Solar control glass assembly and method of making same.

DESCRIPTION

The present invention relates to glass structures for controlling the transmission of solar energy in general and, in particular, to automobile glasses for transmitting light in the visible spectrum while blocking solar radiation outside the visible spectrum.

Generally, two methods, or some combination of them, are used to reduce the transmission of solar energy through the glass. The first method is absorption, in which solar energy outside a particular bandwidth is absorbed by predetermined elements existing in the glass and radiated again as heat. For example, US Pat. nuóm. 2,860,059 describes a light absorbing glass suitable for glazing applications in automotive and architecture. In a laminated car windshield, in which two glass lamines are glued to an intermediate poly (vinyl butyral) queen layer, the plastics layer is provided with a colored band that extends through the top of the windshield , whose band gradually decreases in light transmittance to provide a full built-in anti-glare screen with the windshield. An ultraviolet light absorbing glass was provided in at least the outer glass laminin to protect the colored band from decolorization and other damaging effects of the sun. Glass is an ordinary glass of soda-lime-silica to which ultraviolet cutting materials are added, such as choic oxide and titanium dioxide combined with folate.

It is important that the automotive glass has a low total solar transmission, with a relatively high transmission in the visible spectrum. Federal standards in the United States require that the Illuminator A value of automotive glass be at least seventy percent of the value of clear clear glass at a thickness of 6.35 mm in the visible spectrum (wavelengths of 400-700 millimicras). This requirement ensures that the driver will have enough transmission through the glass to be able to distinguish a car headlight and other sources of visible background light.

As it is also desirable to stop infrared radiation, much work has been done on car glasses that block the transmission of sunlight at both ends of the visible spectrum. The United States federal Illuminator A standard is at least seventy percent transmittance in the visible spectrum at a thickness of 6.35 mm. To consider that it is a heat absorbing glass, the total solar transmittance must be less than fifty percent in the same thickness. A method for manufacturing heat absorbing glass is to add iron and tin to the glass and keep at least eighty percent of the iron in the glass in the ferrous state during the melting, refining and reforming of the glass. In addition, sufficient tin must be maintained in a stannous state to act as an internal reducing agent to prevent further oxidation of ferrous iron to ferric species at a later stage of glass overheating.

By introducing other infrared absorbing compounds into the glass batch materials, radiation could be absorbed at the infrared end of the spectrum while manufacturing a glass for automotive that met the Illuminator A standards. The other method of reducing solar transmission is reflection. . A reflective material, such as silver, is applied as a coating directly on the surface of the glass or on the surface of a plastics laminate which is then adhered to the glass.

The addition of tin oxide can reduce the transmission of basic automotive glass. However, this technique produces only marginal solar gain since the absorbed energy can be radiated both outwardly and into the vehicle. Re-radiated energy inside the vehicle is a solar gain that is added to the direct solar gain that passes through the glass without being absorbed. As the amount of glass laminating used in vehicles increases, it also increases in solar gain, demanding an increased effort on air conditioning equipment.

A better solution is to increase the total solar reflection of the glass by the addition of coatings applied directly to the glass or to a carrier film such as a polyester, which can be applied to the glass. The light coming from the sun that is reflected and not absorbed, is not a gain for the car, since it is not transformed into heat but remains as light. The other advantage of a reflective coating on an absorber glass is that the reflective coating maintains a growing advantage over the absorber glass when the wind becomes increasingly low. The temperature of the glass for an absorber glass increases with the lower speed of the invention and, consequently, loses more energy into the car.

The present invention uses an induced transmission filter combined with an automotive glass to obtain improved filtration characteristics of the glass with respect to solar gain. The filter maintains high transmission on the visible part of the solar spectrum and also has high reflection on the infrared part. The filter includes a stack of coatings that are applied on one side of a polyester ester film, with a hard layer applied on the other side of the film. The coverings face the inner surface of the glass and the hard layer faces the inside of the car to prevent damage to the coverings and the film during normal use. An additional polyester film can be applied to the surface of the coatings when certain types of adhesives are used to bond the film to the glass.

A glass assembly according to the present invention that provides improved resistance to solar transmission and meets federal standards Illuminator A of the United States, consists of a carrier film made of poly (ethylene terephthalate) (PET) that has a resistant coating the abrasion or hard layer on one side and layers of a reflective coating on the other side. Each of the layers of coating

005 Reflective coating is a sandwich of a layer of metal film between two layers of dielectric coatings. For example, the metal film may be a layer of silver and the dielectric coatings may be layers of zinc oxide. Such a construction is applied to a layer of polyvinyl butyral on the inside of a glass substrate such as a single glass sheet or a laminated windshield having two layers of glass with a layer of polyvinyl butyral. between them. The two layers of reflective coating provide significantly better resistance to solar transmission than one layer and still meet Illuminator A.

The film is applied to the glass, either by adding it to a layer of polyvinyl butyral which is then applied to the glass, or using a pressure sensitive adhesive, or using a water activated adhesive. In the latter case, a polyester protective sheet is used between the adhesive and the reflective coating.

Figure 1

It is a fragmentary sectional view of a laminated glass assembly that includes a film to control the solar gain in accordance with the present invention.

Figure 2

It is an enlarged, fragmentary sectional view of the coating layer of Fig. 1. Figure 3

It is a fragmentary sectional view of an alternative embodiment of a glass assembly in accordance with the present invention.

Figure 4

It is an enlarged view of the bonding layer shown in Fig. 3 in accordance with the present invention.

Figure 5

It is a fragmentary sectional view of a second alternative embodiment of a glass assembly in accordance with the present invention.

Figure 6

It is a fragmentary sectional view of a third alternative embodiment of a glass assembly in accordance with the present invention.

In accordance with the present invention, a glass assembly is provided to control the solar transmission that includes a glass substrate having an inner and outer surface, characterized by an induced transmission filter layer adhered to said inner surface of said glass substrate , and an abrasion resistant layer adhered to said filter layer, whereby the Illuminator A transmission through the glass assembly is relatively high and the ultraviolet and infrared radiation transmission through the glass assembly is relatively low.

Also, according to the invention, a method is provided for making a glass assembly to control solar transmission, including obtaining a glass substrate, characterized by:

a) forming an induced transmission filter film having a first layer of dielectric material, a second layer of reflective material and a third layer of dielectric material;

b) adhering said film to a surface of said glass substrate; Y

c) adhering a layer of abrasion resistant material to said film to form in the glass assembly.

With reference to Fig. 1, a glass assembly 11 according to the present invention is shown. The assembly 11 may be, for example, a laminated vehicle windshield that includes an outer layer of transparent glass 12, an intermediate layer 13 of polyvinyl butyral and an inner layer 14 of transparent glass. The glass assembly 11 may be an anti-lining type that includes a protective layer 15 of polyvinyl butyral adhered to an inner surface of the inner layer 14 of glass.

The glass assembly 11 also includes an induced transmission filter formed as a film 16 adhered to an inner surface of the protective layer 15. The film 16 consists of a coating 17, the closest to the protective layer 15, an intermediate carrier 18 formed of a plastic material such as polyester, and a hard coating protective layer 19 that is substantially abrasion resistant. The intermediate layer 18 may be formed, for example, of a poly (ethylene terephthalate). The coating 17 is a reflective material that tends to reflect the ultraviolet and infrared wavelengths of the solar radiation back out through the layers 13 and 15 of polyvinyl butyral and the glass layers 12 and 14. Thus, the assembly has reduced solar gain towards the interior of the vehicle and also complies with federal standards Illuminator A of the United States.

An enlarged fragmentary sectional view of the coating 17 is shown in Fig. 2. The coating is a sandwich of a reflective metal material between two layers of dielectric material. For example, the coating 17 may include a first layer 20 of zinc oxide, a second layer or intermediate layer 21 of silver, a third layer 22 of zinc oxide. Then, the order of the layers is repeated with a fourth layer 23 of zinc oxide, a fifth layer 24 of silver and a sixth layer 25 of zinc oxide. The layers 20 to 25 are applied to the surface facing outward from the carrier 18 before being attached to the protective layer 15.

Other materials are suitable for use in the coating 17. For example, the dielectric material may be titanium dioxide, or indium or tin oxides. The reflective metallic material can be gold, or aluminum, or copper. Typically, the total thickness of the two dielectric layers and the reflective layer is in the order of two hundred twenty five to one thousand two hundred fifty angstroms. The reflective layer may be twenty five to two hundred and fifty angstroms and each dielectric layer may have one hundred to five hundred angstroms.

A fragmentary sectional view of a glass assembly 30 according to an alternative embodiment of the assembly 11 is shown in Fig. 3.

005 263 glass of Figs. 1 and 2. A glass sheet substrate 31 has a tie layer 32 formed on its inner surface. The uniaon layer 32 may be polyvinyl butyral or some form of adhesive structure using a pressure sensitive adhesive or a water activated adhesive, as shown in Fig. 4. The bonding layer 32 puts on contact a film 33 with the glass sheet 31. The film 33 may consist of a coating layer 34, a carrier layer 35, and a hard layer 36. Thus, the film 33 is similar to the film 16 shown in Fig. 1.

The uniaon layer 32 is shown in more detail in Fig. 4. A layer 37 of pressure sensitive adhesive or water activated adhesive is applied to one side of a carrier layer of a plastics material such as polyester, which is oriented towards the substrate 31. A pressure sensitive adhesive layer will be applied to the opposite side of the carrier layer 38 that is oriented to the coating layer 34.

A fragmentary sectional view of a second alternative embodiment of a glass assembly 40 is shown in Fig. 5. A glass sheet 41 has a coating 42 adhered to an inner surface thereof. The coating 42 will then be covered by an abrasion resistant layer 43. Layer 43 may be a hard layer or a polyvinyl butyral material.

Although it is shown as a stratified glass structure, the glass assembly 11 of Fig. 1 may be a side window or a rear window, which are typically constituted by a single layer of glass. Thus, the outer layer 12 and the intermediate layer 13 may be removed. Similarly, the glass assembly of Fig. 3 and the glass assembly 40 of Fig. 4 are shown with Uranic glass sheets. They may also be formed as stratified glass structures by adding an intermediate layer such as polyvinyl butyral layer 13 and the outer layer such as glass layer 12 of Fig. 1. Thus, the solar control glass assemblies shown in the Figures and described in the foregoing may be used in each window of a vehicle.

It has been found that a glass assembly of the type shown in Fig. 1, which has two coatings of the combination of zinc oxide and silver, meets the federal standards of Illuminator A of the United States of at least 70% in the spectrum visible, with total solar transmission of less than 40%, and total solar reflection greater than 25%. The coating configuration shown in Fig. two it has been found with the most suitable to reduce solar gain and comply with the federal Illuminator standard. A single set of filter layers does not provide enough reduction in the solar transmission to meet the solar gain requirements demanded by the automobile industry.

Fig. 6 is a fragmentary sectional view of a third alternative embodiment of a glass assembly 50. A glass sheet 51 has a layer 52 of polyvinyl butyral or similar material adhered to its inner surface. The next layer 53 is a film formed by a coating layer 54 and a carrier layer 55. The assembly 50 is completed with a second layer 56 of polyvinyl butyral and an outer layer of glass 57. Layers 56 and 57 replace the abrasion resistant layers of the first two embodiments.

005 263