GB2437521A

GB2437521A - Method of manufacturing a differentially coloured glass article

Info

Publication number: GB2437521A
Application number: GB0610959A
Authority: GB
Inventors: Peter G Kazansky; Isabel C S Carvalho; Koichi Sakaguchi; Mitsuhiro Kawazu
Original assignee: University of Southampton
Current assignee: University of Southampton
Priority date: 2006-04-28
Filing date: 2006-06-02
Publication date: 2007-10-31
Anticipated expiration: 2026-06-02
Also published as: JP4773872B2; GB0610959D0; JP2007297235A; GB2437521B

Abstract

Methods for manufacturing differentially coloured glass articles 3 are described. The methods allow the level of colouring, achieved via minute metal particles 4, to be lowered by using less energy. A glass article 3 to which voltage is applied includes a glass plate 2 and a film 1, where the electrical conductivity of the glass plate 2 is larger than that of the film 1. The film 1 contains minute metal particles 4. The method comprises applying a voltage to the glass article 3 while the film 1 and the glass plate 2 are arranged between an anode 5 and a cathode 6, as a result, at least part of the minute metal particles 4 contained in the film 1 are ionised in a voltage application region 9. The minute metal particles may be gold, platinum, silver or palladium nanoparticles and can be applied via a sol-gel method.

Description

1 2437521

METHOD FOR MANUFACTURING GLASS ARTICLE

The present invention relates generally to a method for manufacturing a glass article including regions that are different from each other in level of colouring, particularly a glass plate coated with a film including regions that are different from each other in level of colouring.

A method in which minute metal particles are dispersed in glass is known as a method for manufacturing coloured glass. With the method, coloured glasses having various colour tones can be manufactured through the selection of the glass composition or the kind and amount of the minute metal particles to be dispersed therein.

The technique of lowering the level of colouring of such coloured glass in which minute metal particles have been dispersed is disclosed in "Poling-Assisted Bleaching Of Metal-Doped Nanocomposite Glass", Oliver Deparis et al., Applied Physics Letters, vol. 85, No. 6, 872-874(2004) (Reference 1). Reference 1 describes that a voltage is applied to soda-lime glass containing minute colloidal silver particles so as to induce an electric field inside the glass, and thereby silver that exists in the portion in which the electric field has been induced is ionised to be dissolved in the glass, which allows the level of colouring to be lowered. The method disclosed in Reference 1 allows glass having at least two regions that are different from each other in level of colouring to be obtained by applying a voltage to a predetermined region of coloured glass. For instance, a glass article can be manufactured in which coloured regions and non-coloured regions (decolourised regions) are patterned.

The method described in Reference 1 allows the level of colouring to be lowered by ionising minute metal particles. However, the magnitude of the voltage to be required for the ionisation depends on the degree to which the metal forming the minute particles tends to be ionised. On the other hand, minute particles made of palladium, platinum, gold, etc. that are more difficult to ionise than silver also are used as the minute metal particles for obtaining coloured glass. In order to ionise such minute particles, application of a higher voltage, i.e. higher energy is required, and therefore the ionisation is difficult to be carried out by the method described in Reference 1.

Hence, an object of the present invention is to provide a method for manufacturing a glass article including regions that are different from each other in level of colouring. This method is a manufacturing method that allows the level of colouring that is achieved with minute metal particles to be lowered by using less energy than that required in the method disclosed in Reference 1.

A first method for manufacturing a glass article of the present invention is a method for manufacturing a glass article that includes a first region and a second region. The first region is coloured with minute metal particles and the second region is less coloured than the first region. The method includes applying a voltage to a predetermined region of the glass article to be the second region so as to ionise at least part of the minute metal particles included in the predetermined region. The glass article to which the voltage is applied includes a glass plate and a film that is formed on the glass plate. The electrical conductivity of the glass plate is larger than that of the film. The film includes the minute metal particles. In the first manufacturing method of the present invention, the voltage is applied to the glass article while the glass plate and the film are arranged between an anode and a cathode for applying the voltage. Thus at least a part of the minute metal particles contained in the film is ionised in the predetermined region.

A second method for manufacturing a glass article of the present invention is a method for manufacturing a glass article that includes a first region and a second region. The first region is coloured with minute metal particles and the second region is less coloured than the first region. The method includes applying a voltage to a predetermined region of the glass article to be the second region so as to ionise at least part of the minute metal particles included in the predetermined region. The glass article to which the voltage is applied includes a glass plate and a film that is formed on the glass plate. The glass plate contains an alkali metal element. The content of the alkali metal element included in the glass plate is larger than that of an alkali metal element included in the film. The film includes the minute metal particles. In the second manufacturing method of the present invention, the voltage is applied to the glass article while the glass plate and the film are arranged between an anode and a cathode for applying the voltage. Thus at least a part of the minute metal particles contained in the film is ionised in the predetermined region.

According to the manufacturing methods of the present invention, a voltage is applied to a glass article which includes a film containing minute metal particles that has been formed on a glass plate. Thus, at least a part of the minute metal particles contained in the film in the region to which the voltage has been applied, i.e. the region in which the electric field has been induced, and thereby the level of colouring of the region can be lowered.

In the first manufacturing method, it is necessary that the electrical conductivity of the glass plate is larger than that of the film containing minute metal particles.

In the second manufacturing method, it is necessary that the glass plate contains an alkali metal element, and the content of the alkali metal element included in the glass plate be larger than that of an alkali metal element included in the film. The alkali metal element contained in glass generally increases electrical conductivity, the electrical conductivity includes the ion conductivity, of the glass. Accordingly, when the glass plate and the film are compared to each other, the electrical conductivity of the glass plate is larger than that of the film.

When a voltage is applied to a layered product including such layers that are different from each other in electrical conductivity, the voltage further can be concentrated on the layer having a relatively smaller electrical conductivity, i.e. the film, so that the strength of the electric field to be induced in the film that is a layer containing minute metal particles can be increased through application of a voltage to the glass article. That is, as compared to such a method as disclosed in Reference 1 in which a voltage is applied to bulk glass containing minute metal particles, the level of colouring achieved through the ionisation of minute metal particles can be lowered by using less energy.

Furthermore, according to the manufacturing methods of the present invention, minute particles formed of palladium, platinum, gold, etc., which are difficult to ionise by the conventional method, can be ionised more easily.

The present invention will be explained with reference to the following drawings: FIG. 1 is a schematic view that is used for explaining an example of the methods for manufacturing a glass article according to the present invention; FIG. 2 is a schematic view showing an example of glass article manufactured by the methods for manufacturing a glass article according to the present invention; and FIG. 3 is a graph showing the change in absorption spectrum that was obtained in a voltage application region of Sample 1 before and after application of a voltage, which was evaluated in Example.

In the first manufacturing method, a voltage may apply to a glass article including a glass plate and a film, that are stacked together, having compositions that exhibit different conductivities from each other.

For example, the glass plate and the film may have compositions in which the glass plate contains an alkali metal element, and the content of the alkai metal element included in the glass plate is larger than that of an alkali metal element included in the film. As described above, the alkali metal element contained in glass generally increases electrical conductivity, the electrical conductivity includes the ion conductivity, of the glass, so that the electrical conductivity of the glass plate is relatively larger than that of the film.

The glass plate and the film also may have compositions in which the glass plate contains at least one element selected from iron (Fe), bismuth (Bi), vanadium (V), tungsten (W), and molybdenum (Mo), and the content of the at least one element included in the glass plate is larger than that of the at least one element included in the film. The at least one element contained in glass generally increases electrical conductivity, the electrical conductivity includes the electron conductivity, of the glass, so that the electrical conductivity of the glass plate is relatively larger than that of the film.

In the first manufacturing method, each composition of the glass plate and the film is not limited to the above examples as long as the electrical conductivity of the glass plate is larger than that of the film.

In the second manufacturing method, the composition of the glass plate is not particularly limited as long as the glass plate contains an alkali metal element and the content thereof is larger than that of the alkali metal element contained in the film. Typical examples of the alkali metal element contained in the glass plate include at least one element selected from lithium (Li), sodium (Na), and potassium (K). For instance, the glass plate can be soda-lime glass that generally is used for buildings and vehicles.

Soda-lime glasses contain at least Na20 as a component thereof.

In the second manufacturing method, the composition of the film is not particularly limited as long as the content of the alkali metal element included therein is smaller than that of the alkali metal element included in the glass plate. From the viewpoints of reducing the electrical conductivity of the film as much as possible and increasing the strength of the electric field to be induced in the film, it is preferable that the film be substantially free from an alkali metal element.

In the manufacturing methods of the present invention, as described above, minute metal particles are contained in the film having relatively lower electrical conductivity, which allows the strength of the electric field that is induced in the film to increase to ionise the minute metal particles efficiently. Accordingly, the glass plate with relatively higher electrical conductivity can be substantially free from minute metal particles.

The shape, size, etc. of the glass plate are not particularly limited but may be the same as those of glass plates to be used for buildings or vehicles, for example.

The kind of the minute metal particles to be contained in the film is not particularly limited. The minute metal particles may be minute particles containing at least one selected from gold (Au), platinum (Pt), palladium (Pd), and silver (Ag), for example. The film may include at least two kinds of minute particles containing different metals from each other.

In the manufacturing methods of the present invention, even when the film contains minute particles of metal that is more difficult to ionise than silver, such as gold, platinum, or palladium, the minute metal particles can be ionised more efficiently. That is, the film may include minute metal particles containing at least one selected from gold, platinum, and palladium. The film may include minute particles containing gold that is a stable metal and is the most difficult to ionise among the metals described above. The film also may include minute particles containing metal that is easier to ionise. For example, it can include minute particles of copper (Cu).

A standard reduction potential EO (25 C) of metal can be used as an index indicating the degree to which the metal is ionised. It can be said that the higher the standard reduction potential E0, the more difficult the ionisation of the metal concerned. According to Electrochemistry Handbook, the 5th edition, (Maruzen), p91-95, edited by Electrochemical Society of Japan, the standard reduction potentials E of the respective metals described above are as follows: silver 0.799V, palladium 0.915V, platinum 1.188V, and gold 1.52V.

The size of the minute metal particles is not particularly limited as long as they have a particle size that allows the film to be coloured.

Generally, the average diameter of the minute metal particles is about 1 nm to 30 nm. For example, when the minute metal particles are minute gold particles, the translucent colour tone of the layered product formed of the film and the glass plate can be varied variously to red, pink, violet, blue, etc., although it depends on the refractive index of the matrix of the film as well as the translucent colour tone of the glass plate itself.

The content of the minute metal particles included in the film is not particularly limited as long as it allows the film to be coloured. It is generally about 1 wt% to 30 wt%, preferably about 3 wt% to 20 wt%. When the film contains plural kinds of minute metal particles that are different from each other, the above-mentioned content can be a total of the contents of the respective kinds of minute metal particles.

The thickness of the film is preferably sufficiently thinner than that of the glass plate in order to increase the strength of the electric field to be induced in the film. For example, it can be about 10 nm to 1 jim, preferably about 30 nm to 500 nm.

The ratio dl/d2 between the thickness dl of the film and the thickness d2of the glass plate can be, for example, about 1 x 106 to 1 x 102, preferably about 5 x 10 to 5 x 10.

The method of forming the film on the glass plate is not particularly limited. It, however, is preferable that the film be formed by a sol-gel method.

The film can be formed by the sol-gel method according to the methods that are disclosed in, for instance, JP1O(1998)-316885A and JPO9(1997)-235141A. For example, a film containing minute gold particles can be formed by applying a coating solution containing an organic silicon compound represented by silicon (Si) alkoxide and chiorauric acid that is salt of gold, onto a glass plate and then thermally treating the whole. In this case, the film has a structure in which minute gold particles are dispersed in the matrix of Si02.

The coating solution to be applied to the glass plate in the sol-gel method may contain an organic metal compound such as an organic titanium (Ti) compound, an organic cerium (Ce) compound, etc., for the purpose of adjusting the refractive index of the matrix of the film to be formed. Such an organic metal compound is contained, as an inorganic oxide such as Ti02, CeO2, etc., in the matrix of the film together with Si02, through the heat treatment.

In the sol-gel method, when the above-mentioned coating solution contains salt of silver such as silver nitrate, etc., a film can be formed in which minute silver particles are dispersed. Similarly, when the above-mentioned coating solution contains salt of palladium such as palladium chloride, etc., a film can be formed in which minute palladium particles are dispersed. Furthermore, when the above-mentioned coating solution contains salt of platinum such as chloroplatinic acid, etc., a film can be formed in which minute platinum particles are dispersed.

The film also can be said to be a coloured film of a glass article that is a layered product formed of a film and a glass plate. The manufacturing methods of the present invention also can be said to be methods of manufacturing a glass plate coated with a film including regions that are different from each other in level of colouring.

The numbers of the layers of film and glass plate that are included in the glass article each are not particularly limited. The glass article may include two films and/or layered products or more. In the manufacturing methods of the present invention, the level to which the voltage application region of the film is coloured can be lowered. Accordingly, the film does not necessarily need to be exposed. For instance, the film may be sandwiched between and held by a pair of glass plates.

In the manufacturing methods of the present invention, it is preferable that the dielectric constant of the film be smaller than that of the glass plate. In this case, the strength of the electric field to be induced in the film can be increased further. The relative relationship between the dielectric constants of the film and the glass plate can be adjusted through the control of the compositions of the film and/or the glass plate.

The method of applying a voltage to a layered product formed of a film and a glass plate is not particularly limited. For example, a method of poling glass can be employed. For instance, as shown in FIG. 1, a layered product 3 formed of a film 1 containing minute metal particles 4 and a glass plate 2 may be sandwiched between and held by an anode 5 and a cathode 6 that are connected to a voltage applying device 8 such as a DC power source, and then voltage may be applied between the anode 5 and the cathode 6 with the voltage applying device 8.

The magnitude of a voltage to be applied to the layered product 3 can be set arbitrarily according to the degree to which the level of colouring of the region (a voltage application region 9) of the film 1, to which the voltage is applied, is intended to be lowered, i.e. according to the degree to which the minute metal particles 4 are intended to be ionised in the voltage application region 9. When the voltage to be applied between the anode 5 and the cathode 6 is increased, the strength of the electric field to be induced in the film 1 can be increased. This can promote the ionisation of the minute metal particles 4, i.e. the decrease in level of colouring of the voltage application region 9.

In the manufacturing methods of the present invention, when the magnitude of the voltage to be applied to the layered product 3 and/or the period of time for which the voltage is applied are determined suitably, a film 1 can be formed that includes coloured regions 10 and a non-coloured (decolourised) region 11 that corresponds to the voltage application region 9 as shown in FIG. 2. Thus, a glass article 12 can be manufactured in which the glass plate is coated with such a film 1.

The region (a second region) to which a voltage has been applied can be the non-coloured region 11 where all the minute metal particles contained in the region concerned were ionised to disappear. The second region, however, can include part of the minute metal particles that remains therein. In this case, the level of colouring is lower in the second region than that in the region (a first region) where no voltage has been applied, but the second region does have a colour derived from the minute metal particles as in the first region.

When the voltage is applied, it is preferable that the anode 5 and the cathode 6 be in contact with the layered product 3 as shown in FIG. 1. The direction of the voltage to be applied to the layered product 3 is not particularly limited, but the film 1 may be disposed on the anode 5 side, for

example.

The configurations of the anode 5 and the cathode 6 are not particularly limited as long as they allow the voltage to be applied to the layered product 3. For instance, the shape of at least one of the anode 5 and the cathode 6 may be identical to that of the voltage application region 9 when viewed from the direction perpendicular to the surface of the layered product 3.

The temperature of the layered product 3 may be raised in applying the voltage to the layered product 3. For instance, the temperature of the layered product 3 may be raised to around a temperature (generally, about 100 C to 400 C) that is employed when glass is poled thermally. The increase in temperature of the layered product 3 further promotes the ionisation of the minute metal particles 4 to be achieved through the application of the voltage.

EXAMPLE

The manufacturing methods of the present invention is described further in detail using an example. The present invention, however, is not limited to the example described below.

Example

First, 6 g of 0.1 N hydrochloric acid used as a hydrolysis catalyst and 44 g of ethylcellosolve used as a solvent were added to 50 g of ethyl silicate ("Ethyl silicate 40" manufactured by COLCOAT Co., Ltd.) used as an organic silicon compound. This was stirred at room temperature for two hours. Thus a solution A was obtained. The solution A contained 20 wt% of Si in terms of Si02.

Separately from the preparation of the solution A, 2 moles of acetylacetone were allowed to drop into 1 mole of titanium isoprop oxide while stirring was carried out. Thus a solution Bwas obtained. The solution B contained 16.5 wt% of Ti in terms of Ti02.

Independently of the preparation of the solutions A and B, cerium nitrate hexahydrate was added to ethylcellosolve so that the content of the cerium nitrate hexahydrate was 23.2 wt% in terms of Ce02. Thus, a solution Cwas obtained.

Furthermore, independently of the preparation of the solutions A to C chloroauric acid tetrahydrate was dissolved in ethylcellosolve so that the concentration thereof was 10 wt%. Thus, a solution Dwas obtained.

Subsequently, 2.25 g of the solution A, 0.12 g of the solution B, and 0.18 g of the solution Cwere mixed together and thereby a mixed solution was obtained. Then 5.5 g of ethylcellosolve further were added to the mixed solution. Thereafter, 2 g of the solution Dwere added thereto, which then was stirred well. Thus, a coating solution was obtained.

Next, the coating solution prepared as described above was applied, by spin coating, onto soda-lime glass with a thickness of 3.4 mm and a size of 10 cm x 10 cm that was used as a glass plate. After the application of the coating solution, it was heat-treated at 250 C for two hours and further was baked at 720 C for 120 seconds. Thus a glass plate (Sample 1) coated with a film containing minute colloidal gold particles was produced.

The composition of the film included, according to the mixture ratio of the respective solutions described above: Si02 75.7 wt%, Ti02 3. 3 wt%, CeO2 5 wt%, and 16 wt% minute colloidal gold particles (the total of 100 wt%, in which the amount of the minute gold particles is included). The composition of the film is free from an alkali metal element. The film had a thickness of 108 nm. The transparent colour tone of the film, i.e. the whole of Sample 1 was pink.

It should be noted that the electrical conductivity of the glass plate was larger than that of the film, judging from each composition.

Next, as shown in FIG. 1, an anode (with a size of 9.1 mm x 6.9 mm and a thickness of 1.3 mm) made of stainless steel was pressed against the surface of the film of Sample 1 produced as above while a cathode (with a size of 9.1 mm x 6.5mm and a thickness of 2.5 mm) made of stainless steel was pressed against the surface of the glass plate. Thus, Sample 1 was sandwiched between and held by the anode and the cathode. The anode and the cathode were placed so that the centers of the respective electrodes aligned with each other when viewed from the direction perpendicular to the surface of Sample 1.

Next, the anode and the cathode were connected electrically to a high-voltage DC source that was a voltage applying device. Thereafter, Sample 1 was placed in an electric furnace and then the temperature thereof was raised to 280 C. Subsequently, a voltage of a maximum of 1 kV was applied between the electrodes, with the temperature being maintained at 280 C. The voltage was increased up to 1 kV, 200V at a time in five steps and was maintained in each step for ten minutes. After a voltage of 1 kV was applied for ten minutes in the fifth step, the application of voltage was stopped and then the temperature of Sample 1 was brought back to room temperature by leaving Sample 1 to stand. Thereafter, the anode and the cathode were removed from Sample 1. In the region where the anode and the cathode had been placed and aligned with each other when viewed from the direction perpendicular to the surface of Sample 1, i.e. the voltage application region, the film was decolourised. The transparent colour tone of a part that corresponded to the region and included the glass plate was transparent and colourless. On the other hand, the original transparent colour tone was maintained in the region to which no voltage had been applied. Thus a glass article was formed that included coloured regions and a decolourised region like the one shown in FIG. 2.

The absorption spectrum of the voltage application region of Sample 1 with respect to light with a wavelength of 350 nm to 950 nm was evaluated before and after the application of the voltage. As a result, as shown in FIG. 3, it was found that the application of the voltage resulted in the disappearance of the absorption whose peak was at a wavelength of around 520 nm. Presumably, since the peak corresponded to the absorption band of the minute colloidal gold particles, the minute gold particles contained in the film were ionised through the application of the voltage.

In FIG. 3, the horizontal axis and the vertical axis indicate the wavelength (nm) and the absorbance (a.u.), respectively.

Furthermore, a test in which a voltage of a maximum of 400 V was applied to Sample 1 produced in the same manner as described above was carried out separately from the above. As a result, the voltage application region of the film was not decolourised but had a considerably lowered level of colouring as compared to the region to which no voltage had been applied.

Comparative Example

In a comparative example, a voltage was applied to a glass plate throughout which minute gold particles had been dispersed, as in the example, and then the change in level of colouring thereof was evaluated.

First, a gold film (with a thickness of 140 nm) was formed on the surface of silica glass (with a thickness of 1 mm; Type I, manufactured by Ital Quartz) by sputtering. Subsequently, the temperature of the whole was raised to 850 C to 1200 C and thereby the gold was dispersed in the silica glass. Thus a silica glass (Sample A produced as a comparative example) was produced, throughout which the minute gold particles had been dispersed. The transparent colour tone of the silica glass thus produced was pink.

Next, with respect to the silica glass thus produced, an anode and a cathode were placed as in Example. Subsequently, after the anode and the cathode were connected electrically to a high-voltage power source, Sample A was placed in an electric furnace and then the temperature thereof was raised to 280 C. A voltage of 3.1 kV was applied between the electrodes for minutes, with the temperature being maintained at 280 C. Thereafter, the application of voltage was stopped and then the temperature of Sample A was brought back to room temperature by leaving Sample A to stand.

Subsequently, the anode and the cathode were removed. As a result, decolourisation was not observed in the voltage application region. The transparent colour tone of the region was substantially the same as that of the region to which no voltage had been applied.

According to the present invention, it is possible to provide methods for manufacturing a glass article including regions that are differentfrom each other in level of colouring, which is manufacturing methods that allows the level of colouring that is achieved with minute metal particles to be lowered by using less energy.

A glass article obtained by the manufacturing methods of the present invention can be used for windows for vehicles such as automobiles, windows for buildings, or mirrors, for example.

Claims

CLAIMS 1.

A method for manufacturing a glass article that includes a first region and a second region, the first region being coloured with minute metal particles and the second region being less coloured than the first region, the method comprising: applying a voltage to a predetermined region of the glass article to be the second region so as to ionise at least a part of the minute metal particles included in the predetermined region, characterised in that the glass article to which the voltage is applied comprises a glass plate and a film formed on the glass plate, the electrical conductivity of the glass plate is larger than that of the film, the film includes the minute metal particles, and the voltage is applied to the glass article while the glass plate and the film are arranged between an anode and a cathode for applying the voltage, and at least a part of the minute metal particles included in the film is ionised in the predetermined region.
2.

A method as claimed in claim 1, wherein the glass plate contains an alkali metal element, and the content of the alkali metal element included in the glass plate is larger than that of an alkali metal element included in the film.

3. A method for manufacturing a glass article that includes a first region and a second region, the first region being coloured with minute metal particles and the second region being less coloured than the first region, the method comprising: applying a voltage to a predetermined region of the glass article to be the second region so as to ionise at least a part of the minute metal particles included in the predetermined region, characterised in that the glass article to which the voltage is applied comprises a glass plate and a film formed on the glass plate, the glass plate contains an alkali metal element, the content of the alkali metal element included in the glass plate is larger than that of an alkali metal element included in the film, and the film includes the minute metal particles, and the voltage is applied to the glass article while the glass plate and the film are arranged between an anode and a cathode for applying the voltage, and at least a part of the minute metal particles included in the film is ionised in the predetermined region.

4. A method as claimed in any one of claims 1 to 3, wherein the voltage is applied to the glass article whose temperature has been raised.

5. A method as claimed in any one of claims 1 or 4, wherein the minute metal particles contain gold.

6. A method as claimed in any one of claims 1 to 5, wherein the film is substantially free from an alkali metal element.

7. A method as claimed in any one of claims 1 to 6, wherein the glass plate is substantially free from a minute metal particle.

8. A method as claimed in any one of claims 1 to 7, wherein the film is formed by a sol-gel method.