U.S. patent application number 09/886214 was filed with the patent office on 2002-05-02 for solar battery module.
This patent application is currently assigned to TDK CORPORATION. Invention is credited to Kubota, Yuichi.
Application Number | 20020050286 09/886214 |
Document ID | / |
Family ID | 14169433 |
Filed Date | 2002-05-02 |
United States Patent
Application |
20020050286 |
Kind Code |
A1 |
Kubota, Yuichi |
May 2, 2002 |
Solar battery module
Abstract
An object of the invention is to provide a solar battery module
having a high efficiency power generating ability, a harmony of
design without an odd sensation, and a freedom of design. The
object is achieved by a solar battery module comprising, on a
light-receiving surface thereof, a photoelectric conversion section
for converting incident light into electricity, the photoelectric
conversion section comprising silicon, and an insulating color film
disposed in regions other than the photoelectric conversion section
for reducing a color difference from the photoelectric conversion
section.
Inventors: |
Kubota, Yuichi; (Tokyo,
JP) |
Correspondence
Address: |
OBLON SPIVAK MCCLELLAND MAIER & NEUSTADT PC
FOURTH FLOOR
1755 JEFFERSON DAVIS HIGHWAY
ARLINGTON
VA
22202
US
|
Assignee: |
TDK CORPORATION
1-13-1, Nihonbashi, Chuo-ku
Tokyo
JP
103-8272
|
Family ID: |
14169433 |
Appl. No.: |
09/886214 |
Filed: |
June 22, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
09886214 |
Jun 22, 2001 |
|
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09276495 |
Mar 25, 1999 |
|
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Current U.S.
Class: |
136/244 ;
257/E27.125 |
Current CPC
Class: |
H01L 31/022466 20130101;
H01L 31/022483 20130101; H01L 31/048 20130101; Y02E 10/50 20130101;
H01L 31/046 20141201; H01L 31/022475 20130101; B32B 27/306
20130101; B32B 27/36 20130101; H01L 31/02008 20130101; H01L 31/0465
20141201; Y10S 136/291 20130101; H01L 31/02 20130101 |
Class at
Publication: |
136/244 |
International
Class: |
H01L 025/00 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 25, 1998 |
JP |
10-096602 |
Claims
1. A solar battery module comprising, on a light-receiving surface
thereof, a photoelectric conversion section for converting incident
light into electricity, said photoelectric conversion section
comprising silicon, and an insulating color film disposed in
regions other than said photoelectric conversion section for
reducing a color difference from said photoelectric conversion
section.
2. The solar battery module of claim 1 wherein said insulating
color film comprises pigment particles dispersed in a binder.
3. The solar battery module of claim 1 wherein said insulating
color film comprises a microparticulate white pigment as pigment
particles dispersed therein.
4. The solar battery module of claim 1 wherein said photoelectric
conversion section comprises a non-single-crystal silicon film.
5. The solar battery module of claim 1 further comprising a diffuse
transmission layer above the light-receiving surface of the solar
battery module.
6. The solar battery module of claim 5 wherein the color difference
.DELTA.E between the insulating color film and the photoelectric
conversion section as perceived through the diffuse transmission
layer is up to 5.0.
7. The solar battery module of claim 5 further comprising a
selective reflecting layer above and/or below said diffuse
transmission layer.
8. The solar battery module of claim 5 wherein said diffuse
transmission layer has an overall light transmittance of at least
20% and a haze of at least 8% in the visible spectrum.
9. The solar battery module of claim 1 wherein said photoelectric
conversion section has a transparent conductive film
10. The solar battery module of claim 1 comprising a substrate made
of any of light transmissive, heat resistant resins, glass and
stainless steel.
11. The solar battery module of claim 1 wherein a hot-melt web
having a buffer adhesive layer containing a thermosetting resin is
laminated on at least one surface of a substrate made of any of
light transmissive, heat resistant resins, glass and stainless
steel.
12. The solar battery module of claim 11 wherein said substrate
and/or said buffer adhesive layer contains a UV absorber or has a
UV absorber localized on a surface thereof.
13. The solar battery module of claim 11 wherein said buffer
adhesive layer contains an organic peroxide.
14. The solar battery module of claim 11 wherein the hot-melt web
has a support film, and the support has a glass transition
temperature of at least 65.degree. C. or a heat resistant
temperature of at least 80.degree. C. prior to thermocompression
bonding.
15. The solar battery module of claim 11 wherein the hot-melt web
has a support film, and the support has a molecular orientation
ratio (MOR) of from 1.0 to 3.0 prior to thermocompression
bonding.
16. The solar battery module of claim 11 wherein the organic
peroxide has a decomposition temperature of at least 70.degree. C.
at a half life or 10 hours prior to thermocompression bonding.
17. The solar battery module of claim 1 further comprising a
protective coating film having light transparency and heat
resistance on said photoelectric conversion section.
18. A solar battery module further comprising a layer of the
hot-melt web of claim 11 on said protective coating film.
19. A watch comprising the solar battery module of claim 1.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Technical Field
[0002] This invention relates to solar battery modules of portable
or other types as typified by electronic equipment applications
having solar batteries built therein, and more particularly, to
solar battery modules serving as photovoltaic devices which when
integrated in equipment, provide a harmony of color, and especially
of design and have a color not causing an odd sensation despite
solar battery mounting.
[0003] 2. Background Art
[0004] Solar batteries are utilized in various electronic equipment
as a power supply substitute for dry batteries. In particular, low
power consumption electronic equipment such as electronic desktop
calculators, watches, and portable electronic equipment (e.g.,
cameras, cellular phones and commercial radar detectors) can be
fully driven by the electromotive force of solar batteries, so that
the equipment can operate semi-permanently without a need for
battery replacement. Because of the semi-permanent operation
combined with cleanness,to the environment, solar batteries are of
great interest.
[0005] When solar batteries are built in electronic equipment, a
consideration must be taken from the design aspect. In particular,
modern electronic equipment are at an equal performance level
imposing difficulty to discriminate one as superior in performance
to another and the choice of a product by the consumer often
depends on the superiority of design. Because of the structure of
the solar battery, the mechanism of the light-receiving surface is
visually perceivable from the exterior. Therefore, the design is
largely affected by the difference in brightness or color between
the photoelectric conversion section having a photoelectric
converting function on the light-receiving surface and other
regions such as electrodes, isolation walls and other structures.
As a general rule, if these structures are viewed from the
exterior, most of them have a detrimental effect on the design.
[0006] JP-A 60-148174 discloses a solar battery comprising at its
front face a selective reflecting layer (multilayer interference
filter such as a dichroic mirror) which selectively reflects a
portion of visible light having a specific wavelength band,
transmits the reminder and transmits at least a portion of light in
a wavelength band contributing to the power generation of the solar
battery and a light diffusing layer disposed on the front surface
of the selective reflecting layer. With this construction, the
solar battery exhibiting a dark color becomes the lowermost layer,
the "selective reflecting layer" is provided as an upper layer on
its light-receiving surface side for changing the color to a color
of preference, and a "diffuse transmission layer" is provided as an
upper layer thereon for rendering the reflected light brighter for
reducing the dark color of the solar battery so that the color is
controllable to some extent. This allows for a freedom of design of
the color and other factors of the built-in system, thereby
mitigating the odd sensation in product design caused by
incorporating the solar battery.
[0007] The solar battery module that has been used in practice has
a photoelectric conversion film capable of producing a photovoltaic
force, a transparent electrode, a comb-shaped collector electrode
in the form of a conductive silver film formed on the transparent
electrode, and a conductive film of Ag, Cu, Ni, Mo or alloys
thereof, carbon black or graphitized carbon black serving as a
peripheral wiring electrode. The transparent conductive films known
in the art include SiO.sub.2-doped ITO films, SnO.sub.2 films
(inclusive of Sb or F doping type), and ZnO films (inclusive of In,
Al or Si doping type). Of these, ITO is commonly used. In addition,
by forming a multi-stage cell structure capable of producing a
desired high voltage on a single substrate, by forming a printed
insulating film for patterning necessary for series connection, by
effecting laser scribing/patterning by a dry process followed by
printing of an insulating resin thereon to form barriers, or by
printing conductive ink to form a laser bonding structure, an
integrated structure is established (this is more outstanding in
the case of a film solar cell which is easy to form into an
integrated structure). With respect to the color of the solar
battery as viewed from its light-receiving surface, a uniform color
surface given by the interference color of the transparent
electrode thin film (dictating the majority of the color of the
solar battery) which is overlapped by the color of the a-Si
photoelectric conversion film is mixed with patterns of various
line widths having optical characteristics including high light
reflectance, high light absorbance, high light transmittance and
specific wavelength absorption caused by the formation of the above
integrated structure, interfering with the color harmony from the
design standpoint.
[0008] One patterning process is capable of integrating a
transparent electrode formed on a substrate by sputtering through a
metal mask, a photoelectric conversion film by plasma CVD, and a
metal electrode by sputtering together, without using screen
printing or laser scribing. Of these components, the metal
electrode overlapping the mask shielding area exhibits a high
reflectance and provides a high contrast to the photoelectric
conversion section within the non-mask shielding area, giving an
odd sensation. It is quite difficult to eliminate the odd sensation
even when a diffuse transmission layer is formed on top of the cell
to provide a shield.
[0009] Accordingly, even when the selective reflecting layer and
diffuse transmission layer described in the above-referred patent
are formed as upper layers on the light-receiving surface side of
the solar battery, various pattern lines which are different in
brightness, color, reflectance and clearness due to the respective
optical characteristics are viewed as being admixed in the uniform
color surface and look like a relief. To render these pattern lines
to be not perceivable to the view is a key factor in eliminating
the odd sensation in product design caused by building in the solar
battery although the conventional solar battery design lacked a
careful consideration taken to allow for a freedom of product
design. In particular, for the "solar watch" in which the movement
can be driven by the electromotive force that a solar battery
produces at an indoor low illuminance, stringent design
requirements are imposed. Further, when a watch dial plate of a
color selected from a wide range, though frequently white, serving
as a selective reflecting layer and a diffuse transmission layer
too is provided as an upper layer on the light-receiving surface
side of the solar battery, the gap therebetween should be reduced
to a nearly contact state due to the thickness reduction demand.
The above requirements should be met even under such service
circumstances.
[0010] Further, the solar battery module is required to improve the
power generation efficiency at a given light source and
illuminance, or to form a multi-stage integrated structure to
improve the voltage to comply with the requirement of a particular
device used, to thereby improve battery performance whereas giving
the solar battery-built-in product itself a freedom of design in
harmony with the surrounding environment is also a technical task
to be solved for the solar battery to find a wider range of market
as a clean energy source.
SUMMARY OF THE INVENTION
[0011] An object of the invention is to provide a solar battery
module having a high efficiency power generating capability,
maintaining a design harmony, free of an odd sensation, having a
freedom of design, stable to changes in the environment such as
outdoor or indoor temperature and humidity, and having a high
dimensional precision.
[0012] In the solar battery module of the invention, an insulating
ink having a hiding power and a color closest to the color of the
solar battery surface (almost dictated by the interference colors
of an ITO transparent electrode thin film) is prepared, and an
insulating pattern and electrode exposed on the solar battery
surface are concealed by patterning the ink of this color by a
screen printing technique. With respect to an insulating pattern
and conductive pattern having a different color from the solar
battery surface, having a high light reflectance, high light
absorbance, high light transmittance, and specific wavelength band
absorption and exposed to the solar battery surface, the same ink
is overcoated by a similar printing technique to a minimum
thickness necessary to maintain hiding. This unifies the solar
battery surface to a uniform color. Although a contrast is
ascertainable with a pigment-dispersed ink film having a higher
content of diffuse reflectance components unlike a high reflectance
film formed by a dry process, the contrast is mitigated,
maintaining a color harmony in design.
[0013] To obtain a solar batter cell whose solar battery surface is
unified to a uniform color, which becomes the lowermost layer and
in which a "diffuse transmission layer" is provided as an upper
layer on its light-receiving surface side or to obtain a solar
battery of any desired color, the cell in which the diffuse
transmission layer itself is given a color or the "selective
reflecting layer" is provided as an upper layer on the "diffuse
transmission layer" or as an intermediate layer between it and the
solar battery is effective.
[0014] The above and other objects are achieved by the following
constructions.
[0015] (1) A solar battery module comprising, on a light-receiving
surface thereof,
[0016] a photoelectric conversion section for converting incident
light into electricity, said photoelectric conversion section
comprising silicon, and
[0017] an insulating color film disposed in regions other than said
photoelectric conversion section for reducing a color difference
from said photoelectric conversion section.
[0018] (2) The solar battery module of (1) wherein said insulating
color film comprises pigment particles dispersed in a binder.
[0019] (3) The solar battery module of (1) wherein said insulating
color film comprises a microparticulate white pigment as pigment
particles dispersed therein.
[0020] (4) The solar battery module of (1) wherein said
photoelectric conversion section comprises a non-single-crystal
silicon film.
[0021] (5) The solar battery module of (1) further comprising a
diffuse transmission layer above the light-receiving surface of the
solar battery module.
[0022] (6) The solar battery module of (5) wherein the color
difference .DELTA.E between the insulating color film and the
photoelectric conversion section as perceived through the diffuse
transmission layer is up to 5.0.
[0023] (7) The solar battery module of (5) further comprising a
selective reflecting layer above and/or below said diffuse
transmission layer.
[0024] (8) The solar battery module of (5) wherein said diffuse
transmission layer has an overall light transmittance of at least
20% and a haze of at least 8% in the visible spectrum.
[0025] (9) The solar battery module of (1) wherein said
photoelectric conversion section has a transparent conductive
film.
[0026] (10) The solar battery module of (1) comprising a substrate
made of any of light transmissive, heat resistant resins, glass and
stainless steel.
[0027] (11) The solar battery module of (1) wherein a hot-melt web
having a buffer adhesive layer containing a thermosetting resin is
laminated on at least one surface of a substrate made of any of
light transmissive, heat resistant resins, glass and stainless
steel.
[0028] (12) The solar battery module of (11) wherein said substrate
and/or said buffer adhesive layer contains a UV absorber or has a
UV absorber localized on a surface thereof.
[0029] (13) The solar battery module of (11) wherein said buffer
adhesive layer contains an organic peroxide.
[0030] (14) The solar battery module of (11) wherein the hot-melt
web has a support film, and the support has a glass transition
temperature of at least 65.degree. C. or a heat resistant
temperature of at least 80.degree. C. prior to thermocompression
bonding.
[0031] (15) The solar battery module of (11) wherein the hot-melt
web has a support film, and the support has a molecular orientation
ratio (MOR) of from 1.0 to 3.0 prior to thermocompression
bonding.
[0032] (16) The solar battery module of (11) wherein the organic
peroxide has a decomposition temperature of at least 70.degree. C.
at a half life of 10 hours prior to thermocompression bonding.
[0033] (17) The solar battery module of (1) further comprising a
protective coating film having light transparency and heat
resistance on said photoelectric conversion section.
[0034] (18) A solar battery module further comprising a layer of
the hot-melt web of (11) on said protective coating film.
[0035] (19) A watch comprising the solar battery module of (1).
OPERATION
[0036] In the prior art solar battery, no consideration has been
made on the unification of color including colored portions of fine
wires constructing various functional patterns indispensable for
battery formation other than the color of a power generating layer,
that is, a photoelectric conversion section. Therefore, an approach
of forming a selective reflecting layer and a diffuse transmission
layer having both functions of diffusing and transmitting incident
light as upper layers on the light-receiving surface while insuring
a power generating capability failed to achieve hiding by unifying
colors including the colored portions of the respective functional
patterns other than the color of the photoelectric conversion
section. According to the invention, an insulating ink having a
color closest to the color of the photoelectric conversion section
is prepared and as such, used to form an insulating pattern film on
the surface-exposed portions of the solar battery. Alternatively,
with respect to an insulating pattern and conductive pattern having
a high light reflectance, high light absorbance, high light
transmittance, and specific wavelength band absorption, an ink
hiding process of overcoating them with the same ink as an upper
layer is effective.
[0037] To obtain a solar battery of whitish or light surface color
and of high quality, a method of using as the lowermost layer the
cell in which the surface of the solar batter has been unified to a
uniform color by the above-mentioned ink hiding process, providing
a diffuse transmission layer as an upper layer on its
light-receiving surface side, and further providing a selective
reflecting layer is quite effective.
[0038] As expressed by the L*a*b* color space (representing
brightness, redness and blueness, respectively), the color
difference value .DELTA.E between the photoelectric conversion
section and the regions other than the photoelectric conversion
section coated with the insulating color ink is 3.0 or less. Also,
the color difference value .DELTA.E between the surface color of
the solar battery as perceived through the diffuse transmission
layer (based on a white filter) and the color of the insulating
color ink approximate to the surface color of the solar battery as
perceived through the diffuse transmission layer (based on a white
filter) is preferably up to 3.0, more preferably up to 2.0. In this
case, the values of the L*a*b* color space of the surface color of
the solar battery as a reference are (44.51, 6.47, 2.24),
respectively, whereas the values of the L*a*b* color space of the
surface color of the while filter (diffuse transmission layer) used
are (69.12, 0.93, 3.88), respectively. The white filter has an
overall light transmittance Tt of 47.9%, a diffuse transmittance Td
of 33.8%, and a haze value of 70.6%.
[0039] For solar watches using ordinary whitish dial plates, the
most effective insulating color ink approximate to the surface
color of the solar battery is a current insulating ink whose
pigment component is a mixture of rutile type titanium dioxide
having a high hiding power and a brown pigment (e.g., red iron
oxide) having light resistance.
[0040] As to watches for outdoor use such as sports diver watches,
on the other hand, solar watches of a design having a blackish dial
plate are popular. In this case, filters having a low brightness
such as blackish filters having an overall light transmittance of
40 to 20% in the visible spectrum, a haze value of 10 to 15%
indicating a diffuse transmittance of substantially nil, and a
brightness L* as low as about 10 are often used as the diffuse
transmission layer. When such a filter is provided on the
light-receiving surface side, the tone of this filter itself is
visually seen more blackish than the tone of the solar battery
surface color as visually seen through the filter. As a
consequence, the measure of unifying the battery surface color as
required on the use of the above whitish filter having a high
overall light transmittance and diffuse light transmittance is not
needed. It creates least odd sensation on visual observation that
the tone of the hiding ink to be overcoated as an upper layer on
the non-power generating regions of the solar battery is made
closer to the tone of reflected light which is reflected by the
photoelectric conversion film of the cell through a blackish,
low-brightness filter and visually seen substantially black. In
this case, even if the color difference .DELTA.E between the power
generating film and the ink is considerably in excess of 3.0, by
virtue of the black tone and extremely low transmittance of the
black dial plate (the dial plate used in a typical example had a Tt
of 2.6%, a Td of 2.7% and a haze of 10.7%) and the substantial
elimination of light diffusing effect, the tone of return light
which is reflected by the cell surface and visually seen through
the filter (black dial plate) largely depends on the optical
characteristics of the filter (black dial plate) only when the
black filter is used. The watch is visually seen to have a unified
black tone substantially independent of the magnitude of the color
difference between different regions within the cell, as long as
high reflectance metallic luster regions are partially absent.
BRIEF DESCRIPTION OF THE DRAWINGS
[0041] FIG. 1 is a fragmental cross-section illustrating one step
of a process for preparing a solar battery cell for use in a solar
battery module according to the invention.
[0042] FIG. 2 is a fragmental cross-section illustrating one step
of a process for preparing a solar battery cell for use in a solar
battery module according to the invention.
[0043] FIG. 3 is a fragmental cross-section illustrating one step
of a process for preparing a solar battery cell for use in a solar
battery module according to the invention.
[0044] FIG. 4 is a fragmental cross-section illustrating a solar
battery cell for use in a solar battery module according to the
invention.
[0045] FIG. 5 is a plan view illustrating one exemplary arrangement
of a circular solar battery.
[0046] FIG. 6 is a fragmental cross-section illustrating another
construction of a solar battery cell according to the
invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0047] The solar battery module of the invention comprises on a
light-receiving surface thereof, a photoelectric conversion section
for converting incident light into electricity, the photoelectric
conversion section comprising silicon, and an insulating color film
in regions other than the photoelectric conversion section, the
insulating color film serving to reduce the color difference
.DELTA.E from the photoelectric conversion section exerted by the
reflection of light containing at least the visible spectrum of
light.
[0048] The photoelectric conversion section corresponds to a
so-called power-generating layer and in solar batteries, generally
has single crystal silicon, polycrystalline silicon, amorphous
silicon (.alpha.-Si) or the like, to which a predetermined impurity
is added to form a pn junction or pin junction.
[0049] The light-receiving surface of the solar battery is a
surface on which light necessary for light-to-electricity
conversion is incident and generally designates a surface having
the photoelectric conversion section and other structures, but
excluding a protective layer or the like on the face side of the
solar battery.
[0050] The regions other than the photoelectric conversion section
designate various structures or structure films necessary for the
power generating function of the solar battery, excluding the
photoelectric conversion section. The other regions are, for
example, insulating patterns or conductive patterns, and more
illustratively, collector electrodes such as Ag conductive film,
peripheral wiring electrodes of Ag (metal thin films as typified by
Cu, Cu compounds, Ni, Mo and Al and conductive films having metal
microparticulates dispersed therein), thin films or
microparticulate-dispersed films of carbon black, graphitized
carbon black, etc. by a dry process, conductive films in which the
metal microparticulates are mixed with carbon microparticulates,
transparent electrodes of ITO, ZnO, SnO.sub.2, etc., and printed
insulating films.
[0051] The insulating color film serves to reduce the color
difference from the photoelectric conversion section. Specifically,
the color difference .DELTA.E is preferably up to 3.0, more
preferably up to 2.5, most preferably up to 2.0 while the lower
limit is not critical. Namely, the insulating color film is formed
by applying an insulating color ink which is approximate to the
surface color of the solar battery and adjusted such that the color
difference .DELTA.E from the photoelectric conversion section,
inclusive of the color of the underlying portion and reflectivity,
is preferably up to 3.0, when the film-formed surface is observed
from the exterior. When a diffuse transmission layer (based on a
whitish filter) as will be described later is used in combination,
the color difference AE between the photoelectric conversion
section and the insulating color film applied and formed on the
other regions as visually perceived through the diffuse
transmission layer is preferably up to 3.0, more preferably up to
2.0, especially up to 1.5.
[0052] Alternatively, the conductive pattern as the region other
than the photoelectric conversion section, more illustratively,
comb-shaped collector electrodes such as Ag conductive film,
peripheral wiring electrodes of Ag (metal thin films as typified by
Cu, Cu compounds, Ni, Mo and Al and conductive films having metal
microparticulates dispersed therein), thin films or
microparticulate-dispersed films of carbon black, graphitized
carbon black, etc. by a dry process, conductive films in which the
metal microparticulates are mixed with carbon microparticulates,
may be adjusted in color such that the color difference between the
conductive pattern and the photoelectric conversion section may
fall within the above-specified range.
[0053] The color difference .DELTA.E is generally expressed by
National Bureau Standards (NBS) units, and can be determined
according to the following equation for each of brightness L*,
redness a* and blueness b* in the L*,a*,b* color space (indexes
calculable from tristimulus values x, y and z as prescribed in
JIS-Z8722 and JIS-Z8727), from the differences .DELTA.L, .DELTA.a
and .DELTA.b between the region where the insulating color film has
been applied and the photoelectric conversion section.
.DELTA.E=[(.DELTA.L).sup.2+(.DELTA.a).sup.2+(.DELTA.b).sup.2].sup.1/2
[0054] Smaller values of this AE indicate that the color of the
region having the insulating color film applied thereto is closer
to the color of the photoelectric conversion section. As a general
rule, .DELTA.E values of greater than 3.0 allow a definite color
difference to be perceived, and .DELTA.E values of 12.0 or greater
permit discrimination of two fully different kinds of color.
[0055] The insulating color film preferably consists of pigment
particles dispersed in a binder. Especially preferred is a film of
pigment particles dispersed such that the film has a low
reflectance and induces diffuse reflection of light if
reflected.
[0056] The binder used herein is not critical insofar as it is
moderately resistant to weather and light, firmly adheres to
various structures or structural films necessary for the
electricity generating function of the solar battery other than the
photoelectric conversion section, and allows for effective
dispersion of pigment particles therein. When the regions other
than the photoelectric conversion section are covered with a
pattern by a screen printing technique, oil-soluble resins are
preferable to aqueous emulsions because of good wettability of the
film to the dry underlying layer. Examples of the oil-soluble
resins include epoxy resins, especially phenoxy resins, olefinic
resins, desirably polyethylene resins, polypropylene resins or
polyisobutylene resins; vinyl resins, desirably ethylene-vinyl
acetate copolymer resins, vinyl chloride-vinyl acetate copolymer
resins or vinyl acetate resins or ethylene-vinyl chloride-vinyl
acetate resins; acrylic resins, desirably methacrylate resins,
polyacrylate resins, ethylene-ethyl acrylate copolymer resins or
ethylene-methacrylic acid copolymer resins; phenolic resins;
polyurethane resins; polyamide resins; polyester resins; ketone
resins; alkyd resins; rosin resins; hydrogenated rosin resins;
petroleum resins; hydrogenated petroleum resins; maleic acid
resins; butyral resins; terpene resins; hydrogenated terpene
resins; and chroman-indene resins; with the phenoxy resins, epoxy
resins, urethane resins and saturated polyester resins being
preferred. These resins are characterized by the weather resistance
established by crosslinking, the mechanical strength as a composite
material layer of the resin with a material dispersed therein, the
bonding force to the underlying film of organic materials such as
ink film or substrate film or inorganic materials such as ITO and
.alpha.-Si, and the stability to environmental changes during
long-term service. These resins are advantageous because of a high
degree of freedom of molecular structure design. These resins (or
polymers) may be used alone or in admixture of two or more.
[0057] The particulate pigment is not critical insofar as it
provides a predetermined color close to the color of the material
of which the photoelectric conversion section is made. One or more
pigments are selected from those pigments having a high hiding
power and dyeing power. Specifically, white or nearly colorless
particulate pigments having a high hiding power such as titanium
dioxide, zinc oxide, kaolin, clay, calcium carbonate, barium
carbonate, calcium sulfate, barium sulfate, magnesium carbonate,
silica, alumina and diatomaceous earth are preferably used in
combination with pigments having a high dyeing power such as red
iron oxide, carbon black, microparticulate graphite, Prussian blue,
cobalt blue, and phthalocyanine pigments. In particular, admixing
of rutile-type titanium dioxide (TiO.sub.2) having a high hiding
power and a high degree of whiteness can produce a pastel tone
intermediate color which is effective in hiding the underlying
light-receiving surface and close to the diffuse tone of the
underlying color. This is effective in accomplishing uniformity of
tone particularly when a diffusing filter layer of whitish or light
color having an overall light transmittance of at least 30% is
provided at the top.
[0058] Fine particulate iron oxide having a dyeing power is
preferred because it offers a wide range of color selection
covering purple, brown, red and black in matching with the tone of
a solar battery of a structure having an ITO transparent electrode
stacked on an amorphous silicon thin film and because it has light
resistance and weather resistance like titanium dioxide.
[0059] Controlling the tone using a coat having pigment or dye
particles dispersed therein is advantageous in achieving proper
diffuse reflection of incident light and the uniformity of tone of
the overall cell. For example, to prevent a substantial contrast
difference between the photoelectric conversion section and a site
attributable to the high reflectance of a metallic color thin film
in the non-photoelectric conversion section covered with a mask
pattern by a dry process, a pigment dispersed, tone controlled
coating may be provided by a screen printing technique at the top
of the cell on the light-receiving side so as to cover the
non-photoelectric conversion section. This effectively mitigates
the tone difference from the photoelectric conversion section when
a diffuse transmissive filter is laid thereon, so that the
uniformity of tone of the overall cell is visually ascertained
through the filter.
[0060] Also if desired, the color may be adjusted by using along
with the above pigment a prior art well-known pigment, for example,
carbon black, cadmium red, molybdenum red, chromium yellow, cadmium
yellow, titanium yellow, chromium oxide, viridian, titanium cobalt
green, ultramarine blue, Prussian blue, cobalt blue, azo pigments,
phthalocyanine pigments, quinacridone pigments, isoindolinone
pigments, dioxazine pigments, durene pigments, perylene pigments,
perynone pigments, thioindigo pigments, quinophthalone pigments and
metal complex pigments.
[0061] The use of Prussian blue, cobalt blue or phthalocyanine
pigments as a single or main pigment is effective for equalizing
tones when single crystal silicon or polycrystalline silicon is
used as a solar battery without providing a light diffusion layer
at the top, for example.
[0062] Also, a dye is preferably used instead of or in combination
with the above pigment. Exemplary such dyes are oil-soluble dyes,
for example, azo dyes, metal complex salt dyes, naphthol dyes,
anthraquinone dyes, indigo dyes, carbonium dyes, quinoneimine dyes,
xanthene dyes, cyanine dyes, quinoline dyes, nitro dyes, nitroso
dyes, benzoquinone dyes, naphthoquinone dyes, phthalocyanine dyes,
and metal phthalocyanine dyes.
[0063] Primary particles of the pigment may have a mean particle
size of about 0.01 to about 0.8 .mu.m. The amount of the pigment
mixed is preferably about 30 to 500%, and more preferably about 50
to 380% by weight based on the binder.
[0064] As to means for forming the insulating color film, an
insulating color ink having the binder and pigment particles
dispersed and dissolved in a dispersing medium may be coated or
otherwise applied onto a pre-selected region of the light-receiving
surface of a solar battery by a screen printing technique. The
coating has a thickness of about 15 to 30 .mu.m when the underlying
is other than a silver paste electrode film having a high
reflectance and about 10 to 25 .mu.m when the underlying is other
than metals.
[0065] The dispersing medium is preferably one in which the binder
and pigment are dissolvable and dispersible and which does not
dissolve or attack a structure on the solar battery surface.
Examples include cyclohexanone, isophorone, .gamma.-butyrolactone,
N-methylpyrrolidone, terpineol, octane, isooctane, decane,
isodecane, decalin, nonane, dodecane, isododecane, cyclooctane,
cyclodecane, benzene, toluene, xylene, mesitylene, Isoper E, Isoper
G, Isoper H and Isoper L (Isoper is a trade name of Exxon), Shelsol
70 and Shelsol 71 (Shelsol is a trade name of Shell Oil), Amsco OMS
and Amsco 460 solvents (Amsco is a trade name of Spirits), and
acetates such as butylcarbitol acetate and butylcellosolve acetate.
These may be used alone or in admixture of two or more. The amount
of the binder and pigment added is about 40 to 180% by weight based
on the dispersing medium.
[0066] In addition to the above ingredients, there may be admixed
additives such as dispersants, anti-foaming agents and leveling
agents if necessary. These additives are usually added in an
overall amount of up to about 20% by weight.
[0067] As an upper layer on the light-receiving surface of the
solar battery module, a diffuse transmission layer may be provided
for the purpose of improving display quality or adding a design
effect. The diffuse transmission layer is generally based on a
white resin plate, is adjusted to a proper tone if necessary from
the design standpoint, and in some cases, is blue or green or has a
fluorescent ability to emit light upon exposure to UV light. The
material of which the diffuse transmission layer is made is not
critical and selected from transparent resins such as acrylic
resins, methacrylic resins, polycarbonate resins, polystyrene
resins, polyester resins, and polyacrylate resins. Other preferred
materials used herein are obtained by uniformly dispersing in the
foregoing resins a white filler, a finely divided product of any of
the foregoing resins, a transparent inorganic or organic filler
having a significantly different refractive index, or fine bubbles.
The material may be light-colored to a degree not to interfere with
power generation.
[0068] Especially in the watch application where the design factor
is of importance, a diffuse transmission layer of black or nearly
black color is sometimes used as the dial plate. In this case,
carbon black or graphite fine particles may be admixed in an amount
necessary to provide the color, but to insure a light transmittance
of at least 20% which is the minimum level necessary for power
generation.
[0069] On use of such a blackish, low transmittance dial plate as
the diffuse transmission layer, although the underlying cell has a
color difference .DELTA.E of at least 3 or at least 6 between the
photoelectric conversion region and the non-photoelectric
conversion region, the influence of the underlying cell on color
uniformity is mitigated by the interposing dial plate. It is then
rather advantageous that the non-photoelectric conversion region
avoids a metallic luster color having a high reflectance and is
covered with a color coating having a blackish color similar to the
dial plate and a low reflectance. The diffuse transmission layer
preferably has an overall light ray transmission of at least 20%,
more preferably at least 50%, and further preferably at least 70%
in the visible spectrum and a haze of at least 50% and more
preferably at least 70%. The percent "haze" is a transmittance of
diffused light divided by a transmittance of overall light
.times.100. The diffuse transmission layer has a thickness of about
25 to 800 .mu.m.
[0070] In addition to the diffuse transmission layer, a selective
reflecting layer may be provided. Upon receipt of visible light,
for example, the selective reflecting layer is to selectively
reflect or transmit light having a wavelength band of 450-480 nm
(blue), 550-580 nm (yellowish green) or 590-620 nm (orange). Like
the above diffuse transmission layer, the selective reflecting
layer has the effect of improving display quality or adding a
design effect. The selective reflecting layer is, for example, a
dielectric multilayer film on a glass substrate, or an interference
filter having a translucent silver thin film as the uppermost layer
and a dielectric thin film interleaved, a dichroic mirror,
diathermic mirror (cold mirror), and a light diffusing layer having
a small amount of color pigment dispersed as the filler. The
selective reflecting layer generally has a thickness of about 100
to 1,000 .mu.m.
[0071] Next, a solar battery cell included in the solar battery
module according to the invention is described.
[0072] The solar battery cell according to the invention is
illustrated in FIG. 4, for example, as comprising on a substrate 1,
a lower electrode 2, a silicon-containing layer 3 of .alpha.-Si or
the like having a pn or pin junction, an insulating layer 4, and a
transparent electrode 5 of ITO or the like. The cell further
includes a first isolating layer 6, a second isolating layer 7, a
wiring electrode 8, and a reverse-side lead-out electrode 9. It is
understood that FIG. 4 is a fragmental cross section illustrating
one exemplary construction of a solar battery cell.
[0073] In the solar battery cell, the photoelectric conversion
section designates a region where light can pass through the
transparent electrode 5 and enter the silicon-containing layer 3 to
create in its interior an electromotive force which is taken out
through the lower electrode 2 and the transparent electrode 5. The
regions other than the photoelectric conversion section encompasses
the insulating layer 4, first isolating layer 6, second isolating
layer 7, and wiring electrode 8. These portions do not contribute
to electricity generation and are formed of materials different
from the photoelectric conversion section. As a result, these
structural members interfere with the unity of design if they are
located in a region where they are visually seen from the exterior
and have a definite difference. Accordingly, the insulating color
film is provided on these regions so that the color difference is
reduced to or below the specific value, insuring the unity and
harmony of design.
[0074] Also, as shown in FIG. 5, for example, a circular solar
battery cell 21 includes photoelectric conversion sections 22, an
isolating portion 23 for isolating the photoelectric conversion
sections 22 to form a series connected structure with an increased
cell voltage, connections 27, 28 and 29 each having a series
connected wiring structure, and lead-out electrodes 25, 26. The
isolating portion 23 is generally more light-colored than the
photoelectric conversion sections 22, whereas the connections 27,
28, 29 and the lead-out electrodes 25, 26 parts of which extend
through the structure to the bottom are metallic color for wiring
electrodes having a high reflectance when a conductive silver paste
is used. If these structures are located where they are visually
perceivable from the exterior, they interfere with the unity of
design. Especially when the solar battery cell is incorporated in
the dial plate of a watch, more stringent requirements are imposed
from the design aspect, that is, the requirement for unity and
harmony becomes enhanced. Therefore, by providing the insulating
color film on these regions too, their color difference is reduced
to or below the specific value, insuring the unity and harmony of
design. If the underlying portion has a high reflectance as in the
case of a metal portion, the insulating color film may be formed as
a film of highly hiding ink to a thickness of about 30 .mu.m, for
example, optionally by coating two or more times.
[0075] After the insulating color film is formed, the solar battery
cell is preferably provided with a surface coating member or
encapsulating seal member for protecting the cell structure member
from mechanical damages, oxidation and corrosion. Of these
protective members, a lamination film is preferably used for
sealing. As the especially preferred lamination film, the following
hot-melt web is used for sealing.
[0076] For reducing the cost of the solar battery module, a
protective coating of transparent resin may be used if permitted
from a balance with the environmental resistance of the cell. That
is, a transparent insulating film obtained by thermosetting a
phenoxy resin with a melamine resin as described in Japanese Patent
Application No. 9-320476 may be used as a sole protective film.
[0077] When lamination is undertaken, that is, a lamination film
layer is formed on the surface of the solar battery cell, it
achieves the same effect as the gap provided between the outermost
surface of the cell body light-receiving portion and the rear
surface of the dial plate and just corresponding to the thickness
of the transparent laminate film support (for example, about 50 to
100 .mu.m). The extent to which the tone of the solar battery cell
is transmitted by and visually observed through the dial plate is
advantageously reduced by the light diffusing effect of the dial
plate. Therefore, the provision of the insulating color film is of
significance especially for the solar battery cell having such a
lamination seal.
[0078] The hot-melt web used herein has a buffer adhesive layer
containing a thermosetting resin on at least one surface of a
resinous support having light transparency and heat resistance.
[0079] Since the buffer adhesive layer on the resinous support is
formed of a thermosetting polymer having rubbery elasticity which
is a flexible resin having a high crosslinking density among
polymer molecular chains, the buffer adhesive layer experiences
minimal changes of dynamic physical properties with temperature and
humidity changes. The very slow changes of dynamic physical
properties permit the buffer adhesive layer to maintain its
function over a long period of time. Further, since a light
transmissive resin film having a glass transition temperature Tg of
at least 65.degree. C. and/or a heat resistant or continuous
service temperature of at least 80.degree. C. is used as the
resinous protective film, the hot-melt web does not deteriorate
even upon direct exposure to sunlight or other light sources.
[0080] The supports of light transmissive, heat resistant resins
having a Tg of at least 65.degree. C. and/or a heat resistant
temperature (Tw) of at least 80.degree. C. include fluororesin
films, for example, homopolymers such as polyethylene terephthalate
film (Tg 69.degree. C.), heat resistant polyethylene naphthalate
film (Tg 113.degree. C.), polychlorotrifluoroethylene (PCTFE, Tw
150.degree. C.) commercially available as Neoflon CTFE from Daikin
Industry K. K., polyvinylidene fluoride (PVDF, Tw 150.degree. C.,
Tg 50.degree. C.) commercially available as Denda DX film from
Denki Kagaku Kogyo K. K., and polyvinyl fluoride (PVF, Tw
100.degree. C.) commercially available as Tedlar PVF film from E.
I. duPont; and copolymers such as ethylene
tetrafluoride-perfluorovinyl ether copolymers (PFA, Tw 260.degree.
C.) commercially available as Neoflon PFA film from Daikin Industry
K. K., ethylene tetrafluoride-propylene hexafluoride copolymers
(FEP, Tw 200.degree. C.) commercially available as FEP type
Toyoflon film from Toray K. K., and ethylene tetrafluoride-ethylene
copolymers (ETFE) commercially available as Tefzel ETFE film (Tw
150.degree. C.) from E. I. duPont and AFLEX film (Tg 83.degree. C.)
from Asahi Glass K. K.; aromatic dicarboxylic acid-bisphenol
copolymerized aromatic polyester polyarylate film (PAR castings, Tw
290.degree. C., Tg 215.degree. C.) commercially available as Elmeck
from Kanegafuchi Chemical K. K. and polymethyl methacrylate film
(PMMA, Tg 101.degree. C.) commercially available as Technoloy R526
from Sumitomo Chemical K. K.; sulfurous polymer films such as
polysulfone (PSF, Tg 190.degree. C.) commercially available as
Sumilite FS-1200 from Sumitomo Bakelite K. K., and polyether
sulfone (PES, Tg 223.degree. C.) commercially available as Sumilite
FS-1300 from Sumitomo Bakelite K. K.; polycarbonate films (PC, Tg
150.degree. C.) commercially available as Panlite from Teijin
Chemicals K. K.; functional norbornene resins (Tw 164.degree. C.,
Tg 171.degree. C.) commercially available as ARTON from Nippon
Synthetic Rubber K. K.; polymethacrylate resins (PMMA, Tg
93.degree. C.); olefin-maleimide copolymers (Tg .gtoreq.150.degree.
C.) commercially available as TI-160 from Toso K. K., para-aramide
(Tw 200.degree. C.) commercially available as Aramica R from Asahi
Chemicals K. K., fluorinated polyimides (Tw.gtoreq.200.degree. C.),
polystyrene (Tg 90.degree. C.), polyvinyl chloride (Tg
70-80.degree. C.), and cellulose triacetate (Tg 107.degree. C.). Of
these, the heat resistant polyethylene naphthalate film (Tg
113.degree. C.) is preferable to the PET film because it is
superior in heat resistance in terms of Tg, heat resistance during
long term service, Young's modulus (or stiffness), rupture
strength, heat shrinkage factor, low oligomer content, gas barrier,
hydrolytic resistance, moisture permeability, temperature
coefficient of expansion, and photo-degradation of physical
properties. As compared with other polymers, the polyethylene
naphthalate film has a good overall profile of rupture strength,
heat resistance, dimensional stability, moisture permeability and
cost.
[0081] The resinous support should have a glass transition
temperature Tg of at least 65.degree. C., preferably at least
70.degree. C., more preferably at least 80.degree. C., most
preferably at least 110.degree. C. The upper limit of Tg is not
critical although it is usually about 130.degree. C. The heat
resistant or continuous service temperature should be at least
80.degree. C., preferably at least 100.degree. C., more preferably
at least 110.degree. C. The upper limit of the heat resistant
temperature is not critical, but the higher the better, and is
usually about 250.degree. C. The thickness of the resinous support
is properly determined in accordance with the parameters of a
member to be laminated therewith and the strength and flexural
rigidity required for the support although it is usually about 5 to
100 .mu.m, preferably about 20 to 90 .mu.m. A resinous support with
a thickness of less than 5 .mu.m would achieve less effective
surface protection and a hot-melt web obtained by applying an
adhesive layer thereto would be liable to deform. A resinous
support with a thickness of more than 100 .mu.m would have a low
light transmittance in the case of a film loaded with
microparticulate Al.sub.2O.sub.3 or SiO.sub.2 and become less
amenable to lamination in a roll form and hence, obstruct
continuous manufacture. The resinous support should preferably have
a rate of change of its dynamic modulus within 30%, more preferably
within 20% at a temperature of 0.degree. C. and/or 120.degree. C.
subsequent to thermocompression bonding. The magnitude of dynamic
modulus is preferably in the range of 1.times.10.sup.9 to
1.times.10.sup.12 dyn/cm.sup.2. If the rate of change of dynamic
modulus between 0.degree. C. and 120.degree. C. after
thermocompression bonding is in excess of 30%, internal stresses
would be generated in excess of the buffer action of the buffer
adhesive layer, causing a lowering of bonding force, peeling of the
hot-melt web, and deformation of the laminate.
[0082] By the term "light transmissive" resin of the support, it is
meant that at least 70%, preferably at least 80% of light in the
visible spectrum is transmitted by the support.
[0083] The resinous support should preferably have a molecular
orientation ratio (MOR) value, representative of a degree of
molecular orientation, of 1.0 to 3.0, more preferably 1.0 to 2.0,
especially 1.0 to 1.8. MOR values within this range ensure that the
laminate is little deformed. The MOR value representative of a
degree of molecular orientation is described in Convertech, March
1998, Shigeyoshi Osaki, "Quality Control of Film Sheets Using
Microwave Molecular Orientation Meter" and Seikei-Kakou, Vol. 17,
No. 11, 1995, Y. Zushi, T. Niwa, S. Hibi, S. Nagata, and T. Tani,
"Molecular Orientation Behavior On Biaxial Stretching." Larger MOR
values indicate greater anisotropy, with a MOR value of 1.0
indicating the highest isotropy.
[0084] As to the degree of molecular orientation, a single resinous
film may have different MOR values at different sites. Especially
in the event of a biaxially stretched film, the film tends to
exhibit a higher degree of molecular orientation at its edge where
it has been secured during stretching. On account of this tendency,
it is recommended that even when a film is made of a resin normally
having a satisfactory degree of molecular orientation, the film
should be examined for a degree of molecular orientation at several
sites and confirmed to have degrees of molecular orientation within
the desired range before it can be used in the invention.
[0085] Measurement of MOR is made, for example, by directing
microwave to a rotating sample and measuring the intensity of
transmitted microwave. More particularly, the interaction between
the microwave electric field with a certain frequency and dipoles
of the polymer is correlated to the inner product of their vectors.
When the sample is rotated in the microwave polarization electric
field, the intensity of transmitted microwave changes due to the
anisotropy of dielectric constant, from which a degree of molecular
orientation can be determined. The microwave used in this
measurement is not critical although it usually has a frequency of
4 GHz or 12 GHz. The meter for measuring a degree of molecular
orientation utilizing this principle is commercially available as
molecular orientation meters MOA-5001A, 5012A, 3001A and 3012A from
Shin-Oji Paper K. K. Alternatively, MOR values may be determined by
x-ray diffraction, infrared dichroic, polarization fluoroscopic,
ultrasonic, optical and NMR analyses.
[0086] Preferably the MOR value in the above-defined range should
also hold for a component of a member to which the hot-melt web is
to be applied, for example, a flexible substrate.
[0087] The buffer adhesive layer contains a thermosetting resin and
an organic peroxide. Typical thermosetting resins are
ethylene-vinyl acetate copolymers (EVA) having a vinyl acetate
content of about 15 to 50% by weight.
[0088] The organic peroxide may be selected from those compounds
which decompose to generate radicals at temperatures above
80.degree. C., especially above 90.degree. C. With the stability of
organic peroxide upon blending taken into account, it should
preferably have a decomposition temperature, which provides a
half-life of 10 hours, of at least 70.degree. C. Examples of the
organic peroxide for thermosetting resins include
2,5-dimethylhexane-2,5-dihydroperoxide,
2,5-dimethyl-2,5-di(t-butylperoxy)hexane-3, di-t-butylperoxide,
2,5-dimethyl-2,5-di(t-butylperoxy)-hexane, dicumyl peroxide,
.alpha.,.alpha.'-bis(t-butylperoxyisopropyl)-benzene,
n-butyl-4,4-bis(t-butylperoxy)valerate,
2,2-bis(t-butylperoxy)butane,
1,1-bis(t-butylperoxy)-3,3,5-trimethyl-cyclohexane,
t-butylperoxybenzoate, and benzoyl peroxide. These peroxides may be
used alone or as a mixture of two or more in any desired mix ratio.
The amount of the organic peroxide blended is preferably less than
10 parts, more preferably 0.5 to 6 parts by weight per 100 parts by
weight of the thermosetting resin.
[0089] If desired, UV absorbers may be added. The addition of UV
absorbers improves the UV light resistance of the film itself and
prevents deterioration by light of a thin film of .alpha.-Si etc.
constituting the photoelectric conversion section. Especially when
a polymer film is located on the light-receiving surface side, a
benzophenone or benzotriazole UV absorber having a UV shielding
function is preferably incorporated on the light-receiving side
surface or within the polymer and further in the buffer adhesive
layer as typified by crosslinkable EVA by surface treatment or
mixing.
[0090] As the UV absorbers, various aromatic organic compounds may
be used. Especially the compounds of the following chemical
formulae 1 are advantageous because of minimized yellowing and
minimized bleed-out onto the film surface during long-term use. Of
these, benzotriazole compounds are especially preferred. Also, zinc
oxide (ZnO) microparticulates may be similarly used as a chemically
stable inorganic UV absorber.
[0091] A transparent silica thin film which is dense at low
temperatures is formed by dispersing ZnO microparticulates in a
xylene solution of perhydropolysilazane (Mn=600 to 2,000) (N-V120
by Tonen K. K.), applying the dispersion onto a polyether sulfone
resin film to a thickness of about 0.5 .mu.m, and steam oxidizing
at 90.degree. C. (80% RM) for one hour (in the presence of a 5%
aqueous solution of trimethylamine as a catalyst), wherein ZnO is
added so as to give a SiO.sub.2/ZnO ratio of 45/55 by weight. When
this film is formed at the top on the light-receiving surface side
of the solar battery as a transparent support, it serves as an
inorganic UV-cutting, transparent, protective film effective for
improving the outdoor weather resistance of the cell.
1 Chemical name Structural formula 2,4-Dihydroxybenzophenone MW =
214 C.sub.13H.sub.10O.sub.3 1 2-Hydroxy-4-methoxybenzophenone MW =
228 C.sub.14H.sub.12O.sub.3 2 2-Hydroxy-4-methoxybenzophenone- -5-
sulfonic acid MW = 308 C.sub.14H.sub.12O.sub.6S 3
2-Hydroxy-4-octyloxybenzophenone MW = 326 C.sub.21H.sub.26O.sub.3 4
2,2',4,4'-Tetrahydroxybenzophenone MW = 246 C.sub.13H.sub.10O.sub.5
5 2-(-2-Hydroxy-5-methylphenyl)be- nzotriazole MW = 225
C.sub.13H.sub.11N.sub.3O 6
2-[2-Hydroxy-3-(3,4,5,6-tetra-hydrophthalimide-
methyl)-5-methylphenyl]be- nzotriazole MW = 385
C.sub.22H.sub.16N.sub.4O.sub.3 7
2-(2-Hydroxy-3-tert-butyl-5-methylphenyl)-5- chlorobenzotriazole MW
= 316 C.sub.20H.sub.18N.sub.3OCl 8 2-(2-Hydroxy-4-octyloxypheny-
l)benzotriazole MW = 339 C.sub.20H.sub.25N.sub.3O.sub.2 9
2-(2-Hydroxy-3,5-tert-butylphenyl)benzotriazole MW = 323
C.sub.20H.sub.25N.sub.3O 10 2-(2-Hydroxy-5-tert-octylphen-
yl)benzotriazole MW = 323 C.sub.20H.sub.25N.sub.3O 11
2-(2-Hydroxy-3,5-di-tert-amylphenyl)benzotriazole MW = 352
C.sub.22H.sub.29N.sub.3O 12 2,4-Di-tert-butylphenyl-3,5-d-
i-tert-butyl-4- 4-hydroxybenzoate MW = 439 C.sub.29H.sub.42O.sub.3
13
[0092] If desired, additives such as curing promoters may be added.
In one exemplary embodiment wherein the hot-melt web is laid on a
member to form a laminate, an organosilane compound represented by
the structure: RSi(OR).sub.3 wherein R is C.sub.2H.sub.5, for
example, may be blended in an amount of up to 6 parts by weight on
the same basis as an anti-foaming agent or foam inhibitor in the
buffer adhesive layer. In the heating/compressing step, the
organosiloxane compound reacts with the organic peroxide to
generate free radicals, which become a crosslinking agent for the
ethylene-acetic acid copolymer and are thus eventually incorporated
in the buffer adhesive layer. The organosiloxane compound has the
additional function of preventing sticking and facilitating
separation between the buffer adhesive layer and the support back
surface when the hot-melt web is stored in a roll form or as a
stack of sections.
[0093] The thickness of the buffer adhesive layer may be adjusted
as appropriate in accordance with the type of organic peroxide, the
service environment, and the member to which the hot-melt web is
laminated. Preferably the buffer adhesive layer has a thickness of
about 3 to 500 .mu.m, more preferably about 3 to 50 .mu.m, most
preferably about 10 to 40 .mu.m. A buffer adhesive layer of thinner
than 3 .mu.m would exert a less buffer effect whereas a buffer
adhesive layer of thicker than 500 .mu.m would cause a lowering of
light transmittance and tend to leave fins upon punching. It is
noted that since the adhesive layer is far more light transmissive
than the support, a thickness of up to 10,000 .mu.m is acceptable
for outdoor service or use under a high illuminance source. The
buffer adhesive layer should preferably have a dynamic modulus of
up to 5.times.10.sup.9 dyn/cm.sup.2 at 20.degree. C. and at least
1.times.10.sup.6 dyn/cm.sup.2 at 100.degree. C., more preferably
1.times.10.sup.9 to 1.times.10.sup.6 dyn/cm.sup.2 at 20.degree. C.
and 2.times.10.sup.6 to 1.times.10.sup.9 dyn/cm.sup.2 at
100.degree. C., after thermocompression bonding. Also the buffer
adhesive layer should preferably have a maximum peak value of
tan.delta. in a temperature range of up to 20.degree. C., more
preferably in a range of -100.degree. C. to +15.degree. C., after
thermo-compression bonding.
[0094] Particularly when the hot-melt web is used as a laminate
protective film, the buffer adhesive layer is provided on only one
surface of the resinous support. When a solar battery substrate and
a laminate film support have a great difference in thermal
shrinkage factor upon heating because of the material difference,
as will be described later, the buffer adhesive layer is provided
on both surfaces of the resinous support so that the cell laminate
becomes flat. The double side web is advantageous for outdoor use
in a rigorous environment. When the hot-melt web is used as joining
means in the manufacture of optical recording media and flat panel
displays, as will be described later, the buffer adhesive layer is
provided on either surface of the resinous support. In the double
side web, the resinous support and the buffer adhesive layers
should preferably be thinner within the above-described thickness
ranges. The buffer adhesive layer may also be used as a separate
sheet of 4 to 6 mm thick.
[0095] The buffer adhesive layer is provided on the resinous
support by any well-known means such as coating or extrusion
coating. The total thickness of the resinous support and the buffer
adhesive layer or layers is preferably in the range of 10 to 600
.mu.m, more preferably 10 to 120 .mu.m, further preferably 30 to 90
.mu.m, most preferably 60 to 80 .mu.m.
[0096] In the hot-melt web according to the invention, the buffer
adhesive layer is preferably embossed on its surface. Particularly
when the hot-melt web is subject to pressure lamination, it is
preferred to form the emboss pattern, especially as a pattern of
streaks extending in the same direction as the feed direction
during lamination. When the hot-melt web is used for laminating
members, the direction of the emboss pattern is arbitrary. An
optimum direction may be selected for the emboss pattern in
accordance with the laminating direction or the type of members to
be laminated. The embossing or the formation of steaks affords
bubble escape passages, minimizing the entrainment of bubbles.
Particularly when pressure lamination is carried out by a roll
laminator by wrapping a film around the laminator roll and feeding
a member thereto with the aid of the nipple roll, bubbles will find
a way of easy escape in the laminating direction. The size, spacing
and population of streaks to be formed by embossment are not
critical. For example, the buffer adhesive layer is preferably
embossed to a surface roughness Ra of 0.4 to 10 .mu.m, more
preferably 0.6 to 0.8 .mu.m and an average peak-to-peak spacing of
50 to 180 .mu.m, more preferably 60 to 140 .mu.m. The embossing
means is not critical and conventional embossing techniques may be
used. Alternatively, a release film is once embossed and that
emboss pattern is transferred to the buffer adhesive layer.
[0097] Next, the method for preparing the solar battery module is
described. There are furnished a hot-melt web having a buffer
adhesive layer on at least one surface of a light transmissive,
heat resistant resin support having a Tg of at least 65.degree. C.
and a member to be laminated, typically a solar battery sheet
having an upper or light-receiving surface to be protected. The
hot-melt web is laid on the member preferably such that the buffer
adhesive layer of the web is in close contact with the
light-receiving surface of the member. This assembly is passed
through a roll laminator where thermocompression bonding is carried
out, preferably at a temperature of 100 to 120.degree. C. and a
linear pressure of 20 to 70 g/cm. Although reference is mainly made
to a one-side laminate having only one hot-melt web laid on a
member, a double-side laminate having hot-melt webs on opposite
sides of a member may also be employed depending on the type of a
member to be laminated and the service environment. In the case of
the double-side laminate, a sandwich of a member between hot-melt
webs, with the buffer adhesive layers faced to the member, may be
passed through a roll laminator for achieving thermocompression
bonding.
[0098] The composite sheet thus obtained is then cut to sections of
predetermined dimensions. The sheet sections are stacked and
received in a container equipped with heating and compressing
means, typically an autoclave. Preferably in a dry air or nitrogen
atmosphere, especially in a nitrogen atmosphere, a substantially
uniform mechanical pressure of 0.01 to 5.0 kg, especially 0.1 to
5.0 kg is applied to the stack of sheet sections in a direction
perpendicular to the major surfaces of the sheet sections,
typically in a vertical direction while the stack is heated at a
temperature of at least 70.degree. C., especially 140 to
180.degree. C. (The pressure applied during heating is 3 to 15
kg/cm.sup.2.) This heat pressing is continued for about 30 to 120
minutes for achieving heat crosslinking, deaeration and a firm
bond, producing a laminate according to the invention. The heating
temperature and hydrostatic pressure applied by the heating and
compressing means may be adjusted in accordance with the particular
member and hot-melt web employed. The mechanical pressure may be
applied at any desired timing. Preferably the pressure is
maintained even after heating and until cooling to room
temperature. One preferred procedure involves the step of bubble
removal by heating above the curing temperature of the adhesive
layer, more preferably at a temperature of 70 to 100.degree. C.,
applying a pressure of 5 to 10 kg/cm.sup.2, and maintaining the
temperature and pressure for 15 to 60 minutes, and the subsequent
step of thermosetting by heating at a higher temperature, more
preferably at a temperature of 100 to 170.degree. C., especially
120 to 170.degree. C. and maintaining the pressure of 3 to 15
kg/cm.sup.2, especially 5 to 10 kg/cm.sup.2 at the temperature for
a further 5 to 60 minutes, especially 15 to 60 minutes.
[0099] Since lamination is carried out by means of a roll
laminator, the influence of irregularities on the member to be
laminated, for example, a fine pattern of comb-shaped electrodes on
a solar battery or a fine pattern of insulator for cell isolation
is minimized. More particularly, the member/hot-melt web assembly
is fed to a roll laminator while the structured surface of the
member is in contact with the buffer adhesive layer which is heated
to a more fluidized state. The assembly is clamped between the
elastic rolls of the laminator while it is moved forward. The
bubbles which are probably left in the shades of pattern lines on
the structured surface are effectively expelled out by the
hydraulic forces acting thereon due to the sliding stresses
produced between the elastic rolls.
[0100] Residual bubbles which are not completely removed by the
roll laminator are removed in the subsequent heat crosslinking step
by the heating and compressing means. At the thermocompression
bonding stage, it is preferred that a heat resistant elastomer
sheet is laid on the upper (light-receiving) surface of each
composite sheet section and a metal cover plate is laid thereon. A
plurality of metal cover plate/elastomer sheet/composite sheet
section units are placed one on top of the other. A mechanical
pressure is vertically applied to the stack via a high rigidity,
flat smooth platen of SUS or the like by a compressing means such
as a pneumatic cylinder. In this way, the module sheet having a
functional thin film on a plastic substrate which has been randomly
deformed by the thermal contraction and internal stresses of the
functional thin film is laminated with the hot-melt web into a
device which is now corrected to be smooth and flat.
[0101] It is understood that the member to be laminated consists of
plural different components which are different in rigidity and
thickness, for example, .alpha.-Si, ITO, aluminum alloy, interlayer
insulating films, and sealing insulating protective film in the
event of a solar battery. By applying a mechanical pressure to the
laminate sections lying in the above-described layer structure in
the heat crosslinking step by heating and compression, the
components are laminated and integrated with the hot-melt web so
that random deformations contained in the composite sheet whose
layers have different heat shrinkage factors and internal stresses
at the end of their formation may be readily corrected.
Additionally, since the stack of plural composite sheet sections is
heat pressed, flattening correction can be simultaneously carried
out on a plurality of sheet sections, which is advantageous for
mass production. As compared with coating, the lamination of the
hot-melt web is effective in endowing the surface with superior
flatness and smoothness, resulting in products having a good outer
appearance. This adds to the commodity value of products.
[0102] Although within the integrated laminate, the support and
laminate member constitute the majority of members dictating the
thickness of the device, flatness and smoothness are achieved to a
level at least equal to the use of rigid supports of metals (e.g.,
SUS) and glass having a thickness of about 100 .mu.m. As compared
with sheet structures using such metal supports or glass supports,
the laminate can be punched by simple pneumatic press working and
formed with through-holes by means of a YAG laser. Therefore,
compared with the sheet structures using metal supports or glass
supports, thin film devices can be precision worked by simple means
in a high productivity manner, contributing to a cost reduction in
mass-scale production. When combined with patterning by a screen
printing technique, the lamination process can be quickly adapted
to changes of device design, achieving a further cost
reduction.
[0103] The heat resistant elastomer sheet to be stacked is not
critical insofar as it withstands the heating temperature mentioned
above. A proper choice may be made of well-known heat resistant
elastomers, for example, heat resistant silicone rubber,
fluoro-rubber (e.g., Viton), and fluorosilicone rubber. The
thickness of the heat resistant elastomer sheet is not critical
although it is usually in the range of about 0.5 to 10 mm.
[0104] The metal cover plate may be made of aluminum, stainless
steel, brass, or steel sheets. Aluminum is preferable because of
its light weight and good heat transfer. The thickness of the metal
plate is not critical although it is usually about 0.2 to 3 mm. The
metal plate may be surface treated by well-known means, for
example, aluminum anodizing, plating such as chromium, nickel or
nickel-chromium plating, or paint coating.
[0105] In the solar battery module of the invention, for the
purpose of cost reduction, a light and weather resistant coating
may be provided on the solar battery cell surface instead of the
hot-melt web mentioned above. As compared with the above-mentioned
hot laminated assembly, such a resin coating is somewhat inferior
in flatness and weather resistance, but contributes to low-cost,
mass-scale manufacture because the laminating and flattening steps
can be omitted. This is suitable especially when the module is
built in an equipment or mainly intended for indoor use.
[0106] For the resin coating used to this end, a coating film
having a well-balanced profile of transparency, toughness, adhesion
to the transparent electrode or the like, surface hardness, heat
resistance, freeze resistance, low moisture absorption, and low gas
barrier is preferable. In particular, in order that the resin be
soluble in organic solvents, have a molecular weight (Mn) of about
2,000 to 3,000 or lower, and maintain the above-mentioned
mechanical strength as a coating, base resin capable of exerting
the above-mentioned properties are preferably those thermosetting
resins which undergo crosslinking reaction with melamine resins or
non-yellowing isocyanate compounds (low-temperature-curable blocked
isocyanate in which isocyanate groups of non-yellowing isocyanate
compounds are blocked with active methylene groups of acetylacetone
(Duranate "MF-K60X" by Asahi Chemicals K. K.) and
low-temperature-curable blocked isocyanate in which isocyanate
groups of non-yellowing isocyanate compounds are blocked with MEK,
oxime, etc.) below 200.degree. C., which is the heat resistant
temperature of plastic supports, to form higher molecular weight
resins. The thermosetting resins have improved transparency and
undergo least color changes due to aging and optical
degradation.
[0107] Exemplary preferred fluorochemical resins include Lumiflon
resins (Asahi Glass K. K.) which are copolymers of ethylene
trifluoride or ethylene tetrafluoride with a vinyl monomer in which
the H moiety of the ethylene chain is replaced by --OR, --OH or
--ORCOOH; polyurethane resins obtained by condensing aliphatic or
alicyclic polyesters or polyether prepolymers with non-yellowing
isocyanate compounds (e.g., PTMG/Colone HX cured product by Nippon
Polyurethane K. K.); cured products of saturated polyester resins
(copolymers of such esters of ethylene glycol or neopentyl glycol
with phthalic acid or adipic acid, e.g., Viron by Toyobo K. K.)
with the above-mentioned non-yellowing isocyanate or melamine
compounds; cured products of epoxy resins (e.g., Epikoat 1009 by
Yuka Shell K. K.) or phenoxy resins (PKHH by UCC) with the
above-mentioned curing agents; and phosphazene monomers having
functional groups capable of polymerization reaction and curable
with partially saponified acrylic polyols or the above-mentioned
non-yellowing isocyanate compounds (e.g., PPZ Monomer by Idemitsu
K. K.).
[0108] The coating may be formed by such techniques as coating,
screen printing, and spin coating.
EXAMPLE
Example 1
[0109] Preparation Process
[0110] As shown in FIG. 1, a solar better cell-forming structure
comprising a lower electrode layer 2, an amorphous silicon layer 3
having a pn junction or pin junction, an insulating layer 4, and an
ITO transparent electrode layer 5 formed on a flexible substrate 1
was provided with a through-hole 10 and open channels 10a by laser
machining.
[0111] Next, as shown in FIG. 2, a first isolating layer 6 and a
second isolating layer 7 were formed over the ITO transparent
electrode layer 5 where the open channels 10a were formed. Further,
as shown in FIG. 3, a wiring electrode layer 8 was formed over the
first isolating layer 6 and through-hole 10.
[0112] Next, as shown in FIG. 4, after a reverse-side lead-out
electrode 9 was formed if necessary, an insulating color ink which
was prepared in accordance with the following insulating color
resin composition 1 was applied onto the wiring electrode 8 to form
an insulating color film 11.
[0113] The insulating color resin composition 1 whose color was
approximate to the surface color of the solar battery's
photoelectric conversion section is used, in the case of the solar
batter cell shown in FIG. 4, by coating it over the insulating film
(primary printed resin) 4, isolating layers 6, 7 exposed on the
solar battery surface (secondary printed resin), electrode of
silver paste serving as wiring electrode 8 (for suppressing the
high light reflectance of the electrode).
2 Insulating color resin composition 1 Parts by weight Phenoxy
resin (PKHH by UCC, Mn = 15400) 14 Cyclohexanone 15 Isophorone 15
Rutile titanium dioxide (Ishihara Industry 32 K.K., mean particle
size 270 nm) Red iron oxide (Toda Industry K.K., 15 mean particle
size 300 nm) Dispersant (oleic acid) 3 Anti-foaming agent (TSA-720
by 1 Toshiba Silicone K.K.) Leveling agent (KS-66 by Shin-Etsu 1
Silicone K.K.)
[0114] The phenoxy resin was completely dissolved in a solvent
mixture of cyclohexanone and isophorone, and titanium dioxide and
red iron oxide were dispersed therein together with the dispersant
in a zirconia ball mill for 48 hours. The anti-foaming agent and
leveling agent were then added to the dispersion, which was mixed
for a further 2 hours.
[0115] Next, the following hot crosslinking reaction components
were added to the dispersion, which was mixed and dispersed for a
further 20 minutes, obtaining the resin composition for insulating
color film.
3 Parts by weight n-butylated melamine resin (Uban 21R 5 by
Mitsui-Toatsu Chemical K.K.) Curing accelerator (Catalyst 6000 0.03
by Mitsui-Toatsu Chemical K.K.)
[0116] The thus obtained insulating resin composition ink was
primary printed onto the insulating layer 4 shown in FIG. 1 through
a 150-mesh stainless steel screen and thermoset in an oven at
160.degree. C. for 10 minutes. On this insulating film, the ITO
transparent electrode layer 5 was then formed by argon gas
sputtering. During this sputtering step, no damages were found on
the insulating film and the uniform ITO transparent electrode layer
5 was deposited.
[0117] Next, on the first and second isolating layers 6 and 7 shown
in FIG. 2 and the wiring electrode 8 shown in FIG. 4, the
insulating color ink was again printed through a 150-mesh stainless
steel screen and thermoset in an oven at 160.degree. C. for 10
minutes. The insulating color ink was coated onto the insulating
film 4 and isolating layers 6, 7 or overlaid for suppressing the
high light reflectance of the wiring electrode 8 of silver paste in
this way, and thus covered the overall surface layer of the solar
battery except for the photoelectric conversion section. There was
obtained a flexible amorphous silicon solar battery cell which was
uniformed to a color substantially equal to the surface color of
the photoelectric conversion layer.
[0118] Next, a lamination film comprising a PEN film having
excellent physical strength including environmental reliability as
a support and a buffer adhesive layer applied thereon was laid on
the light-receiving surface of the solar battery and sealed
thereto.
[0119] More specifically, the lamination film used was prepared by
furnishing a PEN film of 50 .mu.m thick (Tg: 113.degree. C.) as the
flexible film support having light transparency and heat
resistance. The buffer adhesive was prepared by blending dicumyl
peroxide as an organic peroxide in an ethylene-vinyl acetate
copolymer resin (EVA, vinyl acetate content about 15-50% by weight)
in an amount of 7 parts by weight of the curing agent per 100 parts
by weight of the EVA and further blending minor amounts of
additives such as a curing accelerator. The buffer adhesive was
applied to one surface of the resin film support to a thickness of
20 .mu.m to form the buffer adhesive layer.
[0120] After the lamination, flattening treatment was carried out
to a level meeting the specifications of watch parts, obtaining a
film solar cell complying with the watch dial plate.
[0121] Alternatively, it is acceptable to simplify the
above-mentioned procedure by omitting the laminate sealing while
insuring the reliability of the cell to some extent, that is, to
cover the surface of the cell on the light-receiving side solely
with a transparent protective coating film having light resistance.
By protecting the surface solely with the coating film in this way,
the cost of the solar battery can be reduced so that it is marketed
at a low price.
[0122] Next, onto the solar battery cell having the uniformed tone
and flexibility, a whitish watch dial plate having the optical
functions of a diffuse transmission layer and a selective
reflecting layer (material: plastic plate of acrylic resin with
alumina ultrafine particles dispersed therein, thickness: 500
.mu.m, overall light transmittance 52%) was joined with
substantially no gap left therebetween, obtaining a solar
watch.
[0123] Comparative Example
[0124] A solar battery cell was prepared as in Example 1 except
that an insulating color resin composition 2 of the following
formulation was used, following which a solar watch was similarly
assembled.
4 Insulating color resin composition 2 Parts by weight Phenoxy
resin (PKHH by UCC, Mn = 15400) 20 Cyclohexanone 40 Isophorone 30
High-resistance carbon black (Degussa, 4 mean particle size 25 nm)
Aerosil (Degussa, 10 mean particle size 15 nm) Dispersant (oleic
acid) 3 Anti-foaming agent (TSA-720 by 1 Toshiba Silicone K.K.)
Leveling agent (KS-66 by Shin-Etsu 1 Silicone K.K.)
[0125] Test Method
[0126] For the flexible solar battery cell having a tone uniformed
to the photoelectric conversion section and the solar watch having
the cell integrated with the whitish watch dial plate in Example
and the solar batter cell and the solar watch with a whitish watch
dial plate in Comparative Example, "tristimulus values" and "L*a*b*
color space" (representing brightness, redness and blueness,
respectively) were measured using a high-speed calorimetric
spectrophotometer CMS-35sp by Murakami Color Institute K. K.
[0127] For the watch dial plate, an overall light transmittance was
also measured according to JIS K-7361, and a comparison was made by
carrying out visual evaluation under natural light and a
fluorescent lamp.
[0128] Results
[0129] 1) The solar battery cell prepared in Example, the solar
battery cell prepared in Comparative Example, and the solar watches
of Example and Comparative Example were subjected to colorimetry
analysis by the above-described test method.
[0130] Based on the L*a*b* values, the color difference AE in color
of reflected light of incident natural light between the surface
color of the photoelectric conversion section and the insulating
resin layer prepared in Example was calculated, with the result
indicating a value of 2.39. This value represents the color at the
limit level below which the cell can be used, without further
modification, as a cell having a uniform color between the power
generating film and the surface and as the watch dial plate or
portable solar battery.
[0131] 2) For the solar watch prepared in Example, a color
difference value .DELTA.E of reflected color was determined for the
purpose of comparison with the color to incident natural light
through a whitish watch dial plate of general use level, with the
result indicating a value of 0.16, which ranges up to 0.2 NBS unit.
On visual observation, the presence of the solar battery below the
whitish watch dial plate could not be sensed, even over especially
outstanding color difference regions such as the isolating portion
23 (crisscross pattern), connections 27, 28, 29 and lead-out
electrodes 25, 26 (circumferential pattern).
[0132] 3) The solar battery prepared in Comparative Example showed
a .DELTA.E value of 34.86, and the solar battery having the whitish
watch dial plate rested thereon showed a .DELTA.E value of at least
12 NBS units. On visual observation, the crisscross and
circumferential patterns were definitely viewed, indicating a
serious problem from the design aspect.
[0133] 4) For the solar watch prepared in Example, a color
difference value .DELTA.E of reflected color was determined for the
purpose of comparison with the color to incident natural light
through a special blackish watch dial plate for diver watches on
outdoor use, with the result indicating a value of 3.35, which
ranges beyond 0.3 NBS unit.
[0134] On visual observation, the color ink of insulating color
resin composition 2 used in Comparative Example was applied to the
isolating portion 23 (crisscross pattern), connections 27, 28, 29
and lead-out electrodes 25, 26 (circumferential pattern) by a
screen printing technique so that these regions and even the
overcoat layer were covered with the black color ink film.
[0135] This color ink film had a color difference value 66 E of at
least 12 from the photoelectric conversion region as reported in
Comparative Example of Table 1.
[0136] However, the special black watch dial plate used herein had,
as measured according to JIS K-7361, an overall light transmittance
as low as 26.0% and a diffuse transmittance of 2.7%, indicating the
substantial absence of the shielding effect of reflected light by
light diffusion of a filter, and a low haze value of 10.4%.
[0137] The use of such a black dial plate causes a substantial loss
of the light quantity available to insure the operation of a solar
watch, which is detrimental to the power generation efficacy of the
cell. However, it is advantageous for the design as a black dial
plate for sports use. Although the .DELTA.E value associated with
the use of a black color ink film was 3.35, that is, in excess of
3.0, the non-power generating regions were less outstanding on
visual observation. By the way, when the non-power generating
regions were similarly covered with an ink film of insulating color
resin composition 1 used on the white dial plate in Example, and
the above-mentioned special black dial plate having a low
transmittance and low haze was rested thereon, the color difference
.DELTA.E from the standard cell was 2.50, indicating a greater
color difference than in the case of insulating color resin
composition 2. This suggests that the use of such a dial plate
having special optical characteristics is advantageous in stressing
blackness from the design aspect.
[0138] In addition to the cell having the outer configuration shown
in FIG. 5 and the above-described structure, a cell of the same
outer configuration and having an integration structure on the
transparent film support rear surface was fabricated by oxidizing
the above-described perhydroxypolysilazane with steam to form a
silica layer 14 (containing ZnO UV-cutting agent) below a
transparent PEN film 1 of 75 .mu.m thick, and depositing below the
silica layer 14, a transparent conductive layer ITO 15, a ZnO layer
17, an .alpha.-Si layer 13, a ZnO transparent conductive layer 18
(for light confinement), and an aluminum layer (metal underlying
electrode) 12 to thereby construct a solar battery. The
cross-sectional structure is shown in FIG. 6. To protect the
aluminum underlying electrode 12, a transparent protective layer
such as a transparent insulating layer obtained by thermosetting a
phenoxy resin with a melamine resin as in Japanese Patent
Application No. 9-320476 or a laminate film may be disposed below
it.
[0139] In the process of fabricating such a cell, the respective
thin layers were formed by covering the underlying with a metal
mask and effecting patterned layer deposition by sputtering or
plasma CVD. Patterning by laser scribing or screen printing was
avoided.
[0140] However, when the cell was visually observed from the
light-receiving surface side as shown in FIG. 5, the high
reflectance due to metallic luster of the lowermost layer or
aluminum electrode made the crisscross lines especially outstanding
and provided a further increased contrast to the power generating
region, which could not be hidden even when various dial plates
were rested thereon.
[0141] Accordingly, a process of covering the top side
(light-receiving side) of the PEN film, along the regions of the
crisscross lines corresponding to the high reflectance aluminum
electrode, with an ink layer of insulating color resin composition
1 used in Example 3 (by a screen printing/patterning technique) was
effective in improving the design feature when a dial plate was
rested thereon.
[0142] 5) The whitish watch dial plate used herein had an overall
light transmittance of 52.3%, a diffuse light transmittance of
32.5%, and a haze value of 62.2% as measured according to JIS
K-7361, acquiring a sufficient light quantity to insure indoor
operation as a solar watch.
[0143] 6) It was confirmed that a solar watch or portable solar
battery which is satisfactory from the design aspect can be
fabricated by incorporating a filter (dial plate) in the solar
battery in which the color difference value .DELTA.E between the
surface color of the power generating film and the cell coloring
ink falls within 2.0 as calculated from the L*a*b* values and the
regions other than the power generating film are covered with the
ink to achieve the unity of surface color.
[0144] The results described above are summarized in Table 1.
5 TABLE 1 a b L red yellow c Bright .dwnarw. .dwnarw. Color H Color
Sample X Y Z x y -ness green blue saturation Hue difference Example
cell 14.52 14.19 14.49 0.35 0.33 44.51 6.47 2.24 8.25 10.84 Ink 1
13.67 13.09 13.62 0.34 0.32 42.91 8.11 1.55 8.25 10.84 Color
difference 2.39 Example cell + Dial 46.37 48.75 56.76 0.31 0.32
75.31 0.07 -3.52 -3.52 271.1 plate Ink 1 + Dial plate + 46.39 48.72
56.71 0.31 0.32 75.28 0.23 -3.52 3.53 273.7 Dial plate color 0.16
difference Comparative 46.37 48.75 56.76 0.31 0.32 75.31 0.07 -3.52
-3.52 271.1 Example cell Comparative ink 2 1.16 11.24 1.65 0.29
0.31 10.82 -0.61 -3.28 3.33 259.7 Color difference + 34.86 Dial
plate color >12 difference Example cell + 0.77 0.73 1.12 0.29
0.28 6.55 3.13 -4.59 5.56 304.4 Black dial plate Black dial plate +
0.49 0.49 0.78 0.28 0.28 4.46 0.76 -3.48 3.57 282.4 Ink 2 + Black
dial 3.35 plate color difference
[0145] As seen from the above, in the example of the "solar watch"
with stringent design requirements in which a primarily white,
light-color "watch dial plate" is provided as the top layer of the
solar battery, by constructing to the uniform color cell structure
in which the exposed surface portion of the solar battery is as
approximate to the battery surface color as possible and using the
"ink," "cell" and "filter (dial plate)" such that the color
difference value .DELTA.E in reflected color to incident sunlight
between the cell and the cell coloring ink as sensed through the
whitish watch dial plate may fall within the range of up to 2.0 NBS
units, a "solar watch" which was satisfactory from the design
aspect could be fabricated.
Example 2
[0146] A solar battery module was prepared as in Example 1 except
that a resin coating of the following composition was formed on the
cell surface instead of the lamination film. The solar battery
module was tested as in Example 1, finding that it had a certain
effect of unifying tones and operated as a solar battery without
problems.
6 Composition of resin coating Parts by weight OH-bearing
fluoro-resin 20 (Lumiflon LF200F by Asahi Glass K.K., hydroxyl
value 26 mg KOH/g) .gamma.-butyrolactone 40 isophorone 30
Anti-foaming agent (TSA-720 by 3 Toshiba Silicone K.K.) Leveling
agent (KS-66 by Shin-Etsu 1 Silicone K.K.)
[0147] The Lumiflon resin was completely dissolved in a solvent
mixture of .gamma.-butyrolactone and isophorone, and dispersed in a
zirconia ball mill for 48 hours. The anti-foaming agent and
leveling agent were then added to the dispersion, which was mixed
for a further 2 hours. The following hot crosslinking reaction
components were added.
7 Parts by weight Methylated melamine resin (Sumimal 4 M-40ST by
Sumitomo Chemical K.K.) Catalyst (dodecylbenzenesulfonic acid)
0.13
[0148] The mixture was mixed and dispersed for a further 20
minutes, obtaining a resin coating composition having transparency
and insulation and effective for the protection and sealing of the
cell light-receiving surface.
[0149] The thus obtained composition was applied to the surface of
the solar battery cell by a screen printing technique and thermoset
at 150.degree. C. for 90 minutes, forming a resin coating of about
20 .mu.m thick.
Benefit of the Invention
[0150] There has been provided a solar battery module having a high
efficiency power generating ability, a harmony of design without an
odd sensation, and a freedom of design.
* * * * *