Patent Application: US-99347509-A

Abstract:
provided is a conductive film suitable for use in a transparent heating element having superior visibility and heat generation properties . a conductor of a first conductive film has a mesh pattern which has a plurality of lattice cross points formed by a plurality of first metal nanowires and a plurality of second metal nanowires . the conductor between intersections is formed in a wave - like shape having at least one curve . the array period of an arc of one first metal nanowire from among parallel adjacent first metal nanowires is one period . the array period of an arc of another first metal nanowire constitutes two periods . similarly , the array period of an arc of one second metal nanowire is one period . the array period of an arc of another second metal nanowire constitutes two periods .

Description:
several embodiments of the conductive film and the transparent heating element of the present invention will be described below with reference to fig1 to 31 . as shown in fig1 , a conductive film according to a first embodiment ( hereinafter referred to as the first conductive film 10 a ) contains a plurality of conductive portions 12 and a plurality of opening portions 14 , and the combination of the conductive portions 12 and the opening portions 14 has mesh shapes m . each mesh shape m is a combined shape of one opening portion 14 and four conductive portions 12 surrounding the opening portion 14 . the first conductive film 10 a can be used as a part of a defroster ( defrosting device ) or a window glass for a vehicle . the first conductive film 10 a can be used also in a transparent heating element capable of heat generation by applying electric current . as shown in fig2 , the first conductive film 10 a has a transparent film substrate 16 , and the conductive portions 12 and the opening portions 14 formed thereon . as shown in fig3 , when the first conductive film 10 a is used in a transparent heating element 18 , a first electrode 20 a and a second electrode 20 b are disposed on the opposite ends of the first conductive film 10 a ( e . g ., the right and left ends of fig3 ). when an electric current is flowed from the first electrode 20 a to the second electrode 20 b , the transparent heating element 18 generates heat . thus , a heating object ( such as a building window glass , a vehicle window glass , or a vehicle light front cover ), which is brought into contact or equipped with the transparent heating element 18 , is heated . as a result , snow or the like attached to the object can be removed . as shown in fig1 , the conductive portions 12 in the first conductive film 10 a have a mesh pattern 22 formed by crossing a plurality of first thin metal wires 12 a arranged at a first pitch l 1 in one direction ( the x direction of fig1 ) and a plurality of second thin metal wires 12 b arranged at a second pitch l 2 in another direction ( the y direction of fig1 ). the first pitch l 1 and the second pitch l 2 may be selected within a range of 150 μm to 6000 μm ( 6 . 0 mm ). the line width d of the first thin metal wires 12 a and the second thin metal wires 12 b may be selected within a range of 5 μm to 200 μm ( 0 . 2 mm ). it is to be understood that the line width d may be selected within a range of 5 to 50 μm to improve the transparency . thus , the conductive portions 12 are formed of the plural first thin metal wires 12 a and the plural second thin metal wires 12 b in the mesh pattern 22 having a large number of lattice intersection points ( intersections 24 ). each of the conductive portions 12 is formed in a wavy line shape containing at least one curve between the intersections 24 . specifically , among the plural first thin metal wires 12 a , each alternate first thin metal wire 12 a 1 ( one first thin metal wire 12 a 1 ) has a shape with arc - shaped curves , and two arcs 26 extending in alternate crest and trough directions are continuously formed between the intersections 24 . among the plural first thin metal wires 12 a , each first thin metal wire 12 a 2 other than the first thin metal wires 12 a 1 ( the other first thin metal wire 12 a 2 ) has a shape with arc - shaped curves , and four arcs 26 extending in alternate crest and trough directions are continuously formed between the intersections 24 . in terms of the arrangement period of the arcs 26 , the length , in which two arcs 26 extending in alternate crest and trough directions are continuously formed , is considered as 1 period . then , the one first thin metal wire 12 a 1 have 1 period of the arcs between the intersections , and the other first thin metal wires 12 a 2 have 2 periods of the arcs between the intersections . thus , in the first conductive film 10 a , the adjacent parallel first thin metal wires 12 a ( the one first thin metal wire 12 a 1 and the other first thin metal wire 12 a 2 ) have different arc arrangement periods . also among the second thin metal wires 12 b , one second thin metal wires 12 b 1 have 1 period of the arcs between the intersections 24 , and the other second thin metal wires 12 b 2 have 2 periods of the arcs between the intersections 24 . it is to be understood that , when the one first thin metal wire 12 a 1 has i period of the arcs between the intersections 24 , the other first thin metal wire 12 a 2 has j period of the arcs between the intersections 24 , the one second thin metal wire 12 b 1 has p period of the arcs between the intersections 24 , and the other second thin metal wire 12 b 2 has q period of the arcs between the intersections 24 , the periods may satisfy one of the following relations . each arc 26 has a central angle of 75 ° to 105 °, preferably approximately 90 °. the conductive portions 12 have a crossing angle of approximately 90 °. though the preferred central angle and the preferred crossing angle are represented by the term “ approximately 90 °” in view of production tolerance , it is desired that the central angle and the crossing angle are ideally 90 °. the 1 period is preferably 50 to 2000 μm . the wavy line shape of each conductive portion 12 has a constant amplitude h . when an imaginary line 28 connects two adjacent intersections 24 and a line perpendicular to the imaginary line 28 extends from a crest of the wavy line shape , the amplitude h is a distance from the crest to the intersection point of the perpendicular line and the imaginary line 28 . the amplitude h is preferably 10 to 500 μm . though the conductive portion 12 has the wavy line shape with the constant amplitude h in this embodiment , adjacent two arcs 26 between the intersections 24 may have different amplitudes , and the adjacent parallel wavy line shapes may have different arc amplitudes . as schematically shown in fig4 , in the first conductive film 10 a , in a line connecting the central points c 1 and c 2 of optional adjacent two mesh shapes m 1 and m 2 disposed along the arrangement of the intersections 24 , the length la of a first line segment connecting the central point of one mesh shape m 1 and the intersection 24 is equal to the length lb of a second line segment connecting the central point of the other mesh shape m 2 and the intersection 24 . furthermore , as shown in fig4 , in a line connecting the central points c 3 and c 4 of optional adjacent two mesh shapes m 3 and m 4 disposed along the extending direction of the second thin metal wire 12 b , the length lc of a third line segment connecting the central point c 3 of one mesh shape m 3 and the first thin metal wire 12 a is equal to the length ld of a fourth line segment connecting the central point c 4 of the other mesh shape m 4 and the first thin metal wire 12 a . the first conductive film 10 a has a total light transmittance of 70 % or more but less than 99 %, which can be increased to 80 % or more or 85 % or more . thus , in the first conductive film 10 a , the conductive portions 12 hardly have a straight section , so that diffraction points are not arranged linearly on the intersections 24 of the conductive portions 12 . in addition , the adjacent parallel thin metal wires are formed in the wavy line shapes with different periods , whereby the diffraction points are discretely distributed to further reduce glare or the like caused by interference of diffracted lights . thus , an interfering light from the intersections 24 has a low intensity , and also an interfering light from the conductive portions 12 has a low intensity . the glare or the like caused by the interference of diffracted lights is thus prevented that would otherwise be caused by the mesh shapes . furthermore , since the first thin metal wires 12 a are arranged at the first pitch l 1 and the second thin metal wires 12 b are arranged at the second pitch l 2 in the first conductive film 10 a , the opening portions 14 have approximately constant opening areas , whereby the glare or the like caused by the interference of diffracted lights can be prevented on the whole surface , and significant glare or the like is not caused locally . therefore , the first conductive film 10 a is suitable for the transparent heating element 18 , which can be incorporated in a window glass ( such as a building window glass or a vehicle window glass ), a vehicle light front cover , etc . the straight section may be appropriately formed in the wavy line shape if necessary depending on the product ( such as the window glass or the vehicle light front cover ), the period or amplitude of the wavy line shape , etc . the wavy line shape may be a sine wave curve shape . in the first conductive film 10 a , the number of the arcs 26 on the circumference line of one mesh shape m is 4k ( k = 1 , 2 , 3 , . . . ). therefore , the first conductive film 10 a is capable of exhibiting a low overall surface resistance , improving heat generation efficiency in a transparent heating element , and improving power generation efficiency in a solar cell . an example of a product such as a conductive sheet ( hereinafter referred to as the first conductive sheet 100 ) using the first conductive film 10 a will be described below with reference to also fig5 to 12 . fig5 is a front view showing the first conductive sheet 100 , fig6 is a back view showing the first conductive sheet 100 , fig7 is a top view showing the first conductive sheet 100 , fig8 is a bottom view showing the first conductive sheet 100 , fig9 is a left side view showing the first conductive sheet 100 , and fig1 is a right side view showing the first conductive sheet 100 . further , fig1 is a perspective view showing the first conductive sheet 100 , and fig1 is a front view showing the use of the first conductive sheet 100 . the first conductive sheet 100 contains a transparent film substrate 16 and a wavy conductive pattern ( conductive portions ) 12 formed thereon . the design of the first conductive sheet 100 is continuously formed in the vertical and horizontal directions of the front view . in the first conductive sheet 100 , the transparent film substrate 16 is colorless and clear , and the conductive pattern ( conductive portions ) 12 has a black color . the first conductive sheet 100 can be used as a part of a defroster ( defrosting device ) or a window glass for a vehicle , etc . the first conductive sheet 100 can be used also as a heating sheet capable of heat generation by applying electric current . furthermore , the first conductive sheet 100 can be used as an electrode for a touch panel , an inorganic el device , an organic el device , or a solar cell . for example , electrodes are disposed on the opposite ends of the first conductive sheet 100 ( e . g ., the right and left ends of fig1 ), and an electric current is flowed from one electrode to the other electrode to heat the conductive pattern 12 . thus , a heating object such as a vehicle headlight covered with snow , which is brought into contact or equipped with the first conductive sheet 100 , is heated . as a result , the snow can be melted and removed from the headlight . the pitches of the conductive pattern 12 ( the dimensions l 1 and l 2 of fig5 ) may be selected within a range of 0 . 1 to 6 . 0 mm ( more preferably 0 . 3 to 6 . 0 mm ). in this example , the dimensions l 1 and l 2 are the same value of about 5 . 8 mm . the line width of the conductive pattern 12 ( the dimension d of fig5 ) is about 0 . 1 mm in this example though it may be selected within a range of 0 . 01 to 0 . 2 mm . the thickness of the transparent film substrate 16 ( the dimension t 2 of fig8 ) is about 0 . 6 mm in this example though it may be selected within a range of 0 . 01 to 2 . 0 mm . the thickness of the conductive pattern 12 ( the dimension t 1 of fig8 ) is about 0 . 1 mm in this example though it may be selected within a range of 0 . 001 to 0 . 2 mm . a conductive film according to a second embodiment ( hereinafter referred to as the second conductive film 10 b ) will be described below with reference to fig1 . as shown in fig1 , the structure of the second conductive film 10 b is approximately the same as that of the above first conductive film 10 a , but different in the following respect . thus , in the second conductive film 10 b , among adjacent parallel first thin metal wires 12 a 1 and 12 a 2 , one first thin metal wire 12 a 1 is formed in a wavy line shape containing at least one curve ( e . g ., the arc 26 ) between the intersections 24 , and the other first thin metal wire 12 a 2 is formed in a straight line shape . similarly , among adjacent parallel second thin metal wires 12 b 1 and 12 b 2 , one second thin metal wire 12 b 1 is formed in a wavy line shape containing at least one curve ( e . g ., the arc 26 ) between the intersections 24 , and the other second thin metal wire 12 b 2 is formed in a straight line shape . it should be noted that the wavy line shapes of the one first thin metal wire 12 a 1 and the one second thin metal wire 12 b 1 have 1 period of the arcs 26 between the intersections 24 . though not shown in the drawing , when the second conductive film 10 b is used in a transparent heating element 18 , first and second electrodes are disposed on the opposite ends of the second conductive film 10 b . when an electric current is flowed from the first electrode to the second electrode , the transparent heating element 18 generates heat . thus , in the second conductive film 10 b , diffraction points are not arranged linearly on the intersections 24 of the conductive portions 12 not having a straight section , whereby the mesh shapes can prevent the glare or the like caused by the interference of the diffracted lights . therefore , the second conductive film 10 b is suitable for the transparent heating element 18 that can be incorporated in a window glass ( such as a building window glass or a vehicle window glass ), a vehicle light front cover , etc . though the first thin metal wires 12 a are arranged at the first pitch l 1 in one direction and the second thin metal wires 12 b are arranged at the second pitch l 2 in the other direction in the above first conductive film 10 a and the second conductive film 10 b , the pitches may be increased or decreased locally . thus , the opening areas of the opening portions 14 may be locally changed . a local portion having a decreased pitch ( an opening portion 14 with a smaller opening area ) exhibits higher heat generation efficiency , and a local portion having an increased pitch ( an opening portion 14 with a larger opening area ) exhibits a higher light transmittance . in the case of using the transparent heating element 18 in a window glass , the pitches may be selected in each portion of the window glass such as a portion requiring rapid snow melting or a portion requiring transparency . particularly , when the transparent heating element 18 is used in a vehicle window glass ( a front window glass ), the rapid snow melting , the transparency , and a longer current pathway are required in a portion facing a driver , so that it is preferred that the local portion with an increased pitch and the local portion with a decreased pitch are arranged in combination . a conductive film according to a third embodiment ( hereinafter referred to as the third conductive film 10 c ) will be described below with reference to fig1 . as schematically shown in fig1 , the structure of the third conductive film 10 c is approximately the same as that of the above first conductive film 10 a , but different in the following respect . thus , for example , in the first thin metal wires 12 a , a number - one first thin metal wire 12 a ( 1 ) has a smallest arrangement period number of the arcs 26 ( a largest length of the arrangement period of the arcs 26 ), and the arrangement period number of the arcs 26 is increased stepwise ( the length of the arc arrangement period is reduced stepwise ) from the number - one first thin metal wire 12 a ( 1 ) to another first thin metal wire 12 a arranged in one direction . in the example of fig1 , the number - one first thin metal wire 12 a ( 1 ) has an arc arrangement period number of 1 , the number - two first thin metal wire 12 a ( 2 ) adjacent to the number - one first thin metal wire 12 a ( 1 ) in the one direction has an arc arrangement period number of 2 , and the number - three first thin metal wire 12 a ( 3 ) adjacent to the number - two first thin metal wire 12 a ( 2 ) in the one direction has an arc arrangement period number of 3 . the combinations of the wires are arranged in the one direction . the first thin metal wire 12 a adjacent to the number - one first thin metal wire 12 a ( 1 ) in the opposite direction has an arc arrangement period number of 3 . therefore , the first thin metal wire 12 a having the largest arc arrangement period number is adjacent to the first thin metal wire 12 a having the smallest arc arrangement period number . the second thin metal wires 12 b are arranged in the same manner . also in the third conductive film 10 c , the conductive portions 12 hardly have a straight section , so that diffraction points are not arranged linearly on the intersections 24 of the conductive portions 12 . in addition , the adjacent parallel thin metal wires 12 are formed in the wavy line shapes with different periods , whereby the diffraction points are discretely distributed to further reduce the glare or the like caused by the interference of diffracted lights . the number of the arcs 26 on the circumference line of one mesh shape m is 2k ( k = 1 , 2 , 3 , . . . ). therefore , though the surface resistance lowering effect of the third conductive film 10 c is lower than that of the first conductive film 10 a having the number 4k , the third conductive film 10 c is capable of improving heat generation efficiency in a transparent heating element and improving power generation efficiency in a solar cell . an example of a product such as a conductive sheet ( hereinafter referred to as the second conductive sheet 200 ) using the third conductive film 10 c will be described below with reference also to fig1 to 22 . fig1 is a front view showing the second conductive sheet 200 , fig1 is a back view showing the second conductive sheet 200 , fig1 is a top view showing the second conductive sheet 200 , fig1 is a bottom view showing the second conductive sheet 200 , fig1 is a left side view showing the second conductive sheet 200 , and fig2 is a right side view showing the second conductive sheet 200 . further , fig2 is a perspective view showing the second conductive sheet 200 , and fig2 is a front view showing the use of the second conductive sheet 200 . the second conductive sheet 200 contains a transparent film substrate 16 and a wavy conductive pattern ( conductive portions ) 12 formed thereon . the design of the second conductive sheet 200 is continuously formed in the vertical and horizontal directions of the front view . in the second conductive sheet 200 , the transparent film substrate 16 is colorless and clear , and the conductive pattern ( conductive portions ) 12 has a black color . the second conductive sheet 200 can be used as a part of a defroster ( defrosting device ) or a window glass for a vehicle , etc . the second conductive sheet 200 can be used also as a heating sheet capable of heat generation by applying electric current . furthermore , the second conductive sheet 200 can be used as an electrode for a touch panel , an inorganic el device , an organic el device , or a solar cell . for example , electrodes are disposed on the opposite ends of the second conductive sheet 200 ( e . g ., the right and left ends of fig2 ), and an electric current is flowed from one electrode to the other electrode to heat the conductive pattern 12 . thus , a heating object such as a vehicle headlight covered with snow , which is brought into contact or equipped with the second conductive sheet 200 , is heated . as a result , the snow can be melted and removed from the headlight . the pitches of the conductive pattern 12 ( the dimensions l 1 and l 2 of fig1 ) may be selected within a range of 0 . 15 to 6 . 0 mm . in this example , the dimensions l 1 and l 2 are the same value of about 5 . 8 mm . the line width of the conductive pattern 12 ( the dimension d of fig1 ) is about 0 . 1 mm in this example though it may be selected within a range of 0 . 01 to 0 . 2 mm . the thickness of the transparent film substrate 16 ( the dimension t 2 of fig1 ) is about 0 . 6 mm in this example though it may be selected within a range of 0 . 01 to 2 . 0 mm . the thickness of the conductive pattern 12 ( the dimension t 1 of fig1 ) is about 0 . 1 mm in this example though it may be selected within a range of 0 . 001 to 0 . 2 mm . a conductive film according to a fourth embodiment ( hereinafter referred to as the fourth conductive film 10 d ) will be described below with reference to fig2 . as schematically shown in fig2 , the structure of the fourth conductive film 10 d is approximately the same as that of the above third conductive film 10 c , but different in the following respect . thus , for example , in the first thin metal wires 12 a , two first thin metal wires 12 a disposed adjacently on either side of a first thin metal wire 12 a having a smallest arc arrangement period number ( a largest arc arrangement period length ) have the same arc arrangement period number , and two first thin metal wires 12 a disposed adjacently on either side of a first thin metal wire 12 a having a largest arc arrangement period number ( a smallest arc arrangement period length ) have the same arc arrangement period number . the second thin metal wires 12 b are formed in the same manner . also in the fourth conductive film 10 d , the conductive portions 12 hardly have a straight section , so that diffraction points are not arranged linearly on the intersections 24 of the conductive portions 12 . in addition , the adjacent parallel thin metal wires 12 are formed in the wavy line shapes with different periods , whereby the diffraction points are discretely distributed to further reduce the glare or the like caused by the interference of diffracted lights . in the fourth conductive film 10 d , the number of the arcs 26 on the circumference line of one mesh shape m is 4k ( k = 1 , 2 , 3 , . . . ). therefore , the fourth conductive film 10 d is capable of improving heat generation efficiency in a transparent heating element and improving power generation efficiency in a solar cell . though not shown in the drawings , for example , the pattern of the first thin metal wires 12 a may be arranged such that , calling one first thin metal wire 12 a having a smallest arc arrangement period number a number - one first thin metal wire 12 a , the arc arrangement period number of the first thin metal wire 12 a is increased stepwise from the number - one first thin metal wire 12 a in one direction in the same manner as in the third conductive film 10 c , and the pattern of the second thin metal wires 12 b may be arranged such that two second thin metal wires 12 b disposed adjacently on either side of a second thin metal wire 12 b having a smallest arc arrangement period number have the same arc arrangement period number and two second thin metal wires 12 b disposed adjacently on either side of a second thin metal wire 12 b having a largest arc arrangement period number have the same arc arrangement period number in the same manner as in the fourth conductive film 10 d . of course , conversely , the first thin metal wires 12 a may be patterned in the same manner as in the fourth conductive film 10 d , and the second thin metal wires 12 b may be patterned in the same manner as in the third conductive film 10 c . a conductive film according to a fifth embodiment ( hereinafter referred to as the fifth conductive film 10 e ) will be described below with reference to fig2 . as schematically shown in fig2 , the structure of the fifth conductive film 10 e is approximately the same as that of the above first conductive film 10 a , but different in the following respect . thus , the conductive portions 12 have a wavy line shape with a constant period . in the example of fig2 , 1 period of the arcs are arranged between the intersections 24 . in the fifth conductive film 10 e , the first line segment length la is equal to the second line segment length lb , and the third line segment length lc is equal to the fourth line segment length ld , as in the first conductive film 10 a . however , as shown in fig2 , a pair of optional tangent lines , which are positioned on the circumference line of each mesh shape m symmetrically about the central point c of the mesh shape m , are parallel to each other . specifically , in fig2 , for example , a pair of first tangent lines ( 1 )( 1 ), a pair of second tangent lines ( 2 )( 2 ), and a pair of third tangent lines ( 3 )( 3 ) are parallel to each other , respectively , and have different tangent directions . in general , a light is highly refracted and diffracted in a tangent direction . in the fifth conductive film 10 e , a light can be refracted and diffracted in a large number of the different tangent directions to reduce the significant glare . furthermore , in the fifth conductive film 10 e , the opening portions 14 have approximately constant opening areas , whereby the glare or the like caused by the interference of diffracted lights can be prevented on the whole surface , and the significant glare or the like is not caused locally . in addition , in the fifth conductive film 10 e , the number of the arcs 26 on the circumference line of one mesh shape m is 4k ( k = 1 , 2 , 3 , . . . ). therefore , the fifth conductive film 10 e is capable of improving heat generation efficiency in a transparent heating element and improving power generation efficiency in a solar cell . a conductive film according to a sixth embodiment ( hereinafter referred to as the sixth conductive film 10 f ) will be described below with reference to fig2 . as schematically shown in fig2 , the structure of the sixth conductive film 10 f is approximately the same as that of the above fifth conductive film 10 e . thus , in the sixth conductive film 10 f , the first line segment length la is equal to the second line segment length lb as in the fifth conductive film 10 e . in addition , a pair of optional tangent lines , which are positioned on the circumference line of each mesh shape m symmetrically about the central point c of the mesh shape m , are parallel to each other . however , unlike the fifth conductive film 10 e , in a line connecting the central points c 3 and c 4 of two optional mesh shapes m 3 and m 4 adjacently disposed along the extending direction of the second thin metal wire 12 b , the length lc of a third line segment connecting the central point c 3 of one mesh shape m 3 and the first thin metal wire 12 a is different from the length ld of a fourth line segment connecting the central point c 4 of the other mesh shape m 4 and the first thin metal wire 12 a . in the example of fig2 , the length lc is larger than the length ld . it should be noted that the intersections 24 are at a distance of 0 . 5 periods in this example . as in the fifth conductive film 10 e , also in the sixth conductive film 10 f , a light can be refracted and diffracted in a large number of the different tangent directions to reduce the significant glare . furthermore , the opening portions 14 have approximately constant opening areas , whereby the glare or the like caused by the interference of diffracted lights can be prevented on the whole surface , and the significant glare or the like is not caused locally . a conductive film according to a seventh embodiment ( hereinafter referred to as the seventh conductive film 10 g ) will be described below with reference to fig2 . as schematically shown in fig2 , the structure of the seventh conductive film 10 g is approximately the same as that of the above sixth conductive film 10 f . thus , in the seventh conductive film 10 g , the distance la is equal to the distance lb , the distance lc is different from the distance ld , and a pair of optional tangent lines , which are positioned on the circumference line of each mesh shape m symmetrically about the central point c of the mesh shape m , are parallel to each other . the seventh conductive film 10 g is different from the sixth conductive film 10 f in that 1 . 5 periods of the arcs are arranged between the intersections 24 . also in the seventh conductive film 10 g , a light can be refracted and diffracted in a large number of different directions to reduce the significant glare . furthermore , the opening portions 14 have approximately constant opening areas , whereby the glare or the like caused by the interference of diffracted lights can be prevented on the whole surface , and the significant glare or the like is not caused locally . a conductive film according to an eighth embodiment ( hereinafter referred to as the eighth conductive film 10 h ) will be described below with reference to fig2 . as schematically shown in fig2 , the structure of the eighth conductive film 10 h is approximately the same as that of the above sixth conductive film 10 f . thus , in the eighth conductive film 10 h , the distance la is equal to the distance lb , the distance lc is different from the distance ld , and a pair of optional tangent lines , which are positioned on the circumference line of each mesh shape m symmetrically about the central point c of the mesh shape m , are parallel to each other . the eighth conductive film 10 h is different from the sixth conductive film 10 f in that the arc arrangement period between one intersection 24 and a first intersection 24 a adjacently disposed at one side of the one intersection 24 along the extending direction of the first thin metal wire 12 a is different from the arc arrangement period between the one intersection 24 and a second intersection 24 b adjacently disposed at the other side of the one intersection 24 . in the example of fig2 , in the arc arrangement , the one intersection 24 and the first intersection 24 a are at a distance of 0 . 5 periods , and the one intersection 24 and the second intersection 24 b are at a distance of 1 . 5 periods . in addition , the arc arrangement period between the one intersection 24 and a third intersection 24 c adjacently disposed at one side of the one intersection 24 along the extending direction of the second thin metal wire 12 b is different from the arc arrangement period between the one intersection 24 and a fourth intersection 24 d adjacently disposed at the other side of the one intersection 24 . in the example of fig2 , in the arc arrangement , the one intersection 24 and the third intersection 24 c are at a distance of 1 . 5 periods , and the one intersection 24 and the fourth intersection 24 d are at a distance of 0 . 5 periods . also in the eighth conductive film 10 h , a light can be refracted and diffracted in a large number of different directions to reduce the significant glare . in the fifth to eighth conductive films 10 e to 10 h as well as the first conductive film 10 a , the number of the arcs 26 on the circumference line of one mesh shape m is 4k ( k = 1 , 2 , 3 , . . . ). therefore , the films are capable of exhibiting a low overall surface resistance , improving heat generation efficiency in a transparent heating element , and improving power generation efficiency in a solar cell . then , several methods for producing the first to eighth conductive films 10 a to 10 h ( hereinafter collectively referred to as the conductive film 10 ) will be described below with reference to fig2 a to 31 . in the first production method , a photosensitive silver salt layer is formed , exposed , developed , and fixed on the transparent film substrate 16 to form metallic silver portions . the metallic silver portions and a conductive metal disposed thereon are utilized for forming the mesh pattern 22 . specifically , as shown in fig2 a , the transparent film substrate 16 is coated with a photosensitive silver salt layer 34 containing a mixture of a gelatin 33 and a silver halide 31 ( e . g ., silver bromide particles , silver chlorobromide particles , or silver iodobromide particles ). though the silver halide 31 is exaggeratingly shown by points in fig2 a to 28c to facilitate understanding , the points do not represent the size , concentration , etc . then , as shown in fig2 b , the photosensitive silver salt layer 34 is subjected to an exposure treatment for forming the mesh pattern 22 . when an optical energy is applied to the silver halide 31 , the silver halide 31 is exposed to generate invisible minute silver nuclei , referred to as a latent image . as shown in fig2 c , the photosensitive silver salt layer 34 is subjected to a development treatment for converting the latent image to an image visible to the naked eye . specifically , the photosensitive silver salt layer 34 having the latent image is developed using a developer , which is an alkaline or acidic solution , generally an alkaline solution . in the development treatment , using the latent image silver nuclei as catalyst cores , silver ions from the silver halide particles or the developer are reduced to metallic silver by a reducing agent in the developer ( referred to as a developing agent ). as a result , the latent image silver nuclei are grown to form a visible silver image ( developed silver 35 ). the photosensitive silver halide 31 remains in the photosensitive silver salt layer 34 after the development treatment . as shown in fig2 d , the silver halide 31 is removed by a fixation treatment using a fixer , which is an acidic or alkaline solution , generally an acidic solution . after the fixation treatment , metallic silver portions 36 are formed in exposed areas , and light - transmitting portions 38 containing only the gelatin 33 are formed in unexposed areas . thus , the combination of the metallic silver portions 36 and the light - transmitting portions 38 is formed on the transparent film substrate 16 . in a case where silver bromide is used as the silver halide 31 and a thiosulfate salt is used in the fixation treatment , a reaction represented by the following formula proceeds in the treatment . agbr ( solid )+ 2 s 2 o 3 ions → ag ( s 2 o 3 ) 2 ( readily - water - soluble complex ) two thiosulfate s 2 o 3 ions and one silver ion in the gelatin 33 ( from agbr ) are reacted to generate a silver thiosulfate complex . the silver thiosulfate complex has a high water solubility , and thereby is eluted from the gelatin 33 . as a result , the developed silvers 35 are fixed and remain as the metallic silver portions 36 . thus , the latent image is reacted with the reducing agent to deposit the developed silvers 35 in the development treatment , and the residual silver halide 31 , not converted to the developed silvers 35 , is eluted into water in the fixation treatment . the treatments are described in detail in t . h . james , “ the theory of the photographic process , 4th ed .”, macmillian publishing co ., inc ., ny , chapter 15 , pp . 438 - 442 , 1977 . the development treatment is generally carried out using the alkaline solution . the alkaline solution used in the development treatment may be mixed into the fixer ( generally an acidic solution ), whereby the activity of the fixer may be disadvantageously changed in the fixation treatment . further , the developer may remain on the film after removing the film from the development bath , whereby an undesired development reaction may be accelerated by the developer . thus , it is preferred that the photosensitive silver salt layer 34 is neutralized or acidified by a quencher such as an acetic acid solution after the development treatment before the fixation treatment . as shown in fig2 e , a conductive metal 40 may be disposed only on the metallic silver portions 36 by a plating treatment ( such as an electroless plating treatment , an electroplating treatment , or a combination thereof ), etc . in this case , the mesh pattern 22 is formed of the metallic silver portions 36 on the transparent film substrate 16 and the conductive metal 40 disposed on the metallic silver portions 36 . the difference between the above mentioned process using the photosensitive silver salt layer 34 ( a silver salt photography technology ) and a process using a photoresist ( a resist technology ) will be described below . in the resist technology , a photopolymerization initiator absorbs a light in an exposure treatment to initiate a reaction , a photoresist film ( a resin ) per se undergoes a polymerization reaction to increase or decrease the solubility in a developer , and the resin in an exposed or unexposed area is removed in a development treatment . the developer liquid used in the resist technology may be an alkaline solution free of reducing agents , in which an unreacted resin component can be dissolved . on the other hand , as described above , in the silver salt photography technology according to the present invention , the minute silver nuclei ( the so - called latent image ) are formed from the silver ion and a photoelectron generated in the silver halide 31 exposed in the exposure treatment . the latent image silver nuclei are grown to form the visible silver image in the development treatment using the developer , which must contain the reducing agent ( the developing agent ). thus , the resist technology and the silver salt photography technology are greatly different in the reactions in the exposure and development treatments . in the development treatment of the resist technology , the unpolymerized resin portion in the exposed or unexposed area is removed . on the other hand , in the development treatment of the silver salt photography technology , using the latent image as the catalyst core , the reduction reaction is conducted by the reducing agent contained in the developer ( the developing agent ), and the developed silver 35 is grown into a visible size . the gelatin 33 in the unexposed area is not removed . thus , the resist technology and the silver salt photography technology are greatly different also in the reactions in the development treatments . the silver halide 31 contained in the gelatin 33 in the unexposed area is eluted in the following fixation treatment , and the gelatin 33 is not removed . the main reaction component ( the main photosensitive component ) is the silver halide in the silver salt photography technology , while it is the photopolymerization initiator in the resist technology . further , in the development treatment , the binder ( the gelatin 33 ) remains in the silver salt photography technology , while it is removed in the resist technology . the resist technology and the silver salt photography technology are greatly different in these points . a mask used in the exposure treatment of the photosensitive silver salt layer 34 may have a mask pattern corresponding to the mesh pattern 22 of the conductive portions 12 having the wavy line shape containing at least one curve between the intersections 24 . in another method ( the second production method ), for example , as shown in fig2 a , a photoresist film 44 is formed on a copper foil 42 disposed on the transparent film substrate 16 , and the photoresist film 44 is exposed and developed to form a resist pattern 46 . as shown in fig2 b , the copper foil 42 exposed from the resist pattern 46 is etched to form the mesh pattern 22 . in this method , a mask used in the exposure treatment of the photoresist film 44 may have a mask pattern corresponding to the mesh pattern 22 . in the third production method , as shown in fig3 a , a paste 48 containing fine metal particles is printed on the transparent film substrate 16 . as shown in fig3 b , the printed paste 48 may be plated with a metal 50 to form the mesh pattern 22 . in the fourth production method , as shown in fig3 , the mesh pattern 22 may be printed on the transparent film substrate 16 by using a screen or gravure printing plate . a particularly preferred method of forming a thin conductive metal film using a photographic photosensitive silver halide material for the conductive film 10 of this embodiment will be mainly described below . as described above , the conductive film 10 of this embodiment may be produced as follows . a photosensitive material having the transparent film substrate 16 and thereon a photosensitive silver halide - containing emulsion layer is exposed and developed , whereby the metallic silver portions 36 and the light - transmitting portions 38 are formed in the exposed areas and the unexposed areas respectively . the metallic silver portions 36 may be subjected to a physical development treatment and / or a plating treatment to deposit the conductive metal 40 thereon . the method for forming the conductive film 10 of the embodiment includes the following three processes , depending on the photosensitive materials and development treatments . ( 1 ) a process comprising subjecting a photosensitive black - and - white silver halide material free of physical development nuclei to a chemical or thermal development , to form the metallic silver portions 36 on the photosensitive material . ( 2 ) a process comprising subjecting a photosensitive black - and - white silver halide material having a silver halide emulsion layer containing physical development nuclei to a solution physical development , to form the metallic silver portions 36 on the photosensitive material . ( 3 ) a process comprising subjecting a stack of a photosensitive black - and - white silver halide material free of physical development nuclei and an image - receiving sheet having a non - photosensitive layer containing physical development nuclei to a diffusion transfer development , to form the metallic silver portions 36 on the non - photosensitive image - receiving sheet . in the process of ( 1 ), an integral black - and - white development procedure is used to form a transmittable conductive film such as an electromagnetic - shielding film or a light - transmitting conductive film on the photosensitive material . the resulting silver is a chemically or thermally developed silver containing a high - specific surface area filament , and thereby shows a high activity in the following plating or physical development treatment . in the process of ( 2 ), the silver halide particles are melted around the physical development nuclei and deposited on the nuclei in the exposed areas , to form a transmittable conductive film such as a light - transmitting electromagnetic - shielding film or a light - transmitting conductive film on the photosensitive material . also in this process , an integral black - and - white development procedure is used . though high activity can be achieved since the silver halide is deposited on the physical development nuclei in the development , the developed silver has a spherical shape with small specific surface . in the process of ( 3 ), the silver halide particles are melted in unexposed areas , and diffused and deposited on the development nuclei of the image - receiving sheet , to form a transmittable conductive film such as an electromagnetic - shielding film or a light - transmitting conductive film on the sheet . in this process , a so - called separate - type procedure is used , and the image - receiving sheet is peeled off from the photosensitive material . a negative or reversal development treatment can be used in the processes . in the diffusion transfer development , the negative development treatment can be carried out using an auto - positive photosensitive material . the chemical development , thermal development , solution physical development , and diffusion transfer development have the meanings generally known in the art , and are explained in common photographic chemistry texts such as shin - ichi kikuchi , “ shashin kagaku ( photographic chemistry )”, kyoritsu shuppan co ., ltd ., 1955 and c . e . k . mees , “ the theory of photographic processes , 4th ed .”, mcmillan , 1977 . a liquid treatment is generally used in the present invention , and also a thermal development treatment can be utilized . for example , techniques described in japanese laid - open patent publication nos . 2004 - 184693 , 2004 - 334077 , and 2005 - 010752 , and japanese patent application nos . 2004 - 244080 and 2004 - 085655 can be used in the present invention . the transparent film substrate 16 of the photosensitive material used in the production method of the embodiment may be a plastic film , etc . in this embodiment , it is preferred that the plastic film is a polyethylene terephthalate film or a triacetyl cellulose ( tac ) film from the viewpoints of light transmittance , heat resistance , handling , and cost . in a transparent heating element for a window glass , the transparent film substrate 16 preferably has a high light transmittance . in this case , the total visible light transmittance of the plastic film is preferably 70 % to 100 %, more preferably 85 % to 100 %, particularly preferably 90 % to 100 %. the plastic film may be colored as long as it does not interfere with the advantageous effects of the present invention . in the photosensitive material , a protective layer may be formed on the emulsion layer to be hereinafter described . the protective layer used in this embodiment contains a binder such as a gelatin or a high - molecular polymer , and is formed on the photosensitive emulsion layer to improve the scratch prevention or mechanical property . the photosensitive material used in the production method of this embodiment preferably has the transparent film substrate 16 and thereon the emulsion layer containing the silver salt as a light sensor ( the silver salt - containing layer ). the emulsion layer according to the embodiment may contain a dye , a binder , a solvent , etc . in addition to the silver salt if necessary . the ratio of the dye to the total solid contents in the emulsion layer is preferably 0 . 01 % to 10 % by mass , more preferably 0 . 1 % to 5 % by mass , in view of the effects such as the irradiation prevention effect and the sensitivity reduction due to the excess addition . the silver salt used in this embodiment is preferably an inorganic silver salt such as a silver halide . it is particularly preferred that the silver salt is used in the form of particles for the photographic photosensitive silver halide material . the silver halide has an excellent light sensing property . the silver halide , preferably used in the photographic emulsion of the photographic photosensitive silver halide material , will be described below . in this embodiment , the silver halide is preferably used as a light sensor . silver halide technologies for photographic silver salt films , photographic papers , print engraving films , emulsion masks for photomasking , and the like may be utilized in this embodiment . the silver halide may contain a halogen element of chlorine , bromine , iodine , or fluorine , and may contain a combination of the elements . for example , the silver halide preferably contains agcl , agbr , or agi , more preferably contains agbr or agcl , as a main component . also silver chlorobromide , silver iodochlorobromide , or silver iodobromide is preferably used as the silver halide . the silver halide is further preferably silver chlorobromide , silver bromide , silver iodochlorobromide , or silver iodobromide , most preferably silver chlorobromide or silver iodochlorobromide having a silver chloride content of 50 mol % or more . the term “ the silver halide contains agbr ( silver bromide ) as a main component ” means that the mole ratio of bromide ion is 50 % or more in the silver halide composition . the silver halide particle containing agbr as a main component may contain iodide or chloride ion in addition to the bromide ion . the silver halide emulsion , used as a coating liquid for the emulsion layer in this embodiment , may be prepared by a method described in p . glafkides , “ chimie et physique photographique ”, paul montel , 1967 , g . f . dufin , “ photographic emulsion chemistry ”, the forcal press , 1966 , v . l . zelikman , et al ., “ making and coating photographic emulsion ”, the forcal press , 1964 , etc . the binder may be used in the emulsion layer to uniformly disperse the silver salt particles and to help the emulsion layer adhere to a support . in the present invention , the binder may contain a water - insoluble or water - soluble polymer , and preferably contains a water - soluble polymer . examples of the binders include gelatins , polyvinyl alcohols ( pva ), polyvinyl pyrolidones ( pvp ), polysaccharides such as starches , celluloses and derivatives thereof , polyethylene oxides , polysaccharides , polyvinylamines , chitosans , polylysines , polyacrylic acids , polyalginic acids , polyhyaluronic acids , and carboxycelluloses . the binders show a neutral , anionic , or cationic property depending on the ionicity of a functional group . the solvent used for forming the emulsion layer is not particularly limited , and examples thereof include water , organic solvents ( e . g . alcohols such as methanol , ketones such as acetone , amides such as formamide , sulfoxides such as dimethyl sulfoxide , esters such as ethyl acetate , ethers ), ionic liquids , and mixtures thereof . in the present invention , the ratio of the solvent to the total of the silver salt , the binder , and the like in the emulsion layer is 30 % to 90 % by mass , preferably 50 % to 80 % by mass . the treatments for forming the conductive film will be described below . in this embodiment , though the mesh pattern 22 may be formed by a printing process , it is formed by the exposure and development treatments , etc . in another process . a photosensitive material having the transparent film substrate 16 and thereon the silver salt - containing layer formed thereon or a photosensitive material coated with a photopolymer for photolithography is subjected to the exposure treatment . an electromagnetic wave may be used in the exposure . for example , the electromagnetic wave may be a light such as a visible light or an ultraviolet light , or a radiation ray such as an x - ray . the exposure may be carried out using a light source having a wavelength distribution or a specific wavelength . in this embodiment , the emulsion layer is subjected to the development treatment after the exposure . common development treatment technologies for photographic silver salt films , photographic papers , print engraving films , emulsion masks for photomasking , and the like may be used in the present invention . a developer for the development treatment is not particularly limited , and may be a pq developer , an mq developer , an maa developer , etc . examples of commercially available developers usable in the present invention include cn - 16 , cr - 56 , cp45x , fd - 3 , and papitol available from fujifilm corporation , c - 41 , e - 6 , ra - 4 , d - 19 , and d - 72 available from eastman kodak company , and developers contained in kits thereof . the developer may be a lith developer . in the present invention , the development process may include a fixation treatment for removing the silver salt in the unexposed area to stabilize the material . fixation treatment technologies for photographic silver salt films , photographic papers , print engraving films , emulsion masks for photomasking , and the like may be used in the present invention . in the fixation treatment , the fixation temperature is preferably about 20 ° c . to 50 ° c ., more preferably 25 ° c . to 45 ° c . the fixation time is preferably 5 seconds to 1 minute , more preferably 7 to 50 seconds . the amount of the fixer is preferably 600 ml / m 2 or less , more preferably 500 ml / m 2 or less , particularly preferably 300 ml / m 2 or less , per 1 m 2 of the photosensitive material to be treated . the developed and fixed photosensitive material is preferably subjected to a water washing treatment or a stabilization treatment . the amount of water used in the water washing or stabilization treatment is generally 20 l or less , and may be 3 l or less , per 1 m 2 of the photosensitive material . the photosensitive material may be washed with storage water , and thus the water amount may be 0 . the ratio of the metallic silver contained in the exposed area after the development to the silver contained in this area before the exposure is preferably 50 % or more , more preferably 80 % or more by mass . when the ratio is 50 % or more by mass , a high conductivity can be achieved . in this embodiment , the tone ( gradation ) obtained by the development is preferably more than 4 . 0 , though not particularly restrictive . when the tone is more than 4 . 0 after the development , the conductivity of the conductive metal portion can be increased while maintaining high transmittance of the light - transmitting portion . for example , the tone of 4 . 0 or more can be achieved by doping with rhodium or iridium ion . in this embodiment , to increase the conductivity of the metallic silver portion formed by the above exposure and development treatments , conductive metal particles may be deposited thereon by a physical development treatment and / or a plating treatment . in the present invention , the conductive metal particles may be deposited on the metallic silver portion by only one of the physical development and plating treatments or by the combination of the treatments . the metallic silver portion , subjected to the physical development treatment and / or the plating treatment in this manner , is referred to as the conductive metal portion . in this embodiment , the physical development is such a process that metal ions such as silver ions are reduced by a reducing agent , whereby metal particles are deposited on a metal or metal compound core . such physical development has been used in the fields of instant b & amp ; w film , instant slide film , printing plate production , etc ., and the technologies can be used in the present invention . the physical development may be carried out at the same time as the above development treatment after the exposure , and may be carried out after the development treatment separately . in this embodiment , the plating treatment may contain electroless plating ( such as chemical reduction plating or displacement plating ), electrolytic plating , or a combination thereof . known electroless plating technologies for printed circuit boards , etc . may be used in this embodiment . the electroless plating is preferably electroless copper plating . in this embodiment , the metallic silver portion formed by the development treatment or the conductive metal portion formed by the physical development treatment and / or the plating treatment is preferably subjected to an oxidation treatment . for example , by the oxidation treatment , a small amount of a metal deposited on the light - transmitting portion can be removed , so that the transmittance of the light - transmitting portion can be increased to approximately 100 %. in this embodiment , the line width of the conductive metal portion may be selected within a range of 5 m to 200 μm ( 0 . 2 mm ). in the case of using the conductive metal portion for a transparent heating element , the portion may have a part with a line width of more than 20 μm for the purpose of ground connection , etc . the line width is preferably 5 to 50 μm , more preferably 5 to 30 μm , most preferably 10 to 25 μm . the line distance is preferably 50 to 500 μm , more preferably 200 to 400 μm , most preferably 250 to 350 μm . in this embodiment , the opening ratio of the conductive metal portion is preferably 85 % or more , more preferably 90 % or more , most preferably 95 % or more , in view of the visible light transmittance . the opening ratio is the ratio of the light - transmitting portions other than the metal portions in the mesh pattern 22 to the whole . for example , a square lattice mesh having a line width of 15 μm and a pitch of 300 μm has an opening ratio of 90 %. in this embodiment , the light - transmitting portion is a portion having light transmittance , other than the conductive metal portions in the conductive film 10 . the transmittance of the light - transmitting portion , which is herein a minimum transmittance value in a wavelength region of 380 to 780 nm obtained neglecting the light absorption and reflection of the transparent film substrate 16 , is 90 % or more , preferably 95 % or more , more preferably 97 % or more , further preferably 98 % or more , most preferably 99 % or more . in this embodiment , it is preferred that the mesh pattern 22 has a continuous structure with a length of 3 m or more from the viewpoint of maintaining a high productivity of the conductive film 10 . as the length of the continuous structure of the mesh pattern 22 is increased , this effect is further improved . thus , in this case , the production loss of a transparent heating element can be advantageously reduced . the long roll of the mesh pattern 22 , which contains the conductive portions 12 formed in the wavy line shape having at least one curve between the intersections 24 , may be printing - exposed by a surface exposure method of irradiating the roll with a uniform light through a patterned mask or a scanning exposure method of irradiating the roll with a laser beam while transporting . when an excessively large number of grids of the mesh pattern 22 ( the mesh shapes m ) are continuously printed , the roll of the mesh pattern 22 is disadvantageous in large diameter , heavy weight , and that high pressure is applied to the roll center to cause adhesion or deformation , etc . therefore , the length of the mesh pattern 22 is preferably 2000 m or less . the length is preferably 3 m or more , more preferably 100 to 1000 m , further preferably 200 to 800 m , most preferably 300 to 500 m . the thickness of the transparent film substrate 16 may be selected for example within a range of 0 . 01 to 2 . 0 mm . in view of the above described weight increase , adhesion , deformation , etc . caused in the roll , the thickness of the transparent film substrate 16 is preferably 200 μm or less , more preferably 20 to 180 μm , most preferably 50 to 120 μm . in this embodiment , for example , in the first conductive film 10 a shown in fig1 , it is preferred that an imaginary line connecting the intersections 24 of the first thin metal wire 12 a is parallel to the adjacent imaginary line within an error of plus or minus 2 °. the scanning exposure with the optical beam is preferably carried out using light sources arranged on a line in a direction substantially perpendicular to the transporting direction , or using a rotary polygon mirror . in this case , the optical beam has to undergo binary or more intensity modulation , and dots are continuously formed into a line pattern . because each fine wire is composed of the continuous dots , a fine 1 - dot wire has a steplike edge shape . the width of each fine wire is a length in the narrowest part . in this embodiment , the mesh pattern 22 is tilted preferably at 30 ° to 60 °, more preferably at 40 ° to 50 °, most preferably at 43 ° to 47 °, against the transporting direction . in general , it is difficult to prepare a mask for forming a mesh pattern tilted at about 45 ° against the frame , and this is likely to result in uneven pattern , increased cost , etc . in contrast , in the above method according to the present invention , the pattern unevenness is reduced at the tilt angle of around 45 °. thus , the method of the embodiment is more effective as compared with patterning methods using masking exposure photolithography or screen printing . in the conductive film 10 of this embodiment , the thickness of the transparent film substrate 16 may be selected within a range of 0 . 01 to 2 . 0 mm as described above . the thickness is preferably 5 to 200 μm , more preferably 30 to 150 μm . when the thickness is 5 to 200 μm , a desired visible light transmittance can be obtained , and the transparent film substrate 16 can be easily handled . the thickness of the metallic silver portion 36 formed on the support before the physical development treatment and / or the plating treatment may be appropriately selected by controlling the thickness of the coating liquid for the silver salt - containing layer applied to the transparent film substrate 16 . the thickness of the metallic silver portion 36 may be selected within a range of 0 . 001 to 0 . 2 mm , and is preferably 30 μm or less , more preferably 20 μm or less , further preferably 0 . 01 to 9 μm , most preferably 0 . 05 to 5 μm . the metallic silver portion 36 is preferably formed in a patterned shape . the metallic silver portion 36 may have a monolayer structure or a multilayer structure containing two or more layers . in a case where the metallic silver portion 36 has a patterned multilayer structure containing two or more layers , the layers may have different wavelength color sensitivities . in this case , different patterns can be formed in the layers by using exposure lights with different wavelengths . in the case of using the conductive film 10 in a transparent heating element , the conductive metal portion preferably has a smaller thickness . as the thickness is reduced , the viewing angle of a window glass using the element is increased , and the heat generation efficiency is improved . thus , the thickness of the layer of the conductive metal 40 on the conductive metal portion is preferably less than 9 μm , more preferably 0 . 1 μm or more but less than 5 μm , further preferably 0 . 1 μm or more but less than 3 μm . in this embodiment , the thickness of the metallic silver portion 36 can be controlled by changing the coating thickness of the silver salt - containing layer , and the thickness of the conductive metal particle layer can be controlled in the physical development and / or the plating treatment , whereby the conductive film 10 having a thickness of less than 5 μm ( preferably less than 3 μm ) can be easily produced . in conventional etching methods , most of a thin metal film must be removed and discarded by etching . in contrast , in this embodiment , the pattern containing only a minimal amount of the conductive metal can be formed on the transparent film substrate 16 . thus , only the minimal amount of the metal is required , so that production costs and metal waste amount can be advantageously reduced . the conductive film 10 of the embodiment may be bonded to a window glass , etc . by an adhesive layer . the adhesive layer preferably contains an adhesive having a refractive index of 1 . 40 to 1 . 70 . this is because visible light transmittance deterioration can be prevented by reducing the refractive index difference between the adhesive and the transparent substrate such as the plastic film . when the adhesive has a refractive index of 1 . 40 to 1 . 70 , the visible light transmittance deterioration can be advantageously reduced . the present invention will be described more specifically below with reference to examples 1 and 2 . materials , amounts , ratios , treatment contents , treatment procedures , and the like , used in examples 1 and 2 , may be appropriately changed without departing from the scope of the present invention . the following specific examples are therefore to be considered in all respects as illustrative and not restrictive . an emulsion containing an aqueous medium , a gelatin , and silver iodobromochloride particles was prepared . the amount of the gelatin was 10 . 0 g per 60 g of ag , and the silver iodobromochloride particles had an i content of 0 . 2 moil , a br content of 40 moil , and an average spherical equivalent diameter of 0 . 1 μm . k3rh2br9 and k2ircl6 were added to the emulsion at a concentration of 10 − 7 mol / mol - silver to dope the silver bromide particles with rh and ir ions . na2pdcl4 was further added to the emulsion , and the resultant emulsion was subjected to gold - sulfur sensitization using chlorauric acid and sodium thiosulfate . the emulsion and a gelatin hardening agent were applied to a polyethylene terephthalate ( pet ) such that the amount of the applied silver was 1 g / m 2 . the ag / gelatin volume ratio was 1 / 2 . the pet support had a width of 30 cm , and the emulsion was applied thereto into a width of 25 cm and a length of 20 m . the both end portions having a width of 3 cm of the pet support were cut off to obtain a roll photosensitive silver halide material having a width of 24 cm . the photosensitive silver halide material was exposed by using a continuous exposure apparatus . in the apparatus , exposure heads using a dmd ( a digital mirror device ) according to an embodiment of japanese laid - open patent publication no . 2004 - 1244 were arranged into a width of 25 cm . the exposure heads and exposure stages were arranged on a curved line to concentrate laser lights onto the photosensitive layer of the photosensitive material . further , in the apparatus , a feeding mechanism and a winding mechanism for the photosensitive material were disposed , and a buffering bend was formed such that the speed in the exposure part was not affected by change of the exposure surface tension , and feeding and winding speeds . the light for the exposure had a wavelength of 400 nm and a beam shape of approximately 12 - μm square , and the output of the laser light source was 100 μj . the photosensitive material was exposed continuously in a pattern shown in table 1 with a width of 24 cm and a length of 10 m . the exposure was carried out under the following conditions to print a mesh pattern 22 . the periods of wavy line shapes between intersections 24 in the mesh pattern 22 , the first pitch l 1 ( the pitch of first thin metal wires 12 a ), the second pitch l 2 ( the pitch of second thin metal wires 12 b ) are shown in table 1 . the mesh pattern 22 was formed on the photosensitive layer by an exposure method using two exposure heads in combination . by using the first exposure head , the photosensitive layer is irradiated with a constant laser beam while reciprocating the beam in the direction perpendicular to the direction of transporting the layer , to draw an exposure pattern ( for forming the first thin metal wires 12 a ) on the layer . thus , the pattern is drawn by the beam at a tilt angle of 45 ° in accordance with the ratio of the photosensitive layer transporting speed and the head reciprocating speed in the perpendicular direction . after the beam reaches an end of the photosensitive layer , the pattern is drawn at the reversed angle depending on the reciprocal motion of the head . specifically , in example 1 , an exposure pattern for forming the first thin metal wires 12 a shown in fig1 was drawn . in example 2 , an exposure pattern for forming the first thin metal wires 12 a shown in fig4 was drawn . by using the second exposure head , in the same manner as in the first exposure head , the photosensitive layer is irradiated with a constant laser beam while reciprocating the beam in the direction perpendicular to the direction of transporting the layer , to draw an exposure pattern ( for forming the second thin metal wires 12 b ) on the layer . the motion start point of the second exposure head is different from that of the first exposure head by 180 degrees or a multiple of 180 degrees . thus , when the first exposure head is moved obliquely from one end of the photosensitive layer , the second exposure head is moved obliquely from the other end in the opposite direction , so that the mesh pattern 22 is formed . specifically , in example 1 , an exposure pattern for forming the second thin metal wires 12 b shown in fig1 was drawn . in example 2 , an exposure pattern for forming the second thin metal wires 12 b shown in fig4 was drawn . the exposed photosensitive material was treated with the above treatment agents under the following conditions using an automatic processor fg - 710pts manufactured by fujifilm corporation . a development treatment was carried out at 35 ° c . for 30 seconds , a fixation treatment was carried out at 34 ° c . for 23 seconds , and then a water washing treatment was carried out for 20 seconds at a water flow rate of 5 l / min . the running conditions were such that the amount of the treated photosensitive material was 100 m 2 / day , the replenishment amount of the developer was 500 ml / m 2 , the replenishment amount of the fixer was 640 ml / m 2 , and the treatment period was 3 days . it was confirmed that a copper pattern had a line width of 12 μm and a pitch of 300 μm after a plating treatment . the material was subjected to an electroless copper plating treatment at 45 ° c . using an electroless cu plating solution having a ph of 12 . 5 , containing 0 . 06 mol / l of copper sulfate , 0 . 22 mol / l of formalin , 0 . 12 mol / l of triethanolamine , 100 ppm of a polyethylene glycol , 50 ppm of yellow prussiate of potash , and 20 ppm of α , α ′- bipyridine . the material was then subjected to an oxidation treatment using an aqueous solution containing 10 ppm of fe ( iii ) ion , to produce each conductive film sample . as shown in table 1 , in example 1 ( see fig1 ), one first thin metal wires 12 a 1 and one second thin metal wires 12 b 1 had 1 period of the wavy line shape between the intersections 24 , the other first thin metal wires 12 a 2 and the other second thin metal wires 12 b 2 had 2 periods of the wavy line shape between the intersections 24 , the first pitch l 1 and the second pitch l 2 were 400 μm , and the line width h of the conductive portions 12 was 18 μm . in example 2 ( see fig4 ), one first thin metal wires 12 a 1 and one second thin metal wires 12 b 1 had 1 period of the wavy line shape between the intersections 24 , the first pitch l 1 and the second pitch l 2 were 400 μm , and the line width h of the conductive portions 12 was 18 μm . in each conductive film 10 , the surface resistivity values of optionally selected 10 areas were measured by loresta gp ( model no . mcp - t610 ) manufactured by dia instruments co ., ltd . utilizing an in - line four - probe method ( asp ), and the average of the measured values was obtained to evaluate the surface resistivity uniformity . a transparent plate for supporting each conductive film 10 was composed of a glass with a thickness of 5 mm representing a window glass . the conductive film was attached to the transparent plate and placed in a dark room . a light was emitted from an incandescent lamp ( 40 - watt bulb ) placed at a distance of 3 m from the transparent plate . the light transmitted through the transparent plate was visually observed to evaluate the glare caused by interference of a diffracted light . the glare observation was carried out in a position at a distance of 1 m from the surface of the transparent plate ( the surface on which the conductive film 10 was attached ). when the glare was not observed , the sample was evaluated as excellent . when the glare was slightly observed but acceptable , the sample was evaluated as fair . when the glare was significantly observed , the sample was evaluated as poor . as shown in table 1 , in examples 1 and 2 , each sample had no significant glare , a low surface resistivity sufficient for practical use in a transparent heating element , and an excellent light transmittance . in addition , conductive films were produced in the same manner as in example 1 except for using mesh patterns shown in fig1 and 23 , respectively . also , each of the conductive films had no significant glare , a low surface resistivity sufficient for practical use in a transparent heating element , and an excellent light transmittance . it is to be understood that the conductive film and the transparent heating element of the present invention are not limited to the above embodiments , and various changes and modifications may be made therein without departing from the scope of the present invention . the present invention may be appropriately combined with technologies described in the following patent publications : japanese laid - 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