Patent Publication Number: US-2011053466-A1

Title: Glass substrate spacer separating system and glass substrate fabricating method

Description:
BACKGROUND 
     1. Field of the Invention 
     The present invention relates to a glass substrate spacer separating apparatus for separating spacers adhering to main planes of glass substrates from the glass substrates and a glass substrate manufacturing method. 
     2. Description of the Related Art 
     For example, in a manufacturing process for manufacturing circular disc-shaped glass substrates, there is a machining process of machining planes and end faces of glass substrates including a grinding or abrasion step. For example, as a method for enhancing the abrasion efficiency of end faces of glass substrates, there is used a method comprising steps of preparing a stacked body of glass substrates in which a plurality of (for example, some several hundreds) glass substrates are stacked one on another via resin spacers in a plane direction and grinding or abrading end faces of so many glass substrates at the same time. 
     On completion of the machining of the end faces of the stacked body of glass substrates, a spacer separating and glass substrate loading work needs to be performed before the glass substrates are transported to a subsequent step of grinding or abrading plane portions of the glass substrates. In the spacer separating and glass substrate loading work, glass substrates are separated piece by piece from the stacked body of glass substrates, and further, spacers are separated from the glass substrates. Then, resultant spacer-free glass substrates are loaded in a predetermined cassette. This step of separating the glass substrates piece by piece from the stacked body of glass substrates for loading in the cassette has been mainly implemented by the hands of workers. 
     However, in the manual separation approach, the planes of the glass substrates are pressed against by one another, and therefore, the spacers cannot easily be separated from the glass substrates, leading to a problem that many labor hours have to be involved in the approach. 
     Then, as methods for separating glass substrates piece by piece from a stacked body of glass substrates and removing spaces from the glass substrates so separated, there have conventionally been proposed approaches. For example, in one approach, with a stacked body of glass substrates submerged in a liquid of a tank, upper planes of glass substrates are sucked by a jig such as a vacuum sucking pad so as to be separated from one another, and at the same time, a water pressure is applied to the stacked body of glass substrates so as to remove spacers from the glass substrates, as disclosed in JP-A-2008-302448. In the other approach, an arm is used which grips on an end face of a glass substrate at a plurality of portions (at least three portions), and the arm is raised while applying a flow of water, a brush and ultrasonic waves to the glass substrate so gripped so that a spacer is removed from the glass substrate at the same time as the glass substrate is separated from a stacked body of glass substrates, as disclosed in JP-A-2008-307612, JP-A-2009-48735 and JP-A-2009-48688. 
     In the methods for separating the spacers from the glass substrates by use of the conventional approaches, however, since the spacers closely attached to the main planes of the glass substrates are separated piece by piece from the glass substrates in a secured fashion, it takes time in separating the spacers, leading to a problem that the production efficiency is lowered. 
     SUMMARY 
     In view of these situations, an object of the invention is to provide a glass substrate spacer separating apparatus which solves the aforesaid problem and a glass substrate manufacturing method. 
     According to the invention, there is provided a glass substrate spacer separating apparatus including: a cassette adapted to load a plurality of glass substrates with spacers attached thereto in such a state that the plurality of glass substrates are separated piece by piece; a liquid tank adapted to store a liquid in which the cassette is to be submerged; and a bubble generating mechanism configured to generate bubbles which move towards an interior of the cassette which is submerged in the liquid of the liquid tank, wherein the spacers are separated individually from the plurality of glass substrates to which the spacers are attached by bringing the bubbles generated from the bubble generating mechanism into contact with surfaces of the plurality of glass substrates with spacers attached thereto which are loaded in the cassette in the liquid of the liquid tank 
     The liquid tank may include a moving mechanism for moving the cassette so as to change a relative position of the cassette to the bubble generating mechanism. 
     The bubble generating mechanism may include: a bubble generating unit which is provided at a bottom portion of the liquid tank and in which a plurality of holes are provided for generating bubbles in the liquid; a compressed gas source which is provided outside of the liquid tank, the compressed gas source being configured to supply a compressed gas to the bubble generating unit; a pressure regulator valve configured to regulate a pressure of the compressed gas supplied from the compressed gas supply source to a predetermined pressure; and a connection pipe configured to supply the compressed gas whose pressure is regulated by the pressure regulator valve to the bubble generating unit. 
     The bubble generating unit may include a plurality of holes whose opening diameter ranges from 0.2 mm to 2.0 mm on a surface of a tube or a flat plate. 
     The holes may be formed at intervals which are 0.2 to 2 times larger than glass substrate loading intervals at which the glass substrates with spacers attached thereto are loaded in the cassette in such a state that the glass substrates with spacers attached thereto are separated piece by piece. 
     The glass substrate spacer separating apparatus may further includes: a separate liquid tank provided inside or outside the liquid tank, the separate liquid tank being configured to collect the spacers separated from the glass substrates in the liquid tank; and a liquid supply mechanism configured to supply a liquid so that the liquid of the liquid tank overflows into the separate liquid tank. 
     The spacers separated in the liquid tank may be caused to move into the separate liquid tank together with the liquid which overflows from the liquid tank for collecting thereof. 
     The liquid tank may include an ultrasonic wave radiating mechanism configured to radiate ultrasonic waves to the glass substrates with spacers attached thereto which are loaded in the cassette which is submerged in the liquid. 
     According to another aspect of the invention, there is provided a glass substrate manufacturing method including: preparing a stacked body of glass substrates in which pluralities of glass substrates and spacers are stacked alternately one on another and abrading peripheral end surfaces of the glass substrates of the stacked body of glass substrates; separating the glass substrates from the stacked body of glass substrates after the abrasion of the peripheral end surface of the glass substrates has been performed; and separating the spacers adhering to main planes of the glass substrates from the glass substrates, wherein the glass substrate spacer separating apparatus set forth under any of the above is used to separate the spacers from the glass substrates in the separating of the spacers. 
     The spacers may be formed of a material whose specific gravity is lighter than that of the liquid stored in the liquid tank. 
     The glass substrates maybe glass substrates for magnetic recording media. 
     According to the invention, the spacers can be separated individually from the plurality of glass substrates to which the spacers are attached for collecting thereof with good efficiency by bringing the bubbles generated from the bubble generating mechanism into contact with the surfaces of the plurality of glass substrates with spacers attached thereto which are loaded in the cassette in the liquid of the liquid tank. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present invention will become more fully understood from the detailed description given hereinbelow and the accompanying drawing which is given by way of illustration only, and thus is not limitative of the present invention and wherein: 
         FIG. 1  is a schematic sectional view showing the configuration of an embodiment of a glass substrate spacer separating apparatus according to the invention; 
         FIG. 2  is a plan view of the glass substrate spacer separating apparatus shown in  FIG. 1 ; 
         FIG. 3  is a vertical sectional view, as viewed sideways, of a liquid tank showing an interior configuration thereof; 
         FIG. 4  is a vertical sectional view, as viewed from the front, of an interior of a cassette; 
         FIG. 5  is a schematic sectional view showing the configuration of Modified Example 1 of a glass substrate spacer separating apparatus according to the invention; 
         FIG. 6  is a plan view of the glass substrate spacer separating apparatus shown in  FIG. 5 ; 
         FIG. 7  is a schematic sectional view showing the configuration of Modified Example 2 of a glass substrate spacer separating apparatus according to the invention; and 
         FIG. 8  is a plan view of the glass substrate spacer separating apparatus shown in  FIG. 7 . 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Hereinafter, a mode for carrying out the invention will be described by reference to the drawings. 
       FIG. 1  is a schematic sectional view showing the configuration of Embodiment 1 of a glass substrate spacer separating apparatus according to the invention.  FIG. 2  is a plan view of the glass substrate spacer separating apparatus shown in  FIG. 1 . 
     As is shown in  FIGS. 1 and 2 , a glass substrate spacer separating apparatus  10  includes a liquid tank  20 , a cassette supporting mechanism  30  and a bubble generating mechanism  40 . The liquid tank  20  has a rectangular parallelepiped box shape. The liquid tank  20  has an opening  22  at an upper side thereof. Service water or pure water or a liquid to which a surface-active agent, acid or alkali is added is stored in an interior of the liquid tank  20 . 
     The cassette supporting mechanism  30  has a cassette resting portion  32  which is made up of a grid-like member and on which a plurality of (four in this embodiment) cassettes  50  are rested, suspending portions  34  which extend upwards (in a vertical direction) from both sides of the cassette resting portion  32  and sliding portions  36  which extend sideways (in a horizontal direction) from upper ends of the suspending portions  34 . The sliding portions  36  are rested at an upper end portion  24  of the liquid tank  20  and are provided slidably along the upper end portion  24  of the liquid tank  20  in X directions (horizontal directions). In each cassette  50 , substrate loading portions  80  (refer to  FIG. 3 ) are aligned in a longitudinal direction, and glass substrates  70  with spacers attached thereto are loaded individually in their corresponding substrate loading portions  80 . 
     Here, a manufacturing process for manufacturing glass substrates  70  will be described. 
     In a manufacturing process for manufacturing circular disc-shaped glass substrates  70 , there is a machining process of machining planes and end faces of glass substrates  70  which includes a grinding/abrasion step. In this grinding/abrasion step, for example, as a method for enhancing the abrasion efficiency of end faces of glass substrates  70 , a stacked body of glass substrates is prepared in which a plurality of (for example, some several hundreds) glass substrates  70  are stacked one on another via resin spacers S in a plane direction, and end faces of so many glass substrates  70  are ground or abraded at the same time. 
     On completion of the grinding/abrasion step of grinding or abrading the end faces of the stacked body of glass substrates, a glass substrate and spacer separating step is performed before the glass substrates  70  are transported to a subsequent step of grinding or abrading plane portions of the glass substrates  70 . In this separating step, the glass substrates  70  are separated piece by piece from the stacked body of glass substrates, and following this, spacers S which are closely attached to main planes of the glass substrates  70  are separated piece by piece from the glass substrates  70 . 
     In this embodiment, in order to implement the spacer separation with good efficiency, the glass substrates  70  with spacers in which the spacers S are closely attached to the main planes of the glass substrates  70  are loaded in substrate loading portions in the predetermined cassettes  50 . 
     Each cassette  50  has a plurality of substrate loading portions  80  for loading glass substrates  70  with spacers. Each substrate loading portion  80  is adapted to load one glass substrate  70  with a spacer. Thus, in each cassette  50 , a plurality of glass substrates  70  with spacers are aligned at predetermined intervals in such a state that the glass substrates  70  with spacers are loaded in their corresponding substrate loading portions  80  individually. Consequently, the respective glass substrates  70  with spacers are held in such a state that their respective main planes are spaced apart from each other at predetermined intervals by the glass substrates  70  with spacers being loaded in their corresponding loading portions  80  individually. 
     In this embodiment, the cassettes  50  which are supported on the cassette supporting mechanism  30  can be moved in the X directions (in the horizontal directions) in a reciprocating motion by moving manually the sliding portions  36  in the X directions. Alternatively, a configuration may be adopted in which the cassettes  50  supported on the cassette supporting mechanism  30  are moved by driving the sliding portions  36  in the X directions (in the horizontal directions) by an actuator such as an air cylinder. 
     The bubble generating mechanism  40  has a bubble generating unit  42  which is provided at a bottom portion of the liquid tank  20  and in which a plurality of bubble spouting holes  41  are provided through which bubbles are generated into the liquid, a compressed gas source  44  which is provided outside the liquid tank  20  for supplying a compressed gas to the bubble generating unit  42 , a pressure regulator valve  46  for regulating a pressure of the compressed gas supplied from the compressed gas source  44  to a predetermined pressure and a connection pipe  48  through which the compressed gas whose pressure is regulated by the pressure regulator valve  46  is supplied to the bubble generating unit  42 . 
     The bubble generating unit  42  is made up of a cylindrical hollow tube, for example. The plurality of bubble spouting holes  41  are provided in a line, and the spouting holes  41  penetrate the bubble generating unit  42  from an inner circumference to an outer circumference thereof. An opening diameter of the bubble spouting hole  41  ranges from 0.2 mm to 2.0 mm. The opening diameter of the bubble spouting hole  41  preferably ranges from 0.5 to 1.5 mm and further preferably ranges from 0.7 to 1.3 mm. The plurality of bubble spouting holes  41  may be provided at random or in a zigzag fashion on an upper side of the hollow member. 
     The bubble generating unit  42  is supported at a predetermined height by means of height adjusting portions  60  which are fixed to the bottom portion of the liquid tank  20  so as to extend in the X direction (in the horizontal direction). Since the height adjusting portions  60  can be replaced by height adjusting portions  60  of arbitrary heights selectively, a distance L defined between the plurality of bubble spouting holes  41  which are disposed on the upper side of the bubble generating unit  42  and the cassettes  50  which are supported on the cassette supporting mechanism  30  can be set to a predetermined distance (for example, 10 mm to 100 mm). 
     In this embodiment, two bubble generating units  42  are arranged in parallel at the bottom portion of the liquid tank  20 , and each bubble generating unit  42  is connected to the pressure regulator valve  46  and the compressed gas source  44  via the connection pipe  48 . The number of bubble generating units  42  which are to be disposed in the liquid tank  20  is not limited to two, and hence, three or more bubble generating units may be provided. A configuration may be adopted in which the bubble generating units  42  are disposed in parallel below the cassettes  50 . Alternatively, the bubble generating units  42  may be disposed obliquely to the direction in which the cassettes  50  extend by being inclined at a predetermined angle in a vertical direction. 
     The compressed gas source  44  includes an air compressor for producing compressed air and a tank for storing compressed air so produced, for example. The pressure regulator valve  46  is provided along the length of the connection pipe  48  which connects the bubble generating units  42  and the compressed gas source  44  for regulating a supply pressure at which the compressed air is supplied via the connection pipe  48  by changing its valve opening. 
     The pressure regulator valve  46  is designed to automatically regulating its valve opening so as to hold a preset supply pressure (for example, 5 kg/cm 2 ). The pressure regulator valve  46  regulates the supply pressure of compressed air so that the size of bubbles spouted from the plurality of bubble spouting holes  41  in the bubble generating units  42  becomes a predetermined size (for example, of the order of 1 mm to 2 mm). 
     Bubbles generated from the plurality of bubble spouting holes  41  which are formed on the upper side of the bubble generating units  42  are spouted towards interiors of the cassettes  50  which are disposed thereabove and rise by virtue of buoyancy so as to be brought into contact with the plurality of glass substrates  70  which are loaded in the cassettes  50  and surfaces of the resin spacers S which are closely attached to the main planes of the glass substrates  70 , whereby the resin spacers S can be separated from their corresponding glass substrates  70  by making use of the buoyancy of bubbles. 
     Here, the function of bubbles spouted into the liquid by the bubble generating mechanism  40  will be described. 
       FIG. 3  is a vertical sectional view, as viewed sideways, of the liquid tank  20  showing an interior configuration thereof.  FIG. 4  is a vertical sectional view, as viewed from the front, of an interior of the cassette  50 . As is shown in  FIGS. 3 and 4 , the plurality of substrate loading portions  80  are aligned in the interior of the cassette  50 . Partitions  90  are formed on both sides of each substrate loading portion  80  in a laterally symmetrical fashion. An inclined step portion  92  is formed on each partition  90  so that an outer circumference of the glass substrate  70  is brought into abutment therewith. Further, each substrate loading portion  80  has a lower opening  82  which is opened downwards and an upper opening  84  which is opened upwards. 
     The respective lower openings  82  of the substrate loading portions  80  form a bubble inlet port which extends in the X direction so as to confront the bubble generating unit  42 . The cassette supporting mechanism  30  which supports the cassettes  50  is configured so that the cassette resting portion  32 , which is formed by causing wires extending in the X and Y directions to intersect each other, is suspended by the suspending portions  34  which are disposed on both sides of the cassette resting portion  32 . The cassette resting portion  32  is disposed so that bubbles spouted from the plurality of bubble spouting holes  41  in the bubble generating units  42  pass through openings defined between the wires forming the cassette resting portion  32  so as to flow into the respective lower openings  82  of the substrate loading portions  80 . The cassette resting portion  32  maybe formed by other materials than the wires such as rods or plates which are placed laterally. 
     The resin spacers S (indicated by an alternate long and short dash line in  FIG. 3 ) are closely attached to the main planes of the glass substrates  70  which are loaded individually in their corresponding substrate loading portions  80 . Note that the resin spacer S is formed of a material whose specific gravity is lighter than that of the liquid stored in the liquid tank  20 . 
     When compressed air whose pressure is regulated by the pressure regulator valve  46  is supplied to the bubble generating units  42 , bubbles are spouted upwards from the plurality of bubble spouting holes  41  in the bubble generating units  42 . Intervals P at which the bubble spouting holes  41  are aligned in the X direction are set to be 0.2 to 2 times larger than intervals B at which the glass substrates  70  are loaded in the cassettes  50 . Bubbles spouted from the plurality of bubble spouting holes  41  continue to flow into the lower openings  82  of the cassettes  50  which are disposed thereabove and rise in the respective substrate loading portions  80  to reach a liquid surface lying above the upper openings  84 . 
     Consequently, groups of bubbles which flow into the substrate loading portions  80  from their lower openings  82  come into contact with the spacers S which are closely attached to the main planes of the glass substrates  70  loaded individually in the substrate loading portions  80 , whereby lower edge portions of the spacers S are turned upwards. The sliding portions  36  are caused to reciprocate in the X directions along the upper end portion  24  of the liquid tank  20  at the same time as bubbles are spouted. By doing so, the cassettes  50  rested on the cassette resting portion  32  are moved in the X directions in the liquid tank  20  so that bubbles come into contact with the spacers S in a uniform fashion in the respective interiors of the cassettes  50 . 
     As is shown in  FIG. 4 , lower end portions of the spacers S which are separated from the main planes of the glass substrates  70  are curved into a U-like shape to project from the glass substrates  70  so as to close bubble rising passages, whereby the lower end portions so curved function to increase surface areas with which bubbles come into collision. Because of this, when part of the spaces S are turned up from lower sides of the main planes of the glass substrates  70  as a result of the contact of bubbles with the spacers S, the contact areas of bubbles with the spacers S are gradually increased thereafter, whereby a force which pulls the spacers S upwards is increased. 
     In this way, the respective spacers S which are closely attached to the glass substrates  70  can be separated almost simultaneously in the process of groups of bubbles spouted from the bubble spouting holes  41  in the bubble generating units  42  rising to pass through the respective substrate loading portions  80 . Thus, the spacers S can be separated from all the glass substrates  70  loaded in the cassettes  50  within a short period of time. By the operator moving the cassette supporting mechanism  30  in the X directions, liquid resistance is imparted to the spacers S, whereby the separation of the individual spacers S which have started to be separated from the corresponding glass substrates  70  as a result of contact with bubbles from the glass substrates  70  is promoted further by the liquid resistance and the action of the bubbles. 
     Since their specific gravity is lighter than that of water, the spacers S which are separated from the glass substrates  70  are allowed to float in proximity to the liquid surface of the liquid tank  20 . Thus, the operator can easily collect the spacers S. 
       FIG. 5  is a schematic sectional view showing the configuration of Modified Example 1 of a glass substrate spacer separating apparatus according to the invention.  FIG. 6  is a plan view of the glass substrate spacer separating apparatus shown in  FIG. 5 . Note that in  FIG. 6 , the configuration of a cassette resting portion  32  is omitted from illustration in order to make clear constituent portions which are disposed below the cassette resting portion  32 . 
     As is shown in  FIGS. 5 and 6 , a glass substrate spacer separating apparatus  100  according to Modified Example 1 of the invention has a liquid tank  20 , a cassette supporting mechanism  30  and a bubble generating mechanism  40 , which are like to those described in Embodiment 1 above, as well as a collecting tank  110 . The collecting tank  110  is provided on a left-hand side of the liquid tank  20  for collecting spacers S which are separated from glass substrates  70  together with liquid that overflows from the liquid tank  20 . Note that the collecting tank  110  may be provided in an interior of the liquid tank  20  or may be provided adjacent to an outside of the liquid tank  20 . 
     In addition, a liquid supply mechanism  120  is provided in the liquid tank  20 . The liquid supply mechanism  120  has a plurality of water current generating nozzles  122 , a water supply pipe  124 , a water pressure regulator valve  126 , a pump  128 , a drain pipe  130 , and a filter  132 . The water current generating nozzles  122  are provided at a bottom portion of the liquid tank  20  for spouting water currents towards cassettes  50  lying thereabove. The water supply pipe  124  is connected to the water current generating nozzles  122  at points along the length thereof and is connected to a discharge port of the pump  128  at the other end thereof. The water pressure regulator valve  126  is provided in a position along the length of the water supply pipe  124  for regulating a pressure of water discharged from the pump  128  to a preset pressure. The pump  128  is preferably actuated to operate while being linked with the compressed gas source  44  of the bubble generating mechanism  40  and is switched on and off to generate water currents at the same time as bubbles are generated in the liquid tank  20 . Note that the pump  128  may not be linked with the bubble generating mechanism  40 . Instead, the pump  128  may be actuated to operate periodically at predetermined time intervals. Alternatively, the pump  128  can be actuated to operate as required depending upon the separating conditions of the spacers S. 
     The drain pipe  130  is connected to a bottom portion of the collecting tank  110  at one end and is connected to a suction port of the pump  128  at the other end thereof. The filter  132  is provided in a position along the length of the drain pipe  130  for removing foreign matters contained in the liquid discharged. 
     When the pump  128  is actuated, liquid of the collecting tank  110  is discharged from the bottom portion via the drain pipe  130 , foreign matters contained in the liquid so discharged are filtered out by the filter  132 , and only the liquid from which the foreign matters are removed is sucked into the pump  128  via the suction port thereof. Further, pressurized water is discharged from the discharge port of the pump  128 , and liquid whose pressure is regulated by the water pressure regulator valve  126  is spouted from the plurality of water current generating nozzles  122  towards the cassettes  50 . By doing this, bubbles from a plurality of bubble spouting holes  41  of bubble generating units  42  and water currents from the water current generating nozzles  122  are forcibly emitted into respective substrate loading portions  80  in interiors of the cassettes  50  from bottom to top thereof. 
     Because of this, groups of bubbles and water currents flow into respective substrate loading portions  80  of the cassettes  50  from lower openings  82  thereof so that spacers S closely attached to the glass substrates  70  loaded individually in the corresponding substrate loading portions  80  can be separated altogether from the corresponding glass substrates  70  with good efficiency within a short period of time to float near the surface of liquid of the liquid tank  20 . 
     A recess portion  142  is provided at an upper end of wall portion  140  which defines a boundary between the collecting tank  110  and the liquid tank  20 . Since the recess portion  142  is provided in a position which is lower in level than the liquid surface of the liquid tank  20 , the spacers S floating near the liquid surface of the liquid tank  20  are discharged into the collecting tank  110  together with liquid that flows out of the liquid tank  20  to the collecting tank  110  side. Then, the spacers S separated from the glass substrates  70  are light in specific gravity than water, the spacers S are floating near the surface of liquid of the collecting tank  110 . Thus, the operator can collect the spacers S with ease. 
       FIG. 7  is a schematic sectional view showing the configuration of Modified Example 2 of a glass substrate spacer separating apparatus according to the invention.  FIG. 8  is a plan view of the glass substrate spacer separating apparatus shown in  FIG. 7 . In  FIG. 8 , the configuration of a cassette resting portion  32  is omitted from illustration in order to make clear constituent portions which are disposed below the cassette resting portion  32 . 
     As is shown in  FIGS. 7 and 8 , a glass substrate spacer separating apparatus  200  according to Modified Example 2 of the invention has a liquid tank  20 , a cassette supporting mechanism  30 , a bubble generating mechanism  40 , a collecting tank  110  and a liquid supply mechanism  120 , as well as a vibration mechanism  210 . 
     The vibration mechanism  210  is made up of a vibration plate  212  closely attached to a lateral side of the liquid tank  20  and an ultrasonic oscillator  214  for inputting a vibration signal for generating ultrasonic waves into the vibration plate  212 . The vibration plate  212  vibrates by receiving a vibration signal from the ultrasonic oscillator  214  to propagate ultrasonic waves to a liquid of the liquid tank  20  via the liquid tank  20 . Since ultrasonic waves are propagated to cassettes  50  which are submerged in the liquid of the liquid tank  20  via the liquid, glass substrates  70  which are loaded individually in corresponding substrate loading portions  80  vibrate. 
     The attaching position of the vibration plate  212  is not limited to the lateral side of the liquid tank. For example, the vibration plate  212  may be attached to a lower side of the liquid tank  20 . Additionally, instead of being provided on the outside of the liquid tank  20 , a configuration may be adopted in which the vibration plate  212  is provided on an inner wall of the liquid tank  20 . Alternatively, a vibration member able to be placed in liquid may be submerged in the liquid stored in the liquid tank  20  in place of the vibration plate  212 . 
     The ultrasonic oscillator  214  is preferably actuated to operate while being linked with a compressed gas source  44  of the bubble generating mechanism  40  and a pump  128  of the liquid supply mechanism  120  and is switched on and off to generate vibrations at the same time as bubbles are generated in the liquid tank  20 . Note that the ultrasonic oscillator  214  may not be linked with the compressed gas source of the bubble generating mechanism  40  and the pump  128  of the liquid supply mechanism  120 . Instead, the ultrasonic oscillator  214  may be actuated to operate periodically at predetermined time intervals. Alternatively, the ultrasonic oscillator  214  can be actuated to operate as required depending upon the separating conditions of the spacers S. 
     Because of this, when the pump  128  is actuated, liquid whose pressure is regulated by a water pressure regulator  126  is spouted towards the cassettes  50  from a plurality of current generating nozzles  122 , and the vibration plate  212  vibrates by a vibration signal from the ultrasonic oscillator  214  so as to propagate ultrasonic waves to the right lateral side of the liquid tank  20 . Then, bubbles from a plurality of bubble spouting holes  41  in bubble generating units  42  and water currents from the water current generating nozzles  122  are forcibly emitted into respective substrate loading portions  80  in interiors of the cassettes  50  from bottom to top thereof. 
     By doing this, since the water currents containing mixed bubbles and vibrations in the form of ultrasonic waves are propagated to the respective glass substrates  70  loaded individually in the corresponding substrate loading portions  80 , spacers S closely attached to the glass substrates  70  can be separated altogether from the glass substrates  70  within a short period of time so as to allow them to float near the liquid surface of the liquid tank  20 . 
     Then, the spacers S floating near the liquid surface of the liquid tank  20  are discharged into the collecting tank  110  together with liquid which flows out of the liquid tank  20  towards the collecting tank  110  side and float near the surface of liquid of the collecting tank  110 . Because of this, the operator can collect the spacers S floating near the liquid surface of the collecting tank  110  with ease. The generation of bubbles and water currents by the bubble generating mechanism  40  and the liquid supply mechanism  120  and the propagation of ultrasonic waves by the vibration plate  212  may be caused to occur at the same time or the individual mechanisms maybe designed to be actuated arbitrarily at different points in time. Alternatively, the individual mechanisms can be combined selectively for operation. 
     In Modified Example 2, a configuration may be adopted in which the liquid supply mechanism  120  is removed. As this occurs, bubbles from the plurality of bubble spouting holes  41  in the bubble generating units  42  are forcibly emitted into the respective substrate loading portions  80  in the interiors of the cassettes  50 , and additionally vibrations in the form of ultrasonic waves are propagated to the substrate loading portions  80 , thereby making it possible to promote the separation of the spacers S. 
     In general, a manufacturing process for manufacturing a glass substrate for a magnetic recording medium and a magnetic disk involves the following steps. 
     (1) A glass substrate stock formed through a floating method, a fusion method or a press molding method is machined into a disk (a circular disk) shape, and thereafter, an inner peripheral end surface and an outer peripheral end surface of the disk are chamfered. (2) Upper and lower main planes of the glass substrate are ground. (3) Inner and outer peripheral end surfaces and the inner and outer peripheral chamfered surfaces are end abraded. (4) The upper and lower main planes of the glass substrate are abraded. The abrading step may involve a primary abrasion or both a primary abrasion and a secondary abrasion (an abrasion in which abrasive grains are used which are finer than abrasive grains used in the primary abrasion) with a tertiary abrasion performed arbitrarily after the secondary abrasion (an abrasion in which abrasive grains are used which are finer than abrasive grains used in the secondary abrasion). (5) The glass substrate is precision washed to obtain a glass substrate for a magnetic recording medium. (6) A film such as a magnetic layer is formed on the glass substrate for a magnetic recording medium, whereby a magnetic disk is manufactured. 
     In the manufacturing process for manufacturing a glass substrate for a magnetic recording medium and a magnetic disk, the glass substrate may be washed between the individual steps (an inter-step washing), and surfaces of the glass substrate may be etched between the individual steps (an inter-step etching). Further, in the event that a high mechanical strength is required for a glass substrate for a magnetic recording medium, a reinforcement step (for example, a chemical reinforcement step) of forming a reinforcement layer on a surface layer of the glass substrate may be performed before the abrasion step or after the abrasion step or between abrasion steps. 
     In the invention, the glass substrate for a magnetic recording medium may be an amorphous glass or a crystallized glass or a reinforced glass having a reinforcement layer on the surface layer of the glass substrate (for example, a chemically reinforced glass). In addition, the glass substrate stock for the glass substrate of the invention may be such as to be formed through the floating method, the fusion method or the press molding method. 
     The invention relates to the step (3) in which the inner and outer peripheral end surfaces and the inner and outer peripheral chamfered surfaces are end abraded and relates to the spacer separation step in which the stacked body of glass substrates for magnetic recording media is prepared, the end portions of the glass substrates of the stacked body of glass substrates are abraded and thereafter the glass substrates are separated from the stacked body of glass substrates, and the spacers adhering to the main planes of the glass substrates are separated from the glass substrates. 
     While the embodiment is described as the four cassettes  50  being submerged in the liquid of the liquid tank  20 , the invention is not limited thereto. Hence, four or more cassettes  50  may be submerged in the liquid of the liquid tank  20 . 
     In addition, while the embodiment is described as the two bubble generating units  42  being provided at the bottom portion of the liquid tank  20 , the invention is not limited thereto. Hence, the number of bubble generating units may be increased as required to match the number of cassettes  50 . 
     Additionally, while the embodiment is described as the bubble generating unit  42  being formed by arranging the bubble spouting holes  41  in the line in the hollow tube, the invention is not limited thereto. For example, a plurality of bubble generating nozzles may be arranged at the bottom portion of the liquid tank  20 . Alternatively, a configuration in which a plurality of bubble spouting holes are arranged in an upper side of a hollow flat plate-like member may be adopted as the bubble generating unit  42 .