Abstract:
Abstract of the disclosure The present invention provides a method and an apparatus for a glow discharge plasma surface treatment of flexible sheet materials under atmospheric pressure. The apparatus comprises electrodes, a single plasma-gas flow channel, uniform gas inlet-and-outlet devices, gas-seal devices for the horizontal movements of sheet materials and reel devices, so as to attain an uniform distribution of plasma gases in the gap between electrodes. As a result, not only a great amount of expensive plasma gas is saved, but also an uniform glow discharge plasma is generated at the lowest input power to obtain a good quality of uniform plasma treatment with continuous processing and high production.

Description:
FIELD OF THE INVENTION  
       [0001]     The present invention relates to a method and its associated apparatus for a surface treatment of flexible materials with an atmospheric pressure glow discharge plasma; more particularly, relates to an apparatus for a surface treatment of flexible sheet materials done by a glow discharge plasma under atmospheric pressure where a good quality of uniform treatment is obtained and a great amount of plasma gas is saved with continuous processing and high production.  
       DESCRIPTION OF THE RELATED ARTS(S)  
       [0002]     Since Kanazawa et al. first found in 1988 that a stable atmospheric pressure glow discharge plasma could be generated under certain circumstances, a lots of plasma experts around the world has been enthusiastically devoted their efforts to the development of the atmospheric pressure glow discharge plasma sources due to its great potential in industrial applications. Among them, the atmospheric plasma apparatus capable of continuous treatment meets the application requirements most for flexible materials, such as rolled fabric and polymer film. Although there have been three related prior arts of U.S. patent publications for similar applications, including: (a) U.S. Pat. No. 5,456,972, “Method and apparatus for glow discharge plasma treatment of polymer materials at atmospheric pressure”, proclaimed by Roth et al., in 1995; (b) U.S. Pat. No. 5,529,631, “Apparatus for the continuous surface treatment of sheet material”, proclaimed by Yoshikawa et al., in 1996,; and (c) No. 20030116281A1, “Atmospheric pressure plasma system”, proclaimed by Yoshikawa et al., in 2003, there has been a serious drawback in the design of these three patents. Please refer to  FIG.6 , which is a schematic view of the device for the prior arts. As shown in the figure, the pair of electrodes for the generation of the atmospheric pressure plasmas is embedded in a large plasma-gas chamber  11 , so that in their apparatuses there are at least two plasma-gas flow channels  12  and  13 , where the channel  12  is the gas flow space between two dielectric barrier plates of electrodes; and the channel  13  is the one outside the two dielectric barrier plates of electrodes. In order to reduce the operating cost by lowering the working voltage and power consumption in the surface treatment of flexible materials, such as a fabric or a polymer film, a small gap (&lt;6 mm ) between the parallel dielectric barrier plates of electrodes has to be employed. Hence, the space between the dielectric barrier plates of electrodes has a much greater obstruction to the flow of plasma gas than that for the much wider space outside the dielectric barrier plates of electrodes. Thus, most of the plasma gas flows through the space outside the dielectric barrier plates and only very little amount of the gas passes through the narrow gap between dielectric barrier plates, resulting in a very low usage efficiency of the plasma gas. Owing to the expansive plasma gas used for the apparatus, its operating cost goes high, which obviously does not meet the requirements of industrial applications.  
         [0003]     Firstly, the space uniformity of the glow discharge plasmas is essential for a good quality surface treatment. For the prior three patents of the atmospheric glow discharge plasma apparatuses, most of the input plasma gas predominantly fills up the space outside the dielectric barrier plates and only after the space is filled with the plasma gas, the plasma gas there starts to diffuse gradually into the narrow space between the dielectric barrier plates and dilutes the air presented there previously. Because the diffusion speed of the plasma gas is very low under an atmosphere pressure, the density of the plasma gas around the rim of the electrodes is always higher than that at the center of the electrodes so that the distribution of the plasma gas between the electrodes is not uniform and the density of the glow discharge plasmas generated is not uniform either.  
         [0004]     Secondly, the conditions for the generation of a stable glow discharge plasma has been extensively investigated under atmospheric pressure According to the experiment done by N. Gherardi (published in the book by M. A. Lieberman etc., Principle of plasma discharges and material processing, John Willey &amp; Sons. Inc., 1994), a slow flow of plasma gases between electrodes facilitates to the generation of a stable glow discharge plasmas. In addition, an efficient flow of the plasma gas can also lower the temperature of the plasma gas in the gap between the electrodes, which is good not only to the stability of the glow discharge plasmas, but also to the treatment of polymer materials which are not able to resist high-temperature environments. Regarding the design of the prior arts, most of the input plasma gas is filled up in the space outside of the gap of the electrode at the beginning stage, and then it gradually diffuses into the gap and dilutes the air there. After a discharge, the consumed plasma gas between electrodes is re-supplied mostly by the diffusion of the plasma gas outside of the electrodes through the rim of the electrodes. Therefore, the density of the plasma gas near the rim of the electrodes is always higher than that at the center. In another word, during all plasma-gas input phases, only a very small amount of plasma gas input into the plasma chamber enters directly into the gap between the electrodes and most of its plasma gases there is supplied by the diffusion of the plasma gases through the rim of the electrodes from outside of the electrodes. This leads to a too low gas flow rate to meet the requirements for the generation of a stable glow discharge plasmas.  
         [0005]     In addition, in the device for the generation of glow discharge plasmas proclaimed in 2003 in the world patent publication No. WO003,086,031 A1, the design for an uniformly distributed gas inlet-and-outlet (I/O) device is still not included in spite of its much different design structure from the prior three patents. Hence, the plasma gas between the electrodes is not uniformly distributed and thus, the uniformity of the glow discharge plasma s generated from its apparatus is much in doubt.  
         [0006]     As the above descriptions, although there are several apparatuses and methods in the prior arts can be applied for a surface treatment of the flexible sheet materials by using atmospheric glow discharge plasmas, there are still two serious drawbacks required for good solution, including the un-uniformity of the glow plasma for treating a flexible material of large area and the high consumption of plasma gases. Hence, the prior arts have not been adopted widely by the industrial enterprises. While, the greatest advantage of the present invention is that it can solve these two drawbacks completely.  
       SUMMARY OF THE INVENTION  
       [0007]     The main purpose of the present invention is, by integrating an uniform gas inlet-and-outlet (I/O) devices and a single plasma-gas flow channel to attain a good quality of surface treatment by using an atmospheric pressure glow discharge plasma and to save a great amount of expansive plasma gases, in addition to attain continuous processing and high production.  
         [0008]     To achieve the above purpose, the present invention is an apparatus for a flexible sheet material surface treatment with a glow discharge plasma and a method thereof, where the apparatus comprises a pair of electrodes; a single plasma-gas flow channel consisting of a pair of dielectric barrier plates together with electrically insulated and air-sealed plates; a pair of uniform gas inlet-and-outlet devices with full gas tight seals; a pair of gas-seal devices for the horizontal movement of a flexible sheet material; and a pair of reel devices. Either a pulsed or a continuous AC (alternating current) power supply, is connected to the electrodes to effectively generate an uniform glow discharge plasma at the lowest input power for a surface treatment of the flexible sheet materials, comprising cleaning, disinfection serialization, activation, graft, polymerization, coarsens and coating. Accordingly, a novel apparatus for the uniform surface treatment of a flexible sheet material with an atmospheric pressure glow discharge plasma and a method there of are proposed.  
     
    
     BRIEF DESCRIPTIONS OF THE DRAWINGS  
       [0009]     The present invention will be better understood from the following detailed description of the preferred embodiment according to the present invention, taken in conjunction with the accompanying drawings, in which  
         [0010]      FIG. 1  is a schematic view showing an apparatus according to a preferred embodiment of the present invention;  
         [0011]      FIG. 2  is a schematic view showing a hermetic device for the horizontal movement of a flexible sheet material according to the preferred embodiment of the present invention;  
         [0012]      FIG. 3  is across-sectional side view showing an uniform gas entrance and exit device according to the preferred embodiment of the present invention;  
         [0013]      FIG. 4A  and  FIG. 4B  are a side view and a top view showing an assembly of electrodes and dielectric barrier plates according to the preferred embodiment of the present invention;  
         [0014]      FIG. 5  is a schematic view showing a cooling water device according to the preferred embodiment of the present invention; and  
         [0015]      FIG. 6  is a schematic of an apparatus of a prior art. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0016]     The following description of the preferred embodiment is provided to understand the features and the structures of the present invention.  
         [0017]     Please refer to  FIG. 1 , which is a schematic view showing an apparatus according to a preferred embodiment of the present invention. As shown in the figure, the present invention is an apparatus for a flexible sheet material surface treatment with glow discharge plasmas and a method thereof, where the apparatus  1  comprises a pair of electrodes  2 ; a pair of dielectric barrier plates  3 ; a pair of uniform gas entrance and exit devices  4 ; a pair of gas-seal devices  5  for the horizontal movement of a flexible material; and a pair of reel devices  6 , and where, by u sing positioning nuts  71  and positioning screws  72 , the apparatus  1  is fixed on a positioning plate  7 . The electrode  2  is fixed to electrode positioning rod  21  through screws  211  (as shown in  FIG. 5 ). The electrode positioning rod  21  is also used as a electrically conducting rod connected to a high-voltage power supply device  9  for obtaining the required high voltages. The high-voltage power supply device  9  provides either a pulsed or a continuous AC electric power with a voltage between 1 kV and 100 kV and a frequency between 1 kHz and 100 kHz. One of the electrode positioning rod  21  is connected to the high-voltage power supply device  9  through a high-voltage electrical wire  91 ; and another one of the electrode positioning rod  23  is grounded via a conducting wire  92 . The electrode  2  is a rectangular metal plate, capable of performing a large-area and uniform surface treatment of a flexible material a long a horizontal movement. The flexible material can be a fabric or a polymer film. The electrode  2  can be made of aluminum or copper, which can be fabricated easily and have a good thermal conductivity. The gap between the electrodes  2  can be adjusted by using the electrode positioning rod  21 , an electrode-gap adjusting base  22  and an electrode-gap ad justing nut  24 . The thickness of the dielectric barrier plate  3  is preferred to be not greater than 2 mm, which is made of an electrically insulated material, which can be a glass, a plastic or a ceramic. The gap between the electrodes  2  is between 2 mm and 20 mm, which is preferably about 2 mm thicker than the thickness of the treated sheet material to avoid too much obstruction to the plasma gas flow.  
         [0018]     A method for the apparatus  1  uses a glow plasma obtained within the apparatus  1  for a surface treatment of a flexible sheet material, where the method comprises a plasma treatment process for cleaning, disinfection, serialization, activation, graft, polymerization, coarsening and coating.  
         [0019]     Please refer to  FIG. 2 , which is a schematic showing a gas-seal device for a horizontal movement of a flexible material according to the preferred embodiment of the present invention. As shown in the figure, the gas-seal device  5  comprises the structure of dual sets of cylinders  51 . The gas-seal tightness of the gas-seal device  5  can be ad justed according to the material of the cylinder  5 , the air tightness between the cylinders  5  and the flexible sheet material treated, and the moving speed of the flexible material. A turning shaft  511 , made of metals or ceramics, is at the center of the cylinder  51  surrounded by a second rubber gasket  512 . The gas-seal device  5  is connected to an uniform gas inlet-and-outlet device  4  (not shown in the figure) with a third rubber gasket  52  to increase the gas-tight seal between the gas-seal device  5  and the uniform gas inlet-and-outlet device  4 . The rubber gaskets  512  and  52  are made of electrically insulated materials, which can be a soft plastic. Please further refer to  FIG. 1 . By that the air tightness of the gas-seal device  5  is further adjusted to obtain a better gas seal at the entrance  53  for the treating flexible materials than the gas-seal at the exit  54 . This also facilitates the flow of the plasma gases in the gap of electrodes along a single direction. Another side of the gas-seal device  5  is connected to a reel device  2  to attain continuous processing and high production.  
         [0020]     Please refer to  FIG. 3 , which is a cross-sectional side view showing an uniform gas inlet-and-outlet (I/O) device  4  according to a preferred embodiment of the present invention. As shown in the figure, the uniform gas I/O device  4  comprises a gas inlet-and-outlet (I/O) pipe  41  and a position-fixing base  44 . The gas inlet-and-outlet (I/O) pipe  41  comprises at least two gas inlet-and-outlet (I/O) holes  42 . The diameter of the gas I/O holes  42  is a directly proportional to the distance to the mouth of the gas I/O pipe  41 . That is to say, the farther the gas I/O hole  42  is located from the mouth of the gas I/O pipe  41 , the bigger the diameter of the gas I/O holes; on the contrary, the nearer the gas I/O hole  42  is located from the mouth of the gas I/O pipe  41 , the smaller the diameter of the gas I/O holes; So, the smaller hole  42  located nearer from the mouth of the uniform gas I/O pipe  41  suffers for a greater obstruction to gas flow, while the bigger hole  42  located farther away from the mouth of the uniform gas I/O pipe  41  suffers for a lower obstruction to gas flow. As a result, the gas flow rate of the plasma gas for each hole  42  into the single plasma-gas flow channel is approximately the same. The uniform gas I/O pipe  41  is fixed to the positioning base  44  with an O-ring seal and a set of positioning screws so that a full gas tight seal is obtained. The plasma gas can be helium, argon or a mixture of helium, or argon, oxygen, nitrogen, O 2 , air, NH 3 , CF 4 , C 3 F 6 , C 4 F 8 , and gaseous monomers in various proportion. Please further refer to  FIG. 1 , the plasma gas flow rate for each gas is controlled respectively at the inlet  46  and a mixture of plasma gases is guided through a flexible gas pipe  47  f or in put (output) to (out of) the uniform gas I/O pipe and the gap of electrodes, where an exhaust blower  48  or an air exhaust valve  49  can be used according to the activity of the plasma gas used for each application.  
         [0021]     Please refer to  FIG. 4A  and  FIG. 4B , which is respectively a side view and a top view showing an assembly of electrodes and dielectric barrier plates according to the preferred embodiment of the present invention. As shown in the figures, two electrodes  2  are ad he red to two dielectric barrier plates  3  with a thermally conductive and electrically insulating glue; and at the periphery of each dielectric barrier plate  3  is ad he red with a rectangular gas-seal insulated dam  31 . Each of the surfaces, where the dielectric barrier plate  3  is connected with an uniform gas I/O device  4  (not shown in the figures), comprises a first rubber gasket  32  to improve its air tightness. Each of the surfaces, where the dielectric barrier plate  3  is not connected with the uniform gas I/O device  4 , comprises a first rubber washer  32  and a gas-seal insulated plate  34  to obtain good air tightness; and further comprises an n-shaped gas-seal adjusting base  35  having a knob  351  for ad justing the tightness of the gas-seal insulated plate  34  for a better air-tightness.  
         [0022]     Please refer to  FIG. 5 , which is a schematic view showing a cooling water device according to the preferred embodiment of the present invention. As shown in the figure, a cooling water device  10  is set on an electrode  2 , comprising a cooling-water reservoirs  101 , a cooling-water inlet pipe  102 , a cooling-water outlet pipe  103 , a cooling-water sealing plate  104 , a pair of O-ring seals  105  and a plurality of positioning screws  106 . The cooling water device  10  provides a cooling water of room temperature to cool down the temperature of the plasma gas, and to prevent the undesirable change in the characteristics of plasma discharge due to water condensation on the dielectric barrier plates of electrodes.  
         [0023]     To sum up, the present inventions an apparatus for a flexible sheet material surface treatment with a glow plasma and a method thereof, where a surface treatment is done by an uniform glow discharge plasma so that a good quality of treatment is obtained and a great amount of plasma gas used is saved for continuous processing and high production.  
         [0024]     The preferred embodiment herein disclosed is not intended to unnecessarily limit the scope of the invention. Therefore, simple modifications or variations belonging to the equivalent of the scope of the claims and the instructions disclosed herein for a patent are all within the scope of the present invention.