Batteries: thermoelectric and photoelectric – Photoelectric – Cells
Reexamination Certificate
2000-05-26
2002-03-26
Diamond, Alan (Department: 1753)
Batteries: thermoelectric and photoelectric
Photoelectric
Cells
C136S244000, C136S251000, C257S432000, C257S434000, C428S432000, C428S326000, C428S142000, C428S141000, C428S702000, C428S701000, C052S786100, C052S786130, C052S479000
Reexamination Certificate
active
06362414
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a transparent layered product including a glass sheet and a coating film with a rough surface and a glass article using the same (for example, a photoelectric conversion device, a multiple-glazing unit, or the like).
BACKGROUND OF THE INVENTION
A transparent layered product in which a thin film such as a tin oxide film or the like is formed on a glass sheet has been used widely for a thin film photoelectric conversion device (a thin film solar cell), heat-reflecting glass, or the like. For example, JP 7-29402 B describes heat-reflecting glass formed by stacking a silicon film, a silicon oxide film, and a tin oxide film on a glass sheet in this order.
Tin oxide in a film formed by pyrolysis on a high-temperature substrate becomes a polycrystalline film. The polycrystalline product of tin oxide has a surface with roughness caused by the growth of crystal grains according to the increase in film thickness. In a thin film photoelectric conversion device, the surface roughness of a tin oxide film as a transparent electrode enables photovoltaic characteristics to be improved due to a light trapping effect.
For example, JP 61-288473 A discloses a thin film photoelectric conversion device including a tin oxide film having a rough surface including convex portions with heights in the range between 100 and 500 nm and intervals between respective convex portions in the range between 200 and 1000 nm. The rough surface is formed by etching after film formation.
Further, JP 2-503615 A discloses a substrate for a thin film photoelectric conversion device including a tin oxide film having a surface provided with convex portions with diameters in the range between 0.1 and 0.3 &mgr;m and the ratio of height/diameter in the range between 0.7 and 1.2. In addition, JP 2-503615 A also discloses a chemical vapor deposition method (a CVD method) using a mixed gas containing tin tetrachloride, water vapor, methyl alcohol, nitrogen and the like, which is carried out on a precut glass sheet, as a method of manufacturing a tin oxide film.
JP 4-133360 A discloses a substrate for a thin film photoelectric conversion device including a tin oxide film having a surface with pyramidal convex portions with heights in the range between 100 and 300 nm and angles with respect to the normal line of the principal plane of the substrate in the range between 30° and 60°. Similarly, JP 4-133360 A also discloses a CVD method using a mixed gas containing tin tetrachloride, oxygen, nitrogen and the like, which is carried out on a glass sheet with a temperature in the range between 350 and 500° C., as a method of manufacturing a tin oxide film.
Besides the tin oxide film, coating films formed of zinc oxide, ITO (indium tin oxide), titanium oxide, silicon oxide or the like also are formed on a glass sheet to add various functions. These coating films are formed on a glass sheet as, for example, a reflection-suppression film, an electromagnetic shielding film, an antifouling film, a low-emissivity film (Low-E film), or as a component thereof, in addition to a transparent conductive film and a heat reflecting film.
As described above, when a transparent layered product is obtained by forming a crystalline or amorphous coating film for adding various functions to a glass sheet, the light reflectance may be higher than that required in some cases. In addition, for example, when the transparent layered product is used as a substrate for a photoelectric conversion device or reflection-suppression glass, a lower reflectance is preferable. Depending on the intended use, the coloring of reflected light due to the formation of the coating film may be intended to be suppressed to a degree causing no harm to the desired appearance in some cases.
Judging from the fact that a porous surface has a refractive index distribution in the depth direction, it is conceivable that a transition layer in which the refractive index varies continuously is present at the surface of a coating film such as a tin oxide film or the like. This transition layer can affect reflected light from the transparent layered product. Conventionally, particularly in the field of photoelectric conversion devices, the heights and intervals of convex portions of the rough surface of a tin oxide film have been adjusted. Conventionally, however, attention merely has been paid to the physical shape and size of convex or concave portions of the rough surface. The refractive index distribution in the transition layer produced at the surface of a coating film does not depend only on the shape and size of the individual convex or concave portions of the rough surface but also is affected by the distribution of them. Therefore, the refractive index distribution in the transition layer should not be evaluated based on observation of the rough surface in a very limited region by an electron microscope and is required to be evaluated based on optical measurement.
SUMMARY OF THE INVENTION
It is an object of the present invention that in a transparent layered product including a glass sheet and a coating film exhibiting various functions, the reflectance of light entering the transparent layered product is decreased by suitably controlling the refractive index distribution in a transition layer at the surface of the coating film. Further, another object of the present invention is to provide a glass article using this transparent layered product, particularly a multiple-glazing unit and a photoelectric conversion device such as a photovoltaic device.
The present inventors found that surprisingly, the aforementioned objects were able to be achieved by controlling the pattern of the variation in refractive index in a thickness direction in a transition layer present at the surface of the coating film.
The transparent layered product of the present invention includes a glass sheet and a coating film having a surface with roughness, which is formed on the glass sheet, and a transition layer in which the refractive index varies continuously in its thickness direction is present at the surface of the coating film. The variation in refractive index in the transition layer is indicated by a convex curve over the whole region of the transition layer, when the variation is shown on a plane defined by a horizontal axis indicating the refractive index and a vertical axis indicating the thickness direction of the transition layer, with the glass sheet positioned on a lower side.
When the coating film is formed as an outermost layer, the refractive index in the transition layer varies continuously in its thickness direction to approach the refractive index of air (
1
) from the refractive index of the coating film, in the direction of the outside air. On the other hand, when another thin film is further formed on the coating film having a surface with roughness, the refractive index in the transition layer approaches the refractive index of the another thin film while varying continuously in its thickness direction. In this case, it is preferable that the refractive index varies continuously from a refractive index n
1
of the coating film to a refractive index n
2
of the thin film formed thereon so that the variation in refractive index is indicated by a convex locus (curve) over the whole region when being shown on a plane. The magnitude correlation between the refractive index n
1
and the refractive index n
2
is not particularly limited.
In the transparent layered product, it is preferable that the coating film is a crystalline coating film. It also is preferable that the roughness is caused by crystal grains in the crystalline coating film. In this connection, the crystalline coating film may contain amorphous portions regionally, and a film with a crystalline fraction in volume of at least 50% as a whole is taken as corresponding to a “crystalline” film.
In the transparent layered product, it is preferable that the crystalline coating film contains, as a main component, at least one selected from tin oxide, zinc oxide, indium oxide,
Fujisawa Akira
Hirata Masahiro
Nara Masatoshi
Diamond Alan
Kaneka Corporation
Merchant & Gould
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