JP2007145625A - Method for processing glass plate by laser beam irradiation - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for processing the end part of a glass plate by laser beam irradiation, which does not necessitate a large-scale device and uses a simple means. <P>SOLUTION: In the method for processing the end face part of the glass plate, comprising softening at least the corner part of the end part of the glass plate by heat generated by laser beam irradiation and then solidifying the softened part, the end face part of the glass plate is irradiated with a laser beam having a beam width larger than the thickness of the glass plate from an oblique direction with respect to the surface of the glass plate under such conditions that the end face part is irradiated with the highest intensity part of the laser beam and the laser beam satisfies following formulas: Power*sinθ*speed<SP>-1</SP>>50 (1) and 160> Power*cosθ*speed<SP>-1</SP>>260 (2), wherein, Power represents intensity (W/cm<SP>2</SP>) of laser beam; θ is irradiation angle (°) of the laser beam to the end face part of the glass plate; and speed is working speed (mm/s) in a process for scanning the laser beam along the end face part of the glass plate. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a technique for improving the strength of a glass end by heating, softening, and solidifying the portion by irradiating a laser beam to the end of the glass.

  The strength of the glass plate depends on the presence of defects such as scratches and cracks at the ends, and depending on the state of this defect, the strength of the glass plate is significantly reduced. Thus, in order to improve the strength of the glass plate, in order to reduce defects on the glass plate end surface portion, the edge portion is processed, and as the processing method, a polishing process using a grinding wheel or the like is generally performed. It has been broken. And the method of heating, softening, and solidifying the end portion by laser light irradiation has been studied as a method that may further improve the strength of the end portion because there is no generation of polishing scraps.

In Patent Document 1, a material that absorbs laser light is applied to a ridge line portion of a glass substrate, a laser beam of a YAG laser is applied to the glass edge portion, the edge line portion is heated, softened, and then solidified. A technique for processing into an R shape is disclosed. Further, in Patent Document 2, the end portion is heated to a temperature higher than the preheating temperature by softening and solidifying the end portion by irradiating the end portion with a laser beam of CO ₂ laser in a state where the entire glass is preheated. It is disclosed that a part is chamfered. Furthermore, in Patent Document 3, the rounded shape of the end portion is obtained by changing the irradiation angle of the laser light from the CO ₂ laser to the end surface portion of the glass plate while keeping the glass plate horizontal. Various changes are disclosed.

And in patent document 4, in order to prevent the thermal crack resulting from the extreme temperature gradient generation | occurrence | production by the local heating which arises by laser irradiation, it is glass by irradiating the laser beam of the intensity | strength which does not process (soften) glass to a process part A technique is disclosed in which preheating is performed, and then the processing site is processed by local heating by laser irradiation.
Japanese Patent Laid-Open No. 2-48423 JP-A-2-241684 JP 2000-344551 A JP 2000-288863 A

  When processing a glass plate by irradiating a laser beam, the irradiated portion is locally heated, so that an extreme temperature gradient is generated, which is a major cause of thermal cracking of the glass plate. Therefore, in patent document 2, the whole glass plate is preheated by means, such as a heating furnace, and in patent document 4, glass is preheated by the laser beam.

  However, in order to preheat the entire glass, the entire apparatus becomes large. And since the glass slow cooling process is also required, it is necessary to reduce productivity or cope with further increase in equipment, leading to a significant increase in cost. Further, even with preheating by laser light, there is a problem in that a heat retention means for maintaining the preheating is required and the apparatus becomes large, and productivity is lowered due to one additional processing step.

  Therefore, in view of the above points, an object of the present invention is to provide a method for processing a glass end surface portion by laser light irradiation with simple means without requiring a large-scale apparatus.

  That is, the glass plate processing method of the present invention is a glass end face processing method in which at least a corner of a glass plate end is softened by heating by laser light irradiation, and then the softened portion is cooled to solidify. A laser beam having a beam width larger than the thickness of the glass plate is irradiated from an oblique direction with respect to the plate surface so that the intensity peak portion of the laser beam is applied to the end surface portion of the glass plate. ] And [2] are satisfied so as to satisfy the condition.

Power ・ sinθ ・ speed ^-1 > 50 [1]
160> Power ・ cosθ ・ speed ^-1 > 260 [2]
Here, Power is the intensity of the laser beam (W / cm ² ), θ is an irradiation angle (°) of the laser beam to the end surface of the glass plate, and the angle is explained in FIG. The speed is a processing speed (mm / s) for scanning the laser beam along the end surface of the glass plate. The softened portion can be sufficiently cooled by natural cooling.

  In the present invention, when the heating condition of the glass plate and the thermal cracking condition of the glass plate were examined, the position of 10 mm in the vertical direction in the plane of the glass plate from the softened portion of the glass plate end surface portion (this position is illustrated in FIG. And the temperature of the glass plate is within 330 ° C. from the glass transition temperature.

  In the present invention, on the basis of the above knowledge, in order to prevent the glass plate from cracking even under processing at room temperature or by processing with a single laser beam, a laser applied to the end surface of the glass plate is used. It has been found that a method of irradiating laser light obliquely with respect to the glass plate surface is promising during light irradiation.

  By irradiating a laser beam having a beam width larger than the glass plate thickness from an oblique direction with respect to the glass plate surface so that the intensity peak portion of the laser beam is applied to the glass plate end surface portion, the glass plate end surface portion is softened. And the surface is heated to such an extent that it does not soften. And by satisfy | filling the said [1] type | formula and [2] type | formula as the irradiation conditions of the laser beam to a glass plate end surface part, it is room temperature environment thru | or 0-50 degreeC, without requiring preheating apparatuses, such as a heating furnace. The glass plate end face can be processed with a laser beam in a temperature atmosphere close to room temperature or in a room temperature environment of 0 to 35 ° C.

  Only by adjusting the irradiation angle of the laser light, it becomes possible to perform the end face processing of the glass without causing thermal cracking of the glass. Therefore, a preheating device such as a heating furnace, which has been conventionally required, can be omitted, and it is possible to reduce the cost of manufacturing a glass substrate whose strength is improved by end face processing.

  The glass plate end surface processing method of the present invention is a glass end surface portion processing method in which at least a corner portion of the glass end portion is softened by heating by laser light irradiation, and then the softened portion is cooled to be solidified. This is done by adjusting the irradiation angle of the laser beam to the plate end surface.

  As a laser for processing the glass plate, a carbon dioxide laser, a YAG laser, or the like is used, and a carbon dioxide laser that emits a beam having a wavelength of 10.6 μm, which is an absorption wavelength of glass, is preferably used. In order to alleviate the thermal gradient between the softened portion of the glass end surface and the glass plate surface portion during processing of the glass plate end surface, the present invention irradiates the end surface including the corner of the glass with the beam and simultaneously also irradiates the peripheral portion of the glass surface Therefore, the beam diameter is preferably larger than the glass plate thickness. Therefore, the diameter of the beam is preferably set to 1 to 20 of the glass plate thickness at the time when the glass plate is irradiated.

  The upper limit of the beam diameter depends on the beam profile of the laser beam used, the optical system, etc., but is preferably within 10 times the glass plate thickness. The lower limit of the beam diameter is preferably 1.5 times or more, and preferably 2 times or more.

  In general, the intensity distribution of the laser beam is often a Gaussian distribution. However, in order to easily adjust the laser intensity distribution on the glass plate end face and inside the surface, laser light having a top hat intensity distribution is used. It is preferred to use.

  And the glass plate processing method of the present invention uses float glass, alkali-free glass, quartz glass, high strain point glass used in PDP, and the like. And it is preferable to use the glass plate of the thickness of 1-5 mm for the thickness of the glass applied from the point of processing efficiency.

The conditions of the irradiation angle of the laser beam with respect to the glass plate end surface are such that the power · sin θ · speed ⁻¹ value is 50 or more. Here, Power is the intensity of the laser beam (W / cm ² ), θ is the irradiation angle (°) of the laser beam to the glass plate end surface, and speed is the processing speed (mm) that scans the laser beam along the glass plate end surface. / s). If this value is 50 or more, the glass plate can be satisfactorily processed without breaking during processing, but if it is less than 50, a large thermal stress is generated due to a large temperature gradient generated on the irradiated glass plate end surface and inside the surface. Breaking of the glass plate occurs during processing.

Further, irradiation is performed so that the value of power · cos θ · speed ⁻¹ becomes 160 to 260. When this value is 160 to 260, the shape of the end surface of the glass plate after beam irradiation is a substantially uniform arc. When the value is 160 or less, the shape of the end face of the glass plate is hardly changed and remains angular, and when it is 260 or more, the glass plate is too melted to have a non-uniform end face shape.

  The processing method of the glass of this invention is demonstrated using drawing. FIG. 1 is a cross-sectional view showing a state during glass processing by laser irradiation. The atmosphere temperature when processing is normal temperature and normal pressure. The laser beam B is irradiated to the glass G so as to be inclined with respect to the glass end surface so as to have at least one corner. Then, the glass is scrolled with the laser beam B fixed, or the laser beam B is scanned with the glass fixed to process the glass end face.

Example 1
A CO ₂ laser is irradiated under the conditions shown in Table 1 on the end face of a 300 mm × 300 mm × 2.8 mm (thickness) glass plate made of soda-lime silicate glass having a glass transition temperature of 630 ° C. obtained by the float process. Then, the glass plate end face was processed. The processing was performed in a room temperature atmosphere of 25 ° C.

  When the temperature distribution of the glass plate during irradiation was measured with an infrared radiation thermometer, the temperature at a position 10 mm in the vertical direction from the portion where the end surface of the glass plate was softened was 224 ° C. lower than the glass transition temperature.

  When the shape of the end surface portion of the obtained glass plate was observed, it was a substantially uniform arc-shaped end surface. Further, this end face part was subjected to a four-point bending test in accordance with JIS R 1601 “Fine ceramic bending strength test method”. The breaking load showed a very high value of about 30 kgf on average compared to about 10 kgf on average for conventional polished end face products. Moreover, when the destruction condition was confirmed, they were all destruction from the inside of a glass surface, without destroying from an end surface part. From this, it is considered that the strength of the end face portion of the glass plate processed in this example shows a value higher than that.

Example 2
Processing was performed under the same conditions as in Example 1 except that the conditions described in Table 1 were used. At this time, the temperature at a position 10 mm in the vertical direction from the softened portion of the end surface portion of the glass plate was 330 ° C. lower than the glass transition temperature. When the shape of the end surface portion of the obtained glass plate was observed, it was a substantially uniform arc-shaped end surface, and the strength was the same as in Example 1.

Example 3
Processing was performed under the same conditions as in Example 1 except that the conditions described in Table 1 were used. At this time, the temperature at a position 10 mm in the vertical direction from the softened portion of the end surface of the glass plate was 273 ° C. lower than the glass transition temperature. When the shape of the end surface portion of the obtained glass plate was observed, it was a substantially uniform arc-shaped end surface, and the strength was the same as in Example 1.

Comparative Example 1
Processing was performed under the same conditions as in Example 1 except that the conditions described in Table 1 were used. At this time, the temperature at a position 10 mm in the vertical direction from the softened portion of the end face of the glass plate was 201 ° C. lower than the glass transition temperature. When the shape of the obtained glass plate end surface portion was observed, it was a distorted shape that melted too much and swollen into the surface of the glass plate.

Comparative Example 2
Processing was performed under the same conditions as in Example 1 except that the conditions described in Table 1 were used. At this time, the temperature at a position 10 mm in the vertical direction from the softened portion of the glass plate end face was 364 ° C. lower than the glass transition temperature. When the shape of the end surface portion of the obtained glass plate was observed, it was hardly melted and had an angular shape. Further, although no destruction occurred during the processing, it broke after about 1 hour.

Comparative Example 3
Processing was performed under the same conditions as in Example 1 except that the conditions described in Table 1 were used. At this time, the temperature at a position 10 mm in the vertical direction from the softened portion of the end surface of the glass plate was 426 ° C. lower than the glass transition temperature, but the glass plate was broken during processing.

It is sectional drawing showing the state at the time of the glass processing by laser irradiation. It is a figure which shows the position of 10 mm in the orthogonal | vertical direction in the surface of a glass plate from the softened site | part of a glass plate end surface part.

Explanation of symbols

G Glass B Laser light applied to the glass end face 1 Softened part 2 Position of 10 mm in the vertical direction in the plane of the glass plate from the softened part of the glass plate end face part

Claims (2)

In the processing method of the glass end face part that softens at least the corner part of the glass plate end by heating by laser light irradiation and then solidifies the softened part, a beam larger than the glass plate thickness from an oblique direction with respect to the glass plate surface A laser beam having a width is irradiated so that the intensity peak portion of the laser beam is applied to the end surface portion of the glass plate, and in this irradiation, the laser beam is applied so that the conditions of the equations [1] and [2] are satisfied. The processing method of the glass plate end surface part characterized by being performed.
Power ・ sinθ ・ speed ^-1 > 50 [1]
160> Power ・ cosθ ・ speed ^-1 > 260 [2]
Here, Power is the intensity of the laser beam (W / cm ² ), θ is the irradiation angle (°) of the laser beam to the glass plate end surface, and speed is the processing speed (mm) that scans the laser beam along the glass plate end surface. / s). The manufacturing method of the glass substrate which has the end surface processing process by the processing method of the glass plate end surface part of Claim 1.

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