LAMINATED GLAZING

Abstract

A laminated glazing for use as a combiner in a head up display comprises first and second glazing panes with at least one adhesive ply and an infrared reflecting film therebetween. Light incident upon the first glazing pane at an angle of incidence of 60 is reflected off the laminated glazing to produce first, second and third reflections, the third reflection being from light reflected from the infrared reflecting film. The laminated glazing further comprises light intensity reducing means between the first and second glazing panes for reducing the intensity of the third reflection. In an aspect, upon directing a beam of electromagnetic radiation having an intensity I.sub.O at 770 nm toward the first pane of glazing material at an angle of incidence of 60, the intensity of the third reflection at a wavelength of 770 nm is less than or equal to 0.185I.sub.O.

Claims

1.-46. (canceled)

47. A laminated glazing for use as a combiner in a head up display, the laminated glazing comprising at least two panes of glazing material joined by an interlayer structure comprising at least one adhesive ply, the at least two panes of glazing material including a first pane of glazing material and a second pane of glazing material, each of the first and second panes of glazing material having respectively a first major surface and an opposing second major surface, the laminated glazing being configured such that the second major surface of the first pane of glazing material faces the first major surface of the second pane of glazing material, an infrared reflecting film between the first and second panes of glazing material, the first major surface of the first pane of glazing material being an exposed surface of the laminated glazing such that light directed towards the first major surface of the first pane of glazing material at an angle of incidence of 60 to a normal on the first major surface of the first pane of glazing material is reflected off the laminated glazing to produce a first reflection, a second reflection and a third reflection, the first reflection being from light reflected from the first major surface of the first pane of glazing material, the second reflection being from light reflected from the second major surface of the second pane of glazing material and the third reflection being from light reflected from the infrared reflecting film, light intensity reducing means between the first major surface of the first pane of glazing material and the second major surface of the second pane of glazing material for reducing the intensity of the third reflection, such that upon directing a beam of electromagnetic radiation having an intensity I.sub.O at 770 nm toward the first major surface of the first pane of glazing material at an angle of incidence of 60 to a normal on the first major surface of the first pane of glazing material, and the intensity of the third reflection at a wavelength of 770 nm is less than or equal to 0.185I.sub.O.

48. A laminated glazing according to claim 47, wherein the light intensity reducing means is between the first major surface of the first pane of glazing material and the infrared reflecting film.

49. A laminated glazing according to claim 47, wherein intensity of the third reflection at 770 nm is less than or equal to I.sub.770 where I.sub.770=0.18I.sub.O or 0.17I.sub.O or 0.16I.sub.O or 0.15I.sub.O or 0.14I.sub.O or 0.13I.sub.O or 0.12I.sub.O, and/or wherein the beam of electromagnetic radiation has an intensity I.sub.O at a wavelength of 660 nm and the intensity of the third reflection at 660 nm is less than or equal to 0.13I.sub.O, and/or wherein the beam of electromagnetic radiation has an intensity I.sub.O at a wavelength of 750 nm and the intensity of the third reflection at 750 nm is less than or equal to 0.17I.sub.O.

50. A laminated glazing according to claim 47, wherein light intensity reducing means for reducing the intensity of the third reflection is provided by at least one of the first pane of glazing material, the second pane of glazing material, the interlayer structure or a further light absorbing glass sheet comprising one or more optical absorbers.

51. A laminated glazing according to claim 50, wherein the first pane of glazing material comprises iron oxide (Fe.sub.2O.sub.3).

52. A laminated glazing according to claim 47, further comprising a coating on the second major surface of the first pane of glazing material.

53. A laminated glazing according to claim 52, wherein the coating on second major surface of the first pane of glazing material comprises at least one light absorbing layer for reducing the intensity of the third reflection.

54. A laminated glazing according to claim 53, wherein the at least one light absorbing layer of the coating on the second major surface of the first pane of glazing material has a thickness between 0.1 nm and 5 nm, and/or wherein the at least one light absorbing layer of the coating on the second major surface of the first pane of glazing material comprises nichrome or an oxide or nitride of nichrome.

55. A laminated glazing according to claim 47, wherein the second pane of glazing material has an iron oxide (Fe.sub.2O.sub.3) content between 0.001% and 0.19% by weight Fe.sub.2O.sub.3.

56. A laminated glazing according to claim 47, further comprising a coating on the first major surface of the second pane of glazing material.

57. A laminated glazing according to claim 56, wherein the coating on the first major surface of the second pane of glazing material comprises at least one light absorbing layer for reducing the intensity of the third reflection.

58. A laminated glazing according to claim 57, wherein the at least one light absorbing layer of the coating on the first major surface of the second pane of glazing material comprises nichrome or an oxide or nitride of nichrome.

59. A laminated glazing according to claim 47, wherein the infrared reflecting film comprises at least one layer comprising silver or wherein the infrared reflecting film comprises at least one layer of silver, and/or wherein the infrared reflecting film comprises at least one layer of ZnSnOx, ZnO or ZnO:Al, and/or wherein the infrared reflecting film comprises a first layer comprising silver and a second layer comprising silver, the first layer comprising silver being between a first layer of ZnSnOx, ZnO or ZnO:Al and a second layer of ZnSnOx, ZnO or ZnO:Al, further wherein the second layer comprising silver is between the second layer of ZnSnOx, ZnO or ZnO:Al and a third layer of ZnSnOx, ZnO or ZnO:Al.

60. A laminated glazing according to claim 47, wherein the infrared reflecting film is on the second major surface of the first pane of glazing material or on the first major surface of the second pane of glazing material or wherein the infrared reflecting film is on a carrier ply.

61. A laminated glazing comprising at least two panes of glazing material joined by an interlayer structure comprising at least one adhesive ply, the at least two panes of glazing material including a first pane of glazing material and a second pane of glazing material, each of the first and second panes of glazing material having respectively a first major surface and an opposing major surface, the laminated glazing being configured such that the second major surface of the first pane of glazing material faces the first major surface of the second pane of glazing material, there being an infrared reflecting film between the first and second panes of glazing material, wherein the first major surface of the first pane of glazing material is an exposed surface of the laminated glazing such that light directed towards the first major surface of the first pane of glazing material at an angle of incidence is reflected off the laminated glazing to produce a first reflection, a second reflection and a third reflection, the first reflection being from light reflected from the first major surface of the first pane of glazing material, the second reflection being from light reflected from the second major surface of the second pane of glazing material and the third reflection being from light reflected from the infrared reflecting film, wherein the laminated glazing comprises between the first major surface of the first pane of glazing material and the second major surface of the second pane of glazing material light intensity reducing means for reducing the intensity of the third reflection.

62. A laminated glazing according to claim 61, wherein the light intensity reducing means is between the first major surface of the first pane of glazing material and the infrared reflecting film or wherein first pane of glazing material comprises absorbing means for reducing the intensity of the third reflection.

63. A laminated glazing according to claim 61, wherein at normal incidence the laminated glazing has a visible light transmission (CIE Illuminant A 10 degree observer) of greater than 70% or 71% A or 72% or 73% or 74% or 75%, and/or wherein at normal incidence the laminated glazing has a total transmitted solar (TTS % measured using ISO 13837:2008 Convention A with outside surface wind velocity of approximately 4 m/s) of less than 60%, and/or wherein at normal incidence the percentage of light reflected from the second major surface of the second pane of glazing material (CIE Illuminant D65 10 degree observer) is less than 12%, and/or wherein at normal incidence the light reflected from the second major surface of the second pane of glazing material (CIE Illuminant D65 10 degree observer) has an a* less than zero, and/or wherein at normal incidence the light reflected from the second major surface of the second pane of glazing material (CIE Illuminant D65 10 degree observer) has a b* less than zero.

64. A laminated glazing according to claim 61, wherein prior to being incorporated into the laminated glazing, the infrared reflecting film is on the first or second sheet of glazing material and the sheet resistance (/) of the infrared reflecting film is between 2 / and 4 /, and/or wherein in the laminated glazing, the infrared reflecting film is on the first or second sheet of glazing material and the sheet resistance (/) of the infrared reflecting film is between 2 / and 4 /.

65. Use of one or more optical absorber for reducing the intensity of a third reflection produced by a laminated glazing when an incident beam of light strikes an exposed surface of the laminated glazing, the laminated glazing comprising at least two panes of glazing material joined by an interlayer structure comprising at least one adhesive ply, the at least two panes of glazing material including a first pane of glazing material and a second pane of glazing material, each of the first and second panes of glazing material having respectively a first major surface and an opposing major surface, the laminated glazing being configured such that the second major surface of the first pane of glazing material faces the first major surface of the second pane of glazing material, there being an infrared reflecting film between the first and second panes of glazing material, wherein the first major surface of the first pane of glazing material is the exposed surface of the laminated glazing such that the beam of light directed towards the first major surface of the first pane of glazing material at an angle of incidence is reflected off the laminated glazing to produce a first reflection, a second reflection and the third reflection, the first reflection being from light reflected from the first major surface of the first pane of glazing material, the second reflection being from light reflected from the second major surface of the second pane of glazing material and the third reflection being from light reflected from the infrared reflecting film, wherein the optical absorber is between the first major surface of the first pane of glazing material and the second major surface of the second pane of glazing material, further wherein the optical absorber is selected from the list consisting of a tinted interlayer ply, a body tinted glazing pane and a coating layer.

66. Use according to claim 65, wherein the optical absorber is between the first major surface of the first pane of glazing material and the infrared reflecting film or wherein the optical absorber is a body tinted glazing pane comprising an iron oxide content between 0.15% and 2% by weight Fe.sub.2O.sub.3.

Description

[0226] The invention will now be described with reference to the following figures (not to scale) in which,

[0227] FIG. 1 shows a cross section through a laminated glazing such as a vehicle windscreen to indicate the light paths from a head up display illumination source;

[0228] FIG. 2 shows a cross section through a laminated glazing where reflection from a major surface has been supressed;

[0229] FIG. 3 shows a cross section through a single pane of glass where reflection from a major surface has been supressed;

[0230] FIG. 4 shows the spectral distribution of the third reflection between 600 nm and 800 nm from different laminated glazings determined using an incident beam at an angle of 60 to a normal on the glazing surface;

[0231] FIG. 5 shows the spectral distribution of the third reflection between 380 nm and 780 nm from different laminated glazings determined using an incident beam at an angle of 60 to a normal on the glazing surface;

[0232] FIG. 6 shows the spectral distribution of the third reflection between 600 nm and 800 nm from different laminated glazings determined using an s-polarised incident beam at an angle of 60 to a normal on the glazing surface; and

[0233] FIG. 7 shows the spectral distribution of the third reflection between 380 nm and 780 nm from different laminated glazings determined using an s-polarised incident beam at an angle of 60 to a normal on the glazing surface.

[0234] FIG. 1 shows a schematic cross section of a laminated glazing 1, for example a vehicle windscreen. The laminated glazing 1 comprises a first sheet of glass 3 and a second sheet of glass 5. Both glass sheets 3, 5 have a soda-lime-silica composition. Although in FIG. 1 the laminated glazing 1 is shown as being flat (or planar) in cross section, typically the laminated glazing 1 would have a convex outer surface (facing the sun) and an opposing concave inner surface. Glass bending processes are well known in the art for shaping a flat glass sheet, for example gravity sag bending or press bending between complementary bending members a heat softened glass sheet.

[0235] The first sheet of glass 3 is joined to the second sheet of glass 5 by an adhesive interlayer ply 7. In this example the adhesive interlayer material is PVB, but other adhesive interlayers materials are known in the art, for example ethylene vinyl acetate (EVA). The adhesive interlayer ply 7 is not tinted in the visible region, but may be. Instead of a single adhesive interlayer ply 7, there may be two or more adhesive interlayers plies, one or more of which may be tinted.

[0236] The first sheet of glass 3 is uncoated whereas the second sheet of glass 5 has an infrared reflecting film 9 on the major surface thereof facing the interlayer ply 7. In this example the interlayer ply 7 is in direct contact with the infrared reflecting film 9. The infrared reflecting film 9 may be deposited on the major surface of the second sheet of glass using atmospheric pressure chemical vapour deposition and/or magnetron sputtering. When the laminated glazing is curved as described above, the infrared reflecting film may be deposited before or after the glass bending process.

[0237] In this example the infrared reflecting film 9 is a multilayer coating comprising two silver layers.

[0238] A suitable layer configuration for the infrared reflecting film 9 is given in table 1.

[0239] Methods are known in the art for depositing the infrared reflecting film, see for example WO2009/001143A1, WO2010/073042A1, WO2012/007737A1, WO2012/110823A1 and WO2012/143704A1.

[0240] For example the infrared reflecting film of table 1 may be deposited using AC and/or DC magnetron sputtering devices, medium-frequency, pulsed DC, or bipolar pulsed DC sputtering being applied where appropriate.

[0241] Dielectric layers of an oxide of Zn and Sn (ZnSnOx, weight ratio Zn:Sn50:50) may be reactively sputtered from zinc-tin targets in an Ar/O.sub.2 sputter atmosphere. The weight ratio of Zn to Sn in a ZnSnOx layer may be between 40 and 60% by weight i.e. a ZnSnOx layer, weight ratio Zn:Sn40:60 and a ZnSnOx layer, weight ratio Zn:Sn60:40.

[0242] Layers of silver (Ag) may consist of essentially pure silver (Ag) and may be sputtered from silver targets in an Ar sputter atmosphere without any added oxygen and at a partial pressure of residual oxygen below 105 mbar.

[0243] Layers of Ti may be sputtered from titanium targets (99.9% purity) and act as a barrier layer for the silver layer beneath. As will be readily apparent, the layer of Ti so deposited may be oxidised upon depositing a subsequent layer thereon, such that the layer of Ti is oxidised to TiOx, where x may be about 2. TiO.sub.2 layers may be directly deposited using slightly substoichiometric conductive TiOx targets (where x is about 1.98) in a pure Ar sputter atmosphere without added oxygen.

[0244] Layers of ZnO:Al may be sputtered from conductive ZnOx:Al targets in a pure Ar sputter atmosphere, with or without low levels of added oxygen. ZnO:Al layers may also be sputtered from Al-doped Zn targets (with an Al content about 2 wt. %) in an Ar/O.sub.2 sputter atmosphere.

[0245] ZnOx layers may be sputtered from Zn targets in an Ar/O.sub.2 sputter atmosphere.

[0246] Suboxidic NiCrOx layers may be sputtered from Ni.sub.80Cr.sub.20 targets in an Ar/O.sub.2 sputter atmosphere.

[0247] Layers of SiOx may be deposited using a Si target containing up to 30 wt % Al.sub.2O.sub.3 so depositing an SiOx:Al layer, i.e. said SiOx layer may contain up to 15 wt % Al.sub.2O.sub.3.

[0248] The multilayer coating shown in table 1 was deposited on the major surface of the second glass sheet 5 using magnetron sputtering. As shown in table 1, there is a ZnSnOx layer adjacent the glass surface. Other example infrared reflecting films are provided in table 3, Samples 1-4. The infrared reflecting film in table 1 is also provided in table 3 for Sample 5.

[0249] In FIG. 1 the PVB interlayer ply 7 is not a wedged PVB interlayer, although the PVB interlayer may be a wedged PVB interlayer.

TABLE-US-00001 TABLE 1 Layer Layer thickness (nm) Glass ZnSnOx 28.3 ZnOx 5 Ag 8.4 Ti 1.1 ZnSnOx 83.1 ZnOx 5 Ag 11 Ti 1.1 ZnSnOx 40 SiOx 5.7

[0250] Using conventional nomenclature, the outer facing major surface 11 of the laminated glazing 1 (i.e. the major surface facing the sun) is known as surface one or simply S1. The opposing major surface of the second glass sheet 5 is surface two, or S2 of the laminated glazing 1. The major surface 13 of the sheet of first sheet of glass 3 is referred to as surface four, or S4 of the laminated glazing 1. The opposing major surface of the first glass sheet 3 is referred to as surface three, or S3 of the laminated glazing 1.

[0251] As is conventional in the art, when the laminated glazing 1 is a vehicle windscreen, the first sheet of glass 3 is usually known as the inner pane or the inner ply of the windscreen and the second sheet of glass 5 is usually known as the outer pane or the outer ply of the windscreen.

[0252] As is evident from FIG. 1, both major surfaces 11, 13 are exposed major surfaces.

[0253] The laminated glazing 1 may be manufactured using conventional laminating conditions using high temperature and pressure, for example subjecting the unlaminated stack of individual components to a temperature of about 100 C. to 150 C. and pressure of about 5 to 15 atmospheres.

[0254] FIG. 1 illustrates how three images may be observed when the laminated glazing is viewed in a horizontal direction with the laminated glazing 1 inclined at an angle 15 to the horizontal. This illustrates the situation when the laminated glazing 1 is installed as a windscreen in a vehicle, and the driver of the vehicle looks through the windscreen (i.e. laminated glazing 1) towards the road ahead.

[0255] Positioned below the laminated glazing 1 is a light source 17 configured to shine an incident beam of light 19 onto the major surface 13. The light source 17 may be part of a HUD system and may be a white light source. In this example the incident beam of light 19 is perpendicular to the horizontal (and is therefore vertical.

[0256] The incident beam of light 19 is at an angle 18 to a normal 20 on the major surface 13. Since the incident beam of light is vertical, the angle 15 to the horizontal is the same as the angle 18 to a normal on the glass surface 13.

[0257] The incident beam of light 19 strikes the major surface 13 and a percentage of the incident light beam is reflected off the major surface 13 as reflected beam 21 to give a first reflection. The reflected beam 21 is also at an angle 18 to the normal 20 on the glass surface 13.

[0258] As FIG. 1 illustrates, some of the incident beam of light 19 from the light source 17 is transmitted through the major surface 13 and gets refracted upon passing the air/glass boundary. Some of the incident beam of light is able to pass through the first glass sheet 3, the adhesive interlayer ply 7, the infrared reflecting film 9 and the glass sheet 5 to be reflected off the glass/air boundary (i.e. major surface 11) to emerge through the major surface 13 as reflected beam 23 to give a second reflection.

[0259] Some of the incident beam of light 19 from the light source 17 that passes through the first sheet of glass 3 and the adhesive interlayer ply 7 is reflected off the infrared reflecting film 9 to emerge through the major surface 13 as reflected beam 25 to give a third reflection.

[0260] An observer 27 positioned to view the glazing as illustrated will see three images, a first image 21 (often referred to as a primary image) due to light from the first reflected beam 21 (i.e. the first reflection), a second image 23 (often known as a secondary image) due to light from the second reflected beam 23 (i.e. the second reflection) and a third image 25 (often referred to as a tertiary image) due to light from the third reflected beam 25 (i.e. the third reflection).

[0261] It will be readily apparent that if there is no infrared reflecting film 9 between the first and second sheets of glass 3, 5, there will not be a third image 25.

[0262] The use of a wedged interlayer ply such as wedged PVB may bring the first and second images 21, 23 into coincidence but it is not possible to bring all three images 21, 23 and 25 into coincidence using a wedged interlayer ply instead of interlayer ply 7.

[0263] The first image 21 is usually the brightest and the first reflected beam 21 has a wavelength distribution essentially the same as the wavelength distribution of the incident light beam 19.

[0264] The wavelength distribution of the second and third reflected beams 23, 25 depends on the nature of the glass sheets, 3, 5, the adhesive interlayer ply 7 and the infrared reflecting film 9.

[0265] The three images (or two if a wedged interlayer ply is used) are distracting for the driver of the vehicle.

[0266] Whilst it may be possible to choose a suitable light source 17 in an attempt to minimise the visibility of the third image 25, it is particularly desirable to provide a laminated glazing that may be usable with different light sources, in particular different white light sources, having unknown spectral distributions.

[0267] In order to quantify the amount of reflection due to the reflection off the infrared reflecting film 9 (i.e. the spectral distribution intensity variation with wavelength of the absolute reflection of the third reflected beam 25), a commercially available double beam spectrophotometer was used to determine the intensity of the third reflection as a function of wavelength. In the tests carried out as described below, a CARY 7000 UMS spectrophotometer was used.

[0268] Using such a spectrophotometer allows a wavelength range to be scanned with a known intensity of incident electromagnetic radiation at each wavelength. The CARY 7000 UMS spectrophotometer allows a complete sample characterisation to be made, and allows absolute reflection measurements to be made at variable angles and polarization.

[0269] Before the CARY 7000 UMS spectrophotometer was used to make the absolute reflection measurements, a baseline was run for both p and s polarization states separately. The reference light source was provided by the spectrophotometer.

[0270] Each sample reflection measurement was then carried by measuring the p and s polarization states separately in reflection by using a polariser within the spectrophotometer at the required wavelength. The absolute reflection at a given wavelength was the mean average of the p and s polarization reflection measurements at that wavelength. That is:

R.sub..sup.A=(R.sub..sup.s+R.sub..sup.p)/2(1)

where
R.sub..sup.A=the absolute reflection at wavelength ;
R.sub..sup.s=the reflection measured at wavelength using s-polarised electromagnetic radiation; and
R.sub..sup.p=the reflection measured at wavelength using p-polarised electromagnetic radiation.

[0271] In accordance with the above, and with reference to FIG. 1, the absolute reflection spectrum of the laminated glazing 1 was determined by positioning the laminated glazing (or a portion thereof) in the sample housing of the spectrophotometer so that the angle of incidence to a normal on the sample surface was 60. The light reflected from the laminated glazing was then captured by the spectrophotometer to measure the p and s polarization states in reflection separately at discussed above. With reference to FIG. 1, essentially the light source 17 was that provided by the spectrophotometer and the observer 27 was the detector system provided by the spectrophotometer (shown as detector 29 in FIGS. 2 and 3).

[0272] Determining the absolute reflection spectrum from the laminated glazing 1 in this manner, and with reference to FIG. 1, the reflected light measured by the spectrophotometer will contain light from the first, second and third reflected beams 21, 23 and 25. This makes it very difficult to obtain the spectral distribution of each individual reflected beam 21, 23 and 25.

[0273] Accordingly the samples were treated before being measured to suppress the reflection from the major surface 11 of the second sheet of glass 5 i.e. the major surface of the laminated glazing opposite the major surface where the light was incident i.e. the surface intended to be surface one of the laminated glazing when installed in a vehicle was treated.

[0274] This reflection was suppressed by sand blasting the major surface 11 and/or painting the major surface 11 with black paint. The configuration of the CARY 7000 UMS spectrophotometer also meant that if there was still any reflection from the treated surface, the scattered light was not collected by the detector.

[0275] With the reflection from the major surface 11 of the second sheet of glass 5 in the laminated glazing 1 suppressed, the treated laminated glazing was again inserted into the sample housing of the spectrophotometer for measurement at an angle of incidence of 60 as before.

[0276] This is illustrated in FIG. 2 where the major surface 11 has been treated to suppress reflection therefrom, so is labelled as surface 11. Given that the second reflected beam 23 has now been suppressed the spectrophotometer measures light only from the first and third reflected beams 21 and 25 i.e. the detector 29 of the spectrophotometer measures the combined reflection from the beams 21, 25. Again the s and p polarisation states were measured in reflection separately.

[0277] In order to determine the spectral distribution of the first reflected beam 21, a single glass sheet 3 was measured in the spectrophotometer as before at an angle of incidence of 60 with the reflection from the back surface suppressed in the same way as described above. This is illustrated in FIG. 3 where the sand blasted surface of the glass sheet 3 is labelled as 13. In the configuration shown in FIG. 3, there is no reflection from the light source 17 off surface 13 towards the detector 29 from light that passes through the surface 13. Again the s and p polarisation states were measured in reflection separately.

[0278] With the configuration shown in FIG. 3, the spectral distribution of the first reflected beam 21 was obtained.

[0279] The variation of the absolute reflection as a function of wavelength of the third reflected beam 25 was then obtained as follows.

[0280] With reference to FIG. 2, the detector 29 measures the combined spectral distribution of the first and third reflected beams:

.sup.1R.sub..sup.s=SP1.sub..sup.s+SP3.sub..sup.s(2)

.sup.1R.sub..sup.p=SP1.sub..sup.p+SP3.sub..sup.p(3)

.sup.1R.sub..sup.A=(.sup.1R.sub..sup.s+.sup.1R.sub..sup.p)/2=(SP1.sub..sup.s+SP1.sub..sup.p+SP3.sub..sup.p+SP3.sub..sup.s)/2(4)

where
is the wavelength in nanometres;
.sup.1R.sub..sup.s is the reflection measurement at wavelength made by the spectrophotometer using s-polarised electromagnetic radiation;
.sup.1R.sub..sup.p is the reflection measurement at wavelength made by the spectrophotometer using p-polarised electromagnetic radiation;
SP1.sub..sup.s is the reflection at wavelength of the first reflected beam 21 under s-polarised electromagnetic radiation;
SP3.sub..sup.s is the reflection at wavelength of the third reflected beam 25 under s-polarised electromagnetic radiation;
SP1.sub..sup.p is the reflection at wavelength of the first reflected beam 21 under p-polarised electromagnetic radiation; and
SP3.sub..sup.p is the reflection at wavelength of the third reflected beam 25 under p-polarised electromagnetic radiation.

[0281] The absolute reflection .sup.1R.sub..sup.A at wavelength is given by equation (4) and is the mean average of the reflection measurements made using both s and p polarised electromagnetic radiation.

[0282] With reference to FIG. 3, another set of measurements were made using the spectrophotometer and detector 29 measures the reflection that is due only to the reflected beam 21:

.sup.2R.sub..sup.s=SP1.sub..sup.s(5)

.sup.2R.sub..sup.p=SP1.sub..sup.p(6)

.sup.2R.sub..sup.A=(.sup.2R.sub..sup.s+.sup.2R.sub..sup.p)/2=(SP1.sub..sup.s+SP1.sub..sup.p)/2(7)

where
is the wavelength in nanometres;
.sup.2R.sub..sup.s is the reflection measurement at wavelength made by the spectrophotometer using s-polarised electromagnetic radiation; and
.sup.2R.sub..sup.p is the reflection measurement at wavelength made by the spectrophotometer using p-polarised electromagnetic radiation.

[0283] The parameters SP1.sub..sup.s and SP1.sub..sup.p are as defined above. The absolute reflection .sup.2R.sub..sup.A is given by equation (7) and is the mean average of the reflection measurements made using both s and p polarised electromagnetic radiation.

[0284] To determine the spectral distribution with wavelength of the absolute reflection of the third reflected beam 25 (which with reference to equation (1) is (SP3.sub..sup.p+SP3.sub..sup.s)/2), it is possible to subtract the absolute reflection spectrum containing only the reflection information from the first reflected beam 21 away from the absolute reflection spectrum containing the combined reflection information from both the first reflected beam 21 and the third reflected beam 25. This will leave only the absolute reflection variation with wavelength of the third reflected beam 25. With reference to the above equations, this is equivalent to equation (4)equation (7):

(4)(7)=.sup.1R.sub..sup.A.sup.2R.sub..sup.A=(SP3.sub..sup.s+SP3.sub..sup.p)/2=.sup.3R.sub..sup.A(8)

where
.sup.3R.sub..sup.A is the absolute reflection at wavelength of the third reflected beam 25 due to reflection from the infrared reflecting film 9 in between the two sheets of glass 3, 5 of the laminated glazing 1.

[0285] It should be noted that the parameter .sup.3R.sub..sup.A is dependent upon the angle of incidence of the incident beam of electromagnetic radiation, which in the above was at an angle of 60 to a normal on the sample surface. Accordingly it may be convenient to refer to a parameter .sub.60.sup.3R.sub..sup.A where the subscript 60 refers to the angle of incidence (in degrees) of the incident beam of electromagnetic radiation to a normal on the sample surface.

[0286] With reference to FIG. 1, the infrared reflecting film 9 is configured to reflect infrared energy in the direction surface 2.fwdarw.surface 1 i.e. to prevent infrared energy passing into the vehicle in which the laminated glazing 1 is installed. As such for an incident beam of electromagnetic radiation at an angle of incidence of 60 to a normal on the sample surface, .sup.3R.sub..sup.A varies with wavelength over the visible part of the spectrum and over other selected wavelength regions, for example 600 nm to 800 nm as shown in FIG. 4.

[0287] A typical human eye is sensitive to wavelengths in the 380 nm to 780 nm range, so monitoring the amount of absolute reflection in the red end of the visible spectrum provides a useful guide to the intensity of the third image observable by a driver of a vehicle when the laminated glazing 1 is installed in a vehicle.

[0288] Using the approach described above a number of commercially available laminated glazings were measured with the Cary 7000 UMS spectrophotometer using an incident beam of electromagnetic radiation at an angle of incidence of 60 to a normal on the sample surface as described above and compared with different laminated glazings made in accordance with the present invention to determine the spectral distribution of the absolute reflection of the third reflected beam 25. The results are shown in FIG. 4 where the commercially available laminated glazings are denoted by Comp 1-6.

[0289] The laminated glazing Comp A was made to illustrate the difficulty in achieving good solar control properties (high visible light transmission and low TTS %) and is an example of a type of infrared reflecting film that is commercially available.

[0290] With reference to FIG. 1, the glass sheet 3 would be denoted as the inner pane and the glass sheet 5 would be denoted as the outer pane.

[0291] Samples 1-5 were made in accordance with the present invention.

TABLE-US-00002 TABLE 2 Sample Comp A 1 2 3 4 5 Inner pane glass Clear float Light Green Clear float Light Green Light Green Light Green type glass Float Glass glass Float Glass Float Glass Float Glass Inner pane 2.12 mm 2.09 mm 2.12 mm 2.1 mm 2.09 mm 2.09 mm thickness Outer pane Clear float Clear float Clear float Clear float Clear float Clear float glass type glass glass glass glass glass glass Outer pane 3.84 mm 3.86 mm 3.88 mm 3.85 mm 3.83 mm 3.83 mm thickness Interlayer ply PVB PVB PVB PVB PVB PVB type Interlayer ply 0.76 mm 0.76 mm 0.76 mm 0.76 mm 0.76 mm 0.76 mm thickness Position of Surface two Surface two Surface two Surface two Surface two Surface two infrared reflecting film

[0292] In all the samples in table 2, the infrared reflecting film was on the first major surface of the outer pane of glass and is therefore positioned in the laminated glazing as shown in FIG. 1 i.e. between major surface 11 and the adhesive interlayer ply 7 on the first major surface of the second glass sheet 5. As previously discussed, using conventional nomenclature this is surface two of the laminated glazing 1.

[0293] The individual layer type and thickness in nanometres (nm) and stack configuration of the infrared reflecting film 9 for each of the samples in table 2 was as shown in table 3. For the avoidance of doubt, with reference to FIG. 1, samples 1-5 each have the ZnSnOx layer highlighted in bold (also referred to as layer i) in direct contact with the glass sheet 5. Note that in Sample 2, the nichrome containing layer is a sub-stoichiometric oxide NiCrOx, although this layer may be a metal layer of NiCr or an oxide or nitride of nichrome with varying stoichiometry. As discussed above, a layer of Ti may be fully or partially oxidised (to TiOx) upon depositing a subsequent oxide layer thereon, such as a layer of ZnSnOx. Also as discussed above SiOx layers may contain Al.sub.2O.sub.3 up to 15% by weight (i.e. an SiOx:Al layer) depending upon the exact type of target used during sputtering.

[0294] In the above table 2 by Clear float glass, it is meant a glass having a composition as defined in BS EN 572 1 and BS EN 572-2 (2012). The total iron oxide content of the clear float glass was about 0.082% by weight Fe.sub.2O.sub.3 with a ferrous content expressed as Fe.sub.2O.sub.3 of 27.3%.

[0295] In the above table 2, by Light Green Float Glass it is meant a soda-lime-silica glass composition (i.e. float glass) having an iron oxide of 0.56% by weight Fe.sub.2O.sub.3 at a ferrous content expressed as Fe.sub.2O.sub.3 of 24.5%. As is known in the art, a tinted float glass composition is often made by adding the desired level of colourants on top of a clear float glass batch composition, or at the expense of silica in the glass composition. A clear float batch composition is used to make a clear float glass having a composition as defined in BS EN 572 1 and BS EN 572-2 (2012).

TABLE-US-00003 TABLE 3 Layer Sample Reference Comp A 1 2 3 4 5 GLASS ZnSnOx (nm) i 26.2 26.2 26.8 29.1 28.3 ZnOx (nm) ii 33.3 5 5 5 5 5 Ag (nm) iii 8.9 8.9 8.9 10 10.9 8.4 Ti (nm) iv 1.1 1.1 1.1 1.1 1.1 1.1 ZnSnOx (nm) v 82.4 79.7 79.8 80.5 83.1 ZnOx (nm) vi 76.4 5 5 5 5 5 Ag (nm) vii 11.6 11.6 11.6 11.7 8.6 11 Ti (nm) viii 1.1 1.1 1.1 1.1 1.1 NiCrOx (nm) ix 1.95 ZnSnOx (nm) x 39 32.4 36.8 32 40 ZnOx (nm) xi 23 SiOx (nm) xii 5.7 5.7 5.7 5.7 5.7 5.7

[0296] In table 3 each layer was deposited using magnetron sputtering as previously discussed with reference to the coating shown in table 1. Other vacuum deposition processes (i.e. which are usually performed at a pressure of lower than about 0.1 mbar) may be used to prepare the infrared reflecting film, for example sputtering, reactive sputtering, evaporation and other forms of physical vapour deposition.

[0297] In other examples similar to those shown in table 3, layer i and/or layer ii may be a layer of ZnO or ZnO:Al, where ZnO:Al is ZnO doped with Al.sub.2O.sub.3, typically at a level of about 3 wt % Al.sub.2O.sub.3.

[0298] In other examples similar to those shown in table 3, layer i and ii may be replaced by a single layer i*, the single layer i* being in direct contact with the glass sheet 5 on one side and the layer iii on the opposite side. The single layer i* may be ZnSnOx, ZnOx, ZnO or ZnO:Al, where ZnO:Al is ZnO doped with Al.sub.2O.sub.3, typically at a level of about 3 wt % Al.sub.2O.sub.3. Put another way, the layer i and layer ii may be the same material and may be ZnSnOx, ZnOx, ZnO or ZnO:Al, where ZnO:Al is ZnO doped with Al.sub.2O.sub.3, typically at a level of about 3 wt % Al.sub.2O.sub.3. As is evident from the above examples of a coated glass sheet, the infrared reflecting film may have a layer of ZnSnOx, ZnO or ZnO:Al in direct contact with the glass surface.

[0299] Also as is evident from the above examples of a coated glass sheet, the infrared reflecting film may have a first layer comprising silver (i.e. a first layer of silver) in between a first layer of ZnSnOx, ZnO or ZnO:Al and a second layer of ZnSnOx, ZnO or ZnO:Al, the first layer of ZnSnOx, ZnO or ZnO:Al being in direct contact with the glass surface.

[0300] Also as is evident from the above examples of a coated glass sheet, the infrared reflecting film may have a first layer comprising silver (i.e. a first layer of silver) and a second layer comprising silver (i.e. a second layer of silver), the first layer comprising silver being between a first layer of ZnSnOx, ZnO or ZnO:Al and a second layer of ZnSnOx, ZnO or ZnO:Al, the first layer of ZnSnOx, ZnO or ZnO:Al being in direct contact with the glass surface; and the second layer comprising silver being between the second layer of ZnSnOx, ZnO or ZnO:Al and a third layer of ZnSnOx, ZnO or ZnO:Al.

[0301] Also as is evident from the above examples of a coated glass sheet, the infrared reflecting film may have a layer of SiOx, where at least one layer comprising silver is between the glass and the layer of SiOx. It is preferred for the layer of SiOx to be an outermost layer of the infrared reflecting film, for example there may be no other coating layer on the SiOx layer.

[0302] Also as discussed previously, a layer of SiOx may be deposited using a Si target containing up to 30 wt % Al.sub.2O.sub.3 such that an SiOx:Al layer is deposited that may contain up to 15 wt % Al.sub.2O.sub.3.

[0303] In addition to making measurements of the spectral distribution of the third reflected beam as described above, conventional normal incidence transmission and reflection measurements were also made for each laminated glazing and the results are shown in table 4. These properties for three other commercially available laminated glazings are provided and labelled as Comp 7-9.

[0304] The column headed Tvis (%) in table 4 shows values of visible light transmission (CIE Illuminant A 10 degree observer).

[0305] The column headed Rext vis (%) in table 4 shows values of the reflection according to ISO 9050:2003 from surface 1 of the glazing i.e. with reference to FIG. 1, the reflection of visible light from major surface 11.

[0306] The columns headed Rext a* and Rext b* in table 4 are values of the reflected colour from surface 1 of the glazing (Illuminant D65 10 degree observer) i.e. with reference to FIG. 1, the reflected colour from major surface 11.

[0307] The column headed TTS (%) in table 4 shows the total transmitted solar values calculated in accordance with ISO 13837:2008 Convention A with outside wind velocity .sub.1 of approximately 4 m/s as specified in Appendix B, section B.2 of said standard.

[0308] The column headed Sheet Resistance (/) in table 4 is the sheet resistance of the coated glass sheet (coating side) prior to being incorporated into the laminated glazing. Instruments to make such sheet resistance measurements are commercially available, see for example NAGY, Messsysteme GmbH, Siedlerstr. 34, 71126 Gufelden, Germany.

[0309] Sheet resistance may be an important parameter when the laminated glazing is to be used as a vehicle windscreen wherein the electrically conductive coating that reduces the amount of infrared energy entering the vehicle cabin in which the laminated glazing is installed may also be used to provide a heatable glazing function to reduce misting of the windscreen.

TABLE-US-00004 TABLE 4 Sheet Thickness Tvis Rext vis Rext Rext TTS resistance Sample (mm) (%) (%) a* b* (%) (/) Comp A 6.74 72.44 11.3 7.58 4.25 46.94 3.21 1 6.69 72.19 9.79 3.44 7.98 46.96 3.07 2 6.76 72.59 9.31 3.49 6.89 49.8 3.11 3 6.71 73.07 9.56 3.26 10.81 45.5 2.88 4 6.68 73.11 8.92 2.12 1.1 48.4 3.04 5 6.68 73.99 8.92 1.31 5.15 49.2 3.15 Comp 1 5.4 77.2 11.1 7 2.7 52.8 2.7 Comp 2 4.44 70.8 11.5 12 20.6 34.9 0.7 Comp 3 4.99 79.2 11.4 7.2 1.4 53.4 2.5 Comp 4 4.75 74.5 9.8 3.8 2.7 51.8 3.6 Comp 5 4.5 73.5 8.8 3.22 5.11 51.2 4.1 Comp 6 4.44 72.3 11.2 3.5 1.2 40.5 0.9 Comp 7 4.46 78.4 9.6 3.9 3.6 55.5 5 Comp 8 4.46 70.8 10.4 4.7 4.7 46.3 3.2 Comp 9 4.46 77 9.9 5 5 50.4 3.2

[0310] The values of the absolute reflection .sup.3R.sub..sup.A for the third reflected beam as a function of wavelength from the laminated glazings determined as described above (i.e. at an angle of incidence of 60 to a normal on the first major surface of the first pane of glazing material, using a double beam spectrophotometer and equations 1-8) are illustrated in FIG. 4 over the wavelength region 600-800 nm and in FIG. 5 over the wavelength region 380-780 nm. Specific absolute reflection values .sup.3R.sub..sup.A for the third reflection (in %) at certain wavelengths taken from FIG. 4 and FIG. 5 are given in table 5.

TABLE-US-00005 TABLE 5 Absolute value of reflection of the third reflected beam (%) at wavelength: 660 nm 750 nm 770 nm 800 nm Sample (.sup.3R.sub.660.sup.A) (.sup.3R.sub.750.sup.A) (.sup.3R.sub.770.sup.A) (.sup.3R.sub.800.sup.A) Comp A 13.39 31.48 34.84 39.11 1 4.75 11.75 12.80 13.84 2 2.73 14.81 18.35 23.60 3 4.47 12.99 14.06 15.04 4 2.54 8.29 9.37 10.62 5 3.36 8.38 9.36 10.55 Comp 1 2.98 18.72 23.15 29.60 Comp 2 47.33 73.27 74.87 76.30 Comp 3 3.54 18.52 22.56 28.35 Comp 4 6.07 20.42 23.9 28.88 Comp 5 4.67 16.18 19.03 23.13 Comp 6 22.49 58.66 62.14 65.46

[0311] With reference to FIG. 4 and the above tables, it can be seen that Sample 1, which has a light green float glass inner pane and a clear float glass outer pane, has a much reduced value of the absolute reflection .sup.3R.sub..sup.A for the third reflected beam at 770 nm compared to sample Comp A (12.8% for Sample 1 compared to 34.84% for Comp A). Note that sample Comp A has both inner and outer panes of clear float glass.

[0312] With reference to the FIG. 4 and table 5, at 770 nm Sample 1 has an absolute reflection .sup.3R.sub..sup.A of 12.80%, meaning that compared to the reference beam at 770 nm, the intensity of the third reflection determined according to the above (see also equations 1-8) at 770 nm is 0.1280I.sub.O, where I.sub.O is the intensity of the reference beam at 770 nm. That is, the absolute reflection .sup.3R.sub..sup.A of the third reflected beam at 770 nm is 12.80%.

[0313] Sample 2, which has both the inner and outer panes of clear float glass, has an infrared reflecting film on surface 2 comprising a layer of NiCrOx. As seen from FIG. 4, the NiCrOx layer of Sample 2 reduces the intensity of the absolute reflection of the third reflected beam compared to the sample Comp A, but not to the same extent as for Sample 1. The intensity of the third reflected beam may be further reduced by using a thicker NiCrOx layer.

[0314] Sample 3 is similar to Sample 1 and has acceptable Tvis (%) and TTS (%) for use as a vehicle windscreen.

[0315] Sample 4 has a more neutral colour in reflection from surface 1 of the laminated glazing which may be more desirable in certain applications.

[0316] Sample 5 has a similar intensity of the absolute reflection of the third reflected beam third compared to Sample 4. That is, for Sample 5 the absolute reflection of the third reflected beam at 770 nm is 9.36% compared to 9.37% for Sample 4.

[0317] As discussed above Samples 1, 3, 4 and 5 have the inner pane (i.e. glass sheet 3) of the laminated glazing as a sheet of soda-lime-silica glass containing 0.56% by weight iron oxide (Fe.sub.2O.sub.3) and the outer pane (i.e. glass sheet 5) as a sheet of clear float glass containing about 0.082% by weight iron oxide (Fe.sub.2O.sub.3), although it is preferred for the content of iron oxide in the outer pane to be lower i.e. 0.001-0.07% by weight Fe.sub.2O.sub.3. The outer pane may have an iron oxide content in the region 0.001-0.15% by weight Fe.sub.2O.sub.3 or 0.001-0.12% by weight Fe.sub.2O.sub.3.

[0318] The percentage of ferrous iron (expressed as Fe.sub.2O.sub.3) in the glass of the inner pane is preferably between 20% and 30% i.e. the glass of the inner pane comprises between 0.20.56=0.112 wt % ferrous iron expressed as Fe.sub.2O.sub.3 and 0.30.56=0.168 wt % ferrous iron expressed as Fe.sub.2O.sub.3.

[0319] With reference to FIG. 1, the iron oxide content in the inner pane (i.e. sheet of glass 3) provides the laminated glazing 1 with means to reduce the intensity of the third reflected beam 25. Furthermore, the colour of the third reflection i.e. third image 25 may become more neutral compared to the laminated glazing having an inner pane of clear float glass.

[0320] In Sample 2 both the inner and outer panes of glass were clear float glass having an iron oxide (Fe.sub.2O.sub.3) content of about 0.0.082% by weight. With reference to FIG. 1, Sample 2 has an infrared reflecting film 9 having a 1.95 nm thick sub stoichiometric nichrome oxide layer to help selectively absorb the third reflected beam 25, thereby reducing the intensity of the third image 25 viewable by an observer.

[0321] A laminated glazing according to the present invention finds particular application as a vehicle windscreen, where the vehicle windscreen may be used as a combiner in a head up display system. In such a head up display (HUD) system it may be desirable to use an optical system that has a light source having a particular polarisation state, for example the light source of the optical system of the HUD may be s-polarised or p-polarised.

[0322] As is known in the art, the amount of specular reflection from a glass surface is a function of the angle of incidence and the polarisation state of the incident beam. For example, at an air/glass interface, at the Brewster angle an incident beam of p-polarised light has zero reflection and is fully refracted through the glass. In contrast, for an incident beam of s-polarised light at the Brewster angle, the reflectivity is not zero and an amount of the incident beam is reflected.

[0323] The Brewster angle .sub.p (often known as the polarizing angle in the art) is defined by:

[00001]$\begin{array}{cc}\tan .Math..Math.{}_p=\frac{n_2}{n_1}& \left(9\right)\end{array}$

where .sub.p is measured relative to a normal on the surface of the medium having the refractive index n.sub.2 i.e. a normal on a glass surface.

[0324] In the case of an incident beam travelling from air to glass, n.sub.2 is the refractive index of glass and n.sub.1 is the refractive index of air.

[0325] For example, a soda-lime-silica glass has a refractive index (=n.sub.2) of 1.52 at 540 nm and the refractive index of air (=n.sub.1) at 540 nm is 1.00. Using equation (9) above .sub.p is about 56.7 to a normal on the glass surface. As such, for an incident beam of unpolarised light at an angle of incidence of 60 to a normal on the glass surface, the amount of p-polarised light that is reflected is very low (because the angle of incidence is close to the Brewster angle) and the reflection from the glass surface may be considered to be essentially only s-polarised light.

[0326] With reference to equations (2) and (5) above, when an incident beam of s-polarised light is used,

.sup.1R.sub..sup.s=SP1.sub..sup.s+SP3.sub..sup.s(2)

.sup.2R.sub..sup.s=SP1.sub..sup.s(5)

[0327] Hence, using equations (2) and (5) it is possible to isolate SP3.sub..sup.s (the reflection at wavelength of the third reflected beam 25 under s-polarised electromagnetic radiation), see equation (10) below:

(2)(5)=.sup.1R.sub..sup.s.sup.2R.sub..sup.s=SP3.sub..sup.s(10)

[0328] As before, SP3.sub..sup.s is the reflection at wavelength of the third reflected beam 25 under s-polarised electromagnetic radiation.

[0329] FIG. 6 is a graph showing the variation with wavelength between 600 nm and 800 nm of the reflected intensity of the third reflected beam using an incident beam of s-polarised electromagnetic radiation at an angle of incidence of 60 to a normal on the glass surface i.e. FIG. 6 shows the parameter SP3.sub..sup.s as described above and calculated using equation (10). As expected there are strong similarities between the data presented in FIGS. 4 and 6 because the angle of incidence is close to the Brewster angle.

[0330] The values of the SP3.sub..sup.s parameter at 660 nm, 750 nm, 770 nm and 800 nm are provided in table 6 for an incident beam of s-polarised electromagnetic radiation at an angle of incidence of 60 to a normal on the glass surface.

TABLE-US-00006 TABLE 6 Value of reflection of the third reflected beam (%) at wavelength: (using s-polarised beam at angle of incidence of 60 to a normal on the glass surface) 660 nm 750 nm 770 nm 800 nm Sample (SP3.sub.660.sup.s) (SP3.sub.750.sup.s) (SP3.sub.770.sup.s) (SP3.sub.800.sup.s) Comp A 12.91 31.05 34.25 38.16 2 1.53 13.16 16.74 22.03 3 3.27 11.72 12.74 13.6 Comp 1 2.37 18.11 22.59 29.00 Comp 2 51.26 67.42 68.32 69.08 Comp 3 2.27 17.47 21.62 27.5 Comp 4 4.75 19 22.52 27.5 Comp 5 3.77 15.23 18.10 22.22 Comp 6 29.59 56.38 58.47 60.35

[0331] FIG. 7 is a similar to FIG. 6 and is a graph showing the variation with wavelength between 380 nm and 780 nm of the reflected intensity of the third reflected beam using an incident beam of s-polarised electromagnetic radiation at an angle of incidence of 60 to a normal on the glass surface. Again as expected, there are similarities with the data presented in FIGS. 5 and 7 because the angle of incidence is close to the Brewster angle.

[0332] The present invention provides a laminated glazing for use as a windscreen. The windscreen may be used as a combiner in a head up display system. In comparison to known laminated windscreens having an infrared reflecting film between the inner and outer glass panes, embodiments of the present invention have lower absolute reflection at 770 nm which translates to a reduced intensity third image being seen by the driver of the vehicle.