Patent Publication Number: US-2021162716-A1

Title: Laminated glass

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of International Application PCT/JP2019/027360, filed on Jul. 10, 2019, and designated the U.S., which is based on and claims priority to Japanese patent application No. 2018-154917 filed on Aug. 21, 2018. The entire contents of these applications are incorporated herein by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     Field of the Invention 
     The present invention relates to laminated glass. 
     Description of the Related Art 
     As window glass for an automobile or a railway vehicle, it is known to apply laminated glass (also referred to as an electrically heating window glass or an electrically heating glass) having an electrically conductive heating material (such as a plurality of resistive heating wires) sandwiched between a pair of glass plates. With this laminated glass, it is possible to dissipate fog from window glass or to eliminate freezing of moisture attached to window glass in winter, by letting the electrically conductive heating material generate heat. 
     Such laminated glass usually includes a pair of glass plates, an intermediate film sandwiched between the pair of glass plates, a first bus bar provided at one end between the pair of glass plates, a second bus bar provided at the other end between the pair of glass plates, an electrically conductive heating material provided between the first bus bar and the second bus bar, and third bus bars connecting the first bus bar and the second bus bar to an extracted portion of the electrode. The electrically conductive heating material is disposed at a see-through area excluding the periphery of the laminated glass. 
     As laminated glass provided with an electrically conductive heating material, one wherein an intermediate film having a thin resistive heating wire made of tungsten embedded therein, is disposed between a pair of glass plates (e.g. Patent Literature 1), one having a transparent electrically conductive coating layer formed on glass (e.g. Patent Literature 2), or one wherein a pattern sheet having an electrically conductive pattern provided on a substrate, is disposed between a pair of glass plates (Patent Literature 3), is known. Furthermore, as an electrically conductive heating material, one having an electrically conductive portion formed on a transparent film substrate (Patent Literature 4) is known. 
     Patent Document 1: JP-A-H8-72674 
     Patent Document 2: JP-A-H6-318492 
     Patent Document 3: JP-A-2016-128370 
     Patent Document 4: JP-A-2011-210487 
     In the conventional laminated glass provided with an electrically conductive heating material, a low resistance metal is employed for a first bus bar, a second bus bar, and a third bus bar in order to sufficiently secure the heat quantity of the electrically conductive heating material disposed at a see-through area of the glass plate. 
     A first bus bar, a second bus bar, and a third bus bar are usually disposed so as to be concealed by a shielding layer (such as a black ceramic layer) formed on the periphery of the glass plate for appearance design. However, the width of the shielding layer tends to become smaller in accordance with the improvement of the designability of window glass in recent years. As the width of the shielding layer becomes small, the width of the first bus bar, the second bus bar, and the third bus bar also become small. Consequently, since the resistance values of the first bus bar, the second bus bar, and the third bus bar are increased and heat generation loss in the first bus bar, the second bus bar, and the third bus bar is increased, the heat generation efficiency of the electrically conductive heating material is reduced. 
     SUMMARY OF THE INVENTION 
     The present disclosure has been made in the view of the above information and has an object to provide laminated glass with improved heat generation efficiency of the electrically conductive heating material. 
     The present disclosure provides laminated glass that includes a pair of glass plates facing each other, an intermediate film positioned between the pair of glass plates, an electrically conductive heating material positioned between the pair of glass plates and having a surface in contact with the intermediate film, a first bus bar and a second bus bar connected to the electrically conductive heating material and positioned between the pair of glass plates, disposed such that the electrically conductive heating material is interposed between the first bus bar and the second bus bar in a plan view, third bus bars at least partly positioned between the pair of glass plates, and connecting the first bus bar and the second bus bar to a pair of electrode leads, and a fourth bus bar at least partly positioned between the pair of glass plates, and disposed so as to be superposed on an area of at least a part of at least one of the first bus bar, the second bus bar, and the third bus bars, wherein the electrically conductive heating material, the first bus bar, the second bus bar, and the third bus bars are integrally formed of a same material. 
     According to one embodiment of the present disclosure, laminated glass with the improved heating efficiency of the electrically conductive heating material can be provided. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIGS. 1A and 1B  are diagrams (No. 1) illustrating a windshield for a vehicle according to the first embodiment. 
         FIG. 2  is a diagram (No. 2) illustrating a windshield for a vehicle according to the first embodiment. 
         FIG. 3  is a diagram illustrating a windshield for a vehicle according to Modification 1 of the first embodiment. 
         FIG. 4  is a diagram illustrating a windshield for a vehicle according to Modification 2 of the first embodiment. 
         FIG. 5  is a diagram illustrating a windshield for a vehicle according to Modification 3 of the first embodiment. 
         FIG. 6  is a diagram (No. 1) illustrating a windshield for a vehicle according to a second embodiment. 
         FIG. 7  is a diagram (No. 2) illustrating a windshield for a vehicle according to a second embodiment. 
         FIG. 8  is a diagram (No. 3) illustrating a windshield for a vehicle according to a second embodiment. 
         FIG. 9  is a diagram (No. 4) illustrating a windshield for a vehicle according to a second embodiment. 
         FIG. 10  is a diagram (No. 5) illustrating a windshield for a vehicle according to a second embodiment. 
         FIG. 11  is a diagram (No. 6) illustrating a windshield for a vehicle according to a second embodiment. 
         FIGS. 12A, 12B, 12C, and 12D  are cross-sectional views illustrating a cross-sectional structure in the vicinity of the fourth bus bar. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Hereinafter, embodiments according to the present disclosure will be described with reference to the drawings. In the following drawings, with respect to the same or similar components, an explanation will be made by using the same reference symbols and duplicate explanation may be omitted. Furthermore, in the following drawings, the size and shape may be partially exaggerated so that the content of the present disclosure can be easily understood. 
     Hereinafter, a windshield for a vehicle will be described as an example, but the present disclosure is not limited to this, and the laminated glass according to the embodiment may be applied to other than the windshields for vehicles. Furthermore, the term “vehicle” typically refers to an automobile but also refers to a moving object with glass including a train, a ship, an aircraft, and the like. 
     Furthermore, a plan view refers to viewing a predetermined area of the windshield from the direction normal to the predetermined area, and a planar shape refers to a shape of the predetermined area of the windshield viewed from the direction normal to the predetermined area. 
     First Embodiment 
       FIGS. 1A and 1B  are a diagram (No. 1) illustrating a windshield for a vehicle according to the first embodiment.  FIG. 1A  schematically illustrates a state in which the windshield is visually recognized from the inside of a vehicle to the outside of the vehicle.  FIG. 1B  is a partially enlarged cross-sectional view along line A-A of  FIG. 1A . 
     In  FIG. 1A , for convenience of explanation, the actual curved shape is omitted and the windshield  20  is shown in a plane. In the following description, reference numeral  20   1  is referred to as an upper edge portion of the windshield  20 , reference numeral  20   2  is referred to as a lower edge portion, reference numeral  20   3  is referred to as a left edge portion, and reference numeral  20   4  is referred to as a right edge portion. When the windshield  20  is attached to a vehicle of a right-hand drive vehicle, the upper edge refers to the edge on the roof side of the vehicle, the lower edge refers to the edge on the engine room side, the left edge refers to the edge on the front passenger seat side, and the right edge refers to the edge on the driver&#39;s seat side. 
     As shown in  FIG. 1 , a windshield  20  is laminated glass for a vehicle including a glass plate  21 , a glass plate  22 , an intermediate film  23 , a shielding layer  24 , an electrically conductive heating material  30 , a first bus bar  31 , a second bus bar  32 , third bus bars  33 , and a fourth bus bar  34 . 
     A glass plate  21  is an in-vehicle side glass plate which becomes the inside of the vehicle when the windshield  20  is attached to the vehicle. Furthermore, a glass plate  22  is an out-vehicle side glass plate that becomes the outside of the vehicle when the windshield  20  is attached to the vehicle. 
     A glass plate  21  and a glass plate  22  are a pair of glass plates facing each other. An intermediate film  23 , an electrically conductive heating material  30 , a first bus bar  31 , a second bus bar  32 , third bus bars  33 , and a fourth bus bar  34  are positioned between the pair of glass plates. However, for a third bus bar  33  and a fourth bus bar  34 , at least a part of the third bus bar  33  and the fourth bus bar  34  may be positioned between the pair of glass plates. In other words, a third bus bar  33  and a fourth bus bar  34  may have a portion extended from between the pair of glass plates to the outside of the pair of glass plates. 
     A glass plate  21  and a glass plate  22  are fixed in a state of interposing the intermediate film  23 , the electrically conductive heating material  30 , the first bus bar  31 , the second bus bar  32 , the third bus bar  33 , and the fourth bus bar  34 . 
     An electrically conductive heating material  30 , a first bus bar  31 , a second bus bar  32 , third bus bars  33 , and a fourth bus bar  34  are disposed between the intermediate film  23  and the glass plate  21 . The in-vehicle side surfaces of the electrically conductive heating material  30  and the fourth bus bar  34  are in contact with the out-vehicle side surface  21   b  of the glass plate  21 . Furthermore, the in-vehicle side surfaces of the first bus bar  31 , the second bus bar  32 , and the third bus bar  33  are in contact with the out-vehicle side surface of the fourth bus bar  34 . Furthermore, the out-vehicle side surfaces of the electrically conductive heating material  30 , the first bus bar  31 , the second bus bar  32 , and the third bus bar  33  are in contact with the in-vehicle side surface of the intermediate film  23 . Furthermore, the intermediate film  23  may be a laminate comprising a plurality of layers. 
     A shielding layer  24  is an opaque layer and may be provided in a belt-shape along the peripheral edge (the upper edge portion  20   1 , the lower edge portion  20   2 , the left edge portion  20   3 , the right edge portion  20   4 ) of the windshield  20 . In the example of  FIG. 1 , a shielding layer  24  is provided on the in-vehicle side surface  21   a  of the glass plate  21 . However, a shielding layer  24 , if necessary, may be provided on the in-vehicle side surface  22   a  of the glass plate  22 , or may be provided on both the in-vehicle side surface  21   a  of the glass plate  21  and the in-vehicle side surface  22   a  of the glass plate  22 . 
     An opaque shielding layer  24  is provided on the peripheral edge of the windshield  20  so that deterioration by ultraviolet rays such as a resin such as urethane holding the peripheral edge of the windshield  20  on a vehicle body and an adhesive member sticking bracket for locking such as a camera to the windshield  20  can be suppressed. Furthermore, the bus bar can be concealed. 
       FIG. 2  is a diagram (No. 2) illustrating a windshield for a vehicle according to the first embodiment, and schematically illustrates a state in which the windshield is visually recognized from the inside of a vehicle to the outside of the vehicle.  FIG. 2  illustrates an area where the shielding layer  24  is formed. 
     A shielding layer  24  includes shielding areas  24   1  and  24   2  formed along the upper edge portion  20   1  and the lower edge portion  20   2  of the windshield  20 , and shielding areas  24   3  and  24   4  formed along the left edge portion  20   3  and the right edge portion  20   4  of the windshield  20 . In the shielding layer  24 , the widths of the shielding areas  24   3  and  24   4  are preferably formed smaller than the widths of the shielding areas  24   1  and  24   2  for widening the right and left visibility of the windshield  20 . 
     For a windshield  20 , a trapezoidal area surrounded by the shielding areas  24   1 ,  24   2 ,  24   3 , and  24   4  is a see-through area  28 , and the electrically conductive heating material  30  shown in  FIG. 1  is disposed at the see-through area  28 . The electrically conductive heating material  30  may be provided on the whole surface of the see-through area  28  or on a part thereof.  FIG. 1A  illustrates a state of seeing through the shielding layer  24 , and only the reference signs of the shielding layer  24 , shielding areas  24   1 ,  24   2 ,  24   3 , and  24   4  are shown. The same applies to  FIG. 3  to  FIG. 9  described below. 
     Returning to  FIG. 1 , the electrically conductive heating material  30  includes a plurality of linear members. The pattern formed of the plurality of linear members is not especially limited, but may be, for example, a mesh shape shown in  FIG. 1A . In  FIG. 1A , each linear member may be a wavy line (for example, a sine wave, a triangular wave, a rectangular wave, etc.), or a combination of a wavy line and a straight line. 
     In the electrically conductive heating material  30 , when each linear member is a wavy line, the wavelength and period may not be constant. Furthermore, when each linear member is a wave line, the phases of the adjacent linear members may be aligned or deviated. However, it is preferable that the phases of the adjacent linear members deviate because the light rays caused by regular scattering of light can be suppressed. 
     A first bus bar  31  and a second bus bar  32  are disposed opposite to each other so as to sandwich the electrically conductive heating material  30  at the see-through area  28  in a plan view and are connected to the electrically conductive heating material  30 . The first bus bar  31  is disposed along the upper edge portion  20   2  of the windshield  20 , and the second bus bar  32  is disposed along the lower edge portion  20   2  of the windshield  20 . 
     A third bus bar  33  connects the first bus bar  31  and the electrode lead  38 , and connects the second bus bar  32  and the electrode lead  39 . In other words, the electrode lead  38  is electrically connected to the first bus bar  31  via the third bus bar  33 , and the electrode lead  39  is electrically connected to the second bus bar  32  via the third bus bar  33 . The electrode leads  38  and  39  are a pair of electrode leads positioned at the end of the third bus bar  33  and connected to the positive side and the negative side of the external power supply. 
     If a voltage is applied between the electrode lead  38  and electrode lead  39 , a current flows through the electrically conductive heating material  30  connected between the first bus bar  31  and the second bus bar  32 , and the electrically conductive heating material  30  generates heat. 
     The electrode lead  38  and the electrode lead  39  may be the third bus bar  33  pulled out of the laminated glass as it is. A notch is provided on the in-vehicle side of the glass plate  21 , and the third bus bar  33  is fixed to the notch so that a connector required for energization can be connected. In the case of connecting the third bus bar  33  to the connector by providing a notch on the in-vehicle side of the glass plate  21 , it is preferable to seal the third bus bar  33  with a resin such as silicone in order to prevent the water from intruding into the connecting part and causing a short-circuiting or corrosion. 
     The electrode lead  38  and the electrode lead  39  may have a structure in which the third bus bar  33  is connected to a harness for taking out the electrodes inside the laminated glass, and the harness is outside the laminated glass. A flat harness is preferably used as the harness for taking out the electrodes, but the harness is not limited to this, and a wire harness or the like may be used. As a method of connecting the third bus bar  33  and the harness for taking out the electrodes, at least one adhesive member selected from solder or an electrically conductive adhesive material (electrically conductive adhesive layer) may be used. Furthermore, the third bus bar  33  may be brought into direct contact with the harness for taking out the electrodes without using the solder or the conductive adhesive material. 
     A fourth bus bar  34  is disposed so as to be superposed on the first bus bar  31 , the second bus bar  32 , and the third bus bar  33 . The following effects can be obtained by superposing the fourth bus bar  34  on the first bus bar  31 , the second bus bar  32 , and the third bus bar  33 . 
     In other words, in an area where the fourth bus bar  34  is superposed, the resistance values of the first bus bar  31 , the second bus bar  32 , and the third bus bar  33  can be reduced by an amount corresponding to the cross-sectional area of the fourth bus bar  34 . Consequently, heat generation loss in the first bus bar  31 , the second bus bar  32 , and the third bus bar  33  can be suppressed even when currents flowing through the first bus bar  31 , the second bus bar  32 , and the third bus bar  33  increase in order to increase the heat quantity of the electrically conductive heating material  30 . Therefore, the windshield  20  sufficiently exhibits anti-fogging and ice melting performance in the see-through area  28  to be heated originally. 
     Furthermore, the first bus bar  31 , the second bus bar  32 , and the third bus bar  33  are preferably disposed so as to be concealed by the shielding areas  24   1 ,  24   2 , and  24   3 . In this regard, as the widths of the shielding areas  24   1 ,  24   2 , and  24   3  are reduced in accordance with the improvement of the design property of the windshield  20 , the widths of the first bus bar  31 , the second bus bar  32 , and the third bus bar  33  are forced to be reduced. 
     If the fourth bus bar  34  is not provided, the resistance values of the first bus bar  31 , the second bus bar  32 , and the third bus bar  33  are increased as the widths of the first bus bar  31 , the second bus bar  32 , and the third bus bar  33  are reduced. 
     However, in the windshield  20 , the fourth bus bar  34  is superposed on the first bus bar  31 , the second bus bar  32 , and the third bus bar  33 . Therefore, even if the widths of the first bus bar  31 , the second bus bar  32 , and the third bus bar  33  are reduced, the resistance values thereof can be reduced. 
     In the present embodiment, as an example, the fourth bus bar  34  is superposed on all of the first bus bar  31 , the second bus bar  32 , and the third bus bar  33 , but the fourth bus bar  34  may be superposed without being limited to this example. Any one or more of the first bus bar  31 , the second bus bar  32 , and the third bus bar  33  may be selected, and the fourth bus bar  34  may be superposed on the selected bus bar. Furthermore, the fourth bus bar  34  may be completely overlapped with one or more bus bars selected from among the first bus bar  31 , the second bus bar  32 , and the third bus bar  33  in a plan view or may be partially overlapped. In other words, the fourth bus bar  34  may be disposed so as to be superposed on at least a part of at least one of the first bus bar  31 , the second bus bar  32 , and the third bus bar  33 . 
     An example of a preferable superposition of the fourth bus bar  34  is a form in which the fourth bus bar  34  is disposed so as to be superposed on at least the third bus bar  33 . The reason why this form is preferable is as follows. 
     Generally, in the case of a windshield, the widths of the left and right shielding areas  24   3  and  24   4  are required to be smaller than the widths of the upper and lower shielding areas  24   1  and  24   2  for sufficiently securing the driving field of view. Consequently, when the bus bar is tried to be concealed by the left and right shielding areas  24   3  and  24   4 , the width of the bus bar is difficult to secure. Then the resistance value of the bus bar is increased, and heat generation loss is likely to occur. 
     Accordingly, the resistance value of the third bus bar  33  can be reduced and heat generation loss can be suppressed by disposing the fourth bus bar  34  so as to be superposed on the third bus bar  33 , which is mostly located in the shielding area  24   3  and has to be narrowed in width. 
     Next, the materials and the like of each component of the windshield  20  will be described. 
     [Glass Plates  21 ,  22 ] 
     The glass plates  21  and  22  may be inorganic glass or organic glass. As the inorganic glass, for example, soda-lime glass, borosilicate glass, non-alkali glass, quartz glass, and the like are used without particular limitation. Of these, soda-lime glass is especially preferable. The inorganic glass may be either untempered glass or tempered glass. Untempered glass is made by molding molten glass into a plate shape and slowly cooling it. Tempered glass is formed by forming a compressive stress layer on the surface of untempered glass. 
     The tempered glass may be either physically tempered glass (for example, wind-cooled tempered glass) or chemically tempered glass. In the case of the physically tempered glass, the glass surface may be tempered by rapidly cooling the glass plate uniformly heated in the bending molding from the temperature near the softening point and generating compressive stress on the glass surface with the temperature difference between the glass surface and the inside of the glass. 
     In the case of the chemically tempered glass, the glass surface may be strengthened by generating compressive stress on the glass surface with an ion-exchange method or the like after bending molding. Furthermore, glass absorbing ultraviolet rays or infrared rays may be used, and the glass plate is preferably transparent, but it may be colored so as not to impair transparency. 
     Examples of organic glass include transparent resins such as polycarbonate. The shapes of the glass plates  21  and  22  are not especially limited to a rectangular shape and may be a shape processed into various shapes and curvatures. Gravity molding, press molding, or the like is used as the bending molding of the glass plates  21  and  22 . The molding method of the glass plates  21  and  22  is not especially limited, but for example, in the case of inorganic glass, a glass plate molded by a float method or the like is preferable. 
     The plate thickness of the glass plates  21  and  22  is preferably 0.4 mm or more and 3.0 mm or less, more preferably 1.0 mm or more and 2.5 mm or less, further preferably 1.5 mm or more and 2.3 mm or less, and especially preferably 1.7 mm or more and 2.0 mm or less. The glass plates  21  and  22  may have the same plate thickness or different plate thicknesses. When the plate thicknesses of the glass plates  21  and  22  are different from each other, it is preferable that the plate thickness of the glass plate positioned inside the vehicle is thinner. When the thickness of the glass plate positioned inside the vehicle is thinner, the windshield  20  can be sufficiently reduced in weight if the thickness of the glass plate positioned inside the vehicle is 0.4 mm or more and 1.3 mm or less. 
     [Intermediate Film  23 ] 
     As an intermediate film  23 , many thermoplastic resins are used, such as a plasticized polyvinyl acetal resin, a plasticized polyvinyl chloride resin, a saturated polyester resin, a plasticized saturated polyester resin, a polyurethane resin, a plasticized polyurethane resin, an ethylene-vinyl acetate copolymerized resin, an ethylene-ethyl acrylate copolymerized resin, etc., which have been used for such applications since the past. Furthermore, a resin composition that includes a modified block copolymer hydride disclosed in JP-A-2015-821 may also be preferably used. The intermediate film  23  is preferably a plasticized polyvinyl acetal-based resin, and more preferably a polyvinyl butyral. 
     The film thickness of the intermediate film  23  is preferably 0.3 mm or more at the thinnest portion as the total film thickness in the configuration shown in  FIG. 1B . When the film thickness of the intermediate film  23  is 0.3 mm or more, the penetration resistance required for the windshield is sufficient. The film thickness of the intermediate film  23  is preferably 2.28 mm or less at the thickest portion. When the maximum film thickness of the intermediate film  23  is 2.28 mm or less, the mass of the laminated glass is not increased excessively. The film thickness of the intermediate film  23  is preferably 0.3 mm or more and 1 mm or less. Furthermore, the intermediate film  23  may not have a uniform thickness and may have a wedge shape in a cross-sectional view. 
     The intermediate film  23  may include a sound-insulating function. For example, an intermediate film  23  may be a sound insulation film which can improve the sound insulation of the laminated glass by forming the intermediate film consisting of three or more layers and making the shore hardness of the inner layer lower than the shore hardness of the outer layer by adjusting the plasticizer or the like. In this case, the shore hardness of the outer layer may be the same or different. 
     For manufacturing the intermediate film  23 , for example, resin materials used for the intermediate film are selected among the resin materials described above, as appropriate. Then, the selected resin materials are extruded and molded at a hot-melt state by using an extruder. An extruded condition, such as an extruding speed of the extruder, is set to be constant. Next, the extruded resin film may be extended, for example, as needed so as to fit the design of the windshield  20 . In such a way, the upper and lower edges of the intermediate film have curvatures. [ 0053 ]. [Shielding Layer  24 ] 
     Examples of a shielding layer  24  include a layer formed by applying black ceramic printing ink on a glass plate with screen printing or the like as well as baking the ink. In the shielding layer  24 , the width of the shielding area (any one of the shielding areas  24   1  to  24   4 ) is preferably larger than the width of the first bus bar  31 , the second bus bar  32 , or a third bus bar  33  disposed in the shielding area. 
     If the shielding layer  24  is provided on the in-vehicle side surface  21   a  of the glass plate  21 , the first bus bar  31 , the second bus bar  32 , the third bus bar  33 , and the fourth bus bar  34  can be concealed by the shielding layer  24  when the windshield  20  is viewed from the inside of the vehicle, and it is preferable because the design property of the appearance is not impaired. 
     Furthermore, if the shielding layer  24  is provided on the in-vehicle side surface  22   a  of the glass plate  22 , the first bus bar  31 , the second bus bar  32 , the third bus bar  33 , and the fourth bus bar  34  can be concealed by the shielding layer  24  when the windshield  20  is viewed from the outside of the vehicle, and it is preferable because the design property of the appearance is not impaired. 
     Furthermore, the shielding layer  24  may be provided on both the in-vehicle side surface  21   a  of the glass plate  21  and the in-vehicle side surface  22   a  of the glass plate  22 . In this case, the first bus bar  31 , the second bus bar  32 , the third bus bar  33 , and the fourth bus bar  34  can be concealed by the shielding layer  24  when the windshield  20  is viewed from the inside and outside of the vehicle, and it is preferable because the design property of the appearance is not impaired. 
     [Electrically Conductive Heating Material  30 , First Bus Bar  31 , Second Bus Bar  32 , and Third Bus Bar  33 ] 
     The electrically conductive heating material  30 , the first bus bar  31 , the second bus bar  32 , and the third bus bar  33  are integrally formed of the same material. The material of the electrically conductive heating material  30 , the first bus bar  31 , the second bus bar  32 , and the third bus bar  33  is not especially limited as long as it is an electrically conductive material such as a metal material. Examples of metal materials include gold, silver, copper, aluminum, tungsten, platinum, palladium, nickel, cobalt, titanium, iridium, zinc, magnesium, tin, and the like. Furthermore, these metals may be plated or may be a composite with an alloy or a resin. 
     A method of forming the electrically conductive heating material  30 , the first bus bar  31 , the second bus bar  32 , and the third bus bar  33  may be an etching method such as photolithography, or a printing method such as screen printing, inkjet printing, offset printing, flexographic printing, or gravure printing. In any method, the electrically conductive heating material  30 , the first bus bar  31 , the second bus bar  32 , and the third bus bar  33  may be integrally formed of the same material. In this case, the electrically conductive heating material  30 , the first bus bar  31 , the second bus bar  32 , and the third bus bar  33  may have the same thickness or different thicknesses from each other. 
     Furthermore, the electrically conductive heating material  30 , the first bus bar  31 , the second bus bar  32 , and the third bus bar  33  may be an electrically conductive thin film such as silver or tin-doped indium oxide formed by a sputtering method. As a method of forming a thin film, a PVD (physical vapor deposition) method such as vacuum vapor deposition or ion plating, or a CVD (chemical vapor deposition) method may also be preferably used. Otherwise, the electrically conductive thin film may be formed by using a wet coating method. 
     In the electrically conductive heating material  30 , the line width of each linear member is preferably 25 μm or less, more preferably 20 μm or less, and further preferably 16 μm or less. As the line width of the linear member of the electrically conductive heating material  30  is narrower, it becomes harder for a driver to visually recognize the linear member, and it can be prevented that the presence of the linear member is an obstacle for driving. 
     In the electrically conductive heating material  30 , the thickness of each linear member is preferably 20 μm or less, more preferably 12 μm or less, and further preferably 8 μm or less. As the thickness of the linear member of the electrically conductive heating material  30  is thinner, the area where the linear member reflects light is reduced, and the sunlight and the light such as a headlamp of an opposing car are less likely to be reflected so that the reflected light can be prevented from being an obstacle to the driver for driving. 
     Generally, the manufacturing process can be simplified and the productivity is further improved by integrally forming the electrically conductive heating material  30 , the first bus bar  31 , the second bus bar  32 , and the third bus bar  33  with the same material. However, as the thickness of the electrically conductive heating material  30  becomes thinner, the thickness of the first bus bar  31 , the second bus bar  32 , and the third bus bar  33  also become thinner. In other words, as the thickness of the linear member of the electrically conductive heating material  30  is made thinner, the area reflecting the light is reduced, and it is desirable for the driver to operate. However, at the same time, the thickness of the first bus bar  31 , the second bus bar  32 , and the third bus bar  33  is made thinner. Therefore, the resistance values of the first bus bar  31 , the second bus bar  32 , and the third bus bar  33  are increased, and heat generation in the essential electrically conductive heating material  30  cannot be sufficiently secured due to heat generation loss. In consideration of the above, the present disclosure is especially useful when the electrically conductive heating material  30 , the first bus bar  31 , the second bus bar  32 , and the third bus bar  33  are integrally formed of the same material, and both visibility of the driver and heating characteristics of the heating glass can be improved. 
     [Fourth Bus Bar  34 ] 
     A fourth bus bar  34  may be formed of a material including any one of gold, silver, copper, aluminum, and tin. A copper ribbon or flat braided copper wire may be preferably used for the fourth bus bar  34 . The copper ribbon or flat braided wire may be plated with a metal other than copper. Furthermore, the fourth bus bar  34  may be made of the same material as the electrically conductive heating material  30 , the first bus bar  31 , the second bus bar  32 , and the third bus bar  33 , or may be made of different materials. 
     At least one adhesive member selected from solder or a conductive adhesive material (conductive adhesive layer) may be used for joining the fourth bus bar  34  to the first bus bar  31 , the second bus bar  32 , and the third bus bar  33 . Furthermore, the fourth bus bar  34  may be brought into direct contact with the first bus bar  31 , the second bus bar  32 , and the third bus bar  33  without using the solder or the conductive adhesive material. 
     The fourth bus bar  34  may be formed with a method such as a screen printing, inkjet printing, offset printing, flexographic printing, or gravure printing. The fourth bus bar  34  may be formed between the glass plate and the first bus bar  31 , the second bus bar  32 , or the third bus bar  33 , and may be formed between the intermediate film  23  and the first bus bar  31 , the second bus bar  32 , or the third bus bar  33 . The thickness of the fourth bus bar  34  is preferably 50 μm or more, more preferably 75 μm or more, and further preferably 100 μm or more. 
     [Method of Manufacturing a Windshield  20 ] 
     A general manufacturing method can be cited as a manufacturing method of a windshield  20 , and one example is shown below. 
     First, the fourth bus bar  34  is formed on the out-vehicle side surface  21   b  of the glass plate  21 . Next, the electrically conductive heating material  30 , the first bus bar  31 , the second bus bar  32 , and the third bus bar  33  are formed on the in-vehicle side surface of the intermediate film  23 . The electrically conductive heating material  30 , the first bus bar  31 , the second bus bar  32 , and the third bus bar  33  may be integrally formed of the same material. For example, a method of forming the electrically conductive heating material  30 , the first bus bar  31 , the second bus bar  32 , and the third bus bar  33  on the in-vehicle side surface of the intermediate film  23  may be direct forming on the intermediate film  23 . Alternatively, for example, the intermediate film consists of two or more layers, and one intermediate film layer having the electrically conductive heating material  30 , the first bus bar  31 , the second bus bar  32 , and the third bus bar  33  formed on the surface is laminated on another intermediate film layer to form the intermediate film  23 . A detailed description of the latter will be described below. 
     Next, an intermediate film  23  is laminated on the glass plate  21  so that the out-vehicle side surface of the fourth bus bar  34  formed on the glass plate  21  is brought into contact with the in-vehicle side surfaces of the first bus bar  31 , the second bus bar  32 , and the third bus bar  33  formed on the intermediate film  23  to manufacture the first laminate. Then, the glass plate  22  is further laminated on the intermediate film  23  of the first laminate to manufacture the second laminate. 
     Subsequently, for example, the second laminate is placed within a rubber bag and then bonded in a vacuum at a pressure of −65 to −100 kPa and temperatures of approximately 70 to 110° C. Furthermore, for example, in a case where the press bonding process for heating and pressurizing the laminate is carried out under conditions of 100 to 150° C. and a pressure of 0.6 to 1.3 MPa, the resulting laminated glass can have excellent durability. However, in some cases, the heating and pressurizing process described above may not be used in consideration of simplifying manufacturing processes as well as properties of materials required for the laminated glass. By heating and pressurizing in a vacuum, the intermediate film  23  is deformed, and the in-vehicle side surface of the electrically conductive heating material  30  formed on the intermediate film  23  is brought into contact with the out-vehicle side surface  21   b  of the glass plate  21 . 
     In the above description regarding the manufacture of laminated glass having the cross-sectional structure shown in  FIG. 1B , the fourth bus bar  34  is formed on the out-vehicle side surface  21   b  of the glass plate  21 , but this is merely an example. For example, an electrically conductive heating material  30 , a first bus bar  31 , a second bus bar  32 , and a third bus bar  33  may be formed on the in-vehicle side surface of the intermediate film  23 , and a fourth bus bar  34  may be formed on the in-vehicle side surfaces of the first bus bar  31 , the second bus bar  32 , and the third bus bar  33 . 
     As described above, in the windshield  20 , a fourth bus bar  34  is disposed so as to be superposed on one or more bus bars of the first bus bar  31 , the second bus bar  32 , and the third bus bar  33 . Accordingly, resistance values of the first bus bar  31 , the second bus bar  32 , and the third bus bar  33  can be reduced in an area where the fourth bus bar  34  is disposed so as to be superposed. Consequently, heat generation loss in the first bus bar  31 , the second bus bar  32 , and the third bus bar  33  can be suppressed even when currents flowing through the first bus bar  31 , the second bus bar  32 , and the third bus bar  33  increase in order to increase the heat quantity of the electrically conductive heating material  30 . Therefore, the windshield  20  sufficiently exhibits anti-fogging and ice melting performance in the see-through area  28  that originally needs to be heated. 
     Furthermore, in the windshield  20 , the temperature at which heat is generated in the first bus bar  31 , the second bus bar  32 , and the third bus bar  33  can be lowered by disposing the fourth bus bar  34  in a superposed manner. Therefore, the concern that the glass plates  21  and  22  may be broken due to the thermal stress due to the heat generated in the first bus bar  31 , the second bus bar  32 , and the third bus bar  33  can be eliminated. 
     Modification 1 of the First Embodiment 
     Modification 1 of the first embodiment shows an example in which the heating zone of the electrically conductive heating material  30  is divided into two or more. For the same elements of Modification 1 as those of the first embodiment, explanations may be omitted. 
       FIG. 3  is a diagram illustrating a windshield for a vehicle according to Modification 1 of the first embodiment, and schematically illustrates a state in which the windshield is visually recognized from the inside of a vehicle to the outside of the vehicle. 
     As shown in  FIG. 3 , the see-through area  28  of the windshield  20 A includes a heating zone A and a heating zone B divided into left and right. Here, the heating zone is an area that is heated by energizing between a set of bus bars. 
     A first bus bar  31 A and a second bus bar  32 A compose a set of bus bars that are disposed opposite to each other across the electrically conductive heating material  30  at the see-through area  28  in the heating zone A and are connected to the electrically conductive heating material  30  at the see-through area  28  in the heating zone A. A first bus bar  31 A is disposed along the upper edge portion  20   1  of the windshield  20 A, and a second bus bar  32 A is disposed along the lower edge portion  20   2  of the windshield  20 A. 
     A third bus bar  33 A connects the first bus bar  31 A and the electrode lead  38 A and connects the second bus bar  32 A and the electrode lead  39 A. In other words, the electrode lead  38 A is electrically connected to the first bus bar  31 A via the third bus bar  33 A, and the electrode lead  39 A is electrically connected to the second bus bar  32 A via the third bus bar  33 A. The electrode leads  38 A and  39 A are a pair of electrode leads positioned at the end of the third bus bar  33 A and connected to the positive and negative sides of the external power supply. 
     If a voltage is applied between the electrode lead  38 A and the electrode lead  39 A, a current flows through the electrically conductive heating material  30  connected between the first bus bar  31 A and the second bus bar  32 A, and the electrically conductive heating material  30  disposed in the heating zone A generates heat. 
     A first bus bar  31 B and a second bus bar  32 B compose a set of bus bars that are disposed opposite to each other across the electrically conductive heating material  30  at the see-through area  28  in the heating zone B and are connected to the electrically conductive heating material  30  at the see-through area  28  in the heating zone B. A first bus bar  31 B is disposed along the upper edge portion  20   1  of the windshield  20 A, and a second bus bar  32 B is disposed along the lower edge portion  20   2  of the windshield  20 A. 
     A third bus bar  33 B connects the first bus bar  31 B and the electrode lead  39 B and connects the second bus bar  32 B and the electrode lead  38 B. In other words, the electrode lead  39 B is electrically connected to the first bus bar  31 B via the third bus bar  33 B, and the electrode lead  38 B is electrically connected to the second bus bar  32 B via the third bus bar  33 B. The electrode leads  38 B and  39 B are a pair of electrode leads positioned at the end of the third bus bar  33 B and connected to the positive and negative sides of the external power supply. 
     If a voltage is applied between the electrode lead  38 B and the electrode lead  39 B, a current flows through the electrically conductive heating material  30  connected between the first bus bar  31 B and the second bus bar  32 B, and the electrically conductive heating material  30  disposed in the heating zone B generates heat. 
     The electrically conductive heating material  30  disposed in the heating zone A and the electrically conductive heating material  30  disposed in the heating zone B are not connected, and temperature control may be performed independently. Furthermore, the windshield  20 A may include three or more heating zones capable of independent temperature control. 
     A fourth bus bar  34  is disposed so as to be superposed on the first bus bars  31 A and  31 B, the second bus bars  32 A and  32 B, and the third bus bars  33 A and  33 B. By disposing the fourth bus bar  34  on the first bus bars  31 A and  31 B, the second bus bars  32 A and  32 B, and the third bus bars  33 A and  33 B in a superposed manner, a similar effect as that of the first embodiment can be obtained. 
     Furthermore, the fourth bus bar  34  may be disposed so as to be superposed on an area of at least a part of at least one of the first bus bars  31 A and  31 B, the second bus bars  32 A and  32 B, and the third bus bars  33 A and  33 B. 
     Modification 2 of the First Embodiment 
     Modification 2 of the first embodiment shows an example in which the feeding direction to the electrically conductive heating material is different from that of the first embodiment. For the same elements of Modification 2 as those of the first embodiment, explanations may be omitted. 
       FIG. 4  is a diagram illustrating a windshield for a vehicle according to Modification 2 of the first embodiment, and schematically illustrates a state in which the windshield is visually recognized from the inside of a vehicle to the outside of the vehicle. 
     As shown in  FIG. 4 , in the windshield  20 B, the first bus bar  31  is disposed along the left edge portion  20   3 , and the second bus bar  32  is disposed along the right edge portion  20   4 . That is, the windshield  20 B differs from the windshield  20  in that the power feeding direction is the horizontal direction, while the power feeding direction of the windshield  20  is the vertical direction (see  FIGS. 1A and 1B ). As described above, the power feeding direction may be the horizontal direction or the vertical direction of the windshield. 
     In the windshield  20 B, the fourth bus bar  34  may be disposed so as to be superposed on all of the first bus bar  31 , the second bus bar  32 , and the third bus bar  33 , but the superposing form of the fourth bus bar  34  is not limited to this. The fourth bus bar  34  may be disposed so as to be superposed on an area of at least a part of at least one of the first bus bar  31 , the second bus bar  32 , and the third bus bar  33 . 
     An example of a preferable superposition of the fourth bus bar  34  is a form in which the fourth bus bar  34  is disposed so as to be superposed only on the first bus bar  31  and the second bus bar  32 . The reason why this form is preferable is as follows. 
     As was previously described, generally, in the case of a windshield, the widths of the left and right shielding areas  24   3  and  24   4  are required to be smaller than the widths of the upper and lower shielding areas  24   2  and  24   2  for sufficiently securing the driving field of view. Consequently, when the bus bar is tried to be concealed by the left and right shielding areas  24   3  and  24   4 , the width of the bus bar is difficult to secure. Then the resistance value of the bus bar is increased, and heat generation loss is likely to occur. Furthermore, since the windshield is generally longer in the horizontal direction than in the vertical direction, the electrically conductive heating material and the bus bar are required to have lower resistance when power is fed in the horizontal direction. 
     Therefore, considering such characteristics of the windshield, in the windshield  20 B in which the power is fed in the horizontal direction, it is preferable that the fourth bus bar  34  is disposed so as to be superposed on at least the first bus bar  31  and the second bus bar  32 . This allows the resistance values of the first bus bar  31  and the second bus bar  32  to be reduced, and the heat generation loss can be suppressed. 
     Modification 3 of the First Embodiment 
     Modification 3 of the first embodiment shows an example in which the disposition of the linear members of the electrically conductive heating material is different from that of the first embodiment. For the same elements of Modification 2 as those of the first embodiment, explanations may be omitted. 
       FIG. 5  is a diagram illustrating a windshield for a vehicle according to Modification 3 of the first embodiment, and schematically illustrates a state in which the windshield is visually recognized from the inside of a vehicle to the outside of the vehicle. 
     As shown in  FIG. 5 , the windshield  20 C differs from the windshield  20 B (see  FIG. 4 ) in that the electrically conductive heating material  30  is replaced with the electrically conductive heating material  30 C. The electrically conductive heating material  30 C includes a plurality of linear members disposed in a direction along the upper edge portion  20   1  and the lower edge portion  20   2 . The line width and thickness of each linear member of the electrically conductive heating material  30 C may be the same as in the case of the electrically conductive heating material  30 . 
     In  FIG. 5 , each linear member may be a wavy line (for example, a sine wave, a triangular wave, a rectangular wave, etc.) or a combination of a wavy line and a straight line. 
     In the electrically conductive heating material  30 C, when each linear member is a wavy line, the wavelength and period may not be constant. Furthermore, when each linear member is a wave line, the phases of the adjacent linear members may be aligned or deviated. However, it is preferable that the phases of the adjacent linear members deviate because the light rays caused by regular scattering of light can be suppressed. 
     In such a manner, the linear member of the electrically conductive heating material may be in the mesh shape shown in  FIG. 1  or in the horizontal linear shape shown in  FIG. 5 . 
     Second Embodiment 
     The second embodiment shows an example in which an electrically conductive heating material is disposed in a windshield including an information transmitting/receiving area. In the second embodiment, the explanation of the same elements as the embodiment previously described may be omitted. 
       FIG. 6  is a diagram (No. 1) illustrating a windshield for a vehicle according to the second embodiment, and schematically illustrates a state in which the windshield is visually recognized from the inside of a vehicle to the outside of the vehicle. 
     As shown in  FIG. 6 , an information transmitting/receiving area  50  is defined on the windshield  20 D. An information transmitting/receiving area  50  functions as an area where the device transmits and/or receives information when a device (camera, various sensors, etc.) transmitting and/or receiving information is disposed near an upper edge part  20   1  of the windshield  20 D in a vehicle. The shape of the information transmitting/receiving area  50  is not especially limited to a planar shape, and, for example, a trapezoid shape may be applied. 
     If an electrically conductive heating material or a bus bar exists in the information transmitting/receiving area  50 , the device may be prevented from transmitting and/or receiving information. In consideration of the above, it is preferable that an electrically conductive heating material and a bus bar are not disposed in the information transmitting/receiving area  50 . 
     For example, as shown in  FIG. 6 , the electrically conductive heating material  30  is not disposed in the information transmitting/receiving area  50 , and the first bus bar  31  may be disposed so as to bypass the outer edges of left and right edges and the lower edge of the information transmitting/receiving area  50 . 
       FIG. 6  illustrates an example when the power feeding direction is the vertical direction, while  FIG. 7  illustrates an example when the power feeding direction is the horizontal direction. In  FIG. 7 , Region R without an electrically conductive heating material  30 , a first bus bar  31 , and a second bus bar  32  is provided on the upper edge portion  20   1  of the windshield  20 E, and an information transmitting/receiving area  50  is defined in Region R. In this case, such as an antenna disposition area  52  in a rectangular shape in a plan view may be defined in Region R. 
     However, when the electrically conductive heating material  30  is designed so as not to affect the device (camera, various sensors, etc.) (for example, when the line width of the electrically conductive heating material  30  is narrower and the film thickness is thinner, etc.), the electrically conductive heating material  30  may be disposed in the information transmitting/receiving area  50  as shown in  FIG. 8  and  FIG. 9 . For example, the electrically conductive heating material  30  may be a mesh shape, a linear shape, or a sine wave shape. 
     In a windshield  20 F shown in  FIG. 8  and a windshield  20 G shown in  FIG. 9 , the electrically conductive heating material  30  also exists in the information transmitting/receiving area  50 , and power can be fed through the first bus bar  31 , the second bus bar  32 , and the third bus bar  33 .  FIG. 8  illustrates an example in which the power is fed to the electrically conductive heating material  30  in the information transmitting/receiving area  50  in the vertical direction, and  FIG. 9  illustrates an example in which the power is fed in the horizontal direction. In  FIG. 8  and  FIG. 9 , the inside of the see-through area  28  and the inside of the information transmitting/receiving area  50  may be heated independently. 
     By designing the electrically conductive heating material  30  so as not to affect the device (camera, various sensors, etc.), the electrically conductive heating material  30  can also be disposed in the information transmitting/receiving area  50 . By heating the electrically conductive heating material  30  in the information transmitting/receiving area  50 , the information transmitting/receiving area  50  is available of anti-fogging and ice melting performance. 
     Furthermore, a fourth bus bar  34  may be disposed so as to be superposed on a part or all of the first bus bar  31 , the second bus bar  32 , and the third bus bar  33  for feeding power to the electrically conductive heating material  30  in the information transmitting/receiving area  50 . This allows the resistance value of the bus bar disposed so as to be superposed the fourth bus bar to be reduced, and heat generation loss can be suppressed. 
     As a windshield  20 H shown in  FIG. 10  or a windshield  20   1  shown in  FIG. 11 , the electrically conductive heating material  30  may be disposed only in the information transmitting/receiving area  50 , and the power may be fed through the first bus bar  31 , the second bus bar  32 , and the third bus bar  33 . In  FIG. 10  and  FIG. 11 , the electrically conductive heating material  30  is not disposed at the see-through area  28 . 
     &lt;Modification of Cross-Sectional Structure&gt; 
     A cross-sectional structure in the vicinity of the fourth bus bar  34  is shown in  FIG. 1B , but the cross-sectional structure in the vicinity of the fourth bus bar  34  is not limited to  FIG. 1B  and may be modified as shown in  FIG. 12A  to  FIG. 12D  in each embodiment. In  FIG. 12A ˜ FIG. 12D , the explanation of the same elements as the embodiment previously described may be omitted. 
       FIGS. 12A-12D  are cross-sectional views illustrating a cross-sectional structure in the vicinity of the fourth bus bar and illustrates a cross-sectional view corresponding to  FIG. 1B . 
     In  FIG. 12A , the in-vehicle side surfaces of the electrically conductive heating material  30 , the first bus bar  31 , the second bus bar  32 , and the third bus bar  33  are in contact with the out-vehicle side surface  21   b  of the glass plate  21 . Furthermore, the fourth bus bar  34  is positioned between the first bus bar  31 , the second bus bar  32 , and the third bus bar  33  and the intermediate film  23 , and the in-vehicle side surface of the fourth bus bar  34  is in contact with the out-vehicle side surfaces of the first bus bar  31 , the second bus bar  32 , and the third bus bar  33 . Furthermore, the out-vehicle side surface of the electrically conductive heating material  30  and the out-vehicle side surface of the fourth bus bar  34  are in contact with the in-vehicle side surface of the intermediate film  23 . 
     In order to manufacture laminated glass having a cross-sectional structure shown in  FIG. 12A , first, a fourth bus bar  34  is formed on the in-vehicle side surface of the intermediate film  23 . 
     Next, an electrically conductive heating material  30 , a first bus bar  31 , a second bus bar  32 , and a third bus bar  33  are formed on the intermediate film  23 . At this time, the electrically conductive heating material  30  is formed on the in-vehicle side surface of the intermediate film  23 , and the first bus bar  31 , the second bus bar  32 , and the third bus bar  33  are formed on the in-vehicle side surface of the fourth bus bar  34 . The electrically conductive heating material  30 , the first bus bar  31 , the second bus bar  32 , and the third bus bar  33  may be integrally formed of the same material. 
     Next, an intermediate film  23  is laminated on the glass plate  21  so that the surface  21   b  on the out-vehicle side surface  21   b  of the glass plate  21  and the in-vehicle side surfaces of the first bus bar  31 , the second bus bar  32 , and the third bus bar  33  formed on the intermediate film  23  come into contact with each other to manufacture a first laminate. Then, a glass plate  22  is further laminated on the intermediate film  23  of the first laminate to manufacture a second laminate. Next, by heating and pressurizing the second laminate in a vacuum, the laminated glass having the cross-sectional structure shown in  FIG. 12A  can be manufactured. By heating and pressurizing in a vacuum, the intermediate film  23  is deformed, and the in-vehicle side surface of the electrically conductive heating material  30  formed on the intermediate film  23  is brought into contact with the out-vehicle side surface  21   b  of the glass plate  21 . 
       FIG. 12B  is an example of changing the single-layer intermediate film  23  in  FIG. 1B  to the laminated structure of a first intermediate film  231  provided on the glass plate  21  side and a second intermediate film  232  provided on the glass plate  22  side. The first intermediate film  231  and the second intermediate film  232  are in contact with each other. The electrically conductive heating material  30 , the first bus bar  31 , the second bus bar  32 , the third bus bar  33 , and the fourth bus bar  34  are disposed between the first intermediate film  231  and the glass plate  21 . 
     In  FIG. 12B , the in-vehicle side surfaces of the electrically conductive heating material  30  and the fourth bus bar  34  are in contact with the out-vehicle side surface  21   b  of the glass plate  21 . Furthermore, the in-vehicle side surfaces of the first bus bar  31 , the second bus bar  32 , and the third bus bar  33  are in contact with the out-vehicle side surface of the fourth bus bar  34 . Furthermore, the out-vehicle side surfaces of the electrically conductive heating material  30 , the first bus bar  31 , the second bus bar  32 , and the third bus bar  33  are in contact with the in-vehicle side surface of the first intermediate film  231 . 
     The film thickness of the first intermediate film  231  is preferably 0.01 mm or more and 0.8 mm or less, more preferably 0.025 mm or more and 0.4 mm or less, and further preferably 0.05 mm or more and 0.1 mm or less. If the film thickness of the first intermediate film  231  is equal to or more than the lower limit, the processability and handling efficiency during manufacturing is excellent. If the film thickness of the first intermediate film  231  is equal to or less than the upper limit, heat transfer to the outside of the glass by energization is excellent. 
     The film thickness of the second intermediate film  232  is preferably 0.3 mm or more and 2.0 mm or less, more preferably 0.4 mm or more and 1.8 mm or less, and further preferably 0.5 mm or more and 1.5 mm or less. If the film thickness of the second intermediate film  232  is equal to or more than the lower limit, the penetration resistance is excellent. If the film thickness of the second intermediate film  232  is equal to or less than the upper limit, the weight reduction is excellent. 
     Young&#39;s modulus of the first intermediate film  231  is preferably larger than Young&#39;s modulus of the second intermediate film  232 . Since the first intermediate film  231  has a high Young&#39;s modulus, it has rigidity and is excellent in handling efficiency even if the film thickness is thin, so that the electrically conductive heating material  30 , the first bus bar  31 , the second bus bar  32 , the third bus bar  33 , and the like can be formed accurately. On the other hand, the second intermediate film  232  satisfies performance related to safety such as penetration resistance of laminated glass by having proper flexibility. A predetermined Young&#39;s modulus of the first intermediate film  231  is obtained, for example, by reducing an amount of plasticizer to be added to the polyvinyl acetal-based resin to a small amount, or preferably without adding the plasticizer. 
     In order to manufacture laminated glass having a cross-sectional structure shown in  FIG. 12B , first, a fourth bus bar  34  is formed on the out-vehicle side surface  21   b  of the glass plate  21 . 
     Next, an electrically conductive heating material  30 , a first bus bar  31 , a second bus bar  32 , and a third bus bar  33  are formed on the in-vehicle side surface of the first intermediate film  231 . The electrically conductive heating material  30 , the first bus bar  31 , the second bus bar  32 , and the third bus bar  33  may be integrally formed of the same material. 
     Next, a first intermediate film  231  is laminated on the glass plate  21  so that the out-vehicle side surface of the fourth bus bar  34  formed on the glass plate  21  and the in-vehicle side surfaces of the first bus bar  31 , the second bus bar  32 , and the third bus bar  33  formed on the first intermediate film  231  come into contact with each other to manufacture a first laminate. Then, a second intermediate film  232  and a glass plate  22  is further laminated successively on the first intermediate film  231  of the first laminate to manufacture a second laminate. Next, by heating and pressurizing the second laminate in a vacuum, the laminated glass having the cross-sectional structure shown in  FIG. 12B  can be manufactured. By heating and pressurizing in a vacuum, the first intermediate film  231  is deformed, and the in-vehicle side surface of the electrically conductive heating material  30  formed on the first intermediate film  231  is brought into contact with the out-vehicle side surface  21   b  of the glass plate  21 . 
     In the above description of the manufacture of the laminated glass having the cross-sectional structure of  FIG. 12B , the fourth bus bar  34  is formed on the out-vehicle side surface  21   b  of the glass plate  21 , but this is merely an example. For example, a process may be applied such as forming an electrically conductive heating material  30 , a first bus bar  31 , a second bus bar  32 , and a third bus bar  33  on the in-vehicle side surface of the first intermediate film  231 , and forming a fourth bus bar  34  on the in-vehicle side surfaces of the first bus bar  31 , the second bus bar  32 , and the third bus bar  33 . 
       FIG. 12C  is an example of changing the single-layer intermediate film  23  in  FIG. 12A  to the laminated structure of a first intermediate film  231  provided on the glass plate  21  side and a second intermediate film  232  provided on the glass plate  22  side. The electrically conductive heating material  30 , the first bus bar  31 , the second bus bar  32 , the third bus bar  33 , and the fourth bus bar  34  are disposed between the first intermediate film  231  and the glass plate  21 . 
     In  FIG. 12C , the in-vehicle side surfaces of the electrically conductive heating material  30 , the first bus bar  31 , the second bus bar  32 , and the third bus bar  33  are in contact with the out-vehicle side surface  21   b  of the glass plate  21 . Furthermore, the fourth bus bar  34  is positioned between the first bus bar  31 , the second bus bar  32 , and the third bus bar  33  and the first intermediate film  231 , and the in-vehicle side surface of the fourth bus bar  34  is in contact with the out-vehicle side surfaces of the first bus bar  31 , the second bus bar  32 , and the third bus bar  33 . Furthermore, the out-vehicle side surface of the electrically conductive heating material  30  and the out-vehicle side surface of the fourth bus bar  34  are in contact with the in-vehicle side surface of the first intermediate film  231 . 
     In order to manufacture laminated glass having a cross-sectional structure shown in  FIG. 12C , first, a fourth bus bar  34  is formed on the in-vehicle side surface of the first intermediate film  231 . 
     Next, an electrically conductive heating material  30 , a first bus bar  31 , a second bus bar  32 , and a third bus bar  33  are formed on the first intermediate film  231 . At this time, the electrically conductive heating material  30  is formed on the in-vehicle side surface of the first intermediate film  231 , and the first bus bar  31 , the second bus bar  32 , and the third bus bar  33  are formed on the in-vehicle side surface of the fourth bus bar  34 . The electrically conductive heating material  30 , the first bus bar  31 , the second bus bar  32 , and the third bus bar  33  may be integrally formed of the same material. 
     Next, a first intermediate film  231  is laminated on the glass plate  21  so that the out-vehicle side surface  21   b  of the glass plate  21  and the in-vehicle side surfaces of the first bus bar  31 , the second bus bar  32 , and the third bus bar  33  formed on the first intermediate film  231  come into contact with each other to manufacture a first laminate. Then, a second intermediate film  232  and a glass plate  22  is further laminated successively on the first intermediate film  231  of the first laminate to manufacture a second laminate. Next, by heating and pressurizing the second laminate in a vacuum, the laminated glass having the cross-sectional structure shown in  FIG. 12C  can be manufactured. By heating and pressurizing in a vacuum, the first intermediate film  231  is deformed, and the in-vehicle side surface of the electrically conductive heating material  30  formed on the first intermediate film  231  is brought into contact with the out-vehicle side surface  21   b  of the glass plate  21 . 
       FIG. 12D  is an example of changing the single-layer intermediate film  23  in  FIG. 12A  to the laminated structure of a first intermediate film  231  provided on the glass plate  21  side and a second intermediate film  232  provided on the glass plate  22  side. The electrically conductive heating material  30 , the first bus bar  31 , the second bus bar  32 , the third bus bar  33 , and the fourth bus bar  34  are disposed between the first intermediate film  231  and the second intermediate film  232 . 
     In  FIG. 12D , the in-vehicle side surfaces of the electrically conductive heating material  30 , the first bus bar  31 , the second bus bar  32 , and the third bus bar  33  are in contact with the out-vehicle side surface of the first intermediate film  231 . Furthermore, the fourth bus bar  34  is positioned between the first bus bar  31 , the second bus bar  32 , and the third bus bar  33  and the second intermediate film  232 , and the in-vehicle side surface of the fourth bus bar  34  is in contact with the out-vehicle side surface of the first bus bar  31 , the second bus bar  32 , and the third bus bar  33 . Furthermore, the out-vehicle side surface of the electrically conductive heating material  30  and the out-vehicle side surface of the fourth bus bar  34  are in contact with the in-vehicle side surface of the second intermediate film  232 . 
     In order to manufacture laminated glass having a cross-sectional structure shown in  FIG. 12D , first, an electrically conductive heating material  30 , a first bus bar  31 , a second bus bar  32 , and a third bus bar  33  are formed on the out-vehicle side surface of the first intermediate film  231 . The electrically conductive heating material  30 , the first bus bar  31 , the second bus bar  32 , and the third bus bar  33  may be integrally formed of the same material. 
     Next, a fourth bus bar  34  is formed on the out-vehicle side surfaces of the first bus bar  31 , the second bus bar  32 , and the third bus bar  33  formed on the first intermediate film  231 . 
     Next, a first intermediate film  231  is laminated on the glass plate  21  so that the out-vehicle side surface  21   b  of the glass plate  21  and the in-vehicle side surfaces of the first intermediate film  231  come into contact with each other to manufacture a first laminate. Then, a second intermediate film  232  is laminated so as to come into contact with the out-vehicle side surfaces of the electrically conductive heating material  30  and the fourth bus bar  34  formed on the first intermediate film  231  of the first laminate, and a glass plate  22  is further laminated to manufacture a second laminate. Next, by heating and pressurizing the second laminate in a vacuum, the laminated glass having the cross-sectional structure shown in  FIG. 12D  can be manufactured. By heating and pressurizing in a vacuum, the second intermediate film  232  is deformed, and the out-vehicle side surface of the electrically conductive heating material  30  formed on the first intermediate film  231  is brought into contact with the in-vehicle side surface of the second intermediate film  232 . 
     In such a manner, the cross-sectional structure in the vicinity of the fourth bus bar  34  can be variously formed, and the intermediate film  23  may be a laminated structure of a plurality of intermediate films. 
     Although the preferred embodiments and the like have been described above, the embodiments are not limited to the above embodiments and the like, and various modifications and substitutions can be added to the above embodiments and the like without deviating from the scope stated in the claims. 
     For example, each embodiment and modification can be combined appropriately. For example, when the power feeding direction is horizontal as shown in  FIG. 4 , the area for heating by the electrically conductive heating material  30  may be divided into two or more areas. 
     Furthermore, in each embodiment and modification, the electrically conductive heating material  30 , the first bus bar  31 , the second bus bar  32 , the third bus bar  33 , and the fourth bus bar  34  are disposed on the glass plate  21  which is an in-vehicle side. However, the electrically conductive heating material  30 , the first bus bar  31 , the second bus bar  32 , the third bus bar  33 , and the fourth bus bar  34  may be disposed on the glass plate  22  which is an out-vehicle side. In the case of disposing the fourth bus bar  34  on the glass plate  22  which is an out-vehicle side, the fourth bus bar may be in contact with the glass plate  22 .