LAMINATE WITH LOW-E COATING ON THIN CHEMICALLY STRENGTHENED GLASS AND METHOD OF MANUFACTURE

Abstract

An automotive laminated glazing is provided, comprising an outer glass layer and an inner glass layer, said outer glass layer having a first surface and a second surface and said inner glass layer having a third surface and a fourth surface, wherein the inner glass layer has a thickness of not more than 1.0 mm and is chemically strengthened, and wherein the fourth surface features a low-e coating, obtainable by chemically strengthening a flat glass pane having a thickness of not more than 1.0 mm, then applying the low-e coating, and finally laminating the flat glass pane to a curved glass pane forming the outer layer, thereby cold bending said flat glass pane.

Claims

1. An automotive laminated glazing comprising: a curved outer glass layer having two oppositely disposed major surfaces, a first surface and a second surface; an inner glass layer having two oppositely disposed major surfaces, a third surface and a fourth surface; wherein the inner glass layer is a chemically strengthened glass layer having no more than 1.0 mm in thickness; a low-e coating applied on the fourth surface of the inner glass layer; and at least one plastic bonding layer disposed between second and third surfaces; wherein the inner glass layer adopts the shape of the outer glass layer when joined together.

2. The automotive laminated glazing of claim 1, wherein the low-e coating is comprised of a three-layer MSVD deposited stack comprising SiNx/ITO/SiNx.

3. The automotive laminated glazing of claim 1, wherein the low-e coating is comprised of a three-layer MSVD deposited stack comprising SiOxNy/ITO/SiOxNy.

4. The automotive laminated glazing of claim 1 further comprising an anti-reflective coating applied over the low-e coating.

5. The automotive laminated glazing of claim 4, wherein the anti-reflective coating comprises a two-layer MSVD coating, a first layer having a low refractive index and a second layer having a high refractive index.

6. The method of claim 4, wherein the anti-reflective coating comprises a three-layer MSVD coating, a first layer having a low refractive index, a second layer having a high refractive index, and a third layer having a medium refractive index.

7. The method of claim 4, wherein the anti-reflective coating comprises a four-layer MSVD coating, a first and a third having a low refractive index and a second and a fourth layers having a high refractive index.

8. The automotive laminated glazing of claim 1 further comprising an anti-fingerprint coating applied to the interior facing surface.

9. The automotive laminated glazing of claim 4 further comprising an anti-fingerprint coating applied over the anti-reflective coating.

10. The automotive laminated glazing of claim 1 further comprising an infra-red reflecting coating applied on the second surface of the outer glass layer.

11. The automotive laminated glazing of claim 1 further comprising an infra-red reflecting film to the laminate.

12. A method for producing an automotive laminate comprising at least two glass layers, the method comprising the steps of: providing a curved outer glass layer having two oppositely disposed major surfaces, a first surface and a second surface; providing an inner glass layer having two oppositely disposed major surfaces, a third surface and a fourth surface, wherein: i. said layer is of a thickness that it less than or equal to 1.0 mm, ii. the fourth surface comprises an interior surface of the passenger compartment of the vehicle when installed as a window in a vehicle; said inner glass layer is cut, edged, cleaned, and otherwise prepared as needed for ion exchange chemical strengthening; said inner glass layer is chemically strengthened by an ion exchange process; said inner glass layer is coated with a low-e coating on the fourth surface comprising an interior surface of the passenger compartment of the vehicle; providing at least one plastic bonding layer disposed between second and third surfaces; said strengthened coated inner glass layer is cold bent to adopt the shape of the outer glass layer during the lamination process.

13. The method of claim 12 comprising the additional step of thermal activation of the coating.

14. The method of claim 12 further comprising the additional step of applying an anti-reflective coating over the low-e coating.

15. The method of claim 12 further comprising an anti-fingerprint coating applied to the interior facing surface.

16. The method of claim 12 comprising the additional step of adding an infra-red reflecting film to the laminate.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0050] The following terminology is used to describe the laminated glazing of the invention.

[0051] A glazing is an article comprised of at least one layer of a transparent material which serves to provide for the transmission of light and/or to provide for viewing of the side opposite the viewer and which is mounted in an opening in a building, vehicle, wall or roof or other framing member or enclosure.

[0052] Typical automotive laminated glazing cross sections are illustrated in FIGS. 1A and 1B. A laminate is comprised of two layers of glass 2, the exterior or outer 201 and the interior or inner 202 that are permanently bonded together by a plastic layer 4 (interlayer). In a laminate, 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 2 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 layer 4. An obscuration 6 may be also applied to the glass. Obscurations are commonly comprised of black enamel frit printed on either the number two 102 or number four surface 104 or on both. The laminate may have a coating 18 on one or more of the surfaces. The laminate may also comprise a film 12 laminated between at least two plastic layers 4.

[0053] The term “glass” can be applied to many organic and inorganic materials, include many that are not transparent. For this document we will only be referring to nonorganic transparent glass. From a scientific standpoint, glass is defined as a state of matter comprising a non-crystalline amorphous solid that lacks the ordered molecular structure of true solids. Glasses have the mechanical rigidity of crystals with the random structure of liquids.

[0054] Glass is formed by mixing various substances together and then heating to a temperature where they melt and fully dissolve in each other, forming a miscible homogeneous fluid.

[0055] The types of glass that may be used 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. The glass layers may be comprised of heat absorbing glass compositions and may also utilize infrared reflecting and other types of coatings.

[0056] Most of the glass used for containers and windows is soda-lime glass. Soda-lime glass is made from sodium carbonate (soda), lime (calcium carbonate), dolomite, silicon dioxide (silica), aluminum oxide (alumina), and small quantities of substances added to alter the color and other properties.

[0057] Borosilicate glass is a type of glass that contains boric oxide. It has a low coefficient of thermal expansion and a high resistance to corrosive chemical. It is commonly used to make light bulbs, laboratory glassware, and cooking utensils.

[0058] Aluminosilicate glass is made with aluminum oxide. It is even more resistant to chemicals than borosilicate glass and it can withstand higher temperatures. Chemically strengthened Aluminosilicate glass is widely used for displays on smart phones and other electronic devices.

[0059] Lithium-Aluminosilicate is a glass ceramic that has very low thermal expansion, and high optical transparency. It typically contains 3-6% Li2O. It is commonly used for fireplace windows, cooktop panels, lenses and other applications that require low thermal expansion.

[0060] The glass layers may be annealed or strengthened. There are two processes that can be used to increase the strength of glass. They are thermal strengthening, in which the hot glass is rapidly cooled (quenched) and chemical strengthening which achieves the same effect through an ion exchange chemical treatment.

[0061] 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 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 strengthened glass breaks, the tension and compression are no longer in balance and the glass breaks into small beads with dull edges. Strengthened glass is much stronger than annealed laminated glass. The thickness limits of the typical automotive heat strengthening process are in the 3.2 mm to 3.6 mm range. This is due to the rapid heat transfer that is required. It is not possible to achieve the high surface compression needed with thinner glass using the typical blower type low pressure air quenching systems.

[0062] In the chemical strengthening process, ions in and near the outside surface of the glass are exchanged with ions that are larger. This places the outer layer of glass in compression. Compressive strengths of up to 1,000 MPa are possible. The typical methods involved submerging the glass in a tank of molten salt where the ion exchange takes place. The glass surface must not have any paint or coatings that will interfere with the ion exchange process.

[0063] A wide range of coatings, used to enhance the performance and properties of glass, are available and in common use. These include but are not limited to: low emissivity, infra-red reflecting, anti-reflective, hydrophobic, hydrophilic, self-healing, self-cleaning, anti-bacterial, anti-scratch, anti-graffiti, anti-fingerprint and anti-glare.

[0064] Methods of coating application include Magnetron Sputtered Vacuum Deposition (MSVD) as well as others known in the art that are applied via pyrolytic, spray, controlled vapor deposition (CVD), dip, sol-gel and other methods.

[0065] The glass layers are formed using gravity bending, press bending, cold bending or any other conventional means known in the art. In the gravity bending process, the glass flat is supported near the edge of glass and then heated. The hot glass sags to the desired shape under the force of gravity. With press bending, the flat glass is heated and then bent on a full of partial surface mold. Air pressure and vacuum are often used to assist the bending process. Gravity and press bending methods for forming glass are well known in the art and will not be discussed in detail 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 axes. The process is primarily used to bend chemically strengthened 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 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 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 4 (interlayer) has the primary function of bonding the major faces of adjacent layers to each other. The material selected is typically a clear thermoset plastic.

[0071] For automotive use, the most commonly used bonding layer 4 (interlayer) is polyvinyl butyral (PVB). PVB has excellent adhesion to glass and is optically clear once laminated. It is produced by the reaction between polyvinyl alcohol and n-butyraldehyde. PVB is clear and has high adhesion to glass. However, PVB by itself is too brittle. Plasticizers must be added to make the material flexible and to give it the ability to dissipate energy over a wide range of temperature required for an automobile. Only a small number of plasticizers are used. They are typically linear dicarboxylic esters. Two in common use are di-n-hexyl adipate and tetra-ethylene glycol di-n-heptanoate. A typical automotive PVB interlayer is comprised of 30-40% plasticizer by weight.

[0072] 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. Automotive interlayers are made by an extrusion process which has a thickness tolerance and process variation. As a smooth surface tends to stick to the glass, making it difficult to position on the glass and to trap air, the surface of the plastic is normally embossed to facilitate the handling of the plastic sheet and the removal or air (deairing) from the laminate. This process however contributes to additional variation to the sheet. Standard thicknesses for automotive PVB interlayer are 0.38 mm and 0.76 mm (15 and 30 mil).

[0073] 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 what is normally used. The interlayer may also be of a type which has solar attenuating properties.

[0074] Laminates, in general, are articles comprised of multiple sheets of thin material, relative to their length and width, with each thin sheet having two oppositely disposed major faces and typically of relatively uniform thickness, which are permanently bonded to one and other across at least one major face of each sheet.

[0075] Laminated safety glass is made by bonding two sheets (201 & 202) of annealed glass 2 together using a plastic bonding layer comprised of a thin sheet of transparent thermoplastic 4 (interlayer) as shown in FIG. 1.

[0076] 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. The plastic layer 4 also helps to prevent penetration by objects striking the laminate from the exterior and in the event of a crash occupant retention is improved. A wide variety of films are available that can be incorporated into a laminate. The uses for these films include but are not limited to: solar control, variable light transmission, increased stiffness, increased structural integrity, improved penetration resistance, improved occupant retention, providing a barrier, tint, providing a sunshade, color correction, and as a substrate for functional and aesthetic graphics. The term “film” shall include these as well as other products that may be developed or which are currently available which enhance the performance, function, aesthetics or cost of a laminated glazing. Most films do not have adhesive properties. To incorporate into a laminate, sheets of plastic interlayer are needed on each side of the film to bond the film to the other layers of the laminate.

[0077] Automotive glazing often makes use of heat absorbing glass compositions to reduce the solar load on the vehicle. While a heat absorbing window can be very effective the glass will heat up and transfer energy to the passenger compartment through convective transfer and radiation. A more efficient method is to reflect the heat back to the atmosphere allowing the glass to stay cooler. This is done using various infrared reflecting films and coatings. Infrared coatings and films are generally too soft to be mounted or applied to a glass surface exposed to the elements. Instead, they must be fabricated as one of the internal layers of a laminated product to prevent damage and degradation of the film or coating.

[0078] One of the big advantages of a laminated window over a strengthened monolithic glazing is that a laminate can make use of infrared reflecting coatings and films in addition to heat absorbing compositions and interlayers.

[0079] Infrared reflecting coatings 18 include but are not limited to the various metal/dielectric layered coatings applied though Magnetron Sputtered Vacuum Deposition (MSVD) as well as others known in the art that are applied via pyrolytic, spray, controlled vapor deposition (CVD), dip and other methods.

[0080] Infrared reflecting films include both metallic coated plastic substrates as well as organic based non-metallic optical films which reflect in the infrared. Most of the infrared reflecting films are comprised of a plastic film substrate having an infrared reflecting layered metallic coating applied.

[0081] The black frit print obscuration on many automotive glazings serves both a functional and an aesthetic role. The substantially opaque black print on the glass serves to protect the poly-urethane adhesive used to bond the glass to the vehicle from ultra-violet light and the degradation that it can cause. It also serves to hide the adhesive from view from the exterior of the vehicle. The black obscuration must be durable, lasting the life of the vehicle under all exposure and weather conditions. Part of the aesthetic requirement is that the black has a dark glossy appearance and a consistent appearance from part to part and over the time. A part produced today must match up with one that was produced and in service 20 years ago. The parts must also match up with the other parts in the vehicle which may not have been fabricated by the same manufacturer or with the same formulation of frit. Standard automotive black enamel inks (frits) have been developed that can meet these requirements.

[0082] Other means are sometimes used to provide an obscuration when a black frit is not practical as is the case when the substrate will be chemically strengthened, or the surface has been coated with a coating that is not compatible with the printing process. These include but are not limited to organic inks, primers and inserts.

[0083] Thermal energy is transferred through glass by means of convective transfer or by being radiated by the glass surface. Emissivity is a measure of how much energy a surface will radiate. Emissivity is quantified as the ratio of heat emitted by an object to that of a perfect black body. The ratio of a perfect black body is 1 while the ratio of a perfect reflector is zero. Standard clear soda-lime glass has an emissivity of 0.84, radiating 84% for the heat absorbed, making it a poor insulator. As a result, windows made of soda-lime glass have poor thermal properties. To improve the thermal properties, coatings have been devised which lower the emissivity of the glass surface. These coating, known as low-e, greatly reduce the quantity of thermal radiant heat energy emitted. This energy emitted a major component of the heat transfer of a window. Reducing the emissivity of the glass surface greatly improves its insulating properties. Low-e coatings are known having an emittance as low as 0.04, emitting only 4% the energy and reflecting back 96% of the energy. Low-e coating often have the property of reflecting in the infra-red on the substrate side of the coating further improving the thermal properties by reducing energy transfer from outside. A desirable characteristic when we are trying to cool the interior.

[0084] While a number of methods may be employed to apply the low-e coating of the invention, a magnetron sputtering vacuum deposition (MSVD) coater using bipolar pulsed DC power supply has been found to produce coating films with better uniformity and higher conductivity.

[0085] Some types of low-e coatings are enhanced though the process of thermal activation. During this process, the coated substrate is heated to temperature and held for a duration sufficient to allow certain changes to take place in the coating which further improve the thermal properties of the coating. This optional step may be included depending upon the type of low-e coating applied.

[0086] The first layer deposited on the substrate 32 shall be referred to as layer 1. Subsequent layers shall be incremented by 1. The order is shown in FIG. 4. The glass substrate 32 is shown with a five-layer coating stack 19.

[0087] Note that in chemical formulas, an exact number will be used for any subscript where a specific compound is required. The use of a variable, such as x or y, indicates that the claimed compound includes all possible values of the variable. If the formula HxO is used, then the compounds HO and H.sub.2O are both claimed. Due to the manner in which MSVD and other coating are deposited, we will typically have multiple compounds formed.

DESCRIPTION OF EMBODIMENTS

[0088] All of the articles produced by the various embodiments of the method described are illustrated by FIGS. 3 and 4. The laminate shown is a 1.2 meter by 1.6 meter panoramic laminated roof. The outer glass layer 201 is thermally bent 2.1 mm thick, dark solar green, soda-lime glass. A black frit obscuration 6 is printed and fired on surface two 102 of the outer glass layer 201. The inner glass layer 202 is 1.0 mm thick alumina silicate glass which has been chemically strengthened by an ion exchange process. The bent outer glass layer 201 and the flat coated inner glass layer 202 are laminated with an 0.76 mm layer of dark gray tint PVB. The low-e coating is applied to surface four 104 after ion exchange by a magnetron sputter vacuum deposition coater. The total visible light transmission of the laminate is under 5%.

Embodiment 1

[0089] 1. In method of embodiment 1 the soda-lime outer glass is cut to size, the edge of the cut glass is diamond wheel ground to a smooth finish and then the glass is washed. A black frit obscuration 6 is then screen printed on surface two 102 of the outer glass layer 201. The glass is then heated and bent to shape, using a full surface press bending process, and annealed. [0090] 2. Separately, the inner glass layer 202, a 1.0 mm clear alumina silicate glass, is cut to size by means of a femto-second LASER. No edge work is needed. The cut glass is washed and prepared for the ion exchange process. [0091] 3. When a sufficient number of layers have been prepared, they are process by the ion exchange process. Following the ion exchange, the glass is prepared for coating by again washing the glass to remove any remnants of the salt bath. [0092] 4. The glass is then passed through an MSVD coater which applies a three-layer low-e coating to what will become surface four 104 of the laminate.

TABLE-US-00003 Layer 1: SiNx 21 Layer 2: ITO (Indium Tin Oxide) 22 Layer 3: SiNx 23 [0093] 5. The coated glass is now ready for the lamination. A sheet of PVB 4 is placed between the two layers, the bent outer glass layer 201 and the flat inner glass layer 202 are joined together by means of a vacuum channel. The air is evacuated drawing the surfaces together and bending the thin flat inner glass layer 202 to the contour of the outer glass layer 201. Subsequent treatment with heat, vacuum and pressure permanently bond the two layers together.

Embodiment 2

[0094] Embodiment 2 is the same as embodiment 1 with the exception of the low-e coating. The MSVD coating stack is comprised as follows.

TABLE-US-00004 Layer 1: SiOyNx 21 Layer 2: ITO (Indium Tin Oxide) 22 Layer 3: SiOyNx 23

Embodiment 3

[0095] Embodiment 3 is the same as embodiment 1 but with the addition of a two-layer anti-reflective MSVD coating applied over the MSVD low-e coating with the anti-reflective stack comprised as follows.

TABLE-US-00005 Layer 4: low refractive index 24 Layer 5: high refractive index 25

Embodiment 4

[0096] Embodiment 4 is the same as embodiment 2 but with the addition of a two-layer anti-reflective MSVD coating applied over the MSVD low-e coating with the anti-reflective stack comprised as follows.

TABLE-US-00006 Layer 4: low refractive index 24 Layer 5: high refractive index 25

Embodiment 5

[0097] Embodiment 5 is the same as embodiment 1 but with the addition of a four-layer anti-reflective MSVD coating applied over the MSVD low-e coating with the anti-reflective stack comprised as follows.

TABLE-US-00007 Layer 4: low refractive index 24 Layer 5: high refractive index 25 Layer 6: low refractive index 26 Layer 7: high refractive index 27

Embodiment 6

[0098] Embodiment 6 is the same as embodiment 2 but with the addition of a four-layer anti-reflective MSVD coating applied over the MSVD low-e coating with the anti-reflective stack comprised as follows.

TABLE-US-00008 Layer 4: low refractive index 24 Layer 5: high refractive index 25 Layer 6: low refractive index 26 Layer 7: high refractive index 27

Embodiment 7

[0099] Embodiment 7 is the same as embodiment 1 but with the addition of a three-layer anti-reflective MSVD coating applied over the MSVD low-e coating with the anti-reflective stack comprised as follows.

TABLE-US-00009 Layer 4: low refractive index 24 Layer 5: high refractive index 25 Layer 6: medium refractive index 26

Embodiment 8

[0100] Embodiment 8 is the same as embodiment 2 but with the addition of a three-layer anti-reflective MSVD coating applied over the MSVD low-e coating with the anti-reflective stack comprised as follows.

TABLE-US-00010 Layer 4: low refractive index 24 Layer 5: high refractive index 25 Layer 6: medium refractive index 26

Embodiments 9-16

[0101] The eight embodiments comprising embodiment 9-16 are produced by adding the additional step of applying an anti-fingerprint coating to the laminates of embodiments 1-8. The anti-fingerprint coating may be applied by an MSVD process or any other method appropriate to the coating.