Anti-fogging glass

Details Anti-fogging glass Anti-fogging glass

1999-11-08

2001-04-03

Hoang, Tu Ba (Department: 3742)

Electric heating

Heating devices

Combined with diverse-type art device

C219S541000

Reexamination Certificate

active

06211491

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an anti-fogging glass, which is designed to prevent fogging by heating the glass plate by supplying power to a heating unit formed on the surface of the glass plate.
2. Discussion of Background
As a window glass to be mounted in e.g. a rear window frame of an automobile, an anti-fogging glass having an anti-fogging function is commonly employed to secure safe visibility. Such anti-fogging glass is provided on the surface thereof with a heating unit formed by printing a conductive paste such as silver in a suitable pattern on the surface of a glass plate, followed by heating and baking it.
A conventional structure of an anti-fogging glass for an automobile, provided with a heating unit, is shown in FIG.
8
. The heating unit comprises a plurality of lines, and has heating lines (heat strips)
71
having a narrow width (from about 0.5 to 1 mm), formed to extend substantially in parallel with one another with a distance of a few tens mm in a longitudinal (transverse) direction of the anti-fogging glass and a pair of symmetric bus bars
73
having a large width formed in the vicinities of the short side edges of the anti-fogging glass in the short side direction (vertical direction) of the anti-fogging glass, to which both ends of these heating lines
71
are connected. Further, at the lower end of each bus bar
73
, a terminal
75
for connecting a power supply wire (not shown) connected to a power source of an automobile, to the bus bar
73
, is provided and fixed by e.g. solder.
When power supply to the heating lines
71
is carried out with such a conventional anti-fogging glass having the above described construction, a current obtained from the power source of an automobile is supplied to the bus bars
73
via the power supply wires and the terminals
75
and from the bus bars
73
to the respective heating lines
71
. The heating lines
71
are thereby heated, so that the glass plate
77
is heated mainly in the anti-fogging region
79
.
As described above, the anti-fogging glass is designed to remove or prevent deposition of e.g. moisture, frost or icing on the surface of a glass plate by utilizing heat generated by the heating lines
71
, thereby to secure the transparency of the glass.
SUMMARY OF THE INVENTION
With a conventional anti-fogging glass for an automobile, it is common that a terminal
75
for supplying a current is provided at a lower end portion of a bus bar, for example, because of a restriction from the design of the automobile. Further, all heating lines
71
are connected on the upper side of the glass plate than the upper side line of the terminal
75
, whereby all currents supplied to the heating lines
71
from the terminal
75
are supplied via a bus bar on the upper side of the glass plate than the upper side
75
a
of the terminal
75
. Particularly, at the bus bar portion ranging from the upper side
75
a
of the terminal
75
in
FIG. 8
to the connected point of the lowermost heating line connected to the bus bar, all currents supplied from the terminal
75
will flow, whereby the heat generation is substantial, and there has been a problem such as excessive heat generation.
Further, although it depends on the particular application, the temperature for operating the bus bars
73
without adversely affecting the interior material in the vicinity of the bus bars
73
or other constituting elements such as solder for bonding the terminals
75
, is at most a predetermined temperature (for example, at most about 75° C., and, more particularly, at most at about 70° C.). Accordingly, if there is a portion exceeding the above predetermined temperature, even if it is only a small part of the bus bars, it has been common to prevent excessive heat generation by 1) broadening the transverse width of the bus bars or 2) reducing the resistance of the bus bars by overcoating a conductive paste on the bus bar surface or by a special printing method such as partial thick printing of the bus bar portions.
However, such a method brings about an increase of the production cost due to the conductive paste or the screen printing plate and cumbersomeness of the production process due to the special printing. Further, in the method 2), bus bar bleeding or bus bar peripheral irregularities are likely to result, such being undesirable.
The present invention has been made in view of the above-mentioned situations, and it is an object of the present invention to provide an anti-fogging glass, particularly an anti-fogging glass suitable for automobiles, which is provided with a pattern of heating elements capable of preventing excessive heat generation at bus bars even if a current of the conventional level is supplied to bus bars having no special printing applied, while reducing the production cost, simplifying the production process and improving the product quality.
The present invention provides an anti-fogging glass (first aspect of the invention) having a plurality of conductive heating lines, a pair of bus bars to which both ends of the respective heating lines are connected, and terminal portions on the respective bus bars, to which terminals for supplying a current are to be connected, wherein the plurality of heating lines comprise first heating lines and second heating lines in a predetermined proportion to the plurality of heating lines, the second heating lines are connected in the vicinity of at least one terminal portion, and said vicinity of the terminal portion, in which the second heating lines are connected, is a second region other than a first region constituting a current pathway to the first heating lines, and wherein the second heating lines are connected apart from one another in the second region.
In the anti-fogging glass of the present invention, it is preferred that the second heating lines are connected in the vicinity of one terminal portion and in the vicinity of the other terminal portion, and the respective vicinities of the terminal portions, in which the second heating lines are in connected, are a second region other than a first region constituting a current pathway to the first heating lines.
In the anti-fogging glass of the present invention, the above-mentioned predetermined proportion is preferably from 10 to 50%.
In the anti-fogging glass of the present invention, the second heating lines in a predetermined proportion to the plurality of heating lines, are connected in the vicinity of at least one terminal portion, and said vicinity of the terminal portion, in which the second heating lines are connected, is a second region other than a first region constituting a current pathway to the first heating lines. Preferably, the second heating lines are connected in the vicinity of the one terminal portion and in the vicinity of the other terminal portion, and the respective vicinities of the terminal portions, in which the second heating lines are connected, is a second region other than a first region constituting a current pathway to the first heating lines. Further, the predetermined proportion is preferably from 10 to 50%. With this construction, it is possible to avoid excessive flow of a current or a concentration of current in a part of the bus bars and thereby to prevent excessive heat generation at the bus bars.
In the anti-fogging glass of the present invention, the above-mentioned second heating lines are connected apart from one another in the second region.
When a plurality of heating lines are bundled into one line (as shown in FIG.
7
), in order to suppress heat generation of the line, broadening of the transverse width or special printing such as thick printing is carried out. If the plurality of heating lines are apart from one another without being bundled into one line, the appearance of the same is good without broadening of the transverse width, and there also occurs no such problem as bleeding of the heating line by the thick printing by screen printing. Further, the thick printing is likely to undergo cracking during heating

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