Patent Application
20070207270
1. Field of the Invention
The present invention is related to a method and apparatus for a substrate being coated with a coating layer and particularly to a method of soak type coating and an apparatus thereof.
2. Brief Description of Related Art
Generally, after a substrate being immersed in coating liquid, velocity of the substrate separating from the liquid level of coating liquid and stickiness of the coating liquid affect thickness of the coating film on the substrate. Slower separating velocity and more stickiness result in thicker coating film. Faster separating velocity and less stickiness result in thinner coating film.
Taiwanese Patent Publication No. 590807 discloses an immersion coating device for a thin slat shaped substrate and the device provides a hanging actuation mechanism to place the thin slat shaped substrate in the soak trough of a immersion coating mechanism and take out the substrate after finishing coating.
The preceding hanging actuation mechanism has to be precisely controlled moving speed without swinging or it is hard to control thickness of the coating film on the thin slat shaped substrate.
U.S. Pat. No. 6,214,419 discloses an immersion coating process provides a coating vessel with coating mixture inside. After the substrate having been immersed in the coating mixture, the liquid level of the coating mixture descends a short distance before velocity of the coating mixture being discharged gradually increasing to the largest velocity. Afterwards, the coating mixture is discharged from the coating vessel with the largest velocity.
The preceding coating mixture is discharged from the coating vessel by a pump. Because the pump delivers the liquid by means of pulses, the liquid is delivered with inconstant flow speed and it leads to inconsistent separating velocity of the coating mixture from the substrate such that the coating film on the substrate is formed unevenly.
A main object of the present invention is to provide a method and an apparatus for soak type coating with which velocity of the liquid level of the coating liquid separating from the substrate is controlled steadily for the substrate obtaining preferable effect of coating.
Another object of the present invention is to provide a method and an apparatus for soak type coating with which specific gas is introduced into an air-tight coating container for the substrate obtaining preferable effect of coating.
The present invention can be more fully understood by reference to the following description and accompanying drawings, in which:
Referring to
The second pump 80 introduces gas into the second receiving trough 71 of the second container 70 to create gas pressure exerting to the liquid level of the coating liquid 20 in the second container such that the coating liquid 20 in the second container 70 is able to pass through the guide pipe 74, the valve 60, the guide pipe 52, the throat valve 50 and the guide pipe 51 before being introduced to the first receiving trough 11. In this way, at least part of the substrate 30 is immersed in the coating liquid 20 of the first receiving trough 11.
The first pump 40 introduces gas into the first receiving trough 11 of the first container 10 to create gas pressure at liquid level of the coating liquid 20 in the first container 10 for the coating liquid 20 in the first receiving trough 11 discharges via the second inlet/outlet port 14 at the lower end of the first container 10. When the outlet for discharging the coating liquid 20 is fixed in size, discharge velocity of the coating liquid 20 can be controlled by means of controlling velocity of the pumped gas entering the first receiving trough 11. Thus, descending velocity of the liquid level of the coating liquid 20 in the first receiving trough 11 can be controlled such that separation velocity of the liquid level of the coating liquid 20 from the substrate 30 is controlled for controlling thickness of coating film on the substrate 30.
Because gas is more compressible than liquid, the gas in the first receiving trough 11 provides steady pressure to exert force to the liquid level of the coating liquid 20 even if the first pump 40 introduces the gas into the first receiving trough 11 by pulse. Hence, the coating liquid 20 in the first receiving trough 11 is capable of discharging with a constant velocity and the liquid level of the coating liquid 20 in the first receiving trough 11 descends uniformly to separate from the substrate 30 such that homogeneous thickness of the coating film on the substrate 30 can be obtained with more preferable effect of coating.
The throat valve 50 regulates the outlet port of the first receiving trough 11 to control the discharge rate of the coating liquid 20 in the first receiving trough 11.
When the coating liquid 20 in the first receiving trough 11 is discharged, the valve 60 is in a state of opening and the discharged coating liquid 20 is able to flow into the second receiving trough 71 of the second container 70. The second pump 80 is employed to withdraw gas in the second receiving trough 71 to increase the discharge velocity of the coating liquid 20 in the first receiving trough 11.
The apparatus of the present invention further includes a support stand 31 for the substrate 30 being placed there on and for the substrate 30 being in and out the first receiving trough 11 conveniently. Further, the lower end of the first container 10 is placed on top of a cushion pad 90 to dampen vibration from the first container 10 for facilitating coating process. It is preferable that the cushion pad 90 is a gas cushion pad.
The first cover 12 and the second cover 72 are provided with an elastic ring for closing the openings 111, 721 air-tightly. The first and second covers 12, 72 are joined to the upper ends of first receiving trough 11 and the upper ends of the second receiving trough 71 respectively with screw rods 121, 721.
While the coating liquid 20 in the second container 70 is guided into the first container 10, it is capable of allowing the first pump 40 withdrawing gas in the first container 10 at the same time and the second pump 80 introduces the gas into the second container 70 to speed up the coating liquid 20 in the second container 70 being introduced into the first container 10. The valve 60 is in a state of opening right at this time.
The gas, which is introduced into the first container 10 by the first pump 40, can be, for instance, air, nitrogen or any other idle gas depending on chemical property of the coating liquid 20 to avoid chemical reaction between the coating film on the substrate 30 and the gas molecules for obtaining better quality with desirable effect of coating.
Referring to
(1) The substrate 30 is placed in the first container 10, which has the cover 12, and the coating liquid 20 is introduced into the first container 10 with at least part of the substrate 30 emerged in the coating liquid 20;
(2) The first pump 40 induces the gas into the first container 10 via the first inlet/outlet port 13 at the top of the first container 10 to create air pressure exerting the liquid level of the coating liquid 20 and to allow the the substrate 30 emerged in the coating liquid 20; coating liquid 20 discharging via the second inlet/outlet port 14 at the bottom of the first container 10 such that the liquid level of the coating liquid 20 in the first container 10 descends gradually to separate from the substrate 30 and the surface of the substrate 30, which touches the coating liquid 20, is covered with a coating layer;
Wherein, the first pump 40 is regulated to adjust velocity of the gas entering the first container 10 to control discharge velocity of the coating liquid 20 in the first container 10 so as to control separation velocity of coating liquid 20 in the first container 10 from the substrate 30 for controlling thickness of the coating layer on the substrate 30.
The method of the present invention further including a step of the throat valve 50, which communicates the second inlet/outlet port 14 of the first container, controlling discharge velocity of the coating liquid 20 in the first container 10 and the discharge liquid 20 entering the second container 70 after passing the valve 60 and the second inlet/outlet port 74 at the bottom of the second container 70. The second pump 80 sucks gas in the second container 70 out via the first inlet/outlet port 73 at the top of the second container 70 to increase the discharge velocity of the coating liquid in the first container 10. Other implements of the method according to the present invention have been described in the preceding apparatus of the invention.
It is appreciated that the invention allows descending velocity of the liquid level of the coating liquid being controlled steadily for enhancing quality of soak type coating and introduces gas unable to create chemical reaction with the coating liquid easily for the substrate obtaining better effect of coating.
While the invention has been described with referencing to a preferred embodiment thereof, it is to be understood that modifications or variations may be easily made without departing from the spirit of this invention, which is defined by the appended claims.
