Optical: systems and elements – Optical modulator – Light wave temporal modulation
Reexamination Certificate
2003-03-07
2004-06-22
Schwartz, Jordan M. (Department: 2873)
Optical: systems and elements
Optical modulator
Light wave temporal modulation
C359S265000, C359S267000
Reexamination Certificate
active
06753995
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to an electrochromic mirror, and more particular to an electrochromic mirror having an alternative color and desired electrochromic property by incorporating therein a specific reflective layer. The present invention further relates to a reflective layer imparting an alternative color and desired electrochromic property to an electrochromic mirror.
BACKGROUND OF THE INVENTION
Glare is one of the troublesome factors when driving a vehicle. Many efforts have been made to solve the glaring problem. One of the most effective ways is to provide an electrochromic unit for the rearview mirror of the vehicle. The electrochromic unit deepens the color and thus reduces the reflectance of the mirror according to the degree of the glare, thereby minimizing the glaring effect.
FIG. 1
is a schematic diagram showing a conventional electrochromic unit for use in a rearview mirror assembly of a vehicle to achieve the reflectance-adjustment purpose by changing the color of the rearview mirror.
The electrochromic unit includes two glass substrates
11
and
12
positioned parallel to each other, and spaced apart by a distance of a micrometer-to-millimeter order. On each of the inner faces of the glass substrates, a transparent indium-tin-oxide (ITO) coating
13
,
14
is provided as an electrode for electric conduction. The space
15
between the two glass substrates
11
and
12
is filled with an electrochromic solution and sealed with a material
16
inert to the electrochromic solution, e.g. epoxy. Furthermore, a reflective layer
17
is coated on the other side of the glass substrate
14
opposite to the glass substrate
12
for providing proper mirror reflectance. By applying a voltage across the ITO cathode and anode
13
and
14
, the color of the electrochromic solution will change accordingly. With the increase of the glare light intensity, the voltage applied to the electrochromic unit increases, and the color of the mirror becomes darker.
In general, the electrochromic solution includes an anodic compound which undergoes a reversible color change when its valence state is altered due to oxidation, a cathodic compound which undergoes a reversible color change when its valence state is altered due to reduction, and a solvent which solubilizes the anodic and cathodic compounds but keeps chemically inert to the other constituents of the electrochromic solution. The electrochromic solution may optionally further includes an electrolyte material for enhancing the conductivity of the electrochromic solution. Please refer to U.S. Pat. Nos. 4,902,108, 5,679,283, 5,611,966, 5,239,405, 5,500,760 and 6,211,994B1 which are incorporated herein for reference, to realize examples of the anodic compound, cathodic compound, solvent and electrolyte material contained in conventional electrochromic solutions.
In the prior art, the reflective layer
17
is generally made of aluminum. Due to poor adhesion between glass and aluminum, the reflective layer
17
is readily stripped off the glass substrate
12
so as to reduce lifetime of the rearview mirror assembly.
FIG. 2
is a schematic diagram showing another conventional electrochromic unit for use in a rearview mirror assembly of a vehicle to achieve the color-change purpose. The electrochromic unit of
FIG. 2
includes two glass substrates
21
and
22
positioned parallel to each other, and spaced apart by a distance of a micrometer-to-millimeter order. On each of the inner faces of the glass substrates, an electrically conductive electrode
23
,
24
is provided. The space
25
between the two glass substrates
21
and
22
is filled with an electrochromic solution and sealed with a material
26
inert to the electrochromic solution, e.g. epoxy. Depending on the required level of electric conduction, the electrode
23
is made of a transparent material such as indium-tin-oxide (ITO) or a transparent composite material such as ITO/metaL/ITO. The electrode
24
could also act as a reflective layer by utilizing a metallic material having both the high reflectivity and the high electrical conductivity. Thus, the process for fabricating the electrochromic unit can be exempted from making the reflective layer
17
in FIG.
1
. The metallic material used in the electrode
24
is usually silver (Ag) or silver alloy such as silver-gold (Ag/Au) alloy, silver-platinum (Ag/Pt) alloy, silver-palladium (Ag/Pd) alloy and the like. However, since the electrode
24
is arranged between the glass substrate
22
and electrochromic solution
25
and in contact with the seal
26
, the fabrication of the electrode
24
in view of the corrosion and the electrical property change problems are critical. For example, a base layer
27
between the electrode
24
and the glass substrate
22
is required for the purpose of attaching the electrode
24
onto the glass substrate
22
. Furthermore, in order to prevent the electrode
24
from being corroded by the electrochromic solution
25
, a protective layer
28
is further provided between the electrode
24
and the electrochromic solution
25
with a proviso that the electrical property of the electrode
24
is not impaired. Although the electrode
24
provides both the high reflectivity and the high electrical conductivity, the process for fabricating such electrochromic unit of
FIG. 2
involves complicated steps and high producing cost.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a reflective layer which provides suitable reflectance for the mirror and excellent adhesion to the glass substrate of an electrochromic mirror assembly.
It is another object of the present invention to provide an electrochromic mirror which is easily produced and has an alternative color in response to the glare, compared to the conventional ones.
In accordance with an aspect of the present invention, there is provided an electrochromic mirror for performing color change in response to a voltage applied thereto. The electrochromic mirror comprises a first substrate, a second substrate, a first and a second electrodes, an electrochromic composition and a reflective layer. The first substrate being light transmissible. The second substrate is positioned substantially parallel to the first substrate, and spaced apart from the first substrate by a predetermined clearance to form a space therebetween. The first and the second electrodes are provided on opposite surfaces of the first and second substrates facing the space, respectively, for providing a voltage, the first electrode being light transmissible. The electrochromic composition is disposed in the space between the first and second substrates for performing color change in response to the voltage. The reflective layer is made of aluminum-titanium (Al/Ti) alloy and disposed on the second substrate for partially reflecting the light entering from the first substrate back to the first substrate.
In an embodiment, the first and second substrates are made of glass.
In an embodiment, the first and the second electrodes are made of indium tin oxide (ITO).
In an embodiment, the reflective layer is disposed on the second substrate opposite to the second electrode. Furthermore, the electrochromic mirror comprises an intermediate layer between the second substrate and the reflective layer for cooperating with the reflective layer to provide different color from that resulting from only the reflective layer.
In an embodiment, the intermediate layer is made of indium tin oxide (ITO).
In an embodiment, the reflective layer is disposed between the second substrate and the second electrode.
In accordance with another aspect of the present invention, there is provide an electrochromic mirror for performing color change in response to a voltage applied thereto. The electrochromic mirror comprises a first substrate, a second substrate, a first and a second electrodes, an electrochromic composition and a composite reflective layer. The first substrate is light transmissible. The second substrate is positioned substantially para
Exon Science Inc.
Madson & Metcalf
Schwartz Jordan M.
Stultz Jessica
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