JP2006137169A - Method and apparatus for breaking and cutting fragile material - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To realize ideal breaking and cutting by preventing the disturbance caused by the disturbance of heat conduction occurring in the end part of a fragile material, in breaking and cutting the fragile material such as glass or the like by forming a scribe surface to the surface layer of the fragile material using the heat stress brought about by the heating due to the irradiation with a laser beam or the cooling due to the spraying of a cooling liquid and subsequently breaking the fragile material by the application of mechanical stress. <P>SOLUTION: The irradiation with the laser beam or the spraying of the cooling liquid is prevented by a mask in the end part of the fragile material not avoiding the disturbance of the scribe surface to stop the occurrence of a laser scribe surface. A break surface after scribing approaches an ideal state in a case free from a disturbed part as compared with a case that a disturbed scribe surface is present and the breaking and cutting of high quality of the fragile material can be realized. By performing the breaking and cutting of the fragile material, the enhancement of the quality dispensing with a post process of the broken and cut surface can be realized coupled with the excellent characteristics of laser scribing. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a brittle material, especially a method for cleaving brittle materials such as glass, and an apparatus for the same. In the present specification, description is made especially for glass, but in addition to glass, it can be applied to brittle materials such as quartz, ceramic, and semiconductor in general.

  Conventionally, brittle materials have been cut by a mechanical method using a carbide tool such as a diamond tip. The application of this method to glass is also a method that has been used for a long time over the past century.

  However, such mechanical methods have the following drawbacks. The first is that small pieces called cullet are generated at the time of cutting, and the work surface is soiled. Secondly, there is a risk that a microcrack is generated in the vicinity of the cut surface and the workpiece is cracked starting from the microcrack. Third, there is a cutting margin of about several hundred microns at the minimum, and the existence of this cutting margin cannot be ignored at present when the workpiece size is miniaturized without limit. In addition to this, there are other disadvantages that cannot be ignored in the industry, such as the limit of processing speed and the cost of tools that are consumables.

  Cutting of window glass, etc. is not a problem with the prior art, but in the case of fine glass cutting used for liquid crystal display, plasma display, etc., after cutting, etc. after polishing the cut surface to prevent micro cracks A process is required.

  On the other hand, laser cleaving has the following characteristics. First, the mass loss is zero (no cullet generation), and no post-process such as cleaning is required. Second, since a high-strength cross section is obtained without the occurrence of fracture defects such as microcracks in the vicinity of the split cross section, a post-process such as polishing is unnecessary. Third, a mirror surface having a surface roughness of 1 μm or less is obtained. Fourth, the product outline accuracy is ± 25 μm or less. Fifth, it can be used for glass plates with a thickness of up to 0.2 mm and can be used for future liquid crystal TVs.

When glass is irradiated with a high energy density CO ₂ laser beam, the laser beam is generally absorbed at the irradiation spot, and as a result of rapid heating, radial cracks are generated, and cutting proceeds only in the traveling direction. I can't do that. However, if the energy density of the laser beam is set to be sufficiently lower than that which generates such cracks, the glass is only heated and neither melting nor cracking occurs. At this time, the glass tends to thermally expand, but it cannot expand due to local heating, and compressive stress is generated around the irradiation point. This local heating source is moved in the direction in which it is desired to cleave. When cooling is performed by spraying a cooling liquid after heating, a tensile tension is generated on the contrary. As shown in FIG. 1, when the cross-sectional shape of the laser beam is formed into an appropriate one, tensile tension is generated only in the direction perpendicular to the light moving direction. In the figure, 1 is a heating laser beam, 2 is a compressive stress inside the glass, 3 is a cooling liquid, and 4 is a tensile tension inside the glass. The cleavage crack 5 is generated by the action of the tensile tension. In the glass plate 6, if the trigger crack 8 is attached to the starting point by a mechanical method, the cleaving crack 5 is generated from the trigger crack and can be advanced along the moving direction 7 of the laser beam. In order for such a phenomenon to occur ideally, the energy distribution of the irradiated laser beam needs to be optimal in order to generate such tension. These optimal distributions have been studied in various glass cuttings. The heating laser beam 1 shown in FIG. 1 has been optimized.

The following patent application has been filed for a method for realizing such an optimal distribution.
Patent application number 2003-363855
Patent application number 2004-156891
This laser application for glass cleaving is indispensable in the processing of fine glass in general, for which demand will increase rapidly.

In the thermal stress cleaving of the glass by the CO ₂ laser beam irradiation, the CO ₂ laser beam is absorbed only by the glass surface layer as shown in FIG. The depth of cleaving with laser (referred to as laser scribe) is usually about 100 μm. In the figure, 9 is a laser scribe surface. In order to make the surface deeper than this, a temperature change in the deep part must be generated by heat conduction in the depth direction. In this case, the processing speed is remarkably reduced, so it is not usually performed. The mechanical scribe surface shown in FIG. 3 is also usually of a similar depth. Now, since glass is very brittle, it is easy to mechanically break it in accordance with this scribe line. This process is called a break.

  Conventionally, glass is broken by a combination of mechanical scribe and break. In the case of mechanical scribing, as shown in FIG. 3, since there are a large number of microcracks near the scribe surface, the break is relatively easy. However, as shown in FIG. 12, the break surface after mechanical scribing does not necessarily constitute one plane orthogonal to the glass surface. In order to remove the microcrack layer and improve the accuracy of the break surface, in the case of mechanical scribe, the fractured surface is polished and cleaned after the break.

  On the other hand, in the case of laser scribing, there are no microcracks in the vicinity of the scribe surface, so the break surface is ideal as shown at 10 in FIG. In that case, polishing cleaning can be omitted. However, when the cut surfaces rub against each other, cullet is generated or scratches are generated. As a break technique for preventing these problems, the inventor has developed a method shown in FIG. 4, for example. Here, the rotational stress around the rotation center axis 13 located below the glass plate 6 from the laser scribe surface 9 is applied to the glass plate in the direction of the rotational stress application direction 14 using the rotational stress application device 15, and the laser A break is generated by simultaneously bending and tearing the scribe surface. In this case, since the bearing portion 16 and the glass holding portion 17 of the apparatus are eccentric, the break surfaces after laser scribing do not contact each other, and cullet and scratches do not occur.

  However, laser scribing also has drawbacks. As shown in the laser scribe principle diagram of FIG. 1, the cross-sectional shape of the heating laser beam 1 must be optimized, and the tensile tension 4 generated in the glass after cooling must be perpendicular to the cleaving direction. This shape optimization is based on the premise that heat is conducted in all directions from the heat source on the surface of the glass plate 6. This is correct except at the edge of the glass plate, but heat conduction does not occur in the outer direction of the glass at the edge, so the direction of the tensile tension inside the glass is disturbed, and the scribe line is bent. When the glass plate containing the bent laser scribe line is broken as described above, the break surface 10 after the laser scribe as shown in FIG. It will come off from 19. In this case, the merit of high accuracy peculiar to the laser scribe at the corner is lost.

  The cause of the problem is that laser scribe uses a thermal phenomenon, so that the disturbance of the phenomenon is inevitable at the end of the material where the heat conduction characteristics change, so the laser scribe is stopped just before the end of the material. I will let you. In this case, a part of the laser scribe line is missing, but the linearity of the scribe line can be maintained. On the other hand, when the mechanical break described above is performed, it has been empirically found that the break surface is ideal as shown by 19 in FIG. 5 even if a part of the laser scribe line is missing.

According to the present invention, it is possible to always perform glass cleaving comprising both laser scribe and break processes under optimum conditions. Glass cleaving with a laser has the following technical advantages.
1) Cutting position accuracy is high.
2) The cut surface is a mirror surface and the surface roughness is good.
3) Split section inclination is highly accurate.
4) There is no adhesion of cullet on the cut surface and it is clean.
5) Both scribe and break can be automated.
6) Both scribe and break can be performed at high speed.
7) Subsequent processes such as polishing and cleaning can be omitted.

  Thus, laser laser breaking is a significant advance over conventional mechanical methods such as using a diamond cutter. If glass cleaving by laser becomes widespread, there are things that cannot be measured in terms of processing speed, processing quality, economy, and overcoming difficulty.

  By preventing the laser scribe generation condition at the end of the material where the laser scribe line bends, the progress of the laser scribe line can be stopped. Breaking may be performed by applying mechanical stress while the scribe line is absent, and the material may be cleaved.

  FIG. 6 shows a method for carrying out the present invention. The glass surface is covered with a mask in the vicinity of the end face 20 of the glass plate 6. In the figure, 1 is a heating laser beam, and 3 is a coolant. Both move together along the moving direction 7 of the laser beam. The heating laser beam has a special beam shape as shown in FIG. In combination with the cooling means, it generates a tensile tension on the glass surface in a direction perpendicular to the moving direction of the laser beam. Therefore, a laser scribe surface 5 is formed inside the glass.

  In the vicinity of the glass end surface, a mask 21 covers the glass. As a result, the glass is under a mask at an appropriate distance from the end surface, for example, about 0.5 mm. The mask 21 is placed on the mask base 22. The mask base 22 is in thermal contact with the glass end surface, and helps the heat conduction in the glass to occur in the vicinity of the end surface as well as in the glass.

When the mask has a high reflectance with respect to the heating laser beam, the heating laser beam is reflected by the mask and the glass is not heated. Since a CO ₂ laser beam is used as the laser beam, a mask whose surface is coated with gold may be used.

  The present invention can also be realized by blocking the coolant. In this case, the mask 21 may be made of a heat insulating material. In this case, the generation of tensile tension due to cooling is suppressed.

  You may block both a heating laser beam and a cooling liquid with a mask. Further, the coolant block may be supplied by a valve opening / closing operation instead of using a mask.

  The laser scribe surface disappears when the mask approaches the glass end surface.

  If there is a curved laser scribe surface as described above, the break after the laser scribe also bends. However, if there is no laser scribe surface at the position to be bent, if a mechanical break is applied, the break surface will lack the laser scribe surface. Linearity can be maintained as long as the length of the portion is about 0.5 mm.

  Since heat transfer changes occur at all material edges, scribing disturbances should occur not only at the end face but also at the start face. However, the reason why only the countermeasure on the end face is emphasized in the present invention is that, on the starting face, the laser scribe starts from the trigger crack 8 provided at the upper part of the same face and proceeds in a straight line with sufficient accuracy. . What has been described above is a few examples of mechanisms for realizing the functions of the present invention, and it goes without saying that the spirit of the present invention can be realized in many other ways.

  Cutting flat glass used for flat panel displays such as liquid crystal displays and plasma displays, mobile and car navigation displays, and IR filters for optical devices is currently performed with a diamond cutter, and the need for a cleaning process after cutting. And the presence of microcracks. Laser cleaving can solve these problems. The present invention can also be applied to processing of microchips such as an IC chip cover glass. Since the cutting length is longer than in the case of a large workpiece, the effect of the present invention is great.

  Since glass parts for automobiles are often curved, they are now mechanically cut after linear cutting. For this reason, there is a great expectation for laser processing that requires only glass cleaving.

  Furthermore, the processing of tempered glass as a building material can contribute to the solution of the problem demanded by modern society for crime prevention. Cutting of tempered glass is difficult by a mechanical method, and use of a laser is expected.

  Thus, the advent of laser technology for improving glass breaking is a solution to various problems demanded by modern society.

Laser stress scribe principle diagram by laser. Glass laser scribe. Glass mechanical scribe. Mechanical break method. Laser scribing at the glass edge and breakage of the break surface after laser scribing. Examples of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Thermal laser beam 2 Compressive stress inside glass 3 Coolant 4 Tensile tension inside glass 5 Cleavage crack occurring in glass 6 Glass plate 7 Moving direction of laser beam 8 Trigger crack 9 Laser scribe surface 10 Break surface 11 after laser scribe Scribe surface 12 Break surface after mechanical scribing 13 Rotation center shaft 14 Rotational stress application direction 15 Rotational stress application device 16 Bearing portion 17 Glass holding portion 18 Disrupted break surface end portion 19 Ideal break surface end portion 20 Glass end surface 21 Mask 22 Mask base

Claims (5)

    By using laser beam irradiation that precedes movement and subsequent cooling means, a crack (laser scribe) caused by thermal stress is generated in the surface layer of brittle materials such as glass, quartz, ceramics, and semiconductors. A brittle material cleaving device that breaks along the entire thickness direction of the material by applying stress, which is mechanical means, and is characterized by stopping laser scribe generation on the material surface just before the end of the material.     2. The method for stopping cracks according to claim 1, wherein a mask for blocking laser light is provided at the end of the brittle material.     The method for stopping cracks according to claim 1, wherein a mask for blocking the coolant is provided at the brittle material terminal portion.     3. The method according to claim 1, wherein the crack stopping method is a combination of claim 2 and claim 3.     2. The method according to claim 1, wherein the supply of the coolant is stopped near the end of the brittle material as a method for stopping the crack.

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