WO2008046877A2

WO2008046877A2 - Matt glass sheet

Info

Publication number: WO2008046877A2
Application number: PCT/EP2007/061126
Authority: WO
Inventors: Georges Pilloy; Petr Hennebichler; Nadia Jacobs
Original assignee: Agc Flat Glass Europe Sa
Priority date: 2006-10-18
Filing date: 2007-10-18
Publication date: 2008-04-24
Also published as: WO2008046877A3; EP2074072A2

Abstract

Acid-etched matt glass sheets according to the invention have an acid-etched surface having a surface roughness defined by: Rz greater than 12 and less than 22 and Rz/RSm greater than 0.18 and less than 0.30, when measured over a sample length of 20 mm with a cut-off using the whole selected data length, a short range filter of 0.008 mm and a long range filter of 0.8 mm. Such glass sheets may show anti-slip properties and may advantageously be used as flooring.

Description

Matt glass sheet

The present invention relates to matt glass sheets, in particular acid- etched glass sheets, and to such glass sheets that may be used as floor covering.

By "matt glass sheets" we mean herein translucent glass sheets with a satin finish which diffuse light and may assure privacy. "Matt glass sheets" may preferably show at least one of the following properties: a luminous transmittance (LT) value of less than 90%, a haze value of more than 90% and/or a clarity value of less than 20% (all these values being measured on the acid -etched face of a clear glass sheet of 8 mm-thick).

Glass sheets according to this invention may have particular advantage for use as floor covering or for staircase steps, due to their anti-slip properties, in exterior and interior applications. They may also be used for example for decorative purpose, in furniture, wardrobes, in tables, shelves, in bathrooms or in shops displays.

It is known to use glass in the construction of flooring or staircase steps, but, as glass is smooth, it has the disadvantage of being slippery, especially when it is wet.

To avoid that problem, it is known to glue stickers of rough material at the surface of glass. But these stickers do not resist long to the passage of persons and tend to peel off from the glass, causing an additional danger. It is also known to deposit glass frit small particles at some places of the surface of the glass sheets but this is a complex and onerous process. EP 937 689 A1 describes an alternative which consists in making holes in the glass and fill them in with a resin comprising grains of a hard material.

All these previous methods to avoid slipping on a glass flooring have the inconvenient of necessitate additional steps which are very particular and which have to be adapted to the glass sheet in a very specific way; this is not convenient for mass production.

Beside that, matt acid-etched glass sheets are known, which may be used for floor applications. They are aesthetically pleasant and have the advantage, compare to clear glass, that what is under the flooring, e.g. concrete, is not visible.

Those types of glass sheets show the same disadvantage than clear glass, i.e. being slippery, especially when they are wet.

Conventionally, acid -etched glass sheets may be produced by controlled acid attack, during between 30 seconds and 15 minutes (depending on the acid solution used), on a surface of a pre-formed glass sheet. The acid attack produces a degree of surface roughness on the treated glass surface which results in reduced spectral reflection (due to greater diffusion of reflected light) and a fine matt appearance. This very fine surface roughness may be characterised by the combination of a Rz around 1 1 - 13 μm and a Rz/RSm around 0.14 - 0.17. RSm may vary between 60 and 100 μm. Rz and RSm are typical measures of surface roughness; the way to measure those values is explained hereunder.

According to one of its aspects, the present invention provides a glass sheet as defined by claim 1 . Dependent claims define preferred and/or alternative aspects of the invention.

The acid -etched surfaces of glass sheets according to the invention have a surface roughness defined by:

Rz greater than 12, preferably greater than 14, more preferably greater than 16 and less than 22, preferably less than 20, and

Rz/RSm greater than 0.18, greater than 0.20, preferably greater than 0.21 , more preferably greater than 0.22 and less than 0.30, preferably less than 0.28, more preferably less than 0.26.

All the roughness measurements herein were measured on a Taylor- Hobson Form Talysurf apparatus, in roughness mode. The samples were measured with the following parameters: Shape: LS line

Filter type: 2CR-PC

Sample length: 20 mm

Cut-off: "use the whole selected data length"

Short range filter: 0.008 mm

Long range filter: 0.8 mm

We have found that with a Rz and a Rz/ RSm slightly higher than those of common acid -etched glass, a texturing may be created at the surface of a glass sheet and a glass sheet according to the invention may show durable anti-slip properties, even when it is wet.

The present invention has particular advantages in relation to flooring or staircase steps, nevertheless it may also be used on shelves or shop displays, for example, on which the objects can not slip. Preferably, for these applications, only one face of the glass sheet may have a roughness in the range of the present invention. However, both faces of the glass sheet may be acid -etched.

Glass sheets according to the invention may show RSm greater than 65, preferably greater than 70, more preferably greater than 72 μm and less than 90, preferably less than 85, more preferably less than 80 μm.

Advantageously, glass sheets according to the invention, when tested according to standard DIN 51130:2004-6, show anti-slip properties ranging from R9 to R11 ; preferably, they reach R11. Here follow some examples of applications for R9, RI O and R11 :

Glass sheets according to the invention may preferably have L* (defined in the CIE L*a*b* system, for a clear glass sheet of 8 mm-thick, and measured on the acid-etched face of the glass sheet with a MINOLTA CM-2600d apparatus, with the following measurement parameters: illuminant C, 10° , SCI, white tile as background) of less than 72%, preferably less than 70%, more preferably less than 68%, and greater than 60%, preferably greater than 63%, more preferably greater than 65%. These values have to be compared with a conventional acid -etched glass which shows a L* value of around 73%. This lower L* value for the present ant-slip glass sheets may be explained by the change in roughness of the acid -etched surface.

Glass sheets according to the invention may preferably have at least one of the following properties: a luminous transmittance (LT) value of less than 90%, preferably less than 89% and greater than 84%, preferably greater than 86%, a haze value greater than 90%, preferably greater than 95%, more preferably greater than 98%, and a clarity value of less than 20% , preferably less than 10%, more preferably less than 7%, still more preferably less than 5%, and greater than 2%, preferably greater than 3%, more preferably greater than 4%, all these values being measured on the acid-etched face of a clear glass sheet of 8 mm-thick.

Clarity is a measure of the light that is scattered at small angles when passing through a glass sheet; haze is a measure of the light that is scattered at greater angles when passing through a glass sheet. All the measurements of haze and clarity referred to herein where made on a HAZE-GARD PLUS apparatus conform to the standard ASTM D-1003.

The glass substrate used may be float glass of various thicknesses (between 1 .8 and 16.2 mm, for example). A thickness greater than 6 mm is preferred for floor applications. For floor applications, the glass sheet may be tempered and/or laminated; for shelves or displays it may be tempered.

According to other aspects, the present invention provides a floor covering as defined by claim 9 and a method, as defined in claim 10, for manufacturing glass sheets according to the invention.

Acid -etched glass sheets according to the invention may advantageously be produced by controlled acid attack, using well-known acid-etching solutions commonly used in the manufacture of conventional acid-etched glass, during more than 5 minutes, preferably between 10 and 30 min (depending on the acid solution used) on a surface of a pre-formed glass sheet. The acid attack produces a degree of surface roughness on the treated glass surface, a texturing which results in anti-slip properties. The acid attack may be made in one or several steps.

An embodiment of the invention will now be further described, by way of example only.

Example

A sheet of clear float glass 8 mm-thick is acid-etched in a known manner, but during a longer time than for conventional acid-etched glass. In this case the duration of the acid attack was 25 minutes.

The roughness of glass sheet was then measured by a Taylor- Hobson Talysurf analysis of surface roughness, as commonly used for analysing surface roughness. The analysis consists of arranging a fine stylus having a calibrated point in contact with the surface to be analysed and slowly displacing the stylus across the surface so as to record all variations in the altitude of the surface. The parameters cited above were used to carry out this analysis.

The following results were obtained for one particular glass sheet: Rz = 18.10 μm RSm = 77.89 μm

Rz/RSm = 0.23 Where:

Rz (also called Rtm) is the average of all of the values Rz1 , Rz2 .... etc. over the entire profile Rz1 is the greatest difference in altitude between the highest peak and the lowest valley over the first cut-off portion of the sample

Rz2 is the greatest difference in altitude between the highest peak and the lowest valley over the second cut-off portion of the sample (and so on for Rz3) RSm (also called Sm) is the average of the distance between each time the profile crosses the average line; it represents an indication of the average distance between the main peaks of the profile.

The short range filter and long range filter, as commonly used in the art of measuring surface roughness, are used to separate a characteristic measurement of surface roughness from an overall "waviness" of the sample and from very short wavelength effects.

L*, measured on the acid -etched face, had a value of 66.69%. Tests according to DIN 51130:2004-6 revealed that the glass sheet was at level R11.

A sample was installed as flooring over which a lot of persons walked. After 2 months, tests according to DIN 51130:2004-6 revealed that the glass sheet was at level R10, which means that the glass sheet kept its anti-slip properties.

Claims

1. Acid-etched matt glass sheet, characterised in that an acid-etched surface of the glass sheet has a surface roughness defined by:

Rz greater than 12 μm and less than 22 μm and Rz/RSm greater than 0.18 and less than 0.30, when measured over a sample length of 20 mm with a cut-off using the whole selected data length, a short range filter of 0.008 mm and a long range filter of 0.8 mm.

2. Glass sheet according to claim 1 , in which said acid-etched surface of the glass sheet has a surface roughness defined by:

Rz greater than 16 μm and less than 20 μm and Rz/RSm greater than 0.20 and less than 0.26.

3. Glass sheet according to claim 1 or claim 2, in which said acid- etched surface of the glass sheet has a surface roughness defined by:

RSm greater than 65 μm and less than 90 μm.

4. Glass sheet according to claim 3, in which said acid-etched surface of the glass sheet has a surface roughness defined by:

RSm greater than 72 μm and less than 80 μm.

5. Glass sheet according to any preceding claim, characterised in that it has anti-slip properties determined by standard DIN 51 130:2004-6 showing values of between R9 and R1 1.

6. Glass sheet according to any preceding claim, in which L* measured on the acid-etched surface of a clear glass sheet of 8 mm-thick, is less than 70% and greater than 63%.

7. Glass sheet according to any preceding claim, having at least one property selected from the group consisting of a luminous transmittance (LT) of less than 90%, a haze greater than 90%, and a clarity of less than 20%, when measured on the acid-etched surface of a clear glass sheet of 8 mm-thick.

8. Glass sheet according to any preceding claim, in which the glass sheet has a thickness of at least 6 mm.

9. A floor covering comprising a glass sheet in accordance with any preceding claim.

10. A method of manufacturing a glass sheet in accordance with any of claims 1 to 6 by producing a surface roughness on a surface of the glass sheet, by means of an acid treatment of the surface of the glass sheet during at least 5 minutes.