JP2017168310A - Transfer film for anti-fog heater and windshield for vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a transfer film for an anti-fog heater and a windshield for a vehicle, which are easy to adapt to the change in pattern and which make possible to form a high-definition conducting pattern on an adherend by a simple work.SOLUTION: A transfer film 1 for an anti-fog heater comprises: one or more conducting patterns 3 which is provided on a support body 2 and which can be peeled from the support body and transferred to an adherend. The conducting pattern has: a plurality of terminal parts 4a, 4b to supply a current to the conducting pattern from outside; and a line pattern part 5 extending from the plurality of terminal parts uninterruptedly. The line pattern part includes: a heater line 6 including a surrounding portion Ps extending so as to surround at least a part of the circumference of a heated region; and a plurality of lead wires 7a, 7b connecting both ends of the heater line to plurality of terminal parts respectively. The percentage that the resistance value of the heater line accounts for in a total resistance value of the line pattern part is 80% or more, and the percentage that the resistance of the plurality of lead wires accounts for is 20% or less of the total resistance value.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an anti-fogging heater for providing a conductive pattern for preventing fogging on a window glass or other adherend such as a windshield of an automobile in which an optical sensor system for acquiring information outside the vehicle is disposed in the vicinity. The present invention relates to a transfer film for a vehicle and a windshield for a vehicle.

In recent years, an optical sensor system such as an optical camera system used to prevent collision accidents by acquiring information outside the vehicle, for example, in the vicinity of a windshield of a vehicle such as an automobile may be installed. .
When such an optical sensor system is installed, in order to prevent fogging of the viewing window, which is a glass region that falls within the field of view of the camera of the optical camera system, the periphery of the viewing window is surrounded by or inside the windshield. A heating lead for heating the viewing window is provided.

  As this type of technology, Patent Document 1 is a light sensor system and / or a light identification system viewing window in a vehicle, in which at least one field of view of the optical system is defined in the viewing window. Discloses a viewing window provided with a window heating device surrounding the field of view. In this patent document 1, it is described that the window heating apparatus includes a heating conductor embedded in the window or bonded or printed on the surface of the window.

  Patent Document 2 discloses an optical functional element that transmits a signal to and / or receives a signal from the opposite surface of the window glass through an optical transmission region of the window glass, and a window of the transmission region. A window glass provided with a local heating part for preventing condensation of glass is disclosed. And it is described that the heating element has a heating wire that can be heated electrically and / or a transparent heating layer that can be heated electrically.

  Patent Document 3 discloses a vehicle sensor mounting structure in which a plurality of sensors are installed close to each other in the vicinity of glass. The plurality of sensors includes an image sensor that captures the outside of the vehicle through the glass and a glass fogging sensor that prevents the fogging of the glass, and the imaging system heats a glass region corresponding to the imaging range of the image sensor. And the glass heating device is described as including a hot wire heater embedded in the glass.

Special table 2010-534588 gazette JP 2014-037344 A JP, 2014-101004, A

  As described above, in the case where a conductive pattern for preventing fogging is provided on a part of a window glass such as a windshield of an automobile having an optical sensor system in the vicinity, conventionally, it has been directly applied to a predetermined region on the surface of the window glass. In addition, the conductive pattern is formed by a printing method such as screen printing using a conductive ink.

  However, printing methods such as screen printing require a printing plate that matches the printing pattern, and when changing the pattern, the printing plate must be changed. Moreover, in order to print on relatively large items such as automobile window glass, a large-scale printing facility is required.

In addition, the conductive pattern for preventing fogging includes at least a heater wire that surrounds and heats a predetermined area, and a lead wire that allows an externally supplied current to flow through the heater wire. It is desirable to design a high-definition conductive pattern so that the heater wire effectively generates heat while the lead wire does not generate heat as much as possible.
When the conductive pattern is directly formed on the window glass or the like by the printing method, it is difficult to design the conductive pattern with high definition with the large printing equipment as described above.

An object of the present invention is to solve such problems of the prior art, and its main purpose is to use a high-definition conductive pattern on an adherend without using a large-scale printing facility. Another object of the present invention is to provide a defogging heater transfer film and a vehicle windshield that can be formed by simple operations and can easily cope with pattern changes.
Another object of the present invention is to provide a transfer film for an anti-fogging heater and a vehicle windshield capable of effectively heating the heater wire while effectively suppressing the heat generation of the lead wire of the conductive pattern. There is.

  The transfer film for an anti-fogging heater of this invention is provided with one or more conductive patterns that can be peeled off from a support and transferred to an adherend on the support, and the conductive pattern is A plurality of terminal portions for supplying current to the conductive pattern from the outside, and a linear pattern portion extending continuously from the plurality of terminal portions, wherein the linear pattern portion is a region to be heated. A heater wire including an encircling portion extending so as to surround at least a part of the periphery, and a plurality of lead wires connecting each of both end portions of the heater wire to each of the plurality of terminal portions, The ratio of the resistance value at the heater wire to the total resistance value of the linear pattern portion is 80% or more, and the ratio of the resistance at the lead wire to the total resistance value is 20% or less.

Here, in the transfer film for an anti-fogging heater according to the present invention, the heater wire may have a linear resistance adjusting portion that increases a resistance value of the heater wire at a connection position with the lead wire.
Further, in the transfer film for an anti-fogging heater according to the present invention, the heater wire may include a crossing portion that extends from a part of the surrounding portion and across a heated region surrounded by the surrounding portion.

  In the transfer film for an anti-fogging heater according to the present invention, when the heater wire has a bent portion that bends at an angle of 90 ° or less, the bent portion may have an arc shape with a curvature radius R of 1 mm or more. preferable. More preferably, the bent portion has an arc shape with a radius of curvature R of 4 mm or more.

In the transfer film for an anti-fogging heater of this invention, it is preferable that the line width of the lead wire is equal to or larger than the line width of the heater wire. In this case, the lead wire is at a connection position with the heater wire. It is preferable to have a line width restricting portion in which the line width is gradually reduced toward the heater wire.
In this case, it is preferable that the line width of the lead wire is 1 mm to 5 mm, the line width of the heater wire is 0.1 mm to 0.5 mm, and the length of the line width restricting portion is 5 mm or more.

In the transfer film for an anti-fogging heater of this invention, it is preferable that the conductive pattern includes at least a conductive material, a glass frit, and an organic substance that can be removed by baking.
In the transfer film for an anti-fogging heater of the present invention, the linear pattern is preferably covered with a coating layer containing at least a glass frit and an organic binder that can be removed by firing.

  The transfer film for an anti-fogging heater according to the present invention is laminated on the support, a protective layer in which the conductive pattern is disposed, an intermediate layer laminated on the protective layer, and a laminated layer on the intermediate layer It is preferable that the protective layer, the intermediate layer, and the adhesive layer are made of an organic material that can be removed by baking to transfer the conductive pattern to the adherend.

  Further, the vehicle windshield of the present invention has a glass plate and is capable of disposing an optical sensor system that acquires information outside the vehicle through a viewing window of the glass plate, and is electrically conductive on the glass plate. Comprising a pattern, wherein the conductive pattern has a plurality of terminal portions for supplying current to the conductive pattern from the outside, and a linear pattern portion extending continuously from the plurality of terminal portions, The linear pattern portion includes a heater wire including an encircling portion extending so as to surround at least a part of the periphery of the viewing window, and a plurality of both ends of the heater wire respectively connected to the plurality of terminal portions. The ratio of the resistance value in the heater wire to the total resistance value of the linear pattern portion is 80% or more, and the ratio of the resistance in the lead wire to the total resistance value 20 It is made as follows.

Here, in the vehicle windshield according to the present invention, it is preferable that the heater wire has a linear resistance adjustment portion that increases a resistance value of the heater wire at a connection position with the lead wire.
Further, in the vehicle windshield according to the present invention, it is preferable that the heater wire includes a crossing portion that extends from a part of the surrounding portion and extends across a heated region surrounded by the surrounding portion.

  In the vehicle windshield of the present invention, when the heater wire has a bent portion that bends at an angle of 90 ° or less, the bent portion preferably has an arc shape with a curvature radius R of 1 mm or more. More preferably, the bent portion has an arc shape with a radius of curvature R of 4 mm or more.

In the vehicle windshield of the present invention, the lead wire has a line width greater than or equal to the line width of the heater wire, and the lead wire has a line width toward the heater wire at a connection position with the heater wire. It is preferable to have a line width narrowing part in which is gradually reduced.
In this case, it is preferable that the line width of the lead wire is 1 mm to 5 mm, the line width of the heater wire is 0.1 mm to 0.5 mm, and the length of the line width restricting portion is 5 mm or more.

According to the present invention, a relatively large deposition such as a window glass of an automobile is provided by providing a transfer film on the support with one or more conductive patterns peeled off from the support and transferable to the adherend. Even on the body, the conductive pattern can be easily formed at any desired position by a simple operation of transferring the conductive pattern of the transfer film onto the adherend. And if it is a transfer film, the necessary pattern can be formed separately in a separate body such as a separator film, so that it is possible to form a high-definition pattern with ordinary printing equipment, the pattern design is easy, and multiple types of Since the conductive pattern can be stored in a film shape or the like, complicated work such as changing the printing plate is not necessary.
Further, by adjusting the resistance value between the heater wire and the lead wire of the conductive pattern, the heater wire can be effectively heated while effectively suppressing the heat generation of the lead wire.

It is a partial top view of the transfer film which shows the example of arrangement | positioning of the electroconductive pattern of the transfer film of one Embodiment of this invention. It is the elements on larger scale of the heater wire of the electroconductive pattern shown to Fig.1 (a). It is a graph which shows the relationship between the bending angle of the bending part in the heater wire of an electroconductive pattern, and a temperature rise ratio. It is a graph which shows the relationship between the arc curvature radius of the bending part in the heater wire of an electroconductive pattern, and a temperature reduction ratio. FIG. 2 is a partially enlarged plan view showing an end portion on a heater wire side of a lead wire in the conductive pattern of the transfer film of FIG. 1. It is sectional drawing of the direction orthogonal to an electroconductive pattern which shows the transfer film of FIG. 1 typically. It is sectional drawing in a terminal part which shows the transfer film of FIG. 1 typically. It is an approximate line sectional view showing a schematic structure of an optical sensor system provided in a windshield.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
As illustrated in FIGS. 1A to 1E, a transfer film 1 for an anti-fogging heater according to one embodiment of the present invention (hereinafter also simply referred to as “transfer film 1”), One or more conductive patterns 3 that are provided on the support 2 and can be peeled off from the support 2 are provided. The conductive pattern 3 is transferred to an adherend such as a window glass, peeled off from the support 2, and then sintered on the adherend at about 600 ° C., thereby functioning as a fog prevention heater.

(Conductive pattern)
As shown in FIG. 1, the conductive pattern 3 includes a plurality (a pair in the illustrated embodiment) of terminal portions connected to terminals on the power supply side (not shown) in order to supply current to the conductive pattern 3 from the outside. 4a and 4b and a linear pattern portion 5 extending from the plurality of terminal portions 4a and 4b and forming one continuous pattern.
Here, the linear pattern portion 5 includes a heater wire 6 including an encircling spot Ps extending around at least a part of the periphery of the heated area Ah, and both end portions of the heater wire 6 each having a plurality of terminal portions. 4a and 4b, a plurality of lead wires 7a and 7b (a pair in the illustrated embodiment) connected to each of them.

  In the linear pattern portion 5 of the conductive pattern 3, it is necessary to prevent the lead wires 7 a and 7 b that send current to the heater wire 6 from being heated as much as possible with respect to the heater wire 6 that generates heat to heat the heated area Ah. There is. Therefore, the ratio of the resistance value of the heater wire 6 to the total resistance value of the linear pattern portion 5 is 80% or more, and more preferably 90% or more. The ratio of the resistance values of both lead wires 7a and 7b to the total resistance value is 20% or less, and more preferably 10% or less.

In order to realize such distribution of resistance values, the pattern shape of the conductive pattern 3 can be designed as shown in FIGS.
For example, as shown in FIG. 1 (a), on the support 2, the lead wires 7a and 7b connected to the pair of terminal portions 4a and 4b extend in a direction approaching each other (in the left-right direction in FIG. 1). After that, it bends at a substantially right angle and extends parallel to each other. The heater wire 6 continuing to the ends of the lead wires 7a and 7b is substantially trapezoidal as a whole and extends to surround the heated area Ah. However, the heater wire 6 in FIG. 1A has a meander shape in which the pattern of the surrounding portion Ps extends while meandering to the left and right in the extending direction.

In FIG. 1 (b), the heater wire 6 has a trapezoidal shape with two outside and inside wires instead of a meander shape, the center of the bottom is discontinuous, and lead wires 7a and 7b. 1 is substantially the same as that shown in FIG. 1A except that a linear resistance adjustment portion 8 that increases the resistance value of the heater wire 6 is provided at the connection position. The resistance adjusting portion 8 forms a part of the heater wire 6. In the illustrated example, the resistance adjusting portion 8 swells in a rectangular shape so as to widen the interval between the lead wires 7 a and 7 b extending in parallel with each other. It has an extending shape.
When such a resistance adjustment portion 8 is provided, when the resistance value at the resistance adjustment portion 8 and the resistance value at the heater wire 6 are added together, the ratio of the total to the total resistance value is 80% or more, preferably Can be adjusted to 90% or more. The lead wires 7a and 7b and the heater are provided by providing the resistance adjusting portion 8 when there is a restriction on the location and position where the conductive pattern 3 is transferred or when the area of the heated area Ah by the heater wire 6 is adjusted. The resistance ratio of the line 6 can be easily adjusted.

  In the example shown in FIG. 1C, the heater wire 6 is obliquely extended from a part of the surrounding portion Ps so as to cross the heated area Ah surrounded by the surrounding portion Ps of the heater wire 6. Except for the point that has a crossing point Pt and the discontinuous part is the part of one of the trapezoidal legs from which the crossing point Pt extends, it is substantially the same as that shown in FIG. Even if the area of the heated region Ah is large, the temperature at the center of the heated region Ah can be effectively increased by the crossing point Pt.

  As shown in FIG. 1 (d), the lead wires 7a and 7b are temporarily extended from the pair of elongated terminals 4a and 4b to the upper side in the drawing as compared with those of FIGS. 1 (a) to (c). Then, after bending in a direction approaching each other, it is further bent at a substantially right angle so as to extend parallel to each other toward the lower side of the figure. The heater wire 6 has a surrounding portion Ps having a substantially parallelogram shape as a whole, and a crossing portion Pt extending from a part of the surrounding portion Ps so as to cross a substantially central portion of the non-heating region Ah in a rectangular shape, It is the shape which extended the connection position of the left end of the figure of the surrounding location Ps and the crossing location Pt by making it protrude in the downward direction of a figure.

In FIG. 1 (e), the shapes of the terminal portions 4a, 4b and the lead wires 7a, 7b are substantially the same as those shown in FIG. 1 (d), but the heater wire 6 has an outer shape of “U”. And the point that two resistance adjusting portions 8 that bulge outward and extend at the connecting position with the lead wires 7a and 7b are provided.
However, the shape of the conductive pattern 3 can be various shapes other than those described above as long as a desired resistance ratio between the heater wire 6 and the lead wires 7a and 7b can be realized.

In such a linear pattern portion 5, when the heater wire 6 has a bent portion 9 that bends at an angle of 90 ° or less, as shown in an enlarged view in FIG. 2, each bent portion 9 has a radius of curvature R. Is preferably an arc shape of 1 mm or more. As can be seen from the graph showing the relationship between the bending angle and the temperature increase ratio in FIG. 3, the heat generation temperature of the bent portion 9 is higher than that of the straight portion (180 °), and particularly when the bent portion 9 has a bent angle of 90 ° or less. This is because the temperature rises remarkably, and this temperature rise can be suppressed by adjusting the curvature radius of the bent portion.
FIG. 4 is a graph showing the relationship between the radius of curvature of the arc and the temperature reduction ratio when the bending angle is 45 °, and by increasing the radius of curvature of the arc-shaped bend 9, the temperature of the bend is increased. The rise can be effectively suppressed.

  Therefore, the bent portion 9 that bends at an angle of 90 ° or less has an arc shape with a radius of curvature R of 1 mm or more, so that the line-to-line distance at the most protruding portion of the bent portion 9 is secured. An excessive temperature rise at 9 can be effectively suppressed. From this viewpoint, it is more preferable that the bent portion 9 that bends at an angle of 90 ° or less has an arc shape with a radius of curvature of 4 mm or more.

  In consideration of the amount of heat generated in the lead wires 7 a and 7 b and the heater wire 6 of the linear pattern 5, the line width Lw of the lead wires 7 a and 7 b is greater than the line width Lh of the heater wire 6, particularly from the heater wire 6. A wide width is preferable. Furthermore, as shown in FIG. 5, it is preferable that the lead wires 7 a and 7 b have a line width narrowing portion 10 whose width is gradually narrowed toward the heater wire 6 at a connection position with the heater wire 6. In FIG. 5, only one lead wire 7a is shown, but it is preferable to provide a similar line width narrowing portion 10 also on the other lead wire 7b.

By defining the line width Lw of the lead wires 7a and 7b and the line width Lh of the heater wire 6 in this way, the resistance values at the lead wires 7a and 7b and the heater wire 6 are changed to facilitate temperature control. Can do. In addition, the line width narrowing portion 10 that gradually reduces the line width from the lead wires 7a and 7b toward the heater line 6 can effectively suppress local heat generation caused by a sudden change in the line width. .
When the line width restricting portion 10 is provided, the resistance adjusting portion 8 described above can be disposed between the line width restricting portion 10 and the heater wire 6 although illustration is omitted.

  When the length Ln of the line width restricting portion 10 is set to 5 mm or more, the rapid heat generation in the transition region from the lead wires 7a and 7b to the heater wire 6 can be sufficiently effectively suppressed. More preferably, the length Ln of the line width restricting portion 10 is set to 10 mm or more.

The total length of the lead wires 7a and 7b can be 50 mm or more, preferably 100 mm or more. If it is less than 50 mm, the camera unit and the heater wire 6 in the case of the optical sensor system are close to each other, and the camera unit is easily affected by heat.
The line width Lw of the lead wires 7a and 7b can be 1 mm or more and 5 mm or less, preferably 2 mm or more and 3 mm or less. If it is 1 mm or less, the resistance value becomes high, and there is a risk that the lead wires 7a and 7b generate heat to a degree that cannot be ignored. On the other hand, in the case of 5 mm or more, there is a concern that the wiring bursts during the firing process.
The area that can be calculated by multiplying the total length of the lead wires 7a and 7b by the line width Lw is 50 mm ² or more (for example, total length 50 mm × line width 1.0 mm), preferably 250 mm ² or more (for example, total length 100 mm × line width 2. 5 mm).

The total length of the heater wire 6 can be 300 mm or more, preferably 600 mm or more.
Moreover, the line width Lh of the heater wire 6 can be 0.1 mm or more and 0.5 mm or less, preferably 0.15 mm or more and 0.3 mm or less. In the case of 0.1 mm or less, it may be difficult to produce in the manufacturing process, which may lead to disconnection or the like. On the other hand, in the case of 0.5 mm or more, depending on the application, the resistance value as a heater cannot be obtained and the characteristics may not be satisfied.
The area that can be calculated by multiplying the total length of the heater wire 6 by the line width Lh is 30 mm ² or more (for example, total length 300 mm × line width 0.1 mm), preferably 90 mm ² (for example, total length 600 mm × line width 0.15 mm). can do.

(Transfer film)
As described above, the transfer film 1 according to one embodiment of the present invention is provided with the conductive pattern 3 that is peeled from the support 2 and transferred to the adherend and baked on the support 2. It will be. In order to form the conductive pattern 3 on the adherend using the transfer film 1, first, the transfer film 1 is placed on the adherend such as a window glass, and then only the support 2 is peeled off. Then, for example, by heating to about 550 ° C. to 650 ° C., particularly about 600 ° C., the conductive pattern 3 is sintered to the adherend and functions as a heater for preventing fogging of the adherend.
More specifically, the transfer film 1 includes a support 2, a protective layer 11 laminated on the support 2, and a protective layer, as shown in a sectional view in FIG. It is preferable to have an intermediate layer 12 laminated on 11 and an adhesive layer 13 laminated on the intermediate layer 12.

And as shown to Fig.6 (a), the linear pattern part 5 as above-mentioned can be embedded and arrange | positioned inside this protective layer 11. FIG. Furthermore, it is preferable that the linear pattern portion 5 is entirely covered with the coating layer 14 in the protective layer 11.
On the other hand, the terminal portions 4a and 4b can also be disposed so as to be entirely covered with such a covering layer 14, but as shown in FIG. The covering layer 14 can be interposed only between the intermediate layer 12 and the intermediate layer 12. Therefore, as shown in FIG. 7, the periphery of the terminal portions 4a and 4b is surrounded by the protective layer 11 other than the covering layer 14 on the intermediate layer 12 side. Of the conductive pattern 3, the terminal portions 4 a and 4 b to which current is supplied from the outside may not be covered with the coating layer 14.
Note that the coating layer 14 can be provided only on the portion of the transfer film 1 where the conductive pattern 3 is present, whereas the protective layer 11, the intermediate layer 12, and the adhesive layer 13 are generally formed on the entire surface of the transfer film 1. Provided.

Here, when the conductive pattern 3 of the transfer film 1 is transferred to the adherend 15, the transfer film 1 is placed on the adherend 15 as shown in FIGS. 6B and 7B. It can be performed by bonding the adhesive layer 13 and then peeling only the support 2 and heating at about 600 ° C. to sinter the conductive pattern 3 to a predetermined position of the adherend 15. it can.
In the case of such transfer, it is preferable that the conductive pattern 3 includes at least a conductive material, glass frit, and an organic binder that can be removed by baking. The coating layer 14 may include at least a glass frit and an organic material that can be removed by firing. Any of the protective layer 11, the intermediate layer 12, and the adhesive layer 13 can be made of an organic material that can be removed by baking after being transferred to the adherend 15. Thus, after the conductive pattern 3 is transferred to the adherend 15, unnecessary portions of the transfer film 1 are removed as shown in FIGS. 6 (c) and 7 (c).

  The support 2 functions as a support when the antifogging heater transfer film 1 is manufactured and as a support when the antifogging heater transfer film 1 is bonded to the adherend 15. The material of the support 2 is not particularly limited as long as the conductive pattern 3 can be peeled therefrom. For example, a resin film such as polyethylene terephthalate (PET) or polyimide, a metal sheet such as aluminum foil, and a ceramic sheet In addition, for example, in consideration of the case where a long strip-shaped transfer film provided with a plurality of conductive patterns 3 is stored in a roll shape, the conductivity of the support 2 is determined. A release layer such as silicone (not shown) or a slightly adhesive layer for re-peeling may be provided on the back surface opposite to the surface on which the adhesive pattern 3 is provided.

The conductive pattern 3 can include at least a conductive material, glass frit, and an organic binder that can be removed by baking, and is preferably baked after being transferred to the adherend 15.
Specifically, as the conductive material, Au, Ag, Cu, Ni, Co, Sn, Pb, Zn, Bi, In, or an alloy powder containing these can be used. Examples of the glass frit that can be thermally fused include oxides such as SiO ₂ , ZrO ₂ , Al ₂ O ₃ , TiO ₂ , CeO ₂ , B ₂ O ₃ , Bi ₂ O ₃ , Na ₂ O, K ₂ O, and ZnO. A simple substance or a complex oxide containing two or more of these oxides can be used. The type of organic binder that can be removed by firing is not limited as long as a material that can be removed by firing is used, but materials that are easily decomposed and removed by firing include acrylic, methylcellulose, nitrocellulose, ethylcellulose, vinyl acetate, and polyvinyl butyral. , Polyvinyl acetal, polyvinyl alcohol, polyethylene oxide, polyester, and other resins can be used, and one of them or a mixture thereof can be used. Further, a plasticizer may be added as an organic component for the purpose of imparting flexibility to the coating film before firing. As the plasticizer, fatty acid ester type, phosphate ester type and the like can be used.
The ratio of the conductive material to the glass frit can be in the range of 99: 1 to 50:50, more preferably 99: 1 to 85:15 by mass ratio. When the ratio of the conductive material is 99 or more, the resistance value after firing becomes low, but the ratio of the glass frit to be fused with the adherend 15 is reduced and the adhesion is lowered. On the other hand, when the ratio of the conductive material is 50 or less, the resistance value after firing becomes high, and the temperature control of the lead wires 7a and 7b and the heater wire 6 becomes difficult.

  The film thickness of the conductive pattern 3 is not particularly specified, but is preferably 4 to 15 μm. When the thickness is less than 4 μm, the firing property is improved, but the resistance value after firing becomes high. On the other hand, when it is thicker than 15 μm, the resistance value after firing becomes low, but the firing property is lowered, and the desired fired film Cannot be obtained. When the film thickness of the terminal portions 4a and 4b in the conductive pattern 3 is smaller than 4 μm, the firing property is improved, but since the transfer amount to the adherend 15 is small, the conductive pattern is caused by the heat of the soldering iron. Will melt into the solder. On the other hand, when it is thicker than 15 μm, the calcination property is lowered and a desired fired film cannot be obtained.

The covering layer 14 that covers the entire linear pattern portion 5 and can be disposed on a part of the periphery of the terminal portions 4a and 4b is fired on the adherend 15 simultaneously with the conductive pattern 3 to form a fired body, There exists an effect | action which improves the environmental resistance of an electroconductive pattern. In particular, when there are portions of the linear pattern 5 adjacent to each other, it is possible to prevent a short circuit between wirings caused by electromigration due to moisture adhesion or the like.
When the coating layer 14 is a black layer, reflection of light (smear) can be prevented, which is preferable from the viewpoint of visibility. The black layer contains at least a black pigment that does not physically change even when fired, an organic material that can be removed by firing, and a glass frit that can be thermally fused. Examples of black pigments that can be used for the black layer include Cu—Cr-based oxides and Cu—Cr—Mn-based oxides. The mass ratio between the black pigment and the glass frit is preferably in the range of 95: 5 to 50:50. When the ratio of the black pigment is lower than 50, the abrasion resistance and the weather resistance are improved, but the blackness is lowered. On the other hand, when the ratio of the black pigment is higher than 95, the blackness is improved, but the ratio of the black pigment that is not fused even when baked is increased, so that the chemical bonding force at the interface between the black pigment and the glass frit is weak. Wear resistance and weather resistance are reduced.
The film thickness of the black layer is preferably 5 to 15 μm, more preferably 7 to 13 μm. When the film thickness is thinner than 5 μm, the calcination property is improved, but the amount of glass frit is reduced, so that the wear resistance and weather resistance are lowered, and the blackness is also lowered. When the film thickness is thicker than 15 μm, the calcination property is lowered and it becomes difficult to obtain a desired baked film.
As the organic material that can be removed by baking for the black layer, the same organic material as that used for the conductive pattern 3 can be used. The glass frit that can be thermally fused is not particularly limited as long as it is a material that can be fused to the adherend 15 such as a window glass by firing, and the same material as that used for the conductive pattern 3 can be used. .

In order to form each layer of the transfer film 1, it is possible to employ a printing method such as screen printing or offset printing, a coating method such as gravure coating, a dispenser, or the like.
When the conductive pattern 3 or the coating layer 14 is formed by a printing method such as screen printing, a coating material in which glass frit or an organic substance is dispersed in a solvent is prepared and used. As the solvent, water-based, alcohol-based, ketone-based, ester-based, ether-based, hydrocarbon-based, etc. can be used in consideration of the solubility and dispersibility of organic substances and the boiling point suitable for printing. As the physical properties of the paint, the printing suitability such as viscosity and thixotropy and the solid content are appropriately adjusted and used. If necessary, additives such as an antifoaming agent and a thickening agent can be used to prevent bubbles during printing and to adjust viscosity. An additive that can be decomposed and removed by firing is used.

The protective layer 11, the intermediate layer 12, and the adhesive layer 13 that can be provided on the support in order to improve the function as a transfer film are made of an organic substance that can be removed by baking after being transferred to the adherend 15. can do.
The protective layer 11 is made of an organic material that can be removed by baking. The protective layer 11 has an effect of preventing damage to the conductive pattern 3 and the coating layer 14, an effect of stabilizing the peel strength with the support 2, and improving transferability. .
The organic material used for the protective layer 11 is not particularly limited as long as it is an organic material that can be removed by firing. For example, (meth) acrylic, butyral, polyester, polyurethane, cellulose, polyvinyl, and the like can be used. Can be used.
The protective layer 11 can be formed by a printing method, a coating method, a laminating method, and the like. The protective layer 11 can be formed in the same shape as the conductive pattern 3 and the covering layer 14, and may have a wide sheet shape. The thickness of the protective layer 11 is preferably 1 to 10 μm. When the film thickness is less than 1 μm, the protective layer 11 cannot be sufficiently formed on the conductive pattern 3 or the coating layer 14, resulting in poor scratch resistance and flexibility, leading to problems such as disconnection. On the other hand, when it is thicker than 10 μm, the protective layer is not sufficiently burned in the baking process, which affects the baking property.

The intermediate layer 12 can be provided in order to prevent unintentional movement of each layer during firing, increase the ease of manufacturing, and prevent the adhesive layer from being damaged during firing.
The organic material used for the intermediate layer 12 is not particularly limited as long as it is an organic material that can be removed by firing. However, it is preferable to use an organic material having no tackiness and having a Tg of 30 ° C. or higher, preferably 40 ° C. or higher. For example, a polyol having a hydroxyl group can be used, and one or more selected from (meth) acrylic, butyral, polyester, polyurethane, cellulose, and polyvinyl can be used. . The film thickness of the intermediate layer 12 is preferably 3 to 30 μm. When the film thickness of the intermediate layer 12 is less than 3 μm, when another upper layer is formed on the intermediate layer in the printing process, the solvent contained in the solvent-based ink used for the upper layer dissolves and moisturizes the intermediate layer, A sheet attack occurs and floats between the intermediate layer 12 and the separator base material, causing disconnection or the like. On the other hand, when the film thickness is thicker than 30 μm, combustion of the intermediate layer 12 in the firing process becomes insufficient, which affects the fireability.
When a curing agent is used for the intermediate layer 12, a thermosetting system is preferable, an epoxy curing system or an isocyanate curing system can be used, an isocyanate system is particularly preferable, and an isocyanurate system or a blocked isocyanate system is used. Is possible.
As a method for forming the intermediate layer 12, a printing method such as screen printing or offset printing, or a coating method such as gravure coating can be used. The intermediate layer 12 can be formed in a pattern having the same shape as the conductive pattern 3 and the covering layer 14, and may have a wide sheet shape.

The pressure-sensitive adhesive layer 13 is not particularly limited as long as it is an organic substance that can be removed by baking, but an acrylic or rubber-based pressure-sensitive adhesive having tack at normal temperature can be used. The thickness of the pressure-sensitive adhesive layer 13 can be selected in accordance with the surface roughness and shape of the adherend 15, and can be selected so as to be easily transferred, and is preferably 1 to 10 μm. If the thickness is less than 1 μm, the adhesive force is insufficient and the transferability is lowered. If the thickness is greater than 10 μm, the amount of pyrolysis gas generated during firing increases, and thus the conductive pattern 3 and the coating layer 14 are likely to be defective. It tends to be defective. As the thickness of the pressure-sensitive adhesive layer 13 is as thin as possible within the range in which the adhesion force to the adherend 15 is expressed, the amount of pyrolysis gas of the pressure-sensitive adhesive layer 13 becomes small, and good baking properties can be stably obtained. It is preferable in terms of ease.
The adhesive layer 13 can be formed by a printing method such as screen printing or offset printing, or a coating method such as die coating or gravure coating.

  When the protective layer 11, the intermediate layer 12, and the adhesive layer 13 are formed by a printing method such as screen printing, a paint in which each organic substance is dissolved in an appropriate solvent is prepared, and the printing suitability such as viscosity and thixotropy, and the solid content are appropriately set. Adjust and use. If necessary, additives such as an antifoaming agent and a thickening agent can be used to prevent bubbles during printing and to adjust viscosity. It is necessary to use an additive that can be decomposed and removed by firing. Solvents that can adjust the boiling point, viscosity, and thixotropy suitable for each forming method may be selected. Water-based, alcohol-based, ketone-based, ester-based, ether-based, hydrocarbon-based solvents, etc. should be used. Is possible.

  In order to manufacture the transfer film 1 as described above, an adhesive layer 13 is formed on a carrier film (not shown), an intermediate layer 12 is laminated thereon and cured, and then the conductive pattern 3, the coating layer 14, and the protective layer are protected. The layer 11 can be formed by sequentially laminating, and the support 2 that functions as a protective film for the transfer film 1 is laminated on the protective layer 11. As another method, after forming the intermediate layer 12 on the carrier film and laminating the conductive pattern 3, the coating layer 14 and the protective layer 11, the support 2 as the protective film is laminated on the protective layer 11. It is also possible to produce a laminate, peel off the carrier film of the laminate, and apply and form the adhesive layer 13 on the intermediate layer 12. Alternatively, a pressure-sensitive adhesive sheet in which the pressure-sensitive adhesive layer 13 is formed on the peeling film is prepared separately, and the pressure-sensitive adhesive layer 13 can be prepared by laminating the pressure-sensitive adhesive sheet on the intermediate layer 12 from which the carrier film has been peeled off.

  In order to transfer the conductive pattern 3 to the adherend 15 such as a vehicle window glass using the transfer film 1, the adhesive layer 13 of the transfer film 1 is bonded to the adherend 15, and then the support 2 is attached. After peeling and firing, a fired body of the conductive pattern 3 and the coating layer 14 is formed on the adherend 15.

(Adherent)
Various materials such as a glass plate, a stainless steel plate, a steel plate, a copper plate, an aluminum plate, and a ceramic plate can be selected as the adherend 15, but are close to the thermal expansion coefficient of the glass frit contained in the conductive pattern 3. A glass having a coefficient of thermal expansion is most preferable as the adherend 15.

  As the glass, a known glass plate can be used, and heat ray absorbing glass, general clear glass, green glass, or UV green glass can be used. Examples of clear glass, heat ray absorbing glass, and soda-lime glass are shown below.

<Clear glass>
SiO _2: 70~73 mass%
Al ₂ O ₃ : 0.6 to 2.4% by mass
CaO: 7 to 12% by mass
MgO: 1.0 to 4.5 mass%
R ₂ O: 13-15% by mass
Fe total iron oxide in terms _{of 2 O 3 (T-Fe 2} O 3): 0.08~0.14 wt%

<Heat ray absorbing glass>
The composition of the heat-absorbing glass, for example, based on the composition of the clear glass, the proportion of the total iron oxide in terms of _{Fe 2 O 3 (T-Fe} 2 O 3) and 0.4 to 1.3 wt%, CeO ₂ ratio as 0-2 mass%, the proportion of TiO ₂ and 0 to 0.5 wt%, framework component of the glass (mainly, SiO ₂ and Al ₂ O ₃₎ to T-Fe ₂ O _3, CeO _The composition can be reduced by an increase of ₂ and TiO ₂ .

<Soda-lime glass>
SiO _2: 65~80 mass%
Al ₂ O ₃ : 0 to 5% by mass
CaO: 5 to 15% by mass
MgO: 2% by mass or more NaO: 10-18% by mass
K ₂ O: 0 to 5% by mass
MgO + CaO: 5 to 15% by mass
Na ₂ O + K ₂ O: 10 to 20% by mass
SO ₃ : 0.05 to 0.3% by mass
B ₂ O ₃ : 0 to 5% by mass
Fe total iron oxide in terms _{of 2 O 3 (T-Fe 2} O 3): 0.02~0.03 wt%

<Configuration of glass plate / Configuration of laminated glass>
Various configurations are possible for the glass plate. For example, the glass plate can be composed of laminated glass having a plurality of glass plates, or can be composed of a single glass plate. This laminated glass includes two glass plates, and a resin intermediate film is disposed between the two glass plates. As these two glass plates, known glass plates can be used, and they can be formed of the above-mentioned heat ray absorbing glass, general clear glass, green glass, or UV green glass. The intermediate film is formed of at least one layer, and can be constituted by, for example, three layers in which a soft core layer is sandwiched between harder outer layers. As a specific material, an outer layer can be comprised by polyvinyl butyral resin (PVB), for example. Polyvinyl butyral resin is preferable because it is excellent in adhesiveness and penetration resistance with each glass plate. On the other hand, the core layer can be made of, for example, an ethylene vinyl acetate resin (EVA) or a polyvinyl acetal resin softer than the polyvinyl butyral resin constituting the outer layer. By sandwiching the soft core layer between them, the sound insulation performance can be greatly improved while maintaining the same adhesion and penetration resistance as the single-layer resin intermediate film.

(Front glass with optical sensor system)
FIG. 8 is a cross-sectional view showing a schematic configuration of the optical sensor system 22 provided on the windshield 21. As shown in FIG. 8, the optical sensor system 22 includes a bracket 23 fixed to the inner surface of the windshield 21, the optical sensor system 22 supported by the bracket 23, and the bracket 23 and the optical sensor system 22 from the inside of the vehicle. The cover 24 is covered.
The bracket 23 is fixed to the inner surface of the windshield 21. A viewing window 31 is formed in the bracket 23.

  After a harness (not shown) is attached to the bracket 23, a cover 24 is attached from the inside of the vehicle as shown in FIG. As a result, the optical sensor system 22 and the bracket 23 are not visible from the inside of the vehicle. Thus, the optical sensor system 22 is accommodated in the space surrounded by the bracket 23, the cover 24, and the glass plate 21.

The optical sensor system 22 calculates the distance between the preceding vehicle or the obstacle and the own vehicle by irradiating the laser beam through the viewing window 31 and receiving the reflected light reflected from the preceding vehicle or the obstacle. It is transmitted to an external device via a connector that is not used, and is used for brake control or the like.
The thickness of the windshield is preferably 3 mm to 14 mm. If the thickness is less than 3 mm, the glass may be broken due to a stress caused by a temperature difference with the peripheral portion when energized. If the thickness is more than 14 mm, heat is not easily transmitted, and the time until cloudiness is cleared becomes too long.

  Next, the transfer film of the present invention was prototyped and its effect was confirmed, and will be described below. However, the description here is for illustrative purposes only and is not intended to be limiting.

<Test Example 1>
A transfer film was prepared according to the following procedure.
(Preparation of film with intermediate layer)
A PET film “A70” (manufactured by Teijin DuPont Films Ltd., thickness: 50 μm, film size: 250 mm × 300 mm) provided with a silicone-based release layer was prepared as a film substrate for forming the intermediate layer. Polyvinyl acetal resin “KW3” (manufactured by Sekisui Chemical Co., Ltd.) was dissolved and diluted with a mixture medium of 50:50 water and isopropyl alcohol in mass ratio to obtain an intermediate layer ink. This intermediate layer ink is printed on the release layer side of the film base “A70” by screen printing to a film thickness of 5 μm, and dried in a hot air thermostat at 120 ° C. for 5 minutes to produce a film with an intermediate layer did.

(Preparation of film with adhesive layer)
A PET film “A31” (manufactured by Teijin DuPont Films, Inc., thickness: 50 μm, film size: 250 mm × 300 mm) provided with a silicone release layer was prepared as a film substrate for forming the adhesive layer. Acrylic resin “BR1122” (manufactured by Mitsubishi Rayon Co., Ltd.) is used as the main agent, and an isocyanurate-based curing agent (“TPA100” manufactured by Asahi Kasei Co., Ltd.) is used as the curing agent. 1 was used as an adhesive layer paste. The adhesive layer paste is applied to the release layer side of the film “A31” using a Mayer bar so that the film thickness becomes 5 μm, dried in a hot air thermostat at 120 ° C. for 5 minutes, and then 50 ° C. for 72 hours. The adhesive layer was heat cured to prepare a film with an adhesive layer.

(Preparation of applicator film (support))
As an applicator film (support), a PET film “SRL-0505” (manufactured by Lintec Corporation) coated with a slightly adhesive layer was prepared.

(Preparation of coating layer (black layer) paste)
A composite pigment of chromium oxide and copper oxide, glass frit, and organic binder were dispersed with three rolls to prepare a black layer paste. As an organic binder, an acrylic resin “BR102” (manufactured by Mitsubishi Rayon Co., Ltd.) dissolved in bis (2-butoxyethyl) ether (manufactured by Wako Pure Chemical Industries, Ltd.) is used. The ratio of the solid content mass (R) of the organic binder to the total mass (P) was adjusted to P / R = 80/20.

(Preparation of conductive paste)
As a paste for the conductive layer, a conductive paste “H4170” (manufactured by Shoei Chemical Industry Co., Ltd.) containing glass frit, Ag powder and an organic binder was prepared.

(Preparation of protective layer paste)
As a protective layer paste, methylcellulose “Marporose 60MP-4000” (manufactured by Matsumoto Yushi Seiyaku Co., Ltd.) is diluted to a solid content concentration of 2% by mass using a mixed solvent having a mass ratio of water and IPA of 8 to 2. And made.

(Transfer film production)
For the conductive pattern, the line width of the heater line was set to 200 μm, and the line length was adjusted so that the resistance value of the heating region was 90% or more of the whole. On the other hand, with respect to the lead wire, the wiring width is set to 2.5 mm so that the resistance value between the terminal portion and the heater wire is about 10% or less, and the conductive pattern shown in FIG. did.
On the other hand, the coating layer had the same shape as the conductive pattern, and the line width was about 400 μm thicker than the conductive pattern in order to completely cover the conductive pattern.

These conductive patterns and coating patterns were produced using screen printing.
First, a coating layer (black layer) for coating the conductive pattern is printed on the intermediate layer of the film with the intermediate layer, and dried by an IR dryer at about 70 ° C. for 3 minutes to a thickness of about 7 μm. did. Thereafter, printing was performed so that the conductive pattern did not protrude from the coating layer, and printing was performed with an IR dryer at about 100 ° C. for 3 minutes to a thickness of about 12 μm. Thereafter, printing was performed again so that the covering layer was covered with the conductive pattern, and drying was performed at 70 ° C. for 3 minutes using an IR dryer, and printing was performed so that the thickness became about 7 μm. Then, a protective layer was printed so as to cover the coating layer, and was dried by an IR dryer at 120 ° C. for 3 minutes, so that the thickness was about 5 μm.
Thereafter, the applicator film was attached to the protective layer side through a nip roller of a laminating apparatus so that the protective layer and the slightly adhesive layer face each other. As the nip roller at that time, the upper roller contacting the applicator film was a urethane rubber roller hardness of 65 °, the lower roller was an iron roller, and the application pressure was 0.5 MPa.
After laminating the applicator film, the film base “A70” of the film base with an intermediate layer is peeled off, and the applicator film is placed so that the intermediate layer and the adhesive layer face each other on the peeled surface (intermediate layer side) The transfer film was prepared by laminating in the same manner as in the above.

(Confirmation of anti-fogging effect)
The film “A31” of the film with the adhesive layer is peeled off from the transfer film, the adhesive layer side is attached to the soda lime glass plate which is the adherend, the applicator film is peeled off, and baked at 630 ° C. for 10 minutes. An anti-fogging heater was produced on the top. The glass plate was laminated glass by sandwiching an interlayer butyral between a single plate glass (thickness: about 2.0 mm) with an antifogging heater and a single plate glass (thickness: about 2.0 mm) (thickness: about 4. 8 mm).

Install the anti-fogging heater on the side of this laminated glass plate in an environment of 25 ° C, 60 percent Rh (high temperature side), and the other side on 5 ° C, 60 percent Rh (low temperature side). Condensation was generated on the surface of the glass plate on the attachment surface side.
When a DC voltage of 13.5 V was applied to the terminal portion of the anti-fogging heater with this condensation occurring, it was observed that the condensation started to clear after 1 minute had elapsed after application, and the condensation inside the heater wire gradually cleared. Later, condensation was completely removed. At that time, the average temperature of the linear pattern of the heater was about 80 ° C., and the glass temperature inside the heater wire was about 40 ° C. On the other hand, no rapid temperature increase due to voltage application was observed for the lead wires.

(Front glass with conductive pattern)
In the configuration shown in FIG. 8, the optical sensor system 22 is arranged on the windshield 21 having a thickness of 4.8 mm so as to acquire information outside the vehicle through the viewing window 31, and a surrounding area surrounding the viewing window 31 is separately provided. A conductive pattern having a heater wire was applied to the windshield 21. Since the configuration of the conductive pattern is the same as described above, the description of the same portion will be omitted, and only the difference will be described.
A current is supplied from the terminal portion to the conductive pattern, and the heater wire including the surrounding portion enclosing the viewing window is energized to increase the temperature of the heater wire, and the temperature of the viewing window 31 is also increased by heat conduction. As it rose, the condensation on the viewing window 31 was clear.

<Test Example 2>
Experiments were conducted to confirm the heat generation state of Comparative Examples 1 and 2 and Invention Examples 1 and 2 in which the lead wire and the heater wire in the linear pattern portion of the conductive pattern were different. In Comparative Examples 1 and 2 and Invention Examples 1 and 2, as shown in Table 1, the applied voltage was 13.5 V, and the line width and length of the lead wire and heater wire were changed. As shown, the resistance values of the lead wire and the heater wire and their resistance ratios are different. Table 2 also shows the experimental results in the heat generation state.

  As shown in Table 2, in Comparative Examples 1 and 2, where the ratio of the resistance value of the heater wire to the total resistance value of the linear pattern portion was less than 80%, the amount of heat generated by the lead wire was considerably large. It can be seen that the amount of heat generated by the heater wire has decreased. In contrast, in Invention Examples 1 and 2, where the ratio of the resistance value in the heater wire was 80% or more, the heat value in the heater wire could be increased while suppressing the heat value in the lead wire. .

DESCRIPTION OF SYMBOLS 1 Transfer film 2 Support body 3 Conductive pattern 4a, 4b Terminal part 5 Linear pattern part 6 Heater wire 7a, 7b Lead wire 8 Resistance adjustment part 9 Bending part 10 Line width restricting part 11 Protective layer 12 Intermediate layer 13 Adhesive layer 14 Covering layer 15 Substrate 21 Front glass 22 Optical sensor system 23 Bracket 24 Cover 31 Viewing window Ah Heated area Ps Surrounding place Pt Crossing place Lw Lead wire line width Lh Heater wire line width Ln Line width restriction length The

Claims (15)

On the support, a transfer film for an anti-fogging heater provided with one or more conductive patterns that can be peeled off from the support and transferred to an adherend,
The conductive pattern has a plurality of terminal portions for supplying a current to the conductive pattern from the outside, and a linear pattern portion extending continuously from the plurality of terminal portions, and the linear pattern portion However, a heater wire including an encircling portion extending so as to surround at least a part of the periphery of the heated region, and a plurality of lead wires connecting each of both end portions of the heater wire to each of the plurality of terminal portions. Consists of, including
For the anti-fogging heater, the ratio of the resistance value of the heater wire to the total resistance value of the linear pattern portion is 80% or more, and the ratio of the resistance of the lead wire to the total resistance value is 20% or less. Transfer film.   The transfer film for an anti-fogging heater according to claim 1, wherein the heater wire has a linear resistance adjusting portion that increases a resistance value of the heater wire at a connection position with the lead wire.   The transfer film for an anti-fogging heater according to claim 1, wherein the heater wire includes a crossing portion that extends from a part of the surrounding portion and across a heated region surrounded by the surrounding portion.   The anti-fogging heater according to any one of claims 1 to 3, wherein the heater wire has a bent portion that bends at an angle of 90 ° or less, and the bent portion has an arc shape with a curvature radius R of 1 mm or more. Transfer film.   The line width of the lead wire is set to be equal to or larger than the line width of the heater wire, and the lead wire is connected to the heater wire at a position where the line width is gradually reduced toward the heater wire. The transfer film for an anti-fogging heater according to any one of claims 1 to 4.   The antifogging heater transfer according to claim 5, wherein the lead wire has a line width of 1 mm to 5 mm, the heater wire has a line width of 0.1 mm to 0.5 mm, and the length of the line width restricting portion is 5 mm or more. the film.   The transfer film for an anti-fogging heater according to any one of claims 1 to 6, wherein the conductive pattern includes at least a conductive material, glass frit, and an organic substance that can be removed by baking.   The transfer film for an anti-fogging heater according to any one of claims 1 to 7, wherein the linear pattern is covered with a coating layer containing at least a glass frit and an organic binder that can be removed by firing. Laminated on the support, and having a protective layer in which the conductive pattern is disposed, an intermediate layer laminated on the protective layer, and an adhesive layer laminated on the intermediate layer,
The transfer film for an anti-fogging heater according to any one of claims 1 to 8, wherein the protective layer, the intermediate layer, and the adhesive layer are made of an organic material that can be removed by baking to transfer the conductive pattern to the adherend. . A vehicle windshield having a glass plate and capable of arranging an optical sensor system that acquires information outside the vehicle through a viewing window of the glass plate,
A conductive pattern is provided on the glass plate, and the conductive pattern has a plurality of terminal portions for supplying a current to the conductive pattern from the outside, and a linear shape continuously extending from the plurality of terminal portions. A heater wire including an encircling portion that extends around at least a part of the periphery of the viewing window, and each of both end portions of the heater wire includes a plurality of terminal portions. A plurality of lead wires connected to each other,
The ratio of the resistance value of the heater wire to the total resistance value of the linear pattern portion is 80% or more, and the ratio of the resistance of the lead wire to the total resistance value is 20% or less. .   The vehicle windshield according to claim 10, wherein the heater wire has a linear resistance adjusting portion that increases a resistance value of the heater wire at a connection position with the lead wire.   The vehicle windshield according to claim 10 or 11, wherein the heater wire includes a crossing portion that extends from a part of the surrounding portion to cross a heated region surrounded by the surrounding portion.   The vehicle front according to any one of claims 10 to 12, wherein the heater wire has a bent portion that bends at an angle of 90 ° or less, and the bent portion has an arc shape with a radius of curvature R of 1 mm or more. Glass.   The line width of the lead wire is set to be equal to or larger than the line width of the heater wire, and the lead wire is connected to the heater wire at a position where the line width is gradually reduced toward the heater wire. The vehicle windshield as described in any one of Claims 10-13 which has.   The vehicle windshield according to claim 14, wherein the lead wire has a line width of 1 mm to 5 mm, the heater wire has a line width of 0.1 mm to 0.5 mm, and the length of the line width restricting portion is 5 mm or more.