AUTOMOTIVE LAMINATE WITH INVISIBLE HEATING AND HIGH RED RATIO FOR CAMERA DEFROSTER

Abstract

The use of camera-based safety systems is growing at a rapid rate in automobiles where they provide lane departure warning, collision avoidance, adaptive cruise control and other functions. For proper operation, the cameras require a clear undistorted field of view. Keeping the camera area free of snow and ice has been a problem. The lines widths of printed silver frit defroster circuits can interfere with the camera function. Transparent conductive solar control coatings and films can be used but they often result is a poor red ratio. Thin embedded wire defrosters are invisible for all practical purposes but are expensive and difficult to connect electrically. The invention provides an invisible defroster circuit that can be inexpensively produced by applying the circuit to the inside surface of glass rather than imbedding within the laminate.

Claims

1. A laminated glazing with a camera field of view comprising: at least two glass layers, an exterior and an interior glass layers; at least one plastic bonding layer serving to bond opposite major faces of adjacent layers in the laminate, said at least one bonding layer being located between the exterior and the interior glass layers; a resistive heating circuit configured to heat at least a portion of the camera field of view; at least one adhesive layer; and a transparent glass cover bonded to the interior glass layer by means of said at least one adhesive layer; wherein the resistive heating circuit is located between the transparent glass cover and the interior glass layer.

2. The laminate of claim 1 wherein the resistive heating circuit is comprised of a micro-mesh deposited on the transparent glass cover.

3. The laminate of claim 1 wherein the resistive heating circuit is comprised of a transparent conductive coating deposited on the transparent cover.

4. The laminate of claim 1 wherein the transparent glass cover is chemically tempered.

5. The laminate of claim 1 wherein the transparent glass cover is cold bent.

6. The laminate of claim 1 wherein the transparent glass cover has a thickness of less than or equal to 1 mm thick, preferably less than or equal to 0.7 mm, more preferably less than or equal to 0.4 mm.

7. The laminate of claim 1 further comprising a plastic film, wherein the resistive heating circuit is comprised of a micro-mesh deposited on said plastic film, and wherein the plastic film is placed between the interior glass layer and the transparent glass cover.

8. The laminate of claim 1 further comprising a plastic film, wherein the resistive heating circuit is comprised of a transparent conductive coating deposited on said plastic film, and wherein the plastic film is placed between the interior glass layer and the transparent glass cover.

9. A laminated glazing with a camera field of view comprising: at least two glass layers, an exterior and an interior glass layers, wherein the interior glass layer has a cutout in the camera field of view; at least one plastic bonding layer serving to bond opposite major faces of adjacent layers in the laminate, said at least one bonding layer being located between the exterior and the interior glass layers; a resistive heating circuit configured to heat at least a portion of the camera field of view; and a transparent glass cover that fits within said cutout; wherein the resistive heating circuit is located between the transparent glass cover and the exterior glass layer.

10. The laminate of claim 9 wherein the transparent glass cover is bonded to the exterior glass layer by means of said at least one plastic bonding layer.

11. The laminate of claim 9 further comprising at least one adhesive layer.

12. The laminate of claim 11 wherein said at least one plastic layer has a cut out in the camera field of view; and wherein the transparent glass cover is bonded to the exterior glass layer by means of said at least one adhesive layer.

13. The laminate of claim 9 wherein the resistive heating circuit is comprised of a micro-mesh deposited on the transparent glass cover.

14. The laminate of claim 9 wherein the resistive heating circuit is comprised of a transparent conductive coating deposited on the transparent cover.

15. The laminate of claim 9 wherein the transparent glass cover is chemically tempered.

16. The laminate of claim 9 wherein the transparent glass cover is cold bent.

17. The laminate of claim 9 wherein the transparent glass cover has a thickness of less than or equal to 1 mm thick, preferably less than or equal to 0.7 mm, more preferably less than or equal to 0.4 mm.

18. The laminate of claim 9 further comprising a plastic film, wherein the resistive heating circuit is comprised of a micro-mesh deposited on said plastic film, and wherein the plastic film is placed between the exterior glass layer and the transparent glass cover.

19. The laminate of claim 9 further comprising a plastic film, wherein the resistive heating circuit is comprised of a transparent conductive coating deposited on said plastic film, and wherein the plastic film is placed between the exterior glass layer and the transparent glass cover.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0034] These features and advantages of the present invention will become apparent from the detailed description of the following embodiments in conjunction with the accompanying drawings, wherein:

[0035] FIG. 1A shows a cross section of a typical automotive laminate.

[0036] FIG. 1B shows a cross section of a typical automotive laminate with coating and performance film.

[0037] FIG. 2 shows an exploded view of a micro-mesh on glass defroster.

[0038] FIG. 3 shows an exploded view of a transparent conductive coating defroster.

[0039] FIG. 4 shows an exploded view of an embedded wire defroster.

[0040] FIG. 5 shows an exploded view of a micromesh on film defroster.

[0041] FIG. 6 shows an exploded view of a transparent conductive film defroster.

[0042] FIG. 7 shows an exploded view of a non-uniform area with uniform micro mesh defroster.

[0043] FIG. 8 shows an exploded view of a windshield with laminated defroster on surface four.

REFERENCE NUMERALS

[0044] 4 Plastic bonding layer [0045] 6 Obscuration [0046] 8 Coating [0047] 12 Film [0048] 14 Busbar [0049] 16 Lead [0050] 18 Conductive coating [0051] 22 Embedded wire circuit [0052] 24 Micro mesh circuit [0053] 26 Adhesive layer [0054] 28 Cover [0055] 30 Plastic Film [0056] 32 Camera field of view [0057] 101 Surface one [0058] 102 Surface two [0059] 103 Surface three [0060] 104 Surface four [0061] 201 Exterior glass layer [0062] 202 Inner glass layer

DETAILED DESCRIPTION OF THE INVENTION

[0063] The following terminology is used to describe the laminated glazing of the invention. A typical automotive laminate cross section is illustrated in FIGS. 1A and 1B. The laminate is comprised of two layers of glass the exterior or outer 201 and interior or inner 202 that are permanently bonded together by a plastic bonding layer 4 (interlayer). The glass surface that is on the exterior of the vehicle is referred to as surface one 101 or the number one surface. The opposite face of the exterior glass layer 201 is surface two 102 or the number two surface. The glass surface that is on the interior of the vehicle is referred to as surface four 104 or the number four surface. The opposite face of the interior layer of glass 202 is surface three 103 or the number three surface. Surfaces two 102 and three 103 are bonded together by the plastic bonding layer 4. An obscuration 6 may be also applied to the glass. Obscuration are commonly comprised of black enamel frit printed on either the surface two 102 or number four surface 104 or on both. The laminate may also comprise a coating 8 on one or more of the surfaces. The laminate may also comprise a film 12 laminated between at least two plastic bonding layers 4.

[0064] Laminated safety glass is made by bonding two sheets of annealed glass together using a plastic bonding layer comprised of a thin sheet of transparent thermo plastic as shown in FIG. 1. Annealed glass is glass that has been slowly cooled from the bending temperature down through the glass transition range. This process relieves any stress left in the glass from the bending process. Annealed glass breaks into large shards with sharp edges. When laminated glass breaks, the shards of broken glass are held together, much like the pieces of a jigsaw puzzle, by the plastic bonding layer helping to maintain the structural integrity of the glass. A vehicle with a broken windshield can still be operated. The plastic bonding layer also helps to prevent penetration by objects striking the laminate from the exterior and in the event of a crash occupant retention is improved.

[0065] The glass layers are formed using gravity bending, press bending, cold bending or any other conventional means known in the art. Gravity and press bending methods for forming glass are well known in the art and will not be discussed in the present disclosure.

[0066] Cold bending is a relatively new technology. As the name suggest, the glass is bent, while cold to its final shape, without the use of heat. On parts with minimal curvature a flat sheet of glass can be bent cold to the contour of the part. This is possible because as the thickness of glass decreases, the sheets become increasingly more flexible and can be bent without inducing stress levels high enough to significantly increase the long-term probability of breakage. Thin sheets of annealed soda-lime glass, in thicknesses of about 1 mm, can be bent to large radii cylindrical shapes (greater than 6 m). When the glass is chemically, or heat strengthened the glass can endure much higher levels of stress and can be bent along both major axis. The process is primarily used to bend chemically tempered thin glass sheets (1 mm) to shape.

[0067] Cylindrical shapes can be formed with a radius in one direction of less than 4 meters. Shapes with compound bend, that is curvature in the direction of both principle axis can be formed with a radius of curvature in each direction of as small as approximately 8 meters. Of course, much depends upon the surface area of the parts and the types and thicknesses of the substrates.

[0068] The cold bent glass will remain in tension and tend to distort the shape of the bent layer that it is bonded to. Therefore, the bent layer must be compensated to offset the tension. For more complex shapes with a high level of curvature, the flat glass may need to be partially thermally bent prior to cold bending.

[0069] The glass to be cold bent is placed with a bent to shape layer and with a plastic bonding layer placed between the glass to be cold bent and the bent glass layer. The assembly is placed in what is known as a vacuum bag. The vacuum bag is an airtight set of plastic sheets, enclosing the assembly and bonded together it the edges, which allows for the air to be evacuated from the assembly and which also applies pressure on the assembly forcing the layers into contact. The assembly, in the evacuated vacuum bag, is then heated to seal the assembly. The assembly is next placed into an autoclave which heats the assembly and applies high pressure. This completes the cold bending process as the flat glass at this point has conformed to the shape of the bent layer and is permanently affixed. The cold bending process is very similar to a standard vacuum bag/autoclave process, well known in the art, except for having an unbent glass layer added to the stack of glass.

[0070] The plastic bonding layer (interlayer) has the primary function of bonding the major faces of adjacent layers to each other. The material selected is typically a clear plastic when bonding one glass layer to another glass layer. For automotive use, the most commonly used interlayer is polyvinyl butyl (PVB). In addition to polyvinyl butyl, ionoplast polymers, ethylene vinyl acetate (EVA), cast in place (CIP) liquid resin and thermoplastic polyurethane (TPU) can also be used. Interlayers are available with enhanced capabilities beyond bonding the glass layers together. The invention may include interlayers designed to dampen sound. Such interlayers are comprised whole or in part of a layer of plastic that is softer and more flexible than that normally used. The interlayer may also be of a type which has solar attenuating properties.

[0071] Automotive interlayers are made by an extrusion process. A smooth surface tends to stick to the glass, making it difficult to position on the glass and to trap air. To facilitate the handling of the plastic sheet and the removal or air (deairing) from the laminate, the surface of the plastic is normally embossed. Standard thicknesses for automotive PVB interlayer at 0.38 mm and 0.76 mm (15 and 30 mil).

[0072] Rather than producing a defroster by means of a screen print silver on the number four surface or laminating an embedded wire, conductive coating or micro mesh circuit within the laminate, the defroster circuit is manufactured separate of the laminate and then bonded to the number four surface. The defroster circuit can be applied prior to lamination, depending upon the material used to bond the circuit or at any point afterwards. The defroster circuit may be bonded using an ordinary automotive interlayer, an optical adhesive, laminating resin or other suitable means. As shown in FIGS. 2, 3, 4, 5 and 6, the defroster circuit of the invention is comprised of at least one adhesive layer 26, at least one resistive circuit including busbars 14 and leads 16 and at least one cover 28. The cover 28 may be comprised of plastic, glass or any other suitable transparent material. The resistive circuit may be comprised of a micro mesh circuit 24, embedded wire circuit 22, printed silver, conductive coating 18 or conductive coated film (conductive coating 18 on a plastic film 30). Busbars are comprised of a conductive ink or thin flat copper conductors. The leads for the power connection are soldered to busbar. The resistive circuit is protected by the cover. The circuit is always between the major face of the cover (on the windshield side of the cover) and the windshield. The micro mesh or conductive coating may be deposited on a film, in which case two adhesive layers are required or directly on the cover. The cover may be comprised of thin glass. The cover may be comprised of a chemically tempered glass. The cover may be bent to the curvature of the windshield. The cover may be partially bent or applied flat and flat bent.

[0073] In addition to the conventional automotive interlayers, optically clear adhesives (OCA) might also be applied as adhesive elements for fixing the heating element in the windshield. These adhesives are formed by partially curing optically clear resins (OCR) at 70 C. and forming pliable films that also have some level of adherence. These films may be comprised of acrylics, epoxy resins, silicones, and urethanes disposed in such way that they are compatible with the surfaces to be bonded. Then, by assembling the elements into the laminated windshield, vacuum is applied in order to assure an effective bonding process. After, curing means, such as UV, thermal, electrons, and moisture is applied for forming the final laminated windshield with heating element Laminating resins also consist of these same adhesive materials but in a liquid state. Their application consists of the same steps as that of optically clear adhesives. Both solutions may also be applied depending on how compatible the surfaces to be bonded are with these adhesives.

DETAILED DESCRIPTION OF THE EMBODIMENTS

[0074] 1. A windshield, similar to the one illustrated in FIG. 8, has an opening for the camera field of view 32, in the black obscuration 6, that has a trapezoidal shape of approximately 90 mm at the top by 180 mm along the bottom and a height of 110 mm for a heated area of 1.5 dm2. The defroster circuit is designed to have a power density of at least 15 watts/dm2. With a heated area of 1.5 dm2 the minimum power must be 22.5 watts. The supply voltage is 13 volts. [0075] The laminate has a standard soda-lime 2.5 mm thick clear exterior glass layer 201 and 2.1-mm soda-lime solar green interior glass layer 202. Obscuration 6 is screen printed on surface two and surface four. The obscuration 6 frames the camera field of view 32 area and hides the camera assembly. The glass layers are thermally bent using a gravity bending process. [0076] In this embodiment, the defroster circuit comprises a micro-mesh circuit 24, as show in FIG. 7, comprising 10 m lines designed to meet the electrical requirements. The thickness of the lines is controlled so as to meet the power requirements. The trapezoidal design results in the lines at the top having a lower resistance and drawing more power that the ones located at the bottom. To compensate the spacing between the lines is varied in a manner that is directly proportional to their power. This results in uniform power density from top to bottom. The mesh is also provided with vertical lines. During normal operation, little if no current will flow in the vertical lines as the voltage will be balanced. If a line should fail, the vertical lines provide a measure of fault tolerance as the power will have an alternate route around the break. The vertical lines will also help to balance the power in the circuit if there is any variation in line width or thickness, due to manufacturing variation and tolerance. [0077] During assembly of the laminate, as shown in FIG. 5, a layer of 0.36 mm PVB (adhesive layer) 26 is placed on the number four surface of the laminate followed by the micro-mesh circuit 24 deposited on 50 m PET plastic film 30, another 0.36 layer of PVB (adhesive layer) 26 and then an 0.4 mm chemically tempered aluminosilicate flat glass cover 28. The flat glass cover 28 is cold bent in the autoclave. The assembled laminated is processed, using standard automotive laminating equipment. [0078] 2. The windshield, similar to the one illustrated in FIG. 8, has a rectangular opening for the camera field of view 32, in the black obscuration 6, that top by 200 mm wide and a height of 100 mm for a heated area of 2 dm2 The defroster circuit is designed to have a power density of at least 15 watts/dm2. With a heated area of 1.5 dm2 the minimum power must be 30 watts. The supply voltage is 13 volts. [0079] The laminate has a standard soda-lime 2.5 mm thick clear exterior glass layer 201 and 2.1-mm soda-lime solar green interior glass layer 202. Obscuration 6 is screen printed on surface two and surface four. The obscuration 6 frames the camera field of view 32 area and hides the camera assembly. The glass layers are thermally bent using a gravity bending process. [0080] In this embodiment, the defroster circuit comprises a micro-mesh circuit 24, as show in FIG. 2 comprising 10 m lines, designed to meet the electrical requirements. The thickness of the lines is controlled so as to meet the power requirements. The rectangular design allows for uniform line spacing. This results in uniform power density from top to bottom. [0081] During assembly of the laminate, as shown to FIG. 2, a layer of 0.36 mm PVB (adhesive layer) 26 is placed on the number four surface of the laminate followed by the micro-mesh circuit 24, deposited on an 0.4 mm chemically tempered aluminosilicate flat glass cover 28. The flat glass cover 28 is cold bent in the autoclave. The assembled laminated is processed, using standard automotive laminating equipment. [0082] 3. The windshield, similar to the one illustrated in FIG. 8, has a rectangular opening for the camera field of view 32, in the black obscuration 6, that top by 200 mm wide and a height of 100 mm for a heated area of 2 dm2 The defroster circuit is designed to have a power density of at least 15 watts/dm2. With a heated area of 1.5 dm2 the minimum power must be 30 watts. The supply voltage is 13 volts. [0083] The laminate has a standard soda-lime 2.5 mm thick clear exterior glass layer 201 and 2.1-mm soda-lime solar green interior glass layer 202. Obscuration 6 is screen printed on surface two and surface four. The obscuration 6 frames the camera field of view 32 area and hides the camera assembly. The glass layers are thermally bent using a gravity bending process. [0084] In this embodiment, the defroster circuit comprises a transparent conductive coated film, as show in FIG. 6, designed to meet the electrical requirements. The coating stack selected does not attenuate red. [0085] During assembly of the laminate, as shown in FIG. 6, a layer of 0.36 mm PVB (adhesive layer) 26 is placed on the number four surface of the laminate followed by the transparent conductive coating 18, deposited on 50 m PET plastic film 30, another 0.36 layer of PVB (adhesive layer) 26 and then an 0.4 mm chemically tempered aluminosilicate flat glass cover 28. The flat glass cover 28 is cold bent in the autoclave. The assembled laminated is processed, using standard automotive laminating equipment. [0086] 4. The windshield, similar to the one illustrated in FIG. 8, has a rectangular opening for the camera field of view 32, in the black obscuration 6, that top by 200 mm wide and a height of 100 mm for a heated area of 2 dm2 The defroster circuit is designed to have a power density of at least 15 watts/dm2. With a heated area of 1.5 dm2 the minimum power must be 30 watts. The supply voltage is 13 volts. [0087] The laminate has a standard soda-lime 2.5 mm thick clear exterior glass layer 201 and 2.1 mm soda-lime solar green interior glass layer 202. Obscuration 6 is screen printed on surface two 102 and surface four of the laminate. The obscuration 6 frames the camera field of view 32 area and hides the camera assembly. The glass layers are thermally bent using a gravity bending process. [0088] In this embodiment, the defroster circuit comprises a transparent conductive coating 18 deposited on the cover 28, as shown in FIG. 3. The coating stack selected does not attenuate red. [0089] During assembly of the laminate a layer of 0.36 mm PVB (adhesive layer) 26 is placed on the number four surface of the laminate followed by the transparent conductive coated 0.4 mm chemically tempered aluminosilicate flat glass cover 28. The flat glass cover 28 is cold bent in the autoclave. The assembled laminated is processed, using standard automotive laminating equipment. [0090] 5. The windshield, similar to the one illustrated in FIG. 8, has a rectangular opening for the camera field of view 32, in the black obscuration 6, that top by 200 mm wide and a height of 100 mm for a heated area of 2 dm2 The defroster circuit is designed to have a power density of at least 15 watts/dm2. With a heated area of 1.5 dm2 the minimum power must be 30 watts. The supply voltage is 13 volts. [0091] The laminate has a standard soda-lime 2.5 mm thick clear exterior glass layer 201 and 2.1-mm soda-lime solar green interior glass layer 202. Obscuration 6 is screen printed on surface two 102 and surface four of the laminate. The obscuration 6 frames the camera field of view 32 area and hides the camera assembly. The glass layers are thermally bent using a gravity bending process. [0092] In this embodiment, the defroster circuit comprises an embedded wire circuit 22 designed to meet the power requirements using an 18 m tungsten wire which is embedded in a 0.76 layer of PVB (adhesive layer) 26. [0093] During assembly of the laminate, as shown in FIG. 4, wire embedded PVB is placed on the number four surface of the laminate followed by the 0.4 mm chemically tempered aluminosilicate flat glass cover 28. The flat glass cover 28 is cold bent in the autoclave. The assembled laminated is processed, using standard automotive laminating equipment.

[0094] In some embodiments (not shown in figures), a laminated glazing with a camera field of view comprises an exterior and an interior glass layers, wherein the interior glass layer has a cutout in the camera field of view. The laminated glazing further comprises a plastic bonding layer located between the exterior and the interior glass layers, a resistive heating circuit configured to heat at least a portion of the camera field of view, and a transparent glass cover that fits within said cutout; wherein the resistive heating circuit is located between the transparent glass cover and the exterior glass layer. Additionally, in several embodiment, the transparent glass cover may be bonded to the exterior glass layer by means of said at least one plastic bonding layer. In some preferred embodiments, the laminated glazing further comprises at least one adhesive layer, wherein said at least one plastic layer has a cut out in the camera field of view, and wherein the transparent glass cover is bonded to the exterior glass layer by means of said at least one adhesive layer.