Patent Publication Number: US-9902564-B1

Title: Roller assembly, step roller thereof, and method for transporting substrate using the same

Description:
TECHNICAL FIELD 
     The technical field relates to a roller assembly, step roller, and method for transporting a substrate using the same. 
     BACKGROUND 
     During roll to roll processing in roller assemblies, when substrates or films are transported from one roller to another roller, the substrates or films may have patterns that were formed on the substrates. In order to prevent the patterns from being damaged, the substrates or films are transported through a step roller so that the patterns do not contact the rollers directly. Since the patterns do not contact the rollers through the step roller, the substrates or films are transported without damaging the patterns on them. 
     However, conventional step rollers do not support the middle of the substrate or film they are transporting because the patterns are in the middle of the substrate. During transporting the substrate through the step roller, stress is generated from the bending moment towards the substrate. Because the substrate is not supported in the middle, stress generated from the bending moment may cause the substrate or film to be wrinkled or damaged. If the substrate is damaged, the substrate is not able to be properly transported. In addition, the pattern on the substrate may also be damaged. 
     SUMMARY 
     An exemplary embodiment of the disclosure provides a roller assembly for transporting a substrate. The roller assembly includes a step roller, a first transport roller, and a second transport roller. The step roller includes a main roller, an air cylinder, and a pair of edge rollers. The air cylinder is sleeved on the main roller, and includes a plurality of air jetting holes and a plurality of air suction holes. The edge rollers are disposed on the main roller and are located on opposite ends of the air cylinder. The first transport roller and the second transport roller are disposed on opposite sides of the step roller, wherein the substrate is transported from the first transport roller to the second transport roller through the step roller. 
     An exemplary embodiment of the disclosure provides a step roller adapted to transport a substrate. The step roller includes a main roller, an air cylinder, and a pair of edge rollers. The air cylinder is sleeved on the main roller, and includes a plurality of air jetting holes and a plurality of air suction holes. The edge rollers are disposed on the main roller and are located on opposite ends of the air cylinder. 
     An exemplary embodiment of the disclosure provides a step roller adapted to transport a substrate. The step roller includes a main roller and a pair of edge rollers. A plurality of air jetting holes and a plurality of air suction holes are arranged on the main roller. The edge rollers are disposed on the main roller and located on opposite ends of the main roller. The air jetting holes and the air suction holes are distributed between the pair of edge rollers. 
     An exemplary embodiment of the disclosure provides a step roller adapted to transport a substrate. The step roller includes a main roller and a pair of edge rollers. A plurality of air jetting holes and a plurality of air suction holes are arranged on the main roller. The air jetting holes or the air suction holes are disposed on an arc length of a circumference of the main roller, and an angle of the arc length is equal to or less than 180 degrees. The edge rollers are disposed on the main roller and located on opposite ends of the main roller. The air jetting holes and the air suction holes are distributed between the pair of edge rollers. 
     An exemplary embodiment of the disclosure provides a method for transporting a substrate with a roller assembly. The substrate is radially transported through a step roller. Air is jetted between the substrate and a main roller of the step roller from a plurality of air jetting holes of an air cylinder sleeved on the main roller. Air between the substrate and the main roller is suctioned into a plurality of air suction holes of the air cylinder sleeved on the main roller. The edges of the substrate are supported by a pair of edge rollers. 
     Several exemplary embodiments accompanied with figures are described in detail below to further describe the disclosure in details. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawings are included to provide further understanding, and are incorporated in and constitute a part of this specification. The drawings illustrate exemplary embodiments and, together with the description, serve to explain the principles of the disclosure. 
         FIG. 1  is a three-dimensional schematic diagram of a roller assembly according to an embodiment of the disclosure. 
         FIG. 2  is a schematic side view of the roller assembly of  FIG. 1 . 
         FIG. 3  is a schematic three-dimensional diagram of a step roller of  FIG. 1 . 
         FIG. 4  is a partial enlarged view of the schematic diagram illustrating the step roller in  FIG. 3 . 
         FIG. 5  is a schematic bottom view of the step roller of  FIG. 3 . 
         FIG. 6  is a schematic side view of an air cylinder of  FIG. 3 . 
         FIG. 7A  is a schematic front view of the step roller of  FIG. 3  according to an embodiment of the disclosure. 
         FIG. 7B  is a schematic front view of the step roller of  FIG. 3  according to another embodiment of the disclosure. 
         FIG. 8  is a schematic three-dimensional diagram of a step roller according to another embodiment of the disclosure. 
         FIG. 9  is a schematic three-dimensional diagram of a step roller according to yet another embodiment of the disclosure. 
         FIG. 10  is a partial enlarged view of the schematic diagram illustrating the step roller in  FIG. 9 . 
         FIG. 11  is a schematic three-dimensional diagram of a step roller according to yet another embodiment of the disclosure. 
         FIG. 12  is a schematic three-dimensional diagram of a step roller according to still another embodiment of the disclosure. 
         FIG. 13  is a flow chart of a method of transporting a substrate with a roller assembly according to an embodiment of the disclosure. 
         FIG. 14  is a schematic three-dimensional diagram of a step roller according to another embodiment of the disclosure. 
         FIG. 15  is a schematic three-dimensional diagram of a step roller according to yet another embodiment of the disclosure. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
       FIG. 1  is a three-dimensional schematic diagram of a roller assembly according to an embodiment of the disclosure.  FIG. 2  is a schematic side view of the roller assembly of  FIG. 1 . In the embodiment, the roller assembly  100  includes a first transport roller  110 , a second transport roller  120 , and a step roller  130 . The roller assembly  100  is suitable for roll to roll processing. The first transport roller  110  and the second transport roller  120  are disposed on opposite sides of the step roller  130 . A substrate  140  with patterns  142  is transported from the first transport roller  110  to the second transport roller  120  through the step roller  130 . In other embodiments, the substrate  140  that is transported does not have to include patterns  142 . The substrate  140  or web is, for example, any suitable material to be processed in roll to roll processing such as paper, glass, polyethylene terephthalate (PET), polyimide (PI), or Polyurethane (PU). The patterns  142  are any suitable patterns formed on the substrate  140  desired by the user. The material of the patterns  142  are, for example, semiconductor material, metal, organic material, or any other suitable material. The patterns  142  are, for example, printed or deposited on the substrate  140 . However, the disclosure is not limited thereto, and the patterns  142  may be fol ed on the substrate  140  through any other suitable method. In the embodiment, multiple patterns  142  are shown. However, the disclosure is not limited thereto, and the number of patterns  142  may be determined and adjusted according to user requirements. 
     In the embodiment, when the substrate  140  is transported from the first transport roller  110  to the second transport roller  120 , a side  140   a  with the patterns  142  faces away from the first transport roller  110  and the second transport roller  120 . That is to say, the side  140   a  with the patterns  142  does not contact the first transport roller  110  and the second transport roller  120  so that the patterns  142  are not damaged while the substrate  140  is rolling on the first transport roller  110  and the second transport roller  120 . In addition, the side  140   a  with the patterns  142  faces the step roller  130 . Specifically, as seen in  FIG. 1 , the step roller  130  includes a pair of edge rollers  132  and a main roller  134 . The edge rollers  132  are sleeved on the main roller  134 . When the substrate  140  is transported through the step roller  130 , the side  140   a  of the substrate  140  with the patterns  142  is in contact with the edge rollers  132 . Since the edge rollers  132  support the two sides of the substrate  140 , the patterns  142  do not contact the edge rollers  132  or the main roller  134 . This way, the patterns  142  are not damaged when the substrate  140  is transported through the step roller  130 . As the substrate  140  is transported through the step roller  130 , the edge rollers  132  and the main roller  134  rotate together. The edge rollers  132  are fixed to the main roller  134  through, for example, welding, adhering, fastening, or any other suitable method such that the edge rollers  132  rotate with the main roller  134 . In other embodiments, the edge rollers  132  and the main roller  134  is integrally formed. 
       FIG. 3  is a schematic three-dimensional diagram of a step roller of  FIG. 1 .  FIG. 4  is a partial enlarged view of the schematic diagram illustrating the step roller in  FIG. 3 . As seen in  FIG. 3  and  FIG. 4 , in the embodiment, the step roller  130  includes the pair of edge rollers  132 , the main roller  134 , and an air cylinder  136 . The air cylinder  136  is sleeved on the main roller  134 , and the edge rollers  132  are located on opposite ends of the air cylinder  136 . The air cylinder  136  includes a plurality of air jetting holes  136   a  and a plurality of air suction holes  136   b . In addition, the air cylinder  136  is located around the middle of the main roller  134 , and a length of the air cylinder  136  is less than a distance between the pair of edge rollers  132 . That is to say, the air cylinder  136  does not cover the entire distance between the pair of edge rollers  132 . 
     In the embodiment, air is adapted to be jetted out of the air jetting holes  136   a , and air is adapted to be suctioned into the air suction holes  136   b . Referring to  FIG. 4 , it can be seen that the air jetting holes  136   a  and the air suction holes  136   b  are respectively aligned in the alternating rows, wherein the rows are in a circumferential direction of the air cylinder  136 . That is to say, the air suction holes  136   b  and the air jetting holes  136   a  are not in the same row in a circumferential direction of the air cylinder  136 . In the length direction (y-direction) of the air cylinder  136 , the air jetting holes  136   a  and the air suction holes  136   b  are alternately aligned. The air jetting holes  136   a  and the air suction holes  136   b  face the substrate  140  as the substrate  140  is being transported through the step roller  130 . Therefore, the air jetted out by the air jetting holes  136   a  are able to provide the substrate  140  with an additional support point near the middle, since the air cylinder  136  is near the middle of the main roller  134 . That is to say, the air jetted from the air jetting holes  136   a  push the substrate  140  in the opposite direction of the bending moment (bending moment direction shown as BM in  FIGS. 1, 2 , and  3 ) on the substrate  140 . Thus, this relieves the stress towards the substrate  140  while the substrate  140  is transported through the step roller  130 , and may prevent the substrate  140  from being wrinkled or damaged. 
       FIG. 5  is a schematic bottom view of the step roller of  FIG. 3 . As seen in  FIG. 3  and  FIG. 5 , a support frame  150  is further connected to the step roller  130  to support the air cylinder  136 . The support frame  150  is connected to both ends of an axis support  134   a  of the main roller  134 , and extends along the length direction of the main roller  134 . The axis support  134   a  does not rotate with the edge rollers  132  and the main roller  134 . Therefore, the support frame  150  does not rotate, and is fixed so as to support the air cylinder  136 . Since the air cylinder  136  is supported and fixed on the support frame  150 , the air cylinder  136  is not fixed to the main roller  134 , and does not rotate with the main roller  134 . That is to say, the air cylinder  136  is spaced apart from the main roller  134  and does not rotate with the main roller  134 . This way, the air jetting holes  136   a  and the air suction holes  136   b  do not move and face the same direction towards the substrate  140  while the substrate  140  is being transported through the step roller  130 . However, the disclosure is not limited thereto. In other embodiments, the support frame  150  is connected to any fixed portion of the roller assembly  100 . That is to say, the support frame  150  may be connected to either the step roller  130 , the first transport roller  110 , the second transport roller  120 , or any other component in the roller assembly  100  that is suitable to be connected to the support frame  150  such that the support frame  150  is fixed. 
     Further referring to  FIG. 5 , in the embodiment, the support frame  150  has a connecting portion  152 . The connecting portion  152  is adapted to be connected to an air supplier  170  (shown in  FIG. 7A  and  FIG. 7B ) and a vacuum system  160  (shown in  FIG. 7A  and  FIG. 7B ). The air supplier  170  and the vacuum system  160  are any suitable machine or system required by the user known to one of ordinary skill in the art. That is, the air supplier  170  provides air (jets air), and the vacuum system  160  suctions air. Specifically, the connecting portion  152  includes a plurality of supplying holes  152   a  ( 152   a   1 ,  152   a   2 ,  152   a   3 ) and a plurality of vacuum holes  152   b  ( 152   b   1 ,  152   b   2 ,  152   b   3 ,  152   b   4 ). In the embodiment, three supplying holes  152   a  are shown and four vacuum holes  152   b  are shown. However, the number of supplying holes  152   a  and vacuum holes  152   b  may be adjusted as required by the user. The supplying holes  152   a  are connected to the air supplier  170  through any suitable method. For example, the supplying holes  152   a  are connected to the air supplier through valves, tubes, pipes, or a combination of the above. Similarly, the vacuum holes  152   b  are connected to the vacuum system  160  through valves, tubes, pipes, or a combination of the above. The supplying holes  152   a  are connected to the air jetting holes  136   a  such that the air from the air supplier  170  enters the supplying holes  152   a  and exits from the air jetting holes  136   a . Furthermore the vacuum holes  152   b  are connected to the air suction holes  136   b  such that air is suctioned in from the air suction holes  136   b  and enters the vacuum system  160  through the vacuum holes  152   b.    
     In the embodiment, the pressure and rate of air jetted from the air jetting holes  136   a  is controlled by air supplier  170  in conjunction with the vacuum system  160 . The rate of air suctioned into the air suction holes  136   b  is controlled by the vacuum system  160  in conjunction with the air supplier  170 . That is to say, the air supplier  170  and the vacuum system  160  are controlled such that the air jetted out of the air jetting holes  136   a  is enough to support the substrate  140  from wrinkling due to the stress from the bending moment. In addition, the pressure from the air jetted out of the air jetting holes  136   a  is controlled so that the air does not damage the patterns  142  on the substrate  140 . In the embodiment, the rate of air suctioned by the air suction holes  136   b  is controlled so that the rate is enough to support substrate  140  but not lose stability of the substrate  140  being transported. Specifically, the substrate  140  is in contact with the edge rollers  132  and while being transported covers about half of the step roller  130 . The space between the edge rollers  132  is covered by the substrate  140 . Thus, if the air is continuously jetted out of the air jetting holes  136   a , the air has no clear exit, and the substrate  140  will float and in some cases, lose stability. By losing stability, the substrate  140  may undesirably change position or be harder to control during transportation. Therefore, while the air is jetted out of the air jetting holes  136   a , the air suction holes  136   b  suctions in the air. Thus, the air has a place to exit, and the system has better stability. By controlling the rate the air is supplied and suctioned out, the substrate  140  is both supported and transportation of the substrate  140  through the step roller is stable. 
       FIG. 6  is a schematic side view of an air cylinder of  FIG. 3 . Referring to  FIG. 6 ,  FIG. 6  shows an arc length  138  of the air cylinder  136 , and an angle  138   a  of the arc length  138  of the air cylinder  136 . Specifically, the air jetting holes  136   a  and the air suction holes  136   b  are disposed on the arc length  138  of the circumference of the air cylinder  136 . In the embodiment, the angle  138   a  of the arc length  138  is substantially equal to or less than 180 degrees. Specifically, the angle  138   a  of the arc length  138  is, for example, 160 degrees. However, the disclosure is not limited thereto, and the angle  138   a  of the arc length  138  may be adjusted as required by the user. 
       FIG. 7A  is a schematic front view of the step roller of  FIG. 3  according to an embodiment of the disclosure. As seen in  FIG. 7A , a maximum height H 1  from the air cylinder  136  to the main roller  134  is less than a maximum height H 2  of the edge rollers  132  to the main roller  134 . That is to say, the edge rollers  132  are higher than the air cylinder  136 . This way, as the substrate  140  is being transported through the step roller  130 , the edge rollers  132  support the substrate  140 . Since the edge rollers  132  are higher than the air cylinder  136 , the substrate  140  does not come in contact with the air cylinder  136 . That is to say, there is a gap between the air cylinder  136  and the substrate  140  while the substrate  140  is transported through the step roller  130 . Because the substrate  140  does not come in contact with the air cylinder  136 , the patterns  142  on the substrate  140  do not contact the air cylinder  136 . This prevents the patterns  142  on the substrate  140  from being damaged while the substrate  140  is transported through the step roller  130 . 
     Furthermore, as seen in  FIG. 7A , according to the embodiment, the supplying holes  152   a   1 ,  152   a   2 ,  152   a   3  are connected to the air supplier  170 . Specifically, the supplying holes  152   a   1 ,  152   a   3  are connected to the same tube connected to the air supplier  170  such that the supplying holes  152   a   1 ,  152   a   3  supply air at the same rate. Thus, the rows of air jetting holes  136   a  respectively connected to the supplying holes  152   a   1 ,  152   a   3  jet air at the same rate. The supplying hole  152   a   2  is connected to the air supplier  170  through a different tube separate from the supplying holes  152   a   1 ,  152   a   3 . Thus, the rate of air supplied to the supplying hole  152   a   2  is independent from the rate of air supplied to the supplying holes  152   a   1 ,  152   a   3 . Thus, the row of air jetting holes  136   a  connected to the supplying hole  152   a   2  jets air at a rate that is independent from the rate of air jetted from the row of air jetting holes  136   a  connected to the supplying holes  152   a   1 ,  152   a   3 . Even though the supplying hole  152   a   2  is independently connected to the air supplier  170  from the supplying holes  152   a   1 ,  152   a   3 , the rate of air supplied to the supplying hole  152   a   2  may be the same or different from the rate of air supplied to the supplying holes  152   a   1 ,  152   a   3 . 
     In addition, according to the embodiment, the vacuum holes  152   b   1 ,  152   b   2 ,  152   b   3 ,  152   b   4  are connected to the vacuum system  160 . Specifically, the vacuum holes  152   b   1 ,  152   b   4  are connected to the same tube connected to the vacuum system  160  such that the vacuum holes  152   b   1 ,  152   b   4  suction air at the same rate. Thus, the rows of air suctioning holes  136   b  respectively connected to the vacuum holes  152   b   1 ,  152   b   4  suction air at the same rate. The vacuum holes  152   b   2 ,  152   b   3  are connected to the same tube connected to the vacuum system  160  such that the vacuum holes  152   b   2 ,  152   b   3  suction air at the same rate. Thus, the rows of air suctioning holes  136   b  respectively connected to the vacuum holes  152   b   2 ,  152   b   3  suction air at the same rate. The tube connecting the vacuum holes  152   b   2 ,  152   b   3  to the vacuum system are independent from the tube connecting the vacuum holes  152   b   1 ,  152   b   4 . Thus, the rate of air suctioned by the vacuum holes  152   b   1 ,  152   b   4  is independent from the rate of air suctioned by the vacuum holes  152   b   2 ,  152   b   3 . Even though the vacuum holes  152   b   2 ,  152   b   3  are independently connected to the vacuum system  160  from the vacuum holes  152   b   1 ,  152   b   4 , the rate of air vacuumed by the vacuum holes  152   b   2 ,  152   b   3  may be the same or different from the rate of air vacuumed by the vacuum holes  152   b   1 ,  152   b   4 . 
       FIG. 7B  is a schematic front view of the step roller of  FIG. 3  according to another embodiment of the disclosure.  FIG. 7B  is similar to  FIG. 7A , and the same descriptions will not be repeated herein. The difference is in the embodiment of  FIG. 7B , the vacuum holes  152   b   1 ,  152   b   2 ,  152   b   3 ,  152   b   4  are connected to the vacuum system  160  through the same tube, such that the vacuum holes  152   b   1 ,  152   b   2 ,  152   b   3 ,  152   b   4  suction air at the same rate. In addition, the supplying holes  152   a   1 ,  152   a   2 ,  152   a   3  are connected to the air supplier  170  through the same tube, such that the supplying holes  152   a   1 ,  152   a   2 ,  152   a   3  supply air at the same rate. However, the disclosure is not limited to the connections shown in  FIG. 7A  and  FIG. 7B . The vacuum holes  152   b  and the supplying holes  152   a  may be connected to the air supplier  170  and the vacuum system  160  through any suitable connection. 
       FIG. 8  is a schematic three-dimensional diagram of a step roller according to another embodiment of the disclosure. Referring to  FIG. 8 , the embodiment of  FIG. 8  is similar to the embodiment of  FIG. 3 . Similar elements will use the same reference numerals, and the same description will not be repeated herein. In addition, the step roller  230  of  FIG. 8  is suitable to be in the roller assembly  100  of  FIG. 1 . The difference in the embodiment of  FIG. 8  is that the step roller  230  of  FIG. 8  includes a plurality of air cylinders  136 . The air cylinders  136  are disposed across the entire length between the edge rollers  132 . That is to say, the substrate  140  is further supported across the entire length between the edge rollers  132 . In the embodiment, five air cylinders  136  are disposed between the edge rollers  132 . However, the disclosure is not limited thereto. Depending on the length of the main roller  134  and the distance between the edge rollers  132 , the number of air cylinders  136  disposed between the edge rollers  132  may be adjusted. In some other embodiments, the air cylinders  136  are not disposed across the entire length between the edge rollers  132 , but only cover a partial length between the edge rollers  132 . The disclosure is not limited thereto. In the embodiment of  FIG. 8 , the number of connecting portions  152  (not shown) of the support frame  150  corresponds to the number of air cylinders  136 . 
       FIG. 9  is a schematic three-dimensional diagram of a step roller according to yet another embodiment of the disclosure.  FIG. 10  is a partial enlarged view of the schematic diagram illustrating the step roller in  FIG. 9 . Referring to  FIG. 9  and  FIG. 10 , the embodiment of  FIG. 9  and  FIG. 10  is similar to the embodiment of  FIG. 3 . Similar elements will use the same reference numerals, and the same description will not be repeated herein. In addition, the step roller  330  of  FIG. 9  is suitable to be in the roller assembly  100  of  FIG. 1 . The difference in the embodiment of  FIG. 9  is that the step roller  330  of  FIG. 9  includes an air cylinder  336 . A length of the air cylinder  336  is substantially the same as a distance between the pair of edge rollers  132 . In the embodiment, the air cylinder  336  is fixed to the main roller  134  such that the air cylinder  336  rotates with the main roller  134  and the edge rollers  132 . That is to say, the air cylinder  336  is in contact with the main roller  134  and rotates with the main roller  134 . The air cylinder  336  is fixed and connected to the main roller  134  through, for example, welding, adhering, fastening, or any other suitable method. The disclosure is not limited thereto. 
     Furthermore, as seen in  FIG. 9  and  FIG. 10 , the air jetting holes  336   a  and the air suction holes  336   b  are arranged in rows along the circumferential direction of the air cylinder  336 . In each row, the air jetting holes  336   a  and the air suction holes  336   b  are alternately arranged. Furthermore, the air jetting holes  336   a  and the air suction holes  336   b  are disposed along and surrounding the entire circumference of the air cylinder  336 . That is to say, the air jetting holes  336   a  and the air suction holes  336   b  surround the air cylinder  336  completely. When the air cylinder  336  rotates, only the air jetting holes  336   a  facing the substrate  140  jet air, and only the air suction holes  336   b  facing the substrate  140  suction air. The air jetting holes  336   a  and the air suction holes  336   b  are connected to an air supplier (not shown) and a vacuum system (not shown) through any suitable method. That is to say, the air supplier and the vacuum system are controlled such that only the air suction holes  336   b  facing the substrate  140  suction air and only the air jetting holes  336   a  facing the substrate  140  jet air, and the air supplier and the vacuum system are controlled manually or through any suitable method to one of ordinary skill in the art. In other embodiments, the air jetting holes  336   a  and the air suction holes  336   b  are disposed along an arc length of the circumference of the air cylinder  336 , similar to the arc length  138  in the embodiment of  FIG. 6 . In this case, the air cylinder  336  still rotates with the main roller  134 , and the air jetting holes  336   a  and the air suction holes  336   b  are only able to jet air and suction air towards the substrate  140  when rotated to face the substrate  140 . In some embodiments, the size of the air jetting holes  336   a  may be substantially equal to, greater than or smaller than that of the air suction holes  336   b . The size of the air jetting holes  336   a  and the air suction holes  336   b  is not limited in this disclosure. 
     In the embodiments of  FIG. 3  and  FIG. 8 , the step rollers can alternatively be connected the same way without the support frame  150 , such that the air cylinder  136  or air cylinders  136  are fixed to rotate with the main roller  134 . Furthermore, alternatively in  FIG. 3  and  FIG. 8 , the air jetting holes and the air suction holes may also be disposed along entire circumference. In other embodiments, while the substrate is transported through the step roller, the main roller and the air cylinder are fixed, and the edge rollers rotate. That is to say, the edge rollers are independently connected to separate rotating devices (not shown) such that the edge rollers rotate to transport the substrate. The separate rotating devices are any rotating axle, wheel, connector, or component that can drive the edge rollers to rotate according to one of ordinary skill in the art. Since only the edge rollers rotate, the main roller and the air cylinder do not rotate. Thus, the air cylinder can be connected to an air supplier and vacuum system through the main roller so as to control the air jetting holes and the air suction holes. However, the disclosure is not limited thereto, and the configuration of how to connect to the air supplier or the vacuum system may be adjusted as required by the user. 
     In the above embodiments, as the substrate  140  is transported along the step roller  130 ,  230 ,  330 , the stress affecting the substrate  140  due to the bending moment is the strongest at the substrate  140  corresponding to the top of the air cylinder  136 ,  336 . That is to say, the top of the air cylinder  136 ,  336  is the portion closest to the substrate  140 . The pressure of the air jetted from the air cylinder  136 ,  336 , to offset the bending moment is ideally the greatest at the top of the air cylinder  136 ,  336 . However, the disclosure is not limited thereto, and how the pressure of air jetted from the air cylinder  136 ,  336  is distributed may be adjusted according to user requirements. Depending on how and where the air supplier and vacuum system are connected to the air cylinder  136 ,  336 , the pressure at the top of the air cylinder  136 ,  336  is not necessarily the greatest. 
       FIG. 11  is a schematic three-dimensional diagram of a step roller according to yet another embodiment of the disclosure. Referring to  FIG. 11 , the embodiment of  FIG. 11  is similar to the embodiment of  FIG. 3 . Similar elements will use the same reference numerals, and the same description will not be repeated herein. In addition, the step roller  430  of  FIG. 11  is suitable to be in the roller assembly  100  of  FIG. 1 . The difference in the embodiment of  FIG. 11  is that the step roller  430  does not include an air cylinder. The step roller  430  includes the main roller  234  and the edge rollers  132 . The main roller  234  of  FIG. 11  includes a plurality of air jetting holes  234   a  and a plurality of air suctioning holes  234   b . Referring to  FIG. 11 , it can be seen that the air jetting holes  234   a  and the air suction holes  234   b  are respectively aligned in the alternating rows, wherein the rows are in a circumferential direction of the main roller  234 . The arrangement is similar to the air jetting holes  136   a  and the air suction holes  136   b  of  FIG. 4 . In the embodiment of  FIG. 11 , the air jetting holes  234   a  and the air suction holes  234   b  are disposed near the middle of the main roller  234 , and only partially cover the main roller  234  in the length direction. In some other embodiments, the air jetting holes  234   a  and the air suction holes  234   b  are disposed across the entire length between the edge rollers  132 . The disclosure is not limited thereto. 
     In  FIG. 11 , the air jetting holes  234   a  and the air suction holes  234   b  are disposed along an arc length of the circumference of the main roller  234 , similar to the arc length  138  in the embodiment of  FIG. 6 . While the substrate is transported through the step roller  430 , the main roller  234  is fixed, and the edge rollers  132  rotate. That is to say, the edge rollers  132  are independently connected to separate rotating devices (not shown) such that the edge rollers  132  rotate to transport the substrate. The separate rotating devices are any rotating axle, wheel, connector, or component that can drive the edge rollers  132  to rotate according to one of ordinary skill in the art. Since only the edge rollers  132  rotate, the main roller  234  does not rotate. Thus, an air supplier and vacuum system is connected to the air jetting holes  234   a  and the air suctioning holes  234   b  through the main roller  234  to be controlled. 
       FIG. 12  is a schematic three-dimensional diagram of a step roller according to still another embodiment of the disclosure. Referring to  FIG. 11  and  FIG. 12 , the step roller  430   a  illustrated in  FIG. 12  is similar with the step roller  430  illustrated in  FIG. 11  except that the main roller  234  of the step roller  430   a  shown in  FIG. 12  includes a plurality of air jetting holes  234   a  and a plurality of air suction holes  234   b  arranged thereon, the air jetting holes  234   a  and the air suction holes  234   b  are locally distributed on the circumference of the main roller  234 . For example, the air jetting holes  234   a  and the air suction holes  234   b  are disposed on the arc length AL of the circumference of the main roller  234 , and the angle of the arc length AL is substantially equal to or less than 180 degrees. In addition, the air jetting holes  234   a  and the air suction holes  234   b  are disposed across substantially the entire distance between the edge rollers  132 . 
     In some alternative embodiments, the main roller  234  of the step roller  430   a  may merely include a plurality of air jetting holes  234   a  or a plurality of air suction holes  234   b  arranged thereon. The air jetting holes  234   a  or the air suction holes  234   b  are disposed on the arc length AL of the circumference of the main roller  234 . For instance, the angle of the arc length AL is substantially equal to or less than 180 degrees. 
       FIG. 13  is a flow chart of a method of transporting a substrate with a roller assembly according to an embodiment of the disclosure. In step S 102 , a substrate  140  is radially transported through a step roller  130 . Specifically, the substrate  140  is radially transported from a first transport roller  110  to a second transport roller  120  through the step roller  130 . In step S 104 , air is jetted between the substrate  140  and a main roller  134  of the step roller  130  from a plurality of air jetting holes  136   a  of an air cylinder  136  sleeved on the main roller  134 . In step S 106 , air between the substrate  140  and the main roller  134  is suctioned into a plurality of air suction holes  136   b  of the air cylinder  136  sleeved on the main roller  134 . In step S 108 , the edges of the substrate  140  are supported by a pair of edge rollers  132 . During the method of transporting the substrate  140  through the step roller  130 , the edge rollers  132  and the main roller  134  rotate while the substrate  140  is being transported. The air cylinder  136  is fixed and the main roller  134  rotates while the substrate  140  is being transported. That is to say, the main roller  134  rotates with the edge rollers  132  while the substrate is being transported. Furthermore, the steps S 102 , S 104 , S 106 , and S 108  may all be performed at the same time during the transportation of the substrate  140  through the step roller  130 . In other embodiments, as described above, the air cylinder and the main roller are fixed while the substrate is being transported, and only the edge rollers rotate. Furthermore, in other embodiments, the air cylinder rotates with the main roller while the substrate is being transported. That is to say, similar to the embodiment of  FIG. 9 , when the air cylinder rotates, only the air jetting holes facing the substrate jet air, and only the air suction holes facing the substrate suction air. 
       FIG. 14  is a schematic three-dimensional diagram of a step roller according to another embodiment of the disclosure. Referring to  FIG. 3  and  FIG. 14 , the step roller  130   a  illustrated in  FIG. 14  is similar with the step roller  130  illustrated in  FIG. 3  except that the step roller  130   a  further include at least one support roller  137 . The at least one support roller  137  is fixed to the main roller  134  through, for example, welding, adhering, fastening, or any other suitable method such that the at least one support roller  137  rotates with the main roller  134 . 
     The substrate  140  (shown in  FIG. 1 ) is in contact with the at least one support roller  137  and while being transported covers about half of the step roller  130   a . The patterns  142  on the substrate  140  (shown in  FIG. 1 ) do not contact the at least one support roller  137 . In some embodiments, two support rollers  137  are disposed on the main roller  134  and each of the support rollers  137  may be arranged between the air jetting holes  234   a  (or the air suction holes  234   b ) and one of the edge rollers  132 , respectively. 
       FIG. 15  is a schematic three-dimensional diagram of a step roller according to yet another embodiment of the disclosure. Referring to  FIG. 11  and  FIG. 15 , the step roller  430   b  illustrated in  FIG. 15  is similar with the step roller  430  illustrated in  FIG. 11  except that the step roller  430   b  further include at least one support roller  137 . The at least one support roller  137  is fixed to the main roller  134  through, for example, welding, adhering, fastening, or any other suitable method such that the at least one support roller  137  rotates with the main roller  234 . Furthermore, the substrate  140  (shown in  FIG. 1 ) is in contact with the at least one support roller  137  and while being transported covers about half of the step roller  430   b . The patterns  142  on the substrate  140  (shown in  FIG. 1 ) do not contact the at least one support roller  137 . In some embodiments, two support rollers  137  are disposed on the main roller  234  and each of the support rollers  137  may be arranged between the air jetting holes  234   a  (or the air suction holes  234   b ) and one of the edge rollers  132 , respectively. 
     It will be apparent to those skilled in the art that various modifications and variations can be made to the structure of the disclosed embodiments without departing from the scope or spirit of the disclosure. In view of the foregoing, it is intended that the disclosure cover modifications and variations of this disclosure provided they fall within the scope of the following claims and their equivalents.