Patent Description:
In recent years, safety performance of automobiles has dramatically improved. For example, a safety system has been proposed that detects a distance to a preceding vehicle and its speed and automatically operates a brake when the preceding vehicle comes abnormally close in order to avoid collision with the preceding vehicle. Such a system measures the distance to the preceding vehicle or the like using a laser radar or a camera. The laser radar or camera is typically arranged on the inner side of a windshield and measurement is performed by emitting light such as infrared rays forward (Patent Literature <NUM>, for example).

As described above, measurement devices such as the laser radar and the camera are arranged on the inner surface side of a glass plate that constitutes the windshield and light is emitted or received through the glass plate. However, the glass plate may fog up on cold days and in cold regions. If the glass plate fogs up, there is a risk that the measurement devices cannot accurately emit or receive light. This may result in a failure to accurately calculate a distance between vehicles or the like.

The above-described problem may arise not only in measurement devices that measure a distance between vehicles but also in general information acquisition devices that acquire information from the outside of a vehicle by receiving light such as a rain sensor, a light sensor, or an optical beacon, for example.

<CIT> discloses a windshield for an automobile to which an information acquisition device for acquiring information from the outside of a vehicle by emitting and/or receiving light can be installed, the windshield comprising: an outer glass plate, an inner glass plate that is arranged opposite to the outer glass plate, and an intermediate film that is arranged between the outer glass plate and the inner glass plate wherein the windshield includes an information acquisition region that is to be located opposite to the information acquisition device and through which the light passes, the intermediate film including a polyvinylbutyral layer and a heating element that is supported by the adhesive layer. In one embodiment, the heating element includes in a region that corresponds to the information acquisition region a pair of electrical connection means that are arranged such that the information acquisition region is interposed therebetween, and a plurality of thin tungsten wires that are connected in parallel so as to connect the bus bars to each other.

To solve the above-described problem, arranging heating wires in a region through which light passes has been proposed. However, although generation of a sufficient amount of heat is required in this region to accurately acquire information using an information acquisition device, the required amount of heat cannot be generated by merely arranging heating wires. The present invention was made to solve the above-described problem, and it is an object of the present invention to provide a windshield that enables heat generation such that information can be accurately acquired using an information acquisition device.

A windshield for an automobile to which an information acquisition device for acquiring information from the outside of a vehicle by emitting and/or receiving light can be installed, the windshield including:.

The windshield according to Aspect <NUM> or <NUM>, wherein the information acquisition region has an area not larger than <NUM><NUM>.

The windshield according to any one of Aspects <NUM> to <NUM>, wherein adjacent first heating wires of the first heating wires are not connected to each other.

The windshield according to any one of Aspects <NUM> to <NUM>, wherein the information acquisition region is located within a distance of <NUM> from an edge of the outer glass plate.

The windshield according to any one of Aspects <NUM> to <NUM>, wherein the plurality of first heating wires extend in an up-down direction.

The windshield according to any one of Aspects <NUM> to <NUM>, wherein a pitch between the first heating wires is <NUM> to <NUM>.

The windshield according to any one of Aspects <NUM> to <NUM>, wherein the heat generation layer further includes:.

The windshield according to Aspect <NUM>, wherein one of the first side bus bar and the second side bus bar constitutes a single piece together with either of the bus bars that are arranged such that the information acquisition region is interposed therebetween.

The windshield according to Aspect <NUM> or <NUM>, wherein the second heating wires are arranged in a view field region outside the information acquisition region,.

The windshield according to any one of Aspects <NUM> to <NUM>, wherein a pitch between the first heating wires is smaller than a pitch between the second heating wires.

With the windshield according to the present invention, heat can be generated such that information can be accurately acquired using the information acquisition device.

The following describes a first embodiment of a windshield according to the present invention with reference to the drawings. <FIG> is a plan view of the windshield according to the present embodiment, <FIG> is a cross-sectional view showing a state in which the windshield shown in <FIG> is attached to a vehicle, and <FIG> is a cross-sectional view taken along line A-A in <FIG>. As shown in <FIG>, the windshield according to the present embodiment includes an outer glass plate <NUM>, an inner glass plate <NUM>, and an interlayer <NUM> that is arranged between these glass plates <NUM> and <NUM>. Further, a mask layer <NUM> is layered on at least one of the outer glass plate <NUM> and the inner glass plate <NUM>, and a measurement unit <NUM>, such as a laser radar, that measures a distance between vehicles is attached to a position corresponding to the mask layer <NUM>. The following describes respective members.

Each of the glass plates <NUM> and <NUM> is formed into a rectangular shape that includes a lower side <NUM> that is longer than an upper side <NUM>. That is, each of the glass plates is formed into a trapezoidal shape surrounded by the upper side <NUM>, the lower side <NUM>, and two sides (a left side <NUM> and a right side <NUM>). Known glass plates can be used as the glass plates <NUM> and <NUM>, and these glass plates can be made of heat-ray absorbing glass, regular clear glass, green glass, or UV green glass. However, the glass plates <NUM> and <NUM> need to realize visible light transmittance that conforms to the safety standards of the country in which the automobile is to be used. For example, adjustments can be made so that the outer glass plate <NUM> ensures a required solar absorptance and the inner glass plate <NUM> provides visible light transmittance that meets safety standards. The following shows one example of compositions of clear glass, heat-ray absorbing glass, and soda lime-based glass.

With regard to the composition of heat-ray absorbing glass, a composition obtained, which is based on the composition of clear glass, by setting the ratio of the total iron oxide (T-Fe<NUM>O<NUM>) in terms of Fe<NUM>O<NUM> to <NUM> to <NUM> mass%, the ratio of CeO<NUM> to <NUM> to <NUM> mass%, and the ratio of TiO<NUM> to <NUM> to <NUM> mass%, and reducing the components (mainly SiO<NUM> and Al<NUM>O<NUM>) forming the framework of glass by an amount corresponding to the increases in T-Fe<NUM>O<NUM>, CeO<NUM>, and TiO<NUM> can be used, for example.

As described above, each of the glass plates <NUM> and <NUM> is formed into a rectangular shape, but the ratio between the upper side <NUM> and the lower side <NUM> can be set to <NUM>:<NUM> to <NUM>:<NUM>, for example. If the upper side has a length of <NUM>, the length of the lower side can be set to <NUM> to <NUM>, for example. Specifically, the length of the upper side can be set to <NUM> and the length of the lower side can be set to <NUM>. Note that the above-described ratio is a ratio in a two-dimensional plane to which the windshield is projected from the front side.

That is, although <FIG> shows an example in which the lower side <NUM> is long, the present invention can also be applied to a windshield in which the upper side <NUM> is long. For example, in the case of a windshield of a compact car for one person, if the upper side has a length of <NUM>, the length of the lower side can be set to <NUM> to <NUM>. Specifically, the length of the upper side can be set to <NUM> and the length of the lower side can be set to <NUM>.

Although there is no particular limitation on the thickness of a laminated glass according to the present embodiment, the total thickness of the outer glass plate <NUM> and the inner glass plate <NUM> is preferably set to <NUM> to <NUM>, more preferably <NUM> to <NUM>, and particularly preferably <NUM> to <NUM>, from the viewpoint of weight reduction. As described above, it is necessary to reduce the total thickness of the outer glass plate <NUM> and the inner glass plate <NUM> in order to reduce the weight, and therefore, although there is no particular limitation on the thicknesses of the outer glass plate <NUM> and the inner glass plate <NUM>, the thicknesses of these glass plates can be determined as described below, for example.

Durability against external damage and impact resistance are mainly required for the outer glass plate <NUM>. For example, if the laminated glass is used as a windshield of an automobile, impact resistance against flying objects such as small stones is required. On the other hand, the weight increases as the thickness increases, which is not preferable. From this viewpoint, the thickness of the outer glass plate <NUM> is preferably <NUM> to <NUM>, and more preferably <NUM> to <NUM>. It is possible to determine the thickness to employ according to the use of the glass.

The thickness of the inner glass plate <NUM> can be made equal to the thickness of the outer glass plate <NUM>, but in order to reduce the weight of the laminated glass, for example, the thickness of the inner glass plate <NUM> can be made smaller than that of the outer glass plate <NUM>. Specifically, when the strength of the glass is taken into consideration, the thickness is preferably <NUM> to <NUM>, more preferably <NUM> to <NUM>, and particularly preferably <NUM> to <NUM>. The thickness is yet more preferably <NUM> to <NUM>. For the inner glass plate <NUM> as well, it is possible to determine the thickness to employ according to the use of the glass.

Note that if heating wires <NUM> included in the interlayer <NUM>, which will be described later, are arranged at the center of the interlayer <NUM> in the thickness direction, the thicknesses of the glass plates <NUM> and <NUM> may also be made different from each other. Which glass plate is made thicker depends on the main use of the heating wires <NUM>.

The outer glass plate <NUM> and the inner glass plate <NUM> according to the present embodiment may also have curved shapes. However, it is supposed that, if each of the glass plates <NUM> and <NUM> has a curved shape, the larger the depth of bend is, the lower the sound insulation performance is. The depth of bend is an amount indicating the bend of a glass plate, and when a straight line L connecting the center of an upper side and the center of a lower side of the glass plate is set, the greatest distance between this straight line L and the glass plate is defined as the depth of bend D.

Also, a glass plate having a curved shape does not have a large difference in sound transmission loss (STL) if the depth of bend D is within a range of <NUM> to <NUM>, but it can be found that the sound transmission loss is reduced in a frequency band of <NUM> or lower when compared to a glass plate having a flat shape. Therefore, a smaller depth of bend D is preferable when a glass plate having a curved shape is manufactured. Specifically, the depth of bend D is preferably smaller than <NUM>, more preferably smaller than <NUM>, and particularly preferably smaller than <NUM>.

Here, one example of a method for measuring the thickness of a curved glass plate will be described. First, with respect to the measurement position, the measurement is performed at two positions: an upper position and a lower position on a center line extending in the up-down direction at the center of the glass plate in the left-right direction. Although there is no particular limitation on the measurement device, a thickness gauge such as SM-<NUM> manufactured by TECLOCK Co. can be used, for example. During measurement, the glass plate is arranged such that its curved surface is placed on a flat surface, and an end portion of the glass plate is sandwiched and measured with the above-described thickness gauge.

As shown in <FIG>, the mask layer <NUM> that is formed using ceramic of a dark color such as black is layered on a peripheral edge of the windshield. The mask layer <NUM> is for blocking the view from the inside or the outside of the vehicle, and includes a peripheral portion <NUM> that is layered along the four sides <NUM> to <NUM> of the windshield and a center portion <NUM> that extends downward from the vicinity of the center of a portion of the peripheral portion <NUM> that corresponds to the upper side of the windshield <NUM>. A rectangular window portion <NUM> is formed in the center portion <NUM>. The window portion <NUM> is a portion in which the mask layer <NUM> is not formed and through which the inside and the outside of the windshield can be seen. The above-described measurement unit <NUM> is arranged on the vehicle interior side and is configured to acquire information from the outside of the vehicle via the window portion <NUM>. Note that although there is no particular limitation on the size of the window portion <NUM>, the size can be set to be not larger than <NUM><NUM>, for example. Also, the window portion <NUM> can be arranged on the lower side of the upper side of the windshield within a distance of <NUM> from the upper side, for example.

Various configurations can be employed for the mask layer <NUM>, for example, the mask layer <NUM> can be provided only on an inner surface of the outer glass plate <NUM> or an inner surface of the inner glass plate <NUM>, or can be provided on both the inner surface of the outer glass plate <NUM> and the inner surface of the inner glass plate <NUM>. Although <FIG> shows one example in which the mask layer <NUM> is arranged on the inner surface of the inner glass plate <NUM>, the mask layer <NUM> is omitted in <FIG>. Although ceramic and various materials can be used for the mask layer <NUM>, the mask layer can have the following composition, for example.

Although a ceramic layer can be formed using a screen printing process, the layer can alternatively be produced by transferring a transfer film for firing to the glass plate and firing it. If screen printing is employed, the ceramic layer can be formed under the conditions that a polyester screen of <NUM> mesh is used, the coating thickness is <NUM>, the tension is <NUM>, the squeegee hardness is <NUM> degrees, the attachment angle is <NUM>°, and the printing speed is <NUM>/s, and performing drying in a drying furnace at <NUM> for <NUM> minutes, for example.

Alternatively, the mask layer <NUM> can be formed by attaching a blocking film that is made of a dark colored resin, instead of laminating ceramic.

Next, the interlayer <NUM> will be described. The interlayer <NUM> is constituted by three layers, i.e., a heat generation layer <NUM> and a pair of adhesive layers <NUM> and <NUM> that sandwich the heat generation layer <NUM>. In the following description, an adhesive layer arranged on the outer glass plate <NUM> side will be referred to as a first adhesive layer <NUM> and an adhesive layer arranged on the inner glass plate <NUM> side will be referred to as a second adhesive layer <NUM>.

First, the heat generation layer <NUM> will be described. The heat generation layer <NUM> is for heating a region (information acquisition region) that corresponds to the window portion <NUM> of the mask layer <NUM> in each of the glass plates <NUM> and <NUM> to melt frost or remove fog. Specifically, the heat generation layer includes a sheet-shaped base material <NUM>, a first bus bar <NUM>, a second bus bar <NUM>, and a plurality of heating wires <NUM>, the bus bars and the heating wires being arranged on the base material <NUM>. The base material <NUM> may have the same size as the glass plates <NUM> and <NUM>, but may also be arranged only in a region that corresponds to the center portion <NUM> of the mask layer <NUM>. Alternatively, a configuration is also possible in which the base material <NUM> is smaller than the adhesive layers <NUM> and <NUM> and a peripheral portion of the base material <NUM> is arranged inward of peripheral portions of the adhesive layers <NUM> and <NUM>. The first bus bar <NUM>, the second bus bar <NUM>, and the plurality of heating wires <NUM> are arranged at positions corresponding to the center portion <NUM> of the mask layer <NUM>, and in particular, the plurality of heating wires <NUM> are arranged side by side across the window portion <NUM>. A specific configuration will be described below.

As shown in <FIG>, the first bus bar <NUM> is formed into a band shape and extends along an upper side of the above-described window portion <NUM>, and the second bus bar <NUM> is formed into a band shape and extends along a lower side of the window portion <NUM>. The second bus bar <NUM> is formed so as to slightly protrude rightward from the lower side of the window portion <NUM>. The plurality of heating wires <NUM> are connected in parallel while extending in the up-down direction, with the bus bars <NUM> and <NUM> serving as electrodes. Further, a band-shaped first connection member <NUM> is connected to a left end portion of the first bus bar <NUM>, and a band-shaped second connection member <NUM> is connected to a right end portion of the second bus bar. The first connection member <NUM> and the second connection member <NUM> are for connecting the bus bars <NUM> and <NUM> to connection terminals (a positive electrode terminal and a negative electrode terminal, not shown) and formed into sheet shapes using an electrically-conductive material. Therefore, the connection members <NUM> and <NUM> extend upward toward the upper side of the windshield and are respectively connected to a connection terminal of a positive electrode and a connection terminal of a negative electrode. A power supply voltage of <NUM> to <NUM> V is applied to these connection terminals, for example.

Note that the connection members <NUM> and <NUM> are respectively sandwiched between the first bus bar <NUM> and the second adhesive layer <NUM> and between the second bus bar <NUM> and the second adhesive layer <NUM>. The connection members <NUM> and <NUM> are respectively fixed to the bus bars <NUM> and <NUM> using a fixingmaterial such as solder. It is preferable to use solder that has a low melting point not higher than <NUM>, for example, as the fixing material so that fixing can be performed using an autoclave at the same time when the windshield is assembled as described later. However, another connection method may also be used.

The width of each of the bus bars <NUM> and <NUM> in the up-down direction is preferably <NUM> to <NUM>, and more preferably <NUM> to <NUM>, for example. If the width of the bus bars <NUM> and <NUM> is smaller than <NUM>, the heat generation amount of the bus bars increases, and consequently the heat generation amount of the heating wires <NUM> decreases and a desired heat generation amount cannot be obtained. On the other hand, if the width of the bus bars <NUM> and <NUM> is larger than <NUM>, there is a risk that the bus bars <NUM> and <NUM> may obstruct the view. Each of the bus bars <NUM> and <NUM> need not be formed so as to extend exactly along the base material <NUM>. That is, the bus bars need not be completely parallel to edges of the base material <NUM>, and may also be curved.

Next, the heating wires <NUM> will be described. Snow, frost, and fog on a surface of the window portion <NUM> are removed as a result of heat being generated by the heating wires <NUM>. Therefore, the heating wires <NUM> are required to have a heat generation amount that is large enough to melt frost or the like, but on the other hand, it is necessary to keep the heating wires <NUM> from inhibiting the passage of light in order to acquire information from the outside of the vehicle via the window portion <NUM> using the measurement unit <NUM>, which will be described later. Therefore, the heat generation amount, dimensions such as the wire width and the pitch, and the like of the heating wires <NUM> are set in the present embodiment as described below.

The heat generation amount of the heating wires <NUM> can be calculated using the following Expression (<NUM>). Further, a relationship between the resistance of the heating wires <NUM> and the length and the cross-sectional area of the heating wires <NUM> is as shown in Expression (<NUM>). <MAT> <MAT> W: power, E: voltage, I: current, R: resistance, L: length, A: cross-sectional area, ρ: electrical resistivity.

According to the above Expressions (<NUM>) and (<NUM>), the heat generation amount of the heating wires <NUM> can be increased by, for example, reducing the resistance R, reducing the length L of the heating wires <NUM>, increasing the cross-sectional area A of the heating wires <NUM>, or reducing the electrical resistivity ρ. Also, the heat generation amount at the window portion <NUM> can be increased by increasing the number of heating wires <NUM> to increase a total cross-sectional area A. The following describes the heating wires <NUM> in view of the foregoing.

The plurality of heating wires <NUM> are formed so as to extend in the up-down direction and connect the bus bars <NUM> and <NUM> to each other. Each of the heating wires <NUM> can be formed into a straight line shape or various shapes such as a wave shape. In particular, if each of the heating wires <NUM> is formed into a sine wave shape, heat can be uniformly distributed and the heating wires <NUM> can be kept from optically obstructing a view field of the windshield. At this time, the crimp ratio of the heating wires <NUM> can be set to <NUM>% or less, for example. The crimp ratio is the ratio of an actual length of each heating wire <NUM> (the length measured along a curved line) to a length between both ends of the heating wire <NUM> on the heat generation layer <NUM>.

The wire width of each heating wire <NUM> is preferably <NUM> to <NUM> pm, and more preferably <NUM> to <NUM>. The wire width is even more preferably <NUM> to <NUM>. Heating wires having a smaller wire width such as a wire width not larger than <NUM> are less likely to be seen, and therefore are suitable for use in the window portion <NUM> through which light emitted from a sensor passes as is the case with the present embodiment. Also, the smaller the wire width is, the smaller the thickness of the heating wires <NUM> needs to be made as described later, and consequently the cross-sectional area of the heating wires <NUM> is reduced and the heat generation amount is increased. On the other hand, if the wire width is too small, there is a risk that the heating wires cannot be manufactured or the heat generation amount will be too large. Note that the wire width refers to the largest wire width of a cross-sectional shape of the heating wires <NUM>. Since the cross-sectional shape of the heating wires <NUM> is a trapezoid, the length of the lower side is the wire width. The width of the heating wires <NUM> can be measured using a microscope such as VHX-<NUM> (manufactured by Keyence Corporation) at 1000x magnification, for example.

The wire width of the heating wires <NUM> need not be constant and may also be varied. For example, the heating wires can be formed so as to become gradually narrow or thick downward. Alternatively, the wire width may also be varied between different regions. For example, the wire width may be varied between an upper portion and a lower portion of the heating wires <NUM>. Such a variation of the wire width can be applied to an arrangement in which the pitch between the heating wires <NUM> varies, for example. In a case in which the plurality of heating wires <NUM> are arranged in a trapezoidal window portion <NUM>, for example, if the pitch between the heating wires <NUM> increases downward, the wire width of the heating wires <NUM> can be reduced downward.

The thickness of each heating wire <NUM> is not larger than the wire width. In other words, the aspect ratio of a cross section of each heating wire <NUM> is not larger than <NUM>. If the thickness of the heating wires <NUM> is larger than the wire width, the heating wires <NUM> may fall over on the base material <NUM>, for example, giving rise to a difficulty in manufacture, or there is a risk of breaking of the heating wires.

Although there is no particular limitation on the lower limit of the pitch between adjacent heating wires <NUM>, the pitch is preferably <NUM> to <NUM>, and more preferably <NUM> to <NUM>, for example. If the pitch is small, there is a risk that acquisition of information performed using the measurement unit may be inhibited, and if the pitch is large, there is a risk that the window portion cannot be sufficiently heated. In view of this, it is preferable to set the pitch between the heating wires as described above. Note that the pitch is a length that is obtained by adding the wire width of a heating wire <NUM> to the length of a space between adjacent heating wires <NUM>, rather than the length of the space between adjacent heating wires <NUM>. If the heating wires <NUM> have a sine wave shape, the distance between center lines of the heating wires <NUM> is the pitch between the heating wires <NUM>.

When a voltage of <NUM>. <NUM> V is applied between the bus bars <NUM> and <NUM>, for example, the heat generation amount per unit length of each heating wire <NUM> is preferably not larger than <NUM> W/m, more preferably not larger than <NUM> W/m, and particularly preferably not larger than <NUM> W/m. In order to effectively melt frost or the like using such heating wires <NUM>, the heat generation amount per unit area of the window portion <NUM> is preferably at least <NUM> W/m<NUM>, more preferably at least <NUM> W/m<NUM>, and particularly preferably at least <NUM> W/m<NUM>.

The following shows one example of specifications of the heating wires <NUM> arranged in the window portion <NUM> such as that shown in <FIG>.

Next, materials of the heat generation layer <NUM> will be described. The base material <NUM> is a transparent film that supports the bus bars <NUM> and <NUM> and the heating wires <NUM>. Although there is no particular limitation on the material of the base material <NUM>, the base material <NUM> can be made of polyethylene terephthalate, polyethylene, polymethyl methacrylate, polyvinyl chloride, polyester, polyolefin, polycarbonate, polystyrene, polypropylene, nylon, or the like, for example. Alternatively, the base material can also be made of a polyvinyl butyral resin (PVB), ethylene vinyl acetate (EVA), or the like. The bus bars <NUM> and <NUM> and the heating wires <NUM> can be made of the same material, and can be made of various materials such as copper (or tin-plated copper), gold, aluminum, magnesium, cobalt, tungsten, silver, or an alloy of any of these metals. Among these, silver, copper, gold, and aluminum, each of which has an electrical resistivity not larger than <NUM> × <NUM>-<NUM> Om, are preferably used.

Next, a method for forming the bus bars <NUM> and <NUM> and the heating wires <NUM> will be described. The bus bars <NUM> and <NUM> and the heating wires <NUM> can be formed by arranging thin wires or the like formed in advance on the base material <NUM>, but in order to make the wire width of the heating wires <NUM> smaller, the heating wires <NUM> can be formed by forming a pattern on the base material <NUM>. There is no particular limitation on the method for forming the pattern, and the pattern can be formed using various methods such as printing, etching, and transferring. At this time, the bus bars <NUM> and <NUM> and the heating wires <NUM> can be formed separately or as a single piece. Note that materials being formed "as a single piece" means that the materials are continuous to each other (i.e., seamless) and there is no interface between the materials.

It is also possible to form the bus bars <NUM> and <NUM> on the base material <NUM> and remove portions of the base material <NUM> corresponding to the bus bars <NUM> and <NUM>, while leaving a portion of the base material <NUM> for the heating wires <NUM>. Thereafter, the heating wires <NUM> can be arranged on the base material <NUM> between the bus bars <NUM> and <NUM>.

In particular, etching can be performed using the following process, for example. First, dry lamination of metal foil is performed on the base material <NUM> via a primer layer. Copper foil can be used as the metal foil, for example. A pattern of the bus bars <NUM> and <NUM> and the plurality of heating wires <NUM> can be formed as a single piece on the base material <NUM> by performing chemical etching on the metal foil using photolithography. In particular, in a case in which the wire width of the heating wires <NUM> is made small, as is the case with the present embodiment, thin metal foil is preferably used, and it is possible to form a thin metal layer (e.g., <NUM> or less) on the base material <NUM> through deposition, sputtering, or the like, and thereafter perform patterning using photolithography. Note that surfaces of the heating wires <NUM>, i.e., surfaces on the inner glass plate <NUM> side can also be made black to make the heating wires <NUM> less visible from the vehicle interior side. The heating wires can be made black through plating using a material such as copper nitride, copper oxide, nickel nitride, or nickel chromium.

The adhesive layers <NUM> and <NUM> are sheet-shaped members that sandwich the heat generation layer <NUM> and are bonded to the glass plates <NUM> and <NUM>. The adhesive layers <NUM> and <NUM> have the same size as the glass plates <NUM> and <NUM>. Although these adhesive layers <NUM> and <NUM> can be formed using various materials, the adhesive layers can be formed using a polyvinyl butyral resin (PVB), ethylene vinyl acetate (EVA), or the like. In particular, polyvinyl butyral resin has good adhesion to the glass plates and also has good penetration resistance, and therefore is preferable. Note that layers of a surfactant may also be provided between the heat generation layer <NUM> and the adhesive layers <NUM> and <NUM>. With use of such a surfactant, surfaces of the layers can be modified to improve adhesive force. Although the adhesive layers <NUM> and <NUM> have the same size as the glass plates <NUM> and <NUM>, the heat generation layer <NUM> need not have the same size as the adhesive layers <NUM> and <NUM>, and can also be made small as described above.

The total thickness of the interlayer <NUM> is not particularly specified, but is preferably <NUM> to <NUM>, more preferably <NUM> to <NUM>, and particularly preferably <NUM> to <NUM>. The thickness of the base material <NUM> of the heat generation layer <NUM> is preferably <NUM> to <NUM>, and more preferably <NUM> to <NUM>. On the other hand, the thickness of each of the adhesive layers <NUM> and <NUM> is preferably larger than the thickness of the heat generation layer <NUM>, specifically, preferably <NUM> to <NUM>, and more preferably <NUM> to <NUM>. The thicknesses of the adhesive layers <NUM> and <NUM> may be the same as or different from each other. In order to make the second adhesive layer <NUM> and the base material <NUM> be in close contact with each other, the thickness of the bus bars <NUM> and <NUM> and the heating wires <NUM>, which are sandwiched between the second adhesive layer <NUM> and the base material <NUM>, is preferably <NUM> to <NUM>.

The thicknesses of the heat generation layer <NUM> and the adhesive layers <NUM> and <NUM> can be measured as described below, for example. First, a cross section of the laminated glass is enlarged by a factor of <NUM> and displayed using a microscope (e.g., VH-<NUM> manufactured by Keyence Corporation). Then, the thicknesses of the heat generation layer <NUM> and the adhesive layers <NUM> and <NUM> are visually identified and measured. At this time, in order to eliminate variations seen in visual identification, measurement is performed five times, and an average value is taken as the thickness of the heat generation layer <NUM> or the adhesive layer <NUM> or <NUM>.

Note that the thicknesses of the heat generation layer <NUM> and the adhesive layers <NUM> and <NUM> of the interlayer <NUM> are not required to be constant over the entire surface. For example, the heat generation layer <NUM> and the adhesive layers <NUM> and <NUM> can also have a wedge shape suited to a laminated glass that is used for a head-up display. In this case, the thicknesses of the heat generation layer <NUM> and the adhesive layers <NUM> and <NUM> of the interlayer <NUM> are measured at a position with the smallest thicknesses, i. , in the lowest side portion of the laminated glass. If the interlayer <NUM> has a wedge shape, the outer glass plate <NUM> and the inner glass plate <NUM> are not arranged in parallel, but it should be construed that such an arrangement is also included in the glass plates in the present invention. That is, the present invention includes the arrangement of the outer glass plate <NUM> and the inner glass plate <NUM> when the interlayer <NUM> that includes the heat generation layer <NUM> and the adhesive layers <NUM> and <NUM> whose thicknesses increase at a rate of change of <NUM> or less per meter is used, for example.

Next, the measurement unit will be described with reference to <FIG>. The measurement unit <NUM> is constituted by a bracket (not shown) that is fixed to the inner surface of the inner glass plate <NUM>, a sensor (information acquisition device, not shown) that is supported by the bracket, and a cover (not shown) that covers the bracket and the sensor from the vehicle interior side. Note that the sensor is supported by the bracket fixed to the inner glass plate <NUM> and is not in contact with the inner glass plate <NUM>. Accordingly, it can be said that the sensor is arranged in the vicinity of the inner glass plate <NUM>.

An opening is formed in the bracket, and the sensor is configured to emit light and receive light from the window portion <NUM> of the mask layer <NUM> via the opening.

After a non-illustrated harness or the like is attached, the cover is attached to the bracket from the vehicle interior side. As a result, the sensor and the bracket cannot be seen from the vehicle interior side. Note that the measurement unit <NUM> cannot be seen from the vehicle exterior side except through the window portion <NUM> as a result of the center portion <NUM> of the mask layer <NUM> being provided.

In such a measurement unit, pulses of laser light are emitted from the sensor. A distance from the self-vehicle to a preceding vehicle or an obstacle is calculated based on a time it takes to receive the laser light reflected from the preceding vehicle or the obstacle. The calculated distance is transmitted to an external device and used to control a brake or the like.

Next, a method for manufacturing the windshield will be described. First, a manufacturing line of the glass plates will be described.

Here, a mold will be described in detail with reference to <FIG> is a side view of furnaces through which the mold passes and <FIG> is a plan view of the mold. As shown in <FIG>, a mold <NUM> includes a mold main body <NUM> having the shape of a frame that mostly matches the external forms of the glass plates <NUM> and <NUM>. Since this mold main body <NUM> has the shape of a frame, there is an interior space <NUM> that vertically penetrates the inner side of the mold main body. Peripheral portions of the glass plates <NUM> and <NUM> each having a flat plate shape are placed on an upper surface of the mold main body <NUM>. Accordingly, heat is applied to the glass plates <NUM> and <NUM> via the interior space <NUM> by a heater (not shown) that is arranged below the glass plates. When heat is applied, the glass plates <NUM> and <NUM> soften and curve downward under their own weight. In some cases, a shield plate <NUM> for shielding the glass plates from heat is arranged on an inner peripheral edge of the mold main body <NUM> to enable adjustment of heat applied to the glass plates <NUM> and <NUM>. The heater can be arranged above the mold <NUM> as well as below the mold.

After the above-described shield layer <NUM> is layered on the outer glass plate <NUM> and the inner glass plate <NUM> having the flat plate shape, the outer glass plate <NUM> and the inner glass plate <NUM> are superimposed and passed through a heating furnace <NUM> in a state of being supported by the above-described mold <NUM> as shown in <FIG>. When the glass plates <NUM> and <NUM> are heated to around the softening point in the heating furnace <NUM>, portions of the glass plates inward of peripheral portions curve downward under their own weight and thus the glass plates are molded into a curved shape. Subsequently, the glass plates <NUM> and <NUM> are conveyed from the heating furnace <NUM> to an annealing furnace <NUM> to be subjected to annealing treatment. Thereafter, the glass plates <NUM> and <NUM> are conveyed out of the annealing furnace <NUM> and cooled.

After the outer glass plate <NUM> and the inner glass plate <NUM> are molded as described above, subsequently, the interlayer <NUM> is sandwiched between the outer glass plate <NUM> and the inner glass plate <NUM>. Specifically, first, the outer glass plate <NUM>, the first adhesive layer <NUM>, the heat generation layer <NUM>, the second adhesive layer <NUM>, and the inner glass plate <NUM> are layered in that order. At this time, the heat generation layer <NUM> is arranged such that a surface of the heat generation layer <NUM> on which the first bus bar <NUM> and the like are formed faces the second adhesive layer <NUM> side. Next, the connection members <NUM> and <NUM> are inserted between the heat generation layer <NUM> and the second adhesive layer <NUM> from cutouts <NUM> and <NUM>. At this time, solder that has a low melting point and serves as a fixing material is applied to the connection members <NUM> and <NUM> and is arranged on the bus bars <NUM> and <NUM>.

The resultant laminate including the glass plates <NUM> and <NUM>, the interlayer <NUM>, and the connection members <NUM> and <NUM> is placed into a rubber bag and preliminarily bonded together at about <NUM> to <NUM> under vacuum suction. Preliminary bonding can be performed using another method, and the following method can also be employed. For example, the above-described laminate is heated at <NUM> to <NUM> in an oven. Next, this laminate is pressed by a roller at <NUM> to <NUM> MPa. Subsequently, this laminate is again heated at <NUM> to <NUM> in an oven and thereafter again pressed by a roller at <NUM> to <NUM> MPa. Thus, preliminary bonding is finished.

Next, permanent bonding is performed. The preliminarily bonded laminate is permanently bonded using an autoclave at a pressure of <NUM> to <NUM> atmospheres and at <NUM> to <NUM>, for example. Specifically, permanent bonding can be performed under the conditions of a pressure of <NUM> atmospheres and <NUM>, for example. Through the above-described preliminary boding and permanent bonding, the adhesive layers <NUM> and <NUM> are bonded to the glass plates <NUM> and <NUM> in a state of sandwiching the heat generation layer <NUM>. Also, the solder on the connection members <NUM> and <NUM> is molten and the connection members <NUM> and <NUM> are respectively fixed to the bus bars <NUM> and <NUM>. Thus, a laminated glass according to the present embodiment is manufactured. Note that a curved windshield can also be manufactured using another method, for example, pressing.

The windshield configured as described above is attached to a vehicle body and connection terminals are fixed to the connection members <NUM> and <NUM>. When electricity is passed through the connection terminals, a current is applied to the heating wires <NUM> via the connection members <NUM> and <NUM> and the bus bars <NUM> and <NUM>, and heat is generated. By generating heat as described above, it is possible to remove fog from a vehicle interior side surface of the window portion <NUM> or melt frost on a vehicle exterior side surface of the window portion <NUM>. Accordingly, when light is received or emitted by the sensor, light can be kept from being interrupted by fog or the like in the window portion <NUM>. As a result, measurement can be accurately performed using the sensor.

As described above, the following effects can be achieved according to the present embodiment.

Next, a second embodiment of a windshield according to the present invention will be described. The present embodiment differs from the first embodiment in that bus bars and heating wires are also arranged in a view field region other than the above-described window portion <NUM>, in the heat generation layer <NUM> of the intermediate film <NUM>. The view field region of the windshield is heated using these heating wires to melt frost or remove fog. In the following description, heating wires arranged in the window portion <NUM> will be referred to as first heating wires for the sake of convenience of description. Also, configurations for heating the window portion <NUM>, such as the first heating wires <NUM> and the first and second bus bars <NUM> and <NUM>, will be referred to as a first heat generation portion, and configurations such as the heating wires for generating heat in the view field region of the windshield other than the window portion <NUM> will be referred to as a second heat generation portion.

As shown in <FIG>, the heat generation layer <NUM> according to the present embodiment has a size that mostly covers the entire glass plates and further includes a third bus bar (first side bus bar) <NUM> that is arranged along the upper side <NUM> of the windshield, a fourth bus bar (second side bus bar) <NUM> that is arranged along the lower side <NUM> of the windshield, and a plurality of second heating wires <NUM> that extend in the up-down direction so as to connect the third bus bar <NUM> and the fourth bus bar <NUM> to each other, the third bus bar, the fourth bus bar, and the second heating wires being provided on the base material <NUM> of the heat generation layer <NUM>. The third bus bar <NUM> is formed so as to pass through the peripheral portion <NUM> and the center portion <NUM> of the mask layer <NUM> in the upper side <NUM> portion of the windshield. In particular, a portion of the third bus bar in the vicinity of its center in the left-right direction is formed so as to pass through the peripheral portion <NUM>, a side edge of the center portion <NUM>, and below the window portion <NUM>. On the other hand, the fourth bus bar is formed so as to pass through the peripheral portion <NUM> of the mask layer <NUM> in the lower side <NUM> portion of the windshield. Further, a third connection member <NUM> is attached to a left end portion of the third bus bar <NUM>, and a fourth connection member <NUM> is attached to a right end portion of the fourth bus bar <NUM>. These connection members <NUM> and <NUM> are configured similarly to the first connection member <NUM> and the second connection member <NUM> described above. Note that the base material <NUM> of the heat generation layer <NUM> can be made smaller than the adhesive layers <NUM> and <NUM>.

The plurality of second heating wires <NUM> are formed parallel to each other so as to extend in the up-down direction, but second heating wires <NUM> in the vicinity of the center in the left-right direction are made shorter than the other second heating wires <NUM> because the center portion <NUM> of the mask layer <NUM> protrudes downward. The second heating wires <NUM> can be formed into a straight line shape or a wave shape similarly to the first heating wires <NUM>. The crimp ratio and the like are also as described above.

Incidentally, snow, frost, and fog generated on the surface of the windshield are removed using the plurality of second heating wires <NUM>. On the other hand, as a result of heat being generated by the heating wires <NUM>, the adhesive layers <NUM> and <NUM> and the like located in the surrounding region of the heating wires <NUM> are heated, and this may cause flickering when the outside of the vehicle is viewed through the windshield. In particular, studies made by the inventor of the present invention revealed that the temperature of the heating wires <NUM> and the surrounding region of the heating wires <NUM> needs to be controlled to be not higher than <NUM> to prevent the occurrence of flickering when the outside of the vehicle is viewed through the windshield. To realize this, the heat generation amount of the heating wires <NUM> needs to be reduced to some extent. As described above, the heating wires <NUM> in the second heat generation portion are required to prevent flickering while having a heat generation amount that is large enough to melt frost or the like, and therefore in the present embodiment, the heat generation amount, dimensions such as the wire width and the pitch, and the like of the second heating wires <NUM> are set as described below based on the above-described Expressions (<NUM>) and (<NUM>).

The wire width of each heating wire <NUM> is preferably <NUM> to <NUM> pm, more preferably <NUM> to <NUM> pm, and particularly preferably <NUM> to <NUM>. Heating wires <NUM> having a smaller wire width are less likely to be seen, and therefore are suitable for use in the windshield according to the present embodiment. However, if the width of the heating wires <NUM> is reduced, the cross-sectional area is reduced, and accordingly, the heat generation amount may be increased as described above. Therefore, the lower limit of the wire width of the heating wires <NUM> can be set as described above. On the other hand, if the wire width of the heating wires <NUM> is increased, the heating wires <NUM> are likely to be seen and the heat generation amount is reduced as a result of the cross-sectional area being increased. Therefore, the upper limit of the wire width of the heating wires <NUM> is set as described above.

However, the wire width can also be set as described below, depending on the voltage applied between the bus bars <NUM> and <NUM>. If the voltage is smaller than <NUM> V, for example, the wire width of the heating wires <NUM> is preferably <NUM> to <NUM>. The heat generation amount can be increased by setting the wire width to be at least <NUM>. On the other hand, visibility can be reduced by setting the wire width to be not larger than <NUM>.

If the voltage applied between the bus bars <NUM> and <NUM> is <NUM> to <NUM> V, the wire width is preferably <NUM> to <NUM>. The heat generation amount can be increased by setting the wire width to be at least <NUM>. On the other hand, visibility can be reduced by setting the wire width to be not larger than <NUM>. Note that the wire width refers to the largest wire width of a cross-sectional shape of the heating wires <NUM>. If the cross-sectional shape of the heating wires <NUM> is a trapezoid, for example, the length of the lower side is the wire width, and if the cross-sectional shape of the heating wires <NUM> is a circle, the diameter is the wire width.

The thickness of the heating wires <NUM> is preferably not larger than <NUM> pm, more preferably not larger than <NUM> pm, and particularly preferably not larger than <NUM>. If the thickness is small as described above, steps between the heating wires <NUM> and the base material <NUM> can be made small to suppress the formation of bubbles in the vicinity of the steps during manufacture as described later. Also, the thickness of the heating wires <NUM> is preferably smaller than the wire width of the heating wires <NUM>. In other words, the aspect ratio of a cross section of each heating wire <NUM> is preferably not larger than <NUM>. If the thickness of the heating wires <NUM> is larger than the wire width, the heating wires <NUM> may fall over on the base material <NUM>, for example, giving rise to a difficulty in manufacture, or there is a risk of breaking of the heating wires.

Note that the wire width and the thickness of the heating wires <NUM> can be measured using a microscope such as VHX-<NUM> (manufactured by Keyence Corporation) at 1000x magnification, for example.

The pitch between adjacent heating wires <NUM> is preferably <NUM> to <NUM>, more preferably <NUM> to <NUM>, and even more preferably <NUM> to <NUM>. Note that the pitch is a length that is obtained by adding the wire width of a heating wire <NUM> to the length of a space between adjacent heating wires <NUM>, rather than the length of the space between adjacent heating wires <NUM>.

If the upper limit value of the pitch is set as described above, in a case in which a predetermined heat generation amount (e.g., <NUM> W/m<NUM>) is required for the entire windshield, for example, a reduction in the heat generation amount of the entire windshield can be prevented even if the heat generation amount W of each heating wire <NUM> is reduced as described above, because the number of heating wires <NUM> can be increased by reducing the pitch. On the other hand, with respect to the lower limit of the pitch, the followings are prescribed in Japan as of November <NUM>. That is, with respect to a device embedded in a test region A among devices for preventing fogging of window glass, Article <NUM>, paragraph <NUM>, item (v) (window glass) of notification prescribing details of the Safety Standards of the Road Transportation Vehicles prescribes that "the width of the device is not larger than <NUM> and the density is not higher than <NUM> pieces/cm (if conductors are horizontally embedded, <NUM> pieces/cm) ", and in order to satisfy the requirement of the density being not higher than <NUM> pieces/cm, the pitch is preferably at least <NUM>.

Note that in some cases, the heating wires <NUM> are formed into a sine wave shape. Also, there are cases in which positions or the pitch of rises and falls of the sine wave shape differ between adjacent heating wires <NUM>. In these cases, the pitch between the heating wires <NUM> can be determined by counting the number n of heating wires <NUM> in a predetermined region. For example, in a case in which the predetermined region is a rectangular region having a side with a length of <NUM>, if <NUM> heating wires <NUM> are arranged in the region, the pitch can be determined as follows : <NUM>/ (<NUM>-<NUM>) = <NUM>. The predetermined region is preferably within the range of the test region A defined in JIS R3212. This is because the test region A defined in JIS R3212 is a region for carrying out a test of perspective distortion or the like, and the necessity for preventing flickering, which is an effect of the present application, is high in this region.

The length of each heating wire <NUM> can be set to be at least <NUM>, for example. The length can also be set to be at least <NUM>, or at least <NUM>. The resistance of the heating wires <NUM> is preferably at least <NUM>Ω, and more preferably at least <NUM>Ω. If the length of the heating wires is increased as described above, the resistance R increases according to the above-described Expression (<NUM>), and accordingly, the heat generation amount is reduced and flickering can be suppressed.

Here, measurement of the resistance R of the heating wires <NUM> will be described. The resistance can be measured using a commercially available electrical resistance measurement device, and one example of which is Digital Multimeter <NUM> series (manufactured by Yokogawa Test & Measurement Corporation). In measurement, first, a heating wire to be measured is selected. Next, one terminal of the electrical resistance measurement device is connected to a portion of the heating wire in the vicinity of the bus bar <NUM>, and another terminal is connected to a portion of the heating wire in the vicinity of the bus bar <NUM>. Note that if the heating wire <NUM> is sandwiched between the outer glass plate <NUM> and the inner glass plate <NUM> and the terminals of the electrical resistance measurement device cannot be connected to the heating wire, the outer glass plate <NUM> or the inner glass plate <NUM> can be broken to measure the resistance R of the heating wire <NUM>. Also, if the heating wire to be measured is connected to an adjacent heating wire via a bridge (not shown), for example, the resistance R of the heating wire to be measured is measured after the bridge is cut.

When a voltage of <NUM> V is applied between the bus bars <NUM> and <NUM>, for example, the heat generation amount per unit length of each heating wire <NUM> is preferably not larger than <NUM> W/m, more preferably not larger than <NUM> W/m, and particularly preferably not larger than <NUM> W/m. If the heat generation amount is not larger than <NUM> W/m, flickering can be suppressed. More specifically, the heat generation amount can be set to a range from <NUM> W/m to <NUM> W/m inclusive, from <NUM> W/m to <NUM> W/m inclusive, from <NUM> W/m to <NUM> W/m inclusive, from <NUM> W/m to <NUM> W/m inclusive, from <NUM> W/m to <NUM> W/m inclusive, or from <NUM> W/m to <NUM> W/m inclusive, for example. In order to effectively prevent fogging or melt frost or the like using such heating wires <NUM>, the heat generation amount per unit area of the windshield is preferably <NUM> to <NUM> W/m<NUM>, more preferably at least <NUM> W/m<NUM>, and particularly preferably at least <NUM> W/m<NUM>.

As described above, in general, the wire width and the pitch of the heating wires <NUM> in the second heat generation portion are made larger than the wire width and the pitch of the heating wires <NUM> of the first heat generation portion. This is because an area to be heated by the second heat generation portion is large and therefore power consumption is taken into consideration.

The above-described arrangement of the first to fourth bus bars and the first and second heating wires is one example and can be appropriately changed. In the following description, the example shown in <FIG> will be referred to as a first aspect, and examples of other aspects will be described with reference to <FIG>.

This aspect differs from the first aspect in the configuration of the first heat generation portion, and the configuration of the second heat generation portion is the same. As shown in <FIG>, a fifth bus bar <NUM> and a sixth bus bar <NUM> are arranged on a straight line on the upper side of the window portion <NUM>, and a relay bus bar <NUM> is arranged on the lower side of the window portion <NUM>. The first connection member <NUM> connected to a positive electrode is attached to the fifth bus bar <NUM>, and the second connection member <NUM> connected to a negative electrode is connected to the sixth bus bar <NUM>. The fifth bus bar <NUM> and the sixth bus bar <NUM> are adjacent to each other with a space therebetween, and the relay bus bar <NUM> is made longer than the fifth bus bar <NUM> and the sixth bus bar <NUM>. The plurality of first heating wires <NUM> connect the fifth bus bar <NUM> to a right side region of the relay bus bar <NUM> and connect the sixth bus bar <NUM> to a left side region of the relay bus bar <NUM>. Accordingly, when a voltage is applied between the first connection member <NUM> and the second connection member <NUM>, a current flows through the fifth bus bar <NUM>, the relay bus bar <NUM>, and the sixth bus bar <NUM> in that order, and the first heating wires <NUM> generate heat. As described above, in the second aspect, the first heat generation portion and the second heat generation portion are constituted by different circuits and heat generation can be separately controlled.

As shown in <FIG>, a third aspect differs from the second aspect in the configuration of the second heat generation portion. That is, third connection members <NUM> are respectively attached to both end portions of the third bus bar <NUM>. Further, the second connection member <NUM> is attached to a center portion of the fourth bus bar <NUM>. As described above, in the third aspect, the first heat generation portion and the second heat generation portion are constituted by different circuits and heat generation can be separately controlled.

As shown in <FIG>, in this aspect, a seventh bus bar <NUM> is formed at the upper side <NUM> of the windshield so as to extend from a left end portion to the upper side of the window portion <NUM>. Also, an eighth bus bar <NUM> that extends along the lower side of the window portion <NUM> is formed. Further, a ninth bus bar <NUM> is formed so as to extend rightward along the lower side of the window portion <NUM> while passing below the eighth bus bar <NUM> and further extend along the upper side <NUM> of the windshield while passing the peripheral portion <NUM> of the mask layer <NUM>. Also, the fourth bus bar <NUM> is formed so as to extend along the lower side <NUM> of the windshield similarly to the third aspect.

On the other hand, the plurality of first heating wires <NUM> extend between the seventh bus bar <NUM> and the eighth bus bar <NUM> while passing through the window portion <NUM> in the up-down direction. Some of the plurality of second heating wires <NUM> are arranged so as to extend in the up-down direction between a region of the seventh bus bar <NUM> on the left side of the first heating wires <NUM> and a left side region of the fourth bus bar <NUM>. Further, on the right side of these second heating wires, a plurality of second heating wires <NUM> are arranged parallel to each other so as to extend in the up-down direction between the ninth bus bar <NUM> and the fourth bus bar <NUM>.

The first connection member <NUM> extending upward is attached to the seventh bus bar <NUM> and connected to a positive electrode. Also, the second connection member <NUM> extending upward is attached to the eighth bus bar <NUM> and connected to a negative electrode. Further, the third connection member <NUM> extending upward is attached to the ninth bus bar <NUM> and connected to a negative electrode. As described above, in the fourth aspect, the positive electrode is common to the first heat generation portion and the second heat generation portion, and the negative electrodes are separately provided.

As shown in <FIG>, in a fifth aspect, a tenth bus bar <NUM> is formed along the upper side of the window portion <NUM>. The plurality of first heating wires <NUM> are arranged so as to extend in the up-down direction between the tenth bus bar <NUM> and the third bus bar <NUM>. The first connection member <NUM> extending upward is attached to the tenth bus bar <NUM> and connected to a negative electrode. The configuration of the second heat generation portion is the same as that in the first aspect. As described above, in the fifth aspect, the positive electrode is common to the first heat generation portion and the second heat generation portion, and the negative electrodes are separately provided.

As shown in <FIG>, a sixth aspect differs from the first aspect in the configuration of the third bus bar <NUM>. That is, an extension portion that extends to the vicinity of a left end portion of the lower side <NUM> of the windshield via the left side <NUM> of the windshield is joined to a left end portion of the third bus bar <NUM>. The thus formed bus bar will be referred to as an eleventh bus bar <NUM>. The fourth bus bar is made slightly shorter so as not to be in contact with the eleventh bus bar <NUM>. Also, the third connection member <NUM> that extends downward at the lower side <NUM> of the windshield is attached to the eleventh bus bar <NUM> and connected to a positive electrode. Accordingly, both connection members of the second heat generation portion are connected to power supply terminals at the lower side of the windshield. As described above, in the sixth aspect, the first heat generation portion and the second heat generation portion are constituted by different circuits and heat generation can be separately controlled.

As shown in <FIG>, in a seventh aspect, the third bus bar <NUM> in the fifth aspect is replaced with the eleventh bus bar <NUM>. As described above, in the seventh aspect, the positive electrode is common to the first heat generation portion and the second heat generation portion, and the negative electrodes are separately provided.

As shown in <FIG>, in an eighth aspect, the third bus bar <NUM> in the second aspect is replaced with the eleventh bus bar <NUM>. As described above, in the eighth aspect, the first heat generation portion and the second heat generation portion are constituted by different circuits and heat generation can be separately controlled.

As shown in <FIG>, a ninth aspect includes a twelfth bus bar <NUM> and a 13th bus bar <NUM> that are formed by dividing the fourth bus bar <NUM> in the first aspect into two sections in the left-right direction. A third connection member <NUM> is attached to the twelfth bus bar <NUM> and connected to a positive electrode. On the other hand, a fourth connection member <NUM> is connected to the 13th bus bar <NUM> and a negative electrode. With this configuration, in the second heat generation portion, a current flows from the twelfth bus bar <NUM> via the third bus bar <NUM> to the 13th bus bar <NUM>. As described above, in the eighth aspect, the first heat generation portion and the second heat generation portion are constituted by different circuits and heat generation can be separately controlled.

As shown in <FIG>, a tenth aspect differs from the first aspect in the configuration of the fourth bus bar <NUM>. That is, an extension portion that extends to the vicinity of a right end portion of the upper side <NUM> of the windshield via the right side <NUM> of the windshield is joined to a right end portion of the fourth bus bar <NUM>. A portion of this extension portion that is located at the upper side <NUM> is arranged on the upper side of the third bus bar <NUM>. The thus formed bus bar will be referred to as a 14th bus bar <NUM>. The fourth connection member <NUM> that extends upward at the upper side <NUM> of the windshield is attached to the 14th bus bar <NUM> and connected to a negative electrode. Accordingly, both connection members <NUM> and <NUM> of the second heat generation portion are connected to power supply terminals at the upper side <NUM> of the windshield. As described above, in the tenth aspect, the first heat generation portion and the second heat generation portion are constituted by different circuits and heat generation can be separately controlled.

As shown in <FIG>, in an eleventh aspect, the fourth bus bar <NUM> in the fifth aspect is replaced with the 14th bus bar <NUM>. Accordingly, both connection members <NUM> and <NUM> of the second heat generation portion are connected to power supply terminals at the upper side <NUM> of the windshield. As described above, in the eleventh aspect, the positive electrode is common to the first heat generation portion and the second heat generation portion, and the negative electrodes are separately provided.

As shown in <FIG>, in a twelfth aspect, the fourth bus bar <NUM> in the second aspect is replaced with the 14th bus bar <NUM>. Accordingly, both connection members <NUM> and <NUM> of the second heat generation portion are connected to power supply terminals at the upper side <NUM> of the windshield. As described above, in the twelfth aspect, the first heat generation portion and the second heat generation portion are constituted by different circuits and heat generation can be separately controlled.

As shown in <FIG>, in an eleventh aspect, the fourth bus bar <NUM> in the fifth aspect is replaced with the twelfth bus bar <NUM> and the 13th bus bar <NUM> described in the ninth aspect. Accordingly, both connection members <NUM> and <NUM> of the second heat generation portion are connected to power supply terminals at the lower side <NUM> of the windshield. As described above, in the 13th aspect, the first heat generation portion and the second heat generation portion are constituted by different circuits and heat generation can be controlled.

As shown in <FIG>, in a 14th aspect, the fourth bus bar <NUM> in the second aspect is replaced with the twelfth bus bar <NUM> and the 13th bus bar <NUM> described in the ninth aspect. As described above, in the 14th aspect, the first heat generation portion and the second heat generation portion are constituted by different circuits and heat generation can be separately controlled.

As shown in <FIG>, in a 15th aspect, a 15th bus bar <NUM> that extends along almost the entire length of the upper side <NUM> of the windshield is provided. The 15th bus bar <NUM> is arranged on the upper side of the window portion <NUM>. The plurality of first heating wires <NUM> are arranged between the 15th bus bar <NUM> and the second bus bar <NUM> so as to pass through the window portion <NUM>. Also, a plurality of second heating wires <NUM> are arranged between the 15th bus bar <NUM> and the fourth bus bar <NUM> in regions where the first heating wires <NUM> are not arranged, i.e., on both sides of the window portion <NUM>. Also, a plurality of second heating wires <NUM> are arranged between the second bus bar <NUM> and the fourth bus bar <NUM>. The first connection member <NUM> is attached to the 15th bus bar <NUM> and extends upward. The first connection member <NUM> is connected to a positive electrode. As described above, in the 13th aspect, the first heat generation portion and the second heat generation portion are constituted by a common circuit.

As shown in <FIG>, a 16th aspect differs from the first aspect in the configuration of the first heat generation portion. That is, a 16th bus bar <NUM> is arranged on the left side of the window portion <NUM>, and a 17th bus bar <NUM> is arranged on the right side of the window portion <NUM>. Both of the 16th bus bar <NUM> and the 17th bus bar <NUM> extend in the up-down direction. A plurality of first heating wires <NUM> that extend in the horizontal direction between the 16th bus bar <NUM> and the 17th bus bar <NUM> are arranged parallel to each other. The configuration of the second heat generation portion is the same as that in the first aspect. As described above, in the 16th aspect, the first heat generation portion and the second heat generation portion are constituted by different circuits and heat generation can be separately controlled.

As shown in <FIG>, a 17th aspect differs from the first aspect in the configuration of the first heat generation portion. That is, an 18th bus bar <NUM> that extends in the up-down direction is arranged on the left side of the window portion <NUM>. A plurality of first heating wires <NUM> extend parallel to each other in the horizontal direction from the 18th bus bar <NUM>, pass the window portion <NUM>, and are connected to the third bus bar <NUM>. The first connection member <NUM> is attached to the 18th bus bar <NUM> and extends upward. The first connection member <NUM> is connected to a negative electrode. As described above, in the 17th aspect, the positive electrode is common to the first heat generation portion and the second heat generation portion and the negative electrodes are separately provided.

As shown in <FIG>, an 18th aspect differs from the first aspect in the configuration of the first heat generation portion. That is, a 19th bus bar <NUM> that extends in the up-down direction is arranged on the left side of the window portion <NUM>, and a 20th bus bar <NUM> and a 21st bus bar <NUM> that extend in the up-down direction are arranged on the right side of the window portion <NUM>. The 20th bus bar <NUM> is arranged on the upper side of the 21st bus bar <NUM> with a space therebetween. An upper portion of the 19th bus bar <NUM> and the 20th bus bar <NUM> are connected to a plurality of first heating wires <NUM> extending in the horizontal direction, and a lower portion of the 19th bus bar <NUM> and the 21st bus bar <NUM> are connected to a plurality of first heating wires <NUM> extending in the horizontal direction. The first connection member <NUM> extending upward is attached to the 20th bus bar <NUM> and connected to a positive electrode. On the other hand, the second connection member <NUM> extending upward is attached to the 21st bus bar <NUM> and connected to a negative electrode. Accordingly, a current flows from the 20th bus bar <NUM> via the 19th bus bar <NUM> to the 21st bus bar <NUM>. As described above, in the 18th aspect, the first heat generation portion and the second heat generation portion are constituted by different circuits and heat generation can be separately controlled.

As shown in <FIG>, a 19th aspect differs from the 17th aspect in the configuration of the second heat generation portion. That is, the third bus bar <NUM> in the 17th aspect is divided into a 22nd bus bar <NUM> and a 23rd bus bar <NUM> in the left-right direction. The 18th bus bar <NUM> is connected to the 23rd bus bar <NUM> via a plurality of first heating wires <NUM> extending in the horizontal direction. The third connection member <NUM> is attached to the 22nd bus bar <NUM> and connected to a positive electrode. On the other hand, the fourth connection member <NUM> is attached to the 23rd bus bar <NUM> and connected to a negative electrode. A plurality of second heating wires <NUM> connect the 22nd bus bar <NUM> to a left side region of the fourth bus bar <NUM> and connect the 23rd bus bar <NUM> to a right side region of the fourth bus bar <NUM>. Accordingly, in the second heat generation portion, a current flows from the 22nd bus bar <NUM> via the fourth bus bar <NUM> to the 23rd bus bar <NUM>.

In the above-described first to 19th aspects, the first heat generation portion and the second heat generation portion are provided in a single heat generation layer, but in a 20th aspect, the first heat generation portion and the second heat generation portion are provided in separate heat generation layers. <FIG> is a plan view of the 20th aspect and <FIG> is a cross-sectional view taken along line B-B in <FIG>. <FIG> is a plan view showing a first heat generation layer in which the first heat generation portion is provided, and <FIG> is a plan view showing a second heat generation layer in which the second heat generation portion is provided.

As shown in <FIG>, the intermediate film <NUM> includes a first base material <NUM> that constitutes the first heat generation portion and a second base material <NUM> that constitutes the second heat generation portion. The first and second base materials are constituted by the same material as the above-described base material <NUM> and are slightly smaller than the glass plates <NUM> and <NUM>. However, the first and second base materials may also have the same size as the glass plates <NUM> and <NUM>. As shown in <FIG>, the first bus bar <NUM>, the second bus bar <NUM>, the first heating wires <NUM>, the first connection member <NUM>, and the second connection member <NUM> are arranged on the first base material <NUM>. Configurations of these members are the same as those in the first embodiment. On the other hand, as shown in <FIG>, the third bus bar <NUM>, the second bus bar <NUM>, the second heating wires <NUM>, the third connection member <NUM>, and the fourth connection portion <NUM> are arranged on the second base material <NUM>. Out of these members, the third bus bar <NUM> is formed into a straight line shape and extends along the upper side <NUM> of the glass plates <NUM> and <NUM> on the upper side of the window portion <NUM>, but configurations of the other members are the same as those in the first aspect.

As shown in <FIG>, the first heat generation portion and the second heat generation portion shown in <FIG> are overlaid on each other and sandwiched between the adhesive layers <NUM> and <NUM>. When viewed from the front, the first bus bar <NUM> overlaps the third bus bar <NUM>. As described above, in the 20th aspect, the first heat generation portion and the second heat generation portion are constituted by different circuits and heat generation can be separately controlled.

As described above, according to the present embodiment, the view field region of the windshield can be heated in addition to the window portion <NUM>. Therefore, it is possible to melt frost and remove fog over the entire windshield. In particular, specifications of the heating wires <NUM> are determined as described above, and therefore a sufficient amount of heat can be generated in the view field region to melt frost or the like.

Claim 1:
A windshield for an automobile to which an information acquisition device (<NUM>) for acquiring information from the outside of a vehicle by emitting and/or receiving light can be installed, the windshield comprising:
an outer glass plate (<NUM>) that includes a first side and a second side that is opposite to the first side;
an inner glass plate (<NUM>) that is arranged opposite to the outer glass plate (<NUM>) and has substantially the same shape as the outer glass plate (<NUM>); and
an intermediate film (<NUM>) that is arranged between the outer glass plate (<NUM>) and the inner glass plate (<NUM>),
wherein the windshield includes an information acquisition region (<NUM>) that is to be located opposite to the information acquisition device (<NUM>) and through which the light passes,
the intermediate film (<NUM>) includes:
at least one adhesive layer (<NUM>, <NUM>); and
a heat generation layer (<NUM>) that is supported by the adhesive layer (<NUM>, <NUM>),
the heat generation layer (<NUM>) includes, at least in a region that corresponds to the information acquisition region (<NUM>):
a pair of bus bars (<NUM>, <NUM>) that are arranged such that the information acquisition region is (<NUM>) interposed therebetween; and
a plurality of first heating wires (<NUM>) that are connected in parallel so as to connect the bus bars (<NUM>, <NUM>) to each other,
each of the first heating wires (<NUM>) has a wire width not larger than <NUM> pm,
the cross-sectional shape of the first heating wires (<NUM>) is a trapezoid, and
at least in a portion of each of the first heating wires (<NUM>), the wire width of the first heating wire (<NUM>) is equal to or larger than a thickness of the first heating wire.