Field of the invention This invention relates to the field of automotive glass laminates.

Background of the invention A popular option on new cars, that has seen rapid growth over the last several years, is the panoramic glass roof 14 shown in Figures 1A and IB. A vehicle so equipped has a roof that is comprised substantially of glass 2. The large panoramic glass roof 14 gives the vehicle an airy and luxurious look. In recent years, on models offered with a panoramic roof option in North American and Europe, the take rate has been in the 30% to 40% range. In China, the rate has been close to 100% on some models.

Panoramic roofs are fabricated from annealed laminated glass. The smaller "sun" or "moon" roofs as they were sometimes called were typically fabricated from tempered glass. Tempered glass is glass that has been heat strengthened. Heat strengthened, full temper soda lime float glass, with a compressive strength in the range of at least 70 Mpa, can be used in all vehicle positions other than the windshield. Heat strengthened (tempered) glass has a layer of high compression on the outside surfaces of the glass, balanced by tension on the inside of the glass which is produced by the rapid cooling of the hot softened glass. When tempered glass breaks, the tension and compression are no longer in balance and the glass breaks into small beads with dull edges. Tempered glass is much stronger than annealed laminated glass.

When a tempered glass roof fails, the roof opening 20 is left open and unprotected. In the event of a crash, an occupant could be ejected from the vehicle through the opening. As a result, the much larger panoramic roof glazings must be made from laminated safety glass. Panoramic roofs are generally bonded to the vehicle sheet metal 18 by means of an adhesive 7. Laminated safety glass is made by bonding two sheets of annealed glass 2 together using a thin sheet of a transparent thermo-plastic (plastic bonding layer) 4. 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 layer helping to maintain the structural integrity of the glass. A vehicle with a broken windshield can still be operated. On impact, the plastic layer also helps to prevent penetration by the occupant in the event of a crash and by objects striking the laminate from the exterior.

A big part of the appeal of the panoramic roof comes from the sleek modern appearance that it gives the vehicle with one continuous expanse of glass starting at the rear of the hood, running up the windshield, across the roof and down the back to the start of the trunk or hatch. However, improvements in display and illumination technology, have had an adverse impact on the interior aesthetics of the panoramic roof.

The proliferation of electronic devices coupled with improvements in the cost, brightness, and weight of LED, OLED, Electroluminescent and other types of displays have resulted in an increase in the quantity, brightness and size of the various displays used in modern vehicles. On many vehicles, the instrument panel is now substantially a digital display. Multifunction centrally mounted dashboard displays are also used to control various functions, display alerts, display backup camera images and to provide for GPS navigation. These displays are approaching or exceeding the size of some notebook and table computers. At the same time, solid state lighting is displacing incandescent lighting and allowing for applications that would not have been practical or possible with the older technology. We are seeing lighting now in areas of the cabin that were not typically illuminated in the past. In general, the cabin is getting brighter. Normal uncoated glass reflects about 8% of visible light. At 8%, a panoramic roof acts much like an overhead mirror, especially at night and even more so with a light colored interior. The reflections have an adverse effect on the aesthetics of the cabin and can become distracting. Attempts to solve the problem, through the application of various types of anti-reflection and anti-glare coatings and surface treatments, have not been successful. While all made for some improvement, none were effective enough to justify their added cost.

Clearly, it would be advantageous to eliminate these reflections.

Brief summary of the invention

As discussed initial attempts to solve the problem through the application of various types of anti-reflection and anti-glare coatings and surface treatments were not successful. While all made for some improvement, none were effective enough to justify their added cost. Even with the best performing coatings and treatments the reflected images were still clearly visible even at the lower intensity. However, this was with a laminate, having a total visible light transmittance of 20%, comprising dark solar green glass on the interior and exterior layers and a clear plastic PVB bonding layer.

Surprising results were obtained by switching to lighter tinted glass but with a dark tint PVB bonding layer. This composition was used to produce a laminate with a total visible light transmittance of less than about 5%. On the original laminate, with a visible light transmittance of 20%, while the anti-reflecting coating was able to reduce the reflectance from the number four surface, the coating also increased the quantity of light transmitted into the laminate. Typically, when an anti -reflective coating is applied, the increase in transmittance is about equal to the decrease in reflectance. This is why anti-reflective coatings are used for the cover glass of solar panel. In this case, if we reduce the reflectance from 8% to 1%, we increase the transmittance by about 7%. The more intense transmitted light is then reflected off of the number three, two and one surfaces. The secondary reflections are actually more intense with the anti-reflective coating than without. When a dark PVB layer is used, the transmitted light is absorbed before it can reach the number two and number one surfaces and so that much less light is returned by the secondary reflections. The path of a light ray through the laminate is illustrated in Figure 2. The invention corresponds to a panoramic laminated glass roof comprising an anti-reflection coating deposited onto the number four surface of the interior glass layer by a physical vapor deposition (PVD) process. The anti -reflection coating minimizes reflection to virtually eliminate secondary reflections and reduces the total reflection in the visible region to as low as 0.6%. In conjunction with the anti-reflection coating a dark tint glass and/or dark tint plastic bonding layer is used to reduce the total visible light transmission to less than 5%. By lowering the visible light transmission the multiple secondary reflections from the other surfaces are further minimized. The lower light transmission also allows for the possibility of eliminating a mechanical sun shade, improves privacy and can be used to further hid additional value added components that can be embedded into the plastic layer such as LEDs for illumination and signaling, solar cells, touch sensors and antennas.

Advantages include:

• Improved interior aesthetic.

· Increased privacy

• Less distracting for driver and passed

• Increased headroom.

• Lower cost due to elimination of shade.

• Improved solar control.

Brief description of drawings

Figure 1A shows the section view showing laminated panoramic roof and sheet metal opening in vehicle.

Figure IB shows the isometric view: laminated panoramic roof and sheet metal opening in vehicle.

Figure 2 shows a light path through laminate.

Figure 3 shows a typical laminated glazing cross section.

Figure 4 shows embodiment 1.

Figure 5 shows embodiment 2.

Figure 6 shows embodiment 3.

Figure 7 shows embodiment 4. Reference numerals

2 Glass layer

3 Infrared reflecting film

4 Bonding plastic layer

5 Infrared reflecting coating

6 Black frit

7 Adhesive

12 Path of a light ray

14 Panoramic glass roof

16 Edge of black paint

17 Anti-reflective coating

18 Vehicle sheet metal (Roof Panel)

20 Roof Panel Opening

101 Surface number one

102 Surface number two

103 Surface number three

104 Surface four

201 Layer one - exterior layer, adjacent to the exterior of the vehicle.

202 Layer two - interior layer, adjacent to the inside of the passenger compartment.

Detailed description of the invention The object of the present invention is to provide a laminated panoramic roof with low reflectivity of the interior surface and improved aesthetics.

Standard terminology is used to describe the configuration of a laminated glazing (Figure 3). A normal automotive windshield is comprised of two layers of glass that are permanently bonded together. The glass surface that is on the outside of the vehicle is referred to as surface one 101 or the number one surface. The opposite face of the exterior layer of glass 201 is surface two 102 or the number two surface. The glass surface that is on the inside of the vehicle is referred to as surface four 104 or the number four surface. The opposite face of the inside layer of glass 203 is surface three 103 or the number three surface.

Glass options include but are not limited to: the common soda-lime variety typical of automotive glazing as well as aluminosilicate, lithium aluminosilicate, borosilicate, glass ceramics, and the various other inorganic solid amorphous compositions which undergo a glass transition and are classified as glass included those that are not transparent.

One of the big advantages of a laminated roof over a painted sheet metal roof is that the laminate can more efficiently reflect solar energy through the use of an infrared reflecting coating 5 or film 3 as shown in any of the Figures 4 and 7. Even without an infrared reflecting layer, glass will reflect more solar energy than a painted surface. Glass, being a poor conductor of heat, also helps to slow the transfer of solar energy to the passenger cabin while with an emissivity of over 0.9, it helps to cool a hot vehicle by radiating heat from the inside of the vehicle to the outside air.

Infrared reflecting coatings 5 include but are not limited to the various metal/dielectric layered coatings applied though vacuum deposition as well as others known in the art that are applied via pyrolytic, spray, CVD and dip. Coated layers may have a dark tint substrate or have a dark tint layer opposite the infrared reflecting layer. The dark tint layer may also be created by printing a dark tint ink onto the non-coated side of the substrate.

Infrared reflecting films 3 includes both metallic coated substrates as well as organic based optical films 3 which reflect in the infrared. Film 3 may also include a dark tint coating or layer opposite the infrared reflecting surface.

The bonding layer 4 has the primary function of bonding the major faces of adjacent layers to each other. As an example, surface two of the top glass layer 2 is bonded to surface one of the layer adjacent and below by the bonding layer 4. The material selected is typically a clear plastic when bonding to another glass layer 2. For automotive use, the most commonly used bonding layer 4 or 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. The bonding layer 4 can also serve as the dark tint layer. Dark tint PVB is available in black as well as a wide variety of other colors which can also be used. The dark tint layer can also be created by printing with a dark tint ink on the bonding layer 4.

Black frit 6 is a type of ink made from a mix of high temperature black pigments, fine ground glass and an organic carrier and binder. Black frit 6 is commonly applied by silk screen printing or ink jet printing and used on automotive glazing to provide for an obscuration to hide the interior trim and the adhesive used to mount the glazing in the vehicle. The frit is applied before the bending of the glass. During the bending process, the glass powder fuses with the surface of the glass making for a durable permanent bond.

Glazing, in the context of this document shall mean any safety glazing certified to any of the regulatory standards for automotive safety glazing.

Anti-reflective coating are widely known in the art. Anti-glare coatings serve a similar function and are included. Coatings can applied using a MSVD process, by a pyrolytic process or by a sol-gel process. Surface treatments can also be used to provide for an antiglare surface. As can be appreciated, other chemistries, treatments and application methods are available and will become available which are equivalent.

Glass layers are formed using gravity bending, press bending or cold bending. Gravity and press bending methods for forming glass are well known in the art and will not be discussed here.

Detailed description of the embodiments

Figure 4 shows the laminate of embodiment one further comprising an exterior glass layer 201 having a magnetron sputter vacuum deposition (MSVD) deposited Silver based coating 5 deposited on the number two 102 surface of the glass, further improving the solar performance of the roof.

Figure 5 shows the laminate of embodiment one further comprising an interior glass layer 202 having an MSVD deposited Silver based coating 5 deposited on the number three 103 surface of the glass, further improving the solar performance of the roof. Figure 6 shows the cross section of a laminated panoramic roof comprising two 2.1 mm clear glass layers, the interior 202 and the exterior 201 layers, with an anti- reflective coating 17 applied to the number four 104 surface of the interior layer of glass 202. The coating is applied to the flat glass by a PVD process prior to cutting of the glass shape from the flat glass. A black frit "band" 6 is printed on the number four 104 surface over top of the anti-reflective coating 17. A dark grey tint, 0.76 mm PVB bonding interlayer with a visible light transmittance of 5% is used to bond the two glass layers together. The total reflectance of the assembled laminate is less than 0.5%.

Figure 7 shows the laminate of embodiment one further comprising a non-metallic organic infrared reflecting film 3, sandwiched between the 0.76 mm PVB layer 4 of embodiment one and a second 0.38 mm clear PVB layer 4 further improving the solar performance of the roof.

In an alternative embodiment of that depicted in Figure 7, the laminate further comprising a Suspended Particle Device (SPD) electrically controlled variable light transmittance film, sandwiched between the 0.76 mm 50% light transmittance grey PVB layer and a second 0.38 mm clear PVB layer further improving the solar performance of the roof. In the off state, the SPD layer reduces light total visible light transmittance to under 5%. In the on state, the visible light transmission is 40%. This allow for abundant light and visibility during the day or reflection free driving at the drivers control. The forms of the invention shown and described in this specification represent illustrative preferred embodiments and it is understood that various changes may be made without departing from the spirit of the invention as defined in the following claimed subject matter.