Stock material or miscellaneous articles – Light transmissive sheets – with gas space therebetween and...
Reexamination Certificate
2001-09-18
2004-09-21
Loney, Donald J. (Department: 1772)
Stock material or miscellaneous articles
Light transmissive sheets, with gas space therebetween and...
C428S077000, C428S078000, C052S786100, C156S073500, C156S073600, C156S109000
Reexamination Certificate
active
06793990
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a glass panel including a pair of glass sheets with a gap being formed between opposing faces of the sheets and the gap being hermetically sealed by peripheral edges of the glass sheets. The invention relates also to a method of manufacturing such glass panel.
BACKGROUND ART
For a double glazing or glass panel having peripheral edge thereof sealed, it has been conventionally proposed to bond and seal the entire peripheral edges of the opposing faces of the pair of glass sheets by using metal material such as solder. However, the glass sheets generally do not directly wet with the molten metal material. For this reason, it has been a conventional practice to form, in advance, a metallic coating film having good wettability with the solder at bonding portions on the opposing faces of the pair of glass sheets and then to bond the solder with the glass sheets via such metallic coating film. As such soldering method and the manufacturing method of a bonded assembly of glass sheets utilizing the soldering method, various types of method are known.
For instance, Japanese laid-open patent publication (Kokai) No. Sho. 53-145833 discloses a multiple glazing including two or more glass sheets having metallized edge portions, metallized with e.g. copper coating, thereof soldered.
Further, Japanese laid-open patent publication (Kokai) No. Sho. 54-81324 discloses art of assembling respective components for forming an enclosure in hermetic manner, with at least one of the components being glass. In this, there is disclosed a method of bonding, by means of solder, portions to be bonded which portions have been metallized in advance by e.g. vapor evaporation process.
Still further, Japanese patent publication (Kokoku) No. Hei. 1-58065 discloses, as a high-airtight soldering multiple layer, a multiple layer consisting of a bottom layer, a middle layer and a top layer, which comprises Cu and NiCr films or the like formed on a surface of a base material such as glass.
Further, as the soldering methods, such methods have been attempted as inserting a metal element as an intermediate element between glass substrates having metallic coating films at bonding portions thereof and then bonding these glass substrates and the metallic element by means of solder or as coating solder in advance at the peripheral edges of the glass substrates having metallic coatings and then heating under pressure the substrates so as to bond them together. In either case, the solder employed contains a large amount of lead.
However, with those methods disclosed by the prior art, it has been difficult to obtain hermetically sealed glass panels with good reproducibility. Namely, with such glass panels soldered via the metallic coating films formed at the bonding portions of the glass sheets, sufficient mechanical strength can be obtained, but they are unsatisfactory in the respect of the hermetic seal. This is because of the presence of different material interfaces not only between the respective glass sheets and the solder, but also between the solder and the metal coating film as well as between the metal coating film and each glass sheet. The presence of such interfaces is very disadvantageous for hermetic seal.
Further, in actual manufacturing process, there tend to occur irregularities in the fused condition of the solder at the time of bonding. Because of this, it sometimes happens that the base soldering metallic coating film may be dissolved in the solder completely, thus resulting in insufficient bonding between the solder and the respective glass sheets or that oxidation may develop before the solder can wet the glass sheets, thus leading to deterioration in the hermetic seal.
Also, in the case of the method of bonding glass sheets pre-coated with solder, it is difficult to completely eliminate, at the time of bonding, any oxide dross present originally on the solder coating surface so as to preclude even microscopic inclusions thereon. For this reason, the bonding would be poor in terms of hermetic seal and unsatisfactory especially as vacuum seal.
In addition to the above, if solder with high lead content is employed, the lead may be eluted from the sealed portion of the glass panel when the panel is exposed under such environment as exposure to acid rain, so that there is the possibility of giving adverse effect to the environments.
As described above, the prior art has taught no specific requirements regarding the bonding condition between the glass sheets and the metal required for providing hermetic seal. In particular, it has been practically difficult to manufacture a relatively large glass panel such as one for use in a windowpane in a building. The present invention has been made to solve such problems. Its object is to provide a glass panel including a pair of glass sheets having their peripheral edges sealed in hermetic manner. Another object is provide a glass panel which is free from elution of lead, thus giving no adverse effect to the environments.
DISCLOSURE OF THE INVENTION
The characterizing features of a glass panel and its manufacturing method are as follows.
A glass panel, as shown in
FIGS. 2 and 3
, includes a pair of glass sheets disposed in a spaced relationship with each other with forming a gap therebetween, peripheral edges of the glass sheets being bonded directly by a single metal material for sealing the gap hermetically, characterized in that the panel satisfies the following relationship:
100≦
T
L
≦(
T
S
−100)
where T
L
is the liquidus temperature (° C.) of the metal material and T
S
is the strain point (° C.) of the glass sheets.
As is the case with the prior art described hereinbefore, when soldering metallic coating films are formed in advance on the peripheral edge of the pair of glass sheet and then metal material is applied between these metallic coating films, microscopic gaps which can serve as passages for gas molecules tend to be formed at such different material interfaces between the glass sheet surface and the metallic coating film and between the metallic coating film and the metal material.
On the other hand, according to the above construction of the invention, the bonding to the glass sheets employs a single metal material without using any soldering metallic film coatings. Therefore, it is possible to maintain air-tightness at the peripheral edges of the glass sheets.
In the above, what is referred to as “direct bonding between the glass sheets and the metal material” as used in the concept of the present invention means that the only different material interface present is the interface between each glass sheet and the metal material. And, the term: “single metal material” refers to a single element metal or an alloy having a certain composition to be used alone between the pair of glass sheets. For instance, sealing by using two or more kinds of solder having different compositions from each other is obviously excluded from the scope of the invention. Also, a condition of any other substance than the metal material being present at the bonding portion is contrary to the concept of the invention. Namely, when solder-coated glass sheets are bonded by heating with each other, the inclusions originated from the oxides formed on the raw solder material is contained within the solder, tending to result in reduction in the air-tightness. Further, the residual substance such as flux commonly employed for preventing oxidation of solder must not be present at the bonding portions since it deteriorates the air-tightness. That is to say, the conventional method involving the preliminary formation of the metal coating film for solder welding and a glass panel obtained by such method are out of the scope of the present invention.
With the bonding technique of coating the glass sheet surfaces with solder in advance and then boding the sheets face to face, the oxides on each solder surface will remain to form a different material interface. Therefore, such technique too is out of the scope of the present inventio
Domi Shinjiro
Nakagaki Shigeki
Sakaguchi Koichi
Suganuma Katsuaki
Loney Donald J.
Nippon Sheet Glass Co. Ltd.
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