Patent Publication Number: US-2019193530-A1

Title: Side glass panel

Description:
TECHNICAL FIELD 
     The present invention relates to a side glass panel. 
     BACKGROUND ART 
     On a cold day, or in cold climate areas, a windshield of an automobile sometimes fogs up, which constitutes an obstacle to driving the automobile. Therefore, various methods for removing fogginess of a windshield have been proposed. For example, Patent Literature 1 discloses arranging busbars and heating wires inside a windshield and removing fogginess by generating heat. 
     CITATION LIST 
     Patent Literature 
     Patent Literature 1: JP 2000-77173A 
     SUMMARY OF INVENTION 
     Technical Problem 
     Fogging trouble as mentioned above may occur in not only a windshield but also a side glass panel. However, a side glass panel is smaller than a windshield and thus the arrangement of the heating wires poses a problem. For example, the power consumption W of the heating wire can be determined in accordance with Equation (1) below: 
         W=V   2   R =( S/ρL ) V   2    (1)
 
     where V represents the voltage, R represents the resistance of the heating wire, S represents the cross-sectional area of the heating wire, L represents the length of the heating wire, and ρ represents the thermal conductivity. 
     Here, the higher the voltage V is, the more advantageous it is for a vehicle. For example, when the outputs of a motor and a generator are the same, the electric current can be reduced by increasing the driving voltage, and the power consumption can be thus reduced. When the electric current is reduced, the diameter of a harness for supplying power can be reduced, and therefore, the weight of the vehicle decreases correspondingly, thus making it possible to increase gas mileage. As described above, increasing the voltage V has various advantages, but the glass will break if excessive heat is generated, and therefore, it is preferable that the power consumption is as low as possible. Therefore, the heating wires need to have a long length L and should be arranged in series, but the heating wires are thin and are thus likely to break. Accordingly, in consideration of this, it is preferable to arrange the heating wires adjacent to each other. However, if the heating wires are arranged adjacent to each other, it is necessary to use sufficiently long busbars to which all the heating wires can be connected, but if such busbars are arranged, the busbars will be visible from the outside or inside of the vehicle, resulting in poor appearance. 
     The present invention was made in order to solve the aforementioned problems, and it is an object thereof to provide a side glass panel that can prevent two busbars provided therein from being visible from the inside or outside of a vehicle even when a plurality of heating wires are arranged adjacent to each other so as to connect these busbars. 
     Solution to Problem 
     A side glass panel according to the present invention includes the following aspects. 
     Aspect 1 is a side glass panel to be used in a vehicle, the side glass panel including: 
     a rectangular first glass plate having an upper side, a lower side, a front lateral side, and a rear lateral side; 
     a first busbar extending along a first side that is any one of the upper side, the lower side, the front lateral side, and the rear lateral side; 
     a second busbar extending along a second side that is any one of the upper side, the lower side, the front lateral side, and the rear lateral side; and 
     a plurality of heating wires that are arranged adjacently to each other and connect the first busbar and the second busbar, 
     wherein a blocking portion is configured to conceal the first busbar and the second busbar from an outside or inside of the vehicle. 
     It should be noted that the first side and the second side may be different sides or the same side selected from the upper side, lower side, front lateral side, and rear lateral side of the first glass plate. 
     Aspect 2 is the side glass panel according to aspect 1, wherein the blocking portion is constituted by a blocking film layered at at least one position on an outer surface or inner surface of the first glass plate. 
     Aspect 3 is the side glass panel according to aspect 1 or 2, wherein the blocking portion is constituted by a door frame to which the side glass panel is to be attached. 
     Aspect 4 is the side glass panel according to any one of aspects 1 to 3, 
     wherein the first side is the upper side of the first glass plate, and 
     the second side is the lower side of the first glass plate. 
     Aspect 5 is the side glass panel according to any one of aspects 1 to 3, 
     wherein the first side is the lower side of the first glass plate, and 
     the second side is the front lateral side or the rear lateral side of the first glass plate. 
     Aspect 6 is the side glass panel according to aspect 5, wherein the second side is the front lateral side of the first glass plate. 
     Aspect 7 is the side glass panel according to any one of aspects 1 to 3, wherein the first side and the second side are the lower side of the first glass plate, and the first busbar and the second busbar are arranged adjacent to each other on one line along the lower side of the first glass plate. 
     Aspect 8 is the side glass panel according to any one of aspects 1 to 3, 
     wherein the first side is the front lateral side of the first glass plate, and 
     the second side is the rear lateral side of the first glass. 
     Aspect 9 is the side glass panel according to aspect 4, further including at least one relay busbar that is arranged at a position different from the positions of the first busbar and the second busbar, and is located along any side of the first glass plate, 
     wherein the plurality of heating wires connect the first busbar and the second busbar via the at least one relay busbar. 
     Aspect 10 is the side glass panel according to any one of aspects 5 to 7, 
     wherein the busbars are arranged such that first end portions of the busbars are close to each other and second end portions of the busbars are away from each other, and 
     thicknesses of the plurality of heating wires increase from the first end portion side toward the second end portion side. 
     Aspect 11 is the side glass panel according to any one of aspects 5 to 7, 
     wherein at least one auxiliary heating wire is further arranged between at least one pair of the heating wires that are adjacent, and 
     one end portion of the auxiliary heating wire is connected to an intermediate portion of one of the heating wires that are adjacent, and the other end portion of the auxiliary heating wire is connected to the first busbar or the second busbar. 
     Aspect 12 is the side glass panel according to aspect 8, wherein an attachment angle is within ±30° with respect to a vertical direction. 
     Aspect 13 is the side glass panel according to any one of aspects 1 to 12, further including: a second glass plate that is arranged opposite to the first glass plate and has substantially the same shape as the first glass plate; and 
     an interlayer that is arranged between the first glass plate and the second glass plate, 
     wherein the first busbar, the second busbar, and the plurality of heating wires are arranged between the first glass plat and the second glass plate. 
     Aspect 14 is the side glass panel according to aspect 13, wherein the blocking portion is constituted by a blocking film layered at at least one position on an outer surface of the first glass plate, an inner surface of the first glass plate, an outer surface of the second glass plate, and an inner surface of the second glass plate. 
     Aspect 15 is the side glass panel according to any one of aspects 1 to 14, wherein the first busbar, the second busbar, and the plurality of heating wires are integrally formed of the same material. 
     Aspect 16 is the side glass panel according to any one of aspects 1 to 15, wherein the heating wires have a thickness of 500 μm or less. 
     Advantageous Effects of the Invention 
     With the present invention, it is possible to prevent the entire region of laminated glass having a trapezoidal shape with a longer lower side from fogging up. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a front view of a first embodiment of a side glass panel according to the present invention. 
         FIG. 2  is a cross-sectional view taken along line A-A in  FIG. 1 . 
         FIG. 3  is a front view of a second embodiment of the side glass panel according to the present invention. 
         FIG. 4  is a front view of a third embodiment of the side glass panel according to the present invention. 
         FIG. 5  is a front view of a fourth embodiment of the side glass panel according to the present invention. 
         FIG. 6  is a front view of a fifth embodiment of the side glass panel according to the present invention. 
         FIG. 7  is a front view of a sixth embodiment of the side glass panel according to the present invention. 
         FIG. 8  is a front view showing another example of the side glass panel according to the present invention. 
         FIG. 9  is a front view showing yet another example of the side glass panel according to the present invention. 
         FIG. 10  is a front view showing yet another example of the side glass panel according to the present invention. 
         FIG. 11  is a diagram showing the attachment angle of a side glass panel. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     A. First Embodiment 
     Hereinafter, a first embodiment of aside glass panel for a vehicle according to the present invention will be described with reference to the drawings.  FIG. 1  is a plan view of a side glass panel of this embodiment, and  FIG. 2  is a cross-sectional view of  FIG. 1 . As shown in  FIGS. 1 and 2 , the side glass panel according to this embodiment includes an outer glass plate (first glass plate)  1 , an inner glass plate (second glass plate)  2 , and an interlayer  3  arranged between the glass plates  1  and  2 . Cutout portions  21  and  22  are formed at the lower end portions of the inner glass plate  2 , and connection members  41  and  42  extending from the interlayer  3  are exposed from the cutout portions  21  and  22 , respectively. It should be noted that, unless otherwise stated, the configuration and effects shown in the first embodiment are shared with all of the subsequent embodiments. The individual members will be described below. 
     1. Overview of Side Glass Panel 
     1-1. Glass Plate 
     The glass plates  1  and  2  are formed in a rectangular shape having an upper side  11 , a lower side  12 , a front lateral side  13 , and a rear lateral side  14 . It should be noted that the glass plates  1  and  2  have the same shape, and therefore, in the following description, identical reference numerals  11  to  14  are used to denote the identical sides of the glass plates  1  and  2 . Here, “rectangular shape” means a shape in which the upper side  11 , the lower side  12 , the front lateral side  13 , and the rear lateral side  14  can be identified in outline, and is not necessarily a rectangle. 
     The upper side  11  and the lower side  12  extend parallel to each other, and the upper side  11  is shorter than the lower side  12 . The front lateral side  13  includes a first portion  131  that extends upward from the front end of the lower side  12  and inclines rearward, and a second portion  132  that extends from the upper end of the first portion  131  and inclines further rearward. The rear lateral side  14  extends upward from the rear end of the lower side  12 , substantially parallel to the first portion  131  of the front lateral side  13  and inclines rearward while being slightly curved. Therefore, the rear end of the upper side  11  is located slightly toward the rear with respect to the rear end of the lower side  12 . As described above, the arc-shaped cutout portions  21  and  22  are respectively formed in the front end portion and the rear end portion of the lower side of the inner glass plate  2 . In the description below, the cutout portion formed in the front end portion of the inner glass plate  2  is referred to as “first cutout portion  21 ”, and the cutout portion formed in the rear end portion is referred to as “second cutout portion  22 ”. 
     The side glass panel including the above-mentioned outer glass plate  1  and inner glass plate  2  is to be attached to a vehicle door. The side glass panel is supported by a raising/lowering module (regulator) (not shown) provided inside the door, and is thereby raised and lowered. When the side glass panel is raised and the window is thus closed, the lower side  12  of the side glass panel is located below a belt molding B of the door. Therefore, irrespective of whether the window is open or closed, the lower side  12  of the side glass panel is invisible from the outside and inside of the vehicle. During a process of raising the side glass panel, the first portion  131  of the front lateral side  13  and the rear lateral side  14  are supported by guides (e.g., sash portions) of a door frame and moved up/down along the guides. Therefore, the first portion  131  of the front lateral side  13  and the rear lateral side  14  are accommodated in the guides and are thus invisible from the outside and inside of the vehicle. When the window is closed, the second portion  132  of the front lateral side  13  and the upper side  11  are accommodated inside the door frame and are thus also invisible from the outside and inside of the vehicle. It should be noted that the door frame that conceals the sides  11  to  14  of the side glass panel from the outside and inside of the vehicle corresponds to the blocking portion of the present invention. 
     Known glass plates can be used as the glass plates  11  and  12 , and these glass plates can also be made of heat-ray absorbing glass, regular clear glass or green glass, or UV green glass. However, the glass plates  11  and  12  need to attain a visible light transmittance that conforms to the safety standards of a country in which the automobile is to be used. For example, an adjustment can be made so that the outer glass plate  11  ensures a required solar absorptance and the inner glass plate  12  provides a visible light transmittance that meets the safety standards. An example of the composition of clear glass, an example of the composition of heat-ray absorbing glass, and an example of the composition of soda-lime based glass are shown below. 
     Clear Glass 
     SiO 2 : 70 to 73 mass % 
     Al 2 O 3 : 0.6 to 2.4 mass % 
     CaO: 7 to 12 mass % 
     MgO: 1.0 to 4.5 mass % 
     R 2 O: 13 to 15 mass % (R is an alkali metal) 
     Total iron oxide (T-Fe 2 O 3 ) in terms of Fe 2 O 3 : 0.08 to 0.14 mass % 
     Heat-Ray Absorbing Glass 
     With regard to the composition of heat-ray absorbing glass, a composition obtained based on the composition of clear glass by setting the ratio of the total iron oxide (T-Fe 2 O 3 ) in terms of Fe 2 O 3  to 0.4 to 1.3 mass %, the ratio of CeO 2  to 0 to 2 mass %, and the ratio of TiO 2  to 0 to 0.5 mass % and reducing the components (mainly SiO 2  and Al 2 O 3 ) forming the framework of glass by an amount corresponding to the increases in T-Fe 2 O 3 , CeO 2 , and TiO 2  can be used, for example. 
     Soda-Lime Based Glass 
     SiO 2 : 65 to 80 mass % 
     Al 2 O 3 : 0 to 5 mass % 
     CaO: 5 to 15 mass % 
     MgO: 2 mass % or more 
     NaO: 10 to 18 mass % 
     K 2 O: 0 to 5 mass % 
     MgO+CaO: 5 to 15 mass % 
     Na 2 O+K 2 O: 10 to 20 mass % 
     SO 3 : 0.05 to 0.3 mass % 
     B 2 O 3 : 0 to 5 mass % 
     Total iron oxide (T-Fe 2 O 3 ) in terms of Fe 2 O 3 : 0.02 to 0.03 mass % 
     Although there is no particular limitation on the thickness of the laminated glass according to this embodiment, the total thickness of the outer glass plate  1  and the inner glass plate  2  is preferably set to 2.4 to 4.6 mm, more preferably 2.6 to 3.4 mm, and even more preferably 2.7 to 3.2 mm, from the viewpoint of weight reduction. As described above, there is a need to reduce the total thickness of the outer glass plate  1  and the inner glass plate  2  in order to reduce the weight. Therefore, although there is no particular limitation on the thicknesses of the glass plates, the thicknesses of the outer glass plate  11  and the inner glass plate  12  can be determined as described below, for example. 
     The outer glass plate  1  is mainly required to have durability and impact resistance against external interference. For example, when this laminated glass is used as a windshield of an automobile, the impact-resistance performance with respect to flying objects such as small stones is required. On the other hand, a larger thickness is not preferable because the weight increases. From this viewpoint, the thickness of the outer glass plate  1  is preferably 1.0 to 3.0 mm, and more preferably 1.6 to 2.3 mm. The thickness to be used can be determined in accordance with the application of the glass plate. 
     Although the thickness of the inner glass plate  2  can be made equal to that of the outer glass plate  1 , the thickness of the inner glass plate  2  can be made smaller than that of the outer glass plate  11  in order to reduce the weight of the laminated glass, for example. Specifically, when the strength of the glass plate is taken into consideration, the thickness is preferably 0.6 to 2.0 mm, more preferably 0.8 to 1.8 mm, and even more preferably 1.0 to 1.6 mm. Furthermore, the thickness is preferably 0.8 to 1.3 mm. With regard to the inner glass plate  2  as well, the thickness to be used can be determined in accordance with the application of the glass plate. 
     1-2. Interlayer 
     Next, the interlayer  3  will be described. The interlayer  3  includes three layers, namely a heat generating layer  31  and two bonding layers  32  and  33  between which the heat generating layer  31  is sandwiched. In the description below, the bonding layer that is arranged on the outer glass plate  1  side is referred to as “first bonding layer  32 ”, and the bonding layer that is arranged on the inner glass plate  2  side is referred to as “second bonding layer  33 ”. 
     1-2-1. Heat Generating Layer 
     First, the heat generating layer  31  will be described. The heat generating layer  31  includes a sheet-like substrate  311 , and a first busbar  312 , a second busbar  313 , and a plurality of heating wires  314  that are arranged on the substrate  311 . The substrate  311  can be formed so as to correspond to the above-mentioned glass plates  1  and  2 , but the shape of the substrate  311  is not necessarily the same as that of the glass plates  1  and  2  and may be smaller than that of the glass plates  1  and  2 . For example, as shown in  FIG. 1 , the vertical length of the substrate  311  can be made shorter than the vertical length of the glass plates  1  and  2  in order to prevent the substrate  311  from interfering with the cutout portions  21  and  22  of the inner glass plate  2 . Also, the horizontal length of the substrate  311  can be made shorter than the width of the glass plates  1  and  2 . 
     The busbars  312  and  313  are formed in a belt shape. The first busbar  312  is formed to extend along the first portions  131  of the front lateral sides  13  of the glass plates  1  and  2  on the substrate  311 . On the other hand, the second busbar  313  is formed to extend along the rear lateral sides  14  of the glass plates  1  and  2  on the substrate  311 . It should be noted that the lower end portions of the busbars  312  and  313  are respectively arranged above the above-described cutout portions  21  and  22  so as not to be exposed from the cutout portions  21  and  22  when the interlayer  3  is sandwiched between the glass plates  1  and  2  . The widths in the front-rear direction of the busbars  312  and  313  are preferably 1 to 50 mm, and more preferably 10 to 30 mm, for example. The reason for this is that busbars  312  and  313  with a width of less than 5 mm may be hotter than the heating wires due to a heat-spot phenomenon, whereas busbars  312  and  313  with a width of more than 50 mm may protrude from the guide of the door frame and be visible from the outside and inside of the vehicle. 
     The plurality of heating wires  314  are formed to extend in the front-rear direction so as to connect the busbars  312  and  313 . Thus, the plurality of heating wires  314  extend adjacently to each other, but not all the heating wires  314  are arranged parallel to each other. For example, the heating wire arranged at the lowest position extends along the lower sides  12  so as to connect the lower end portion of the first busbar  312  and the lower end portion of the second busbar  313 , and the heating wire  314  arranged at the highest position extends from the upper end portion of the first busbar  312  to the upper end portion of the second busbar  313  along the second portions  132  of the front lateral sides  13  and the upper sides  11 . That is, the vertical length of the first busbar  312  is shorter than the vertical length of the second busbar  313 , and therefore, the plurality of heating wires  314  extend rearward while the distances between the adjacent heating wires  314  substantially increase. However, the plurality of heating wires  314  have substantially the same length. 
     In order to make it difficult to see the heating wires  314 , the thickness thereof is preferably 3 to 500 μm, more preferably 5 to 20 μm, and even more preferably 8 to 10 μm. The distances between the adjacent heating wires  314  are preferably 1 to 4 mm, more preferably 1.25 to 3 mm, and even more preferably 1.25 to 2.5 mm. 
     It should be noted that the heating wires  314  can be formed in not only a linear shape but also various shapes such as a wave shape. In particular, forming the heating wires  314  in a substantially sinusoidal shape makes it possible to not only make the heat distribution uniform but also prevent the heating wires  314  from optically interrupting the visual field through a windshield. It should be noted that the “substantially sinusoidal shape” does not necessarily have a constant amplitude and a constant wavelength unlike a sinusoidal wave and refers to a wave form with random amplitudes and wavelengths. 
     The width of the heating wires  314  can be measured using a microscope such as VHX-200 (manufactured by Keyence Corporation) at a 1000-fold magnification. It should be noted that it is the cross-sectional areas of the heating wires  314  that practically exert an influence on the generated heat amount, but the width and the cross-sectional area have substantially the same technical meaning. The smaller the widths are, the more difficult the heating wires  314  are to see, and therefore, heating wires  314  having a smaller width are suitable for the windshield according to this embodiment. 
     Next, the materials of the heat generating layer  31  will be described. The substrate  311  is a transparent film for supporting the busbars  312  and  313  and the heating wires  314 , and there is no particular limitation on the material thereof. Examples thereof include polyethylene terephthalate, polyethylene, polymethyl methacrylate, polyvinyl chloride, polyester, polyolefin, polycarbonate, polystyrene, polypropylene, and nylon. The busbars  312  and  313  and the heating wires  314  can be made of the same material, and examples thereof include various materials such as copper (or tinned copper), tungsten, and silver. 
     Subsequently, a method of forming the busbars  312  and  313  and the heating wires  314  will be described. The busbars  312  and  313  and the heating wires  314  can be formed by arranging, on the substrate  311 , thin lines (e.g., wires) and the like that were formed in advance. However, in particular, in order to further reduce the thickness of the heating wires  314 , the heating wires  314  can be formed through patterning on the substrate  311 . There is no particular limitation on such a method, and various methods such as printing, etching, and transfer can be used. At this time, the busbars  312  and  313  and the heating wires  314  can be formed individually or integrally. It shouldbe noted that the term “integrally” means that no boundaries are formed between materials (i.e., “seamlessly”), and no interfaces are present. 
     The following configuration can also be employed. That is, the busbars  312  and  313  are formed on the substrate  311 , and portions of the substrate  311  that correspond to the busbars  312  and  313  are detached and removed so that a portion of the substrate  311  for the heating wires  314  is left. Thereafter, the heating wires are arranged on the portion of the substrate between the busbars  312  and  313 . 
     In particular, when etching is employed, the procedures are as follows, for example. First, a metal foil is laminated on the substrate  311  via a primer layer through dry laminating. An example of the metal foil is a copper foil. The busbars  312  and  313  and the plurality of heating wires  314  can be patterned on the substrate  311  by performing chemical etching treatment using a photo lithography method on the metal foil. In particular, when the thicknesses of the heating wires  314  are reduced (e.g., 15 μmor less), it is preferable to use a thin metal foil. Patterning may also be performed through photo lithography on a thin metal layer (e.g., 5 μmor less) formed on the substrate  311  through deposition, spattering, or the like. 
     1-2-2. Bonding Layer 
     The bonding layers  32  and  33  are sheet-like members for sandwiching the heat generating layer  31  therebetween and bonding the heat generating layer  31  to the glass plates  1  and  2 . The bonding layers  32  and  33  have the same size as the glass plates  1  and  2 , and cutout portions having the same shape as the cutout portions  21  and  22  of the inner glass plate  2  are respectively formed in the bonding layers  32  and  32  at positions corresponding to the cutout portions  21  and  22 . The bonding layers  32  and  33  can be made of various materials, and examples thereof include a polyvinyl butyral resin (PVB) and ethylene vinyl acetate (EVA). In particular, a polyvinyl butyral resin has excellent adhesiveness with the glass plates and excellent penetration resistance, and is thus preferable. It should be noted that surfactant layers may also be provided between the bonding layers and the heat generating layer. The surfaces of the layers can be reformed using such a surfactant, thus making it possible to improve the adhesive strength. 
     1-2-3. Thickness of Interlayer 
     The total thickness of the interlayer  3  is not particularly specified, but is preferably 0.3 to 6.0 mm, more preferably 0.5 to 4.0 mm, and even more preferably 0.6 to 2.0 mm. Also, the thickness of the substrate  311  of the heat generating layer  31  is preferably 0.01 to 2.0 mm, and more preferably 0.03 to 0.6 mm. On the other hand, it is preferable that the thickness of the bonding layers  32  and  33  is larger than the thickness of the heat generating layer  31 . Specifically, the thickness of the bonding layers  32  and  33  is preferably 0.1 to 2.0 mm, and more preferably 0.1 to 1.0 mm. It should be noted that the second bonding layer  33  is brought into close contact with the substrate  311 , and therefore, the thicknesses of the busbars  312  and  313  and the heating wires  314  sandwiched between the second bonding layer  33  and the substrate  311  are preferably 3 to 20 μm. 
     The thicknesses of the heat generating layer  31  and the bonding layers  32  and  33  can be measured as described below, for example. First, the cross section of the laminated glass is magnified by a factor of  175  and displayed using a microscope (e.g., VH-5500 manufactured by Keyence Corporation). Then, the thicknesses of the heat generating layer  31  and the bonding layers  32  and  33  are visually identified and measured. At this time, in order to eliminate variations seen in visual identification, the measurement is performed five times, and average values are taken as the thicknesses of the heat generating layer  31  and the bonding layers  32  and  33 . 
     1-3. Connection Member 
     Next, the connection members will be described. The connection members  41  and  42  are used to connect the busbars  312  and  313  to connection terminals (positive electrode terminal and negative electrode terminal; not shown). The connection members  41  and  42  are made of a conductive material and have a sheet-like shape. In the description below, the connection member connected to the first busbar  312  is referred to as “first connection member  41 ”, and the connection member connected to the second busbar  313  is referred to as “second connection member  42 ”. The connection members  41  and  42  have the same configuration, and therefore, the first connection member  41  will be mainly described hereinafter. 
     The first connection member  41  is formed in a rectangular shape, and is sandwiched between the first busbar  312  and the second bonding layer  33 . The first connection member  41  is fixed to the first busbar  312  using a fixing material  5  such as solder. It is preferable to use solder having a low melting point (e.g., 150° C.) as the fixing material  5  such that the first connection member  41  can be simultaneously fixed using an autoclave during assembly of a side glass panel, which will be described later. The first connection member  41  extends from the first busbar  312  to the upper edge of the outer glass plate  1 , and is exposed from the first cutout portion  21  formed in the inner glass plate  2 . A connection terminal to which a cable extending toward a power source is connected is connected to this exposed portion using a fixing material such as solder. As described above, the connection member  41  and  42  do not protrude from the end portions of the glass plates  1  and  2 , and connection terminals are fixed to the portions thereof exposed from the cutout portions  21  and  22  of the inner glass plate  2 . It should be noted that the connection members  41  and  42  are formed of a thin material, thus making it possible to bend the connection members  41  and  42  and then fix the end portions thereof to the busbar  312  using the fixing material  5  as shown in  FIG. 2 . 
     2. Method for Manufacturing Side Glass Panel 
     Next, a method for manufacturing the side glass panel will be described. First, a manufacturing line for a glass plate will be described. 
     The outer glass plate  11  and the inner glass plate  12  are formed using a known method, and then the interlayer  3  is sandwiched between the outer glass plate  11  and the inner glass plate  12 . Specifically, first, the outer glass plate  1 , the first bonding layer  32 , the heat generating layer  31 , the second bonding layer  33 , and the inner glass plate  2  are layered in this order. At this time, the heat generating layer  31  is arranged such that the surface on which the first busbar  312  and the like are formed faces the second bonding layer  33 . The lower end portion of the heat generating layer  31  is arranged above the cutout portions  21  and  22  of the inner glass plate  2 . Furthermore, the cutout portions of the first and second bonding layers  32  and  33  are matched to the cutout portions  21  and  22  of the inner glass plate  2 . Accordingly, the outer glass plate  1  is exposed from the cutout portions  21  and  22  of the inner glass plate  2 . Subsequently, the connection members  41  and  42  are inserted between the heat generating layer  31  and the second bonding layer  33  through the cutout portions  21  and  22 , respectively. At this time, solder having a low melting point, which serves as the fixing material  5 , is applied to the connection members  41  and  42  so as to be arranged on the busbars  312  and  313 . 
     A laminate obtained by layering the glass plates  1  and  2 , the interlayer  3 , and the connection members  41  and  42  in this manner is placed in a rubber bag and preliminarily bonded together at about 70 to 110° C. under vacuum suction. Preliminary bonding can be performed using a method other than this method, the following method can also be employed. For example, the above-mentioned laminate is heated at 45 to 65° C. in an oven. Subsequently, this laminate is pressed by a roller at 0.45 to 0.55 MPa. Then, this laminate is again heated at 80 to 105° C. in an oven and thereafter again pressed by a roller at 0.45 to 0.55 MPa. Thus, preliminary bonding is finished. 
     Next, permanent bonding is performed. The preliminarily bonded laminate is permanently bonded using an autoclave at a pressure of 8 to 15 atmospheres and at 100 to 150° C., for example. Specifically, permanent bonding can be performed in the conditions of a pressure of 14 atmospheres and at 135° C., for example. The bonding layers  32  and  33  between which the heat generating layer  31  is sandwiched are bonded to the glass plates  1  and  2  through the above-described preliminary bonding and permanent bonding. In addition, the solder on the connection members  41  and  42  is melted, and the connection members  41  and  42  are fixed to the busbars  312  and  313 , respectively. The side glass panel according to this embodiment is thus manufactured. 
     3. Method for Using Side Glass Panel 
     The side glass panel configured as mentioned above is attached to a vehicle body. Furthermore, connection terminals are fixed to the connection members  41  and  42 . When an electric current is applied to the connection terminals thereafter, the electric current is applied to the heating wires  314  via the connection members  41  and  42  and the busbars  312  and  313 , and heat is thus generated. Fogginess of the side glass panel can be removed due to the generated heat. 
     4. Features 
     As described above, with this embodiment, the following effects can be obtained. 
     (1) With this embodiment, the first busbar  312  and the second busbar  313  are respectively arranged to extend along the front lateral side  13  and the rear lateral side  14  of the side glass panel, and the plurality of heating wires  314  are arranged adjacently to each other so as to connect the busbars  312  and  313 . The plurality of heating wires  314  are arranged to extend in the front-rear direction, which is a longitudinal direction, of the side glass panel in this manner, and therefore, it is thus possible to increase the lengths of the heating wires  314 . Therefore, the side glass panel can be heated while being prevented from breaking. The first portion  131  of the front lateral side  13  and the rear lateral side  14  of the side glass panel are accommodated in the glass runs of the door frame, thus making it possible to conceal the busbars  312  and  313  from the outside and inside of the vehicle. 
     (2) The busbars  312  and  313  and the heating wires  314  are made of the same material, and thus have the same coefficient of linear expansion. Accordingly, the following advantages are obtained. If the busbars  312  and  313  and the heating wires  314  are made of different materials, their coefficients of linear expansion will be different. Therefore, if these members are separately produced and fixed, for example, an issue may arise in that the heating wires separate from the busbars due to a harsh environmental change such as a heat cycle test, and the two glass plates included in the laminated glass thus separate from each other. However, if the busbars  312  and  313  and the heating wires  314  are made of the same material as in this embodiment, such an issue can be prevented. 
     (3) The busbars  312  and  313  and the heating wires  314  are formed integrally, thus making it possible to prevent contact failure therebetween and thus prevent defective heat generation. The following is a detailed description of defective heat generation. In general, when a glass plate is heated for defogging, it is required to control the electric current value such that the maximum value of heating temperature is 70 to 80° C., for example, in order to prevent cracks in the glass plate. Accordingly, if heat is locally generated due to above-mentioned contact resistance, the electric current value will need to be controlled taking the temperature at such a portion as the maximum value of heating temperature. As a result, an issue will arise in that control that enables heat to be sufficiently generated overall by the heating wires cannot be performed. However, with the above-mentioned configuration, local heat generation can be prevented, thus making it also possible to perform control that enables heat to be sufficiently generated overall by the heating wires. 
     (4) The heat generating layer  31  in which the busbars  312  and  313  and the heating wires  314  are arranged is sandwiched between the bonding layers  32  and  33 , and the thus obtained laminate is arranged between the glass plates  1  and  2 . Therefore, the heat generating layer  31  can be reliably fixed to the glass plates  1  and  2 . Moreover, covering the busbars  312  and  313  and the heating wires  314  with the second bonding layer  33  makes it possible to prevent these members from coming into contact with the glass plate. As a result, it is possible to prevent the breakage of the glass plate and the like. 
     B. Second Embodiment 
     Next, a second embodiment according to the present invention will be described with reference to  FIG. 3 .  FIG. 3  is a plan view of a side glass panel according to the second embodiment. The second embodiment differs from the first embodiment in the arrangement of the busbars and the heating wires. Therefore, only different portions will be described below, identical constituent elements are denoted by identical reference numerals, and descriptions thereof are omitted. 
     As shown in  FIG. 3 , with the side glass panel according to this embodiment, the first busbar  312  is arranged along the lower sides  12  of the glass plates  1  and  2 , and the second busbar  313  is arranged along the rear lateral sides  14 . The plurality of heating wires  314  connecting the two busbars  312  and  313  are arranged adjacently to each other, and are formed in an arc shape. That is, the plurality of heating wires  314  are formed substantially concentrically about a corner portion  17  at which the lower side  12  and the rear lateral side  14  of the side glass panel intersect. Accordingly, for example, a heating wire  314   a  that connects the vicinity of the rear end portion (first end portion) of the first busbar  312  and the vicinity of the lower end portion (first end portion) of the second busbar  313  is short, and a heating wire  314   b  that connects the vicinity of the front end portion (second end portion) of the first busbar  312  and the vicinity of the upper end portion (second end portion) of the second busbar  313  is long because it extends along the second portion  132  of the front lateral side  13  and the upper side  11 . The longer the heating wire  314  is, the thicker it is. 
     The first connection member  41  is connected to the front end portion of the first busbar  312 , and the second connection member  42  is connected to the lower end portion of the second busbar  313 . Accordingly, the positions at which the connection members  41  and  42  are connected are the same as those in the first embodiment. 
     As described above, with this embodiment, the following effects can be obtained. First, the first busbar  312  is arranged along the lower side  12  of the side glass panel and is thus arranged below the belt molding B. Therefore, the first busbar  312  is invisible from the outside and inside of the vehicle. On the other hand, the second busbar  313  is accommodated in the glass run and is thus invisible from the outside and inside of the vehicle. 
     The plurality of heating wires  314  have different lengths. However, the longer the heating wire  314  is, the thicker it is, and therefore, the heating wires  314  can generate substantially the same amount of heat. That is, when the heating wires  314  have the same width, the amount of heat generated by a longer heating wire  314  is smaller than that generated by a shorter heating wire  314 . To compensate for a decrease in a generated heat amount, the width of the longer heating wire  314  is increased. Accordingly, a uniform amount of generated heat can be supplied to the entire side glass panel, and as a result, fogginess can be removed from the entire side glass panel. 
     C. Third Embodiment 
     Next, a third embodiment according to the present invention will be described with reference to  FIG. 4 .  FIG. 4  is a plan view of a side glass panel according to the third embodiment. The third embodiment differs from the second embodiment in the heating wires. Therefore, only different portions will be described below, identical constituent elements are denoted by identical reference numerals, and descriptions thereof are omitted. 
     As shown in  FIG. 4 , with the side glass panel according to this embodiment, the arrangement of the heating wires  314  is substantially the same as that of the second embodiment, but all the heating wires have the same width. At least one auxiliary heating wire  315  is connected to some of the plurality of heating wires  314 . Thus, the longer the heating wire  314  is, the thicker it is. 
     For example, three auxiliary heating wires  315  pass between the uppermost heating wire  314   a  that connects the vicinity of the front end portion of the first busbar  312  and the vicinity of the upper end portion of the second busbar  313 , and the adjacent heating wire  314   b , and are connected to the heating wire  314   a . One end of each auxiliary heating wire  315  is connected to the uppermost heating wire  314   a , and the other end is connected to the first busbar  312 . On the other hand, a smaller number of auxiliary heating wires  315  are connected to a shorter heating wire  314 , or a shorter auxiliary heating wire  315  is connected thereto. For example, no auxiliary heating wires  315  are connected to the shortest heating wire  314   c , but a short auxiliary heating wire  315  is connected to a slightly longer heating wire  314   d  adjacent to the heating wire  314   c . As described above, when all the heating wires  314  have the same width, at least one auxiliary heating wire  315  is connected to a longer heating wire  314 , or an auxiliary heating wire  315  having a different length is connected thereto, in order to compensate for a decrease in a generated heat amount. 
     As described above, with this embodiment, fogginess can be uniformly removed over the entire side glass panel as with the second embodiment. It should be noted that when a plurality of auxiliary heating wires  315  are provided, the auxiliary heating wires  315  may or may not intersect. The arrangement of the auxiliary heating wires  315  can be determined as appropriate from the viewpoint of supplying a uniform amount of generated heat, thus making it possible to determine the number and the lengths thereof as appropriate. One end of each auxiliary heating wire  315  can also be connected to the second busbar  313 . The distance between the heating wires  314  can also be adjusted instead of providing the auxiliary heating wires  315 . For example, in a region in which longer heating wires  314  are arranged, the distance between the heating wires  314  can be reduced to increase the amount of heat applied to the glass. 
     D. Fourth Embodiment 
     Next, a fourth embodiment according to the present invention will be described with reference to  FIG. 5 .  FIG. 5  is a plan view of a side glass panel according to the fourth embodiment. The fourth embodiment differs from the first embodiment in the arrangement of the busbars and the heating wires. Therefore, only different portions will be described below, identical constituent elements are denoted by identical reference numerals, and descriptions thereof are omitted. 
     As shown in  FIG. 5 , with the side glass panel according to this embodiment, the first busbar  312  is arranged along the front lateral side  13  of the side glass panel. The second busbar  313  is formed to have a shorter length, and is arranged along the vicinity of the rear end portion of the lower side  12 . In addition, a first relay busbar  316  that extends along the lower side  12  is arranged between the front end of the lower side  12  of the side glass panel and the second busbar  313 , and a second relay busbar  317  is further arranged along the upper side  11  of the side glass panel. The first relay busbar  316  is formed to have a length corresponding to the first busbar  312  and the approximate front half of the second relay busbar  317 . 
     The plurality of heating wires  314  are divided into three groups. That is, the plurality of heating wires  314  are divided into a first group  314   x  including the heating wires  314  connecting the first busbar  312  and the first relay busbar  316 , a second group  314   y  including the heating wires  314  connecting the first relay busbar  316  and the second relay busbar  317 , and a third group  314   z  including the heating wires  314  connecting the second relay busbar  317  and the second busbar  313 . The heating wires  314  in the first group  314   x  extend, substantially parallel to each other, downward from the first busbar  312 , and are connected to the front half of the first relay busbar  316 . The heating wires  314  in the second group  314   y  extend, substantially parallel to each other, upward from the rear half of the first relay busbar  316 , and are connected to the front half of the second relay busbar  316 . The heating wires  314  in the third group  314   z  extend, substantially parallel to each other, downward from the rear half of the second relay busbar  317 , and are connected to the second busbar  313 . 
     As described above, with this embodiment, a configuration is employed in which the two relay busbars  316  and  317  are provided between the first busbar  312  and the second busbar  313 , and the plurality of heating wires  314   x ,  314   y , and  314   z  connect the first busbar  312  and the second busbar  313  via the relay busbars  316  and  317 . Accordingly, the heating wires  314  between the first busbar  312  and the second busbar  313  can be made longer. This makes it possible to make the heating wires  314  longer when the heating wires  314  are arranged to extend in the vertical direction in a small side glass panel. 
     E. Fifth Embodiment 
     Next, a fifth embodiment according to the present invention will be described with reference to  FIG. 6 .  FIG. 6  is a plan view of a side glass panel according to the fifth embodiment. The fifth embodiment is substantially the same as the second embodiment, but the arrangement of the heating wires and the busbars is different. Only different portions will be described below, identical constituent elements are denoted by identical reference numerals, and the descriptions thereof are omitted. 
     As shown in  FIG. 6 , with the side glass panel according to this embodiment, the first busbar  312  is arranged along the first portions  131  of the front lateral sides  13  of the glass plates  1  and  2 , and the second busbar  313  is arranged along the substantially front half of the lower sides  12 . The plurality of heating wires  314  connecting the two busbars  312  and  313  are arranged adjacently to each other, and are formed in an arc shape. That is, the plurality of heating wires  314  are formed substantially concentrically about a corner portion  18  at which the front lateral side  13  and the lower side  12  of the side glass panel intersect. Accordingly, for example, a heating wire  314  that connects the vicinity of the lower end portion (first end portion) of the first busbar  312  and the vicinity of the front end portion (first end portion) of the second busbar  313  is short, and a heating wire  314  that connects the vicinity of the upper end portion (second end portion) of the first busbar  312  and the vicinity of the rear end portion (second end portion) of the second busbar  313  is long. The longer the heating wire  314  is, the thicker it is. 
     The first connection member  41  is connected to the front end portion of the first busbar  312 , and the second connection member  42  is connected to the lower end portion of the second busbar  313 . Accordingly, the second cutout portion  22  is formed at a position corresponding to the position of the second connection member  42 . 
     As described above, with this embodiment, the heating wires  314  are arranged near the corner portion  18  located at the lower end of the front portion of the side glass panel. That is, this portion is located at a position corresponding to a side mirror. Accordingly, with the fifth embodiment, particularly the position corresponding to a side mirror is heated and is thus prevented from fogging up, and therefore, the side mirror can be clearly seen from the inside of the vehicle. Since the entire side glass panel is not heated in this manner, the power consumption can be reduced. It should be noted that the widths of longer heating wires  314  are increased in the same manner as in the second embodiment, fogginess of the entirety of a region in which the heating wires  314  are arranged can be uniformly removed. However, the heating wires can be made to have the same width  314 . In this case, it is sufficient that the auxiliary heating wires  315  are provided in the same manner as in the third embodiment. 
     F. Sixth Embodiment 
     Next, a sixth embodiment according to the present invention will be described with reference to  FIG. 7 .  FIG. 7  is a plan view of a side glass panel according to the sixth embodiment. In the sixth embodiment, a configuration for heating a position corresponding to a side mirror is employed as in the fifth embodiment. Only portions different from those of the above-mentioned embodiments will be described below, identical constituent elements are denoted by identical reference numerals, and descriptions thereof are omitted. 
     As shown in  FIG. 7 , with the side glass panel according to this embodiment, the first busbar  312  is arranged near the front ends of the lower sides  12  of the glass plates  1  and  2 . The second busbar  313  is arranged behind the first busbar  312  and extends along the lower side  12 . That is, the busbars  312  and  313  are arranged adjacent to each other on one line along the lower side  12 . The busbars  312  and  313  are short, and the total length of the two busbars  312  and  313  is about half of the length of the lower side  12 . 
     The heating wires  314  connecting the busbars  312  and  313  are formed as follows. That is, the plurality of heating wires  314  are formed in an arc shape about the vicinity of the position at which the rear end of the first busbar  312  is located and the position at which the front end of the second busbar  313  is located. For example, a heating wire  314  connecting the vicinity of the rear end portion (first end portion) of the first busbar  312  and the vicinity of the front end portion (first end portion) of the second busbar  313  is short, and is formed in a small arc shape protruding upward. A heating wire  314  connecting the vicinity of the front end portion (second end portion) of the first busbar  312  and the vicinity of the rear end portion (second end portion) of the second busbar  313  is long, and is formed in a large arc shape protruding upward. The uppermost heating wire  314  is configured such that a portion thereof extends along the first portion  131  of the front lateral side  13 . 
     As described above, the plurality of heating wires  314  are formed in a portion located at a position corresponding to a side mirror. Accordingly, with the sixth embodiment, particularly the position corresponding to a side mirror is heated and is thus prevented from fogging up, and therefore, the side mirror can be clearly seen from the inside of the vehicle. Since the entire side glass panel is not heated in this manner, the power consumption can be reduced. It should be noted that the widths of longer heating wires  314  are increased in the same manner as in the second embodiment, fogginess of the entirety of a region in which the heating wires  314  are arranged can be uniformly removed. However, the heating wires can be made to have the same width  314 . In this case, it is sufficient that the auxiliary heating wires  315  are provided in the same manner as in the third embodiment. 
     5. MODIFIED EXAMPLES 
     Although the embodiments of the present invention have been described above, the present invention is not limited to the above embodiments, and various modifications can be carried out without departing from the gist of the invention. It should be noted that modified examples below can be implemented in combination as appropriate. 
     5-1 
     With the above-mentioned embodiments, the busbars  312  and  313  are accommodated in sash portions and thus are invisible from the outside or inside of the vehicle. However, the busbars  312  and  313  protrude from the sash portions depending on their widths in some cases. In such a case, blocking layers can be layered along the sides of the glass plates  1  and  2  along which the busbars  312  and  313  are arranged.  FIG. 8  shows an example of the side glass panel of the first embodiment in which blocking layers  7  are formed (it will be appreciated that such a configuration can also be applied to the side glass panels of the other embodiments). The blocking layers  7  can be made of ceramic with a dark color such as black, and can be formed on at least one of the outer surface of the outer glass plate  11 , the inner surface of the outer glass plate  11 , the outer surface of the inner glass plate  12 , and the inner surface of the inner glass plate  12 . 
     The blocking layers  7  can be formed in various ways. For example, the blocking layer may be formed on only the inner surface of the outer glass plate  11  or only the inner surface of the inner glass plate  12 , or the blocking layers  7  may be formed on the inner surface of the outer glass plate  11  and the inner surface of the inner glass plate  12 . The blocking layers  7  can be made of ceramic and various materials, and may have the following composition, for example. 
     
       
         
           
               
               
             
               
                   
                 TABLE 1 
               
               
                   
                   
               
               
                   
                 Ceramic paste 
               
               
                   
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
            
               
                   
                 Pigment *1 
                 mass % 
                 10% 
               
               
                   
                 Resin (cellulose resin) 
                 mass % 
                  5% 
               
               
                   
                 Organic solvent (pine 
                 mass % 
                 15% 
               
               
                   
                 oil) 
               
               
                   
                 Glass binder *2 
                 mass % 
                 70% 
               
               
                   
                 Viscosity 
                 dPs 
                 150 
               
               
                   
                   
               
               
                   
                 *1, Main components: copper oxide, chromium oxide, iron oxide, and manganese oxide 
               
               
                   
                 *2, Main components: bismuth borosilicate, zinc borosilicate 
               
            
           
         
       
     
     Although the ceramic can be formed using a screen printing process, it can also be produced, in addition, by transferring a transfer film for firing to the glass plate and firing it. The screen printing can be performed under the conditions that a polyester screen of 355 mesh is used, the coating thickness is 20 μm, the tension is 20 Nm, the squeegee hardness is 80 degrees, the attachment angle is 75°, and the printing speed is 300 mm/s, for example, and then drying is performed in a drying furnace at 150° C. for 10 minutes. The ceramic can thus be formed. 
     The blocking layers  7  can also be formed by bonding blocking films made of a dark-colored resin instead of layering ceramic. 
     5-2 
     With the above-mentioned embodiments, the interlayer  3  includes three layers in total, namely the heat generating layer  31  and the two bonding layers  32  and  33 , but there is no limitation thereto. That is, it is sufficient that the interlayer  3  includes at least the busbars  312  and  313  and the heating wires  314 . Therefore, for example, a configuration can be employed in which only one bonding layer is included, or the heat generating layer  31  is sandwiched between the glass plates  1  and  2  using an adhesive or the like. In addition, a configuration can also be employed in which the heat generating layer  31  does not include the substrate  311 . 
     5-3 
     The heat generating layer  31  can be shaped into various shapes. For example, a sheet-like heat generating layer  31  that is prepared in advance by forming the busbar  312  and  313  and the heating wires  314  on the substrate  311  can be cut into a suitable shape as appropriate and arranged between the glass plates  1  and  2 . Accordingly, when the edges of the glass plates  1  and  2  are curved, for example, the edge of the substrate  311  may be curved correspondingly. It is not necessary that the heat generating layer  31  and the glass plates  1  and  2  have exactly the same shape, and the heat generating layer  31  can be arranged at only a portion in which an antifog effect is desired. Therefore, the heat generating layer  31  can be shaped into various shapes and may be smaller than the glass plates  1  and  2 . It should be noted that the glass plates  1  and  2  can also be shaped into various shapes in addition to a perfect rectangle. 
     With the above-mentioned embodiments, the busbars  312  and  313  and the heating wires  314  are arranged on the substrate  311 , but it is sufficient that at least the heating wires  314  are arranged. Accordingly, the busbars  312  and  313  can also be arranged between the bonding layers  32  and  33 . 
     5-4 
     The adjacent heating wires  314  can be connected using at least one bypass wire. In this case, for example, even when one heating wire  314  breaks, an electric current can be applied through the adjacent heating wire  314 . Such bypass wires can be provided in various ways, and  FIG. 9  shows an example (it will be appreciated that such a configuration can also be applied to the side glass panels of the other embodiments). That is, at least one bypass wire  319  is provided between the adjacent heating wires  314 , and the heating wires  314  can be thereby connected. There is no particular limitation on the positions and number of the bypass wires  319 . There is also no particular limitation on the shape of the bypass wires  319 , and the bypass wire  319  may be arranged to obliquely extend as shown in  FIG. 9 , or may be shaped into various shapes such as a wave shape. It should be noted that the bypass wires  319  can be made of the same material as that of the heating wires  314  in one piece with the heating wires  314 . 
     5-5 
     There is no limitation on the shape of the connection members  41  and  42  and the configuration of the cutout portions  21  and  22  of the inner glass plate  2 . For example, as shown in  FIG. 10 , a configuration can also be employed in which small cutout portions  21  and  22  having a size that is substantially equal to the thickness of the connection members  41  and  42  are formed in the inner glass plate  2 , and the connection members  41  and  42  extending from the busbars  312  and  313  are folded back at the cutout portions  21  and  22  and bonded to the surface of the inner glass plate  2 . This makes it possible to prevent the connection members  41  and  42  from protruding from the end portions of the laminated glass in the surface direction. 
     5-6 
     Each side glass panel described in the above-mentioned embodiments can be attached to a vehicle at various angles. For example, as shown in  FIG. 11 , a side glass panel  10  can be attached at an angle within ±30°, and preferably ±15°, with respect to a vertical direction N. Although a windshield is arranged inclining significantly, the side glass panel  10  rises at an angle closer to a right angle compared with the windshield. Therefore, when the heating wires  314  are arranged to extend in the front-rear direction (horizontal direction) as in the first embodiment, for example, the heating wires  314  are not dense as viewed in the horizontal direction, thus making it possible to prevent obstruction of view. On the other hand, even in a case where the distances between the heating wires  314  are the same, when the side glass panel  10  inclines significantly in the same manner as the windshield, the heating wires  314  are dense as viewed in the horizontal direction, which may cause obstruction of view. 
     5-7 
     There is no particular limitation on the shape of the glass plates  1  and  2 . It is sufficient that the glass plates  1  and  2  have a shape in which the upper side  11 , the lower side  12 , the front lateral side  13 , and the rear lateral side  14  can be identified in outline, and the glass plates  1  and  2  do not necessarily have a rectangular shape. Accordingly, as the front lateral side  13  in the above-mentioned embodiments, each of the sides  11  to  14  may be constituted by a side with two or more angles. The sides  11  to  14  may be linear or curved. 
     5-8 
     With the above-mentioned embodiments, the heat generating layer is provided in the interlayer, but instead, the busbars  312  and  313  and the heating wire  314  can be formed on the inner surface of the outer glass plate  1  or the inner surface of the inner glass plate  2  through screen printing or the like. In this case, the heat generating layer  31  can be constituted by only the substrate  311  or at least one bonding layer. The busbars  312  and  313  and the heating wires  314  can be arranged as described in the above-mentioned embodiments. 
     5-9 
     With the above-mentioned embodiments, the side glass panel is constituted by a laminated glass including the outer glass plate  1 , the inner glass plate  2 , and the interlayer  3 , but can also be constituted by a single glass plate. In this case, the busbars  312  and  313  and the heating wires  314  can be formed on the inner surface of the glass plate through screen printing or the like. The busbars and the heating wires can be arranged as described in the above-mentioned embodiments. 
     LIST OF REFERENCE NUMERALS 
       1  Outer glass plate 
       2  Inner glass plate 
       3  Interlayer 
       31  Heat generating layer 
       311  Substrate 
       312  First busbar 
       313  Second busbar 
       314  Heating wire