IE43892B1 - Coated transparent sheets - Google Patents

Abstract

1518580 Self heating coatings SAINTGOBAIN INDUSTRIES 3 Dec 1976 [5 Dec 1975] 50513/76 Heading B2E [Also in Division G2] A sheet of transparent material having on at least one of its surfaces a semi-reflecting metal layer covered with a protective layer of soft plastics material capable of selfhealing after scratching. The plastics material may be a partly reticulated polyurethane prepared from a polyglycol ether obtained by condensation of propylene oxide and trimethylolpropane containing from 10.5 to 12% of free hydroxyl groups and biuret of 1-6 hexamethylenediisocyanate containing from 21 to 22% of isocyanate groups the weight ratio of biuret to ether being from 0.9 to 1.1. The layer may have a thickness of 50 to 1,000 microns and the sheet may be of mineral glass or of a plastics material and may be a window pane, optical apparatus mask or spectacles. Reference has been directed by the comptroller to Specification 1487529

Description

TliQ present invention relates to sheets of transparent·1 material such as mineral glass or transparent plastics provided on at least one of their faces with a semi-reflecting metallic layer. , Sheets of this type may be manufactured starting from a transparent sheet of organic or mineral glass on which there is deposited under vacuum one or more metal layers, such as copper, gold, silver and aluminium.

Sheets of this type and their method of manufacture are described for example in''British Patent Specification Kos. 1336825, 1356774 and 1513826. Such semi-reflecting sheets, in which the metal layer may be used as an electrical conductor, find uses in building, optical apparatus, masks and spectacles for protecting the eyes, anti-heat panes, heating panes and filters. Because of the fragility of the deposited layers, these sheets when used as window panes have to be used as laminated panes or airtight double panes, their coated face being placed inside. By this means the layers deposited under vacuum are protected from mechanical or chemical attack due for example to dust, rubbing, atmospheric pollution and cleaning materials.

The cost of such laminated or multiple panes is quite high and it would be advantageous to be able to manufacture commercially monolithic panes having the same optical properties and properties of conduction or heat-resistance.

The present invention has as its subject semi-reflecting panes provided with layers deposited under vacuum which may have excellent resistance to mechanical and chemical attack. x -2438SS According to one aspect of the invention there is provided a sheet of transparent material provided on at least one of its surfaces with a semi-reflecting metal layer covered with a protective layer of soft plastics material capable of self-healing after scratching.

In one embodiment the soft plastics material is a partly reticulated polyurethane.

The polyurethane may be prepared from a polyglycol ether resulting from the condensation of propylene oxide on trimethylol propane containing from 10.5 to 12% by weight of free hydroxy groups (component 1) and a biuret of 1-6 hexamethylenediisocyanate containing 21 to 22% of isocyanate groups (component 2), the weight ratio of component 2 to component 1 being from 0.9 to 1.1.

The protective layer of soft plastics material may have a thickness from 50 to 1.000 microns.

This protective layer may be deposited in the liquid state on the face or faces of the sheet to be protected after which reticulation of the plastics material is carried out.

Application of the plastics layer may be carried out by flow from a film-drawing device, by spraying or by immersion if both faces of the sheet are to be coated.

Embodiments of the invention will be described by way of illustration in the following Examples.

EXAMPLE 1 Two glass plates of dimensions 10 cm x 10 cm are coated by vacuum deposition on one of their faces with a copper layer itself covered with a layer of aluminium. The 3i serai-reflecting samples thus obtained have a ruby colour.

There is mixed a polyglycol ether resulting from condensation of propylene oxide on trimethylol propane containing 11% of free OH groups (component 1) with a biuret of 1-6 hexamethylenediisocyanate containing 21% Of isocyanate groups (component 2) in a weight ratio of 1:1 of the two components.

The liquid mixture is degassed and deposited by means of a film-draxfing device in such a manner as to obtain a protective layer of 250 microns thickness on the surface coated with copper and aluminium of one of the two glass samples previously heated to 60°C. The coated sample is then placed for 45 minutes in a stove heated to 6o°C in order fo carry out reticulation of the layer of polyurethane obtained.

The optical characteristics of each of the two samples are measured and the results are plotted in Figure 1 for sample No. 1 (without protective layer) and in Figure 2 for sample No.2 coated with the protective layer ) of polyurethane.

In these diagrams showing wavelength as abscissa curve T gives (as ordinate) a coefficient of transmission curve R the coefficient of reflection from the side of the samples supporting the layers and the curve R> the coefficient of i reflection from the side opposite the layers.

By integrating the values of the coefficients of transmission and reflection on each surface for the whole solar spectrum it is possible to calculate for each sample the total transmission energy factor TW, the total energy -443882 reflection factor RW for the coated surface and the total reflected energy factor R'W for the non coated surface.

In the same way, restricting to the visible range of the spectrum there are calculated corresponding factors TL, RL, R'L concerned exclusively with luminous energy.

The values of these different factors are given in the table below.

TABLE 1 TW RW R’W TL RL R'L Sample 1 (without protective layer) 27 50 39 4l 33 23 Sample 2 (with protective layer) 33 42 38 48 25 25 It will be seen that the factors of transmission TW and TL are greater in the case of sample 2 covered with plastics material than in the case of sample 1» The reflection factors R’W and R’L (on the non coated surface) are practically the same for the two samples but the reflection factors RW and RL (relative to the surface provided with the layer) are somewhat less for sample 2 coated with plastics material.

It will be seen that from the optical point of view the influence of the protective film of polyurethane is beneficial for most applications.

It should also be noted that it is possible to modify the optical characteristics of the sample coated with plastics film in various ways: for this it is possible to estimate -5the final effect of the protective layer at the moment of deposition under vacuum and act in consequence on the predicted values of transmission or reflection. To measure the adherence of the film of plastics material the sample No. 2 is subjected to an ageing test in a cycling cupboard as follows· Each cycle, having a total duration of 6 hours, is carried out at 90% relative humidity and consists of the following phases! - Increase in temperature from 0 to 40°C in 3θ minutes· - Holding at 40°C for 3 hours· - Return to 0°C in 30 minutes.

- Held at 0°C for 2 hours.

This cycle is repeated a large number of times up to 5 about 5θ0 hours duration and it is found that the adhesion of the plastics material film is very good and well maintained during this time.

To observe, the resistance which the film gives to abrasion the two samples are subjected to the following tests: A-A typewriter eraser rubber is rubbed several times on the layer of sample No. 1 (not coated, with plastics material).

The metal layers are totally removed. If this operation is repeated on sample 2 coated with plastics material, the surface remains absolutely intact. > B - Another test consists of subjecting the two samples to a jet of abrasive powder (REGAWIT IV - Trade Mark) having the following grain size distribution: -643SS2 Grains 0.4 to 0.2 mm 1.4% Grains 0.2 to 0.1 mm Grains 0.1 to 0.08 rani Fines 91.5% .5% 1.5% The jet of abrasive powder is directed onto the samples from a distance of 85 to 90 cm under a pressure of 0.5 kg/cm2, the passage time for sweeping the length of the sample being about 1 second.

After a certain number of passages the apparent turbidity of the samples are measured. After 12 passages the turbidity reached is 85% for the non protected sample and only 10% for the sample protected by the plastics layer. EXAMPLE 2 The procedure of Example 1 is followed but starting from two glass plates coated on one face by deposition under vacuum, successively of an aluminium layer, a gold layer and a second layer of aluminium.

The semi-reflecting samples thus obtained have a gilt colour.

As in Example 1, the optical characteristics of the two samples are measured and Figure 3 shows the results plotted for sample No. 1 (without a protective layer) and Figure 4 shows the results for sample No. 2(coated with a protective layer).

The table below gives the factors for transmission and reflection of the samples for total solar radiation and for the visible spectrum. -7438S2 TABLE 3 Τίί RW R’W TL RL R'L Sample 1 (without protective layer) 26 50 37 %3 34 23 Sample 2 (with protective layer) 32 42 37 50 27 25 The results show the advantageous effect of the protective film of plastics material.

The test for resistance to ageing and resistance to abrasion gives results which are as satisfactory as in Example 1 in favour of the sample coated with the protective layer.

In particular the test for abrasion by a jet of abrasive powder shows that from the first passage of the unprotected sample, not only the metallic layers are eliminated but the glass is roughened whereas after 20 passages on the protected sample the latter has a turbidity less than 18%, the metal layers being intact below the film of polyurethane.

The results given above show that the panes provided with layers deposited under vacuum and coated with a protective film of self-healing polyurethane may be used in monolithic panes’ without any risk of deterioration of the semi-reflective layers. The same is true in the case when the transparent support is of organic glass.

In the two preceding Examples, the film of self-healing polyurethane is deposited on the coated surfaces of samples by means of a film drawing device. It is of course possible -8438S2 to deposit the film by spraying or by immersion. In the latter case both faces of the glass sheet are coated with polyurethane which may be an advantage in certain applications the polyurethane film, because of its elasticity and strength, having the property of retaining broken pieces of glass in the case of fracture of the pane. Further it is possible owing to the film of plastics material to modify the optical properties of the panes which are coated. Thus the film may have anti-UV properties or properties of absorption to infra-red wavelengths.

Further, by colouring the x'ilm of plastics material with a colour complimentary to that of the glass coated with a semireflecting layer, it is possible to obtain an uncoloured product.

Conversely, by colouring the film of plastics material in the same colour as the coated glass, it is possible to reinforce this colour.

Claims (12)

1. A sheet of transparent material provided on at least one of its surfaces v/ith a semi-reflecting metal layer covered v/ith, a protective layer of soft plastics material 5 capable of self-healing after scratching.

2. A sheet according to Claim I, in which the soft plastics material is a partly reticulated polyurethane.

3. „ A sheet according to Claim 2, in which the polyurethahq is prepared from a polyglycol ether resulting 0 from condensation of propylene oxide on triraethylolpropane containing from 10.5 to 12% of free hydroxyl groups (component 1) and a biuret of 1-6 hexamethylenediisocyanate containing from 21 to 22% of isocyanate groups (component 2) the weight ratio of component 2 to component 1 being from 0.9 to 1.1.

4. 5 4. A sheet according to any preceding claim, in which the protective layer of soft plastics material has a thickness from 50 to 1,000 microns. 5. A sheet according to any preceding claim,, in which the protective layer of plastics material is capable of 0 preventing transmission of ultra-violet radiation.

5. 6. A sheet according to any preceding claim, in which the protective film of plastics material is capable of absorbing infra-red radiation. -1043892

6. 7. A sheet according to any preceding claim, in which the protective film of plastics material is coloured with a colour complimentary to that of the transparent material with the semi-reflecting layer. 5

7. 8. A sheet according to any one of Claims 1 to 6, in which the protective film of plastics material is coloured with the same colour as the transparent material with the semi-refleciing layer.

8. 9. A sheet according to any preceding claim, in which

9. 10 the transparent material is mineral glass. 10. A sheet according to any one of Claims 1 to 8, in which the transparent material is a plastics material.

10. 11. A sheet according to Claim 1, substantially as hereinbefore described with reference to Example 1 or 2.

11. 15

12. A window pane, comprising a sheet as claimed in any preceding claim.