JP2011063456A - Glass plate having bored hole and method for boring the glass plate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent the occurrence of troublesome cracks on the inner peripheral surface of a through-hole bored in a glass plate. <P>SOLUTION: A pair of drills having a conical peripheral surface where the grinding surface at the side peripheral part of the drill is reduced in diameter toward a tip part are used. A drill is intruded from one surface of the glass plate, a hole having an inner peripheral surface being reduced in diameter toward an intermediate part in the thickness direction of the glass plate from the surface of the glass plate and being the conical peripheral surface is bored and then the drill is made to go backward. Another drill is intruded from another surface of the glass plate to the opposite part of the hole, a hole having an inner peripheral surface being reduced in diameter toward the intermediate part in the thickness direction of the glass plate from the surface of the glass plate to the substantially middle part of the thickness of the glass plate and being the conical peripheral surface is bored and the drill is made to go backward and then the through-hole is bored in the glass plate. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a glass plate having a perforation and a method for perforating the glass plate, and more particularly to a technique for forming a through hole in a glass plate for a flat display panel.

  Glass substrates for flat display panels such as plasma display (PDP), field emission display (FED), electroluminescence display (ELP) and the like are used for exhausting the panel and introducing gas into the panel in the panel manufacturing process. In addition, a through hole is provided in a corner portion or a peripheral portion of the glass substrate. For example, in order to manufacture a PDP, an electrode for generating plasma discharge is formed, and a front glass substrate and a rear glass substrate are arranged facing each other, and the periphery thereof is sealed with sealing glass. After forming and exhausting the inside of the panel from the through hole provided in the back glass plate, a gas such as Ne is sealed in the panel to seal the through hole.

  As a method for forming the through hole, the method disclosed in Patent Document 1 below is known. In this method, as shown in FIG. 5, the first drill 12 a is inserted from the lower surface of the glass substrate 1 and then the first drill is retracted, and then the second drill 12 b is inserted from the upper surface of the glass substrate. 13 is formed. In this case, a cylindrical electrodeposited diamond drill or a sintered diamond drill having the same diameter in the axial direction is usually used as the drill, so that the inner peripheral surface of the through hole is a cylindrical grinding of the drill. Ground by the surface. Further, since the drill has a driving part that rotates with respect to the glass substrate and a sliding part that moves up and down, the drill during drilling has a runout caused by a slight gap between the driving part and the sliding part. Will occur.

  For this reason, when a through-hole is drilled in a glass substrate using this type of drill, a crack occurs due to the cylindrical grinding surface of the drill that runs out of contact with the inner peripheral surface of the through-hole. In particular, the crack formed when the second drill is retracted remains without being removed.

  When a flat display device is manufactured using a glass substrate having cracks on the inner peripheral surface of the through hole in this way, the glass substrate is heated to about 500 to 600 ° C. in a heat treatment process such as sealing with sealing glass. Therefore, thermal stress is generated around the through hole, and the glass substrate may be damaged due to the crack.

  Patent Document 2 discloses a method for preventing or suppressing the occurrence of such cracks. That is, in this method, when the upper drill is penetrated from the upper surface of the glass substrate to the middle in the thickness direction and then retracted, and then the lower drill is penetrated from the lower surface of the glass substrate to drill a through hole, the drill is used as the lower drill. Use a drill with a shape that reduces the diameter from the body (maximum outer diameter) to the tip of the drill, and use the upper drill to leave a glass with a thickness smaller than the axial length of the reduced diameter portion of the lower drill. After forming the lower drill, the lower drill is penetrated from the lower surface to reach the hole formed by the upper drill, and after reaching the lower drill, the lower drill is caused to penetrate along the hole, thereby reducing the runout of the lower drill and cracking. It is a deterrent.

JP-A-9-117896 JP 2008-137354 A

  In the drilling method of the through hole of Patent Document 1, since the grinding surface of the drill is cylindrical and a certain amount of drill runout is unavoidable, cracks (including scratches) generated on the inner peripheral surface of the hole are included. ) To a degree that does not cause breakage of the glass substrate in the manufacture of the display panel. In particular, when a plurality of display panels (six in FIG. 6) are manufactured together in parallel using a large glass substrate 1 as illustrated in FIG. 6 and then cut to obtain a plurality of panels. Since the exhaust holes 13 for exhausting the gas in each panel and introducing gas into the panel are provided in the glass substrate 1 corresponding to each panel, the glass substrate 1 is subjected to heat treatment at the time of manufacturing the display panel. Is heated, a large stress is generated around the through hole of the panel located in the middle of the parallel. Therefore, if there is a defect crack that causes damage to the inner peripheral surface of the through hole, the glass substrate 1 is likely to be damaged starting from here, and thus countermeasures against the crack are strongly demanded.

  Further, according to the drilling method of Patent Document 2, the occurrence of cracks is reduced to some extent by reducing the runout of the drill. However, when the lower drill is retracted, the maximum diameter portion is runout and the inner circumference of the hole In order to come into contact with the surface, there may still be a defect crack.

  Furthermore, since the inner peripheral surfaces of the through holes drilled by these conventional methods are all perpendicular to the plate surface of the glass substrate, the edge portions of the through holes become sharp and weak in strength, It has a considerable adverse effect on glass substrate breakage.

  The present invention has been made in view of the above. By drilling with a drill having a specific shape, the grinding surface can be prevented from coming into contact with the inner peripheral surface of the through-hole when the drill is retracted. It aims at providing the drilling method of the glass plate which can prevent generation | occurrence | production of this.

  The present invention is directed to glass using a pair of drills whose grinding surface is reduced in diameter toward the tip in consideration of drill runout when drilling through holes in a glass plate and allowable accuracy of the through holes. The object is achieved by perforating from both sides of the plate. Specifically, the present invention uses a pair of drills having a conical circumferential surface whose diameter is reduced toward the tip of the grinding surface of the side circumferential part of the drill, and the drill is inserted from one surface of the glass plate. After drilling, retreat, and then drill another drill from the other side of the glass plate into the opposite part of the perforation, grind it to the middle in the thickness direction of the glass plate and then retract to form a through hole in the glass plate By doing so, even if there is a runout in the drill, the ground surface does not substantially contact the inner peripheral surface of the through-hole when the drill is retracted, and there is a risk that the glass plate may be damaged, that is, a defective crack. The upper frustoconical diameter of the inner peripheral surface of the through hole is reduced from the upper surface (front surface) of the glass plate toward the middle portion in the thickness direction of the glass plate, and the lower surface (rear surface) of the glass plate. ) To the middle of the thickness direction of the glass plate It is possible to obtain a glass plate, which is formed by the conical circumferential surface of the lower truncated cone whose diameter decreases toward the.

That is, this invention provides the glass plate which has the following perforation, and the drilling method of a glass plate.
(1) A glass plate having at least one through hole, wherein the inner peripheral surface of the through hole is reduced in diameter from the upper surface of the glass plate toward an intermediate portion in the thickness direction of the glass plate and glass A glass plate having perforations, characterized in that it is formed by each conical circumferential surface of a lower truncated cone that decreases in diameter from the lower surface of the plate toward an intermediate portion in the thickness direction of the glass plate.
(2) When the inclination angle with respect to the through-hole central axis of the conical circumferential surface of the upper truncated cone is θ1, and the inclination angle with respect to the through-hole central axis of the conical circumferential surface of the lower truncated cone is θ2, θ1 and θ2 are 2 The glass plate according to (1) above, which is 5 degrees and θ1 and θ2 are substantially the same.
(3) The glass plate according to (1) or (2), wherein H1> H2, where H1 is the height of the lower truncated cone and H2 is the height of the upper truncated cone.
(4) The said glass plate is a glass plate as described in said (1), (2) or (3) which is a glass substrate for flat display panels.
(5) Use a pair of drills having a conical circumferential surface whose diameter is reduced toward the tip of the grinding surface on the side circumferential part of the drill, and the inner circumferential surface is a glass plate by allowing the drill to enter from one surface of the glass plate. After drilling a conical circumferential surface whose diameter is reduced from the plate surface toward the middle in the thickness direction of the glass plate, it is retracted, and then another drill enters the opposite portion of the hole from the other surface of the glass plate. The perforation of the conical peripheral surface whose inner peripheral surface is reduced in diameter from the plate surface of the glass plate toward the intermediate portion in the thickness direction of the glass plate is made to recede after being drilled to approximately the middle of the thickness of the glass plate. A method of drilling a glass plate, characterized in that a through hole is drilled in the glass plate.
(6) The method for punching a glass plate according to (5), wherein an inclination angle θ of the conical circumferential surface of the drill with respect to a drill center axis is 2 to 5 degrees.

  According to the present invention, the through-holes are drilled from both sides of the glass plate using a pair of drills having a conical circumferential surface whose diameter is reduced toward the tip portion at the side circumferential portion of the drill. Even if the drill has a runout, it can be avoided that the grinding surface of the drill comes into contact with the inner peripheral surface of the through hole. As a result, when a through hole is made in a glass plate with a conventional drill, when the drill that has entered is retracted, the drill mainly comes into contact with the inner peripheral surface of the through hole in which the drill has been drilled due to runout of the drill. It is possible to eliminate as many cracks as possible, and it is possible to make a through-hole in the glass plate that does not have a crack that causes damage to the glass plate on the inner peripheral surface.

  Further, the inner peripheral surface of the through hole is reduced in diameter from the upper surface of the glass plate toward the central portion in the thickness direction of the glass plate and from the lower surface of the glass plate toward the central portion of the glass plate. Since it is formed by each conical circumferential surface of the lower truncated cone, the edge portion of the through hole where the glass plate surface and the inner circumferential surface of the through hole intersect is obtuse and the strength of the glass plate of the through hole portion is reduced. Can be improved.

  In addition, since the inner peripheral surface of the through-hole is an inclined surface that decreases in diameter from the glass plate surface toward the center of the glass plate thickness method, the presence or absence of cracks on the inner peripheral surface and the state of occurrence are externally It becomes easy to see and inspection becomes easy.

The front view of the drill which concerns on preferable embodiment of this invention. (A)-(E) are cross-sectional explanatory drawing which shows the punching process in the drilling method of the glass plate which concerns on embodiment of this invention. Cross-sectional explanatory drawing of the through-hole part of the glass plate obtained by this invention. Cross-sectional explanatory drawing of the through-hole part of the other glass plate obtained by this invention. Cross-sectional explanatory drawing which shows the drilling method of the conventional glass plate. The top view which shows an example which manufactures a display panel using a glass substrate.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  In the drilling method of the present invention, a pair of drills are used to punch a glass plate. The pair of drills have the same basic configuration and operation as drills, and usually have the same shape. Hereinafter, one of the pair of drills is an upper drill and the other is a lower drill, and only the upper drill is representatively described in detail, and illustration and description of the lower drill are omitted.

  FIG. 1 is a front view of an upper drill according to a preferred embodiment used in the present invention. The upper drill 7 is mounted on a holder 11, and although not shown, the holder 11 is provided with a drive unit for rotating the upper drill 7 and a sliding unit for moving the upper drill 7 up and down. ing. In this upper drill 7, a side peripheral portion 8, which is formed entirely as a conical peripheral surface, is smoothly and continuously formed at the tip end portion 9, and the side peripheral portion 8 is reduced in diameter toward the tip end portion 9. It has a tapered shape. Although the front-end | tip part 9 of this example is flat, it is not limited to this, For example, convex shape may be sufficient.

  As the upper drill 7, it is possible to preferably use a diamond main body sintered by electrodeposition or metal bond on the surface of a metal main body in the same manner as a conventional drill. In this case, the diamond abrasive grains are usually present on the entire surface of the side peripheral portion 8 including the tip portion 9 of the upper drill 7, but it is sufficient that the side peripheral portion 8 exists at least in a portion used for drilling. That is, when the upper drill 7 is drilled into the glass plate, the tip 9 of the upper drill 7 is brought into contact with the upper surface of the glass plate and further penetrated, and the inner peripheral surface of the drill is ground to the predetermined depth by the side peripheral portion 8. Since the upper drill 7 is retracted from the glass plate, it is only necessary that the diamond abrasive grains exist in the side peripheral portion 8 that contacts the glass plate when the upper drill 7 penetrates the deepest and a region slightly above it. It is.

  In the present invention, the upper drill 7 is reduced in diameter toward the tip end portion 9 as described above, and the side peripheral portion 8 is formed by a conical peripheral surface. Therefore, as shown in FIG. With an inclination angle θ. As a matter of course, at least a portion of the side peripheral portion 8 of the upper drill 7 used for drilling is inclined in this way, and does not have a cylindrical portion having the same drill diameter as in a conventional drill. The inclination angle θ is appropriately determined depending on the size of the drill core runout, the thickness of the glass plate, the accuracy allowed for the through hole of the glass plate, the diameter of the through hole, and the like. 5 degrees is preferable and 2.5 to 4 degrees is more preferable. If θ is smaller than 2 degrees, it cannot cope with the core run-out of a general-purpose drill, and therefore, when the drill is retracted, the side peripheral portion may come into contact with the inner peripheral surface of the through hole and cracks may occur. If θ is larger than 5 degrees, it is difficult to satisfy the accuracy generally accepted in the through hole of the glass plate, and it is sufficient for drill runout even if it does not have an inclination angle larger than this. Correspondingly, the object of the present invention can be achieved.

  In the present invention, it is preferable that the upper drill and the lower drill are substantially the same from the viewpoints of ease of drilling operation and drilling workability. Therefore, the inclination angle of the side periphery of the lower drill is generally designed to be the same as the inclination angle of the upper drill, but if the drill can be drilled within the allowable accuracy of the through hole, the inclination angle of the side periphery of the lower drill May not exactly match the tilt angle of the upper drill.

  Further, it is preferable that the side circumferential portion 8 is provided with a concave groove 10 in the same direction as or substantially in the same direction as the drill axis Y as shown in FIG. The concave groove 10 allows the cutting fluid to smoothly reach the cutting portion of the glass plate when drilling with the upper drill 7, suppresses heating, discharges glass waste generated by the cutting, and efficiently forms the through hole. It is effective to drill well. The number of the concave grooves 10 provided in the side peripheral portion 8 is preferably about 1 to 3, and the shape and size thereof are appropriately determined.

  Next, a procedure method for drilling a through hole in the glass plate 1 using the upper drill 7 and the lower drill 7 'will be described with reference to FIG.

  First, as shown in FIG. 2A, an upper drill 7 and a lower drill 7 'having the same shape are arranged above and below the glass plate 1 with their drill axes aligned, or the drill axes are aligned. The positions where the through holes of the glass plate 1 are to be drilled are fixed to the positions of the upper drill 7 and the lower drill 7 'arranged in this manner. Next, the lower drill 7 'is lifted and brought into contact with the lower surface of the glass plate 1 and is drilled by penetrating the glass plate 1 while supplying the cutting fluid. The drilling of the lower drill 7' reaches a predetermined depth. At that time, the lower drill 7 'stops rising and is retracted. (B) shows a state where the drilling of the lower drill 7 'has reached a predetermined depth, and (C) shows a state where the lower drill 7' is retracted. By retreating the lower drill 7 ', a hole 2a having the same shape as the lower drill 7' is obtained in the glass plate 1.

  In the above, even if there is a runout that normally occurs when the lower drill 7 'is retracted, no trouble cracks due to the lower drill 7' occur on the inner peripheral surface of the hole 2a. That is, as described above, the lower drill 7 'has a tapered shape that decreases in diameter toward the tip, and the side peripheral surface thereof has an inclination angle θ with respect to the drill shaft, so that the lower drill 7' is retracted. At the same time, the lower drill 7 'is separated from the inner peripheral surface of the hole 2a. As a result, contact between the ground surface of the lower drill 7 'and the inner peripheral surface of the hole 2a is avoided, and the risk that the ground surface of the lower drill 7' gives cracks to the inner peripheral surface of the hole 2a is eliminated.

  Next, as shown in (D), the upper drill 7 is lowered and penetrated while supplying cutting fluid from the upper surface of the glass plate 1, and the side peripheral surface of the upper drill 7 is formed by the lower drill 7 '. When the inner peripheral surface of the drilled hole 2a intersects with a substantially middle portion in the thickness direction of the glass plate 1, the lowering of the upper drill 7 is stopped and retracted. (E) is a state in which the upper drill 7 is retracted, and a through hole 2 is formed in the glass plate 1. Further, no trouble cracks are generated on the inner peripheral surface of the through hole 2 formed by the upper drill 7 for the same reason as the lower drill 7 '. Thus, the through-hole 2 can be drilled in the glass plate 1 with the upper drill 7 and the lower drill 7 ', and the through-hole 2 having no cracks that may cause damage to the glass plate 1 is drilled in the inner peripheral surface. Can be set.

  In this example, the lower drill 7 ′ is first penetrated from the lower surface of the glass plate 1 to make the hole 2 a, and then the upper drill 7 is made to penetrate from the upper surface of the glass plate 1 to make the through hole 2. The procedure is reversed, first the upper drill 7 is inserted from the upper surface of the glass plate 1 and the hole 2a is formed on the upper side of the glass plate 1, and then the lower drill 7 'is inserted from the lower surface of the glass plate 1 to penetrate the hole. 2 may be drilled.

  Further, the upper drill 7 and the lower drill 7 '(hereinafter sometimes collectively referred to as a drill) have a tapered shape whose diameter is reduced toward the tip portion, and the side peripheral portion thereof has a predetermined inclination angle. Therefore, the diameter of the through hole 2 can be changed depending on the penetration length of these drills into the glass plate 1. Specifically, the diameter of the through hole 2 becomes larger as the drill enters the glass plate 1 longer. Therefore, how much the drill penetrates into the glass plate 1 at the time of drilling is made to penetrate to a position where the same drill diameter as the diameter of the through hole 2 can be obtained based on the diameter of the tip of the drill and the inclination angle of the side periphery. Just do it. Further, in this example, the tip portion of the drill does not protrude from the glass plate 1 during drilling (non-penetrating state). However, when the drill penetration length is increased, the tip portion of the drill is the glass plate 1. It may be in a state of protruding from (penetration state).

  Further, when a plurality of through holes are formed in the glass plate 1, a plurality of through holes can be formed simultaneously by arranging the drills in accordance with the positions of the respective through holes. As a result, a plurality of exhaust holes for exhaust and gas filling in the display panel manufacturing process can be drilled in a large glass substrate for a flat display panel according to the number of display panels to be collected (see FIG. 6). .

  Next, the through hole obtained by the drilling method of the present invention will be described. FIG. 3 is a sectional view schematically showing the through hole 2 formed in the glass plate 1 by the drilling method of the present invention. As shown in the figure, the through-hole 2 has a glass plate from the upper truncated cone 3 whose inner peripheral surface is reduced in diameter from the upper surface of the glass plate 1 toward the middle portion in the thickness direction of the glass plate and from the lower surface of the glass plate 1 The glass plate 1 is formed by the respective conical circumferential surfaces of the lower truncated cone 4 whose diameter is reduced toward the middle portion in the thickness direction, and the minimum diameter portion of the through hole 2 is joined to the upper truncated cone 3 and the lower truncated cone 4. It is in the shape of a thin film located in the middle part of the thickness direction. Needless to say, the portion corresponding to the upper truncated cone 3 of the through-hole 2 is formed by the upper drill, and the portion corresponding to the lower truncated cone 4 is formed by the lower drill.

  Therefore, the conical circumferential surfaces of the upper truncated cone 3 and the lower truncated cone 4 are inclined with respect to the central axis X of the through hole 2. Here, when the inclination angle with respect to the central axis X of the conical circumferential surface 5 of the upper truncated cone 3 is θ1, and the inclination angle with respect to the central axis X of the conical circumferential surface 6 of the lower truncated cone 4 is θ2, θ1 and θ2 are Each corresponds to the inclination angle of the side periphery of the upper drill and the inclination angle of the side periphery of the lower drill, preferably 2 to 5 degrees, more preferably 2.5 to 4 degrees. If θ1 and θ2 are within this range, they can be within the accuracy range allowed for the through hole. The obstructions θ1 and θ2 are the same if a pair of drills having the same shape are used, but need not be exactly the same and may be substantially the same.

  When the height of the lower truncated cone 4 is H1, and the height of the upper truncated cone 3 is H2, H1 and H2 may be the same or different. If the glass substrate warps on the upper surface side where surface treatment is applied during the flat panel manufacturing process, such as a glass substrate for a flat panel display, thermal stress is generated more on the lower surface side than on the upper surface side of the glass substrate. Therefore, it is preferable that the joint portion between the lower truncated cone 4 and the upper truncated cone 3 is on the upper surface side where the thermal stress is relatively small. It is not preferable that the joint is located on the lower surface side where a large thermal stress is generated or approaches the lower surface side because breakage tends to occur. That is, it is preferable that H1> H2. In this case, if the ratio of H1 to H2 becomes too large, the difference between the maximum diameter and the minimum diameter of the through hole exceeds the allowable range, so the ratio of H1 to H2 is adjusted within the allowable range. The adjustment of the ratio of H1 and H2 can be performed by changing the ratio of the penetration length of the upper drill and the lower drill, and the height of the larger penetration length can be increased.

  FIG. 4 is a cross-sectional view schematically showing another through-hole 2 obtained by the drilling method of the present invention. The basic shape of the through-hole 2 is the same as that of the above-described through-hole shown in FIG. 3 differs from the through hole of FIG. 3 in which the inner peripheral surface is not curved toward the shaft side in that the inner peripheral surface of the through hole 2 is slightly curved toward the shaft side in the central axis X direction of the through hole. Such a through-hole 2 can be obtained by curving the side peripheral surface of the drill slightly concavely toward the shaft side in the direction of the drill shaft.

  Note that the inclination angles θ1 and θ2 in the case where the inner peripheral surface of the through hole is curved in this way are the two ends of the curved peripheral surfaces of the upper truncated cone 3 and the lower truncated cone 4 as shown in FIG. The angle between the connecting straight line and the central axis X of the through hole 2 can be determined.

  As described above, the glass plate of the present invention is very slight even if there is a run-out of the drill when the glass plate is drilled, because the drill when retreating does not contact the inner peripheral surface of the through-hole or even when contacted. Therefore, no trouble cracks are generated on the inner peripheral surface of the through hole. In addition, since the edge of the through hole where the inner peripheral surface of the through hole intersects the glass plate surface becomes obtuse, not only the strength of the edge increases, but also the drill during retraction may be damaged by touching the edge. Improved.

  Therefore, the glass plate of the present invention is preferable as a glass substrate for a flat display panel in which damage from the through-hole portion is a concern. When the glass plate of the present invention is used as a glass substrate for a flat display panel, since the inner peripheral surface of the through hole does not have a defective crack, the through hole is the starting point in the heat treatment process when manufacturing the display panel. It is possible to prevent the glass substrate from being damaged. However, the drilling method of the present invention can also be applied to glass plates other than glass substrates for flat display panels.

  With the drilling method of the present invention and the conventional drilling method shown in FIG. 5, through-holes were drilled in each of 20 PDP glass substrates (thickness: 1.8 mm, vertical dimension: 150 mm, horizontal dimension: 150 mm). The cracks on the inner peripheral surface of the through hole were observed and compared with a stereomicroscope.

  In the embodiment of the present invention, the same drill shown in FIG. 1 is used for the upper drill and the lower drill, the drill diameter at the tip of both drills is 1.8 mm, and the inclination angles θ1 and θ2 of the side peripheral surface of the drill are 3 degrees. First, drilling is performed from the lower surface of the glass substrate so that the rotation speed of the drill is 20000 rpm, the penetration speed of the drill is 0.15 mm / sec, and H1 is 1.2 mm and H2 is 0.6 mm. The opposing portion was perforated from the upper surface, and a through-hole having a diameter of 2 mm on the lower surface portion and diameter-reducing from the upper and lower surfaces of the glass substrate toward the middle portion in the thickness direction was formed in 20 glass substrates.

  On the other hand, in the conventional drilling method, the cylindrical drill shown in FIG. 5 having the same drill diameter in the drill axial direction is used for the upper drill and the lower drill, the drill diameter of both drills is 2 mm, and the number of rotations of the drill is set. A through hole having a diameter of 2 mm was drilled in 20 glass substrates at 20000 rpm and a drill penetration speed of 0.15 mm / sec.

  Next, as a result of observing the inner peripheral surface of the through hole of each glass substrate with a stereomicroscope and investigating the occurrence of cracks, cracks having a depth of less than 2 μm were recognized in the through hole by the drilling method of the present invention. However, a crack having a depth of 40 μm or more, which might cause breakage of the glass substrate, was not observed in any of the 20 glass substrates.

  On the other hand, in the through holes drilled by the conventional drilling method, cracks deeper than the cracks of the through holes in the examples of the present invention are generally recognized, and the glass substrate may be damaged, and the depth is 40 μm. The above cracks were observed on 16 of the 20 sheets.

  INDUSTRIAL APPLICABILITY The present invention is suitable for drilling a through-hole that does not have a defective crack on the inner peripheral surface with a drill, and can be used particularly for drilling an exhaust hole in a glass substrate for a flat display panel.

1: Glass plate 2: Through hole 3: Upper truncated cone 4: Lower truncated cone 5: Conical circumferential surface 6: Conical circumferential surface 7: Drill 8: Side circumferential portion 9: Tip portion 10: Groove 11: Holder 12a: No. 1 drill 12b: second drill 13: exhaust hole

Claims (6)

  A glass plate having at least one through-hole, wherein the inner peripheral surface of the through-hole is reduced in diameter from the upper surface of the glass plate toward the middle portion in the thickness direction of the glass plate, and the lower surface of the glass plate The glass plate is characterized by being formed by each conical circumferential surface of the lower truncated cone that is reduced in diameter toward an intermediate portion in the thickness direction of the glass plate.   When the inclination angle of the upper circular truncated cone with respect to the through hole central axis is θ1, and the inclined angle of the lower circular truncated cone with respect to the through hole central axis is θ2, θ1 and θ2 are 2 to 5 degrees. The glass plate according to claim 1, wherein θ1 and θ2 are substantially the same.   The glass plate according to claim 1 or 2, wherein H1> H2, where H1 is a height of the lower truncated cone and H2 is a height of the upper truncated cone.   The glass plate according to claim 1, 2, or 3, wherein the glass plate is a glass substrate for a flat panel display.   Use a pair of drills having a conical circumferential surface whose diameter is reduced toward the tip, and the inner circumferential surface is the plate surface of the glass plate. After drilling a conical circumferential surface whose diameter is reduced toward the middle part of the thickness method of the glass plate, it is retracted, and then another drill is penetrated from the other surface of the glass plate into the opposite part of the perforation. The perforation of the conical peripheral surface whose diameter decreases from the plate surface of the glass plate toward the middle portion in the thickness direction of the glass plate is drilled to approximately the middle of the thickness of the glass plate and then retracted to penetrate the glass plate. A method of drilling a glass plate, wherein   6. The method for punching a glass plate according to claim 5, wherein an inclination angle [theta] of the conical circumferential surface of the drill with respect to a drill central axis is 2 to 5 degrees.

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