GB2535561A

GB2535561A - Optical effects in transparent materials

Info

Publication number: GB2535561A
Application number: GB1515283.8A
Authority: GB
Inventors: Behrens Steven
Original assignee: CRYSTAL CLEAR JEWELLERY Ltd
Current assignee: CRYSTAL CLEAR JEWELLERY Ltd
Priority date: 2014-12-08
Filing date: 2015-08-28
Publication date: 2016-08-24
Also published as: GB2533182A; GB201521596D0; GB2533097A; GB201421823D0; WO2016092288A1; GB2535292A; GB201515283D0; GB201512811D0

Abstract

A pavé effect article made of glass which at least in part comprises substantially parallel front and back faces 12,13, the back face comprising a relief pattern of close packed projections 14 with parallel sides, the front face being unfaceted, the projections comprising even numbers of sides with an apex angle between 80° and 100°. The projections may be pyramids or prisms. The article may be an item of glassware such as a tumbler, stemmed glass, carafe, jug or decanter, or an item of jewellery. The faceting on the base may be in a design such as a circle, or more complex shapes. The faceting may be effected by cutting and polishing, etching, or moulding.

Description

Optical Effects in Transparent Materials This invention relates to optical effects in transparent materials.

Pave effects in jewellery are conventionally done by mounting individual gemstones in close array. By 'gemstones' is meant precious and semiprecious cut stones, which comprise a crown, a girdle, by which they are retained in a setting, and a pavilion. Glass crystal, or flint or lead glass is also used to emulate precious stones, a prime example of this being Swarovski ® jewellery and objets d'art.

Glass crystal or flint or lead glass is also used for glassware such as tumblers and stemware, as well as carafes and jugs, and patterns are cut into the glass, or, in many cases, moulded in.

Waterford® glass has a distinctive pave pattern of faceted gemstone-like pyramids. Much crystal glassware has a cut star pattern in the base of a tumbler or the foot of a stemmed glass.

Pave designs sparkle, with 'fire' -reds, greens and blues from the visible spectrum -by virtue of refraction and dispersion of light internally of the stone, and by reflection from the facets. Monolithic pave designs in glass are cut or moulded in the outer face -the 'technical front' -of the tumbler, jug, carafe, decanter or the like, simulating assembled pave designs. It would, of course, be difficult to cut such designs on the inner surfaces of such glassware, where it would not, in any event, give the required simulation of assembled pave designs.

Generally speaking, best effects are had from materials with high refractive indices and high dispersions. The refractive index of diamond is 2.42, that of cubic zirconia (CZ) 2.15 (though CZ has a higher dispersion than diamond), flint glass typically 1,62. These different refractive indices give different degrees of sparkle and fire.

It has now been found that monolithic pave effect articles can have an unexpected brilliance when viewed from the technical back, i.e. from the smooth, unfaceted face. Provided the faceting meets certain requirements, the effect is due to retroreflection, the result of total internal reflection off two internal surfaces of the faceting of light incident on the unfaceted face.

The effect is not dependent on refractive index, provided only that the refractive index is above about 1.42, which is true for all glasses and most plastics. The invention provides novel glassware and, generally, articles made of glass which have this brilliance.

The invention comprises a pave effect article made of glass which at least in part comprises substantially parallel front and back faces, the back face comprising a relief pattern of close packed projections with parallel sides, the front face being unfaceted, the projections comprising even numbers of sides with an apex angle between 80° and 100°.

The number of sides of each projection may be two, in which case the projections will comprise prisms -an unusual pave design, perhaps, but well within the definition, "a setting of stones placed close together so as to show no metal between them", the 'stones' in this case being prismatic rather than conventional gemstones. The number of sides may be four, in which case the projections will be pyramids -six or eight faceted pyramids would work, but would be more difficult to make.

The projections may be parallel, or at least substantially so. Where the projections are prisms, parallel projections on the bottom of a tumbler are, of course, quite different from the conventional cut star pattern found on the bottoms of crystal tumblers or the feet of stemware, with grooves radiating from a central point. The radiating grooves, which themselves have an included angle far more obtuse than the grooves that define the projections of the present invention, do not define prisms between them and the spacing between them increases as they radiate away from the centre.

The projections thus may be parallel prisms or parallel arrays of pyramids, or may be concentric annuli, or even spiral, which approximates to parallel for present purposes.

The effect aimed at is to get a substantial extent of retroreflection through total internal reflection of the faces of the projections -light entering through the front face and incident internally on one face of a projection being totally internally reflected on to the opposite face, there to be again totally internally reflected back out of the front face.

The front face is, of course, the face from which the article is viewed, and is the technical back, as referred to above.

The apex angle may be between 89° and 91° -desirably as close to 90° as possible for maximum brilliance. The article may be any conventional article of glass that affords the substantially parallel front and back faces. Thus an article of glassware, such as a tumbler, stemmed glass, carafe, jug or decanter will have a base which will normally be viewed, when the article is standing on it, from above. If the upper face of the base is unfaceted, the lower face faceted, the faceted area will appear brilliant because of the light incident on the upper face being retroreflected towards the viewer.

The whole of the base may be faceted, or just a part of it, which may be in a design such as a circle, an ellipse, crossed ellipses, a square, a triangle, a star, a heart shape, or more complex shapes such as company or club logos, animals, flowers, indeed, any shape that can be devised that will permit of being realised in the faceting.

The faceting may be effected in any appropriate size, for example with a spacing between apexes of 3.5 mm, 2.7 mm, 2.1 mm or less, emulating micropave designs. Where the article rests on its base, it may be desirable that the points of the faceting are elevated, and the 30 faceting may be done, then, within a rim, or the base may be concave to that end.

The front face may be flat or it may have a shallow convex or concave curvature. By shallow' is meant the depth at the centre, for a convex surface is no more than twice the average depth, and for a concave surface, the depth at the centre is greater than half the average depth. And 'substantially parallel' does not exclude that one face may be flat while the other is curved or that they may be oppositely curved.

By 'close packed' is meant contiguous or substantially so, with gaps between the bases of the pyramids less than one fifth the pyramid base length. Preferably, for maximum retroreflection there should the no gap at all. Nor, again, for maximum brilliance, should the projections be truncated, though tiny culets may militate against wear of or damage to or by points.

As mentioned above, pave effects in jewellery are effected by assembling individual stones. In common with otherjewellery comprising gemstones, the crowns of the stones are exposed on the outer or front face. GB2492225 discloses the production of pave jewellery by punching, machining or otherwise working the outer face of a workpiece, or by an additive process such as 3D printing, but, again, to put the relief pattern on the face.

When the pave effect is in transparent gemstones or in glass crystal, the gemstone crowns are on the front face, and they will, depending on the direction of incident light, reflect light from their facets or allow it to pass into the gemstone undergoing refraction and dispersion, and some, but by no means all, of the light will be totally internally reflected to emerge from one or other of the front face facets, where it will be further refracted and dispersed -a discussion of this is to be found in 11S2015/0201720, D. Swarovski AG.

By contrast, in pave effect glass crystal jewellery according to the present invention, the front face is unfaceted, so that, with light incident from behind the viewer there is substantially no front face reflection away from the viewer, the majority of the light passing straight through substantially without refraction or dispersion to be totally internally reflected off opposite faces of the rear face faceting to be retroreflected back towards the viewer for maximum brilliance.

The faceting may be effected by cutting and polishing, etching, or by moulding.

Glass pave effect articles according to the invention will now be described with reference to the accompanying drawings, in which: Figure 1 is a side elevation of a tumbler; Figure 2 is a view in the direction of Arrow 2 on Figure 1; Figure 3 is a side elevation of a stemmed glass; Figure 4 is a view in the direction of Arrow 4 of Figure 3; Figure 5 is a part section through the base of a conventionally star cut glass, showing light paths; Figure 6 is a part section like Figure 5 of a cut glass base of a glass like those of Figures 1 to 4; Figure 7 is a side elevation of a bracelet with a pave appliqué; Figure 8 is a view on Arrow 8 of Figure 7, to a larger scale; Figure 9 is a section through the pave section of the bracelet of Figures 6 and 7, with a

prior art pave appliqué;

Figure 10 is a section like Figure 9 with a pave appliqué according to the invention Figure 11 is a view of the base of a second embodiment of stemmed glass with a different pave design; Figure 12 is a section on the line 12-12 of Figure 11; and Figure 13 is a view like Figure 11 of the base of a third embodiment of stemmed glass with a further pave design.

The drawings illustrate pave effect articles 11 made of glass which at least in part comprise substantially parallel front 12 and back 13 faces, the back face 13 comprising a relief pattern of faceted projections 14, the front face 12 being unfaceted, the faceted projections 14 comprising close packed right pyramids with even numbers of sides with an apex angle between 80° and 100°.

The front face 12 is, of course, the face from which the article 11 is viewed, and is the technical back, as referred to above. Thus the front face 12 of the tumbler illustrated in Figures 1 and 2 is the upper or inner surface of the base of the tumbler as will be viewed from above when the tumbler is on a table or when it is raised for drinking. The retroreflective effect will be but little affected by the presence of liquid in the tumbler, as the faces involved in total internal reflection will not be in the liquid.

The front face 12 of the stemmed glass 11 illust4ated in Figures 3 and 4 is the upper face of the foot of the glass, which will likewise be seen when the glass is on a table or raised for drinking The apex angle can be between 89° and 91 -desirably as close to 90° as possible for maximum brilliance. The number of sides of the pyramidal projections 14 illustrated is four -six or eight would work, but would be more difficult to make.

The article 11 can be any conventional article of glass that affords the substantially parallel front and back faces 12, 13. Thus an article of glassware, such as a tumbler, stemmed glass, carafe, jug or decanter will have a base which will normally be viewed, when the article is standing on it, from above. When so viewed, the faceted area will appear brilliant because of the light incident on the upper face 12 being retroreflected towards the viewer.

The whole of the back face 13 of the base of the tumbler 11 of Figures 1 and 2 is faceted.

The stemmed glass 11 of Figures 3 and 4 is just part faceted in a four pointed star design, but of course any other design can be applied, such as a circle, an ellipse, crossed ellipses, a square, a triangle, a five or six pointed star, a heart shape, or more complex shapes such as company or club logos, animals, flowers, indeed, any shape that can be devised that will permit of being realised in the faceting.

The faceting can be effected in any appropriate size, for example with a spacing between apexes of the pyramidal projections 14 of 3.5 mm, 2.7 mm, 2.1 mm or less. Where the article rests on its base, it may be desirable that the points of the faceting are elevated, and the faceting may be done, then, within a rim, or the base may be concave to that end. The projections 14 of the tumbler of Figures 1 and 2 are recessed within a rim 15.

The front face 12 of the tumbler 11 is flat, while that of the stemmed glass 11 of Figures 3 and 4 has a shallow convex curvature. By 'shallow' is meant the depth at the centre, for a convex surface is no more than twice the average depth. A concave surface, such as might be the inner face of a tumbler, decanter, vase or the like, could have a depth at the centre greater than half the average depth. And, as already mentioned, 'substantially parallel' does not exclude that one face may be flat while the other is curved or that they may be oppositely curved.

By 'close packed' is meant contiguous or substantially so, with gaps between the bases of the pyramidal projections 14 less than one fifth the pyramid base length. For maximum retroreflection there should be no gap at all. Nor, again, for maximum brilliance, should the pyramidal projections 14 be truncated, though tiny culets could militate against wear of or damage to or by points.

Figures 5 and 6 illustrate the different effects of the conventionally star cut base (Figure 5) and the cut according to the invention. In the conventionally cut base of Figure 5, most of the base is flat, and light incident on the front face 12 mostly passes straight through, possibly retroreflecting off neighbouring surfaces of radial cuts, if the apex angles are right, which they seldom are, usually being around 120°. In the case of figure 6, it is seen that substantially all the light is retroreflected.

1() As mentioned above, pave effects in jewellery are effected by assembling individual stones.

In common with otherjewellery comprising gemstones, the crowns of the stones are exposed on the outer or front face. GB2492225 discloses the production of pave jewellery by punching, machining or otherwise working the outer face of a workpiece, or by an additive process such as 3D printing, but, again, to put the relief pattern on the exposed face.

Figures 7 and 8 illustrate a bracelet 71 with a pave applique 11. Prior art pave appliqués would comprise individual gemstones or glass crystals 73, as seen in the cross section of Figure 9, in some kind of mount, not shown. The gemstone crowns are on the front face, and they will, depending on the direction of incident light, reflect light from their facets or allow it to pass into the gemstone undergoing refraction and dispersion, and some, but by no means all, of the light will be totally internally reflected to emerge from one or other of the front face facets, where it will be further refracted and dispersed -a discussion of this is to be found in US2015/0201720, D. Swarovslci AG.

By contrast, in the pave applique shown in cross section in Figure 10, the front face 12 is unfaceted, so that, with light incident from behind the viewer there is substantially no front face reflection away from the viewer, the majority of the light passing straight through substantially without refraction or dispersion to be totally internally reflected off opposite faces of the rear face 13 faceting to be retroreflected back towards the viewer for maximum brilliance.

Aside from the brilliant effect, and advantage of this is that the front face is smooth and does not collect dirt, while the faceted face can be sealed in a mount.

For jewellery or objets d'art applications, of course, harder glass-like materials can be used, such as cubic zirconia, which can be obtained in appropriated sizes.

Figures 11 and 12 illustrate a stemmed glass 11 of which the underside 13 of the foot has parallel grooves leaving prismatic projections 14. While this is superficially similar to a star cut often found on quality crystal glassware, the grooves on such glassware usually have a much more obtuse included angle, usually about 120° and, while close together at the centre, spread out so that they do not define prisms, and there is no possibility of total internal reflection. Light reflected off the faces of the grooves can give the base a flash of brilliance, but only, usually, from one, at most a couple of grooves when incident light is at an appropriate angle.

Figure 13 illustrates a design in which the parallel projections 14 are circular. Again, light will be totally internally reflected off the inner faces of the projections 14 to be redirected out of the front face 12 for a bright, retroreflective appearance. Instead of being parallel circular projections, a spiral groove could be cut leaving a single spiral projection which sufficiently satisfies the requirements of close packing and parallelism for the purposes of the invention.

The faceting can be effected by any of the usual methods, as by cutting and polishing, etching, or by moulding. Polishing enhances the retroreflective effect by enhancing the total internal reflection.

Claims

Claims: 1 A pave effect article made of glass which at least in part comprises substantially parallel front and back faces, the back face comprising a relief pattern of close packed projections with parallel sides, the front face being unfaceted, the projections comprising even numbers of sides with an apex angle between 80° and 100°.
2 An article according to claim 1, in which the apex angle between 89° and 91°.
3 An article according to claim 1 or claim 2, in which the number of sides is four, so that the projections are pyramids.
4 An article according to claim 1 or claim 2, in which the number of sides is two, so that the projections are prisms.
An article according to any one of claims 1 to 4, comprising any conventional article of glass that affords the substantially parallel front and back faces.
6 An article according to claim 5, comprising an article of glassware, such as a tumbler, stemmed glass, carafe, jug or decanter having a base which will normally be viewed, when the article is standing on it, from above.
7 An article according to claim 6, in which the whole of the base is faceted.
8 An article according to claim 6, in which just a part of the base is faceted.
9 An article according to claim 8, in which the faceting is in a design such as a circle, an ellipse, crossed ellipses, a square, triangle, a star, a heart shape, or more complex shapes such as company or club logos, animals, flowers, or any other shape that can be devised that will permit of being realised in the faceting.
An article according to any one of claims 1 to 9, in which the faceting is effected with a spacing between apexes of 3.5 mm, 2.7 mm, 2.1 mm or less.
11 An article according to any one of claims 1 to 9, which normally rest on it base, and its base is faceted, in which the points of the faceting are elevated.
12 An article according to claim 11, in which the faceting is done within a rim.
13 An article according to claim 11, in which the base is be concave and the faceting elevated within the concavity.
14 An article according to any one of claims 1 to 13, in which the front face is flat or has a shallow convex or concave curvature.
An article according to any one of claims 1 to 14, in which the back face is flat or has a shallow convex or concave curvature.
16 An article according to any one of claims 1 to 15, in which gaps between the bases of the pyramids less than one fifth the pyramid base length.
17 An article according to claim 16, in which there is no gap between the bases of the pyramids.
18 An article according to any one of claims 1 to 4, comprising a pave appliqué of a piece of j ewellery.
19 An article according to any one of claims 1 to 18, in which the faceting is effected by cutting and polishing, etching, or by moulding.