U.S. patent application number 10/980680 was filed with the patent office on 2006-05-04 for reflective alloy film.
Invention is credited to Jhewn-Kuang Chen, Jye-Long Lee, Huan-Chien Tung.
Application Number | 20060093511 10/980680 |
Document ID | / |
Family ID | 36262158 |
Filed Date | 2006-05-04 |
United States Patent
Application |
20060093511 |
Kind Code |
A1 |
Chen; Jhewn-Kuang ; et
al. |
May 4, 2006 |
Reflective alloy film
Abstract
A reflective alloy film having high strength, high corrosion
resistance, and high reflectivity includes 0.01-2.0 at % of at
least one strengthening element, 0.01-2.0 at % of at least one
anti-corrosive element, 0.01-3.0 at % of at least one reflective
element, and a balance amount of silver. The total atomic
percentage of the strengthening element, the anti-corrosive
element, and the reflective element is less than 5.0. The
reflective alloy film is useful as a reflective layer or a
semi-reflective layer for various electronic devices, such as flat
panel displays and optical storage media.
Inventors: |
Chen; Jhewn-Kuang;
(Kaohsiung, TW) ; Tung; Huan-Chien; (Kaohsiung,
TW) ; Lee; Jye-Long; (Kaohsiung, TW) |
Correspondence
Address: |
CHRISTIE, PARKER & HALE, LLP
PO BOX 7068
PASADENA
CA
91109-7068
US
|
Family ID: |
36262158 |
Appl. No.: |
10/980680 |
Filed: |
November 3, 2004 |
Current U.S.
Class: |
420/502 ;
420/505; G9B/7.192 |
Current CPC
Class: |
G02B 5/0808 20130101;
C23C 14/14 20130101; G11B 7/258 20130101; C22C 5/08 20130101; G11B
7/24 20130101; C22C 5/06 20130101; G11B 7/259 20130101 |
Class at
Publication: |
420/502 ;
420/505 |
International
Class: |
C22C 5/06 20060101
C22C005/06 |
Claims
1. A reflective alloy film comprising: 0.01-2.0 at % of at least
one strengthening element; 0.01-2.0 at % of at least one
anti-corrosive element; 0.01-3.0 at % of at least one reflective
element; and a balance amount of silver, the total atomic
percentage of said strengthening element, said anti-corrosive
element, and said reflective element being less than 5.0.
2. The reflective alloy film as claimed in claim 1, wherein said
strengthening element is selected from the group consisting of
barium, scandium, silicon, titanium, indium, germanium, zinc, and
bismuth.
3. The reflective alloy film as claimed in claim 1, wherein said
anti-corrosive element is selected from the group consisting of
scandium, beryllium, aluminum, titanium, chromium, zinc, and
nickel.
4. The reflective alloy film as claimed in claim 1, wherein said
reflective element is selected from the group consisting of
palladium, copper, and platinum.
5. The reflective alloy film as claimed in claim 1, wherein said
strengthening element is germanium, said anti-corrosive element is
nickel, and said reflective element is platinum.
6. The reflective alloy film as claimed in claim 5, comprising 0.5
at % of said germanium, 0.5 at % of said nickel, and 1.0 at % of
said platinum.
7. The reflective alloy film as claimed in claim 1, wherein said
strengthening element is indium, said anti-corrosive element is
titanium, and said reflective element is copper.
8. The reflective alloy film as claimed in claim 7, comprising 0.05
at % of said indium, 0.5 at % of said titanium, and 0.5 at % of
said copper.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The invention relates to a reflective alloy film, more
particularly to a reflective alloy film having high strength, high
corrosion resistance, and high reflectivity.
[0003] 2. Description of the Related Art
[0004] A metal film has been widely applied in various electronic
products to enhance or improve original properties of a substrate
and to meet specific requirements of the products. Since silver has
high reflectivity, a film made of pure silver can meet the general
requirement of mirror-like reflection for a metal film. Therefore,
silver is a primary material used in the manufacture of a
reflective film.
[0005] In order to reduce the manufacturing cost by minimizing the
amount of silver used in the film or to provide the film with
desirable transmittance or reflectivity, the film is usually formed
on a substrate by vapor depositing silver on the substrate so as to
reduce the thickness of the silver film and thus the amount of
silver. However, the reduction in the thickness of the silver film
formed by vapor deposition decreases the strength and the corrosion
resistance of the film, which causes the film to oxidize and to
deform in an atmospheric environment, especially at an elevated
temperature or in a humid condition.
[0006] Therefore, various silver alloys, each of which contains
selective additives, have been developed to improve the properties
of the silver film.
[0007] Various silver alloys containing palladium, copper, tin,
indium, gallium, or zinc therein can enhance strength and hardness
while having a high compatibility with ceramic substrate (see, for
example, the "Noble Metal" section in "Metals Handbook" published
by American Society for Metals).
[0008] Various silver alloys with selectively added copper,
neodymium, tin, platinum, palladium, or zinc therein can achieve
corrosion resistance, and retard the undesirable oxidation. (see,
for example, Japanese Patent Nos. 2000-395894, 2002-15464 and
2003-160827, and Taiwanese Patent Nos. 514,909 and 531,562).
[0009] Various silver alloys with selectively added platinum,
palladium, copper or gold therein can minimize the reduction of
reflectivity. Since such silver alloys have a reflectivity
substantially identical to that of pure silver, they can be used in
applications such as CD-R, writable DVD disk, and the like (see,
for example, U.S. Pat. Nos. 5,948,497 and 6,007,889).
[0010] Nevertheless, in view of the development of high storage
capacity and high reading and/or writing speeds for electronic
products, it is desirable to provide the reflective film with high
strength, high corrosion resistance, and high reflectivity.
SUMMARY OF THE INVENTION
[0011] The object of the present invention is to provide a
reflective alloy film having high strength, high corrosion
resistance, and high reflectivity.
[0012] The reflective alloy film according to this invention
includes 0.01-2.0 at % of at least one strengthening element,
0.01-2.0 at % of at least one anti-corrosive element, 0.01-3.0 at %
of at least one reflective element, and a balance amount of silver.
The total atomic percentage of the strengthening element, the
anti-corrosive element, and the reflective element is less than
5.0.
[0013] The strengthening element decreases the grain size of the
alloy film so as to increase the mechanical strength of the film.
The anti-corrosive element can form a dense oxide film on the alloy
film so as to protect the alloy film from corrosion. The reflective
element enlarges area of a solid solution of the alloy film so as
to prevent formation of precipitates and to result in high
reflectivity.
BRIEF DESCRIPTION OF THE DRAWINGS
[0014] Other features and advantages of the present invention will
become apparent in the following detailed description of the
preferred embodiments with reference to the accompanying drawings,
of which:
[0015] FIG. 1 is a transmission electron microscopic photograph of
a preferred embodiment of the reflective alloy film according to
this invention illustrating a microscopic structure of the alloy
film containing 0.5 at % titanium, 0.05 at % indium and 0.5 at %
copper; and
[0016] FIG. 2 is a transmission electron microscopic photograph of
a comparative film illustrating a microscopic structure of the film
made of pure silver.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0017] The preferred embodiment of the reflective alloy film
according to this invention contains at least one strengthening
element, at least one anti-corrosive element, at least one
reflective element, and silver.
[0018] The reflectivity of the silver alloy is influenced by the
existence of a second phase element. In the present invention, at
least one of the highly reflective elements, which is selected from
the group consisting of palladium, copper and platinum, is added to
silver under the condition that reflectivity of the silver alloy
does not decrease significantly. Since the reflective element, such
as palladium, copper, or platinum, has a face-centered cubic
structure, like silver, it is compatible with silver, and thus can
enlarge the single phase area of the silver alloy phase diagram. As
a result, precipitation can be avoided, and the scattering
phenomenon and the reduction of reflectivity due to the
precipitates can be minimized. As shown in Table 1, although the
addition of the reflective element reduces the reflectivity of
silver, the reflectivity reduction is not significant. Preferably,
the amount of the reflective element ranges from 0.01 at % to 3.0
at %. If the amount of the reflective element is above 3.0 at %,
the reflectivity of the alloy film will decrease significantly as
the amount of the reflective element is increased. TABLE-US-00001
TABLE 1 Reflectivity 200 nm thickness, reflectivity(%) Composition
of film at 650 nm wavelength Ag 98 Ag--2.0at % Pd 98 Ag--2.0at % Cu
97 Ag--2.0at % Pt 96
[0019] The anti-corrosive element can form a dense oxide film on
the alloy film so as to enhance the corrosion resistance of the
alloy film. As shown in Table 2, the anti-corrosive element is
preferably scandium, beryllium, aluminum, titanium, chromium, zinc,
nickel, or mixtures thereof. Since the anti-corrosive element has a
high reactivity with oxygen, the anti-corrosive element added to
the alloy film will migrate to the surface of the alloy film so as
to form a dense anti-corrosive oxide film thereon. Preferably, the
amount of the anti-corrosive element ranges from 0.01 at % to 2.0
at %. If the amount of the anti-corrosive element is above 2.0 at
%, the reflectivity of the alloy film may be adversely affected
thereby. TABLE-US-00002 TABLE 2 Anti-corrosive element
Anti-corrosive Oxidation free energy (kJ/mole element oxygen) at
127.degree. C. Scandium(Sc) -596 Beryllium(Be) -570 Aluminum(Al)
-511 Titanium(Ti) -468 Chromium(Cr) -342 Zinc(Zn) -310 Nickel(Ni)
-202
[0020] In order to strengthen the film and to maintain a single
phase microstructure of the silver alloy, the principle of solid
solution strengthening mechanism is applied in the present
invention. As shown in Table 3, the strengthening element is
selected from barium, scandium, silicon, titanium, indium,
germanium, zinc, bismuth, and mixtures thereof. The atomic radiuses
of these strengthening elements all have 5% or higher difference
from the atomic radius of pure silver. The dislocation migration in
the atomic lattice of these alloys is reduced by elastic strain of
the atomic lattice. Therefore, the grain size is reduced, and the
strength of the alloy film is increased. Preferably, the amount of
the strengthening element is controlled to be in a range from 0.01
at % to 2.0 at %. TABLE-US-00003 TABLE 3 Strengthening element
Radius difference as compared to silver Barium(Ba) 59% Scandium(Sc)
19% Silicon(Si) 17% Titanium(Ti) 14% Indium(In) 14% Germanium(Ge)
13% Zinc(Zn) 13% Bismuth(Bi) 7%
[0021] In Table 4, examples of this invention and comparative
examples are compared in terms of reflectivity, relative mechanical
strength, and relative corrosion resistance. The comparative
examples include a film of pure silver, a silver alloy film
containing 2 at % copper, a silver alloy film containing 2 at %
platinum, and a silver alloy film containing 1 at % neodymium. The
examples of this invention include a silver alloy film containing
0.5 at % germanium, 0.5 at % nickel, and 1.0 at % platinum
(referred as Example 1 hereinafter), and a silver alloy film
containing 0.5 at % titanium, 0.05 at % indium, and 0.5 at % copper
(referred as Example 2 hereinafter).
[0022] The relative mechanical strength is determined on a basis of
grain size of a sputtered film. Since the mechanical strength is
inversely proportional to the square root of the grain size, the
smaller the grain size, the higher will be the relative mechanical
strength. Four numbers from 1 to 4 are used to evaluate the
mechanical strength. The smaller the number, the lower is the
relative mechanical strength.
[0023] The relative corrosion resistance is determined on a basis
of the duration of delaying an abrupt reduction of the reflectivity
at constant temperature under constant relative humidity. The
longer the duration, the better is the corrosion resistance. The
relative corrosion resistance is evaluated using numbers from 1 to
4. The smaller the number, the worse is the corrosion resistance.
TABLE-US-00004 TABLE 4 comparison of properties between the
examples of this invention and the comparative examples Relative
Relative Reflectivity mechanical corrosion Composition at 650 nm
strength resistance Comparative Ag 98% 1 1 Ag--2at%Cu 97% 2 2
Ag--2at%Pt 96% 3 4 Ag--1at%Nd 90% 4 3 Examples Example 1 96% 3.5 4
(Ag--0.5at% Ge--0.5at%Ni-- 1.0at%Pt) Example 2 97% 3 3.5
(Ag--0.5at% Ti--0.05at%In-- 0.5at%Cu)
[0024] As shown in Table 4, generally, Examples 1 and 2 have
significantly improved properties in connection with mechanical
strength and corrosion resistance while attaining a reflectivity
above 95%.
[0025] The alloy film of Example 1 has a reflectivity of 96%, which
is comparable to that of the comparative alloy film containing 2 at
% platinum. However, the addition of germanium (used as the
strengthening element) and nickel (used as the anti-corrosive
element) improves the mechanical strength and the corrosion
resistance of the alloy film of Example 1 over the comparative
example. Furthermore, the alloy film of Example 1 has a
reflectivity superior to that of the comparative example containing
2 at % neodymium.
[0026] The alloy film of Example 2 has a reflectivity of 97%, and
has the mechanical strength and the corrosion resistance superior
to those of the comparative alloy film containing 2 at % copper,
which has a reflectivity identical to that of Example 2.
[0027] In view of the results shown in Table 4, the alloy film of
this invention possesses high strength, high corrosion resistance,
and high reflectivity. Therefore, the alloy film of this invention
is useful as a reflective film for various electronic products,
such as flat panel displays and optical storage media.
[0028] FIGS. 1 and 2 show transmission electron microscopic
photographs of the alloy film of Example 2 and the comparative film
made of pure silver. The alloy film of Example 2 has a grain size
less than 10 nm, and the grains thereof are distributed densely.
Therefore, as compared to the silver film shown in FIG. 2, which
has a grain size of about 100 nm, the grain size of the alloy film
of Example 2 is reduced significantly, which in turn demonstrates
that the mechanical strength of the alloy film of Example 2 is
superior to that of the comparative silver film. It was further
confirmed by electron diffraction pattern that the atomic structure
of the alloy film of Example 2 is a single phase face-centered
cubic structure.
[0029] In fact, when the alloy film of this invention is made in a
thickness of 100 nm, it not only has a reflectivity of 97% at a
wavelength of 650 nm, which is comparable to that of silver film
(98%), but also passed a corrosion resistance test at a temperature
of 80.degree. C. in a relative humidity of 85% (The duration till
the reduction in the reflectivity is over 100 hrs). Therefore, the
alloy film can be used as a full-reflective layer of a high-speed
write-once DVD disk.
[0030] When the alloy film of this invention is made in a thickness
less than 20 nm, it still has a reflectivity above 25%, while
passing the corrosion resistance test at a temperature of
80.degree. C. in a relative humidity of 85% (The duration till the
reduction in the reflectivity is longer than 96 hrs). Therefore,
the alloy film can be used as a semi-reflective layer of a
double-layer read-only recording medium or a double-layer
write-once recording medium, or as a reflective layer of a
reflective/semi-reflective flat panel display.
[0031] While the present invention has been described in connection
with what is considered the most practical and preferred
embodiments, it is understood that this invention is not limited to
the disclosed embodiments but is intended to cover various
arrangements included within the spirit and scope of the broadest
interpretation so as to encompass all such modifications and
equivalent arrangements.
* * * * *