Patent Application
20210086221
The present invention pertains to a slot-the coating apparatus.
The present invention further pertains to a slot-die coating method.
Organic coatings layers are typically applied to a substrate as a liquid solution, e.g. for manufacturing OLED or PV devices. For many applications, e.g. manufacturing of photo-active layers and/or light-emitting layers, it may be desired to provide one or more homogeneous coating layers on a substrate, i.e. having a homogeneous layer thickness. One technique for manufacturing a homogeneous coating layer may be referred to as “slot-the coating”. This technique typically comprises providing a slot-the coating head arranged over a substrate surface. The slot-die coating head comprising an outflow opening forming a slit that is arranged in a slit direction over the substrate surface. A coating fluid, e.g. supplied by a coating fluid supply, flows through the outflow opening onto the substrate surface. A relative movement between the outflow opening and the substrate surface is controlled along a coating direction. The coating direction is typically transverse, i.e. having a perpendicular component, to the slit direction. In this way a homogeneous layer may be manufactured along a width of the slit onto the substrate surface.
In addition to having a homogeneous coating layer, it may be desired to provide a patterning of the coating on the substrate surface, e.g. wherein the patterned coating comprises coated areas on the substrate surface separated by uncoated areas. For example, for the manufacture of photo-active layers and/or light-emitting layers it may be desired to provide separated active areas on a substrate, e.g. for building an array of photo-cells.
From JP2009028605 a slot-the coating apparatus is known that provides for an intermittent transfer coating fluid from the slot-the coating head onto the substrate surface. To that end the coating apparatus the slot-die coating head has a manifold with an inlet coupled to a liquid feed pump and an outlet coupled to an intermittent discharging mechanism. The latter comprises a first and a second valve for opening and closing the circulation line. The first valve is arranged directly stream downward of the outlet and the second valve is arranged stream downward with respect to the first one. The intermittent discharging mechanism further comprises a sucking pump that is communicatively coupled to a portion of the circulation line between the first and the second valve.
In operation the slot-die coating apparatus has a first operational mode, wherein the first valve is closed as a result of which the coating fluid flows to the outflow opening of the coating head for deposition on the substrate. The slot-die coating apparatus has a second operational mode, wherein the first valve is open and the second valve is closed, while the suction pump pumps coating liquid out of the manifold. As a result a flow of coating fluid from the outflow opening is interrupted. When the apparatus returns to its first operational mode, with the first valve in its closed state and the second valve in an opened state, the suction pump discharges the liquid pumped during the second mode back into the reservoir via the open second valve.
Unfortunately, it is found that an intermittent switching of the supply and/or removal and reapplication of the coating head may result in edge effects wherein the coating is no longer uniform e.g. due to the accumulation of coating material on the coating head. This applies in particular to coating liquids having a relatively low viscosity, e.g. in the range of 1 to 10 mPa·s. Typically, when slot-the coating such low-viscosity liquid a substantial amount thereof may be present between the outflow opening of the coating head and the surface of the substrate to be coated. For example an amount of coating liquid may be present on the outflow opening at a thickness that substantially exceeds a thickness with which the coating liquid is deposited on the substrate.
It is an object of the invention to provide a slot-die coating apparatus and a slot-die coating method that enable a more uniform thickness of the coated layer near its edges.
In accordance therewith a coating apparatus is provided for manufacturing a patterned coating layer on a substrate surface of a substrate. The apparatus comprises a slot-die coating head, a coating fluid supply system, a controller for controlling the coating fluid supply system, and a substrate carrier for carrying the substrate. The slot-die coating head comprises an inlet for receiving coating fluid from the coating fluid supply system and a slit-shaped outflow opening communicatively coupled to the inlet and having a slit direction. In use the controller alternately causes the coating fluid supply system to operate in a first mode to provide for a flow of coating fluid out of the slit-shaped outflow opening for deposition on the substrate surface and in a second mode wherein a deposition of coating fluid onto the substrate surface is interrupted. The coating head has an internal coating fluid trajectory extending from the inlet to the slit-shaped outflow opening. In a stream-downwards order the coating fluid trajectory comprises a lateral distribution portion to distribute a flow of fluid over the slit direction, a collection channel extending transverse to the stream-downwards direction, and a flow resistive output portion. Upon a transition from the first mode to the second mode the controller causes the coating fluid supply system to suck coating fluid from the at least one outlet of the slot-die coating head that is communicatively coupled to the collection channel. In this transitional stage the combination of the above-mentioned subsequent elements in the internal coating fluid trajectory provide for a controlled and homogeneously distributed reflow of coating fluid into the slot-die coating head, therewith causing excess coating fluid outside the slit-shaped outflow opening (22) to flow via the flow resistive output portion, via the collection channel (24) to said at least one outlet. The controller for controlling the coating fluid supply system may be provided in any of various implementations, for example as dedicated hardware, as a suitably programmed general purpose processor or as a combination of dedicated and programmable elements. The controller may additionally be configured to control other units of the apparatus, for example a position of the coating head, a substrate transport velocity, and quality maintenance.
According to another aspect a slot-die coating method is provided for manufacturing a patterned coating layer on a substrate surface of a substrate using a slot-die coating head and a substrate carrier for carrying the substrate. The method comprises alternately operating in a first mode and a second mode. In the first mode coating fluid is supplied to the inlet of the coating head and laterally distributed in the lateral distribution portion. Subsequently the coating fluid flows via the flow resistive output portion to the outflow opening for deposition on the substrate. In the second mode M2 a deposition of coating fluid is interrupted. In particular in a transitional phase of the second mode M2 following the first mode a suction is applied to the at least one outlet. This causes excess coating fluid outside the slit-shaped outflow opening to flow in a laterally homogenously distributed manner via the flow resistive output portion, via the collection channel to the at least one outlet.
In embodiments the flow resistive output portion may have a flow resistance that is in a range between 0.05 times and 1 times a flow resistance of the lateral distribution portion, preferably in a range of 0.15 to 0.45.
These and other aspects are described in more detail with reference to the drawing. Therein:
Like reference symbols in the various drawings indicate like elements unless otherwise indicated.
The apparatus comprises a slot-the coating head 2, a coating fluid supply system 7, a controller 9 for controlling the coating fluid supply system, and a substrate carrier 6 for carrying the substrate 1. In an embodiment the substrate carrier 6 may provide for a fixed support of the substrate, and the coating head may be displaced at a velocity vhead as indicated in
The slot-die coating head 2 comprises an inlet 21 for receiving coating fluid from the coating fluid supply system 7 and a slit-shaped outflow opening 22 that is communicatively coupled to the inlet and that has a slit direction y. In use the controller 9 applies control signal C7that alternately causes the coating fluid supply system 7 to operate in a first mode M1 and a second mode M2. In the first mode M1 it provides for a flow Vout of coating fluid out of the slit-shaped outflow opening 22 for deposition on the substrate surface 1s. In the second mode M2 a flow of coating fluid out of the slit-shaped outflow opening 22 is interrupted 21. The coating head 2 has an internal coating fluid trajectory extending from the inlet 21 to the slit-shaped outflow opening 22. The coating fluid trajectory comprises in a stream-downwards order a lateral distribution portion 23, a collection channel 24 and a flow resistive output portion 25.
In operation, the lateral distribution portion 23 distribute a flow of fluid over the slit direction y. In the embodiment shown the lateral distribution portion 23 comprises a comprises a lateral distribution channel 23a and a distribution gap 23b having a relatively high flow resistance in comparison to a flow resistance of the lateral distribution channel 23a.
The flow resistance R, in Pa·s·m−3, of a trajectory portion may be approximated by the following approximation based on the Poisseuille equation:
Therein η is the dynamic viscosity of the fluid in Pa·s, Lst is the length of the trajectory in the flow direction in m, and W and h are the width the height of the trajectory portion in m.
In the embodiment shown the distribution gap 23b has a length l23b and a height h23b. The flow resistance of the distribution gap is substantially proportional to a ratio length l23b/h23b. By way of example the distribution gap may have a height h23b of 25 to 500 micron and a length l23b of 10 to 50 mm, wherein the ratio is in the range of 50 to 500. If this ratio is substantially less than 50, e.g. less than 10 than the flow may be insufficiently distributed in the lateral direction, and the ratio is substantially higher than 500, e.g. higher than 1000 than an unnecessary high load of the supply may result, at a relatively modest additional improvement of the lateral distribution.
Stream downwards of the lateral distribution portion 23, a collection channel 24 is provided that extends in a direction transverse to the stream-downwards direction. The collection channel 24 is communicatively coupled to one or more outlets. In the embodiment shown in
The controller 9 is configured to cause the coating fluid supply system 7 to suck coating fluid from the outlet 26 of the slot-die coating head 2 upon a transition from the first mode M1 to the second mode M2. This suction of coating fluid may proceed during the second mode M2, to compensate for the supply of coating fluid from outlet 71 of the coating fluid supply system 7. Alternatively, this suction may be performed during a suction time interval shorter than the duration of the second mode M2 such that during the suction time interval an excess amount of fluid is sucked from the outflow opening 22 and possibly a portion of the flow resistive output portion 25, while during the remainder of the second mode the supply Vsupply of coating fluid provides for a renewed formation of a bead of coating fluid at the outflow opening 22, possibly preceded by a refilling of the flow resistive output portion 25.
By way of example,
In a typical example a distance between the coating head and the substrate may be in a range of 25500 μm, a viscosity of the coating fluid 1-100 mPa·s, a nozzle cross-section diameter 25-350 μm, a relative speed between the coating head and substrate 3-30 metres per minute, a wet coating layer thickness 5-100 μm, e.g. 10 to 50 μm. Coating parameters may be determined e.g. experimentally and/or by model calculations.
As shown in
Whereas in this example the amount Q decreases to 0, also embodiments are conceivable wherein the amount is reduced to a value between 0 and QM1. Also embodiments are conceivable wherein the amount Q is reduced to a negative value, implying that also the flow resistive output portion 25 is (partially) discharged.
As indicated above, during the remainder t1a to t2, for example as illustrated for a point in time tc in
The coating fluid supply system 7 in this embodiment further comprises a suction pump 75 for sucking a discrete amount of coating fluid. Hence, upon each activation the suction pump 75, e.g. by control signal C75a, the suction pump 75 suck a preset quantity of coating fluid from the outlet 26. In the embodiment shown the suction pump 75 is provided to drain the discrete amount of fluid into the reservoir 73. To that end valves 76, 77 are provided that are controlled by the controller 9 with respective control signals C76, C77. In another embodiment the valves 76, 77 may operate autonomously. For example valve 76 may be arranged as a one-way valve that automatically opens if a pressure difference P1-P2 exceeds a threshold value. In this way it is prevented that during operation in mode M1 coating fluid flows away via return channel 27, whereas a flow of coating fluid is enabled in the transition from mode M1 to mode M2. The second valve can also be provided as a one-way valve, but its threshold can be arbitrary low.
In an embodiment, for example the embodiment of
In the embodiment shown the controller controls the position of the stopper 755 to automatically regulate an amount of sucked coating fluid.
The ratio between the flow resistance in the lateral distribution portion 23 and in the flow resistive output portion 25 can also be expressed as a ratio of the pressure drops ΔP1/ΔP2 occurring in these portions during operation in the first mode. This is schematically indicated in
Exemplary embodiments of the coating head as illustrated in
For comparison the pressure drop in remaining parts of the fluid supply system is substantially lower. For example the pressure drop in the supply line towards the inlet 21 is merely 4 mPa, i.e. its magnitude is at least three orders of magnitude lower than that in the portions 23b, 25 of the coating head 2. Similarly, the pressure drop in the distribution channel 23a and the collection channel 24 is substantially lower, e.g. at least two orders of magnitude lower than those in the portions 23a, 25 respectively.
While example embodiments were shown for providing a coating layer on a substrate, also alternative ways may be envisaged by those skilled in the art having the benefit of the present disclosure for achieving a similar function and result. The various elements of the embodiments as discussed and shown offer certain advantages, such as providing homogeneous coating layers. Of course, it is to be appreciated that any one of the above embodiments or processes may be combined with one or more other embodiments or processes to provide even further improvements in finding and matching designs and advantages, e.g. combinations of slot die coating, intermittent coating, shim coating, and/or pre-patterning a substrate. It is appreciated that this disclosure offers particular advantages to the manufacture of solar cell arrays, and in general can be applied for any application of large-scale production of homogeneous patterned layers on a substrate or web.
Finally, the above-discussion is intended to be merely illustrative of the present system and should not be construed as limiting the appended claims to any particular embodiment or group of embodiments. Thus, while the present system has been described in particular detail with reference to specific exemplary embodiments thereof, it should also be appreciated that numerous modifications and alternative embodiments may be devised by those having ordinary skill in the art without departing from the scope of the present systems and methods as set forth in the claims that follow. The specification and drawings are accordingly to be regarded in an illustrative manner and are not intended to limit the scope of the appended claims.
In interpreting the appended claims, it should be understood that the word “comprising” does not exclude the presence of other elements or acts than those listed in a given claim; the word “a” or “an” preceding an element does not exclude the presence of a plurality of such elements; any reference signs in the claims do not limit their scope; several “means” may be represented by the same or different item(s) or implemented structure or function; any of the disclosed devices or portions thereof may be combined together or separated into further portions unless specifically stated otherwise. The mere fact that certain measures are recited in mutually different claims does not indicate that a combination of these measures cannot be used to advantage.
| Number | Date | Country | Kind |
|---|---|---|---|
| 17163635.0 | Mar 2017 | EP | regional |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/NL2018/050188 | 3/28/2018 | WO | 00 |
