Patent Publication Number: US-2011053461-A1

Title: Polishing apparatus and polishing method

Description:
TECHNICAL FIELD 
     The present invention relates to a polishing apparatus and a polishing method for polishing both surfaces of a plate material such as a glass plate. In particular, the present invention relates to measures to simultaneously polish both surfaces of such a plate material while transferring the same. 
     BACKGROUND ART 
     Generally, manufacture of a prescribed product using a plate material such as a glass plate includes polishing of the surfaces of the plate material. 
     Known polishing apparatuses used in such a process are, for example, the one disclosed in PATENT DOCUMENT 1, with which a plate material is polished on a one surface-by-one surface basis while the plate material is transferred, and, for example, the one disclosed in PATENT DOCUMENT 2, with which both surfaces of a plate material are polished simultaneously while the plate material is held. 
     CITATION LIST 
     Patent Document 
     PATENT DOCUMENT 1: Japanese Patent Publication No. 2002-066886 (page 4, FIG. 3) 
     PATENT DOCUMENT 2: Japanese Patent Publication No. 2001-334459 (page 5, FIGS. 1 and 2) 
     SUMMARY OF THE INVENTION 
     Technical Problem 
     However, in the conventional techniques described above, both the surfaces of a plate material cannot simultaneously be polished while being transferred, and accordingly they pose a problem of difficulty in shortening the takt time. 
     The present invention has been made in consideration of the foregoing, and its principle object is to make it possible, in polishing both surfaces of a plate material such as a glass plate, to simultaneously polish both the surfaces of the plate material while transferring the plate material, so as to contribute toward shortening the takt time. 
     Solution to the Problem 
     In order to achieve the above-described object, in the present invention, a plate material is sandwiched by two polishing heads, and in this state, the two polishing heads are vibrated in a direction crossing a transfer direction of the plate material. 
     Specifically, a polishing apparatus in accordance with the present invention includes: a transfer mechanism configured to transfer a plate material in a prescribed transfer direction; two polishing heads respectively having polishing surfaces configured to polish corresponding surfaces of the plate material, the two polishing heads being disposed so as to cause the polishing surfaces contact the corresponding surfaces of the plate material so as to sandwich the plate material in a plate-thickness direction therebetween, the two polishing heads being capable of being displaced along the corresponding surfaces and in a displace direction being a direction crossing the transfer direction of the transfer mechanism while allowing for the transfer of the plate material by the transfer mechanism; and a vibration mechanism configured to vibrate the two polishing heads such that the polishing heads are repeatedly displaced in the displace direction. 
     In a polishing method for polishing both surfaces of a plate material, two polishing heads respectively polishing both the surfaces of the plate material are used, and while the plate material is transferred in a prescribed transfer direction, the two polishing heads are vibrated so as to be repeatedly displaced relative to both the surfaces of the plate material along the corresponding surfaces of the plate material and in a displace direction being a direction crossing the transfer direction. In this way, both the surfaces of the plate material are simultaneously polished while the plate material is transferred. 
     It is noted that, in the above-described configuration, as to the polishing heads, the dimension of each of the polishing surfaces of the polishing heads in the displace direction of the polishing heads may be greater than that of the plate material in the displace direction. Further, the displace direction may be a direction approximately perpendicular to the transfer direction (a direction substantially perpendicular to the transfer direction). 
     Further, the vibration mechanism may be configured to vibrate the two polishing heads such that the two polishing heads are reversely displaced relative to each other. 
     In addition to the above-described configuration, liquid supply means for supplying liquid (such as water) on the corresponding surfaces of the plate material while being polished by the polishing heads may be included. Here, when the polishing heads each have a plurality of polishing blocks forming each of the polishing surfaces of the polishing heads, the liquid supply means may have a plurality of discharge nozzles disposed among the polishing blocks to discharge the liquid. 
     Specific use of the polishing apparatus in accordance with the present invention may include, for example, in a manufacturing process of a liquid crystal display panel, polishing a glass plate used as a base of an electrode substrate such as a TFT array substrate, a counter electrode substrate and the like, polishing such a liquid crystal display panel itself before a polarizer is bonded thereto, and polishing a liquid crystal display panel of a type to which such a polarizer is not bonded. 
     ADVANTAGES OF THE INVENTION 
     In accordance with the present invention, the plate material while being transferred is sandwiched by the two polishing heads, which two polishing heads are vibrated so as to be repeatedly displaced along the corresponding surfaces of the plate material and in a displace direction being a direction crossing the transfer direction of the plate material, whereby both the surfaces of the plate material can be polished while the plate material is transferred. Hence, the present invention can contribute toward shortening the takt time of the polishing step itself, and eventually that of the entire manufacturing process of a product using such a plate material. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view showing the overall structure of a polishing apparatus in accordance with an embodiment of the present invention. 
         FIG. 2  is a side view showing a state in which a glass plate is polished while being transferred. 
         FIG. 3  is a front view showing a state where the glass plate is polished while a top side polishing head and a bottom side polishing head are vibrated such that they are reversely displaced relative to each other while being supplied with water. 
         FIG. 4  is a cross-sectional view showing a state of water supply to the glass plate and the polishing blocks in an enlarged manner 
         FIG. 5  is a cross-sectional view taken along line V-V in  FIG. 3 . 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     In the following, an embodiment of the present invention will be described, referring to the drawings. 
       FIG. 1  is a perspective view schematically showing the overall structure of a polishing apparatus in accordance with the embodiment of the present invention. The polishing apparatus is used, in the manufacturing process of a product that is manufactured using a glass plate w as one of its materials, for polishing both the surfaces of the glass plate w. 
     The polishing apparatus includes: a transfer mechanism  10  configured to transfer a carried-in glass plate w; two polishing heads  20  and  30  having polishing surfaces configured to polish corresponding surfaces of the glass plate w, the two polishing heads  20  and  30  being disposed so as to cause the polishing surfaces contact the corresponding surfaces of the glass plate w so as to sandwich the glass plate w in the plate-thickness direction therebetween while allowing for the transfer of the glass plate w being transferred by the transfer mechanism  10 ; and a vibration mechanism  40  configured to vibrate the two polishing heads  20  and  30  respectively along the corresponding surfaces of the glass plate w and in a direction crossing a transfer direction T in which the glass plate w is transferred by the transfer mechanism  10 . 
     Because the glass plate w is carried in a horizontal state in the present embodiment, the transfer mechanism  10  is configured to transfer the glass plate w keeping it in the horizontal state. Specifically, a plurality of transfer rollers  11  whose respective shaft centers extend in the horizontal direction are disposed so as to be juxtaposed to one another in the prescribed transfer direction T. Here, as can also be seen in  FIG. 2  being a side view, the interval between a plurality of transfer rollers  11  located on the upstream side of the transfer direction T (left side in the drawing) and a plurality of transfer rollers  11  located on the downstream side of the transfer direction T (right side in the drawing) is set to be wider than the interval between any individual transfer rollers  11  adjacent to each other in the transfer direction T in other locations. Note that the interval between the upstream side and the downstream side is set to be narrower than the dimension of the glass plate w in the transfer direction T. The transfer rollers  11  are drivably coupled to a not-shown driver unit such that they rotate in the same direction at the same circumferential velocity. It is noted that the lengthwise dimension of the transfer rollers  11  is set to be greater than the dimension of the glass plate w in a direction perpendicular to the transfer direction T (hereinafter referred to as the transfer path widthwise direction). 
     The two polishing heads  20  and  30  are disposed so as to overlap one above the other between the transfer rollers  11  on the upstream side of the transfer direction T and the transfer rollers  11  on the downstream side of the transfer direction T. The polishing heads  20  and  30  are guided and supported by a not-shown guide support mechanism so as to be capable of being displaced in the transfer path widthwise direction. On the bottom surface side of the top side polishing head  20 , a plurality of (eleven in the exemplarily shown case) substantially columnar polishing blocks  21  each containing abrasive grains are mounted in a staggered manner. Specifically, the polishing blocks  21  are disposed so as to form two lines extending in the transfer path widthwise direction, in which the two lines are juxtaposed to each other in the transfer direction T. The number of the polishing blocks  21  forming the line on the downstream side of the transfer direction T is one plus the number of the polishing blocks  21  (five in the exemplarily shown case) on the upstream side of the transfer direction T (which provides six in the exemplarily shown case). Further, the gap dimension between the two polishing blocks  21  adjacent to each other in the transfer path widthwise direction is set to be smaller than that of each polishing block  21  in the transfer path widthwise direction. The polishing blocks  21  are disposed such that their respective bottom end surfaces are located on an identical plane. These bottom end surfaces form the polishing surface of the polishing head  20 . 
     On the other hand, on the top surface side of the bottom side polishing head  30  also, similarly to the top side polishing head  20 , a plurality of (eleven in the exemplarily shown case) substantially columnar polishing blocks  31  each containing abrasive grains are mounted in a staggered manner. Also, the gap dimension between the two polishing blocks  31  adjacent to each other in the transfer path widthwise direction is set to be smaller than that of each polishing block  31  in the transfer path widthwise direction. The polishing blocks  31  are disposed such that their respective top end surfaces are located on an identical plane. These top end surfaces form the polishing surface of the bottom side polishing head  30 . The polishing blocks  21  of the top side polishing head  20  and the polishing blocks  31  of the bottom side polishing head  30  are disposed so as to face to each other in the top-bottom direction. The dimension of each of the polishing surfaces of the polishing heads  20  and  30  in the transfer path widthwise direction is set to be greater than the dimension of the glass plate w in the transfer path widthwise direction. This not only allows both the surfaces of the glass plate w in their entirety to be exhaustively polished, but also makes it possible to use the polishing apparatus in accordance with the present embodiment when a glass plate whose transfer path widthwise direction dimension is smaller than that of the glass plate w is polished. 
     Arranged on one lateral side (right side in  FIG. 1 ) of the transfer path of the transfer mechanism  10  is a vibration mechanism  40  configured to vibrate the two polishing heads  20  and  30  so as to be repeatedly displaced in the transfer path widthwise direction in a prescribed dimension range. Here, the vibration mechanism  40  is configured to displace the two polishing heads  20  and  30  reversely relative to each other. Specifically, as indicated by a solid outline arrow in  FIG. 3  being a front view, when the top side polishing head  20  is displaced toward the opposite side relative to the transfer mechanism  10  (left side in the drawing), the bottom side polishing head  30  is displaced toward the transfer mechanism  10  side (right side in the drawing); and as indicated by a phantom outline arrow in  FIG. 3 , when the top side polishing head  20  is displaced toward the transfer mechanism  10  side (right side in the drawing), the bottom side polishing head  30  is displaced toward the opposite side relative to the transfer mechanism  10  (left side in the drawing). This allows the movements in the transfer path widthwise direction applied to the glass plate w by the vibration of the polishing heads  20  and  30  to cancel each other out, which in turn suppresses deviation of the glass plate w in the transfer path widthwise direction. A specific exemplary mode of the vibration may be an amplitude of several mm and a frequency of several times per second. 
     As shown in  FIG. 4 , which is a cross-sectional view in which the substantial portion of  FIG. 3  is shown in an enlarged manner, the polishing heads  20  and  30  are provided with, in a successive manner, water supply mechanisms  50  configured to supply water to both the surfaces of the glass plate w. Specifically, the polishing heads  20  and  30  are each provided with a plurality of (five in the exemplarily shown case) water spray nozzles  51  for splaying water on the corresponding surfaces of the glass plate w being polished by the polishing heads  20  and  30 . As shown in  FIG. 5 , which is a cross-sectional view taken along line V-V in  FIG. 3 , the water spray nozzles  51  in the top side polishing head  20  are each disposed at a substantially central position among two long line side polishing blocks  21  adjacent to each other in the transfer path widthwise direction (right-left direction in the drawing) and one short line side polishing block  21  close to the two long line side polishing blocks  21 . The water spray nozzles  51  are arranged such that their respective water spray ports are positioned farther than the end surfaces of the polishing blocks  21  of the polishing head  20  relative to the corresponding surface of the glass plate w (see  FIG. 4 ). The water spray nozzles  51  are connected to the outlet side of a water supply unit  52  by not-shown piping, and configured to be supplied with water from the water supply unit  52  via the piping and to spray the water from the water spray ports. This creates a water layer on the surface of the glass plate w, which water layer suppresses sliding resistance between the polishing blocks  21  and the glass plate w. Such reduced sliding resistance can suppress damage such as scratches done on the surface of the glass plate w. Further, any foreign object such as polishing debris resulted from the polishing is washed away by the sprayed water and expelled from the surface of the glass plate w. Thus, it becomes possible to prevent such an event that the foreign object is dragged by or tangled with the polishing blocks  21 . In particular, even in a situation where static electricity tends to build up due to friction associated with the polishing, such an electrostatic buildup can be suppressed by the water layer. Accordingly, it becomes possible to prevent such an event that the foreign object remains on the surface of the glass plate w due to such an electrostatic buildup. It is noted that description of the bottom side polishing head  30  is the same as the foregoing description with the polishing blocks  21  replaced by the polishing blocks  31  and, therefore, the description thereof is omitted. It is further noted that downward arrows each between the polishing blocks  21  of the top side polishing head  20  in  FIG. 3  and upward arrows each between the polishing blocks  31  of the bottom side polishing head  30  represent the state of water being sprayed by the water supply mechanism  50 . 
     Next, the operation of the polishing apparatus structured as described above will be described. 
     The glass plate w carried in the horizontal state is placed on the transfer rollers  11 , which are on the upstream side of the transfer direction T, of the transfer mechanism  10  while being kept in the horizontal state. Then, the glass plate w is transferred in the transfer direction T on the transfer rollers  11  by the operation of the transfer mechanism  10 , and enters the gap between the two top and bottom polishing heads  20  and  30  from its front end portion in terms of the transfer direction T. Relative to the glass plate w, the two polishing heads  20  and  30  are vibrated by the vibration mechanism  40  in the transfer path widthwise direction. In accordance with the vibration, the top side polishing head  20  polishes the top surface of the glass plate w in the transfer path widthwise direction, and the bottom side polishing head  30  polishes the bottom surface of the glass plate w in the transfer path widthwise direction. On the other hand, the glass plate w is transferred in the transfer direction T by the transfer mechanism  10  while being polished by the two polishing heads  20  and  30 . Hence, the glass plate w has its both surfaces simultaneously polished while being transferred. 
     Further, when the polishing is carried out, the water sprayed from the water spray nozzles  51  forms water layers on the corresponding surfaces of the glass plate w, which water layers suppress the sliding resistance between the glass plate w and the polishing blocks  21  and  31 , respectively. Thus, it becomes possible to prevent such an event that damage such as scratches done to the glass plate w by the polishing blocks  21  and  31 . Further, because any foreign object such as polishing debris is washed away by the flowing water, such a foreign object is expelled without being remained on the glass plate w. 
     In the manner described above, the glass plate w having its both surfaces simultaneously polished while being transferred is carried out from a rear end portion of the transfer path for the next process while being kept in the horizontal state. 
     Hence, in accordance with the present embodiment, in a manufacturing process of a product that is manufactured using a glass plate was one of its materials, in a polishing apparatus used in a polishing step of polishing both the surfaces of the glass plate w, the two polishing heads  20  and  30  disposed so as to sandwich both the surfaces of the glass plate w being transferred by the transfer mechanism  10  are vibrated by the vibration mechanism  40  in the direction perpendicular to the transfer direction T. Thus, it becomes possible to simultaneously polish both the surfaces of the glass plate w while transferring it. Therefore, as compared to the conventional cases in which a glass plate is polished on a one surface-by-one surface basis while being transferred, or in which a glass plate has its both surfaces simultaneously polished while being stopped, the present invention can contribute toward shortening the takt time of the polishing step itself, and eventually that of the entire manufacturing process. 
     Note that, in the above-described embodiment, the glass plate w is transferred in the horizontal state (where an angle α relative to level plane is: α=0°) and the two polishing heads  20  and  30  are disposed so as to face each other in the top-bottom direction. However, in a situation where, for example, the glass plate w is carried in a state inclined by a prescribed angle α (0°&lt;α≦90°) relative to the level plane (including the vertical state), the glass plate w may be transferred in substantially the same inclined state as in the carried-in state, and the two polishing heads  20  and  30  may be disposed so as to face each other in a direction approximately perpendicular to the inclination plane. 
     Further, in the above-described embodiment, the two polishing heads  20  and  30  are displaced in the transfer path widthwise direction (the direction in which angle β relative to the transfer direction T is: β=90°). However, they may be displaced in a direction in which angle β relative to the transfer direction T is smaller than 90° (β&lt;90°, where 0°&lt;β). In such a case, however, the dimension of each of the polishing surface of the polishing heads  20  and  30  in the displace direction must be increased and/or the amplitude of the polishing heads  20  and  30  must be increased. 
     Still further, in the above-described embodiment, in forming the polishing surfaces of the polishing heads by a plurality of polishing blocks, each of the polishing blocks is set to have a substantially columnar shape. However, the shape of the polishing blocks is not limited to a substantially columnar shape, and they may each be formed in any of various three-dimensional shapes. 
     Still further, in the above-described embodiment, the polishing surfaces are each formed by a plurality of polishing blocks. However, the polishing surfaces may each be formed by one polishing block. In this case, the polishing block itself may be provided with a port for establishing water channel, and the polishing block may be provided with grooves or the like at its polishing surface so as to facilitate water flow or expulsion of any foreign object by the water flow. 
     Still further, in the above-described embodiment, the description has been given of a case where, in the manufacturing process of a product that is manufactured using a glass plate was one of its materials, the glass plate w has its both surfaces polished. However, the present invention is applicable to a polishing apparatus configured to polish both surfaces of any of various plate materials other than the glass plate w. 
     INDUSTRIAL APPLICABILITY 
     The present invention is useful to a polishing apparatus and a polishing method with which both surfaces of a plate material such as a glass plate are polished, as described in the foregoing. 
     DESCRIPTION OF REFERENCE CHARACTERS 
     
         
           10  Transfer Mechanism 
           20  Top Side Polishing Head (Polishing Head) 
           21  Polishing Block 
           30  Bottom Side Polishing Head (Polishing Head) 
           31  Polishing Block 
           40  Vibration Mechanism 
           50  Water Supply Mechanism (Liquid Supply Mechanism) 
           51  Water Spray Nozzle (Discharge Nozzle) 
         T Transfer Direction 
         w Glass Plate (Plate Material)