TECHNICAL FIELD
[0001] This invention relates to a solar battery powered watch provided with a solar battery
as a power supply.
BACKGROUND TECHNOLOGY
[0002] A solar battery powered watch provided with a solar battery as a power supply has
been conventionally generally structured in a manner that the solar battery is mounted
on the surface of a dial under a glass so as to be seen from the outside in view of
the fact that the solar battery absorbs light to generate electric power.
[0003] However in such a structure, since the solar battery has a peculiar deep violet color,
colors of the dial and designs of the dial are largely restricted, which makes it
difficult to bring out an ornamental value of the watch.
[0004] Aiming to solve such a problem, there is proposed an invention having coloring means
at a light receiving surface of a solar battery as disclosed, for example, in a publication
of JP-A 5-29641.
[0005] That is, in the same publication, cholesteric liquid crystal is microcapsuled and
the surface of the solar battery is coated with the microcapsuled liquid crystal as
a binder.
[0006] However, in the coloring means disclosed in the same publication, there are few colors
to be selected as those of the dial, and the surface of the dial becomes a deep color,
and hence it does not enhance the ornamental value thereof. Particularly, there is
a problem that the aforementioned coloring means can not produce white which is a
basic color and is frequently used as a color of the dial of the watch.
[0007] EP 0 242 088 A2 discloses a solar battery powered watch according to the preamble
of claim 1.
[0008] Swiss patent CH 522 247 discloses a covering member made of ceramic containing alumina
as a main constituent, wherein the alumina particles forming the base of the ceramic
to be sintered have a diameter of at most 10µm and the resulting covering member can
be coloured, for instance, white.
[0009] DE-OS 1 548 007 discloses light reflection layers or faces serving for concentrating
incident light to photoelements.
[0010] FR 2 212 573 A discloses a positioning frame for positioning a covering member of
a watch which is disposed around an outer periphery of the covering member and has
recessed parts formed in the positioning frame such that projecting parts formed in
the periphery of the covering member can engage these recessed parts.
[0011] Under the circumstances, it is an object of this invention to realize a solar battery
powered watch capable of designing a dial with colors including white, and of transmitting
light which is sufficiently necessary for generating electric power for the solar
battery.
[0012] These objects are achieved by a solar battery powered watch according to the claim
1.
[0013] Further developments of the invention are given in the dependent claims.
[0014] It is also provided a solar battery powered watch capable of improving impact resistance
of a covering member.
[0015] With such an arrangement, since the surface of the covering member can be seen from
the outside through the glass, if the covering member is also used as the dial, it
is possible to provide the solar battery powered watch provided with a dial having
a desired color if the color of the covering member is adjusted to the desired color
.
[0016] According to this invention, the covering member is molded out of ceramic. Since
the ceramic in general looks white, it is possible to form white dial (covering member)
without coloring the dial.
[0017] It is needless to say that the covering member molded out of ceramic can prevent
the solar battery from being seen from the outside. Further, since incident light
appropriately is transmitted through the ceramic made of a porous material, the solar
battery can be charged without a problem.
[0018] Since ceramic is easily colored, its color other than white is freely adjustable.
[0019] Further, this invention provides a solar battery powered watch having light transmittance
so that the solar battery is irradiated with sufficient light, and a preferable structure
of the covering member to show a white appearance.
[0020] That is, if the covering member is molded out of ceramic containing aluminum as a
main constituent, it can show a preferable white, and if an average diameter of the
ceramic grains ranges from 5 µm to 40 µm, and the covering member is molded to a thickness
ranging from 0.2 mm to 0.5 mm, the covering member can keep high external quality
and transmit light sufficiently for charging the solar battery.
[0021] In case that the covering member is utilized as a dial, dial patterns such as an
indicator, lettering for a brand name, and the like are inscribed on the surface of
the covering member. As a result, since the light transmittance is prevented by the
dial patterns, it is unavoidable that light transmittance area of the covering member
is reduced. Further, light returned to the surface of the covering member owing to
diffusion of light in the covering member is absorbed by an interface between the
covering member and the dial patterns so that the amount of light which reaches the
solar battery is further reduced.
[0022] Accordingly, it is preferable to form an arbitrary dial patterns on the surface of
the covering member and to interpose light reflection layers or light reflection faces
between the surface of the covering member and the dial patterns to keep the watch
driving stable by minimizing the reduction of the amount of irradiation of light to
the solar battery.
[0023] In such a structure, light which is incident on the covering member as the dial first
enters the inside of the covering member which is light transmittant. The thus entered
light is diffused inside the covering member and directed to various directions. As
a result, most of the incident light spreads out while it is diffused inside the covering
member, and a part of the incident light is returned to the surface of the covering
member.
[0024] The amount of light which is returned to the surface is substantially uniform on
the surface of the covering member. Since the light returned to a part where the dial
patterns are formed is reflected on the light reflection layers or light reflection
faces, and it is returned to the inside of the covering member, and then it is transmitted
to the solar battery, the amount of irradiation of light to the solar battery can
be increased.
[0025] In the case of the conventional solar battery powered watch having no reflection
layer at the interface between the covering member and the dial patterns, the light
returned to the part where the dial patterns are formed inside the covering member
is all absorbed by the dial patterns. In such a manner, since the light which spreads
out while it is diffused inside the dial is absorbed by the dial patterns, and hence
the amount of irradiation of light to the solar battery is significantly reduced.
[0026] The arrangement of the solar battery powered watch having light reflection layers
or light reflection faces can eliminate the loss of light caused by the light absorption
at the interface between the covering member and the dial patterns, and can reduce
the loss in the amount of irradiation of light.
[0027] It may be possible to laminate a transparent substrate to the surface of the covering
member, and to form arbitrary patterns on the surface of the transparent substrate,
and further light reflection layers or light reflection faces are interposed between
the surface of the transparent substrate and the dial patterns. Since the covering
member is molded out of ceramic, it has a property that it is fragile and breaks easily
when impact loading is applied to the covering member. Particularly, when the covering
member is accommodated to move freely in the case, there is good possibility that
the covering member strikes strong against a peripheral sidewall of the opening of
the case and that it is broken when an impact loading is applied.
[0028] Accordingly, it is preferable that the outer rim of the covering member is in contact
in advance with the peripheral sidewall of the opening of the case, whereby the movement
of the covering member in the case is restricted to prevent the breakage of the covering
member.
[0029] Further, if at least the outer rim of the covering member is pressed against the
peripheral sidewall of the opening of the case by an elastic member, the covering
member can be surely brought into contact with the peripheral sidewall of the opening
of the case.
[0030] In order to carry out the positioning of the covering member utilizable as the dial
in the case, it may be possible to dispose a positioning frame around the outer periphery
of the covering member, to provide projecting parts or recessed parts in the positioning
frame, to provide recessed parts or projecting parts in the covering member for engagement
with the projecting parts or recessed parts of the positioning frame, and to provide
positioning means for positioning the positioning frame relative to the movement.
[0031] With such an arrangement, the covering member can be easily positioned relative to
the movement, which becomes a positioning standard relative to respective constituents
in the case, by way of the positioning frame.
[0032] An ornamental frame may be provided inside the case along the rim of the opening
of the case for enhancing the value of the watch as ornamental goods.
[0033] In this case, when the inside of the periphery of the covering member is brought
into contact with the ornamental frame, the movement of the covering member is restricted
inside the case to prevent the breakage of the covering member.
[0034] As described above, when the inside of the periphery of the covering member serves
as a supporting face, the projecting parts do not contact the case even if the positioning
projecting parts are formed at the periphery of the covering member. Accordingly,
even if the covering member receives an impact loading, there is no likelihood of
occurrence of stress concentration on the projecting parts, so that the tolerance
against an impact can be further enhanced.
[0035] Further, when the positioning projecting parts are provided on the periphery of the
covering member, if a gap is defined between the periphery of the covering member
and the case, and the projecting parts provided on the periphery of the covering member
are disposed in the gap, the projecting parts do not contact the case. Accordingly,
even if the covering member receives an impact loading, there is no likelihood of
occurrence of stress concentration on the projecting parts, so that the torelance
against an impact can be further enhanced.
[0036] In the solar battery powered watch which is structured such that the opening formed
at the back side of the case is covered by a case back, and the covering member, the
solar battery and the movement are held by a casing frame, it is preferable to interpose
an intermediate member made of a resin material between the case back and the movement.
[0037] As a result, when the solar battery powered watch receives an impact loading, the
intermediate member functions to suppress the deformation of the covering member,
thereby preventing the breakage of the covering member with more reliability.
[0038] If the intermediate member is disposed at a position opposite to the ornamental frame,
there is no possibility that a shearing force acts on the covering member which is
held between the ornamental frame and the intermediate member, thereby preventing
the breakage of the covering member with more reliability.
[0039] Further, even if an elastic member is interposed between the case back and the casing
frame, the elastic member functions to suppress the deformation of the covering member,
thereby preventing the breakage of the covering member with more reliability.
[0040] For positioning the covering member relative to the movement, it may be structured
such that thorough holes are defined in the covering member at a region contacting
the ornamental frame, and end portions of the fixed pins are engaged in the through
holes, and the fixed pins protrude from the underside of the covering member, and
throughholes are defined in the solar battery for insertion of the fixed pins, and
further a means for securely holding the fixed pins is provided on the movement.
BRIEF DESCRIPTION OF THE DRAWINGS
[0041] Fig. 1 is a cross sectional view of a solar battery powered watch according to a
first embodiment of this invention.
[0042] Fig. 2 is a plan view of a covering member which is one of the constituents of the
solar battery powered watch of the first embodiment and is used as a dial.
[0043] Fig. 3 is a table showing a condition for fabricating the covering member, average
diameters of ceramic grains, and results of measurement of transmittance and transparency
of each sample.
[0044] Fig. 4 is a plan view of a dial (covering member) of a solar battery powered watch
according to a second embodiment of this invention.
[0045] Fig. 5 is a cross sectional view taken along the line A-A of Fig. 4.
[0046] Figs. 6 through 9 are cross sectional views for explaining function and effect of
the solar battery powered watch according to the second embodiment of this invention.
[0047] Fig. 10 is a cross sectional view of a solar battery powered watch according to a
third embodiment of this invention.
[0048] Fig. 11 is a plan view of a covering member which is one of the constituents of the
solar battery powered watch of the third embodiment and is used as a dial.
[0049] Fig. 12 is a cross sectional view of the solar battery powered watch according to
a modification of the third embodiment of this invention.
[0050] Fig. 13 is a cross sectional view of the solar battery powered watch according to
another modification of the third embodiment of this invention.
[0051] Fig. 14 is a cross sectional view of a solar battery powered watch according to a
fourth embodiment of this invention.
[0052] Fig. 15 is a plan view of a covering member which is one of the constituents of the
solar battery powered watch of the fourth embodiment and is used as a dial.
[0053] Fig. 16 is a cross sectional view of the solar battery powered watch according to
a modification of the fourth embodiment of this invention.
[0054] Fig. 17 is a cross sectional view of the solar battery powered watch according to
another modification of the fourth embodiment of this invention.
[0055] Fig. 18 is a cross sectional view of the solar battery powered watch according to
still another modification of the fourth embodiment of this invention.
BEST MODE FOR CARRYING OUT THE INVENTION
[0056] A best mode for carrying out this invention will be now described with reference
to the attached drawings.
(First Embodiment)
[0057] A solar battery powered watch according to a first embodiment of this invention will
be now described with reference to Figs. 1 and 2. Fig. 1 is a cross sectional view
of the solar battery powered watch according to the first embodiment of this invention,
and Fig. 2 is a plan view of a covering member which is one of the constituents of
the solar battery powered watch of the first embodiment and is used as a dial.
[0058] As shown in Fig. 1, the solar battery powered watch accommodates a movement 2, a
solar battery 3, and a dial 4 in a case 1.
[0059] The case 1 has an opening (face side opening) 1a at the front side thereof, and another
opening (back side opening) 1b at the back side thereof. A glass 5 made of transparent
glass or sapphire is provided in the face side opening 1a. Meanwhile, the back side
opening 1b can be covered by a case back 6. Respective constituents in the case 1
can be accommodated through the back side opening 1b.
[0060] Respective constituents in the case 1 are arranged in the order of the dial 4, the
solar battery 3 and the movement 2 from the side close to the glass 5, wherein a light
receiving surface (front surface) 3a of the solar battery 3 is opposed to the glass
5.
[0061] The movement 2 houses therein an electric double layer capacitor for storing a generated
electric power of the solar battery 3, a crystal oscillator serving as a time base
source, a semiconductor integrated circuit for generating driving pulses for driving
a hand 7 based on an oscillation frequency of the crystal oscillator, a step motor
for driving a train wheel mechanism second by second upon reception of the driving
pulses, and the train wheel mechanism, which are respectively not shown.
[0062] The dial 4 serves as a covering member for covering the surface of the solar battery
3, described later, so that the solar battery 3 can not be seen from the outside.
Dial patterns such as an indicator, lettering for a brand name, and the like are inscribed
on the surface of the dial 4 for performing a primary function of the inherent dial
4.
[0063] The dial 4 is in advance fixed to the movement 2 by way of a positioning frame 8.
That is, as shown in Fig. 2, positioning pins 2a and 2b are provided on the movement
2 at the front periphery thereof, and the positioning pins 2a and 2b penetrate the
solar battery 3 and protrude from the positioning frame 8 at their arranging portions
(front periphery of the solar battery 3). Meanwhile, positioning holes 8a and 8b are
bored in the positioning frame 8. When the positioning pins 2a and 2b are engaged
in the positioning holes 8a and 8b, the positioning frame 8 can be fixed to the movement
2 at a given relative position thereof.
[0064] Further, recessed parts 8c and 8d are provided on the positioning frame 8 at the
inner periphery thereof, while projecting parts 4a and 4b are provided on the dial
4 at the outer periphery thereof. When the projecting parts 4a and 4b are engaged
in the recessed parts 8c and 8d, the dial 4 can be fixed to the positioning frame
8.
[0065] The dial (covering member) 4 is formed by molding ceramic containing alumina and
zirconia as a main constituent. Particularly, in the first embodiment, the dial 4
is made of ceramic containing alumina as the main constituent. The ceramic made of
alumina as the main constituents looks a preferable white, and has high mechanical
strength.
[0066] If the dial 4 is to be colored, pigment is dispersed in the ceramic or the surface
of the dial 4 is colored by coating means so that the dial 4 is easily colored with
a desired color.
[0067] The solar battery 3 is formed of thin films of non-monocrystalline silicon or films
of monocrystalline silicon, or films of compound semiconductor.
[0068] In the first embodiment, the light receiving surface 3a of the solar battery 3 is
covered with the dial 4, causing the light receiving surface 3a to be unrecognizable
from the outside. Accordingly, the peculiar deep violet color of the solar battery
3 can not be seen, and hence the dial 4 looks white which is particular to alumina.
[0069] Although it is sufficient that the dial 4 and the solar battery 3 are merely overlapping
each other, they can be joint to each other by a transparent adhesive, and the like
in an assembling step thereof, if necessary.
[0070] A method of fabricating the solar battery 3 will be now described.
[0071] First, an insulating film (not shown) is formed on the entire surface of a metallic
substrate made of e.g., brass by use of a sputtering system. The insulating film is
made of silicon oxide in the thickness of about 100 nm.
[0072] Next, an electrode film (not shown) is formed by use of the same sputtering system.
The electrode film employs aluminum containing, e.g., 1 wt% of silicon. The electrode
film may be formed on the entire surface of the metallic substrate or may be partly
formed on the insulating film.
[0073] When the electrode film is partly formed on the insulating film, a metal mask is
employed. The metal mask is formed of a thin sheet of a metallic material, and has
an opening in a region forming the electrode. The metal mask having the opening therein
is put on the substrate, and it is arranged in the sputtering system, then the electrode
film is formed in the opening of the metal mask.
[0074] Subsequently, a solar battery layer (not shown) composed of thin films of non-monocrystalline
silicon is formed on the surface of the electrode film. The solar battery layer is
composed of, for example, amorphous silicon films (non-monocrystalline silicon films)
each having a structure of a p-i-n type conductivity.
[0075] The solar battery layer is formed by use of a plasma chemical vapor deposition system.
Silane gas (SiH
4) is used as reactive gas. An amorphous silicon film of n-type conductivity is formed
by adding phosphine gas (PH
3) as dopant, and an amorphous silicon film of p-type conductivity is formed by adding
diborane gas (B
2H
6) as dopant. An i-type amorphous silicon film may be formed without adding any dopant.
[0076] The thickness of the p-type film, and the n-type film, respectively, ranges from
50 to 100 nm, and the thickness of the i-type film ranges from 50 to 300 nm.
[0077] The solar battery layer composed of the amorphous silicon films of p-i-n junction
can be formed continuously with the plasma chemical vapor deposition system.
[0078] Then, a transparent electrode film (not shown) is formed on the surface of the solar
battery layer by use of the sputtering system, thereby obtaining a solar battery 3.
In forming the transparent electrode film, indium tin oxide (ITO) is used.
[0079] The metal mask may be used for forming the transparent electrode film on parts of
the surface of the solar battery layer. The metal mask is prepared from a thin metal
sheet and has openings in regions where the transparent electrode film is formed.
The formation of the transparent electrode film within the openings of the metal film
is carried out by placing the solar battery inside the sputtering system, where the
layer of the solar battery is overlaid with the metal mask having the openings.
[0080] A method of fabricating the dial 4 formed by molding ceramic containing alumina as
a main constituent is described hereafter.
[0081] Firstly, a mold is filled up with a mixture of a ceramic material containing alumina
as a main constituent, and a binder. In this case, alumina in powder form of about
0.3 µm in grain diameter is used, and an amount of the binder added represents about
3.0 % of the mixture.
[0082] For the ceramic material, alumina at purity of 99.5 % or higher is used, and for
the binder, polyvinyl alcohol (PVA) is used.
[0083] In the case of the ceramic material of alumina at a purity less than 99.5 % being
used, the dial 4 was found tinted with the color of impurities, significantly reducing
declining its light transmittance. Therefore, it is preferable to use the ceramic
material of high purity alumina at 99.5 % or higher for fabricating the dial 4 for
a desirable white appearance.
[0084] Then, a pressurizing process is applied to the mold filled up with the mixture of
the ceramic material and the binder. At this time, pressure of about 1 ton / cm
2 is applied to the mold.
[0085] Hereupon, as shown in Fig. 2, the dial 4 has projecting parts 4a and 4b, a display
window 4c for displaying dates and days of the week, and a center hole 4d through
which a spindle of the second hand protrudes from a movement of the watch.
[0086] Subsequently, a first sintering process is applied to the dial 4, removing the binder
composed of PVA which was added to the ceramic material. The first sintering process
is applied in the atmosphere at a temperature in the range of about 800 to 1600°C
for a duration of about 120 minutes. As a result of the first sintering process applied,
the dial 4 shrinks slightly in its outer dimensions because the binder is removed,
but undergoes little change in the thickness thereof.
[0087] Thereafter, a second sintering process is applied at a temperature higher than that
for the first sintering process. The second sintering process is applied at a temperature
(1500 to 1900°C) close to the fusion point of ceramic for a duration of about 300
minutes. The second sintering process is applied in a vacuum to increase the density
of the ceramic.
[0088] The second sintering process applied at a temperature close to the fusion point of
the ceramic as described above is conductive to progress in crystallization. Consequently,
the diameter of the ceramic grains in the final stage of the steps is much larger
than 0.3 µm.
[0089] By means of such a step of enlarging the diameter of the ceramic grains as described
above (crystallization step), light transmittance of the ceramic can be enhanced.
The enhanced light transmittance of the dial 4 permits a sufficient amount of light
to be transmitted to the solar battery 3, which is quite desirable from the viewpoint
of securing enough generated power necessary as a source of power supply to the watch.
[0090] However, it has been found as a result of various studies that the step of enlarging
the diameter of the ceramic grains applied excessively results in excessive transparency
of the dial 4 due to a decrease in a amount of light scattered inside the ceramic.
When the dial 4 becomes excessively transparent, it can not fulfill its function as
a covering member to cause the solar battery to be unrecognizable from the outside.
[0091] In this embodiment, a preferable diameter of the ceramic grains in forming the dial
4 will be described later. However, prior to this description, steps to be taken upon
completion of the second sintering process will be first described.
[0092] Upon completion of the second sintering process, the surface of the dial 4 is flattened
by removing undulation thereof by use of a grinder. There are various methods of grinding,
for example, simultaneous grinding of both faces, grinding of one face by pasting
the ceramic on a working jig using wax, and the like. For grinding, diamond powders
and a diamond grinder are used.
[0093] As for the size of a workpiece in grinding, it is preferable to adopt a thickness
in the order of 0.4 mm. Normally, the thickness of the workpiece when the pressurizing
process thereof in the mold is completed may be preferably thicker by about 0.3 mm
than that of the finished dial 4.
[0094] Then, a third sintering process is applied to the ceramic at a temperature (1200
to 1600°C) lower than that for the second sintering process for a duration of about
120 minutes. By applying the third sintering process in the atmosphere, dirt adhered
to the surface of the ceramic is removed through oxidation reaction, and the like.
[0095] Then, barrel polishing is applied to the dial 4 by use of a barrel polishing apparatus.
In such barrel polishing, balls made of copper (Cu) may be used. As a result of the
barrel polishing, the surface roughness of the dial 4 is reduced thereby, enhancing
the light transmittance of the dial 4. Furthermore, the barrel polishing enables burrs
generated around the outer rim and in the corners of the dial 4 to be removed and
in addition, roundness to be provided in the corners of the dial 4.
[0096] Thereafter, a fourth sintering process is applied to the ceramic at a temperature
(1200 to 1600°C) lower than that for the second sintering process for a duration of
about 120 minutes. The fourth sintering process is also applied in the atmosphere
for cleaning up the surface of the ceramic by further removing dirt adhered to the
surface. Normally, the third and fourth sintering processes may be applied under the
same condition.
[0097] Finally, indicators, lettering for a brand name and the like, graphic, a symbol (dial
patterns) are inscribed on the surface of the dial 4 by a printing method to complete
the dial 4.
[0098] In case that undulation on the surface of the ceramic, and fluctuation in the thickness
thereof can be minimized in the course of the pressurization process of the ceramic
using the mold, and the first and second sintering processes thereof, the grinding
and the third sintering processes to be applied thereafter may be omitted.
[0099] The inventors of this application fabricated samples (A to M) of the dial 4 by use
of the method of fabrication under varying conditions. Fig. 3 shows fabricating conditions
of the samples, and measurement results of samples including average diameters of
ceramic grains of the samples, light transmittance of respective samples, and transparency
of the same.
[0100] Alumina used in fabrication of the samples was 99.9 % pure, and the thickness of
the samples (A to M) of the dial was 0.4 mm. As a result of the second sintering process
applied in vacuum, the ceramic of each of the samples acquired high density in the
range of 3.90 to 3.92 g / cm
3.
[0101] The average diameters of the ceramic grains were measured through observation of
the cleaved surfaces of the samples using an electron microscope. The light transmittances
of the samples were determined by measuring a power output value of the solar battery
3 when the samples (A to M) of the dial were placed on the solar battery 3. Herein,
the light transmittance was determined as 100 % when a power output value of the solar
battery 3 without the samples (A to M) of the dial placed thereon was obtained.
[0102] Further, transparency of the samples (A to M) of the dial was determined by visual
observation therethrough on the basis whether or not two black lines drawn in parallel
at a spacing of 0.3 mm can be separably identified. Some of the samples, through which
such identification was achieved, are marked with blank circles while other samples
are marked with crosses. The spacing of 0.3 mm between the two black lines corresponds
to the size of smallest letters normally inscribed on the dial of a watch.
[0103] As is evident from the measurement results shown in Fig. 3, when the average diameter
of the ceramic grains is 45 µm or greater, the transparency of the dial samples increases
excessively, significantly reducing the dial's performance to cover the solar battery
3. The results of a survey made on sensuous impression of a plurality of subjects
actually inspecting a solar battery powered watch fabricated according to the structure
shown in Fig. 1 indicate that the criteria for assessing the transparency, adopted
by the inventors of the invention, substantially agree with the subjects' sensuous
perception on the transparency.
[0104] It has been found from the measurement results described above that the average diameter
of the ceramic grains need be preferably kept at about 40 µm or less for the dial
4 to permit a maximum amount of light irradiating the solar battery 3 to be transmitted
therethrough, and yet to cover sufficiently the solar battery 3.
[0105] On the other hand, it has become apparent that when the average diameter of the ceramic
grains becomes less than 5 µm, the light transmittance of the dial declines sharply.
Accordingly, it can be stated that the average diameter of the ceramic grains need
be preferably kept in the range from 5 µm to 40 µm for the dial 4 to obtain whiteness
while permitting the solar battery 3 to maintain a necessary power generation capability.
[0106] Further, the thickness of the dial 4 is preferably kept in the range between 0.2
mm and 0.5 mm because impact resistance thereof deteriorates when the thickness becomes
less than 0.2 mm. On the other hand, when the thickness is greater than 0.5 mm, the
watch itself becomes excessively thick, depreciating the commercial value thereof.
However, from the viewpoint of strength, the dial 4 with the critical thickness of
0.1 mm at the minimum can be put to practical use.
[0107] Reviewing again the measurement results shown in Fig. 3 while taking into account
such constraint as described above in respect of the thickness of the dial 4, it can
be stated that, as the dial 4 became thinner by 0.1 mm, the light transmittance thereof
increased by about 1.5 %, but that the transparency thereof did not undergo noticeable
change.
[0108] Therefore, it is appropriate to state that the average diameter of the ceramic grains
should be preferably in the range from 5 µm to 40 µm regardless of the thickness of
the dial 4 provided that the thickness thereof is in the range between 0.1 mm and
0.5 mm.
[0109] Further, it is readily understood on the basis of the measurement results shown in
Fig. 3 that the average diameter of the ceramic grains can be controlled by regulating
sintering temperatures, the duration of sintering, sintering atmosphere, and the like.
[0110] When the dial 4 fabricated under the adequate conditions described above was incorporated
in the solar battery powered watch having the structure shown in Fig. 1, the watch
was found to continue moving normally without stopping due to shortage of generated
electric power. Furthermore, the dial 4 was natural white in color.
(Second Embodiment)
[0111] A solar battery powered watch according to a second embodiment will be now described.
[0112] The feature of the second embodiment resides in a structure of dial patterns which
are formed on the surface of a dial (covering member) 4 of the solar battery powered
watch shown in Fig. 1. The other entire structure and the method of fabricating the
solar battery, and the method of fabricating the dial are the same as those of the
first embodiment (see Fig. 1), and hence the detailed explanations thereof are omitted
while numerals in figures are denoted in common with those of the first embodiment.
[0113] Fig. 4 is a plan view of a front surface of the dial, and Fig. 5 is a cross sectional
view taken along the line A-A in Fig. 4.
[0114] As shown in Fig. 4, dial patterns 10 such as indicators, lettering for a brand name
and the like, graphic, a symbol are inscribed on the surface of the dial 4.
[0115] As shown in Fig. 5, light reflection layers 11 are interposed between the surface
of the dial 4 and the dial patterns 10. The light reflection layers 11 are formed
by masking the surface of the dial 4, then applying a vacuum evaporation to a thin
metal film such as aluminum, nickel, and the like or etching the thin metal film formed
on the entire surface of the dial 4 in the form of the dial patterns 10. After the
light reflection layers 11 were formed, the dial patterns 10 may be printed on the
surface of the light reflection layers 11. Further, the dial patterns 10 may be printed
using ink in which fine particles of gold or aluminum is dispersed, then heat drying
or high temperature sintering process is applied to the dial patterns 10 so as to
form the light reflection layers 11.
[0116] The effect of the formation of the light reflection layers 11 will be now described
with reference to Figs. 6 through 8.
[0117] Fig. 6 schematically shows lights 52a, 52b, 52c, 52d which are respectively incident
to a substrate 51 having light transmittance and light diffusibility. The light diffusibility
of the substrate 51 appears because of the diffusion of light inside the substrate
51. In Fig. 6, the light diffusibility is illustrated as sharp change of directions
of the lights inside the substrate 51. Such diffusing phenomenon is caused by discontinuity
of refractive index at interfaces between fine particles.
[0118] When the lights are changed in directions, a part of the lights, such as a light
53a is emitted outside from the surface of the substrate 51. This is phenomenally
similar to the surface reflection. Other lights such as the lights 54b, 54c and 54d
are emitted from the back surface of the substrate 51, and they are transmitted lights.
[0119] Although Fig. 6 schematically shows a light by a single line, it is noted that for
example, the entire incident light 52d does not necessarily form the optical path
denoted by the line shown in Fig. 6 to be emitted but a part of the light 52d is emitted,
because there actually occurs diffusion of light inside the substrate 51 with a certain
probability. However, the following typical expression is sufficient for explaining
the light, and the probability problem is not referred to in this explanation.
[0120] Fig. 7 shows light absorption bodies 62 formed at a part of the surface (incident
side) of the substrate 51 in addition to the structure of Fig. 6.
[0121] In Fig. 7, supposing that the lights 52a, 52b, 52c and 52d shown in Fig. 6 respectively
form the optical paths inside the substrate 51 like the case of Fig. 6, the lights
52a, 52b and 52d which travel along the surface of the substrate 51 are respectively
absorbed by the light absorption bodies 62 as evident from Fig. 7 in the midway of
the respective optical paths, then they are finally changed to heat.
[0122] That is, in the structure of Fig. 7, the lights are not emitted from the substrate
51 like the lights 54b, 54c and 54d as shown in Fig. 6. However, the light incident
to the substrate 51 as the light 52c does not meet the light absorption bodies 62
in the course of traveling so that it is emitted from the back surface of the substrate
51 as the light 54c like the case of Fig. 6.
[0123] Fig. 8 shows light reflection bodies 73 each made of a metallic material and replaced
with the light absorption bodies 62 of Fig. 7.
[0124] Supposing the lights 52a, 52b, 52c and 52d shown in Fig. 6 respectively form the
optical paths inside the substrate 51 like the case of Fig. 6, lights incident from
the inside of the substrate 51 to the light reflection bodies 73 are reflected substantially
100% and are returned to the inside of the substrate 51. Accordingly, the lights which
are incident as the lights 52a, 52b, 52c and 52d are respectively emitted from the
back surface of the substrate 51 as the lights 54a, 54b, 54c and 54d.
[0125] As for the light 54a, although it is emitted from the back surface of the substrate
51, there is good possibility that it is emitted from the front surface of the substrate
51 depending on the course of diffusion inside the substrate 51.
[0126] Let us consider as follows by applying the above explanation of the principle to
the solar battery powered watch of the second embodiment of this invention.
[0127] The dial 4 shown in Fig. 5 corresponds to the substrate 51 shown in Figs. 6 through
8. When the dial patterns 10 are directly formed on the surface of the dial 4 (without
interposing the light reflection layers 11), the dial patterns 10 correspond to the
light absorption bodies 62 of Fig. 7, from which it is evident that light absorption
phenomenon as explained in Fig. 7 will occur.
[0128] Meanwhile, in the second embodiment in which the dial patterns 10 are formed on the
surface of the dial 4 by way of the light reflection layers 11 (see Fig. 5), the light
reflection layers 11 correspond to the light reflection bodies 73 of Fig. 8 from which
it is understood that the light reflection phenomenon as explained in Fig. 8 will
occur.
[0129] As is evident from the above explanations, in the structure including the dial patterns
10 which are formed on the dial 4 having light transmittance and light diffusibility
without interposing the light reflection layers 11, a part of the incident lights
is absorbed by the dial patterns 10 and it is attenuated.
[0130] On the other hand, according to the second embodiment having the light reflection
layers 11, most of lights which are incident to the dial 4 can transmit to the back
surface of the substrate 51 without being attenuated. That is, it is possible to eliminate
loss of light caused by absorption of light at the interface between the dial 4 and
the dial patterns 10, and also it is possible to reduce the amount of light irradiating
the solar battery 3 to a minimum.
[0131] Particularly, a part of the lights, which is incident to the dial 4 at the peripheries
of the dial patterns 10 and is diffused horizontally, is easily absorbed by the dial
patterns 10, so that the amount of light reaching the solar battery is further attenuated
by the amount corresponding to several times as large as that of an area ratio (normally
about 5 %) of the dial patterns 10 relative to the dial 4, thereby exerting an non-negligible
influence upon the solar battery powered watch provided with the solar battery 3.
The light reflection layers 11 provided in the second embodiment performs such function
and effect that they suppress the attenuation of the amount of transmitted light,
and increase the amount of light irradiating the solar battery 3.
[0132] Fig. 9 is a view of a solar battery powered watch according to another modification
of the second embodiment.
[0133] That is, a transparent substrate 81 is provided in addition to the constituent of
Fig. 8, and the light reflection body 73 is formed on the front surface of the transparent
substrate 81. An incident light 52e, shown as an example, travels directly inside
the transparent substrate 81, and is diffused inside the substrate 51, then it is
returned to the transparent substrate 81, then it travels directly inside the transparent
substrate 81, and then it is reflected on the light reflection body 73. Thereafter,
the incident light 52e travels directly inside the transparent substrate 81, and is
diffused inside the substrate 51, and finally it is emitted from the back surface
of the substrate 51 as the emitted light 54e.
[0134] Incidentally, since only the substrate 51 has light diffusibility, the transparent
substrate 81 plays a role to permit the light to directly travel therein.
[0135] When the structure shown in Fig. 9 is applied to the dial 4, a transparent substrate
having direct light traveling property is laminated to the surface of the substrate
51 made of ceramic, and the dial patterns 10 are formed on the surface of the transparent
substrate by way of the light reflection layers 11. Even in such a structure, it is
possible to prevent light from being absorbed by the dial patterns so that the light
can sufficiently irradiate the solar battery 3. Further, such a change of structure
has an effect that a free designing of the dial for the solar battery powered watch
can be enhanced.
[0136] Next, a method of forming the light reflection layers 11 and the dial patterns 10
on the dial 4 will be described in detail.
[0137] After the dial 4 was fabricated by the method of fabricating the dial, which was
explained in the first embodiment, the light reflection layers 11 are formed on the
surface of the dial 4.
[0138] That is, the light reflection layers 11 are formed on the dial patterns 10 using
ink composed of powdered gold which is dispersed in and mixed with varnish by a tampon
printing method. Thereafter, the light reflection layers 11 are temporally dried at
the temperature of about 100 °C, further it is sintered by a heat of about 750 °C
so that only gold is sintered to form the light reflection layers 11.
[0139] Finally the tampon printing is applied to the surface of the light reflection layers
11 using UV hardening type ink of black pigment, and it is temporally dried at the
temperature of about 80 °C, then it is irradiated with UV rays to completely solidify
the light reflection layers 11.
[0140] The dial 4 which was fabricated with the above steps is incorporated into the case
1 shown in Fig. 1. As a result, inoperative condition such as stop of the watch which
will be caused by the shortage of generated electric power of the solar battery 3
does not occur, and the watch remains operative normally. Furthermore, the dial was
natural white in color.
[0141] The area ratio of the dial patterns 10 relative to the dial 4 is 4.3 %, and the light
transmittance of the dial 4 is 51 % before the light reflection layers 11 and the
dial patterns 10 are formed, and it is 49 % after the light reflection layers 11 and
the dial patterns 10 were formed.
[0142] As for the dial as a comparative example, which was fabricated by omitting the printing
step using ink composed of powdered gold which is dispersed in and mixed with varnish
among the aforementioned steps, the light transmittance is 51 % before the dial patterns
are formed and it is 42% after the dial patterns were formed.
[0143] Although in the second embodiment set forth above, the light reflection layers 11
are interposed between the dial 4 and the dial patterns 10, the back surfaces of the
dial patterns (surfaces contacting the dial 4) become the light reflection faces if
the dial patterns 10 per se are formed of the light reflective material. Even such
light reflection faces can reflect the scattered light inside the dial 4 to the solar
battery 3, so that they can achieve the same effect as the light reflection layers
11.
(Third Embodiment)
[0144] A solar battery powered watch according to a third embodiment of this invention will
be now described.
[0145] The feature of the third embodiment resides in fixing means of the dial 4 (covering
member) in the case 1 and positioning means relative to the movement 2 in the solar
battery powered watch shown in Fig. 1. The other entire structure and the method of
fabricating the solar battery, and the method of fabricating the dial are the same
as those of the first embodiment (see Fig. 1), and hence the detailed explanations
thereof are omitted while numerals in figures are denoted in common with those of
the first embodiment.
[0146] Fig. 10 is a cross sectional view of the solar battery powered watch according to
the third embodiment, and Fig. 11 is a plan view of a dial (covering member) and a
positioning frame which are respectively constituents of the solar battery powered
watch.
[0147] As shown in Fig. 11, recessed parts 12 and 13 each having a circular shape or a rectangular
shape are provided on the dial 4 at positions close to the dial patterns 10 which
indicate twelve o'clock and six o'clock. Meanwhile, projecting parts 14 and 15 which
are engaged in the recessed parts 12 and 13 are formed in the positioning frame 8.
[0148] The positioning frame 8 is made of a resin material or a metallic material, and it
is arranged on the upper surface of the solar battery 3 at the outer periphery of
the dial 4. The positioning holes 8a and 8b are respectively bored in the positioning
frame 8 while the positioning pins 2a and 2b are respectively provided on the front
face of the movement 2 at the outer periphery thereof. The positioning pins 2a and
2b penetrate the solar battery 3 and protrude to the surface of the solar battery
3. The positioning frame 8 can be positioned relative to the movement 2.
[0149] If the dial 4 is arranged in a state where the projecting parts 14 and 15 are engaged
in the recessed parts 12 and 13, the dial 4 can be positioned relative to the movement
2 by way of the positioning frame 8.
[0150] Meanwhile, the surfaces of the dial 4 and the positioning frame 8 are flush with
each other, and the surface of the positioning frame 8 which contacts the case 1 is
flush with the case 1 while the dial 4 and the positioning frame 8 are aligned with
each other in height.
[0151] The movement 2, the solar battery 3 and the outer periphery of the positioning frame
8 are respectively held by a frame body 16 and they are accommodated in the case 1
while keeping this holding state. When the frame body 16 is pressed against the face
side opening 1a of the case 1 by the case back 6, the positioning frame 8 and the
dial 4 contact a peripheral sidewall 17 of the face side opening 1a of the case 1.
[0152] If the state where the dial 4 and the positioning frame 8 contact the peripheral
sidewall 17 of the case 1 is maintained, there is no likelihood of breakage of the
dial 4 and the positioning frame 8 caused by striking against the peripheral sidewall
17 even if they receive a large impact loading, thereby enhancing the impact tolerance.
[0153] As compared with the case where the projecting parts 4a and 4b shown in Fig. 2 are
formed on the dial 4 made of a fragile material such as ceramic and they are engaged
in the recessed parts 8c and 8d of the positioning frame 8, the recessed parts 12
and 13 are provided on the dial 4 so that the stress concentration occurs in the projecting
parts 4a and 4b, thereby preventing the dial 4 from being cracked and broken, and
further enhancing the impact tolerance.
[0154] Fig. 12 is a cross sectional view of a modification of the third embodiment.
[0155] In this embodiment, only the dial 4 contacts the peripheral sidewall 17 of the face
side opening 1a of the case 1, and a gap is defined between the positioning frame
8 and the peripheral sidewall 17. That is, the height of the positioning frame 8 is
set to be lower than that of the dial 4.
[0156] When the positioning frame 8 is made of a metallic material which is less fragile,
the same impact tolerance can be obtained in the same way as the third embodiment.
[0157] Fig. 13 is a cross sectional view of another modification of the third embodiment.
[0158] In this modification, an elastic member 18 is provided between the dial 4, the positioning
frame 8 and the solar battery 3. The elastic member 18 is made of rubber or synthetic
resin respectively having elasticity, and it has a thickness ranging from 50 to 100
µm. Since the elastic member 18 is interposed as set forth above, it is possible to
prevent a mechanical breakage caused by the striking of the dial 4 and the positioning
frame 8 against the light receiving surface 3a of the solar battery 3, and possible
to enhance the impact tolerance of the dial 4 owing to an impact or shock absorbing
effect by the elastic member 18.
[0159] The elastic member 18 may be provided between the dial 4, the positioning frame 8
and the solar battery 3 in the structure of the modification in Fig. 12.
[0160] As a result of impact tests for the solar battery powered watch having the structures
shown in Figs. 10, 11 and 12 which test corresponds to a free drop of watch from the
height of 1 m, the dial 4 is not at all broken.
[0161] In the positioning structure of the dial 4 shown in Fig. 11, the recessed parts 12
and 13, and the projecting parts 14 and 15 may be provided appropriately at three
points or more on the dial 4.
(Fourth Embodiment)
[0162] A solar battery powered watch according to a fourth embodiment of this invention
will be now described with reference to Figs. 14 and 15. Fig. 14 is a cross sectional
view of the solar battery powered watch of the fourth embodiment, and Fig. 15 is a
plan view of a covering member which is one of the constituents of the solar battery
powered watch and is used as a dial.
[0163] In Figs 14 and 15, constituents which are the same as or correspond to those in Figs.
1 and 2 are denoted by the same numerals, and the explanations thereof are omitted.
[0164] The glass 5 is attached to the face side opening 1a of the case 1 by way of a first
packing 20 made of a resin material, thereby forming an airtight structure to prevent
the entry of dust, moisture and the like to the solar battery powered watch.
[0165] The ornamental frame 21 is fixed to the inner side of the case 1 along the periphery
of the face side opening 1a of the case 1. The ornamental frame 21 covers the periphery
(rough surface) of the face side opening 1a of the case 1 which is a forged product,
and it has been conventionally employed for enhancing the ornamental value of the
watch. The ornamental frame 21 is generally made of a material which is different
from that of the case 1, and it has a mirror-finished surface formed by grinding the
surface thereof by a diamond tool.
[0166] Further, a groove is defined in the case 1 at the surface to which the case back
6 is attached, and a second packing 22 made of a rubber material is provided in the
groove. The case back 6 is mounted to the case 1 by way of the second packing 22,
thereby forming an airtight structure to prevent the entry of dust, moisture and the
like to the solar battery powered watch.
[0167] The movement 2, the dial 4 and the solar battery 3 are accommodated in the case 1
in a state where they are held by a casing frame 23 at the outer peripheries thereof.
The casing frame 23 is made of a resin material. A stage part 23a having the same
dimensions as the thickness of dial 4 is formed on the stage part 23a at the front
end thereof, wherein the dial 4 which is engaged in the positioning frame 8 (see Fig.
15) is accommodated in the stage part 23a so as to be dropped therein. Accordingly,
the front end of the casing frame 23 is flush with the surface of the dial 4.
[0168] An accommodation part 23b of the solar battery 3 is defined in the casing frame 23
under the stage part 23a for accommodating the dial 4 therein. The solar battery 3
is arranged in the accommodation part 23b.
[0169] The lower end surface 21a of the ornamental frame 21 protrudes under (the back side
of) the peripheral sidewall 17 of the face side opening la of the case 1 shown in
Fig. 14. Accordingly, the casing frame 23 for holding the dial 4, the solar battery
3 and the movement 2 is pressed by the case back 6 from the back side, the inner face
of the periphery of the dial 4 is brought into contact with the ornamental frame 21.
[0170] At this time, if the lower end surface 21a of the ornamental frame 21 is positioned
under (the back side of) a curved part 25 which is formed by a forging process on
the base of the peripheral sidewall 17, the casing frame 23 is not liable to interfere
with the curved part 25. When the dial 4 contacts the ornamental frame 21, a gap 24
is defined between the back of the peripheral sidewall 17 of the case 1 and the dial
4. Since the curved part with a thickness of about 0.2 mm is formed with corners in
a general forging process, if the gap 24 having a length of about 0.2 mm is defined
between the back of the peripheral sidewall 17 of the case 1 and the dial 4, it is
possible to prevent the interference between the curved part 25 and the casing frame
23.
[0171] Since the projecting parts 4a and 4b formed at the periphery of the dial 4 (see Fig.
15) are disposed in the gap 24, even if impact loading is applied from the outside,
the projecting parts 4a and 4b do not strike against the case 1. Accordingly, there
is no likelihood of occurrence of stress concentration in the projecting parts 4a
and 4b, thereby preventing the dial 4 from being cracked and broken, and further enhancing
the impact tolerance.
[0172] The inventors of this application fabricated 10 solar battery powered watches each
having the structure shown in Fig. 14, and these solar battery powered watches are
subject to a hammer impact test corresponding to a free drop from the height of 1
m. As a result of the test, no dial 4 was broken.
[0173] Fig. 16 is a view for explaining a modification of the fourth embodiment.
[0174] The solar battery powered watch shown in Fig. 16 has an intermediate member 26 made
of a resin material between the movement 2 and the case back 6. The intermediate member
26 may be fixed to the case back 6. It is preferable that the inner diameter of the
intermediate member 26 is substantially the same as that of the ornamental frame 21,
and the intermediate member 26 is opposite to the ornamental frame. With such an arrangement,
a repulsive force which is generated between the ornamental frame 21 and the intermediate
member 26 does not act on the constituents such as the movement 2, the solar battery
3 and the dial 4 as a shearing force.
[0175] Meanwhile, when the case back 6 is attached to the case 1, it is structured not to
define a gap between the intermediate member 26 and the movement 2. In order to structure
it as such, the thickness of the intermediate member 26 may be greater than the length
of the gap between the movement 2 and the case back 6 by the length ranging from about
0.5 mm to 0.1 mm.
[0176] When the case back 6 is attached to the case 1, the dial 4 is brought into contact
with and fixed to the ornamental frame 21 owing to the pressing force from the intermediate
member 26. With the provision of the intermediate member 26, when solar battery powered
watch receives the impact loading, the intermediate member 26 operates to suppress
the deformation of the dial 4 to surely prevent the breakage of the dial 4.
[0177] Fig. 17 is a view for explaining another modification of the fourth embodiment.
[0178] The solar battery powered watch shown in Fig. 17 has an elastic member 27 such as
rubber which is interposed between the casing frame 23 and the case back 6. The elastic
member 27 may be fixed to the lower end surface of the casing frame 23. When the case
back 6 is mounted to the case 1, the case back 6 is structured to press the elastic
member 27, and the dial 4 is brought into contact with the ornamental frame 21 without
generating a gap there between by the pressing force from the case back 6.
[0179] The operation of the elastic member 27 will be now described. That is, if the solar
battery powered watch has not the elastic member 27, when it receives impact loading
from the outside repetitively, the case back 6 made of the metallic material transmits
the impact loading to the casing frame 23 repetitively. The casing frame 23 is made
of a resin material as set forth above. Accordingly, the casing frame 23 is deformed
when it receives the impact loading repetitively, so that a gap is defined between
the casing frame 23 and the case back 6.
[0180] As a result, a gap is also defined between the surface of the dial 4 and the case
1 and between the case 1 and the ornamental frame 21. When the solar battery powered
watch receives impact loading, the dial 4 strikes strong against the ornamental frame
21 so that the dial 4 is broken.
[0181] The elastic member 27 is provided as an impact absorbing member between the casing
frame 23 and the case back 6 in order to prevent the deformation of the casing frame
23 caused by repetitive impact loading. When the elastic member 27 is provided, the
deformation of the casing frame 23 owing to the impact loading is prevented, thereby
preventing the breakage of the dial 4.
[0182] Although not shown in Fig. 17, the intermediate member 26 shown in Fig. 16 may be
also provided between the case back 6 and the movement 2.
[0183] Fig. 18 is a view for explaining still another modification of the fourth embodiment.
[0184] The feature of the solar battery powered watch in Fig. 18 resides in a positioning
fixed means for positioning and fixing the dial 4 relative to the movement 2. That
is, in this modification, the projecting parts 4a and 4b are not formed on the dial
4 shown in Fig. 15, but a plurality of (e.g., two) through holes are bored in the
dial 4 at a region contacting the ornamental frame 21 and end portions of fixed pins
28 are engaged in the through holes. The dial 4 is positioned relative to the movement
2 using the fixed pins 28.
[0185] Through holes through which the fixed pins 28 penetrate are bored in the solar battery
3, and positioning holes (fixing means) in which the fixed pins 28 are engaged are
bored in the movement 2. The fixed pins 28 are engaged in the positioning holes of
the movement 2 by way of the through holes of the solar battery 3, so that the dial
4 are positioned relative to and fixed to the movement 2, and the solar battery 3
is also positioned relative to the movement 2.
[0186] Although not shown in Fig. 18, the intermediate member 26 shown in Fig. 16 may be
provided between the movement 2 and the case back 6. Further, the elastic member 27
shown in Fig. 17 may be provided between the case back 6 and the casing frame 23.
Still further, the intermediate member 26 and the elastic member 27 are respectively
provided.
[0187] Although the size of the dial 4 is substantially the same as that of the movement
2 in Fig. 18, these sizes are not necessarily the same. That is, the stage part 23a
is formed on the casing frame 23 and the dial 4 is accommodated and disposed in the
stage part 23a shown in Fig. 14.
[0188] Although the size of the dial 4 is substantially the same as that of the solar battery
3 in Fig. 18, the solar battery 3 may be made smaller than the dial 4 and it may be
accommodated and disposed in the accommodation part 23b (see Fig. 14) of the casing
frame 23. In this case, it is preferable that the dimensions of the solar battery
3 are substantially the same as or slightly greater than outer dimensions of the ornamental
frame 21.
[0189] That is, when the solar battery powered watch receives the impact loading from the
outside, the impact loading is transmitted to the dial 4 by way of the movement 2.
At this time, when the dimensions of the solar battery 3 are smaller than the outer
dimensions of the ornamental frame 21, a shearing force is applied to the dial 4 so
that the dial 4 is liable to be broken. Accordingly, if the dimensions of the solar
battery 3 are made larger than the outer dimensions of the ornamental frame 21, such
a shearing force does not apply to the dial 4, thereby preventing the breakage of
the dial 4.
[0190] As the fixed means for fixing the dial 4 and the solar battery 3 relative to the
movement 2, it is possible to employ means other than the fixed pins 28 for adhering
respective constituents, for example, an adhesive. In case that the solar battery
3 and the dial 4 are adhered to each other, it is possible to suppress the lowering
of generated electric power of the solar battery 3 if only the periphery of the solar
battery 3 is adhered by the adhesive.
[0191] In the aforementioned embodiments, the case 1 and the ornamental frame 21 are respectively
formed of different members but they may as well be integrally formed.
CAPABILITY OF EXPLOITATION IN INDUSTRY
[0192] This invention can be utilized for various watches incorporating a solar battery
therein as a power supply, thereby enhancing an ornamental value thereof and also
enhancing light transmittance relative to the solar battery.