Device for drying and sintering metal-containing ink on a substrate

Abstract

A device for drying and sintering metal-containing ink on a substrate enables homogeneous irradiation of the substrate, has compact construction, and is simple and economical to produce. Optical infrared radiators have a cylindrical radiator tube and a longitudinal axis, and emit radiation having an IR-B radiation component of at least 30% and an IR-C radiation component of at least 5% of total radiator output power. The radiators are arranged in a module with their longitudinal axes running parallel to each other and transverse to the transport direction. They thereby irradiate on the surface of the substrate an irradiation field, which is divided into a drying zone and a sintering zone arranged downstream of the drying zone in the transport direction. The drying zone is exposed to at least 15% less average irradiation density than the sintering zone along a center axis running in the transport direction.

Claims

1. A device for drying and sintering metal-containing ink on a substrate, the device comprising multiple optical radiators for irradiating the substrate and a reflector for reflecting radiation onto the substrate, the optical radiators and substrate being movable relative to each other in a transport direction, wherein the optical radiators are infrared radiators having a cylindrical radiator tube and a radiator tube longitudinal axis, the optical radiators emitting an IR-B radiation component of at least 30% and an IR-C radiation component of at least 5%, each based on total radiator output power, the optical radiators being arranged in a radiator module such that their radiator tube longitudinal axes run parallel to each other and transverse to a transport direction of the substrate, wherein the optical radiators irradiate an irradiation field on a surface of the substrate, such that the irradiation field is divided into a drying zone and a sintering zone downstream of the drying zone in the transport direction, and wherein the drying zone is exposed to at least 15% less average irradiation density than the sintering zone along a center axis running in the transport direction.

2. The device according to claim 1, wherein the multiple infrared radiators comprise an infrared radiator of a first type having an emission maximum in a wavelength range between 1600 nm and 3000 nm and an infrared radiator of a second type having an emission maximum in a wavelength range between 900 nm and 1600 nm.

3. The device according to claim 2, wherein multiple infrared radiators of the first type and multiple infrared radiators of the second type are provided, and wherein adjacent infrared radiators of the first type have a greater spacing relative to each other than adjacent infrared radiators of the second type.

4. The device according to claim 1, wherein the infrared radiators emit radiation continuously.

5. The device according to claim 1, wherein the infrared radiators have a broadband emission spectrum having visible range and IR-A range radiation components which together equal at least 10% of the total radiator output power.

6. The device according to claim 1, wherein the irradiation field has a total surface area in a range of 800 cm.sup.2 to 6000 cm.sup.2, and wherein surface areas of the drying zone and the sintering zone each make up at least 30% of the total surface area.

7. The device according to claim 6, wherein the surface area of the drying zone is in a range between 35% and 65% of the total surface area.

8. The device according to claim 6, wherein the drying zone and the sintering zone have a same amount of surface area.

9. The device according to claim 1, wherein the drying zone has an average irradiation density of less than 50 kW/m.sup.2 along the center axis.

10. The device according to claim 1, wherein the sintering zone has an irradiation density of greater than 50 kW/m.sup.2 along the center axis.

11. The device according to claim 1, wherein the radiator module is designed for an irradiation of the irradiation field having an average irradiation density in a range of 30 kW/m.sup.2 to 250 kW/m.sup.2.

12. The device according to claim 1, wherein the radiator module has a cooling element arranged on a side of the reflector facing away from the infrared radiators.

13. The device according to claim 12, wherein the cooling element is a water cooling system.

Description

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

(1) The foregoing summary, as well as the following detailed description of the invention, will be better understood when read in conjunction with the appended drawings. For the purpose of illustrating the invention, there are shown in the drawings embodiments which are presently preferred. It should be understood, however, that the invention is not limited to the precise arrangements and instrumentalities shown. In the drawings:

(2) FIG. 1 is a schematic cross-sectional representation of a first embodiment of the device according to the invention for drying and sintering a metal-containing ink;

(3) FIG. 2 is a schematic three-dimensional representation of a second embodiment of the device according to the invention; and

(4) FIG. 3 is a ray-tracing simulation of the irradiation intensity for the second embodiment of the device according to the invention as per FIG. 2.

DETAILED DESCRIPTION OF THE INVENTION

(5) FIG. 1 shows schematically a first embodiment of the device according to the invention, designated overall by the reference numeral 100. The device 100 is used for drying and sintering metal-containing ink on a substrate 103. It is suitable especially for drying and sintering inks in components for printed electronics, which are manufactured in a roll-to-roll process.

(6) The device 100 comprises a radiator module 101 having four infrared radiators 102a, 102b arranged therein for emitting optical radiation 105, a reflector 107, and also a mirror 104 for reflecting a portion of the radiation 105 emitted by the radiator module 101 onto the substrate 103.

(7) The infrared radiators 102a, 102b are twin tube radiators designed for continuous operation; they have a cylindrical radiator tube having a radiator tube longitudinal axis. The infrared radiators 102a are carbon radiators having a color temperature of 1200 C.; they are allocated to the drying zone and have an emission maximum at a wavelength of approximately 1.9 m. The infrared radiators 102b are short-wave infrared radiators having a color temperature of approximately 2200 C.; they contribute significantly to generating the sintering zone. The emission maximum of these radiators is at a wavelength of approximately 1.2 m. Both infrared radiator types 102a, 102b emit radiation having a radiation component of IR-B radiation of greater than 30% and in the IR-C range of greater than 5% of the total radiator output power. In addition, both infrared radiator types 102a, 102b emit greater than 10% of the total radiator output power in the IR-A range and in the visible range.

(8) The infrared radiators 102 are arranged parallel to each other within the radiator module 101 and perpendicular to the transport direction 108.

(9) Adjacent infrared radiators 102a have a spacing 111 from each other of 55 mm, adjacent infrared radiators 102b have a spacing 112 from each other of 38 mm. The spacing a between the bottom side of the infrared radiators 102a, 102b and the substrate is 60 mm. An adjustment unit (not shown) allows a simple adjustment of the spacing a in a range of 35 mm to 185 mm.

(10) The radiator module 101 has a two-sided, angled housing 106 having a side facing the infrared radiators. The reflector 107 is mounted on this side. Therefore, because the reflector 107 has a base reflector 107a and two side reflectors 107b, 107c, a large component of the infrared radiation emitted by the infrared radiators 102 is incident on the substrate 103. The reflector 107 is made of aluminum and suitable for the reflection of infrared radiation having a wavelength in the range of 800 nm to 5000 nm. In an alternative embodiment (not shown), highly reflective coating made of aluminum, silver, gold, copper, nickel, or chromium is mounted on the housing.

(11) The radiator module 101 irradiates an irradiation field on the surface of the substrate 103, which viewed in the transport direction 108 has a drying zone 109 and a sintering zone 110 downstream of the drying zone 109. The radiator module 101 is designed for an irradiation of the irradiation field having an average irradiation density of approximately 150 kW/m.sup.2. The irradiation field has a total surface area of 1800 cm.sup.2; the surface area of the drying and sintering zones is each approximately 750 cm.sup.2. The drying and sintering zones 109, 110 differ in their average irradiation density. Along a center axis running in the transport direction, the average irradiation density in the drying zone 109 is 50 kW/m.sup.2 and in the sintering zone 110 is 250 kW/m.sup.2.

(12) The substrate 103 is a plastic film made of PET having a film thickness of 0.1 mm, which is moved by a transport device (not shown) in the transport direction 108 relative to the radiator module 101. The substrate 103 is moved at a constant advancing speed.

(13) Within the housing 106 there is a cooling element (not shown) for cooling the reflector 107 and the infrared radiators 102. The cooling element is a water cooling system. It contributes to a long service life of the device, especially of the radiators and the reflector layer. In an alternative embodiment, the cooling element is an air cooling system. Here, the cooling element is designed so that the substrate 103, due to its low thermal mass, is not cooled by an air flow coming out from the radiator module 101. This is achieved, for example, by an air heat exchange system for the reflector 107 or an air cooling system for the infrared radiators 102 and the reflector 107 having special air conductance and side air outlet.

(14) FIG. 2 shows schematically in three-dimensional representation a radiator module 200 for use in a device according to the invention for drying and sintering metal-containing ink.

(15) The radiator module 200 comprises 12 infrared radiators (not shown), as well as a housing 201 made of several plates 202, 203, 204. The outer dimensions of the radiator module 200 are 650 mm450 mm160 mm (LBH). Furthermore, an inner reflector 205 is provided, which is mounted on the inner surface of the radiator module housing 201. The inner reflector 205 covers the inner surfaces of the plates 203, 204, 208. Reflector plates 207 are also mounted on the end sides. With the reflector 205, especially the side reflectors on the plates 203, 204, and the reflector plates 207, the greatest possible part of the radiation emitted by the infrared radiators is provided for the irradiation of the substrate. The inner reflector 205 is allocated to the heated areas of the infrared radiators. The unheated ends of the radiators extend out from the area of the reflector 205. The radiator module 200 is designed for the irradiation of an irradiation field having the dimensions 600 mm350 mm (lb). The bottom side of the infrared radiators has a spacing h of 50 mm from the substrate.

(16) The infrared radiators are selected and arranged within the radiator module 200 so that the irradiation profile generated by the radiator module 200 on the irradiation field comprises a drying zone and a sintering zone. The infrared radiators are mounted on the unheated ends on the plate 202, such that their position can be adjusted in the longitudinal direction 1 and thus can set various irradiation profiles of the irradiation field.

(17) Within the plates 202, 203, 204 of the housing 201 there is a respective cooling element in the form of a water cooling system 206 for cooling the inner reflector 205 and the infrared radiators.

(18) The plates 202, 203, 204 having cooling elements can be produced by various methods, for example by welding or soldering a meander-shaped U-profile on a flat base plate, by welding or soldering half-tubes on a base plate, or by milling channels in a base plate and then pressing copper tubes into the channels.

(19) FIG. 3 shows a ray-tracing simulation of the irradiation intensity of the second embodiment of the device according to the invention. In the diagram 300, the infrared irradiation density is shown in W/mm.sup.2 in an irradiation field having a size of 300 mm600 mm on the surface of a substrate made of PET film. The transport direction of the PET film relative to the radiator module of the device is indicated in FIG. 3 by the arrow 305.

(20) The ray-tracing simulation is based on the radiator module 200; it is distinguished by an irradiation width w of 350 mm, an irradiation length l of 600 mm, and a height h of 50.5 mm.

(21) The radiator module 200 is equipped with eight IR twin tube radiators, of which four have an output power of 22.725 kilowatt (sintering zone) and four have an output power of 21200 watt (drying zone), wherein only one channel is active for each. Adjacent twin tube radiators in the drying zone have a spacing of 70 mm and in the sintering zone of 45 mm.

(22) The spacing of the radiator bottom sides from the PET surface is 50 mm. On the side of the radiator module facing the PET film, a reflector is applied in the form of a gold coating.

(23) On the abscissa 301 of the diagram 300, the magnitude of the irradiation field in the x-direction is plotted in mm; the ordinate 302 shows the extent of the irradiation field in the y-direction. The diagram 300 shows the distribution of the irradiation intensity in the irradiation field in gray-scale representation.

(24) The irradiation field is divided by a center axis 304 running in the transport direction 305 and a vertical 303 running perpendicular to the center axis 304 into four equal-size sub-areas.

(25) The ray-tracing simulation shows an irradiation field that comprises two irradiation zones, namely a drying zone 307 and a sintering zone 309. The drying zone 307 has, along the center axis 304, an average irradiation density of approximately 50 kW/m.sup.2. The irradiation density along the center axis 304 is 135 kW/m.sup.2 in the sintering zone.

(26) The diagram 310 also shows the profile of the irradiation intensity in W/mm.sup.2 in the direction of the vertical 303. The diagram 311 shows the profile of the irradiation intensity along the center axis 304.

(27) Example

(28) A plastic film made of polyethylene naphthalate (PEN) having a film thickness of 100 m is printed with an inkjet printer (Dimatix DMP283; Dropspace 25/30 m) having metal-containing ink. As the ink, a dispersion of silver nanoparticles (20 wt. %) in organic solvents is used (Suntronic Jet Silver U5603).

(29) The printed plastic film is then dried with a device that comprises a radiator module having 22 short-wave infrared radiators having a cylindrical radiator tube. The heated length of the radiator tubes is 150 mm. A gold reflector is applied to the side of the radiator tubes facing away from the coating. The infrared radiators have a wide wavelength spectrum and a color temperature less than 2500 C. They are designed for an electrical output power of 40.7 kW. The power per surface area of the radiator is 50 kW/m.sup.2. The spacing of the radiators to the film is approx. 50 mm. On the bottom side of the film there is a ceramic filter board radiation converter. The spacing of the radiation converter to the bottom side of the film is approximately 120 mm.

(30) For the drying and sintering of the ink layer, the film is moved in the transport direction with an advancing speed of 4 cm/s relative to the radiator module. The processing time is 10 s (for comparison: processing time with hot air (140 C.): 40 s).

(31) The sintered coating has good electrical conductivity; its resistance is 3 Ohm.

(32) It will be appreciated by those skilled in the art that changes could be made to the embodiments described above without departing from the broad inventive concept thereof. It is understood, therefore, that this invention is not limited to the particular embodiments disclosed, but it is intended to cover modifications within the spirit and scope of the present invention as defined by the appended claims.