MXPA99011849A - Heat reflecting layered system for transparent substrates - Google Patents

Abstract

Heat reflecting system for transparent substrates used in laminated glass manufacture comprises a functional silver-based layer and bottom and top dielectric antireflection layers Bottom antireflection layer comprises at least one metal oxide, especially TiO2, SnO2, Ta2O5, ZnO and Nb2O5. Top antireflection layer comprises AlN and/or Si3N4. A 0.1-1 (preferably 0.2-0.5) nm thick metal or sub-nitride layer (preferably Ti, Zr, Al, Cr, Ni or Hf, or their mixtures, or their sub-nitrides) is located between the silver layer and the top antireflection layer, to promote adhesion. The system preferably includes two silver layers separated by a dielectric antireflection layer formed from a metal oxide corresponding to the bottom antireflection layer, and a 1-2 nm metallic blocking layer is applied below the metal oxide layer directly on the silver layer. The system of layers is preferably as follows:substrate - 25 to 35 nm TiO2 - 8 to 12 nm Ag - 1 to 2 nm Ti - 50 to 60 nm TiO2 - 8 to 12 nm Ag - 0.1-0.5 nm Ti - 35-45 nm AlN. Independent claims are given for:(a) a system of layers of a heat reflecting system for transparent substrates as above except that the bottom antireflection layer comprises metal oxides other than ZnO, such as TiO2, SnO2, ZnO, Ta2O5 or Nb2O5 and a top 5-15 nm thick ZnO part that is next to the silver layer;(b) a flexible polymeric film on at least one face of which is applied the system of layers cited above;and (c) laminated glass incorporating the polymer film cited in (b).

Description

SYSTEM OF LAYERS THAT REFLECT THE HEAT FOR TRANSPARENT SUBSTRATES DESCRIPTION OF THE INVENTION The present invention relates to a system of layers that reflect thermal radiation (solar control or low emissivity) for transparent substrates, comprising at least one functional layer formed of silver and antireflective coatings before dielectric, the antireflection coating The top layer comprises a layer of a metal nitride, in particular A1N, of silicon nitride SÍ3N4, or of a mixed nitride of a metal and of silicon. EP-0 281 048 discloses a stack of layers comprising a functional layer formed of silver, in which both the lower anti-reflective layer and the upper anti-reflective layer are constituted by a metallic nitride, preferably an aluminum nitride. or a silicon nitride. Contrary to metal oxides that serve as antireflective layers before dielectric, metal nitrides have the advantage of presenting a particularly high mechanical and chemical resistance. This known layer system does not have metallic protection layers above the silver layer. Metal protection layers or those obtained by sub-oxidation are generally necessary in the case of antireflection layers obtained by oxidation (sputtering in an oxidizing atmosphere). If not, the silver layer is at risk of being damaged by oxygen during the reactive spraying of the antireflective upper layer. A silver-based layer system comprising dielectric anti-reflective layers of aluminum nitride is also known from the dpcumen, DE 39 41 046 C2. In this layer system, a blocking layer of a thickness of 2 to 20 nm formed of metallic Zn is disposed between the functional layer formed of silver and the antireflective layer deposited thereon. This blocking layer should allow to avoid the risk of a long-term damage to the silver layer by -oxidation. The metallic Zn layer however reduces the light transmission of the layer system, so that this layer system can not be used when a light transmission factor of 75% is necessary, which is the case of vehicle windshields automotive DE 41 35 701 Al discloses a system of layers that reflect thermal radiation, comprising a functional layer formed of silver and anti-reflective layers before dielectric consisting of metal oxides or metal nitrides, in which a blocking layer, formed of two partial layers is applied on the silver layer. This blocking layer is constituted by a first partial layer formed of Pd or Pt, of a thickness of 0.2 to 0.5 nm, deposited directly on the silver layer, and of a second partial layer deposited on the first, and formed of Ti , Cr or a mixture thereof, or an alloy comprising at least 15% of one of these metals, of a thickness of 0.5 to 5 nm. This blocking layer formed of two layers should increase the moisture resistance of the layer system. This, however, requires a supplementary tank chamber in the sputtering installation. In addition, since Pd and Pt are expensive metals, the manufacture of this layer system is expensive. DE 19 52 0843 A1 discloses a layer system consisting of a series of layers comprising a first layer consisting of a metal oxide or a metal nitride, a second layer consisting of a sub-oxide of Zn and / or Ta or of a mixture thereof, a functional layer formed of silver, a fourth metallic layer or metal sub-oxide applied to the silver layer and consisting of one of the metals Ti, Cr, Nb or a mixture of these, or of an alloy comprising one of these metals, and a fifth antireflective upper layer, formed of the material of the first layer. The metallic blocking layer or obtained by sub-oxidation deposited on the silver layer must guarantee the mechanical and chemical resistance of the system. This layer system also comprises a total of five individual layers. Layer systems comprising an antireflective upper layer consisting of a metal nitride, more particularly AlN or Si3N4, are distinguished by their good resistance to corrosion. It has been found, however, that their properties are still not satisfactory from any point of view. The object of the invention is to take advantage of the known advantages of a layer system comprising a superior antireflective layer comprising a metallic nitride, namely its high resistance to corrosion and aging, and to develop a layer system which It comprises this coating layer, and which has still improved properties, particularly related to its mechanical and chemical resistance. To achieve this objective, the invention has developed two alternative or cumulative variants. According to a first variant, the layer system according to the invention is characterized by the fact that the upper anti-reflective layer comprises at least one layer of a metallic nitride, such as, in particular, AlN, Si3N4 or mixed nitride SiAl or SiZn. Preferably, the upper anti-reflective layer is constituted only of this type of material. The lower antireflection layer is made up of one or more of the metal oxides of the type Ti02, Sn02, ZnO, Ta205 or Nb205, it being clear that its upper part, namely the part adjacent to the silver layer, is replaced over a thickness from 5 to 15 nm by ZnO. Preferably, the optical thickness of the partial ZnO layer corresponds to the optical thickness of the part of the metal oxide layer replaced by the partial layer formed of ZnO. In the set of the present text, the term "antireflective layer ante" means that it comprises either a single layer, or an overlap of at least two layers. According to this first variant, the lower "antireflection layer" comprises at least two superposed layers, that of oxide and that of ZnQ, the upper "antireflection layer" comprises at least one. This layer structure favorably influences the structure of the silver layer. Therefore, with the same thickness of the silver layer and the same reflection of infra red radiation, the light transmission is increased. In addition, an improvement in the adhesion of the metallic nitride layer on the silver layer is obtained surprisingly. The performance in the course of the deposit operation and the quality of the layer system, namely more particularly its resistance to corrosion, are also clearly improved. A complementary improvement of the adhesion of the metallic nitride layer on the silver layer can be obtained by the fact that between these two layers a layer formed of Ti, Zr, Al, Cr, Ni or HF is deposited, or of a mixture of these, or of the nitrides thereof, of a thickness of 0.1 to 1 nm, preferably of 0.2 to 0.5 n. According to the second variant of the invention, the lower anti-reflective layer is composed of one or more of the metal oxides of the Ti02, Sn02, ZnO, Ta205 or Nb205 type, and the upper anti-reflective layer comprises at least one layer of AlN, of Si3N or mixtures thereof (mixed nitride SiAl or SiZR). Preferably, it is constituted only of this type of material. In addition, between the silver layer and the upper anti-reflective layer, a layer formed of metal or sub-nitride, preferably from 0.1 to 1 nm in thickness, is designed to improve adhesion. Preferably, the layer formed of metal or sub-nitride intended to improve the adhesion is constituted by Ti, Zr, Al, Cr, Ni or Hf or mixtures thereof, or sub-nitrides thereof. The thickness of this layer intended to improve the adhesion is preferably between 0.2 and 0.5 nm; it is an extremely thin thickness, the layer can be considered as probably discontinuous. The improvement of the long-term strength of the layer system according to the second variant of the invention, verified by the appropriate tests, in relation to the layer systems in which the AlN layers are directly adjacent to the Ag layer, It can be attributed to the fact that a more compact series of layers is obtained. The adhesion and anchoring of the silver layer on the contiguous layer formed of AlN or Si3N are improved. The restructuring of the surface of this anchoring layer, which determines the effect of the anchoring, is clearly formed during the spraying of the following metal nitride layer. On the side adjacent to the silver layer, this anchoring layer has a substantially metallic character, and because of the arrangement of its atoms, it contributes to a good bond with the silver layer. Its structure is modified on the surface by the formation of nitrides (a certain nitriding) that allows a better union with the nitride layer. There is no problem in that the antireflection layer at the bottom is constituted by a metal oxide, at least before a metal nitride. In fact, the resistance to the possibly weaker moisture of the metal oxide is compensated for by the fact that the metal oxide adheres better to the silver layer than the metal nitrides. The aforementioned metal oxides are allowed to spray well. They also have a favorable influence on the optical properties of the layer system, so that the layer system according to the invention altogether has substantially improved properties. The layer system according to one or other of the variants of the invention is particularly suitable for the coating of transparent films of flexible polymer, of the polyethylene terephthalate (PET) type, intended for the manufacture of laminated crystals. The coated films are assembled to two glass sheets by means of thermoplastic adhesive sheets, consisting in particular of polyvinyl butyral (PVB) or polyurethane (PU). When other layer systems tend, during a direct contact with the adhesive sheets of this type, to show signs of aging under the influence of ultraviolet rays, such signs are not observed in the layer systems according to the invention, which is very advantageous The industrial manufacture of the layer system is preferably carried out by sputtering assisted by a magnetic field in continuous sliding tank installations. For the antireflective layers before dielectric, the spray is reactive with a percentage of 02 or, as the case may be, of N2 as working gas, for respectively the nitrogen or nitride layers. In view of the fact that certain metals can only be sprayed at a relatively small spraying rate, modern spraying techniques, such as rotary sputtering or double cathode sputtering, are the preferred choice for this type of spraying. material.

Of course, the layer system according to the invention can also comprise two functional layers based on silver, separated one from the other by ung. dielectric layer. Providing two layers of silver instead of one allows particularly to obtain a better selectivity (better compromise between the level of light transmission and the thermal properties sought, which are either a control of the solar contribution, or a low emissivity). The "intermediate" dielectric layer disposed between the two layers of silver can thus comprise a single layer or several layers. It can be in accordance with the first variant of the invention, that is to say, "replaced" by ZnO of thickness from 5 to 15 n in its part adjacent to the second silver layer. In fact, in the presence of two layers of silver, at least one of them must respect one of the variants at least of the invention; have a layer of ZnO directly under it, and / or be covered with a thin metallic layer optionally nitrided.

Advantageously, the two layers of silver follow these conditions. However, it is preferable to provide a blocking layer above the first layer of silver (sacrificial) of metallic type, of thickness for example from 1 to 3 nm, to avoid its deterioration in the case in which a metal oxide layer must be sprayed on top of it. The invention will now be detailed with the aid of non-limiting embodiments: EXAMPLES 1 4 These examples are in accordance with the first variant of the invention, using substrates in the form of PET films. The embodiments of a layer system according to the invention are described below, and the improvement obtained on the layers is demonstrated by a comparison with a layer system without intermediate ZnO layer. The layer systems are increasingly sprayed on transparent PET films with a thickness of 50 μm. the coated PET films are incorporated between two thermoplastic sheets of polyvinyl butyral (PVB), each having a thickness of 0.38 mm, and transformed in a known manner into laminated glass from these sheets of PVB, under the application of heat and pressure in an autoclave under pressure. On samples of laminated glass prepared in this way, with a size of 30 x 30 cm2, the tests mentioned below are carried out to determine the chemical resistance: - Test A: Spray test of saline mist according to DIN 50021. - Test B: Test of Kesternich according to DIN 50018. - Test C; Moisture test according to ANSI Z 26.1 After having carried out each test, the length of the corroded layer is measured on the edge. The length of the corroded layer is a measure of the resistance of the layer to corrosion. So that the layer system can be used for its application in composite crystals, the samples can not present more than one corrosion of a maximum of 3 mm in length over the edge during each test. In most of the tests indicated for the determination of the corrosion resistance, what is called a detachment test is carried out according to ANSI Z 26.1 and ECE R43 (Test D) that allows an opinion on the cohesion of the partial layers of the layer system. This detachment test consists of not associating the coated PET sheet with more than two sheets of PVB. The procedure described for manufacturing a composite glass under the application of heat and pressure is then used, but between the adjacent crystals and sheets of PVB, a separating sheet is inserted each time, so that after pressing and lifting the crystals and separating sheets, a stratified material of PVB-PET-VB is obtained. In the peel test, the PVB sheet adjacent to the layer system is thus separated from one end, and is folded and removed from the coated PET sheet under a force application angle of 180 degrees. The force required to tear off the PVB sheet is a measure of the adhesion of the PVB sheet to the layer system and the cohesion of the partial layers of the layer system.

COMPARATIVE EXAMPLE 1 The layer system of the comparative example has the construction: 30 nm of Ti02 - 10 nm of Ag - 40 nm of AlN.

EXAMPLE 1 SEC N THE INVENTION The layer system embodiment example has the sequence: 20 nm of Ti02 - 12 nm ZnO - 10 nm of Ag - 40 nm of AlN. The pulverization of the different partial layers on the PET sheet is carried out under otherwise identical spray conditions. The results of the tests carried out are shown in the table below. The results of the D test represent the average value of five measurements.

The comparison between the results of the test shows that not only a considerable increase in the detachment force is observed, but also shows an improvement in the result of the salt fog nebulization test. The analytical study of the surfaces of the PVB sheet and the coated PET sheet of the comparative example and of the exemplary embodiment, carried out after the peel test, indicates on the other hand that on the surface of the PVB sheet, no it is found more than AlN, whereas, although Ag and Ti are found on the layer of the PET sheet, there are nevertheless more than traces of AlN. It can be concluded that the increase in the release force does not derive from a higher adhesion of the AlN to the PVB sheet, but rather from a better anchoring of the AlN layer on the silver layer.

EXAMPLE 2 It has the following sequence of layers: PET substrate - 30 nm of Ti02 - 12 nm of ZnO - 10 nm of Ag - 1 nm of Ti - 46 nm of Ti02 - 12 nm of ZnO - 10 nm of Ag - 40 n , from AlN.

EXAMPLE 3 It has the following sequence of layers: PET substrate - 30 nm of Ti02 - 13 nm of ZnO - 10 nm of Ag - 20 n of AlN - 31 nm of Ti02 - 12 nm of ZnO - 10 nm of Ag - 40 nm of AlN.

EXAMPLE 4 It has the following sequence of layers: PET substrate - 30 nm of Ti02 - 12 nm of ZnO - 10 nm of Ag - 1 nm of Ti - 46 nm of Ti02 - 12 nm of ZnO - 10 nm of Ag - 0.2 nm of Ti - 40 nm of AlN. It has the particularity of combining the two variants of the invention. These latter examples also show an improvement of the same type as Example 1. Their resistance to corrosion is much better than the layer stacks of the state of the art.

EXAMPLES 5 AND 6 These examples follow the second variant of the invention. They are made in comparison with the comparative example 1 explained above. They are made as before (deposit then assembled with two sheets of PVB to two sheets of glass).

Example 5: The layer system of this example presents the sequence: 30 nm of Ti02 - 10 nm of Ag - 0.5 nm of Ti - 40 nm of AlN the results of the tests carried out are shown in the Table below. The results of test D represent in each case the average value of five measurements.

The comparison between the results of the test shows that not only a considerable increase of the detachment force is observed, but also a surprising improvement of the corrosion resistance for both the salt fog nebulization test and the Kesternich test. The analytical study, in each case after the peeling test, of the surfaces of the PVB sheet and the PET sheet coated with comparative example 1 and of the embodiment 5 indicates on the other hand that on the surface of the sheet of PVB, np is found more than AlN, whereas, although Ag and Ti are found on the layer of the PET sheet, there are nevertheless more than traces of AlN. As the AlN consequently presents a high adhesion to the surface of the PVB, the values measured during the peel test provide an immediate conclusion about the adhesion between the AlN layer and the silver layer.

Example 6: The following layer system, which makes laminated glass with a transmission in the visible spectrum greater than 70%, was found to be equally effective. It uses two layers of silver: PET substrate - 30 nm of Ti02 - 10 nm of Ag - 1 nm of Ti - 56 nm of Ti02 - 10 nm of Ag - 0.2 nm of Ti - 40 nm of AlN. In conclusionThe two variants of the invention have the purpose of reinforcing the adhesion of the silver layer (s) to the other layers of the stack, very particularly to the advantageous nitride layers, but which in a known manner have an unsatisfactory adhesion to the silver The invention thus provides an anchoring layer, at the interface between the silver and the nitride, and / or more surprisingly, a ZnO layer under the silver. Another original feature of the invention is to provide, preferably in the case of a single layer of Ag, under the silver rather than the oxide layers, and over the silver rather than the nitride layers. In the case of the two Ag layers, it is preferred to provide oxide layers under the first Ag layer. Above the second layer of Ag (the furthest away from the substrate), nitride layers are preferably provided. And between the two layers of silver, you can have dielectrics exclusively in the form of metal oxide or exclusively in the form of nitride, or associating these two types of materials. It is thus possible to have an intermediate dielectric having the AlN / oxide sequence, particularly A1N / Ti02 or A1N / Ti02 / Zn0.

Claims (18)

1. CLAIMS 1. System of layers that reflect thermal radiation for transparent substrates, comprising at least one functional layer based on silver and anti-reflective layers before dielectric, characterized in that the lower antireflection layer comprises one or more metal oxides, particularly Ti02, Sn02 , ZnO, Ta205 or b205, and because the upper antireflective layer comprises AlN, Si3N4 or mixtures of these, and because between the silver layer and the upper antireflective layer there is a layer formed of metal or sub-nitride, a thickness of preferably 0.1 to 1 nm, and intended to improve adhesion.
2. 2. Layer system according to claim 1, characterized in that the layer intended to improve the adhesion is formed of Ti, Zr, Al, rj Ni or Hf, or a mixture thereof, or sub-nitrides thereof.
3. 3. Layer system according to claim 1 or 2, characterized in that the layer intended to improve the adhesion has a thickness comprised between 0.2 and 0.5 nm.
4. 4. Layer system according to any of claims 1 to 3, characterized in that it comprises two layers of silver separated one from the other by a dielectric anti-reflective layer.
5. 5. Layer system according to claim 4, characterized in that the dielectric anti-reflective layer applied between the layers of p ^ ata is formed of a metal oxide corresponding to the lower anti-reflective layer, and because a metallic blocking layer is applied below the This layer of metal oxide directly on the silver layer.
6. 6. Layer system according to claim 5, characterized in that the metallic blocking layer applied on the silver layer has a thickness of about 1 to 2 nm.
7. 7. Layer system according to claim 6, characterized by the following series of layers: substrate - 25 to 35 nm of Ti02 - 8 at 12 nm of Ag - 1 at 2 nm of Ti - 50 at 60 nm of Ti02 - 8 a 12 nm of Ag - 0.1 to 0.5 nm of Ti-35 at 45 nm of AlN.
8. System of layers reflecting thermal radiation for transparent substrates, comprising at least one functional layer formed of silver and anti-reflective layers before dielectric, the upper antireflection layer comprises a metallic nitride, such as AlN or SÍ3N4, and the lower anti-reflective layer comprises one or more of the metal oxides other than ZnO, of the type of Ti02, Sn02, ZnO, Ta205 or Nb205, its supexorous part, namely the part adjacent to the silver layer, is replaced by ZnO over a thickness of particularly 5 to 15 nm.
9. 9. Layer system according to claim 8, characterized in that the optical thickness of the partial layer formed of ZnO corresponds to the optical thickness of the part of the oxide layer replaced by the partial layer of ZnO.
10. 10. Layer system according to claim 8 or 9, characterized in that between the upper anti-reflective layer consisting of metallic nitride and the silver layer is formed a layer formed of metal or metal nitride, of a thickness of 0.1 to 1 nm, preferably from 0.2 to 0.5 nm which improves adhesion.
11. 11. Layer system according to claim 10, characterized in that the layer intended to improve the adhesion is formed of Ti, Zr, Al, Cr, Ni or Hf, or mixtures thereof, or sub-nitrides thereof.
12. 12. Layer system according to any of claims 8 to 12, characterized in that it comprises two layers of silver separated one from the other by an intermediate dielectric antireflection layer whose upper part, namely the part (± straight next to the second layer of silver, is also replaced by a layer of ZnO.
13. 13. Layer system according to claim 8, characterized in that the intermediate dielectric antireflection layer is formed from the series of metal-metal oxide-ZnO nitride layers, more particularly from the layer series A1N-Ti02-ZnO.
14. 14. Layer system according to claim 12 or 13, characterized in that a metal blocking layer is applied below the intermediate antireflection layer, directly on the first silver layer.
15. 15. Layer system according to claim 14, characterized in that the metallic blocking layer has a thickness of 1 to 3 nm.
16. 16. Layer system according to any of the preceding claims, characterized in that a polymer of the polyethylene terephthalate type is applied on a transparent film, which is assembled by means of thermoplastic adhesive sheets with two glass substrates to form a laminated glass .
17. 17. Flexible polymer film, characterized in that one of its faces of the layer system according to any of the preceding claims is provided on the underside.
18. 18. Laminated glass, characterized in that it incorporates the polymer film according to claim 17.