DE102009037371B3 - Coating device for substrate, comprises atomizing chamber, in which coating solution or coating dispersion is converted into aerosol by series of ultrasound sources having ultrasonic atomizer - Google Patents

Abstract

The coating device (01) comprises an atomizing chamber (02), in which a coating solution (03) or coating dispersion is converted into an aerosol by a series of ultrasound sources (05) having an ultrasonic atomizer (04). The flat sheet die (15) forms a width of its outlet port (22) in the area of the width of a substrate (24).

Description

The invention relates to a coating apparatus for a substrate having a Zerstäubungsraum in which a coating solution or dispersion is transferred by means of at least one row of ultrasonic sources having ultrasonic atomizer in an aerosol, and with a flowing transport gas for forwarding the aerosol to a slot die over the aerosol is directed onto the substrate in a wide front, wherein the slot die has a width of its exit opening in the region of the width of the substrate.

Coating devices are known in various technical fields of application and basically serve to apply a kind of coating to a suitable substrate, i. H. on a carrier material. Coating devices operate automatically, replacing manual coating operations. The substrate can be introduced as a single substrate or as a roll substrate. The coatings can be made by different methods, for example by vapor deposition or by sputtering. The present invention is concerned with the coating of a substrate with a material which is previously dissolved in a solvent and converted into ultrafine droplets by means of an ultrasonic atomizer (ultrasonic nebulizer). This process is called nebulization or nebulization. It forms an aerosol (also referred to as spray) as a mixture of droplets and a gas, which is conducted by means of a transport gas to the substrate and deposited there. Subsequently, the coating can be completed by evaporation of the solvent or by a reaction with other materials or by further processing steps, such as heating.

STATE OF THE ART

A good overview of the field of ultrasonic atomization is the publication "Techniques and Applications of Ultrasonic Atomization - A Review of 35 Years of Research and Development" (EG Lierke, Chemie Ingenieur Technik (70) 7/98, pp 815-826). refer to. For an even, large-scale distribution of an aerosol, an "umbrella vaporizer" of the Batelle Institute is reported here.

From the EP 0 860 211 A1 a device with an ultrasonic atomizer is known in which a plurality of ultrasonic sources are arranged in a circle. Furthermore, from the DE 34 34 11 A1 a liquid atomizer is known in which an indirect atomization with a coupling liquid for the transmission of vibrations is used to avoid residual liquid.

The from the EP 0 411 499 A1 known apparatus for coating a substrate with a liquid resist layer is to be further developed so that the homogeneity, the uniformity and the anchoring of the layer structure of the coating on the substrate at high coating speed and low drying costs for the applied layer structure can be increased. For this purpose, the known coating device has an atomization space in which a coating solution or dispersion containing evaporable solvent and solid components is transferred by means of an ultrasonic atomizer into an aerosol and is then passed with a flowing transport gas to a slot die. The coating solution is in direct contact with the ultrasound sources of the ultrasonic atomizer so that no aggressive coating solutions can be used. The ultrasonic sources are arranged in a single row and are overflowed in the longitudinal direction of the transport gas, so that the concentration of aerosolized particles in the transport gas increases increasingly, which can lead to inhomogeneities in the aerosol. About the slot die, the aerosol is then passed in a wide front on the substrate, the slot die is adapted in width to the width of the substrate. Before that, the aerosol still passes through an evaporation chamber in which the solvent is evaporated by heating. Thus, the slot die is the exit nozzle of the vaporization chamber, not further explained as the transition between the vaporization chamber and the entrance port of the slot die is made. The substrate is passed as a roller substrate evenly past the slot die. In the region of the slot die, a suction channel is provided above the substrate for sucking off non-deposited material.

The closest prior art from which the present invention is based is disclosed in U.S.P. US Pat. No. 4,656,963 disclosed. From this, a coating apparatus for a substrate with an atomization space is known, in which a coating solution is transferred into an aerosol by means of an ultrasonic atomizer, and with a flowing transport gas for the delivery of the aerosol to an exit opening of the atomization space, wherein the ultrasonic sources are covered with a coupling liquid, into which the atomization chamber with its lower area dives. In the known coating apparatus, however, the atomization space and the transport gas are put under a high pressure. About pressure valves, the transport gas is forced into the Zerstäubungsraum, a suction, the aerosol is in a directed to additional collection chamber. This arrangement results in a special function of the aerosol transport and a special basic geometry of the sputtering chambers. Accordingly, special suction devices and additional collection chambers are required in the known coating device.

TASK

The TASK for the present invention is to provide a generic coating device, in which a good homogeneity of the aerosol is achieved directly before application to the substrate with the least possible expenditure on equipment, so that the most uniform possible coating of the substrate can be achieved. In this case, the highest possible coating rate should be achieved. Furthermore, the coating device should be insensitive to the use of aggressive coating solutions. The solution according to the invention for this task can be found in the main claim, advantageous developments of the invention are shown in the subclaims and explained in more detail below in connection with the invention.

The coating device according to the invention is characterized according to the invention by a number of features. First of all, the slot die is designed as the exit nozzle of the atomization chamber. An evaporation chamber between atomization chamber and slot die is eliminated, so that no inhomogeneities can occur due to uneven evaporation. Furthermore, a further slot die is provided as the inlet nozzle of the atomization space for introducing the transport gas. By the inlet of the transport gas thus also no turbulence can arise, the transport gas is injected uniformly over the entire width of the slot die as an input nozzle. Furthermore, the outlet opening of the inlet nozzle is arranged parallel to the inlet opening of the outlet nozzle. This results in an undisturbed laminar, turbulence-free flow through the atomization space. This is further assisted by providing equal widths of the exit opening of the entrance nozzle, the entrance opening of the exit opening and the atomization space in a region of the substrate width. Thus, in the invention, the essential aerosol guiding elements are all sized the same width: the outlet opening of the inlet nozzle, the complete atomization space and the complete outlet nozzle with inlet and outlet openings, which allows a completely turbulence-free flow of the aerosol. In order for the aerosol to be generated uniformly even over the entire width of the atomization space, it is provided in the case of the coating device according to the invention that the at least one row of ultrasound sources is arranged over the entire width of the outlet opening of the inlet nozzle. All ultrasound sources in a row are thus overflowed simultaneously in the transverse direction.

Finally, in the case of the coating apparatus according to the invention, the ultrasonic atomizer is still uncoupled from the coating solution, so that it can not attack the ultrasound sources. Thus, aggressive coating solutions, such as solutions diluted with solvent, can be used. For this purpose, in the invention, the ultrasound sources are covered with a coupling liquid into which the atomization space immersed liquid-tight above the ultrasonic transducer.

The very high homogeneity of the coating that can be achieved in the coating device according to the invention is partly due to the particularly uniform generation and guidance of the aerosol. To avoid any turbulence, all aerosol-carrying components have the same width. The aerosol is then evenly generated by the ultrasound sources over this width. Another measure for avoiding turbulence is advantageously in an opposing arrangement of the inlet nozzle and outlet nozzle in a secant plane of the cylindrically shaped atomization chamber. The aerosol rises in the atomization chamber, enters the transport gas stream and is continuously transported in the direction of the outlet nozzle. In addition, advantageously, the transition between the atomization chamber and the inlet opening of the outlet nozzle have rounded edges, so that no vortex corners can arise here.

In this sense, has emerged as a particularly advantageous form for the Zerstäubungsraum a cylindrical design that avoids especially corners and edges and can be particularly well integrated between the inlet and outlet nozzle above the Ultraschallzerstäubers. As dimensions, a diameter of the cylindrically shaped atomizing space in a range of 10 cm and / or a wall thickness of a cylindrically shaped atomizing space in a range of 0.5 mm has advantageously resulted. By such a thin walling the vibrations of the ultrasonic vibrator can be well transferred via the coupling fluid. This is further enhanced if it is a flexible wall. As atomization space plastic containers are therefore particularly well suited. These can be transparent in order to be able to clearly recognize the filling level of the coating solution on the inside. Regardless, the Level of course also detected by electrical or optical level sensors.

Irrespective of the extent of the atomization chamber, the invention has a particularly good atomization performance when the atomization space is filled up to one third of its maximum height with the coating solution. For a cylinder, this corresponds to one third of its diameter. At such a filling height, on the one hand, the coating solution is completely penetrated by the ultrasonic waves, on the other hand reaches the rising aerosol quickly and evenly laminar outflow between the inlet and outlet nozzle.

Due to the uniformity of the width of the inlet and outlet openings of the outlet nozzle results in a flat course of the outlet nozzle. The characteristic nozzle constriction occurs in the vertical direction at the transition between the atomization space and the substrate. Advantageously, the flat exit nozzle can therefore have a curved course with a rising portion behind the atomization space and a portion sloping towards the substrate. Due to the first rising portion, a reflux of any resulting condensate from the aerosol into the atomization space is achieved. The sloping second portion supports by gravity the uniform coating of the substrate. Alternatively, the flat exit nozzle can advantageously also be made flexible so that a simple adaptation to any structural conditions within the coating device and with respect to the substrate is possible.

In order to increase the atomization power, in the case of the coating device according to the invention it can furthermore be advantageously provided that a plurality of parallel rows of ultrasound sources are arranged in front of the outlet opening of the inlet nozzle. In this case, the ultrasound sources between the individual rows can advantageously be arranged offset from one another, resulting in a further homogenization of the atomization of the coating solution.

In order to improve the adhesion of the aerosol to the substrate, it is further advantageous in the case of the invention for a counterpolar electrostatic charging of the coating solution and the substrate to be provided. In addition to the adhesion, electrostatic forces also occur for attachment, but they can be neutralized in the further course of the process.

As a coating solution, any solution can be used. In particular, aggressive coating solutions can also be used in the coating device according to the invention, since direct contact with the ultrasound sources is avoided. Advantageously, therefore, an alcohol-containing precursor solution can be used as a coating solution. Furthermore, preference may be given to using nitrogen as the transport gas and water as the coupling liquid. These are inexpensive, harmless media. In the parameter setting, a volume flow of the transport gas in a range of 15 l / min, a sputtering rate of each ultrasonic source of 1.5 ml / min at a sound frequency of MHz of the ultrasonic sources may be preferably selected. The result is a homogeneous aerosol with a droplet size of 2 microns-5 microns, which can be optimally deposited on the substrate. Here, "optimal" means maximum deposition at maximum feed rate of the substrate so that cost effective high efficiency can be achieved.

In particular, the coating device according to the invention can advantageously be used in a coating of a substrate according to the ILGAR (Ion Bearing Gas Reaction) method. For this purpose, it is advantageous if in the coating device, a coating chamber is still provided, in which the outlet nozzle is inserted. The substrate, which may be made-up pieces (glass) or a continuous material made of metal or plastic, is guided by a treadmill into the coating chamber through locks and coated there beneath the exit die. The transport gas is removed via a discharge. The coated substrate is then led out of the coating chamber via sluices on the treadmill. In the ILGAR process, a precursor solution of, for example, a metal salt dissolved in ethanol is used as the coating solution. This is atomized and supplied to the substrate as an aerosol. Subsequently, the solvent is evaporated (or evaporated) and the metal particles adhere by pure adsorption evenly on the - if necessary, also undercut - surface of the substrate. After coating in the coating chamber, the substrate is transferred to a reaction chamber into which a chalcogen hydrogen gas is introduced. The chalcogen reacts with the metal deposit on the substrate and forms an extremely resistant metal chalcogenide layer, which can be used for a wide variety of purposes, but especially as a buffer layer (indium sulfide) in solar technology. In particular, when using the coating device according to the invention in the ILGAR process, their advantages in the form of almost any Aufskalierungsmöglichkeit the device, in which the atomized aerosol with consistently fine droplets below 5 microns in diameter on a wide, rapidly moving substrate with a high Atomizer performance can be sprayed particularly evenly.

Further details on the inexpensive and easy-to-maintain coating device according to the invention for particularly uniform atomization and spraying of large volumes of liquid can be found in the following special description part.

Embodiment

Embodiments of the coating apparatus according to the invention are explained in more detail below with reference to the schematic figures for further understanding of the invention. Showing:

1 a cross section of the coating device

2 a perspective view of the coating apparatus,

3 a plan view of the coating apparatus and

4 the coating device with other components.

The 1 shows the coating device 01 according to the invention in a cross section. Shown is a cylindrically shaped atomization space 02 in which is a coating solution 03 (or coating dispersion, such as precursor solution) is located. Optimal is the atomization space 02 up to a third of its height H with the coating solution 03 filled. The atomization room 02 is above an ultrasonic atomizer 04 arranged, the multiple ultrasound sources 05 includes. The ultrasound sources 05 are in a coupling fluid 06 (For example, water) for transmitting the sound waves to the coating solution 03 in the atomization room 02 , The coupling fluid 06 is in a container 07 filled and serves to avoid the contact of coating solution 03 and ultrasound sources 05 , In the atomization room 02 becomes the coating solution 03 atomized by the action of ultrasonic waves and in an aerosol 08 (finely divided liquid droplets in gas) transferred.

In an upper area 09 of the spraying room 02 are an input nozzle 10 and an exit nozzle 11 in a common secant plane 12 of the cylindrical atomization space 02 arranged. Through the inlet nozzle 10 becomes a transport gas 13 (For example, nitrogen N ₂ ) in the Zerstäubungsraum 02 initiated, then with the atomized coating solution 03 as an aerosol 08 through the exit nozzle 11 from the atomization room 02 flows.

In the 2 is the coating device 01 according to 1 presented in perspective. Evident is the cylindrical (for example diameter 10 cm) Zerstäubungsraum 02 that with the coating solution 03 is filled and in its lower part 14 from the coupling fluid 06 for decoupling the coating solution 03 from the corrodible ultrasound sources 05 of the ultrasonic atomizer 04 is surrounded. Good to see is the design of the input nozzle 10 and the exit nozzle 11 as slot dies 15 , The inlet nozzle 10 has accordingly a wide exit opening 16 on, by the supplied transport gas 13 in a broad front 17 in the upper area 09 the atomization room 02 flows. An entrance opening 30 the inlet nozzle 10 for supplying the transport gas 13 is designed with a smaller width to facilitate the gas supply, for example, from a supply line. But it can be seen how the width of the input nozzle 10 towards the exit opening 16 increasingly extended, so that possibly occurring turbulence in the transport gas 13 be dissolved. Together with the atomized coating solution 03 the transport gas flows 13 (maximum volume flow 15 l / min) as aerosol 08 then through a wide entrance opening 18 into the outlet nozzle 11 , In this case, the inlet opening 18 the outlet nozzle 11 rounded edges 19 on to avoid turbulence at the transition. Furthermore, in the selected embodiment, the exit nozzle 11 a curved course with an increasing share 20 at the entrance opening 18 for a possibly occurring condensate reflux and a falling portion 21 at an exit opening 22 , About this is the aerosol 08 then in a broad front 23 towards a substrate 24 blown.

Good to see in the 2 in that to equalize the flow and to obtain an optimum coating rate, the outlet opening 16 the inlet nozzle 10 , the atomizer room 02 and entrance opening 18 as well as exit opening 22 the outlet nozzle 11 approximately the same width in the width of the substrate 24 exhibit. In addition, the exit opening 16 the inlet nozzle 10 parallel to the entrance opening 18 the die 3 shows the coating device 01 according to the invention in a plan view. In addition to the known components (see previous FIGURES and description) is in particular the structure of the ultrasonic vibrator 04 to recognize. Shown is the arrangement of the ultrasound sources 05 (maximum sputtering rate, for example, 1.5 ml / min at a frequency of 2 MHz) in a row 25 parallel to the exit opening 16 the inlet nozzle 10 , Thus, the ultrasound sources become 05 across from the transport gas 13 overlined, so that it can not lead to inhomogeneities in the aerosol distribution. Furthermore, another series 26 of ultrasonic transducers 05 shown, which are also parallel to the exit opening 16 the inlet nozzle 10 are arranged. These are the ultrasound sources 05 the series 25 offset to the ultrasound sources 05 the series 24 arranged. Because the exit opening 16 the inlet nozzle 10 parallel to the entrance opening 18 the outlet nozzle 11 is arranged, so are all rows 25 . 26 from ultrasound sources 05 parallel to the outlet nozzle 11 arranged. More rows of ultrasound sources 05 can be provided which then the entire cross section of the atomization space 02 to capture. This will surely ensure that the entire coating solution 03 of ultrasonic waves (preferably 2 MHz) excited and the aerosol 08 is generated evenly.

Furthermore, in the 3 shown that in the selected embodiment, each ultrasonic source 05 over a sound membrane 27 , a level sensor 28 and an electrical connection 29 features.

In the 4 is a coating device 01 according to the invention with additional components for an automated coating. Evident is a gas-tight coating chamber 31 through which a treadmill 32 the substrate 24 to be led. In the entrance area 36 the coating chamber 31 is an entrance lock 33 for gas-tight insertion of the substrate 24 , in the exit area 37 an exit lock 34 for gas-tight execution of the substrate 24 intended. The outlet nozzle 11 the coating device 01 reaches into the coating chamber 31 until just above the moving substrate 24 into it, so that the aerosol 08 can be passed directly to the substrate surface. The coating 38 takes place over the entire width of the substrate 24 , The transport gas 13 (without the nebulized coating droplets) is via a derivative 35 from the coating chamber 31 brought out again.

That with the coating 38 wetted substrate 24 can then be dried so that the applied precursor materials, for example a metal salt, which is dissolved in an aggressive alcohol solution, by adsorption to the substrate 24 hold. In a further process step, for example, a chalcogen hydrogen gas can then be conducted onto the surface, so that the chalcogen then combines with the metal to form a solid component (ILGAR process, compare, for example DE 101 60 504 C2 . DE 198 31 214 C2 . DE 199 16 403 C1 ). This results in a homogeneous large-area coating 38 with droplet sizes of the aerosol 08 from 2 μm to 5 μm. In this case, a maximum possible ratio of the sputtering rate to the sprayed area width of the substrate 24 of 0.6 ml / min cm (at least 0.4 ml / min cm). This layer can be used, for example, as a buffer layer in a thin-film solar cell assembly with a plastic substrate.

LIST OF REFERENCE NUMBERS

01

coater

02

nebulization

03

coating solution

04

ultrasonic nebulizer

05

ultrasound source

06

coupling fluid

07

container

08

aerosol

09

upper area of 02

10

inlet nozzle

11

outlet nozzle

12

secant

13

transport gas

14

lower area of 02

15

slot die

16

Exit opening of 10

17

wide front of 16

18

Entrance opening of 11

19

rounded edge

20

increasing share of 11

21

decreasing share of 11

22

Exit opening of 11

23

wide front of 22

24

substratum

25

a row of 05

26

another series of 05

27

sound membrane

28

level sensor

29

electrical connection

30

Entrance opening of 10

31

coating chamber

32

treadmill

33

entry lock

34

exit lock

35

derivation

36

entrance area

37

output range

38

coating

H

Height of 02

Claims (13)

Coating device ( 01 ) for a substrate ( 24 ) with an atomization space ( 02 ), in which a coating solution ( 03 ) or dispersion by means of at least one row ( 25 ) of ultrasound sources ( 05 ) having ultrasonic atomizer ( 04 ) in an aerosol ( 08 ), and with a flowing transport gas ( 13 ) for the delivery of the aerosol ( 08 ) to a slot die ( 15 ) through which the aerosol ( 08 ) in a broad front ( 23 ) on the substrate ( 24 ), wherein • the slot die ( 15 ) a width of its exit opening ( 22 ) in the region of the width of the substrate ( 24 ) and as exit nozzle ( 11 ) of the atomization space ( 02 ), • another slot die ( 15 ) as an inlet nozzle ( 10 ) of the atomization space ( 02 ) for the introduction of the transport gas ( 13 ), the exit opening ( 16 ) of the input nozzle ( 10 ) parallel to the entrance opening ( 18 ) of the outlet nozzle ( 11 ), the exit opening ( 16 ) of the input nozzle ( 10 ), the entrance opening ( 18 ) of the outlet nozzle ( 11 ) and the atomization space ( 03 ) in approximately equal widths in a range of the width of the substrate ( 24 ), the at least one row ( 25 ) of ultrasound sources ( 05 ) across the broad front ( 17 ) of the exit opening ( 16 ) of the input nozzle ( 10 ) and • the ultrasound sources ( 05 ) with a coupling fluid ( 07 ) are covered, in which the atomization space ( 02 ) in its lower area ( 14 ) dips liquid-tight. Coating device ( 01 ) according to claim 1, characterized by rounded edges ( 19 ) of the entrance opening ( 18 ) of the outlet nozzle ( 11 ) at the atomization room ( 02 ). Coating device ( 01 ) according to claim 1, characterized by a cylindrical formation of the atomization space ( 02 ). Coating device ( 01 ) according to claim 3, characterized by an opposing arrangement of inlet nozzle ( 10 ) and exit nozzle ( 11 ) in a secant plane ( 12 ) of the cylindrical spray chamber ( 02 ). Coating device ( 01 ) according to claim 3, characterized by a diameter of the cylindrical spray chamber ( 02 ) in a range of 10 cm and / or a wall thickness of the cylindrical spray chamber ( 02 ) in a range of 0.5 mm. Coating device ( 01 ) according to claim 1, characterized by a filling of the atomization space ( 02 ) up to one third of its maximum height (H) with the coating solution ( 03 ). Coating device ( 01 ) according to claim 1, characterized by a curved course of the outlet nozzle ( 11 ) with an increasing proportion ( 20 ) in the area of the entrance opening ( 18 ) and a decreasing share ( 21 ) in the region of the exit opening ( 22 ) of the outlet nozzle ( 11 ). Coating device ( 01 ) according to claim 1, characterized by a flexible design of the outlet nozzle ( 11 ). Coating device ( 01 ) according to claim 1, characterized by a plurality of parallel rows of ultrasonic sources along the width of the exit opening of the entrance nozzle, the ultrasonic sources being arranged offset from each other between the individual rows. Coating device ( 01 ) according to claim 1, characterized by a gegenpolige electrostatic charging of coating solution ( 03 ) and substrate ( 24 ). Coating device ( 01 ) according to claim 1, characterized by an alcohol-containing precursor solution as coating solution ( 03 ) and / or nitrogen as transport gas ( 13 ) and / or water as coupling fluid ( 07 ). Coating device ( 01 ) according to claim 1, characterized by a volume flow of the transport gas ( 13 ) in a range of 15 l / min and / or a sputtering rate of each ultrasound source ( 05 ) of 1.5 ml / min at a sound frequency of MHz and / or a droplet size of 2-5 μm. Coating device ( 01 ) according to claim 1, characterized by providing a coating chamber ( 31 ) into which the exit nozzle ( 11 ) with a treadmill ( 32 ) for transporting the substrate ( 24 ), a derivative for the transport gas ( 13 ) from the coating chamber ( 31 ) and several locks ( 33 . 34 ) in the input and output area ( 36 . 37 ) of the coating chamber ( 31 ) for the substrate ( 24 ).

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