WO2015036426A1

WO2015036426A1 - Laser process for the implementation of metallic nanoparticles into the surface of large size glass substrates

Info

Publication number: WO2015036426A1
Application number: PCT/EP2014/069273
Authority: WO
Inventors: Li-Ya Yeh; Michael BEHMKE; Lorenzo CANOVA; Nicolas Nadaud
Original assignee: Saint-Gobain Glass France
Priority date: 2013-09-10
Filing date: 2014-09-10
Publication date: 2015-03-19
Also published as: EP3044178A1

Abstract

A method for modification of optical properties of a glass substrate (1) by generation of nanoparticles comprising a) deposition of at least one metal compound containing layer (2) onto the glass substrate (1), b)focusing a laser line (4) onto the metal compound containing layer (2), c) laser processing of the glass substrate (1) with metal compound containing layer (2) by movement of the glass substrate (1) in direction x relative to the laser line(4), wherein the glass substrate (1) has got a width of 0.10 m to 5.00 m perpendicular to the direction x and wherein laser induced diffusion of metal ions from the metal compound containing layer (2) into the glass substrate (1) and/or other neighboring layers takes place and nanoparticles are generated within the glass substrate (1) and/or other neighboring layers during step c).

Description

Laser process for the implementation of metallic nanoparticles into the surface of large size glass substrates

The invention relates to a laser process for the implementation of metallic nanoparticles into the surface of large size glass substrates and its use.

Modern architecture often contains large glass surfaces, which are often colored to give an appealing impression. Manufacturing of colored glass is usually done by addition of colorants, e.g. metals or metal oxides, to the molten glass or the raw materials for glass production. Changing the color or the composition of the glass is extremely time consuming and expensive as the float glass process is a continuous process and large scales of rejects are produced.

Alternatively several post processes for coloration of glass are known. In these post processes metallic particles are applied into or onto the glass surface, whereby not only the color but also the optical properties of the glass can be modified. The modification of optical properties gives rise to a huge spectrum of possible applications for such glazing, e.g. selective solar absorbers, photo thermal conversion of solar energy or energy efficient windows.

Multiple thermal processes for generation of metallic nano particle in the surface near region of glass are disclosed. WO 2010/106370 describes a process for coloration of glass, in which a precursor containing metallic nanoparticles is sprayed onto a hot glass substrate. The glass substrates are heated to a temperature of 350°C to 550 °C. The tempering has to done for several minutes due to the time dependency of the diffusion process. Hence the process is rather time consuming. Another method for coating glass substrates is flame spraying. Such a flame spraying process is for example disclosed in WO 2008/099048. In a first step a precursor comprising coloring transition metal oxides is flame sprayed onto the substrate followed by a reduction step. Reduction of metal cations yields the corresponding metal, which arranges to nanometric collodials in the glass matrix. This process is less time consuming compared to the process disclosed in WO 2010/106370, nevertheless a substrate temperature between 500°C and 800°C is obtained.

Another process leading to colored glass or glass with optically modified properties is alternating sputtering and co-sputtering of a dielectric matrix containing nano particles onto the glass surface. The mechanical stability and resistivity of the obtained coating is quite low due to the low layer thickness between 10 nm and 500 nm.

US 2004/01 18157 A1 discloses a process for laser beam-assisted implementation of metallic nano particles into glass surfaces. The object of the invention is to develop a method for marking glass or to produce multi colored decorations. The laser processing is preferably realized by a C0₂ laser, whereat the deposition area is limited by the size of the laser spot. The size of the processing area of such laser arrangements is typically limited between 10 μηη and several millimeters. Hence the laser process described in US 2004/01 18157 A1 is not suitable for processing of large sheets of glass.

The object of the present invention is to provide a profitable laser process for implementation of metallic nanoparticles into the surface of glass or coated glass substrates, wherein also large size substrates can be processed.

The solution of the object of the present invention is a laser process for implementation of metallic nanoparticles into the surface of large size glass substrates and its use according to independent claims 1 and 13.

The method according to the invention for modification of optical properties of a glass substrate by processing of nanoparticles comprises the following steps:

a) at least one metal compound containing layer is deposited onto the glass substrate,

b) a laser line is focused onto this metal compound containing layer,

c) the glass substrate is moved in a direction x relative to the laser line and the glass substrate with metal compound containing layer is laser processed, wherein the glass substrate has got a width of 0.10 m to 5.00 m perpendicular to the direction x. During step c) laser induced diffusion of metal ions from the metal compound containing layer into the glass substrate and/or other neighboring layers takes place. These metal ions form nanoparticles within the glass substrate (1 ) and/or other neighboring layers, which leads to a change in optical properties of the substrate.

The method according to the invention enables a homogeneous and time-saving laser processing of large size substrates. The metal compound containing layer is heated by carefully targeted laser processing, whereas an increase of the core temperature of the glass substrate can be mostly avoided and only the temperature within the surface near region of the glass substrate is slightly raised. The method according to the invention involves the generation of nanoparticles and if desirable also a subsequent diffusion and/or modification of these nanoparticles. The laser heating leads to a formation of metal ions within the processed metal compound containing layer in a first step. These metals ions diffuse into the glass substrate and/or other neighboring layers where they are reduced to elementary metal and form nanoparticles by self-organization. Hence the product gained in the process contains nanoparticles. A local heat treatment of the metal compound containing layer yields nanoparticles and/or leads to the modification of their optical properties. Hence the process according to the invention is especially advantageous for the production of large-scale sheets of colored glass or diffractive glazing.

The change of optical properties or color is governed by the size, number, depth and allocation of the nanoparticles. These values can be controlled by the heating process. Therefore the precise adjustment of the laser heating process allows a defined modification of the optical properties.

The change in optical properties or color of the modified glass is defined by the wavelength of the Surface Plasmon Resonance (SPR). This is manly governed on the material of the nanoparticles. For example cobalt leads to bluish, copper to ruby, nickel to grey and silver to yellow color change.

Oven processes according to the state of the art are rather time consuming, in general a few minutes are needed per substrate, whereas laser processes according to the state of the art use lasers providing a laser spot of very limited size, typically 10 pm to a few millimeters. Thus these processes are not suitable for processing of large size substrates. The method according to the invention enables a fast processing of large substrates, in which a single substrate is typically processed within a few seconds, preferably a fraction of seconds.

The direction x is defined as the direction of relative movement between the laser line and the substrate during processing. In a preferred embodiment of the invention the glass substrates are placed onto a conveyor, which is spanned by a stationary laser arrangement generating the laser line. The glass substrates are transported in direction x via the conveyor and processed by crossing the laser line. This embodiment is especially advantageous as the process could be performed in line with a float process and a deposition process. In an alternative embodiment the laser arrangement is mounted on a moveable track system while the glass substrates are held stationary. The direction x is solely defined as positive value as the transportation of the glass sheet only takes place in one direction. A backward transport of the glass substrate in direction -x is not necessary as the laser line covers the width of the substrate and the entire surface of the substrate is treated within one cycle. A time- consuming repeated passage of substrates is not required.

In a first particularly advantageous embodiment of the invention the metal compound containing layer is a transfer medium from which metal compounds diffuse into the glass substrate and form nanoparticles in the surface near region of the glass substrate during laser processing (step c)) and the transfer medium is removed afterwards. The diffusing species could be for example metals or also metal ions depending on the transfer medium applied.

The transfer medium is applied in form of a paste, coating, fluid or diffusion ink onto the glass substrate, preferably as a paste. For the application of the transfer medium a wide variety of processes, which are known to the person skilled in the art can be utilized. Preferably pastes are printed via ink jet printing, coatings are sputtered and fluids are spray coated.

The transfer medium contains a transition metal or transition metal compound, preferably silver, gold, iron, copper, chromium, cobalt, nickel, molybdenum, palladium, platinum, manganese, vanadium, rare earth metals or compounds or mixtures thereof, more preferably cobalt, nickel, palladium, silver, gold, copper or compounds or mixtures thereof, most preferably silver, gold or cobalt.

In a second particularly advantageous embodiment of the invention the metal compound containing layer is a donator layer from which metal compounds diffuse into the neighboring glass substrate and/or a neighboring acceptor layer and form nanoparticles in the surface near region of the glass substrate and/or in the acceptor layer during step c). The diffusing species could be for example metals or also metal ions depending on the transfer medium applied.

The second embodiment comprises a stack of at least one donator layer and at least two acceptor layers, which are applied onto the glass substrate. Preferably the outer layers of the stack are acceptor layers, between which one or multiple donator layers or a series of alternating donator and acceptor layers are embedded. The acceptor layers and donator layers could be deposited by various alternative sputtering processes, e.g. by co-sputtering. The donator layer according to the second embodiment of the invention contains a transition metal or transition metal compound, preferably silver, gold, iron, copper, chromium, cobalt, nickel, molybdenum, palladium, platinum, manganese, vanadium, rare earth metals or compounds or mixtures thereof, more preferably cobalt, nickel, palladium, silver, gold, copper or compounds or mixtures thereof, most preferably gold, copper, silver.

The acceptor layer according to the second embodiment of the invention contains a dielectric material and/or a transparent conductive oxide, preferably Si₃N₄, Si0₂, Ti0₂, ITO, Al₂0₃ or compounds or mixtures thereof, more preferably Si₃N₄.

The general process parameters used for laser modification, generation and/or diffusion of nanoparticles within all embodiments mentioned are described in the following paragraphs:

The length of the laser line is defined as its maximum dimension, while the width of the laser line is its minimum dimension. Preferably the laser line runs along direction y, perpendicular to direction x, so that the width of the laser line is measured along direction x, while the length of the laser line is measured along direction y. Alternatively a diagonal progression of the laser line is also possible.

The laser line according to the invention is preferably generated by a series of laser assemblies, mounted besides each other. The areas illuminated by the single laser assemblies add up to the laser line. The single laser assemblies can be operated independently, e.g. the power density could be modulated within the laser line.

In an alternative embodiment of the invention the laser line is generated by a single laser.

Preferably the laser assemblies comprise diode lasers, fiber lasers and/or disk lasers, most preferably diode lasers.

In a preferred embodiment of the method according to the invention the laser line has got a length of 0.10 m to 5.00m, preferably 0.25 m to 3.50 m, more preferably of 0.60 m to 3.30 m. As the general standard size of float glass sheets is 6 m x 3 m, the method according to the invention enables homogeneous and fast processing of such sheets.

The laser line has got a width of 10 μηη to 500 μηη, preferably 20 μηη to 250 μηη, most preferably 20 μηη to 100 μηη. Within those line widths the power density of the laser line is between 50 W/mm² and 3000 W/mm², preferably 300 W/mm² to 2000 W/mm², most preferably 500 W/mm² to 1700 W/mm².

One example for the line width of the laser line is 40 μηι. The line width should be chosen as small as possible to maximize the energy input per unit area. A large energy input per surface area means that the processing time can be kept short. Hence only the surface area of the substrate is heated and the temperature rise of the glass is minimized.

The wave length of the laser line is between 250 nm to 2000 nm, preferably 500 nm to 1700 nm, most preferably 700 nm to 1300 nm.

The method according to the invention is suitable for heat treatment within the temperature range of 80 °C to 700 °C, preferably 100 °C to 600 °C. In a preferred embodiment the maximum core temperature of the glass substrate is 250 °C, preferably 100 °C, most preferably 80 °C. Thus also temperature sensitive substrates can be processed. The core temperature of the glass substrate is defined as the temperature outside the surface near region, wherein during processing the temperature of the surface near region is equal to or higher than the core temperature.

The surface near region has got a thickness of 1 μηι to 500 μηι, preferably 1 μηι to 100 μηι.

In one possible embodiment of the invention the laser line is turned off at least once during step c) and/or the power density of the laser line is modified during step c). Such a modulation of the power density leads to a structuring of the substrate as nanoparticles are only formed in some regions, e.g. when the laser line is turned off during processing, or nanoparticles with different properties are formed. This could be desirable in terms of design aspects, for the production of diffractive glazing or other linear designs for gaining optical effects.

In another embodiment according to the invention the power density along the laser line is not homogeneous and/or the power density along the laser line is modified during step c). Such an embodiment of the process is for example advantageous in production of glazing with an inhomogeneous appearance or color. Another solution of the present invention is the use of the method according to the invention for the production of colored glass substrates or diffractive glazing, preferably for processing of large-scale glass substrates with a size of at least 1 m².

Further advantages and details of the present invention can be taken from the description of several exemplary embodiments with reference to the drawings.

Figure 1 a depicts a cross sectional view of a glass substrate with a transfer medium and a method according to the first embodiment according of the invention.

Figure 1 b depicts a top view of the glass substrate according to figure 1 a.

Figure 2 shows a cross sectional view of a glass substrate with a transfer medium and another method according to the first embodiment of the invention, wherein a diffractive glazing is produced.

Figure 3 shows a cross sectional view of a glass substrate with a transfer medium and a further method according to the first embodiment of the invention, wherein a diffractive glazing is produced.

Figures 4a and 4b show cross sectional views of a glass substrate with donator layers and acceptor layers and a method according to the second embodiment of the invention.

Figures 5 and 6 depict preferred embodiments of the first and the second embodiment of the method according to the invention.

Figure 1 a depicts a glass substrate (1 ) coated with a metal compound containing layer (2) and a method for its laser treatment according to the first embodiment of the invention, wherein the metal compound containing layer (2) is a transfer medium (2.1 ). The transfer medium (2.1 ) is a silver conductive paste for printing applications containing 30-35 % Ag with a particle size of < 50 nm in a matrix of triethylene glycol monoethyl ether. In a first step the paste is printed onto the glass substrate (1 ) according to step a) of the method according to the invention. A laser line (4) is focused onto the transfer medium (2.1 ) in step b) and the glass substrate (1 ) is processed by moving the glass substrate in direction x relative to the laser line (4) in step c). The laser line (4) runs along direction y, perpendicular to the direction x, to cover the whole width of the substrate by a laser line (4) being as short as possible. The laser line (4) has got a length of 3.1 m and runs along the width of the glass substrate (1 ), having a width of 3.0 m, along direction y, perpendicular to direction x. The laser line (4) has got a line width of 40 μηη, a power density of 1000 W/mm² and a wave length of 980 nm. Laser treatment of the transfer medium (2.1 ) leads to a temperature increase, which initiates the diffusion of silver ions from the transfer medium (2.1 ) into the surface near region (R) of the glass substrate (1 ). As the surface near region (R) is also heated during laser processing of the transfer medium (2.1 ) a temperature-controlled arrangement of elemental silver to silver nanoparticles takes place within the surface near region (R). Hence nanoparticles within glass (3) are formed. The last step (step d)) of the process comprises the removal of the transfer medium (2.1 ), e.g. by a solvent.

Figure 1 b shows a top view of the glass substrate (1 ) with transfer layer (2.1 ) according to Figure 1 a. The laser line (4) runs along the direction x and covers the whole width of the glass substrate (1 ). The glass substrate (1 ) is laser processed by transport of the substrate in direction x via a conveyor.

Figure 2 shows a cross sectional view of a glass substrate (1 ) with a transfer medium (2.1 ) according to the first embodiment of the invention. The transfer medium (2.1 ) and the properties of the laser line (4) are those already described in Figure 1 . The transfer medium (2.1 ) is printed onto the glass surface in step a), which corresponds to figure 1 step a). The laser line (4) is focused onto the transfer medium (2.1 ) in step b) and the glass substrate (1 ) is processed by moving the glass substrate in direction x relative to the laser line (4) in step c). The laser line (4) is turned off and on frequently during step c). Hence a linear pattern of parallel lines, in which nanoparticles in glass (3) within the surface near region (R) are generated, is obtained. The last step (step d)) of the process comprises the removal of the transfer medium (2.1 ), e.g. by a solvent. The process according to figure 2 is particularly advantageous as patterns of high resolution can be generated.

Figure 3 shows a cross sectional view of a glass substrate with a transfer medium (2.1 ) and a further method according to the first embodiment of the invention. The transfer medium (2.1 ) and the properties of the laser line (4) are those already described in Figure 1 . The transfer medium (2.1 ) is printed in form of a linear pattern of parallel lines onto the glass surface in step a). The laser line (4) is focused onto the transfer medium (2.1 ) in step b) and the glass substrate (1 ) is processed by moving the glass substrate in direction x relative to the laser line (4) in step c). The laser line (4) is turned off and on frequently during step c), wherein only the surface areas carrying the transfer medium (2.1 ) are laser heated. The required amount of transfer medium (2.1 ) is reduced advantageously as it is only applied in the obligatory surface portion, which leads to a cost reduction. Furthermore a heating of the uncoated glass substrate is avoided by turning the laser line (4) off within surface portions not carrying a transfer medium (2.1 ). A linear pattern of parallel lines, in which nanoparticles in glass (3) within the surface near region (R) are generated, is obtained. The last step (step d)) of the process comprises the removal of the transfer medium (2.1 ), e.g. by a solvent.

Figure 4a shows a cross sectional view of a glass substrate (1 ) with a donator layer (2.3) and an acceptor layer (5) and a method according to the second embodiment of the invention. The donator layer (2.3) consists of a 2 nm silver layer applied in an alternate sputtering process with an acceptor layer (5) of 10 nm Si₃N₄ during step a). A laser line (4) is focused onto the donator layer (2.3) in step b) and the glass substrate (1 ) is processed by moving the glass substrate in direction x relative to the laser line (4) in step c). The laser line (4) runs along direction y, perpendicular to the direction x, to cover the whole width of the substrate by a laser line (4) being as short as possible. The laser line (4) has got a length of 3.1 m and runs along the width of the glass substrate (1 ), having a width of 3.0 m, along direction y, perpendicular to direction x. The laser line (4) has got a line width of 40 μηη, a power density of 1000 W/mm² and a wave length of 980 nm. Laser treatment of the donator layer (2.3) leads to a temperature increase, which initiates the diffusion of silver from the donator layer (2.3) into the acceptor layer (5) yielding an acceptor layer with nanoparticles (5.1 ). The optical properties of the coated substrate are changed by laser processing and the thereby induced diffusion of nanoparticles.

Figure 4b depicts a cross sectional view of a glass substrate (1 ) with another donator layer (2.3) and another acceptor layer (5) and a method according to the second embodiment of the invention. The donator layer (2.3) consists of a 3 nm gold layer applied in an alternate sputtering process with an acceptor layer (5) of 30 nm Ti0₂. The upper layer of the stack and the layer directly applied onto the glass substrate (1 ) are acceptor layers. Between this top and bottom acceptor layers (5) an alternating stack of three donator layers (2.3) and two acceptor layers (5) is applied. The properties of the laser line (4) and the dimensions of the substrate are those already described in Figure 4a. Laser treatment of the donator layer (2.3) leads to a temperature increase, which initiates the diffusion of gold from the donator layer (2.3) into the acceptor layer (5) yielding an acceptor layer with nanoparticles (5.1 ). The optical properties of the coated substrate are changed by laser processing and the thereby induced diffusion of nanoparticles. Figure 5 shows a flow chart of the first embodiment of the method according to the invention.

Figure 6 shows a flow chart of the second embodiment of the method according to the invention.

References

1 glass substrate

2 metal compound containing layer

2.1 transfer medium

2.3 donator layer

3 nanoparticles in glass

4 laser line

5 acceptor layer

5.1 acceptor layer with nanoparticles

X direction of relative movement of laser line and glass substrate y direction perpendicular to direction x

R surface near region

Claims

1 . A method for modification of optical properties of a glass substrate (1 ) by generation of nanoparticles comprising

a) deposition of at least one metal compound containing layer (2) onto the glass substrate (1 ),

b) focusing a laser line (4) onto the metal compound containing layer (2), c) laser processing of the glass substrate (1 ) with metal compound containing layer (2) by movement of the glass substrate (1 ) in direction x relative to the laser line (4),

wherein the glass substrate (1 ) has got a width of 0.10 m to 5.00 m perpendicular to the direction x and

wherein laser induced diffusion of metal ions from the metal compound containing layer (2) into the glass substrate (1 ) and/or other neighboring layers takes place and nanoparticles are generated within the glass substrate (1 ) and/or other neighboring layers during step c).

2. Method according to claim 1 , wherein the metal compound containing layer (2) is a transfer medium (2.1 ) from which metal ions diffuse into the glass substrate (1 ) and form nanoparticles in the surface near region (R) of the glass substrate (1 ) during step c) and the transfer medium (2.1 ) is removed after step c).

3. Method according to claim 2, wherein the transfer medium (2.1 ) contains a transition metal, preferably silver, gold, iron, copper, chromium, cobalt, nickel, molybdenum, palladium, platinum, manganese, vanadium, rare earth metals or compounds or mixtures thereof, more preferably cobalt, nickel, palladium, silver, gold, copper or compounds or mixtures thereof, most preferably silver, gold or cobalt.

4. Method according to claim 1 , wherein the metal compound containing layer (2) is a donator layer (2.3) from which metal ions diffuse into the neighboring glass substrate (1 ) and/or a neighboring acceptor layer (5) and form nanoparticles in the surface near region (R) of the glass substrate (1 ) and/or in the acceptor layer (5) during step c).

5. Method according to claim 4, wherein a stack of at least one donator layer (2.3) and at least two acceptor layers (5) are applied onto the glass substrate (1 ) in step a).

6. Method according to claim 4 or 5, wherein the donator layer (2.3) contains a transition metal, preferably silver, gold, iron, copper, chromium, cobalt, nickel, molybdenum, palladium, platinum, manganese, vanadium, rare earth metals or compounds or mixtures thereof, more preferably cobalt, nickel, palladium, silver, gold, copper or compounds or mixtures thereof, most preferably gold, copper, silver.

7. Method according to one of the claims 4 to 6, wherein the acceptor layer (5) contains a dielectric material and/or a transparent conductive oxide, preferably Si₃N₄, Si0₂, Ti0₂, ITO, Al₂0₃ or compounds or mixtures thereof.

8. Method according to one of the claims 1 to 7, wherein the laser line (4) has got a length of 0.10 m to 5.00 m, preferably 0.25 m to 3.50 m, most preferably of 0.60 m to 3.30 m.

9. Method according to one of the claims 1 to 8, wherein the wave length of the laser line (4) is between 250 nm to 2000 nm, preferably 500 nm to 1700 nm, most preferably 700 nm to 1300 nm.

10. Method according to one of the claims 1 to 9, wherein the maximum core temperature of the glass substrate (1 ) is 250 °C, preferably 100 °C, most preferably 80 °C.

1 1 . Method according to one of the claims 1 to 10, wherein the laser line (4) is turned off at least once during step c) and/or the power density of the laser line (4) is modified during step c).

12. Method according to one of the claims 1 to 1 1 , wherein the power density along the laser line (4) is not homogeneous and/or the power density along the laser line (4) is modified during step c).

13. Use of the method according to one of the claims 1 to 12 for the production of colored glass substrates or diffractive glazing, preferably for processing of large-scale glass substrates with a size of at least 1 m².