloy thin film that is to be obtained.
[0064] The respective melting temperatures of the thin films were
measured in the following manner. About 5 mg of the respective
aluminum-alloy thin films (the Al--Nd thin film, and the Al--Y thin
film) formed to a thickness 1 .mu.m were collected after being
stripped from the substrate to be measured with a differential
thermometer. In this case, the mean value of temperature at the
time of the close of film melting in increasing temperature, and
temperature at the time of the start of film solidification in
decreasing temperature was taken as melting temperature. The
thermal conductivity was obtained by conversion from electrical
resistivity of the respective aluminum-alloy thin films formed to a
thickness 100 nm. The reflectance was found by measuring
reflectance of the respective films 100 nm thick at the laser wave
length 650 nm and 405 nm as currently adopted in the case of DVD.
Tests on BCA marking property were conducted using a PC
(polycarbonate) base plate 0.6 mm thick as a substrate to fabricate
an Al-alloy thin film 70 nm thick although the same film forming
conditions as those described above were adopted. At the tests, the
thin film was irradiated with laser light (laser marking) under a
laser condition of laser wavelength: 810 nm, linear velocity: 4
m/sec, and laser power: 1.5W to thereby evaluate the
characteristics on the basis of an effective aperture ratio of
portions of the thin film, subjected to the laser marking. Further,
for evaluation, use was made of a BCA code recorder POP120-8R for
DVD-ROM (manufactured by Hitachi Computer Equipment). In making
evaluation of the BCA marking property, described later, those with
the effective aperture ratio at not less than 95% is designated as
a double circle, those with the effective aperture ratio in a range
of 80 to 95% as a circle, those with the effective aperture ratio
in a range of 50 to 80% as a triangle, and those with the effective
aperture ratio less than 50% as a cross (x).
[0065] Meanwhile, as an comparative example against the
aluminum-alloy thin films described as above (the Al--Nd thin film,
and the Al--Y thin film), an aluminum-alloy thin film of a
composition equivalent to that for a JIS6061 material was
fabricated (formed) by the same method as described above. For a
sputtering target in this case, use was made of an aluminum-alloy
sputtering target fabricated out of the JIS6061 material. The
aluminum-alloy sputtering target had a composition of Si; 0.75 wt.
% (mass %), Fe: 0.10 wt. %. Cu: 0.41 wt. %, Mn: 0.07 wt. %. Mg:
1.10 wt. %, Cr: 0.12 wt. %, and the balance being composed of Al
and intrinsic impurities. An aluminum-alloy thin film as fabricated
had the same composition as that of the aluminum-alloy sputtering
target described above.
[0066] With the aluminum-alloy thin film of the composition
equivalent to that for the JIS6061 material, measurements were made
in respect of melting temperature, thermal conductivity,
reflectance, and BCA marking property, respectively, by the same
method described as above.
[0067] Results of the measurements (examinations) as described are
shown in Table 1. In the "composition" column of Table 1, an
Nd-amount, and a Y-amount of Al--Nd alloy and Al--Y alloy,
respectively, refer to values expressed in at. % (atomic %). That
is, Al-x.Nd refers to an Al alloy (Al--Nd alloy) thin film
containing x at. % of Nd while Al-x.Y refers to an Al alloy (Al--Y
alloy) thin film containing x at. % of Y. For example, Al-1.0Nd
refers to an Al alloy containing 1.0 at. % of Nd.
[0068] As is evident from Table 1, thermal conductivity
significantly deteriorates with an increase in the Nd-amount, and
the Y-amount, respectively. On the other hand, melting temperature
hardly changes even with an increase in the Nd-amount, and the
Y-amount, respectively. Further, reflectance is found gradually
deteriorating with an increase in the Nd-amount, and the Y-amount,
respectively.
[0069] Thermal conductivity is found at a sufficiently good value
(low value) when the Nd-amount, and the Y-amount are at not less
than 1.0 at. %, respectively, and is at a higher-level good value
when the Nd-amount, and the Y-amount are at not less than 2.0 at.
%, respectively. Reflectance is found at a sufficiently good value
(high value) when the Nd-amount, and the Y-amount are at not more
than 10.0 at. %, respectively, provided, however, that the
magnitude of deterioration in reflectance when the Nd-amount, and
the Y-amount exceed 7 at. %, in the described range, respectively,
is greater than that when the Nd-amount, and the Y-amount are at
not more than 7 at. %, respectively,
[0070] Based on those results, it is evident that the respective
addition amounts (contents) of Nd, and Y need to be in a range of
1.0 to 10.0 at. %, and are more preferably in a range of 2.0 to 7
at. %.
Working Example 2
[0071] An Al-4.0Nd--(Ta, Cr, Ti) thin film (a thin film made of an
Al alloy containing 4.0 at. % of Nd, together with at least one
element selected from the group consisting of elements Ta, Cr, and
Ti) was fabricated, having examined relationships of respective
addition amounts of Ta, Cr, and Ti, with the melting temperature,
thermal conductivity, reflectance, corrosion resistance of the thin
film, and BCA marking property, respectively.
[0072] The thin film was fabricated as follows. More specifically,
the Al-4.0Nd--(Ta, Cr, Ti) alloy thin film was fabricated (formed)
on a glass substrate (Corning #1737, substrate size; 50 mm in
diameter, 1 mm in thickness) by DC magnetron sputtering. At this
point in time, there were adopted film forming conditions of
substrate temperature: 22.degree. C., Ar gas pressure: 2 mTorr,
film forming rate: 2 mm/sec, and back pressure:
<5.times.10.sup.-6 Torr. For a sputtering target, use was made
of an aluminum-alloy sputtering target of the same composition as
that for the Al alloy thin film that is to be obtained.
[0073] The melting temperature of the thin film was measured in the
following manner. About 5 mg of the aluminum-alloy thin film {the
Al-4.0Nd--(Ta, Cr, Ti) alloy thin film} formed to a thickness 1
.mu.m were collected after being stripped from the substrate to be
measured with a differential thermometer. In this case, the mean
value of temperature at the time of the close of film melting in
increasing temperature, and temperature at the time of the start of
film solidification in decreasing temperature was taken as melting
temperature. The thermal conductivity thereof was obtained by
conversion from electrical resistivity of the aluminum-alloy thin
film formed to a thickness 100 nm. The reflectance was found by
measuring reflectance of the respective films 100 nm thick at the
laser wave length 650 nm and 405 nm as currently adopted in the
case of DVD. Tests on BCA marking property were conducted using a
PC (polycarbonate) base plate 0.6 mm thick as a substrate to
fabricate an Al-alloy thin film 70 nm thick although the same film
forming conditions as those described above were adopted. At the
tests, the thin film was irradiated with laser light (laser
marking) under a laser condition of laser wavelength: 810 nm,
linear velocity: 4 m/sec, and laser power: 1.5W to thereby evaluate
the characteristics on the basis of an effective aperture ratio of
portions of the thin film, subjected to the laser marking. Further,
for evaluation, use was made of a BCA code recorder POP120-8R for
DVD-ROM (manufactured by Hitachi Computer Equipment). In making
evaluation of the BCA marking property, described later, those with
the effective aperture ratio at not less than 95% is designated as
a double circle, those with the effective aperture ratio in a range
of 80 to 95% as a circle, those with the effective aperture ratio
in a range of 50 to 80% as a triangle, and those with the effective
aperture ratio less than 50% as a cross (x). As for corrosion
resistance, the aluminum-alloy thin film was immersed in a solution
of 5% NaCl at 35.degree. C. to thereby measure anodic polarization,
from which a pitting initiation potential (a potential
corresponding to current density at 10 .mu.A/cm.sup.2) was found to
be used as an index for corrosion resistance. The potential
described is a potential relative to the saturated calomel
electrode (SCE), that is, a potential vs. SCE (the same applies
hereinafter).
[0074] Results of the measurements (examinations) as described are
shown in Table 2. In the "composition" column of Table 2, an
Nd-amount, a Ta amount, a Cr amount, and a Ti amount of
Al-4Nd--(Ta, Cr, Ti) refer to values expressed in at. % (atomic %),
respectively. That is, Al-4Nd--Y.Ta (or Cr, Ti) refers to an Al
alloy {Al--Nd--(Ta, Cr, Ti) alloy} thin film containing 4.0 at. %
Nd, together with Y at. % of Ta (or Cr, Ti). For example,
Al-4Nd-1.0Ta refers to an Al alloy containing 4.0 at. % of Nd,
together with 1.0 at. % of Ta.
[0075] As is evident from Table 2, with an increase in respective
addition amounts (contents) of Ta, Cr, and Ti, the pitting
initiation potential increases (becomes more noble), resulting in
enhancement of corrosion resistance. Ta, in particular, among Ta,
Cr, and Ti, has the effect of large enhancement in corrosion
resistance. On the other hand, with an increase in the respective
addition amounts (contents) of those elements (Ta, Cr, and Ti),
melting temperature increases and reflectance deteriorates,
respectively.
[0076] Corrosion resistance is found at a sufficiently good value
(high value) when the Ta amount, Cr amount, and Ti amount are at
not less than 0.5 at. %, respectively, and is found at a
higher-level good value when those amounts are at not less than 2.0
at. %, respectively. Reflectance is found at a sufficiently good
value (high value) when the Ta amount, Cr amount, and Ti amount are
at not more than 5.0 at. %, respectively, and is at a higher-level
good value when those amounts are at not more than 4.0 at. %,
respectively. Melting temperature is found at a sufficiently good
value (low value) when the Ta amount, Cr amount, and Ti amount are
at not more than 5.0 at. %, respectively, and is at a higher-level
good value when those amounts are at not more than 4.0 at. %,
respectively.
[0077] Based on those results, it is evident that the respective
addition amounts (contents) of the Ta amount, Cr amount, and Ti
amount need to be in a range of 0.5 to 5.0 at. %, and are more
preferably in a range of 2.0 to 4.0 at. %.
[0078] Furthermore, as is evident from Tables 1 and 2, a film made
of pure aluminum is unsatisfactory because the thermal conductivity
thereof is high, and the pitting initiation potential thereof is
low (less noble). With reference to the aluminum-alloy thin film of
the composition equivalent to that for the JIS6061 material, the
pitting initiation potential thereof was found low at -744 mV
although not shown in Tables, so-that the corrosion resistance
thereof was poor
Working Example 3
[0079] An Al-4.0Nd-{Mo, V, W, Zr, Hf, Nb, and Ni (hereinafter
referred to also as (Mo to Nb, Ni)) thin film (a thin film made of
an Al alloy containing 4.0 at. % of Nd, together with at least one
element selected from the group consisting of elements Mo to Nb,
Ni) was fabricated, having examined relationships of respective
addition amounts of Mo to Nb, Ni, with the melting temperature,
thermal conductivity, reflectance, corrosion resistance of the thin
film, and BCA marking property, respectively.
[0080] The thin film was fabricated as follows. More specifically,
the Al-4.0Nd--(Mo to Nb, Ni) alloy thin film was fabricated
(formed) on a glass substrate (Corning #1737, substrate size; 50 mm
in diameter, 1 mm in thickness) by DC magnetron sputtering. At this
point in time, there were adopted film forming conditions of
substrate temperature: 22.degree. C., Ar gas pressure: 2 mTorr,
film forming rate: 2 mm/sec, and back pressure:
<5.times.10.sup.-6 Torr. For a sputtering target, use was made
of an aluminum-alloy sputtering target of the same composition as
that for the Al alloy thin film that is to be obtained.
[0081] The melting temperature of the thin film was measured in the
following manner. About 5 mg of the aluminum-alloy thin film {the
Al-4.0Nd--(Mo to Nb, Ni) alloy thin film} formed to a thickness 1
.mu.m were collected after being stripped from the substrate to be
measured with a differential thermometer. In this case, the mean
value of temperature at the time of the close of film melting in
increasing temperature, and temperature at the time of the start of
film solidification in decreasing temperature was taken as melting
temperature. The thermal conductivity thereof was obtained by
conversion from electrical resistivity of the aluminum-alloy thin
film formed to a thickness 100 nm. The reflectance was found by
measuring reflectance of the respective films 100 nm thick at the
laser wave length 650 nm and 405 nm as currently adopted in the
case of DVD. Tests on BCA marking property were conducted using a
PC (polycarbonate) base plate 0.6 mm thick as a substrate to
fabricate an Al-alloy thin film 70 nm thick although the same film
forming conditions as those described above were adopted. At the
tests, the thin film was irradiated with laser light (laser
marking) under a laser condition of laser wavelength: 810 nm,
linear velocity: 4 m/sec, and laser power: 1.5W to thereby evaluate
the characteristics on the basis of an effective aperture ratio of
portions of the thin film, subjected to the laser marking. Further,
for evaluation, use was made of a BCA code recorder POP120-8R for
DVD-ROM (manufactured by Hitachi Computer Equipment). In making
evaluation of the BCA marking property, described later, those with
the effective aperture ratio at not less than 95% is designated as
a double circle, those with the effective aperture ratio in a range
of 80 to 95% as a circle, those with the effective aperture ratio
in a range of 50 to 80% as a triangle, and those with the effective
aperture ratio less than 50% as a cross (x). As for corrosion
resistance, the aluminum-alloy thin film was immersed in a solution
of 5% NaCl at 35.degree. C. to thereby measure anodic polarization,
from which a pitting initiation potential (the potential
corresponding to current density at 10 .mu.A/cm.sup.2) was found to
be used as an index for corrosion resistance.
[0082] Results of the measurements (examinations) as described are
shown in Tables 3 and 4. In the respective "composition" columns of
Tables 3 and 4, respective amounts of Mo to Nb, Ni of Al-4Nd--(Mo
to Nb, Ni) refer to values expressed in at. % (atomic %),
respectively. That is, Al-4Nd --Y Mo (or one element selected from
the group consisting of elements V to Nb, Ni) refers to an Al alloy
{Al--Nd--(Mo to Nb, Ni) alloy} thin film containing 4.0 at. % Nd,
together with Y at. % of Mo (or the one element selected from the
group consisting of elements V to Nb, Ni). For example,
Al-4Nd-11.0Mo refers to an Al alloy containing 4.0 at. % of Nd,
together with 1.0 at. % of Mo.
[0083] As is evident from Tables 3 and 4, with an increase in an
addition amount (content) of any of Mo to Nb, Ni (Mo, V, W, Zr, Hf,
Nb, and Ni), the pitting initiation potential thereof increases
(becomes more noble), resulting in enhancement of corrosion
resistance. On the other hand, with an increase in the respective
addition amounts of those elements (Mo to Nb, Ni), melting
temperature increases, and reflectance decreases.
[0084] Corrosion resistance is found at a sufficiently good value
(high value) when the respective addition amounts (contents) of Mo
to Nb, Ni are at not less than 0.5 at. %, and is at a higher-level
good value when the respective addition amounts are at not less
than 2.0 at. %. Reflectance is found at a sufficiently good value
(high value) when the respective addition amounts of Mo to Nb, Ni
are at not more than 5.0 at. %, and is at a higher-level good value
when the respective addition amounts are at not more than 4.0 at.
%. Melting temperature is found at a sufficiently good value (low
value) when the respective addition amounts of Mo to Nb, Ni are at
not more than 5.0 at. %, respectively, and is at a higher-level
good value when the respective addition amounts are at not more
than 4.0 at. %.
[0085] Based on those results, it is evident that the respective
addition amounts (contents) of Mo to Nb, Ni need to be in a range
of 0.5 to 5.0 at. %, and are more preferably in a range of 2.0 to
4.0 at. %.
Working Example 4
[0086] An Al-4.0Nd--(Fe, Co) thin film (a thin film made of an Al
alloy containing 4.0 at. % of Nd, together with Fe or Co) and an
Al-4.0Nd-1Ta--(Fe, Co) thin film (a thin film made of an Al alloy
containing 4.0 at. % of Nd, and 1.0 at. % of Ta, together with Fe
or Co) were fabricated, having examined relationships of respective
addition amounts of Fe and Co, with the melting temperature,
thermal conductivity, reflectance, corrosion resistance, and BCA
marking property of the respective thin films, respectively.
[0087] The thin films were fabricated as follows. More
specifically, the Al-4.0Nd--(Fe, Co) alloy thin film, the
Al-4.0Nd-1Ta--(Fe, Co) alloy thin film, and so forth, were
fabricated (formed) on a glass substrate (Corning #1737, substrate
size; 50 mm in diameter, 1 mm in thickness) by DC magnetron
sputtering. At this point in time, there were adopted film forming
conditions of substrate temperature: 22.degree. C., Ar gas
pressure: 2 mTorr, film forming rate: 2 mm/sec, and back pressure:
<5.times.10.sup.-6 Torr. For a sputtering target, use was made
of an aluminum-alloy sputtering target of the same composition as
those for the Al alloy thin films that are to be obtained,
respectively.
[0088] The respective melting temperatures of the thin films were
measured in the following manner. About 5 mg of the Al-4.0Nd--(Fe,
Co) alloy thin film, the Al-4.0Nd-1Ta--(Fe, Co) alloy thin film,
and so forth, formed to a thickness 1 .mu.m, were collected after
being stripped from the substrate to be measured with a
differential thermometer. In this case, the mean value of
temperature at the time of the close of film melting in increasing
temperature, and temperature at the time of the start of film
solidification in decreasing temperature was taken as melting
temperature. The thermal conductivity thereof was obtained by
conversion from electrical resistivity of the aluminum-alloy thin
film formed to a thickness 100 nm. The reflectance was found by
measuring reflectance of the respective films 100 nm thick at the
laser wave length 650 nm and 405 nm as currently adopted in the
case of DVD. Tests on BCA marking property were conducted using a
PC (polycarbonate) base plate 0.6 mm thick as a substrate to
fabricate an Al-alloy thin film 70 nm thick although the same film
forming conditions as those described above were adopted. At the
tests, the thin film was irradiated with laser light (laser
marking) under a laser condition of laser wavelength: 810 nm,
linear velocity: 4 m/sec, and laser power: 1.5W to thereby evaluate
the characteristics on the basis of an effective aperture ratio of
portions of the thin film, subjected to the laser marking. Further,
for evaluation, use was made of a BCA code recorder POP120-8R for
DVD-ROM (manufactured by Hitachi Computer Equipment). In making
evaluation of the BCA marking property, described later, those with
the effective aperture ratio at not less than 95% is designated as
a double circle, those with the effective aperture ratio in a range
of 80 to 95% as a circle, those with the effective aperture ratio
in a range of 50 to 80% as a triangle, and those with the effective
aperture ratio less than 50% as a cross (x). As for corrosion
resistance, the respective aluminum-alloy thin films were immersed
in a solution of 5% NaCl at 35.degree. C. to thereby measure anodic
polarization, from which respective pitting initiation potentials
(the respective potentials corresponding to current density at 10
.mu.A/cm.sup.2) were found to be used as indexes for corrosion
resistance.
[0089] Results of the measurements (examinations) as described are
shown in Table 5. In the "composition" column of Table 5, an
Fe-amount, and a Co amount of Al-4.0Nd-1Ta--(Fe, Co) refer to
values expressed in at. % (atomic %), respectively. That is,
Al-4Nd--Z.Fe (or Co) refers to an Al alloy {Al--Nd--Ta--(Fe, Co)
alloy} thin film containing 4.0 at. % Nd, together with Z at. % of
Fe (or Co). For example, Al-4Nd-1Ta-3.0Fe refers to an Al alloy
containing 4.0 at. % of Nd, and 1.0 at. % of Ta, together with 3.0
at. % of Fe.
[0090] As is evident from Table 5, ether Fe or Co has the effect of
causing reduction in thermal conductivity. Neither Fe nor Co has
the effect of enhancement in corrosion resistance.
[0091] If the respective addition amounts of Fe, and Co are less
than 1.0 at. %, the effect of reduction in thermal conductivity is
small. If the respective addition amounts of Fe, and Co exceed 5.0
at. %, there is an increase in deterioration of reflectance. Based
on those results, it is evident that the respective addition
amounts of Fe and Co are preferably in a range of 1.0 to 5.0 at.
%.
Working Example 5
[0092] An Al-4.0Nd-{In--Li(In, Zn, Ge, Cu, Li)} thin film (a thin
film made of an Al alloy containing 4.0 at. % of Nd, together with
at least one element selected from the group consisting of elements
In--Li), and an Al-4.0Nd-1Ta--{In--Li(In, Zn, Ge, Cu, Li)} thin
film (a thin film made of an Al alloy containing 4.0 at. % of Nd,
and 1.0% of Ta, together with at least one element selected from
the group consisting of elements In--Li), were fabricated, having
examined relationships of respective addition amounts of In to Ni,
with the melting temperature, thermal conductivity, reflectance, of
the respective thin films, corrosion resistance, and BCA marking
property, respectively.
[0093] The thin films were fabricated as follows. More
specifically, the Al-4.0Nd--(In--Li) thin film, the
Al-4.0Nd-1Ta--(In--Li) thin film, and so forth, were fabricated
(formed) on a glass substrate (Corning #1737, substrate size; 50 mm
in diameter, 1 mm in thickness) by DC magnetron sputtering. At this
point in time, there were adopted film forming conditions of
substrate temperature: 22.degree. C., Ar gas pressure: 2 mTorr,
film forming rate: 2 mm/sec, and back pressure:
<5.times.10.sup.-6 Torr. For a sputtering target, use was made
of an aluminum-alloy sputtering target of the same composition as
those for the Al alloy thin films that are to be obtained,
respectively.
[0094] The melting temperature of the thin films was measured in
the following manner. About 5 mg of the aluminum-alloy thin films
{the Al-4.0Nd--(In--Li) thin film, the Al-4.0Nd-1Ta--(In--Li) thin
film, and so forth}, formed to a thickness 1 .mu.m, were collected
after being stripped from the substrate too be measured with a
differential thermometer. In this case, the mean value of
temperature at the time of the close of film melting in increasing
temperature, and temperature at the time of the start of film
solidification in decreasing temperature was taken as melting
temperature. The thermal conductivity thereof was obtained by
conversion from electrical resistivity of the aluminum-alloy thin
films formed to a thickness 100 nm. The reflectance was found by
measuring reflectance of the respective films 100 nm thick at the
laser wave length 650 nm and 405 nm as currently adopted in the
case of DVD. Tests on BCA marking property were conducted using a
PC (polycarbonate) base plate 0.6 mm thick as a substrate to
fabricate an Al-alloy thin film 70 nm thick although the same film
forming conditions as those described above were adopted. At the
tests, the thin film was irradiated with laser light (laser
marking) under a laser condition of laser wavelength: 810 nm,
linear velocity: 4 m/sec, and laser power: 1.5W to thereby evaluate
the characteristics on the basis of an effective aperture ratio of
portions of the thin film, subjected to the laser marking. Further,
for evaluation, use was made of a BCA code recorder POP120-8R for
DVD-ROM (manufactured by Hitachi Computer Equipment). In making
evaluation of the BCA marking property, described later, those with
the effective aperture ratio at not less than 95% is designated as
a double circle, those with the effective aperture ratio in a range
of 80 to 95% as a circle, those with the effective aperture ratio
in a range of 50 to 80% as a triangle, and those with the effective
aperture ratio less than 50% as a cross (x). As for corrosion
resistance, the aluminum-alloy thin films were immersed in a
solution of 5% NaCl at 35.degree. C. to thereby measure anodic
polarization, from which respective pitting initiation potentials
(the respective potentials corresponding to current density at 10
.mu.A/cm.sup.2) were found to be used as indexes for corrosion
resistance.
[0095] Results of the measurements (examinations) as described are
shown in Table 6. In the "composition" column of Table 6,
respective amounts of In--Li of Al-4.0Nd-1Ta--(In--Li) refer to
values expressed in at. % (atomic %), respectively. That is,
Al-4.0Nd-1Ta--Z In (or one element selected from the group
consisting of elements Zn, Ge, Cu, and Li) refers to an Al alloy
{Al--Nd--Ta--(In--Li) alloy} thin film containing 4.0 at. % of Nd,
and 1.0 at. % of Ta, together with Z at. % of In (or one element
selected from the group consisting of elements Zn, Ge, Cu, and Li).
For example, Al-4.0Nd-1Ta-3.0In refers to an Al alloy containing
4.0 at. % of Nd, and 1.0 at. % of Ta, together with 3.0 at. % of
In.
[0096] As is evident from Table 6, any of In--Li (In, Zn, Ge, Cu,
and Li) has the effect of reduction in melting temperature as well
as thermal conductivity. Among In--Li, In and Ge, in particular,
have the effect of large reduction in thermal conductivity, and
from this point of view, addition of In, Ge is preferable. In--Li
have no effect of causing enhancement in corrosion resistance.
[0097] If respective addition amounts of In--Li are less than 1.0
at. %, both the effect of reduction in thermal conductivity and the
effect of reduction in melting temperature are small. If the
respective addition amounts of In--Li exceed 10.0 at. %, this will
cause deterioration in reflectance to increase. From these point of
view, it is evident that the respective addition amounts of In--Li
are preferably in a range of 1.0 to 10.0 at. %.
Working Example 6
[0098] An Al-4.0Nd-2.0Ta--(Si, Mg) thin film (a thin film made of
an Al alloy containing 4.0 at. % of Nd, and 2.0 at. % of Ta,
together with at least one element selected from the group
consisting of elements Si, and Mg) was fabricated, having examined
relationships of respective addition amounts of Si, and Mg, with
the melting temperature, thermal conductivity, reflectance,
corrosion resistance, and BCA marking property of the thin film,
respectively.
[0099] The thin film was fabricated as follows. More specifically,
the Al-4.0Nd-2.0Ta--(Si, Mg) alloy thin film was fabricated
(formed) on a glass substrate (Corning #1737, substrate size; 50 mm
in diameter, 1 mm in thickness) by DC magnetron sputtering. At this
point in time, there were adopted film forming conditions of
substrate temperature: 22.degree. C., Ar gas pressure: 2 mTorr,
film forming rate: 2 mm/sec, and back pressure:
<5.times.10.sup.-6 Torr. For a sputtering target, use was made
of an aluminum-alloy sputtering target of the same composition as
that for the Al alloy thin film that is to be obtained.
[0100] The melting temperature of the thin film was measured in the
following manner. About 5 mg of the Al-4.0Nd-2.0Ta--(Si, Mg) alloy
thin film, formed to a thickness 1 .mu.m, was collected after being
stripped from the substrate to be measured with a differential
thermometer. In this case, the mean value of temperature at the
time of the close of film melting in increasing temperature, and
temperature at the time of the start of film solidification in
decreasing temperature was taken as melting temperature. The
thermal conductivity thereof was obtained by conversion from
electrical resistivity of the aluminum-alloy thin film formed to a
thickness 100 nm. The reflectance was found by measuring
reflectance of the respective films 100 nm thick at the laser wave
length 650 nm and 405 nm as currently adopted in the case of DVD.
Tests on BCA marking property were conducted using a PC
(polycarbonate) base plate 0.6 mm thick as a substrate to fabricate
an Al-alloy thin film 70 nm thick although the same film forming
conditions as those described above were adopted. At the tests, the
thin film was irradiated with laser light (laser marking) under a
laser condition of laser wavelength: 810 nm, linear velocity: 4
m/sec, and laser power: 1.5W to thereby evaluate the
characteristics on the basis of an effective aperture ratio of
portions of the thin film, subjected to the laser marking. Further,
for evaluation, use was made of a BCA code recorder POP120-8R for
DVD-ROM (manufactured by Hitachi Computer Equipment). In making
evaluation of the BCA marking property, described later, those with
the effective aperture ratio at not less than 95% is designated as
a double circle, those with the effective aperture ratio in a range
of 80 to 95% as a circle, those with the effective aperture ratio
in a range of 50 to 80% as a triangle, and those with the effective
aperture ratio less than 50% as a cross (x). As for corrosion
resistance, the aluminum-alloy thin film was immersed in a solution
of 5% NaCl at 35.degree. C. to thereby measure anodic polarization,
from which a pitting initiation potential (the potential
corresponding to current density at 10 .mu.A/cm.sup.2) was found to
be used as an index for corrosion resistance.
[0101] Results of the measurements (examinations) as described are
shown in Table 7. In the "composition" column of Table 7, an Nd
amount, a Ts amount, an Si amount, and an Mg amount of
Al-4.0Nd-2.0Ta--(Si, Mg) refer to values expressed in at. % (atomic
%), respectively. That is, Al-4Nd-2.0Ta--Z.Si (or Mg) refers to an
Al alloy {Al--Nd--Ta--(Si, Mg) alloy} thin film containing 4.0 at.
% of Nd, and 2.0 at. % of Ta, together with Z at. % of Si (or Mg).
For example, Al-4Nd-2.0Ta-5.0Si refers to an Al alloy containing
4.0 at. % of Nd, and 2.0 at. % of Ta, together with 5.0 at. % of
Si.
[0102] As is evident from Table 7, with an increase in respective
addition amounts of Si, and Mg, melting temperature is found
decreasing. Further, with addition (inclusion) of Si, the pitting
initiation potential is found significantly rising, resulting in
enhancement of corrosion resistance. Incidentally, in the case of
Al-2.0Si alloy (comparative example) with only Si added thereto, no
rise in the pitting initiation potential thereof is observed. Both
Si, and Mg have the effect of reduction in thermal conductivity,
but the magnitude of the effect is small.
[0103] In the case of the working examples described as above, Nd
or Y has been added as the rare earth element, however, even in the
case of adding rare earth elements other than Nd, and Y, there can
be obtained results of a tendency similar to that for the case of
the working examples described as above. Further, with the case of
the above-described working examples, any one element of the rare
earth element has been added (single addition), and further, any
one element selected from the group consisting of elements Cr to
Nb, Ni (Cr, Ta, Ti, Mo, V, W, Zr, Hf, Nb, and Ni) has been added
(single addition). However, even in the case of adding not less
than two elements selected from the group of the rare earth
elements (combined addition), and not less than two elements
selected from the group consisting of elements Cr to Nb, Ni
(combined addition), there can also be obtained results of a
tendency similar to that for the case of the working examples
described as above.
[0104] As the aluminum-alloy reflection film for optical
information-recording according to the invention has low thermal
conductivity, low melting temperature, and high corrosion
resistance, the same can be suitably used for a reflection film for
optical information-recording, requiring those properties
described, particularly for a reflection film for optical
information-recording, capable of coping with laser marking.
1TABLE 1 Melting Electrical Thermal Reflectance Reflectance BCA
temperature resistivity conductivity @650 nm @405 nm marking
Composition (.degree. C.) (.mu..OMEGA.cm) (W/m .multidot. K) (%)
(%) property JIS6061 654 8.0 0.93 89.3 88.6 X Pure Al 660 3.0 2.47
90.3 91.7 X Al--0.5Nd 655 5.5 1.35 90.2 91.5 .DELTA. Al--1.0Nd 653
7.8 0.95 89.2 90.8 .largecircle. Al--2.0Nd 652 13.0 0.57 89.2 90.2
.largecircle. Al--4.0Nd 658 21.8 0.34 88.1 88.0 .circleincircle.
Al--7.0Nd 650 37.0 0.20 84.3 82.3 .circleincircle. Al--10.0Nd 651
50.2 0.15 81.2 79.5 .circleincircle. Al--12.0Nd 662 60.1 0.12 79.5
76.9 .circleincircle. Al--0.5Y 654 4.9 1.51 90.6 91.3 .DELTA.
Al--1.0Y 661 6.5 1.14 90.1 90.7 .largecircle. Al--5.0Y 654 22.3
0.33 87.9 85.7 .circleincircle. Al--10.0Y 653 46.5 0.16 82.3 79.1
.circleincircle. Al--12.0Y 663 54.6 0.14 80.6 77.6
.circleincircle.
[0105]
2TABLE 2 Pitting Melting Electrical Thermal initiation Reflectance
Reflectance BCA temperature resistivity conductivity potential @650
nm @405 nm marking Composition (.degree. C.) (.mu..OMEGA.cm) (W/m
.multidot. K) (mV) (%) (%) property Pure Al 660 3.0 2.47 -758 90.3
91.7 X Al--4Nd 658 21.8 0.34 -766 88.1 88.0 .circleincircle.
Al--4Nd--0.5Ta 732 23.9 0.31 -612 87.2 86.8 .circleincircle.
Al--4Nd--1.0Ta 780 26.3 0.29 -588 86.7 85.2 .circleincircle.
Al--4Nd--2.0Ta 865 30.6 0.25 -555 85.2 83.6 .circleincircle.
Al--4Nd--3.0Ta 930 35.6 0.21 -483 84.0 81.4 .largecircle.
Al--4Nd--5.0Ta 982 47.2 0.16 -420 80.8 77.3 .largecircle.
Al--4Nd--7.0Ta >1000 60.3 0.12 -374 75.3 71.1 .DELTA.
Al--4Nd--0.5Ti 730 24.3 0.31 -630 87.1 86.8 .circleincircle.
Al--4Nd--1.0Ti 810 27.1 0.27 -601 85.9 85.1 .circleincircle.
Al--4Nd--2.0Ti 850 31.2 0.24 -564 85.3 84.2 .circleincircle.
Al--4Nd--5.0Ti 987 47.6 0.16 -441 80.2 78.6 .largecircle.
Al--4Nd--7.0Ti >1000 61.4 0.12 -384 74.2 71.3 .DELTA.
Al--4Nd--0.5Cr 674 22.1 0.34 -642 86.5 86.3 .circleincircle.
Al--4Nd--1.0Cr 695 26.1 0.28 -613 85.1 84.8 .circleincircle.
Al--4Nd--2.0Cr 740 30.5 0.24 -576 84.6 83.5 .circleincircle.
Al--4Nd--5.0Cr 885 46.0 0.16 -460 79.2 76.2 .largecircle.
Al--4Nd--7.0Cr 940 61.4 0.12 -402 74.0 71.2 .DELTA.
[0106]
3TABLE 3 Pitting Melting Electrical Thermal initiation Reflectance
Reflectance BCA temperature resistivity conductivity potential @650
nm @405 nm marking Composition (.degree. C.) (.mu..OMEGA.cm) (W/m
.multidot. K) (mV) (%) (%) property Pure Al 660 3.0 2.47 -758 90.3
91.7 X Al--4Nd 658 21.8 0.34 -766 88.1 88.0 .circleincircle.
Al--4Nd--0.5Zr 805 24.6 0.30 -678 85.4 85.4 .circleincircle.
Al--4Nd--1.0Zr 880 25.8 0.29 -623 83.1 83.0 .circleincircle.
Al--4Nd--2.0Zr 912 29.1 0.25 -601 81.0 80.2 .circleincircle.
Al--4Nd--3.0Zr 954 36.9 0.20 -546 78.4 76.3 .circleincircle.
Al--4Nd--5.0Zr 980 50.2 0.15 -487 76.3 73.9 .largecircle.
Al--4Nd--7.0Zr >1000 63.7 0.12 -430 70.1 64.9 X Al--4Nd--0.5Mo
683 22.6 0.33 -655 87.0 86.5 .circleincircle. Al--4Nd--1.0Mo 705
23.8 0.31 -631 85.2 84.1 .circleincircle. Al--4Nd--2.0Mo 785 26.0
0.29 -598 82.6 81.1 .circleincircle. Al--4Nd--5.0Mo 856 44.2 0.17
-480 79.9 76.7 .largecircle. Al--4Nd--0.5W 712 23.8 0.31 -690 85.1
84.9 .circleincircle. Al--4Nd--1.0W 778 27.6 0.27 -671 83.2 82.7
.circleincircle. Al--4Nd--2.0W 850 32.5 0.23 -623 81.3 80.0
.circleincircle. Al--4Nd--5.0W 960 54.3 0.14 -501 75.2 73.1
.largecircle.
[0107]
4TABLE 4 Pitting Melting Electrical Thermal initiation Reflectance
Reflectance BCA temperature resistivity conductivity potential @650
nm @405 nm marking Composition (.degree. C.) (.mu..OMEGA.cm) (W/m
.multidot. K) (mV) (%) (%) property Pure Al 660 3.0 2.47 -758 90.3
91.7 X Al--4Nd 658 21.8 0.34 -766 88.1 88.0 .circleincircle.
Al--4Nd--0.5V 709 22.8 0.33 -702 85.2 85.0 .circleincircle.
Al--4Nd--1.0V 754 25.6 0.30 -665 83.4 83.0 .circleincircle.
Al--4Nd--2.0V 843 30.4 0.24 -621 81.6 80.2 .circleincircle.
Al--4Nd--5.0V 950 47.1 0.16 -530 77.1 75.3 .largecircle.
Al--4Nd--0.5Hf 674 23.4 0.32 -634 86.3 86.3 .circleincircle.
Al--4Nd--1.0Hf 713 25.1 0.29 -587 84.7 84.2 .circleincircle.
Al--4Nd--2.0Hf 762 28.3 0.26 -567 83.9 82.0 .circleincircle.
Al--4Nd--5.0Hf 910 45.2 0.16 -501 79.0 78.2 .largecircle.
Al--4Nd--0.5Nb 703 22.5 0.33 -701 85.9 85.5 .circleincircle.
Al--4Nd--1.0Nb 742 24.3 0.30 -674 84.2 83.5 .circleincircle.
Al--4Nd--2.0Nb 830 27.6 0.27 -587 83.1 81.8 .circleincircle.
Al--4Nd--5.0Nb 930 43.1 0.17 -512 78.2 76.7 .largecircle.
Al--4Nd--0.5Ni 662 23.4 0.32 -666 87.9 87.7 .circleincircle.
Al--4Nd--1.0Ni 658 28.4 0.26 -623 86.5 86.0 .circleincircle.
Al--4Nd--2.0Ni 647 31.3 0.24 -598 85.1 83.9 .circleincircle.
Al--4Nd--5.0Ni 678 48.6 0.15 -488 80.6 78.1 .circleincircle.
[0108]
5TABLE 5 Pitting Melting Electrical Thermal Reflectance initiation
Reflectance BCA temperature resistivity conductivity @650 nm
potential @405 nm marking Composition (.degree. C.) (.mu..OMEGA.cm)
(W/m .multidot. K) (%) (mV) (%) property Al--4.0Nd 658 21.8 0.34
88.1 -766 88.0 .circleincircle. Al--4Nd--1.0Ta 780 26.3 0.29 86.7
-588 85.2 .circleincircle. Al--4Nd--2.0Ta 865 30.6 0.25 85.2 -555
83.6 .circleincircle. Al--4Nd--3.0Ta 930 35.6 0.21 84.0 -483 81.4
.circleincircle. Al--4.0Nd--1.0Fe 702 27.8 0.27 86.2 -754 85.0
.circleincircle. Al--4.0Nd--3.0Fe 803 39.8 0.19 82.3 -755 80.1
.circleincircle. Al--4.0Nd--5.0Fe 915 46.7 0.16 77.6 -746 74.3
.largecircle. Al--4.0Nd--7.0Fe >1000 60.3 0.12 62.3 -743 58.9
.DELTA. Al--4.0Nd--2.0Co 751 36.4 0.20 86.1 -748 84.6
.circleincircle. Al--4.0Nd--1Ta--1.0Fe 840 31.9 0.23 84.7 -574 81.3
.circleincircle. Al--4.0Nd--1Ta--3.0Fe 853 44.6 0.17 80.5 -589 76.9
.circleincircle. Al--4.0Nd--1Ta--5.0Fe 970 50.3 0.15 75.8 -570 71.3
.largecircle. Al--4.0Nd--1Ta--7.0Fe >1000 64.2 0.12 60.5 -532
55.7 X Al--4.0Nd--1Ta--2.0Co 890 40.2 0.19 85.5 -569 82.0
.circleincircle.
[0109]
6TABLE 6 Pitting Melting Electrical Thermal Reflectance initiation
Reflectance BCA temperature resistivity conductivity @650 nm
potential @405 nm marking Composition (.degree. C.) (.mu..OMEGA.cm)
(W/m .multidot. K) (%) (mV) (%) property Pure Al 660 3.0 2.47 90.3
-758 91.7 X Al--4Nd 658 21.8 0.34 88.1 -766 88.0 .circleincircle.
Al--4Nd--1.0Ta 780 26.3 0.29 86.7 -588 85.2 .circleincircle.
Al--4Nd--2.0Ta 865 30.6 0.25 85.2 -555 83.6 .circleincircle.
Al--4Nd--3.0Ta 930 35.6 0.21 84.0 -483 81.4 .circleincircle.
Al--4.0Nd--3.0Li 655 28.8 0.26 85.3 -787 84.8 .circleincircle.
Al--4.0Nd--3.0Ge 640 31.3 0.24 82.1 -761 80.6 .circleincircle.
Al--4.0Nd--3.0Zn 650 24.3 0.30 83.4 -756 81.1 .circleincircle.
Al--4.0Nd--3.0Cu 643 23.8 0.31 86.9 -746 84.9 .circleincircle.
Al--4.0Nd--0.5In 638 23.1 0.32 88.2 -789 86.8 .circleincircle.
Al--4.0Nd--1.0In 633 25.6 0.29 87.2 -788 86.0 .circleincircle.
Al--4.0Nd--3.0In 625 30.3 0.24 86.1 -791 85.2 .circleincircle.
Al--4.0Nd--10.0In 611 40.3 0.18 78.1 -799 76.3 .circleincircle.
Al--4Nd--3.0In--2.0Zr 911 33.6 0.22 78.9 -654 77.1 .circleincircle.
Al--4.0Nd--1Ta--3.0Li 775 33.5 0.22 83.9 -595 80.9 .circleincircle.
Al--4.0Nd--1Ta--3.0Ge 762 36.0 0.21 80.7 -587 76.8 .circleincircle.
Al--4.0Nd--1Ta--3.0Zn 778 35.1 0.21 82.1 -576 80.1 .circleincircle.
Al--4.0Nd--1Ta--3.0Cu 762 29.3 0.26 85.3 -562 83.0 .circleincircle.
Al--4.0Nd--1Ta--0.5In 744 28.1 0.27 86.9 -586 86.5 .circleincircle.
Al--4.0Nd--1Ta--1.0In 763 30.0 0.25 86.0 -574 85.2 .circleincircle.
Al--4.0Nd--1Ta--3.0In 742 35.6 0.21 84.6 -561 83.0 .circleincircle.
Al--4.0Nd--1Ta--10.0In 710 46.8 0.16 77.0 -559 72.9
.circleincircle.
[0110]
7TABLE 7 Pitting Melting Electrical Thermal initiation Reflectance
Reflectance BCA temperature resistivity conductivity potential @650
nm @405 nm marking Composition (.degree. C.) (.mu..OMEGA.cm) (W/m
.multidot. K) (mV) (%) (%) property Al--4Nd--2.0Ta 865 30.6 0.25
-555 85.2 83.6 .circleincircle. Al--4Nd--2.0Ta--0.5Si 852 30.5 0.25
-367 85.9 86.1 .circleincircle. Al--4Nd--2.0Ta--1.0Si 842 33.1 0.23
-404 85.1 85.1 .circleincircle. Al--4Nd--2.0Ta--1.5Si 828 33.8 0.22
-423 85.1 85.0 .circleincircle. Al--4Nd--2.0Ta--3.0Si 789 38.9 0.19
-430 84.3 83.9 .circleincircle. Al--4Nd--2.0Ta--5.0Si 730 44.8 0.17
-439 82.1 80.0 .circleincircle. Al--4Nd--2.0Ta--0.5Mg 855 30.3 0.24
-560 85.6 85.8 .circleincircle. Al--4Nd--2.0Ta--1.0Mg 846 31.5 0.24
-572 84.9 84.6 .circleincircle. Al--4Nd--2.0Ta--3.0Mg 836 36.8 0.20
-580 83.5 82.7 .circleincircle. Al--4Nd--2.0Ta--5.0Mg 801 42.6 0.17
-599 81.6 80.0 .circleincircle. Al--2.0Si 642 4.2 1.77 -732 90.1
91.6 X
* * * * *