IE20030776A1 - Method of detecting very barely discernible thin coatings - Google Patents

Abstract

The present invention relates to a method of detecting a coating on a glass substrate, the reflection properties of a light ray reflected by the said coating being known, especially at its interface with the air, characterized in that the reflection of a light ray by the surface to be tested of a glass substrate or a monolithic, laminated or multiple glazing unit, and then by another surface are measured in succession and then in that the results are compared so as to determine whether the said surface to be tested is provided with the said coating. The invention also relates to a device for implementing this method and to the application of this method to various glazing units.

Description

The invention relates to the detection of thin coatings on glass or an equivalent material, in particular the detection of very barely discernible thin coatings.

Among the coatings to be detected, mention may be made of all the coatings that have a different reflection from that of glass, and the coatings referred to as water-cleaning, self-cleaning, anti-fouling, easy-to-clean, hydrophilic/oleophilic, hydrophobic/ oleophobic, photocatalyic, coloured or uncoloured, transparent coatings. Mention may be made of coatings based on SiO2, SiOC, TiO2, and fluorosilane, in particular one having a (per)fluoroalkyl functional group.

As regards coatings having a water-cleaning, self-cleaning, solar-protection, easy-to-clean character, etc., the cleaning function is effective only if that face of the glazing on which the coating (or coatings) is deposited is in contact with the external atmosphere .

It therefore proves to be absolutely essential to ensure in the factory that the coating face is properly located on an external face of a double glazing unit when this coated glass is assembled as a double glazing unit; it also proves to be absolutely essential in the field to check that the coated face is mounted facing the outside of the building.

In addition, in the · case of what are called self-cleaning coatings, that are chemically active, particularly based on nanoparticulate anatase TiO2, it is important during manufacture of double glazing units IE OS 07 7 8 that the glass with the said coating be facing the correct side (coating on the outside), otherwise there is a risk of the active coating degrading the organic seals that seal the double glazing unit. Likewise, it is necessary to make sure that such a chemically active coating is not in contact with the plastic interlayer of a laminated glazing or any other organic assembly product that would then be progressively degraded, leading to rapid deterioration of the glazing.

It is therefore paramount to be able to detect the position of the coated face of the glass, both during assembly of double glazing units, multiple glazing units, laminated glazing, etc. and when the glazing is being fitted into buildings or transport vehicles.

The optical characteristics described above of these coatings (lack of colouration, transparency, reflection close to that of the glass) make visual detection of the position of the coated face on the glazing impossible during its assembly and when it is being fitted on the work site.

The dielectric nature of the coating precludes the use of a commercially available detector operating by electrical conduction.

The coating may be detected by an optical device, the principle of which is based on measuring the reflection of the light by the faces of the glazing. These devices measure the amount of light specularly reflected by the surface with which they are in contact. This measurement employs an optoelectronic system that compares the signal thus obtained with a reference value stored in the detector. This reference value, which is set during design of the detector, corresponds to a signal level slightly higher than that obtained by reflection on a glass face. If the measured signal is weaker than the reference signal, the face in contact IE 0 3 0 7 Ί S with the device is a glass face, if the signal is stronger than the reference signal, the device is in contact with the coating face.

It has been found that, in use, such a detector delivers erroneous results after a short time in use. The principal cause of these detection errors lies in the contamination of the measuring optic. When, as is inevitable, the measuring optic is progressively contaminated (with dust, fingerprints, scratches, etc.), the reflected light is attenuated until a level systematically below the reference signal is reached, whatever the nature of the face in contact with the detector. The detector then sees only glass faces, with the risk of the glazing being improperly assembled or improperly fitted. Since such a device cannot be cleaned by the users, the detector is then out of commission.

The object of the invention is to make available a means of detecting a thin coating, especially one that is very barely discernible, deposited on glass, that overcomes the problem of any pollution or deterioration of the detector, in particular of the measuring optic, as mentioned above.

For this purpose, the subject of the invention is a method of detecting a coating on a glass substrate, the reflection properties of a light ray reflected by the said coating being known, especially at its interface with the air. The particular feature of this method resides in the fact that the reflection of a light ray by the surface to be tested of a glass substrate or a monolithic, laminated or multiple glazing unit, and then by another surface are measured in succession and then the results are compared so as to determine whether the said surface to be tested is provided with the said coating.

IE 0 3 07 7 β The advantage of this detection method lies in the two measurements that compensate for the attenuation of the signal that may result from a contamination or another phenomenon (a drift in the measurement electronics, for example). If the measured first signal SI is attenuated by a factor r, the second signal S2 will be attenuated by the same factor r. Now, to compare the results of the two measurements, the ratio of the two measured signals, in this case r.Sl/r.S2 = S1/S2, is determined according to an advantageous method of implementation. This ratio is therefore identical to that obtained without attenuation of the signals SI and S2.

It is possible, when implementing this method, to compare the surface to be tested with a control surface consisting, for example, either of the expected surface provided with its coating, especially a glass sheet + coating, or of the same substrate without the coating (glass sheet alone). In the first case, the presence of the coating will give a ratio of the signals that is sufficiently close to 1, while in the second case it will be sufficiently far from 1; the absence of a coating will lead to the opposite results.

However, it is preferred for the said other surface to be the opposite face of the said surface to be tested of a glass substrate or a monolithic, laminated or multiple glazing unit. This is particularly advantageous when only one of the two faces of the said glass substrate or monolithic, laminated or multiple glazing unit is provided with the coating, which situation constitutes a preferred way of implementing the present method. This is because in this case the presence of the coating in the first or the second measurement results in a ratio of the signals that is higher, or alternatively lower, than 1 assuming that the reflection by the coating is greater than that by the substrate without the coating.

IE 0 3 07 7 8 According to preferred methods of implementation: the said coating is, as indicated above, a water-cleaning, self-cleaning, anti-fogging and/or anti-fouling (the fouling being of the organic and/or mineral type), easy-to-clean, hydrophilic/oleophilic or hydrophobic/oleophobic and/or photocatalytic, coloured or uncoloured, transparent coating, especially one based on SiO2, SiOC, TiO2 or fluorosilane, in particular one having a (per)fluoroalkyl functional group; and the said results are compared by positioning the ratio of the signal SI of the rays reflected by the first face to the signal S2 of the rays reflected by the second face relative to two positive numerical values a and b respectively less than and greater than 1 (as an example, it is possible to choose a = 0.9 and b = 1.1) .

The subject of the invention is also a device for implementing the method described above, comprising at least one button for initiating the measurement, a measurement circuit consisting of a light source, a measurement window, a receiver associated with a circuit for amplifying and digitizing the signal, and two light-emitting diodes.

Advantageously, the source/window/receiver system is placed in a configuration that makes it possible to illuminate the face subjected to the measurement at an angle of incidence high enough for only the rays reflected by the said face to reach the receiver. Another subject of the invention consists of the application of the above method to glazing for buildings , especially of the double glazing type, to glazing for vehicles of the automobile windscreen, rear window or side window type, or for land, air or sea transport vehicles, to utility glazing, such as glass for aquariums, shop windows, greenhouses, glazing for interior decoration, glazing for showers, glazing for urban furniture, mirrors, screens, especially television screens, and glazing with electrically controlled variable absorption.

The invention will now be illustrated by the following implementation example.

The presence will be detected, on one of the faces of a sheet of soda-lime silica float glass 4mm thick, of a 25 nm thick TiO2 layer as described in Patent EP 0 850 204 .

A detector in the form of a box that can be easily handled is used, this being equipped with a button for initiating the measurement, with two light-emitting diodes (LEDs) and with a measurement window made on the lower face of the box, which face will be in contact with the face to be tested.

The measurement circuit of the detector consists of an LED-type light source, a measurement window protected by a thin glass plate or the equivalent, and a photodiode-type receiver or equivalent associated with a circuit for amplifying and digitizing the signal.

The source/window/receiver system is placed in a configuration that makes it possible to illuminate the surface to be measured at an angle of incidence high enough (about 60°) for the rays reflected on various faces and interfaces to be sufficiently far apart and thus able to be easily separated thanks to the width of the window or diaphragm, the ray reflected on the coating being the only one picked up; the light reflected by the other faces of the glazing (including via the interface between the coating and its substrate) is not perceived. Only the light beam reflected by the face to be measured reaches the receiver.

IE 03 07 7 6 The emission wavelength of the LED is chosen according to the spectrum in reflection by the coating to be detected. Since the water-cleaning, self-cleaning, etc. coatings mentioned above have a reflection maximum in the blue part of the visible spectrum, in which they reflect more than the glass substrate that they coat (for example 8% of the rays instead of 4%), an LED that emits in this spectral band is chosen.

The processing electronics consist of a suitable electronic controller and necessary peripherals (memory, etc .) .

The test phase consists in placing the detector in contact with the surface to be tested of the glazing and in pressing a button in order to carry out the first measurement. Next, the operator places the detector on the second face of the glazing and then initiates a second measurement. Two LEDs referenced face 1 (first measurement) and face 2 (second measurement) inform the operator of the number of the coating face. If the coating has been detected during the first, or alternatively the second, measurement, the face 1 LED, or alternatively the face 2 LED, lights up. In the absence of a coating, the ratio of the signals is, for example, between 0.9 and 1.1, that is to say it is considered neither less nor greater than 1, and no LED lights up unless a third LED is provided for this purpose. A judicious arrangement of the LEDs and the addition of informative screen printing on the box facilitate the use and the interpretation of the results .

Claims (8)

1. Method of detecting a coating on a glass substrate, the reflection properties of a light rayreflected by the said coating being known, especially at its interface with the air, characterized in that the reflection of a light ray by the surface to be tested of a glass substrate or a monolithic, laminated or multiple glazing unit, and then by another surface are measured in succession and then in that the results are compared so as to determine whether the said surface to be tested is provided with the said coating.

2. Method according to Claim 1, characterized in that the said other surface is the opposite face of the said surface to be tested of a glass substrate or a monolithic, laminated or multiple glazing unit.

3. Method according to Claim 2, characterized in that only one of the two faces of the said glass substrate or monolithic, laminated or multiple glazing unit is provided with the coating.

4. Method according to one of the preceding claims, characterized in that the said coating is a water-cleaning, anti-fogging and anti - fouling, easy-to-clean, hydrophilic/oleophilic, transparent coating based on at least one of the compounds SiO 2 , SiOC and TiO 2

5. Method according to Claim 1, characterized in that the said results are compared by positioning the ratio of the signal SI of the rays reflected by the first face to the signal S2 of the rays reflected by the second face relative to two positive numerical values a and b respectively less than and greater than 1. IE os 07 7 6

6. Device for implementing the method according to one of Claims 1 to 5, comprising at least one button for initiating the measurement, a measurement circuit consisting of a light source, a measurement window, a receiver associated with a circuit for amplifying and digitizing the signal, and two light-emitting diodes.

7. Device according to Claim 6, the source/window/receiver system of which is placed in a configuration that makes it possible to illuminate the face subjected to the measurement at an angle of incidence high enough for only the rays reflected by the said face to reach the receiver.

8. Application of the method according to one of Claims 1 to 5 to glazing for buildings, especially of the double glazing type, to glazing for vehicles of the automobile windscreen, rear window or side window type, or for land, air or sea transport vehicles, to utility glazing, such as glass for aquariums, shop windows, greenhouses, glazing for interior decoration, glazing for showers, glazing for urban furniture, mirrors, screens, especially television screens, and glazing with electrically controlled variable absorption.