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BACKGROUND OF THE INVENTION
(i) Field of the Invention
The present invention relates to a transparent panel heater which can be
used as a portion of a window. More particularly, it relates to a
transparent panel heater which can be used in liquid crystal displays,
refrigerator showcases, freezer showcases, defrosters for windshields of
cars and the like, and a transparent laminate for use in the transparent
panel heater.
(ii) Description of the Related Art
In a freezer showcase or a refrigerator showcase, it has been necessary to
prevent dew from condensing on the surface of a glass plate constituting
its window. Therefore, a transparent conductive film has been formed on
the glass surface, and predetermined electric power has been applied to
the transparent conductive film to heat the glass surface.
In recent years, the demand for liquid crystal displays has increased, but
when they are used in a cold environment, their operation is
inconveniently slow. Thus, also in liquid crystal displays, the necessity
of providing transparent panel heaters for temperature control has
increased.
Conventionally, in a liquid crystal display which can be used under such
conditions as in a cold environment, a mesh-like heating resistor has been
disposed to heat it, as suggested in, for example, Japanese Patent
Application Laid-open No. 126517/1983. In this constitution, however, it
is difficult to uniformly heat the whole liquid crystal display, and the
heating resistor comprising an opaque metal tends to inconveniently
disturb an operator in watching the display.
A transparent heating element in which a transparent conductive film is
formed on a transparent substrate has been suggested in, for example, U.S.
Pat. No. 4,952,783. One exemplary constitution of such a heating element
is shown in FIG. 1 attached hereto. That is, a transparent conductive film
52 is formed all over the surface of a transparent substrate 51, and a
pair of electrodes 53 for feeding electric power to the transparent
conductive film 52 are arranged at both the ends of the transparent
conductive film 52. Furthermore, in order to protect the transparent
conductive film 52 and the electrodes 53, a transparent protective layer
54 is formed all over the surface of the heating element. Here, the
electrodes 53 are formed by applying a conductive printing material such
as a silver paste on suitable positions of the transparent conductive film
52 by a screen printing method or the like, and then thermally treating
the applied coating material. For the purpose of improving the reliability
of the electrodes, Japanese Patent Application Laid-open No. 289685/1992
discloses electrodes constituted by sandwiching a metal foil with
electrically conductive printing material layers.
In this kind of transparent panel heater, however, if the electrodes are
constituted by an electrically conductive printing material such as the
silver paste, the resistance of the conductive printing material itself is
larger as compared with that of the transparent conductive film, and the
contact resistance between the electrodes and the transparent conductive
film tends to increase. If the contact resistance increases, a conduction
state in the transparent conductive film is uneven with the enlargement of
the transparent panel heater. As a result, heat is unevenly generated, and
the transparent panel heater is not uniformly heated on the whole. In
addition, current is concentrated in the vicinity of the contacts of the
electrodes, so that portions of the transparent panel heater in the
vicinity of the electrodes are abnormally heated and a problem such as
disconnection tends to inconveniently occur. In the case of such
electrodes as disclosed in the above-mentioned Japanese Patent Application
Laid-open No. 289685/1992, the unevenness of the conduction state can be
solved, but adhesive properties between the transparent conductive film
and the electrodes are poor and both of them are liable to peel from each
other during use. In addition, a manufacturing process for the formation
of such electrodes is intricate and their workability is low, which
increases the cost of products.
The present inventors have disclosed, in U.S. patent application Ser. No.
08/099,445 (European Patent Application No. 93306118.6, European
Publication No. 0582457), that a transparent panel heater can be provided
by forming a substantially light-transmittable metallic thin film on a
transparent conductive film, and then forming metallic electrodes on the
metallic thin film by a wet process. This invention is an effective
invention which can provide a transparent panel heater, but in a treatment
for the formation of the metallic electrodes of the transparent panel
heater by the wet process, skill has been required.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a transparent panel heater
which has electrodes that do not use any conductive printing material and
which permits an improved process for forming the electrodes on a
transparent conductive film and preventing damage to the transparent
conductive film in forming metallic electrodes even in a wet process and
which can be manufactured with a high productivity.
Another object of the present invention is to provide a method for
manufacturing a transparent panel heater in which electrodes can be formed
without using any conductive printing material and in which productivity
can be improved.
Still another object of the present invention is to provide a transparent
laminate for use in the transparent panel heater.
The above-mentioned objects of the present invention can be achieved by a
transparent panel heater having a transparent conductive film which is
formed on a transparent substrate and which can be used as a heating
surface, and a pair of metallic electrodes for electrifying the
transparent conductive film; said transparent panel heater comprising: an
acid-resistant transparent protective film formed on the transparent
conductive film and a substantially light transmittable metallic
electrode-underlying-layer formed on the transparent protective film, said
metallic electrodes being formed on the electrode-underlying-layer.
The object of the present invention can be also achieved by a transparent
panel heater having a transparent conductive film which is formed on a
transparent substrate and which can be used as a heating surface, and a
pair of metallic electrodes for electrifying the transparent conductive
film; said transparent panel heater comprising: a substantially
light-transmittable metallic electrode-underlying-layer formed on the
transparent conductive film, said transparent conductive film being a
laminate of at least one transparent thin layer made of a nitride and/or a
carbide and at least one substantially light-transmittable metallic layer,
said metallic electrodes being formed on the electrode-underlying-layer.
Another object of the present invention can be achieved by a method for
manufacturing a transparent panel heater having a transparent conductive
film which is formed on a transparent substrate and which can be used as a
heating surface, and a pair of metallic electrodes for electrifying the
transparent conductive film; said method for manufacturing the transparent
panel heater comprising: a first step of forming, by a dry process, an
acid-resistant transparent protective film which is insoluble in an acidic
solution having a pH of 5 or less, preferably a pH of 3 or less, more
preferably a pH of 1 or less, on the transparent conductive film formed on
the transparent substrate; a second step of depositing a metal or an alloy
on the transparent conductive film by the dry process to form a
substantially light-transmittable electrode-underlying-layer thereon; a
third step of forming a first transparent resin protective layer on an
area other than a place where the metallic electrodes are formed; and a
fourth step of forming the metallic electrodes on the
electrode-underlying-layer by a wet plating process.
The other object of a present invention can be also achieved by a method
for manufacturing a transparent panel heater having a transparent
conductive film which is formed on a transparent substrate and which can
be used as a heating surface, and a pair of metallic electrodes for
electrifying the transparent conductive film; said method for
manufacturing the transparent panel heater comprising: a first step of
forming, on the transparent substrate by a dry process, the transparent
conductive film comprising a laminate of at least one transparent thin
layer made of a nitride and/or a carbide, and at least one substantially
light-transmittable metallic layer; a second step of depositing a metal or
an alloy on the transparent conductive film by the dry process to form a
substantially light-transmittable electrode-underlying-layer thereon; a
third step of forming a first transparent resin protective layer eon an
area other than a place where the metallic electrodes are formed; and a
fourth step of forming the metallic electrodes on the
electrode-underlying-layer by a wet plating process.
Other objects of the present invention can be achieved by a transparent
laminate obtained by laminating a transparent thin layer made of a nitride
and/or a carbide and a substantially light-transmittable metallic layer on
at least one side of a transparent substrate.
In the transparent panel heater of the present invention, the
electrode-underlying-layer and the acid-resistant transparent protective
film are usually formed by a dry process, and the metallic electrodes are
usually formed by a wet process. In the present invention, the dry process
means a process for forming a film in a solution-free atmosphere, and
examples of the dry process include physical deposition methods such as a
vacuum vapor deposition method, an ion plating method, a sputtering method
and a molecular beam epitaxy (MBE) as well as chemical deposition methods
such as a CVD method, an MOCVD method and a plasma CVD method.
Furthermore, the wet process means a process for forming a film in a
solution, and particularly, it denotes electroplating or electroless
plating (chemical plating) which is wet plating.
As the transparent substrate which can be used in the present invention,
there can be used a glass or a transparent plastic film having a light
transmission of 70% or more, preferably 80% or more in a visible light
range having a wavelength of from 400 nm to 800 nm. From the viewpoints of
thinness, flexibility, impact resistance and continuous productivity, the
plastic film can be preferably used as the transparent substrate.
Preferable examples of a plastic material of the film constituting the
transparent substrate include polyesters such as polyethylene
terephthalate (PET) and polyethylene naphthalate (PEN), polyamide,
polyether, polysulfone, polyethersulfone (PES), polycarbonate,
polyarylate, polyether imide, polyether ether ketone (PEEK), polyimide and
aramid.
The thickness of the plastic film which can be used as the transparent
substrate is usually in the range of from 5 .mu.m to 500 .mu.m, preferably
from 10 .mu.m to 200 .mu.m, more preferably from 50 .mu.m to 150 .mu.m.
As the transparent conductive film which can be used in the present
invention, there can be used (1) a compound semiconductor layer of tin
oxide, indium oxide or the like, (2) a metallic layer comprising a simple
substance of gold, silver, copper, palladium or the like, or an alloy
thereof, and (3) a laminate of a sandwiched structure of a metallic layer
comprising a metal such as gold, silver, copper, palladium or the like, or
an alloy thereof and a thin film having a high refractive index with a
refractive index of 01.8 or more, preferably 2.0 or more, of indium oxide,
titanium oxide or the like. The thickness of each of these layers is
basically in the range of from 1 nm to 500 nm, preferably from 5 nm to 50
nm, more preferably from 10 nm to 30 nm. Particularly in the case of the
laminate structure, the thickness of the metallic layer is in the range of
from 1 nm to 100 nm, preferably from 5 nm to 50 nm, more preferably 10 nm
to 30 nm. From the viewpoints of transparency and conductivity, the
laminate structure (3) is desirable. Here, as the metallic layer, a thin
film mainly comprising silver is preferable, silver only is more
preferable and also in the case of silver alloy, and the content of silver
is 30% by weight or more, preferably 40% by weight or more, more
preferably 50% by weight or more. Needless to say, even the metallic layer
in which the silver content falls off from the above-mentioned range is
also usable in a certain case. In addition, the metallic layer may be
formed of a laminate of the thin layer mainly comprising silver and a thin
layer comprising another metal.
As an example of the laminate which is preferable from the viewpoint of
acid resistance at the time of plating, there is a laminate in which the
metallic layer, particularly the silver thin layer is sandwiched between
transparent thin layers made of a nitride and/or a carbide. When the
transparent thin layer is made of the nitride and/or the carbide having
acid resistance, it can be omitted to form the acid-resistant transparent
protective film on the transparent conductive film. In this case, in order
to prevent the transparent conductive film from deteriorating owing to
electrification, it is preferable to add a metal such as gold, copper
palladium platinum or tungsten to the silver thin film, so long as
conductivity and transparency are not impaired. In addition, a thin film
of a metal other than silver may be laminated on the silver thin layer.
The plural transparent thin layers and metallic layers can be alternately
mutually laminated. The transparent thin layers made of the nitride and/or
the carbide may be partially oxidized or hydrogenated, so long as
transparency and acid resistance are not impaired. If neither the nitride
nor the carbide is used in the transparent conductive film, the
acid-resistant transparent protective film should be interposed between
the transparent conductive film and the electrode-underlying-layer which
is an underlying layer for the metallic electrodes.
The above-mentioned transparent thin layer will be further described in
more detail. As this transparent thin layer, any layer is acceptable, so
long as it is a protective layer capable of withstanding a solution having
a pH of 5 or less, preferably a pH of 3 or less, more preferably a pH of 1
or less which is used at the time of a plating treatment. Examples of the
transparent thin layer include layers made of aluminum nitride, indium
nitride, gallium nitride, silicon nitride, tin nitride, boron nitride,
silicon carbide, amorphous carbon, diamond-like carbon, tin oxide,
titanium oxide, and aluminum oxide and the transparent thin film having a
high refractive index with a refractive index of 1.8 or more, preferably
2.0 or more which comprises the nitride and/or the carbide is preferable.
In this case, the transparent thin film may be partially oxidized or
hydrogenated.
Examples of the partially oxidized transparent thin layer include aluminum
oxynitride, indium oxynitride, gallium oxynitride, silicon oxynitride, tin
oxynitride, boron oxynitride and silicon oxynitride carbide. In each of
these oxynitrides, the content of nitrogen in the components except the
metal and carbon is preferably 30 atom % or more, more preferably 50 atom
% or more.
Examples of the partially hydrogenated transparent thin layer include
aluminum hydride nitride, indium hydride nitride, gallium hydride nitride,
silicon hydride nitride, tin hydride nitride, boron hydride nitride and
silicon hydride nitride carbide. In each of these hydride nitrides, the
content of nitrogen in the components except the metal and carbon is
preferably 50 atom % or more, more preferably 80 atom % or more.
In the present invention, the thickness of the transparent thin layer is
usually in the range of from 1 nm to 100 nm, preferably from 5 nm to 50
nm, more preferably from 10 nm to 30 nm.
As a technique for forming the transparent conductive film on the
transparent substrate, there can be utilized a known method such as a
spray method, a coating method or a physical deposition method. Here, the
physical deposition method is a technique for forming a thin film of a
metal or the like under reduced pressure or under vacuum, and examples of
the physical deposition method include a vacuum deposition method, a
sputtering method, an ion plating method, an ion beam assisting deposition
method and an ion cluster beam method. In the case that the transparent
conductive film comprises the laminate, it is preferable to use a
formation method using ions or a plasma such as the sputtering method, the
ion plating method, the ion beam assisting deposition method and the ion
cluster beam method.
As materials for the electrode-underlying-layer which can be used in the
present invention, there can be used a metal such as copper, nickel,
palladium, chromium, gold, silver, lead or platinum or an alloy thereof.
The electrode-underlying-layer is formed on the transparent conductive film
or the acid-resistant transparent protective film by a selected dry
process in which deposited particles directly or indirectly get energy
from an electromagnetic field. Here, directly getting the energy means
that ions are accelerated by power in the electromagnetic field to get the
energy. Indirectly getting the energy means that the ions get the energy
via a collision step from particles which have directly received the
energy. The energy which the deposited particles get in the
above-mentioned process is preferably in the range of from 0.5 eV to 100
eV, more preferably from 1 eV to 50 eV. If the energy which the deposited
particles get is less than 0.5 eV, the adhesive force of the
electrode-underlying-layer is not sufficient in many cases, and if it is
more than 100 eV, the thin film is excessively sputtered with the
deposited particles. In this connection, the particles not having the
energy in the above-mentioned range may be present as much as several
percent to several tens percent in the deposited particles for forming the
electrode-underlying-layer. Typical examples of a technique for forming
the electrode-underlying-layer include a vacuum vapor deposition method, a
sputtering method, an ion plating method, an ion beam assisting deposition
method, an ion cluster beam method and an ion deposition thin film
formation method.
The electrode-underlying-layer is suitably formed in the state of a uniform
continuous layer on the transparent conductive film or the acid-resistant
transparent protective film, but it may be formed in the form of an island
on the transparent conductive film, or locally on the transparent
conductive film or the acid-resistant transparent protective film.
The thickness of the electrode-underlying-layer is preferably in the range
of from 0.5 nm to 20 nm. If the thickness is less than 0.5 nm, the
thickness of the electrodes formed by a plating treatment is apt to be
nonuniform. If it is more than 20 nm, visible light transmission
noticeably deteriorates, so that the light transmission of the transparent
panel heater is impaired, which is unsuitable for the objects of the
present invention.
In the transparent panel heater of the present invention, when the
acid-resistant transparent protective film is interposed between the
transparent conductive film and the electrode-underlying-layer, this
acid-resistant transparent protective film should have a light
transmission of 60% or more, preferably 70% or more, more preferably 80%
or more at a wavelength of 550 nm and withstand a solution having a pH of
5 or less, preferably a pH of 3 or less, more preferably a pH of 1 or less
which is used at the time of the plating treatment. Examples of the
material for such a transparent protective film include aluminum nitride,
indium nitride, gallium nitride, silicon nitride, tin nitride, boron
nitride, silicon carbide, amorphous carbon, diamond carbon, tin oxide,
titanium oxide and aluminum oxide, and the transparent thin film having a
high refractive index with a refractive index of 1.8 or more, preferably
2.0 or more which comprises the nitride and/or the carbide is preferable.
In the present invention, the thickness of the acid-resistant transparent
protective film is in the range of from 1 nm to 100 nm, preferably from 5
nm to 50 nm, more preferably from 10 nm to 30 nm.
In the transparent panel heater of the present invention, when a laminate
of at least one transparent thin film made of the nitride and/or the
carbide and at least one metallic layer is used as the transparent
conductive film, an intermediate layer can be interposed between the
transparent conductive film and the electrode-underlying-layer for the
purpose of further improving the adhesive properties of the transparent
conductive film to the metallic electrodes formed by the wet process.
Preferable examples of a material for the intermediate layer of the
present invention include metal oxides such as zinc oxide, tin oxide,
aluminum oxide, indium oxide and indium tin oxide (ITO). The thickness of
the intermediate layer is usually from 1 nm to 100 nm, preferably 5 nm to
50 nm, more preferably from 10 nm to 20 nm.
In the present invention, as the first transparent resin protective layer,
any protective layer is acceptable, so long as it has a light transmission
of 70% or more, preferably 80% or more at a wavelength of 550 nm and it
withstands the plating treatment. Examples of such a first transparent
resin protective layer include layers obtained by applying and then curing
an ultra-violet setting resin, an electron beam-setting resin, a
thermosetting resin, and a known UV-setting resist ink, an electron
beam-setting resist ink and a thermosetting resist ink, and a dry film. In
addition, other materials can also be used as the first transparent resin
protective layer, if they can provide the water-resistant and
chemical-resistant transparent films. For example, a transparent coating
material, a curable monomer or oligomer, a plastic film such as a
polyester onto which an adhesive is applied, or a self-adhesive film of an
ethylene-vinyl acetate copolymer or the like can also be laminated to form
the first transparent resin protective layer. The above mentioned resin or
film can be also used in combination thereof or mixture thereof as the
first transparent resin protective layer. The thickness of the first
transparent resin protective layer is usually in the range of from 1 .mu.m
to 100 .mu.m, preferably from 5 .mu.m to 50 .mu.m, more preferably from 10
.mu.m to 30 .mu.m.
As a material for the metallic electrodes which can be used in the present
invention, any metal can be used, so long as it can be deposited by the
plating. Nevertheless, from the viewpoints of electrical properties and
durability, the electrodes preferably comprise a single layer or a
laminate of at least one metal selected from the group consisting of
copper, silver, gold, nickel, chromium, tin, lead and solder, or an alloy
of these metals. The thickness of the electrodes should be such as to
permit the flow of current under which the transparent conductive film can
function as a heating surface, and it is preferably 0.5 .mu.m or more. As
described above, this metallic electrodes can usually be formed by
electroplating or electroless plating, and the electroplating and the
electroless plating may be used together.
Furthermore, for the sake of the mechanical protection of the electrodes
and the first transparent resin protective layer as well as chemical
protection from corrosion by moisture and the like, it is preferable to
provide a second transparent resin protective layer so as to cover the
metallic electrodes and the first transparent resin protective layer. For
the second transparent resin protective layer, there can be used a
material having a light transmission of at least 70%, preferably 80% or
more at a wavelength of 550 nm. The second transparent resin protective
layer can be formed by laminating the same kind of plastic film as the
transparent substrate with the aid of an adhesive, or applying an organic
material such as a polyester, a polyolefin or an acrylic resin, or a
silicone-based hard coating material. Or a silica sol material having a
similar function may also be used. In the case that the plastic film is
used as the second transparent resin protective layer, a usual transparent
sticky agent or adhesive can be used. Preferable examples of the adhesive
include acrylic pressure-sensitive adhesives and cyanoacrylate-based
reactive adhesives. The thickness of the second transparent resin
protective layer is usually in the range of from 1 .mu.m to 200 .mu.m,
preferably from 2 .mu.m to 100 .mu.m, more preferably from 5 .mu.m to 50
.mu.m.
When it is required that the transparent panel heater of the present
invention be adhered on a support, an adhesive layer can be formed on the
surface of the transparent substrate or the second transparent resin
protective layer. For this adhesive layer, a conventional transparent
viscous material or adhesive can be used. Preferable examples of the
adhesive include acrylic pressure-sensitive adhesives and
cyanoacrylate-based reactive adhesives. If necessary, a separator (or a
release paper) can be put on each adhesive surface to suitably prevent the
adhesive surface from adhering to another member, when products are
transported. As the separator or release paper, a polypropylene film and a
polyester film can be used. The thickness of the separator is usually in
the range of from 1 .mu.m to 200 .mu.m, preferably from 2 .mu.m to 100
.mu.m, more preferably from 5 .mu.m to 50 .mu.m.
The transparent laminate of the present invention can be applied not only
as the transparent conductive film for a transparent panel heater but also
as an electromagnetic shield material and a heat ray reflective film for a
window by the utilization of its conductivity and optical properties. When
the transparent laminate is used as the electromagnetic shield material,
the metallic electrodes formed for the transparent panel heater of the
present invention can be used as electrodes for grounding. As a
transparent thin layer and a metallic layer which are used in this
transparent laminate, the exemplified transparent thin layer and metallic
layer in the above-mentioned transparent panel heater can be directly
used.
The transparent laminate of the present invention is not limited to a
laminate in which one transparent thin layer made of the nitride and/or
the carbide and one metallic layer are laminated on one surface of the
transparent substrate. Examples of the transparent laminate of the present
invention include a laminate formed by depositing three layers of the
transparent thin layer, the metallic layer and the transparent thin layer
on the transparent substrate; a laminate formed by depositing five layers
of the transparent thin layer, the metallic layer, the transparent thin
layer, the metallic layer and the transparent thin layer on the
transparent substrate; and a laminate formed by depositing seven layers of
the transparent thin layer, the metallic layer, the transparent thin
layer, the metallic layer, the transparent thin layer, the metallic layer
and the transparent thin layer on the transparent substrate.
The above and other objects, features and advantages of the present
invention will be apparent from the following description referring to the
accompanying drawings which will illustrate examples of the preferred
embodiments of the present invention.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a sectional view of a conventional transparent panel heater.
FIG. 2 is a plan view illustrating one embodiment of a transparent panel
heater according to the present invention.
FIGS. 3a and 3b each is a sectional view along the A--A line in FIG. 2.
FIG. 4 is a perspective view of the transparent panel heater shown in FIG.
2.
FIG. 5 is a sectional view illustrating another embodiment of the
transparent panel heater according to the present invention.
FIG. 6 is a perspective view of the transparent panel heater shown in FIG.
5.
FIG. 7 is a sectional view illustrating one constitutional example of a
transparent conductive film of the transparent panel heater shown in FIG.
5.
FIGS. 8a and 8b each is a sectional view illustrating still another
embodiment of a transparent panel heater according to the present
invention.
FIG. 9 is a sectional view illustrating the first embodiment of a
transparent laminate according to the present invention.
FIG. 10 is a sectional view illustrating the second embodiment of the
transparent laminate according to the present invention.
FIG. 11 is a sectional view illustrating the third embodiment of the
transparent laminate according to the present invention.
FIG. 12 is a sectional view illustrating the fourth embodiment of the
transparent laminate according to the present invention.
DETAILED DESCRIPTION OF THE INVENTION
The present invention will be described in more detail. A transparent panel
heater 1 shown in FIGS. 2, 3a and 4 has the form of a substantially
rectangular plate. This heater is constituted of a transparent substrate 2
made of a plastic or the like, a transparent conductive film 3, an
acid-resistant transparent protective film 13, an
electrode-underlying-layer 4, a pair of metallic electrodes 5 formed on
the electrode-underlying-layer 4 and at both end portions of the heater 1
so as to electrify the transparent conductive film 3, a first transparent
resin protective layer 6 for covering a portion on the surface of the
electrode-underlying-layer 4 where the metallic electrodes 5 are not
formed, and a second transparent resin protective layer 7 for covering the
metallic electrodes 5 and the first transparent resin protective layer 6
successively laminated on the surface of the transparent substrate 2. The
transparent protective film 13 is made of an acid-resistant material such
as a carbide and/or a nitride. Furthermore, the thickness of the
electrode-underlying-layer 4 is decided so as to substantially have
light-transmission. The metallic electrodes 5 have a long and narrow
shape, and one end of each electrode constitutes a connecting portion 5a.
The connecting portion 5a is a portion to which an electric wire for
applying voltage to the electrode 5 is connected, and the second resin
protective layer 7 is not disposed on the connecting portions 5a. As shown
in FIGS. 2 and 4, the connecting portions 5a are protruded from the heater
1 itself to a direction in its surface.
The electrode-underlying-layer 4 is formed on the transparent conductive
film 3 by a method selected from dry processes using deposition particles
with the energy of a specific value or more, preferably 1 eV or more. The
thickness of the electrode-underlying-layer 4 is, for example, from 0.5 nm
to 20 nm. The metallic electrodes 5 are formed on the surface of the
electrode-underlying-layer 4 by a method selected from wet processes such
as electroless plating and electroplating, after the first transparent
resin protective layer 6 has been formed on the surface of the
electrode-underlying-layer 4 except positions where the electrodes 5 are
formed. The second transparent resin protective layer 7, which is disposed
for the mechanical and chemical protection of the electrodes 5 and the
transparent conductive film 3, is made of a resin or a film having a
visible light transmission of, e.g., 70% or more.
According to the transparent panel heater of the present invention which is
constituted as described above, the electrode layers comprising a metal
can be substantially directly formed on the transparent conductive film
without damaging the transparent conductive film, and therefore electrical
connection between the electrodes and the transparent conductive film is
good. In consequence, the connection resistance between both of them is
low, so that performance as the heater is improved and reliability is also
remarkably heightened. Furthermore, a first transparent resin protective
layer determines positions where the metallic electrodes should be formed,
and protects the transparent conductive film, whereby operating efficiency
at the time of the manufacture of the transparent panel heater can also be
remarkably enhanced.
FIG. 3b shows a section of one variant of the transparent panel heater in
this embodiment. In this transparent panel heater, the second transparent
resin protective layer 7 comprises a laminate of an adhesive layer 7a and
a plastic film 7b. This plastic film 7b is formed on the metallic
electrodes 5 and the first transparent resin protective layer 6 via the
adhesive layer 7a.
FIGS. 5 to 7 show another embodiment of the transparent panel heater of the
present invention. In FIGS. 5 to 7, the same members as shown in FIGS. 2
to 4 are represented by the same reference numerals. This | | |
