LAMINATED GLAZING

Abstract

An automotive rear window glazing for installation in a car, comprises at least two plies of glazing material and at least one ply of plastics interlayer material extending between the plies of glazing material, the ply of plastics interlayer material being substantially co-extensive with the plies of glazing material and bonding the plies of glazing material to each other, wherein the ply of plastics interlayer material contains draw lines extending in substantially one direction, the automotive rear window glazing has a top edge and a bottom edge, and wherein the automotive rear window glazing is installed with the draw lines in the plastics interlayer material extending from the top to the bottom edges.

Claims

1. An automotive rear window glazing for installation in a car, comprising at least two plies of glazing material and at least one ply of plastics interlayer material extending between the plies of glazing material, the ply of plastics interlayer material being substantially co-extensive with the plies of glazing material and bonding the plies of glazing material to each other, wherein the ply of plastics interlayer material contains draw lines extending in substantially one direction, the automotive rear window glazing has a top edge and a bottom edge, and wherein the automotive rear window glazing is installed with the draw lines in the plastics interlayer material extending from the top to the bottom edges.

2. An automotive rear window glazing as claimed in claim 1, wherein one or both of the plies of glazing material contains draw lines and the draw lines in the plies of glazing material are substantially parallel to the draw lines in the ply of plastics interlayer material.

3. An automotive rear window glazing as claimed in claim 1, wherein the installation angle of the glazing is 65° or greater.

4. An automotive rear window glazing as claimed in claim 1, wherein the installation angle of the glazing is 68° or greater.

5. An automotive rear window glazing as claimed in claim 1, wherein the installation angle of the glazing is 72° or greater.

6. An automotive rear window glazing as claimed in claim 1, wherein the installation angle of the glazing is 75° or greater.

7. An automotive rear window glazing as claimed in claim 1, wherein the installation angle of the glazing is 78° or greater.

8. An automotive rear window glazing as claimed in claim 1, wherein the thickness of at least one of the plies of glazing material is in the range from 0.4 to 1.3 mm.

9. An automotive rear window glazing as claimed in claim 1, wherein the thickness of at least one of the plies of glazing material is in the range from 0.5 to 1.1 mm.

10. An automotive rear window glazing as claimed in claim 1, wherein the thickness of at least one of the plies of glazing material is in the range from 0.6 to 0.9 mm.

11. An automotive rear window glazing as claimed in claim 1, wherein at least one of the plies of glazing material is glass which has been chemically toughened.

12. An automotive rear window glazing as claimed in claim 1, wherein the wavelength of the draw lines is 50 mm or greater.

13. An automotive rear window glazing as claimed in claim 1, wherein the wavelength of the draw lines is 80 mm or greater.

14. An automotive rear window glazing as claimed in claim 1, wherein the wavelength of the draw lines is 120 mm or greater.

15. A car fitted with an automotive rear window glazing as claimed in claim 1.

16. A high performance car fitted with an automotive rear window glazing as claimed in claim 1.

Description

[0040] The invention will now be further described by way of the following non-limiting specific embodiments, which are illustrated with reference to the accompanying drawings in which:

[0041] FIG. 1 is a schematic plan view of an automotive rear window glazing;

[0042] FIG. 2 is a sectional view taken along the line A-A in FIG. 1, showing part of the automotive rear window glazing, greatly enlarged;

[0043] FIG. 3 is a diagram showing the installation angle of an automotive rear window glazing, the glazing being shown in section;

[0044] FIG. 4 is a schematic combined perspective and sectional view of a sheet of plastics interlayer material.

[0045] Referring to FIG. 1, a schematic plan view of an automotive rear window glazing 10 is shown. The glazing has a top edge 11, a bottom edge 12, and side edges 13 and 14. The shape of the glazing shown is purely schematic, and rear window glazings may have a variety of shapes other than that shown. In general, however, the shape of a rear window glazing is very loosely based on a trapezium, rectangle or square, but with curved edges and corners.

[0046] FIG. 2 is a sectional view taken along the line A-A in FIG. 1, showing the upper part of the automotive rear window glazing, greatly enlarged. As stated above, the glazing is a laminated glazing, comprising first and second plies of glass 20, 21, with a ply of plastics interlayer material 22 (hereafter termed “interlayer” for brevity) extending between the plies of glass and bonding them together.

[0047] Automotive glazings are normally curved, with the convex surface facing the exterior, and the concave surface facing the interior of the vehicle. In the automotive industry, it is conventional to number the surfaces of the plies 1, 2, 3, 4, starting from the exterior surface. Accordingly the first ply 20 is the exterior ply, having surfaces 1 and 2, and the second ply 21 is the interior ply, having surfaces 3 and 4. In this specification, “interior” is used to denote the interior of the vehicle, and not the inside of the laminate.

[0048] The laminated glazing is manufactured in three steps: first the plies are assembled, then the assembly is de-aired, and finally the assembly is heated in an autoclave to bond the plies together to form a laminate. Accordingly, first the ply of plastics interlayer material is placed between the plies of glass so that it is in register with them, i.e. co-extensive with them, and then air is removed from the assembly by passing it between nip-rollers or by use of a vacuum bag. The de-aired assembly is then placed in an autoclave and subjected to an elevated temperature and pressure to cause the interlayer material to bond to the glass, thereby bonding the plies of glass together and forming a laminate.

[0049] The maximum temperature attained in the autoclave may be between 125° C. and 150° C., preferably 140° C., and the maximum pressure may be between 8 and 15 bars (between 0.8 and 1.5 MPa), preferably 12 bars (1.2 MPa). These conditions may be sustained for between 15 and 45 minutes, preferably around 30 minutes. The total autoclave cycle including heating and pressurisation may take around 90 minutes.

[0050] The interlayer material softens and flows while the glazing is in the autoclave, and it had previously been thought that any unevenness in the thickness of the interlayer material would dissipate during autoclaving, with the consequence that the draw lines would disappear. However, it has been found that this is not the case, and it is now believed that the wavelength of the draw lines is too large for the differences in thickness to homogenise during the time available during the autoclave cycle. Furthermore, extending the length of the autoclave cycle for the purpose of reducing the amplitude of the draw lines would not only add to costs, but it is also believed that as the interlayer material flows, distortion due to unevenness in the glass would be accentuated.

[0051] It should be noted that FIG. 2 is also schematic in nature. In particular, although the plies are shown as being of approximately equal thickness, normally at least one and possibly both plies of glass may be thicker than the interlayer. The plies of glass may range from 1.6 to 2.9 mm in thickness; alternatively, one of the plies of glass may be less than 1.5 mm in thickness, preferably in the range from 0.4 to 1.3 mm. When one of the plies is composed of chemically toughened glass, its thickness will normally be in the range from 0.4 to 1.3 mm, preferably 0.5 to 1.1 mm. If present, the chemically toughened ply is likely to be the inner ply.

[0052] FIG. 3 is a diagram showing the installation angle of the automotive rear window glazing, the glazing being shown in section. A tangent 30 is drawn to the glazing 10 in its installed condition, and the angle to the vertical 31 is measured, this being the installation angle 32.

[0053] FIG. 4 is a schematic combined perspective and sectional view of a sheet of plastics interlayer material 22, showing elongate peaks 40 and troughs 41 which extend in one direction, i.e. they all extend in a single direction. The peaks and troughs are therefore parallel to each other, as are the resulting draw lines in a laminated glass made with the interlayer.

[0054] It should be noted that FIG. 4 is purely diagrammatic, and shows the amplitude of the peaks and troughs greatly exaggerated, and the wavelength greatly compressed. The wavelength of the peaks and troughs is shown on the sectional part of FIG. 4, denoted by reference numeral 42.

[0055] Referring again to FIG. 1, when the glazing 10 is viewed in appropriate lighting conditions, such as a shadowgraph, transmitted optical distortion in the form of a pattern of faint parallel lines 15 may be seen extending from the top edge 11 to the bottom edge 12 (or vice versa, as will be clear). As previously mentioned, the lines 15 comprise alternating lines of relative brightness and darkness resulting from the localised refractive power of the laminated glazing, due to the elongate peaks and troughs in the interlayer. These alternating lines are the draw lines previously referred to. It is not possible to represent draw lines faithfully in a line drawing, and so dashed lines have been used in the absence of a better alternative.

[0056] The magnitude and extent of transmitted optical distortion may be accurately and quantitatively measured using equipment available from ISRA Vision AG, of Industriestrasse 14, D-64297 Darmstadt, Germany.

[0057] Such equipment may be used to evaluate the optical quality of a rear window glazing in the laboratory, and detect the degree of distortion present. However, as a consequence of the invention, this distortion is barely visible to the occupants of a vehicle in which a rear window glazing according to the invention is fitted.