GB2186769A

GB2186769A - Conductive glass plate

Info

Publication number: GB2186769A
Application number: GB08630807A
Authority: GB
Inventors: Jun Hasegawa; Jun Kawaguchi; Takashi Muromachi; Kaoru Sakurai
Original assignee: Nippon Sheet Glass Co Ltd
Current assignee: Nippon Sheet Glass Co Ltd
Priority date: 1985-12-26
Filing date: 1986-12-23
Publication date: 1987-08-19
Also published as: IT8622869A0; KR870005921A; FR2592544A1; IT1213578B; GB8630807D0; DE3644297A1

Abstract

A glass plate 31 has a transparent conductive film 32 on one face. A current is not supplied to the entire surface of a transparent conductive film 32 but limited by slits 34 in the film 32, so that the current is supplied along a limited current path. By attaining a predetermined current density only in a predetermined portion of the transparent conductive film, even if power consumption per unit time is small, thawing, defrosting or the like in the predetermined portion can be immediately performed. Bus bars 33a, 33b, 33c and 33d serve as terminals for voltage applied to the film 32. The pattern of current flow can be altered by altering the respective polarities of the bus bars 33. Slits 34 may be formed which completely surround areas of the film 32 which are then only heated by conduction. <IMAGE>

Description

SPECIFICATION Conductive glass plate BACKGROUND OF THE INVENTION Field ofthe Invention: The present invention relates to a conductive glass plate suitably used as window glass of an automobile or the like and electrically heated for thawing, defrosting orthe like.

Description of the Prior Art: Fig. 1 shows a typical conventional conductive glass plate. In a conductive glass plate 10, a transparent conductive film 12 containing tin oxide as a major constituent is formed on one surface of a glass plate 11,and bus bars 13a and 13b are formed along a pair of opposite edges on the same surface.

In the conductive glass plate 10, when a voltage is applied across the bus bars 1 3a and 1 3b to perform thawing, defrosting or the like, a current is supplied to substantially the entire surface ofthe transparent conductive film 12.

The electric resistance ofthe transparent conductive film 12 between the bus bars 13a and 13b is as large as about 2.5 n. Forthis reason, in order to supply a current of, e.g., 20 Ato the entire surface of the transparent conductive film 12, a relatively high voltage of 50 V is required. Therefore, high power consumption is required to perform thawing, defrosting or the like. And, if power consumption per unit time is reduced, high-speed thawing, defrosting or the like cannot be achieved.

If the transparent conductive film 12 has a nonuniform thickness, its electrical resistance has a nonuniform distribution. When a current is supplied to substantially the entire surface of the transparent conductive film 12, the resultant current density becomes nonuniform, as indicated by broken lines in Fig. 1. As a result, a portion having a high current density is abnormally heated to degradethetranspa- rent conductive film 12.

SUMMARY OF THE INVENTION A conductive glass plate according to the present invention is designed so that a current is not supplied to the entire surface of a transparent conductive film, and flow paths of the current are limited by slits.

A predetermined current density can be obtained for predetermined portions ofthetransparent conduc- tive film, and thawing, defrosting orthe like can be quickly performed for the predetermined portions even if power consumption per unit time is low.

Alternatively, a comb-like current path is used to prevent variations in current density and hence abnormal heating. As a result, degradation orthe like ofthe transparent conductive film can be prevented.

Furthermore, a proper slit pattern is selected to control the current densities of different areas ofthe glass plate, and the areas have a priority order four thawing, defrosting or the like.

Since a slitwidth can be 0.1 mm or less, the outer appearance ofthe transparent conductive film is not impaired, and the driver's field of view can be guaranteed. In addition, this arrangement also serves to reflect solar heat.

BRIEF DESCRIPTION OF THE DRAWINGS Fig. is front view of a conventional example; and Figs. 2to 1 8B are front views showing first to seventeenth embodiments ofthe present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A th ree-layered transparent conductive film 32 is formed by sputtering orthe like on one surface of a glass plate 31 in each of conductive glass plates 21 to 29 according to first to ninth embodiments ofthe present invention. The three-layered structure comprises a MO,-Ag-MO, structure (wherein MOx = SnO2, ZnO, ln203, ITO, Ti02, orthe like). Bus bars 33a and 33b are formed along a pair of opposite edges ofthe glass plate 31 on the same surface in each of the plates 21 to 29, exceptthatthe bus bars 33a and 33b in the eighth embodiment of Fig. 9 extend up to half the entire sides of the glass plate 31.

Slits 34 are formed in each transparent conductive film 32 by mechanical cutting (a width is 20to40 pm) by a blade, laser cutting (a width is several micrometers) or the like.

The slits 34 have different patterns, as shown in Figs. 2 to 10. In any case, the slits 34 include length components of longitudinal directions in direction wherein the bus bars 33a and 33b extend.

In each of the conductive glass plates 21 to 28, when a voltage is applied between the bus bars 33a and 33b, a current is not supplied across the slits 34. Since the slits 34 are formed such that the slits 34 include the length components of longitudinal directions in direc tionwhereinthe bus bars 33a and 33b extend, nonconductive portions are formed by the slits 34, so that a current is supplied in conductive portions between the nonconductive portions.

A ratio of a conductive portion width to a nonconductive portion width falls within the range between 1 : 2 and 1 5 in 1:5 inthefirstto ninth em embodiments. Power required to obtain the same current density ofthe conductive portion as in the conventional case is reduced to 1/2 to 1/5. Thawing, defrosting or the like in the nonconductive portions are performed by heat conduction from the conductive portions.

If the absolute width of each conductive portion is excessively reduced even ifthe ratio of the conductive portion width to the nonconductive portion width falls within the range between 1: 2 and 1: 5, that is, if the number ofslits 34 is excessively large, the field of view maybe interfered by these many slits 34. Forthis reason, the conductive portion width is setto be about lotto 50 mm in the firstto ninth embodiments.

When the width of the slit 34 exceeds 100 pom, the slit 34 becomes visually conspicuous. When the width falls within the range between 50 pom and 100 pom, the slit 34 is not conspicuous but can be identified by a naked eye. However, when the width falls within the range between 20 pom and 50 pm, the slit 34 can rarely be identified by the naked eye. When the width falls within the range between 1 pom and 201lem, the slit 34 cannot be identified by the naked eye at all. However, if the width is 1 pm or less, the slit 34 cannot be satisfactorily formed. In other words, the slit forming process becomes unstable, and complete slits cannot be formed.

The width ofthe slit 34 must be 100 pm or less and preferably falls within the range between several micrometers and 50 us. Thus the widths in the first to ninth embodiments are defined as described above.

The transparent conductive film 32 need not be a multi-layered film, but may be a single layer of SnO2, In203 orthe like.

Two slits 34 are formed by mechanical cutting (a width is 20 um to 40 um) using a blade, laser cutting (a width is several micrometers) orthe like in a transparent conductive film 32 on a conductiveglass plate 41 according to a tenth embodiment in Fig. 1 1A and 11 B.

Thetwoslits34verticallyextendfrom one side aboutthe center ofthetransparent conductive film 32.

On the surface ofthe glass plate 41 with the transparent conductive film 32, bus bars 33a, 33b, and 33e extend along one side with slits so as to interpose the slits 34therebetween. A bus bar 33d extends along substantially the entire side opposite to one side with slits.

In the conductive glass plate 41, a voltage is applied to the bus bars 33a to 33csuch that the bus bars 33a and 33b serve as anodes and the bus bar 33c serves as a cathode, and thatthe bus bar 33d is kept deenergised.

In this state, a currenttends to be supplied from the bars 33a and 33b to the bus bar 33c. However, the current is not supplied to cross the slits 34. Therefore, the current detours the slits 34, as indicated by broken lines in Fig. 11A.

Forthis reason, the current density nearthedistal ends of the slits 34 is higherthan thatatthe other portions. Even if a voltage appled to the bus bars 33a to 33c is not so high, thawing, defrosting or the like are immediately performed near the distal ends ofthe slits 34.

When thawing, defrosting orthe like near the distal ends of the slits-34are completed, the polarity ofthe voltage applied to the bus bar33c is inverted to the positive polarity, and atthe same time a negative voltage is applied to the bus bar33d, as shown in Fig.

11B.

A current is uniformly supplied to substantially the entire surface ofthetransparent conductive film 32, as indicated by dotted lines in Fig. 11 B. Thawing, defrosting orthe like are slowly performed for the entire surface ofthe transparent conductive film 32.

A conductive glass plate 42 according to an eleventh embodiment of Figs. 1 2A and 1 2B is substantiallythe sameasthatofthetenth embodiment, exceptthata pairofslits 34 extend from opposite sides of the transparent conductive film 32 so as to come close to each other and bus bars 33a and 33b and bus bars33c and 33d areformed at opposite sides so asto interpose the corresponding slits 34.

As shown in Fig. 12A, in the conductive glass plate 42, a voltage is appliedtothe bus bars 33a to 33d such thatthe bus bars 33a and 33c serve as anodes and the bus bars 33b and 33d serve as cathodes. In this case, thawing, defrosting orthe like are performed at a portion between the distal ends ofthe slits 34, i.e., a portion having a high current density.

Thereafter, as shown in Fig. 1 2B, the polarity ofthe bus bars 33b is changed to the positive polarity, and the polarity ofthe bus bar33c is changed to the negative polarity to peform thawing, defrosting or the like substantially on the entire surface ofthe transpa rent conductive film 32.

Aconductive glass plate 43 in a twelth embodiment of Figs. 13Aand 13B is substantiallythe same as the conductive glass plate 41 of the tenth embodiment, exceptthat slits 34 extend from two adjacent corners toward the center of a transparent conductive film 32 and that bus bars 33a to 33d respectively extend along foursidesofthetransparentconductivefilm 32.

In this conductive glass plate 43, a voltage is selectively applied to the bus bars 33a to 33d such that the bus bar33a servesas an anode andthebus bars 33b and 33c serve as cathodes to perform thawing, frosting or the like ata portion near the distal ends of the slits 34, i.e., a portion having a high current density, as shown in Fig. 13A.

Thereafter, as shown in Fig. 13B, the bus bars 33b and 33e are deenergised, and at the sametime a negative voltage is applied to the bus bar 33d to perform thawing, defrosting or the like for substantialliy the entire surface ofthe transparent conductive film 32.

Three slits 34 equidistantly extend along a direction perpendicularto a pair of opposite sides of a transpa rent conductive film 32 in a conductive glass plate 51 according to a thirteenth embodiment of Fig.

14. These slits 34 are formed by a mechanical cutting (a width is 20 to 40 pm) using a blade, laser cutting (a width is several micrometers), or the like.

The transparent conductive film 32 is divided into four equal areas 32a to 32d bythe slits 34. Bus bars 33a and 33b, 33c and 33d, 33e and 33f, and 33g and 33h extend along pairs of opposite sides ofthe areas 32a to 33d, respectively.

In the conductive glass plate 51 having the construction described above, a voltage is applied atfirstto onlythe bus bars 33a and 33b, and the busbars 33c to 33h are kept deenergised. A current is supplied between the bus bars 33a and 33b but is not supplied to cross the slit 34. As a result, the current is supplied to onlythe area 32a.

Even if a voltage applied to the bus bars 33a and 33b does not have a large magnitude, a predetermined currentdensity can be obtained within the area 32a. In otherwords, even if power consumption per unit time is not so large, thawing, defrosting orthe like are performed for at least the area 32a. When thawing, defrosting orthe like within the area 32a are completed, a voltage is sequentially applied between the bus bars 33c and 33d, 33e and 33f, and 33g to 33h to energise the areas 32b, 32c, and 32d so as to perform independent thawing, defrosting or the like in these areas.

However, thawing, defrosting or the like need not be sequentially performed in the order of the areas 32a to 32d. If the amount of ice orfrost attached to the conductive glass plate 51 is small,the areas 32a to 32d may be simultaneously energised.

Aconductive glass plate 52 according to a four teenth embodiment of Fig. 15 is substantialiythesame as the conductive glass plate 51 of the thirteenth embodiment, except that in addition to two slits 34, slits 35 including length components of longitudinal directions in direction wherein bus bars 33a to 33f extend are respectively formed within the areas 32a to 32c.

Since the slits 35 are formed so as to include length components of longitudinal directions in direction wherein the bus bars 33a to 33f extend in the conductive glass plate 52, these slits 35 define nonconductive portions, and acurrent is supplied between conductive portions defined by the nonconductive portions.

Power consumption for obtaining the same current density in the conductive portion as in the thirteenth embodiment can be reduced in the fourteenth embodiment. It should be noted that thawing, defrosting orthe like in the nonconductive portions are performed by heat conduction from the conductive portions.

Four slits 34 extend from four corners to the vicinity ofthe center of a transparent conductive film 32 in a conductive glass plate 61 according to a fifteenth embodiment of Figs. 1 6Ato 16B. These slits 34 are formed by mechanical cutting (a width is about 20 to 40 cm) using a blade, laser cutting (a width is several micrometers), orthe like.

Bus bars 33a to 33d are respectively formed along foursides on the same surface ofthe glass plate 61 with the transparent conductive film 32, except for the corners of the plate 61.

In the conductive glass plate 61, a voltage is selectively applied to the bus bars 33a to 33d such that at first the bus bar 33a serves as an anode and the bus bar 33b serves as a cathode, and that the bus bars 33c and 33d are kept deenergised, as shown in Fig. 1 6A.

In this state, a current tends to be supplied from the bus bar 33a to the bus bar 33b, but does not cross the slits 34. As indicated by broken lines in Fig. 16A,the current is supplied so as to detourthe slits 34.

Therefore, a portion defined by the distal ends ofthe slits 34, i.e., the central portion of the transparent conductive film 32 has a highest current density. Even if the voltage applied to the bus bars 33a and 33b does not have a large magnitude, thawing, defrosting or the like are immediately performed at the central portion ofthe transparent conductive film 32.

When thawing, defrosting or the like at the central portion ofthe transparent conductive film 32 are completed to a given extent, a voltage is then selectively applied to the bus bars 33a to 33d such that the bus bar33c serves as an anode and the bus bar 33d serves as a cathode, and that the bus bars 33a and 34b are deenergised, as shown in Fig. 1 6B.

As indicated by broken lines in Fig. 1 6B, the central portion of the transparent conductive film 32 has the highest current density.

When thawing, defrosting or the like at the central portion of the transparent conductive film 32 are completed,thawing, defrosting orthe like atother portions have not yet been completed although have progressed to a given extent that the driver's field of view is guaranteed. When the application of the voltagetothe bus bars 33a and 33b and bars 33c and 33d continues, thawing, defrosting orthe likethroughout the transparent conductive film 32 are completed.

A conductive glass plate 62 according to a sixteenth embodiment of Figs., 1 7A and 1 7B is substantially the same as the conductive glass plate 61 ofthe fifteenth embodiment, except that only two diagonal slits 34 are formed in a transparent conductive film 32.

In the conductive glass plate 62, a voltage is applied at first to the bus bars 33a and 33b such that the bus bar 33a serves as an anode and the bus bar 33b serves as a cathode, as shown in Fig. 17A. Thereafter, a voltage is applied to the bus bars 33c and 33d such that the bus bar33c serves as an anode and the bus bar33d serves as a cathode, as shown in Fig. 17B.

Thawing, defrosting or the like atthe central portion ofthe transparent conductive film 32 in the conductive glass plate 62 are immediately performed.These operations in other portions are also performed to a given extent within a short period oftime.

A conductive glass plate 63 according to a seventeenth embodiment of Figs. 1 8A and 1 8B is substan tiallythe same as the conductive glass plate 61 ofthe sixteenth embodiment, except that slits 34 extend from foursides to the vicinity ofthe center and L-shaped bus bars33ato33d areformed atfour corners of a transparent conductive film 32. In this case, each slit 34 in opposite pairs comes close to each other.

In the conductive glass plate 63, a voltage is applied atfirstto bus bars 33a and 33b such thatthe bus bar 33a serves as an anode and the bus bar 33b serves as a cathode, as shown in Fig. 1 8A. Thereafter, a vo Itage is applied to the bus bars 33c and 33d such thatthe bus bar33c serves as an anode and the bus bar33d serves as a cathode, as shown in Fig. 1 8B.

Thawing, defrosting or the like at the central portion ofthetransparent conductive film 32 in the conductive glass plate 63 are immediately performed, and the identical operations in other portions are performed to a given extentwithin a short period oftime.

Although the transparent conductive film 32 and the bus bars 33a to 33h are formed on one surface ofthe glass plate 31 in any embodiment described above, the transparent conductive film 32 and the bus bars 33a to 33h may be formed in a laminated glass.

Claims

1. A conductive glass plate comprising: a transparent conductive film attached to a glass plate; at least two bus bars attached to said glass plate to energise said transparent conductive film; and slits formed in said transparent conductive film to limit a current path between said bus bars.

2. A plate according to claim 1, wherein said bus bars oppose each other in a direction perpendicularto an extension direction of said bus bars, and said slits include length components of longitudinal directions in direction wherein said bus bars extend.

3. A plate according to claim 1,wherein said slits extend from edgesofsaidtransparentconductivefilm to a predetermined portion in said transparent con ductive film, and said two bus bars are independently located at two sides of each of said slits.

4. A plate according to claim 1,wherein said slits extend from edges of said transparent conductive film to a predetermined portion i n sa in saidtransparentcon- ductivefilm, said two bus bars are independently located at two sides of each of said slits, and athird bus bar is arranged to oppose at least one of said two bus bars.

5. A plate according to claim 1, wherein said slits divide said transparent conductive film into a plurality of areas, and atleasttwo bus bars are arranged in each of said plurality of areas.

6. A plate according to claim 1, wherein said slits extend from opposite edges of said transparent conductivefilmtocomecloseto each other, and a plurality of bus bars are respectively arranged along all sides of said grass plate.

7. A plate according to any one of claims 1 to 6, wherein each of said slits has a width of not more than 100calm.