DK143696B - PROCEDURE FOR PREPARING A HEAT REFLECTING WINDOW - Google Patents

Description

(19) DENMARK

W c «) SUBMISSION WRITING on 11 + 3696 B

DIRECTORATE OF THE PATENT AND TRADEMARKET SYSTEM

(21) Application No. 4110/72 (51) intCI. * C 03 C 17/40 (22) Filing date 18 Aug. 1972 // C 03 C 17/09 (24) Race day 1 8 Aug. 1972 E 06 B 9/24 (41) Aim. available Feb 20 1973 (44) Presented 28 Sep. 19 ^ 1 (86) International application no.

(86) International filing day (85) Continuation day - (62) Master application no. -

(30) Priority ig. August 1971 in 7130168, PR

(71) Applicant SAINT-GOBAIN INDUSTRIES, P 92 Neullly-BUT-Seine, FR.

(72) Inventor Sabatino _Cohen, PR.

(74) Clerk of the International Patent Office.

(54) Method of producing a heat reflecting pane.

BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to a method of producing a heat-reflecting pane with a gold-evaporated gold coating applied to a vacuum-evaporated substrate.

It is known to produce panes which are transparent despite having one or more very thin metal coatings which impart special optical transmission and reflection properties to the pane, taking into account specific requirements.

For use in buildings, it is thus known to produce panes with a thin 0Q gold coating to reflect the infrared rays as much as possible and absorb the visible part of the light spectrum as much as possible.

The preparation of such metal coatings is usually carried out by the known method of evaporation under vacuum, with gold being one of the metals most commonly used for such panes. The gold layer can be anchored to an "extremely" thin sheet of another metal, e.g. aluminum. If the gold layer which satisfies the optical function alone is thin enough to achieve a satisfactory transmission coefficient of e.g. 70¾ within the visible part of the light spectrum, however, the coefficient of reflection in the infrared region is insufficient to prevent the pane from heating and gives the known greenhouse effect. If, on the other hand, the metal coating is sufficiently thick to suppress the greenhouse effect, the transmission coefficient of the pane in the visible part of the light spectrum is too small for sufficient lighting in the room to be obtained.

From the data provided by SCHRODER in the publication "Glastechnische Berichte" 39 (1966) 3, pages 156-163, it appears that a pane with a gold coating of about 100 A exhibits a transmission maximum of about 657. in the visible part of the spectrum, but in the infrared region has a reflection coefficient of about 30% for 1.1 μ, which coefficient decreases as the wavelength increases.

In other words, one can say that so far, thin gold coatings have not made it possible to create panes that have both a high coefficient of transmission in the visible part of the spectrum and a high coefficient of reflection in the infrared region.

The invention aims to remedy this disadvantage and provides glazing with a gold coating which is both sufficiently transparent in the visible part of the spectrum, thereby obtaining the desired brightness, and sufficiently reflective in the infrared range ti.1 under sunlight to avoid a unnecessary heating of the window and the room.

To this end, the method according to the invention is characterized in that the blank is applied to a substrate of aluminum in such a thickness that, at a wavelength of 0.404 µm, it results in a reduction of the light transmission through the pane of 5-30% compared to the light transmission through the blank. coating, after which the gold coating is applied to the aluminum substrate until such thickness is obtained so that this coating itself gives a reduction of approx. 30% of the light transmission through the substrate with the substrate being applied, if desired - on top of the gold coating another vacuum evaporated layer of aluminum.

The invention is based on the finding that when bonding a gold coating to a glass body by means of an aluminum substrate, the thickness of the individual layers plays a very significant role.

This is due to the following three considerations: 1) For wavelengths between 0.5 and 0.8 µm, ie. in the visible part of the spectrum, a two-layered pane has a greater light transmission than if the pane had only a gold coating of the same thickness.

2) At wavelengths above 1.25 µm, the transmission through the two-pane pane is significantly lower than through the pane with only one gold coating.

3) At wavelengths below 0.5 µm, the transmission through the pane fitted with the two layers is practically identical to the transmission through a pane having only a gold coating.

The aluminum substrate provided in accordance with the invention causes a special crystalline state in the gold coating subsequently applied, which in turn causes the desired optical properties of the pane to be obtained, i.e. in particular, a high transmission coefficient in the visible part of the spectrum and at the same time a satisfactory reflection coefficient in the infrared region.

The data given below confirms the surprising effect of the presence of a substrate according to the invention, provided it has the thickness given here.

This data is shown in FIG. 1, which shows for panes with gold coatings curves A and B for the transmission and A ^ and for the reflection as a function of the wavelength in μπι.

The wavelength is indicated on the abscissa axis, while the transmission and reflection percentage is indicated on the ordinate axis.

Specifically, curve Δ shows the transmission of a pane with a gold coating placed directly on the glass carrier and where a transmission of 30% deterioration is obtained over the original transmission, while curve B shows the transmission of a pane with a gold coating of the same thickness of a substrate of aluminum, the thickness of which corresponds to a deterioration of 25% of the original transmission through the carrier.

It is noted that for the measurement of the transmission for the purpose of assessing and selecting the coating applied, a wavelength of 0.404 per, corresponding to the violet line for mercury, has been chosen.

A comparison between curves A and B leads to the surprising finding that within the visible part of the spectrum, the transmission through a pane with two successive aluminum and gold coatings - corresponding to curve B - is significantly greater than the transmission through the pane with only one gold coating. - corresponds to curve A. This proves, after all, that the aluminum substrate has a special structure in the applied gold coating that imparts new optical properties to this gold coating.

It is noted, among other things, the peculiar and particularly appropriate that the transmission maximum of approx. In the present case, 70% are close to the maximum for eye sensitivity, thereby improving the luminous intensity, which is not the case with a gold coating applied directly to the glass pane, cf. curve A in FIG. First

FIG. 1 shows for the same subjects the reflection curves A ^ and B ^ proving that in the visible part of the spectrum there is a very reduced reflection and that for the pane having the aluminum substrate and the gold coating (curve B ^) 0.8 µm and towards the infrared a strong growing reflection.

143696 4

For practical use, these results can be converted into a "sunlight factor" and a "brightness factor" respectively, which factors are defined as follows: solvation factor - through energy + transmitted giergi (1) 3 incoming energy (1), especially in the form of infrared rays brightness factor = S ^ breathable energy? JJ of incoming energy, taking into account corrections required to take into account the spectral distribution of solar energy and the special sensitivity of the eye.

Based on these definitions, the subject Δ (only one gold coating) and the subject B (gold coating on an aluminum substrate) have the following sunlight and brightness factors:

Sunlight factor Brightness factor

Subject A 59% 60%

Subject B 64% 707o

It is known that you want the sunlight factor, ie. the continuous heat energy. must be as small as possible and that the brightness factor, ie. the lighting in the room must be as large as possible.

The curves show that when switching from workpiece A to workpiece B, the sunlight factor has only a relative increase of 8.5%, while the brightness factor improves by more than 16%.

The advantage obtained by using an aluminum substrate according to the invention can be realized in another way, namely by comparing the sunlight factors for the two blanks when they are designed to exhibit the same brightness factor or vice versa, by comparing the brightness factors when the subjects have the same sunlight factor.

Sunlight factor with only one coating of gold for approx. 74% given brightness factor · Sunlight factor with a substrate j of aluminum and a gold over-1 feature: approx. 64% 'Brightness factor with only one gold coating approx. 65% given sunlight factor of 6 F ° Brightness factor with one! aluminum substrate and a gold plating approx. 707 »

From the foregoing it appears that at constant brightness factor, the use of an aluminum substrate leads to a reduction, ie. an improvement of the sunlight factor and a constant sunlight factor for an increase, ie. an enhancement of the brightness factor.

Another important advantage of the invention is that, by this combination of a gold coating on an aluminum substrate, it is able to affect the color of the pane when viewed with a translucent light, shifting the blue-green color normal to the gold coating. towards the yellow area. This can be of great interest in glazing for buildings.

A further significant advantage of using an aluminum substrate lies in the fact that, during manufacture, a better reproducibility of the color of the pane can be obtained, which is also a significant factor in the manufacture of glazing for the purpose mentioned.

Furthermore, the process of the invention allows, by stabilizing the crystalline structure of the gold coating, to obtain electrical properties which could only be obtained by the prior art processes if considerably thicker layers were used, which had the disadvantage of significant deterioration of the transmission coefficient in the visible part of the spectrum, ie. of the brightness factor.

It should be noted that a gold coating on a sufficient substrate of aluminum is characterized by an improved electrical conductivity approaching the solid metal conductivity.

A metal coating comprising an aluminum substrate of such thickness as to reduce the transmission coefficient by 11% and a gold coating of such thickness to reduce transmission by 30% have a square surface resistance of 18 olm, while only a gold layer of the same thickness has a square surface resistance of 8000. ohms.

Thus, it is possible to produce electrically conductive and yet transparent panes which, e.g. can be used as heating panes in buildings or as car windows for auxiliary heating or removal of dew or rhyme.

On the semi-reflective double layer, another layer of aluminum can be deposited using the method described in French Patent Specification 2135o33, in which case a thinner substrate is used. In other words, the aluminum layer can be divided into two layers.

FIG. 2 shows the transmission characteristic T and the reflection characteristic R as a function of the wavelength of such a window, which will be discussed in more detail in the following examples.

As mentioned in the aforementioned patent, the use of yet another optical aluminum layer on the semi-reflective bilayer according to the invention has the surprising result that the adhesion of the metal coating is improved and that for a given sunlight factor and for a given brightness factor there is more freedom in the choice of the 6 143696 final color of the pane seen with penetrating light.

It is known that in accordance with the standards laid down in 1931 by the '' Commissin Internationale de l'Eclairage ', the color can be defined by the dominant wavelength and by the purity factor. In the following, these factors must be used to characterize the color of the pane. .

It is noted that the method according to the invention allows for new properties which could not be obtained by the measures according to the above-mentioned patent, with regard to the optical properties of the finished pane, and in particular with regard to the sunlight factor and the brightness factor.

For example, if plots on a diagram (Fig. 3) the properties of the pane defined by the sunlight factor (FS) plotted on the ordinate axis and the brightness factor (FL) plotted on the abscissa axis, the points representing the panes obtainable by the method of the invention will be within square JKHG, where the vertices have the following coordinate pairs: FL 0.83 FL 0.83 FL 0.52 FL 0.52

J K H G

FS 0.80 FS 0.67 FS 0.39 FS 0.52

In terms of practical application, the preferred area is the area defined by the square N.M.E.B, whose vertices have the following coordinate pairs: FL 0.80 FL 0.80 FL 0.60 FL 0.60

N Μ E B

FS 0.78 FS 0.65 FS 0.46 FS 0.59 The diagram shows the areas ABCD and FGHI made available by the method of the above patent. It will be seen that the range of NMEB made available by the method of the invention is outside the range made available by the method of said patent.

The practice of the method according to the invention is clarified in the enlightening with reference to two examples:

Example 1.

The example applies to the two items A and B mentioned above and whose light transmission curve and light reflection curve are shown in FIG. First

Two 4 mm thick glass plates A and B are placed side by side in a vacuum chamber and a 10 min prolonged discharge treatment is performed under vacuum. Then the pressure is lowered to 2.10 Torr. After covering the blank A with a mask which is controlled from the outside, the source of aluminum vapor which can only be deposited on the blank B. The heating is stopped when measurements of the transmission at a wavelength of 0.404 µm show that the original transmission through the blank B is been reduced by 25%. This is achieved after 13 sec. After removing the mask from item A, gold evaporation is performed so that both items are applied to gold vapor. This treatment lasts until a further reduction of the transmission of 30% is obtained for the part A, which lasts 80 seconds. Subjects A and B are removed from vacuo fires and their transmission and reflection properties as a function of wavelength are examined. The results are shown in FIG. First

For each item, the sunlight factor and the brightness factor are deduced from these curves and values of 0.59 and 0.60 are obtained for item A and 0.64 and 0.70 for item B.

The color of the blank B is characterized by a dominant wavelength of 0.570 µm and a uniformity factor of 7%.

Example 2.

The example applies to the embodiment of the invention, in which, after application of an aluminum substrate and a gold coating to the workpiece, another layer of aluminum is applied.

To begin with, proceed as described in Example 1, limiting the first layer of aluminum vapor to achieve a reduction of only 10¾ of the original transmission through the blank, which requires 10 seconds. Then, the blank is coated with gold as indicated in the previous example until a further reduction of 30% transmission is obtained for blank A, which takes 66 seconds. Then, another layer of aluminum is applied until a further reduction of 25% is achieved for the part A, which lasts 22 seconds.

The obtained object is removed from the vacuum chamber and its optical properties examined. The transmission characteristic T and the reflection characteristic R are shown in FIG. 2nd

The sunlight factor is 0.56 and the brightness factor is 0.615. The color is characterized by a dominant wavelength of 0.54 pra and a purity factor of less than 2%, which corresponds to practically a neutral color.