Method of making a heat treated coated glass

Abstract: A method of making a heat treated coated glass comprising the steps of: forming a solar control layer (1)or an electroconductive layer (1) on a glass substrate (4); forming a first protective layer (2) composed of a non-oxide or not completely oxidized, which is transparent in a region of visible light, and which remains transparent even when oxidized, to provide a glass coated with a multi-layer comprising at least two layers including said solar control layer (1) or an electroconductive layer (1) and said first protective layer (2); and performing heat-treatment for said coated glass.

Description: This invention relates to a method of making a heat treated coated glass, particularly to a method of making a heat treated coated glass which minimizes changes of characteristics thereof before and after bending thereof. Conventionally, a bent coated glass is made by performing a coating on a glass which is already bent. Or, it is made by bending a glass coated with a metallic film or a metal nitride film to be protected which is sandwichingly covered with an easily oxided metal such as tantalum, and in bending thereof, the easily oxided metal is mainly oxided, thereby protecting the film to be protected. Or, it is made while preventing the oxidation of the film to be protected by maintaining a nonoxidizing atmosphere during the bending. Among the above technologies, in the method of coating the bent glass, it is not possible to perform a uniform coating on the bent glass, unless the coating process and the coating condition are controlled complying with a configuration of the bent glass. Accordingly, it is difficult to obtain products thereof provided with the high quality and the uniform performance. On the other hand, in the method of sandwiching the layer to be protected by the easily oxided metal, characteristics of the coated glass change before and after the bending. Therefore, in a plane glass which shares the same characteristics with the obtained bent glass, a different film construction should be prepared, or a heat treatment which is the same with that in the bending should be performed. Accordingly, a considerable extravagance is present in the product control. Moreover, in the method of maintaining the nonoxidizing atmosphere during bending, revamping of a normal bending device is necessitated, which increases the production cost. As the heat treating of glass, tempering is generally performed which is similar to bending. With respect to a tempered coated glass, the situation is the same as in the bent coated glass. It is an object of the present invention to provide a method of making a heat treated coated glass wherein a coated plane glass having an excellent uniformity is made by employing a normal coating technology to a plane glass at a low cost, and bending and/or tempering which is generally easily performed is performed thereon without the necessity of an atmosphere control and by heating thereof in the normal oxygen-containing atmosphere, with almost no change of the coated layer to be protected which mainly influences optical characteristics thereof. This object is achieved by the method of claim 1. Preferable embodiments are defined in claims 2 to 6. In the drawings: Figure 1 is a sectional diagram of an example of heat treated coated glass which is made by the present invention, Figures 2 and 3, sectional diagrams showing other examples of heat treated coated glass according to the present invention. In these Figures, a reference numeral 1 designates a solar control layer, 2, a first protective layer, 3, a second protective layer and 4, a glass substrate. In the present invention, as the solar control layer 1, a film provided with a solar energy absorbing function having a light absorption characteristic at least with respect to a portion of a region of wave length of the solar ray, or a film provided with a light reflection characteristic mainly with respect to a region of near infrared ray, or the like can be used. Specifically, a film whose major component is at least one of stainless steel, titanium, chromium, zirconium, tantalum and hafnium (hereinafter, defined as metal M), a nitride of the metal M, a boride of the metal M, a carbide of the metal M or a mixture of these, or a film whose major component is aluminium is used according to the invention. In case of the nitride, the boride, the carbide or the like, a thickness thereof is preferably approximately from 100Å to 800Å to obtain the solar control property. In case of the aluminum metal film, the film thickness is preferably 20Å to 300Å. This is invention is applicable to an electroconductive layer whose carriers are caused from the oxygen vacancies, in place of the solar control layer. As the examples of materials of such films, an indium oxide doped with tin, a tin oxide doped with antimony or fluorine, or a zinc oxide doped with aluminum, boron or silicon, etc., can be pointed out. Moreover, ZnO, TiO 2 , SnO 2 , ThO 2 , V 2 O 5 , Nb 2 O 5 , Ta 2 O 5 , MoO 3 , WO 3 , MnO 2 , PbCrO 4 , are also the examples of the materials of the above electroconductive layer. Hereinafter "solar control layer" represents not only the above solar control layer but also the above electroconductive layer in this specification. The first protective layer 2 is a film which prevents diffusion of oxygen into the solar control layer 1 even when it is heated in the heat treatment, or, which does not discharge oxygen to the solar control layer 1 even when the first protective layer 2 per se contains oxygen. Since in the first protective film, only the refractive index thereof changes, the change of absorption is not caused and a transparency thereof is maintained even when it is oxidized, no considerable influence is applied on the optical characteristics thereof after the heat treatment. The most preferable example of the first protective layer 2, is a film whose major component is at least one of a boron nitride, a carbon nitride and a silicon nitride. Especially, a representative example is a film whose major component is a nitride of silicon or boron, or a film whose major component is a nitride of at least two of silicon, boron, aluminium, zirconium and tin, particularly a film of a zirconium siliconitride, a film of tin siliconitride or the like. Or, it may be a film whose major component is a partially oxided substance of the nitride, the boronitride, the carbonitride, the siliconitride and the like. Among these, the silicon nitride and the zirconium siliconitride are particularly provided with an excellent oxygen barrier performance. In the film of the nitride or the like as the above-mentioned first protective film, the invention is applicable thereto so far as it is transparent in the visible light region, even when the nitride is not bonded in the most general stoichiometrical ratio. For instance, in case of the silicon nitride, Si 3 N 4 is the general composition. However, this invention is applicable so far as the film is transparent in the visible light region. The atomic ratio of N to Si is preferably 1.25 or more, because the silicon nitride film is transparent in the visible light region. When the second protective layer 3 is formed as an outermost layer, the thickness of the first protective layer 2 depends on the oxygen barrier performance, and is determined in consideration of a quantity of oxygen which is diffused inside through the second protective layer. In the normal heat treatment, the thickness is preferably at least about 10Å, particularly 20Å or more. In this invention, the effect of the invention can be provided even when the second protective film is not formed and the first protective film is formed with a thickness of the film which is thick to some degree. The film thickness should be determined in consideration of a film thickness of a portion of the film of which is oxidized in the heat treatment. The second protective layer 3 is preferably composed of a metal oxide, is a transparent film in the visible light region, and provided with a high oxygen barrier performance. Specifically, an oxide such as a tin oxide, a zinc oxide, a zirconium oxide, a tantalum oxide, a niobium oxide, a titanium oxide, a silicon oxide or the like is pointed out as the metal oxide. The thickness of the second protective layer 3 is determined in consideration of the thickness of the first protective layer 2, and the optical characteristics in view of a total of the coated glass and the like. In the present method, it is preferable to form a film which displays the same function with that in the first protective film, between the solar control film 1 and the glass substrate 4, to shield oxygen diffused from the glass substrate in a very small quantity, that is, a non-oxide film or a film that is not completely oxidized, which is transparent even when it is oxidized, as a first underlayer 5, as shown in Figure 2. As the materials of such first underlayer 5, the materials described for the first protective layer 2 can be similarly used. In this invention, the solar control layer 1 to be protected can be perfectly protected from the oxidation during the heating process for bending and/or tempering, by the first protective layer 2, and, in some cases, by the first protective layer 2 together with the first underlayer 5. Furthermore, in the invented method, a film may be formed as a second underlayer 6 which is composed of a metal oxide and is transparent, between the glass substrate 4 and the first underlayer 5, as shown in Figure 3, to obtain a desired optical characteristic (transmittance, reflectance, color tone etc.) by employing interference of light, or to promote the durability such as the adherence. As the second underlayer 6, the film exemplified as the first protective layer can be utilized. In this invention, the change of characteristics of the coated layers can be minimized, because the two metal oxide layers of the second protective layer 3 and the second underlayer 6 which have no change during the heating decrease the oxygen diffusing to the first protective layer 2 and first underlayer 5 which absorb said oxygen and change only their refractive indices. Furthermore, without being restricted by these films, a desired film may be formed between the glass substrate 4 and the first underlayer 5. The glass substrate 4 is not particularly restrained. Various glass plates such as a soda-lime glass plate or a heat ray absorbing glass plate can be employed. The bending method as the heat treatment is a method wherein coated glass is heated at approximately 580 to 700°C (which temperature depends on the composition of a glass) in the atmosphere and is bent. Naturally, it may be bent in a nonoxidizing atmosphere. However, in that case revamping of a device or the like is necessary and the production cost is increased. The tempering method as the heat treatment is a method wherein coated glass is heated at approximately 500 to 700°C in the atmosphere and rapidly cooled. It is possible to perform the tempering continuously successive to the bending. The tempering may be a full-tempering or a semi-tempering. In the heat treated coated glass, there may be caused almost no change in the composition of the first protective layer, since the oxidation thereof is not promoted in case wherein the oxygen barrier performance of the second protective film is excellent. However, the first protective layer often contains oxygen more than that before the heat treatment, since the oxidation thereof is promoted by the heating in the heat treatment. In some cases, it is converted into an oxide by discharging nitrogen or carbon in the first protective layer in the heat treatment. Or, when the second protective layer is not formed, some degree of oxidation is promoted from the surface of the first protective layer but the first protective layer is in a state wherein the oxidation thereof is not performed to a portion adjacent to the solar control layer. The solar control layer 1 which covers glass, is normally oxidized in the heat treatment by oxygen in an atmospheric gas (the atmosphere) which is diffused to the inside thereof through the film protecting the solar control layer 1 and by a combined oxygen in the contiguous oxide film, thereby considerably changing the optical characteristics thereof, particularly the heat ray shielding function, the visible light transmittance and the like (the electroconductivity in case of an electroconductive layer). In this invention, as the second protective layer 3 for the protection, one which is provided with an excellent oxygen barrier performance is selected thereby considerably reducing the oxygen diffusing inside thereof. Furthermore, the first protective layer 2 is provided between the second protective layer 3 and the solar control layer 1. Accordingly, the first protective layer 2 mainly reacts with the oxygen diffused inwardly through the second protective layer in a very small amount or the combined oxygen in the second protective layer, thereby preventing the diffused oxygen and the combined oxygen to reach the solar control layer 1 to be protected. Therefore, the solar control layer 1 suffers almost no change. Furthermore, even when the second protective layer 3 is not formed, the first protective layer sufficiently absorbs the oxygen from the atmosphere during the heat treatment and plays a role of an oxygen barrier. Therefore, the solar control layer 1 suffers almost no change. Since the solar control layer 1 suffers almost no change in view of a total of the multi-layer coated on glass, although the refractive index of the first protective layer changes more or less, as a total of the film, there causes no change in the optical characteristics which takes place in the conventional heat treatment. EXAMPLE 1 A reactive sputtering is performed on the plane glass substrate 4 employing a tin target in a mixture of oxygen and argon gases, thereby forming the second underlayer 6 (250Å) composed of a tin oxide. Next, another reactive sputtering is performed thereon employing a zirconium silicide alloy target in nitrogen gas, thereby forming the first underlayer 5 (50Å) composed of a zirconium siliconitride. Next, a third reactive sputtering is performed thereon employing a chromium target in nitrogen gas thereby forming the solar control layer 1 (100Å) composed of a chromium nitride. Thereafter, the first protective film 2 (50Å) composed of a zirconium siliconitride similar to the first underlayer 5, and the second protective film 3 (300Å) composed of a tin oxide similar to the second protective layer 6 are formed. In this way, a coated glass having the construction as shown in Figure 3, is provided. The plane coated glass is put into an electric furnace wherein it is heated at about 630°C in the atmospheric environment and the bending thereof is performed. There is no change in the solar control layer 1, the second protective layer 3 and the second underlayer 6 after the bending as compared with those before the bending. The first protective film 2 and the first underlayer 5 after the bending are partially oxidized. The optical characteristics of the coated glass before and after the heating are shown in Table 1. COMPARATIVE EXAMPLE 1 A tin oxide layer (250Å), a chromium nitride layer (100Å) and a tin oxide layer (300Å) are successively formed on a plane glass substrate by the sputtering method similar to Example 1. The heat treatment similar to that in Example 1 is performed on the obtained plane coated glass and the optical characteristics before and after the heating are measured. The result is shown in Table 1. COMPARATIVE EXAMPLE 2 A chromium nitride layer (100Å) is formed on a plane glass substrate by the sputtering method similar to that in Example 1. The heat treatment similar to that in Example 1 is performed on the obtained plane coated glass. The optical characteristics before and after the heating thereof are shown in Table 1. Color coordinate according to CIE 1931 (XYZ) Color difference before & after heating according to CIE 1976 (L*u*v*) Visual light transmittance: Y x y Coated glass of Example 1 Before bending 44.7% 0.299 0.307 - After bending 46.0% 0.297 0.306 1.67 Coated glass of Comparative Example 1 Before bending 46.9% 0.304 0.309 - After bending 51.8% 0.308 0.312 3.97 Coated glass of Comparative Example 2 Before bending 30.4% 0.317 0.323 - After bending 78.6% 0.314 0.321 29.19 EXAMPLE 2 A coated glass as in Figure 3 (that is, a coated glass having a construction of glass substrate/tin oxide layer (320Å)/silicon nitride layer/chromium nitride layer (136Å)/silicon nitride layer/tin oxide layer (280Å)), is obtained by a method similar to Example 1 except that the silicon nitride layers are formed as the first underlayer 5 and the first protective layer 2, by performing a reactive sputtering employing silicon targets in nitrogen gas. The changes of the optical characteristics are shown in Table 2, in cases wherein the heat treating temperature is varied with respect to three kinds of film thicknesses, namely 30Å, 20Å and 0Å (that is, a case wherein the silicon nitride is not formed) of the silicon nitride layers as the first underlayer 5 and the first protective layer 2. The atomic ratio of nitrogen to silicon in the silicon nitride layers in Example 2 was 1.35. By the comparison of the results of Example 1, Comparative Examples 1 and 2, and Table 2, it is found that the coated glass of this invention suffers little change with respect to the optical characteristics thereof in the heat treatment in the atmosphere and the significance of the invented method is clarified. Film thickness of silicon nitride (Å) Heating temperature (°C) Color coordinate according to CIE 1931 (XYZ) Color difference before & after heating according to CIE 1976 (L*u*v*) Visible light transmittance: Y (%) x y 30 Before heating 48.57 0.2973 0.3207 - 530 48.39 0.2975 0.3186 1.46 600 49.15 0.2976 0.3186 1.51 620 49.91 0.2987 0.3201 1.45 640 49.73 0.2981 0.3189 1.69 660 48.80 0.2987 0.3193 1.59 20 Before heating 51.44 0.2999 0.3225 - 530 51.13 0.2992 0.3198 1.67 600 51.04 0.3010 0.3210 1.74 620 53.85 0.3007 0.3209 1.93 640 53.69 0.3008 0.3207 2.02 660 51.56 0.3035 0.3226 2.50 0 Before heating 46.67 0.2962 0.3170 - 530 49.58 0.2996 0.3185 2.70 600 51.04 0.3001 0.3185 3.50 620 52.01 0.3000 0.3192 3.92 640 53.20 0.3002 0.3192 4.57 660 54.58 0.3003 0.3190 5.27

Claims: A method of making a heat treated coated glass comprising the steps of (a) forming on a glass substrate (i) a solar control layer wherein the major component of the layer is at least one metal (hereinafter defined as metal M) selected from stainless steel, titanium, chromium, zirconium, tantalum and hafnium, or a nitride of the metal M, or a boride of the metal M, or a carbide of the metal M, or a mixture of these, or wherein the major component of the layer is aluminum, or an electroconductive layer wherein the material of the layer is an indium oxide doped with tin, a tin oxide doped with antimony or fluorine, or a zinc oxide doped with aluminum, boron, or silicon, or wherein the material of the layer is ZnO, TiO 2 , SnO 2 , ThO 2 , V 2 O 5 , Nb 2 O 5 , Ta 2 O 5 , MoO 3 , WO 3 , MnO 2 , or PbCrO 4 ; and (ii) a first protective layer whose major component is at least one selected from the group consisting of a boron nitride, a silicon nitride, a boronitride, a siliconitride, and a carbonitride; or a nitride of at least two selected from the group consisting of silicon, boron, aluminum, zirconium and tin, which may be incompletely oxidized, which is transparent in a region of visible light, and which remains transparent even when oxidized, to provide a glass coated with a multi-layer comprising at least two layers including said solar control layer or electroconductive layer and said first protective layer; and (b) performing heat-treatment for said coated glass, (b1) wherein the coated glass is heated at 580 to 700°C and bent, or (b2) wherein the coated glass is heated at 500 to 700°C and rapidly cooled for tempering, or (b3) wherein the tempering (b2) is performed continuously successive to the bending (b1). A method of making a heat treated coated glass according to claim 1 wherein (iii) a second protective layer which is composed of a metal oxide and is transparent, is formed on the first protective layer, to provide a glass coated with a multi-layer composed of at least three layers including the solar control layer, or an electroconductive layer, the first protective layer and said second protective layer, and then a heat-treatment is performed for said coated glass. The method of making a heat treated coated glass according to Claim 2, wherein the second protective layer is a film having an oxygen barrier performance. The method of making a heat treated coated glass according to Claim 2, wherein the second protective layer is a film whose major component is at least one selected from the group consisting of a tin oxide, a tantalum oxide, a titanium oxide, a niobium oxide, a titanium oxide and a silicon oxide. A method of making a heat treated coated glass according to claim 1 wherein (iv) a first underlayer composed of a non-oxide or not completely oxidized, and which remains transparent even when oxidized, is formed on the glass substrate before the solar control layer or the electroconductive layer is formed on the glass substrate. The method of making a heat treated coated glass according to Claim 5, wherein a second underfayer which is composed of a metal oxide and is transparent, is formed on the glass substrate before said first underlayer is formed on the glass substrate.

Inventors: KOJIMA HIROYASU, OHSAKI HISASHI, SUZUKI KOICHI, KOJIMA, HIROYASU, OHSAKI, HISASHI, SUZUKI, KOICHI, KOJIMA, HIROYASU, ASAHI GLASS COMPANY LTD., OHSAKI, HISASHI, ASAHI GLASS COMPANY LTD., SUZUKI, KOICHI, ASAHI GLASS COMPANY LTD.
Applicants: ASAHI GLASS CO LTD, ASAHI GLASS COMPANY LTD.
Application year: 1992
Main classification: C03C17
IPC codes: C03C17