JP2009084133A - Full body cleaving method of brittle material - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a full body cleaving method capable of a high speed cleaving, generating no stripe pattern on the cleaved surface, realizing a thermal stress cleaving high in speed and quality and having high smoothness, also capable of freely controlling the position of cleaving line and the cleaving speed. <P>SOLUTION: The full body cleaving is performed along a predetermined cleaving position, by forming a strip-like heating part 12 by preliminarily heating the predetermined cleaving position of a glass substrate 11 with a surface heat source, giving tensile stresses 13, 14 and 15 generated by thermal stress to the predetermined cleaving position to maintain the predetermined cleaving position in the state of just before cleaving, then scanning a local heat source by laser to the predetermined cleaving position of the strip-like heating part 12 in the scanning direction 22, that is, scanning laser beam from a laser heating part 18 to the predetermined cleaving position to add a tensile stress 19. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

The present invention relates to a full-body cleaving method for a brittle material, in particular, a flat-body display glass for full-body cleaving. Hereinafter, glass will be described as an example of the brittle material, but the present invention can be applied to brittle materials such as quartz, ceramics, and semiconductors in addition to glass.

Recently, in the glass cleaving, a thermal stress cleaving method by laser light irradiation (hereinafter abbreviated as a laser cleaving method) has been used in place of the diamond chip mechanical method that has been used for the past century.

  According to the laser cleaving method, defects inherent in the mechanical method, that is, a decrease in glass strength due to the occurrence of microcracks, contamination due to the occurrence of cullet during cleaving, the presence of a lower limit value of the applied plate thickness, etc. can be eliminated.

According to this laser cleaving method, polishing and cleaning, which are subsequent steps of mechanical cleaving, are not required, a mirror surface having a surface roughness of 1 μm or less is obtained, and the product external dimension accuracy is ± 25 μm or more. Furthermore, it can be used for glass substrates with a thickness of up to 0.1 mm, and can be used for future glass for liquid crystal displays.

  The principle of the laser cleaving method is as follows. Laser irradiation is performed to such an extent that only heating occurs locally on the glass and vaporization, melting and cracking do not occur. At this time, the glass heating section tries to expand thermally, but cannot sufficiently expand due to the reaction from the surrounding glass, and compressive stress is generated around the irradiation point. Even in the peripheral non-heated region, the peripheral portion is further distorted by the expansion from the heating portion, and as a result, compressive stress is generated. These compressive stresses are radial. By the way, when the object has a compressive stress, a tensile stress related to the Poisson's ratio is generated in the orthogonal direction. Here, the direction is a tangential direction. This is shown in FIG.

FIG. 1 shows changes in the radial stress component σ _x and the tangential stress component σ _y when there is a temperature increase in the Gaussian distribution centered at the origin. The radial stress component σ _x is a compressive stress (negative value in FIG. 1) from beginning to end, while the tangential stress component σ _y is a compressive stress at the heating center (distance r = 0), but tensile stress when it is away from the heating center. (Positive value in FIG. 1).

Among these stresses, the tensile stress is related to the cleaving. When the tensile stress exceeds the fracture toughness value that is a material specific value, fracture occurs everywhere and is uncontrollable. In the case of the laser cleaving method, the tensile stress is selected below this fracture toughness value, so no fracture occurs.

However, when there is a crack at the position where the tensile stress is present, stress expansion occurs at the tip of the crack, and the crack expands when the stress intensity factor due to this stress exceeds the fracture toughness value of the material. That is, controlled cleaving occurs. Therefore, the crack can be extended by scanning the laser irradiation point. In this laser cleaving method, since the fractured surface is similar to the cleavage plane of the crystal, there is no generation of microcracks or cullet, the disadvantages of the mechanical method described above can be eliminated, and excellent properties as a glass processing method It is what you have.

This glass laser cleaving method was first developed by Kondratenko, and the Japanese Patent of Patent Document 1 was established.
Japanese Patent No. 3027768 FIG. 2A shows the principle of the laser cleaving method according to Patent Document 1. FIG. As the laser light, CO2 laser light is used, and 99% of the energy in the beam spot 1 of the CO2 laser light is absorbed in the glass surface layer having a depth of 3.7 μm of the glass substrate 2 and is spread over the entire thickness of the glass substrate 2. Not transparent. This is due to the extremely large absorption coefficient of glass at the CO2 laser wavelength. The depth of the cleaving by the laser (hereinafter referred to as scribe) is usually about 100 μm even if assisted by the heat conduction 4 in the glass substrate 2. However, the glass substrate 2 is highly brittle and can be easily cleaved mechanically by applying stress in accordance with the scribe line. The process of breaking all by application of the mechanical stress is called “break”. The laser beam is scanned in the cleaving direction 3. Although this method has advantages compared to the conventional mechanical method, its practicality is limited to the necessity of a break, and its diffusion has not necessarily been perfect.

  On the other hand, when the laser beam 5 is irradiated such that it passes through the glass substrate 2 as shown in FIG. 2B and is partially absorbed, the transmitted light is less than the total thickness of the glass substrate 2. Since the cleaving 6 is generated, the glass substrate 2 can be cleaved only in this step, and a break is unnecessary. This cleaving is called full-body cleaving (or all cleaving) by laser.

By adopting full body cleaving, in addition to the technical features of the laser cleaving method described above, breaks are unnecessary and work inversion is not required, free curve cleaving is possible, selective from one direction of laminated glass Benefits unique to full-body cleaving, such as the ability to cleave, have made it possible to realize incredible improvements in the flat panel manufacturing process. Remi Co., Ltd. has proposed Patent Documents 2 to 8 for this full-body cleaving technology.
JP 2006-256944 A JP 2006-347793 A JP 2007-55072 A JP 2007-76077 A Japanese Patent Application No. 2006-089949 Japanese Patent Application No. 2006-311379 Japanese Patent Application No. 2006-348836

In addition, a nichrome wire with tension is brought into contact with the strip that has scratches (initial cracks) formed on the end face of the glass substrate and heated, and the crack progresses along the nichrome wire from the position of the scratch. Non-Patent Document 1 proposes a glass cleaving technique using a linear heat source that has been cleaved to increase the cleaving speed. The principle of glass breaking by this linear heat source will be described with reference to FIG.
In FIG. 3, the horizontal axis indicates the position x in the length direction normalized with respect to the length L of the glass substrate, and the vertical axis indicates the fracture toughness value K1c when the nichrome wire is energized to heat the glass substrate linearly. The normalized stress intensity factor K1 is shown. Therefore, the fracture toughness value K1c is at the position 1 on the vertical axis. The stress intensity factor K1S of scratches (hereinafter referred to as initial cracks) formed on the end face of the glass substrate is smaller than the fracture toughness value K1c. When the nichrome wire is further energized from this state and the glass substrate is heated in a linear shape, the stress intensity factor K1 further increases from the curve A and K1s reaches 1, and the length of the glass substrate from the position of the initial crack. The stress intensity factor K1 is larger than the fracture toughness value K1c until the position x / L in the direction is close to 0.8, and the cleaving proceeds at a high speed from the initial crack to the position x / L near 0.8. In the part where the position x / L exceeds about 0.8, the speed decreases, but the cleaving proceeds at the high speed from the initial crack to the position x / L near 0.8, and the edge of the glass substrate progresses. And the cleaving is finished.
Journal of Precision Engineering Vol. 66, no. 7, 2000, pages 1135 to 1139

As described above, the cleaving according to Patent Document 1 requires a break process and cannot be full-body, so that its practicality is limited.
Although the full body by laser proposed in Patent Documents 2 to 8 is an excellent technique, there is a drawback that the cleaving speed does not increase beyond a certain limit value. The reason why the cleaving speed is limited is that laser beam irradiation for generating thermal stress and cleaving by crack expansion are simultaneously performed as one process. Originally, the crack propagation speed in the glass should be close to the speed of sound as well as the propagation speed of stress. However, in actuality, the scanning speed of laser light irradiation for generating thermal stress must be based on the optimal scanning speed of laser light for generating thermal stress that causes laser cleaving. Is usually about 10-100 mm / s in the case of non-alkali glass having a thickness of 0.7 mm. This is due to the fact that the heat source by laser light is a local heat source. In other words, in order to fully body a brittle material, the tensile stress, which is the thermal stress generated by the heat source, must be greater than the resistance force of the brittle material, but the resistance force of the brittle material acts on an area basis. This is because the moving speed of the local heat source must be reduced to make the stress larger than the resistance force due to this area.

On the other hand, the glass cleaving technique using the linear heat source proposed in Non-Patent Document 1 can increase the cleaving speed, but the speed of the crack cannot be controlled because the progress of the crack proceeds at a stretch at a stretch. As the crack progresses, a striped pattern is generated and the smoothness tends to be impaired. This tendency becomes more remarkable as the progress rate of cracks increases. Further, since the tip of the crack cannot be controlled to an arbitrary position, the position of the breaking line cannot be controlled.

The present invention solves these problems of the prior art, and eliminates the disadvantage that the cleaving speed in the full-body cleaving technology by laser does not increase beyond a certain limit value, thereby realizing high-speed thermal stress cleaving. The object is to provide a full body cleaving method.
Another object of the present invention is to provide a full-body cleaving method capable of controlling the cleaving speed freely and realizing a thermal stress cleaving having no striped pattern and having high smoothness even in high-speed cleaving. It is for the purpose.
Still another object of the present invention is to provide a full-body breaking method capable of freely controlling the position of the breaking line while freely controlling the position of the breaking line, while being able to freely control the position of the breaking line. It is.

In order to achieve the above object, the present invention preliminarily heats the cutting position of the brittle material with a surface heat source, maintains the cutting position in a state immediately before the cutting, and supplies the local heat source at the preheated cutting position. The full body is cleaved along the planned cleaving position. Specifically, the following configuration is provided.
In the first configuration, the pre-cleaving position of the brittle material is preheated by a surface heat source, a tensile stress due to thermal stress is applied to the fracturing position of the brittle material, and the pre-heating cleaving is maintained. It is characterized in that full body cleaving is performed while scanning the local heat source at the planned position to increase the tensile stress and controlling along the planned cleaving position.
The second configuration is characterized in that, in the first configuration, the speed of full body cleaving is controlled by the scanning speed of the local heat source.
The third configuration is characterized in that, in the first configuration, the position of the breaking line in the full body breaking is controlled by the scanning position of the local heat source.
The fourth configuration is characterized in that, in the first configuration, the timing for starting full body cleaving is controlled by the timing of starting scanning of the local heat source.
The fifth configuration is characterized in that, in the first configuration, an initial crack is formed at an end portion of the brittle material at a planned cutting position.
The sixth configuration is characterized in that in the first configuration, the surface heat source is a far-infrared lamp arranged on one main surface of the brittle material so as to be spaced apart.
The seventh configuration is characterized in that, in the first configuration, the surface heat source is a belt-like heat source disposed on or in contact with one main surface of the brittle material.
The eighth configuration is characterized in that, in the first configuration, the local heat source is a laser beam.
The ninth configuration is characterized in that, in the first configuration, the local heat source is due to dielectric loss based on a high-frequency voltage applied between electrodes brought into contact with the front and back surfaces of the brittle material.
The tenth configuration is characterized in that, in the first configuration, the local heat source is a micro heat source using a nichrome wire or a solder iron.

According to the present invention, the full-body thermal stress cleaving that can greatly increase the cleaving speed compared with the full-body cleaving by the laser while having the high quality of the cleaving section that the full-body cleaving technology by the laser has. Can be realized.
Further, even in high-speed cleaving, there is no striped pattern on the cut surface, and full-body thermal stress cleaving having high smoothness can be realized.

Specific advantages of the present invention include the following.
(1) Full-body cleaving of brittle materials can be performed at a significantly higher speed than conventional methods.
(2) The brittle material can be cleaved in a single process with full body cleaving, and no break is required. In addition, post-processing such as polishing and cleaning is unnecessary.
(3) There is no generation of microcracks in the vicinity of the fractured surface, and the mechanical strength of the workpiece is high.
(4) There is no adhesion of cullet on the cut surface and it is clean.
(5) Curve cutting is possible.
(6) The cleaving position accuracy is high.
(7) The fractured surface is sufficiently perpendicular to the glass surface.
(8) The fractured surface is a mirror surface and the surface roughness is good.
(9) The selective cleaving of the laminated glass can be performed by laser beam irradiation from one direction, and an operation such as inversion of the glass substrate is unnecessary.
(10) The cleaving can be automated.

As described above, if the high-speed full-body thermal stress cleaving according to the present invention is introduced into the flat panel display manufacturing process, the effect is important in improving the processing speed, processing quality, economy, etc., and overcoming the weaknesses of the prior art. There is something unknown.

The full-body cleaving method for a brittle material according to the first embodiment of the present invention is to preheat the cleaving position of the brittle material with a surface heat source and keep the brittle material at the cleaving position of the brittle material in a state immediately before cleaving. The local heat source is scanned at the planned cutting position, and the full body is cut along the planned cutting position. According to the present embodiment, it is possible to greatly increase the cutting speed as compared with the conventional full body cleaving using a laser while having high quality of the fractured surface of the full body cleaving technique using a laser. Further, even in high-speed cleaving, there is no striped pattern on the cut surface, and full-body thermal stress cleaving having high smoothness can be realized.
The second embodiment of the present invention is characterized in that in the full-body cleaving method for brittle material according to the first embodiment, the speed of full-body cleaving is controlled by the scanning speed of the local heat source. According to the present embodiment, the speed of full body cleaving can be freely controlled by controlling the scanning speed of the local heat source.
The third embodiment of the present invention controls the position of the breaking line in the full body cleaving by the scanning position of the local heat source in the brittle material full body cleaving method according to the first embodiment. According to the present embodiment, the position of the full-body cleaving line can be freely controlled by controlling the scanning position of the local heat source.
The fourth embodiment of the present invention controls the timing for starting full body cleaving according to the scanning start timing of the local heat source in the brittle material full body cleaving method according to the first embodiment. According to the present embodiment, the timing for starting full body cleaving can be freely controlled by the scanning start timing of the local heat source.
The fifth embodiment of the present invention is to form an initial crack at the end portion of the brittle material where the brittle material is to be cut in the full body cleaving method of the brittle material according to the first embodiment. According to the present embodiment, it is possible to accurately set the position at which cleaving is started.
According to a sixth embodiment of the present invention, in the full-body cleaving method for a brittle material according to the first embodiment, a surface heat source is configured by a far infrared lamp arranged separately on one main surface of the brittle material. Is. According to the present embodiment, a thermal stress source for cleaving a brittle material can be realized with a small-scale and simple and inexpensive configuration.
According to a seventh embodiment of the present invention, in the full body cleaving method for a brittle material according to the first embodiment, the surface heat source is a belt-like heat source disposed on or in contact with one main surface of the brittle material. Is. According to the present embodiment, a thermal stress source for cleaving a brittle material can be realized with a small-scale and simple and inexpensive configuration.
The eighth embodiment of the present invention uses a laser beam as a local heat source in the full body cleaving method for a brittle material according to the first embodiment. According to the present embodiment, the size, shape, position, temperature distribution, etc. of the local heat source can be precisely controlled.
The ninth embodiment of the present invention is a dielectric loss based on a high-frequency voltage applied between electrodes in which a local heat source is brought into contact with the front and back surfaces of the brittle material in the full body cleaving method of the brittle material according to the first embodiment. It is realized by. According to the present embodiment, scanning of the local heat source can be performed at high speed.
In the tenth embodiment of the present invention, in the full body cleaving method for brittle material according to the first embodiment, the local heat source is a micro heat source using nichrome wire or soldering iron. According to the present embodiment, the local heat source can be realized with a simple configuration.

Hereinafter, it will be described in detail with reference to the drawings.
First, the principle of the present invention will be described. In the present invention, the pre-cleaving position of the brittle material is pre-heated with a surface heat source using a linear heat source or a belt-like heat source, and a tensile stress due to thermal stress is applied to the fracturing position of the brittle material to maintain the state immediately before cleaving. Next, heating is performed while moving a local heat source by laser beam irradiation or the like to a pre-cleaved scheduled cutting position. The brittle material that was in the state immediately before cleaving starts to cleave by heating the cleaving planned position by the local heat source. This will be described with reference to FIG.

4A and 4B are plan views showing a state where a brittle material substrate such as a glass substrate is heated in a linear or belt shape, where FIG. 4A shows a state in which thermal stress is generated, and FIG. Indicates a cleaved state. In addition, since strip | belt shape is the state which expanded the linear width | variety, in description of this invention in this specification, and these claims, these are collectively named "band | belt shape".
When the belt-shaped heating part 12 is formed by bringing a belt-shaped heating member such as a nichrome wire into contact with a substantially central position of the glass substrate 11 as shown in FIG. 4A, the glass substrate 11 tends to expand around the belt-shaped heating part 12. A force acts, and the force to expand is a tensile stress 13, 14, 15 along the length direction in the width direction of the belt-shaped heating unit 12, and the length direction at both ends of the glass substrate 11 in the length direction. It acts as stretching force 16 and 17 extending in the direction. On the other hand, since the force to expand like the belt-like heating unit 12 does not act on the unheated region around the belt-like heating unit 12 of the glass substrate 11, the belt-like heating unit 12 expands in this unheated region. Even if it does not expand, the substrate warps in a bow shape and tensile stresses 13, 14, and 15 are generated. After actually being cleaved as shown in FIG. The tensile stresses 13, 14, and 15 are greatest when the area of the heated portion is as large as the area of the non-overheated portion. That is, it is desirable to perform area heating in which the area of the heated portion is heated to the same level as the area of the non-heated portion.

When the heating temperature by the belt-like heating unit 12 is not sufficiently high, the glass substrate 11 is not cleaved because the stress intensity factors due to the tensile stresses 13, 14, and 15 acting on the glass substrate 11 are smaller than the fracture toughness value. In this state, when the heating temperature by the belt-like heating unit 12 becomes sufficiently high, the stress intensity factor due to the tensile stresses 13, 14, and 15 at the initial crack 18 position of the belt-like heating unit 12 becomes larger than the fracture toughness value. As a result, the crack progresses from the initial crack 18, and the glass substrate 11 is cleaved full body along the belt-like heating unit 12 as shown in FIG. Since this full-body cleaving is usually broken from the side having the initial crack 18, only the one side of the glass substrate 11 is cleaved. At this time, since the belt-like heating unit 12 is expanded, the full body is cut so as to bend up and down like the bimetal. Although the drawings are written with emphasis, the actual deformation cannot be seen with the naked eye because of changes on the micron order.

In the present invention, the glass substrate 11 is in the state shown in FIG. 4A, that is, in a heated state in which the stress intensity factor due to the tensile stresses 13, 14, 15 acting on the glass substrate 11 is smaller than the fracture toughness value (hereinafter referred to as this). The state is referred to as preheating), and the state immediately before cleaving is maintained. In this state, the belt-shaped heating unit 12 is moved and scanned while being heated by a local heat source such as laser light. This is shown in FIG.
FIG. 5 is a plan view showing a state when a local heat source is scanned in a state in which the brittle material substrate in the embodiment of the present invention is preheated in a strip shape. In FIG. 5, the same parts as those in FIG. The heating by the laser heating unit 18 is superimposed on the preliminary heating by the belt-shaped heating unit 12, and the stress intensity factor generated by adding the tensile tension 19 by the heating by the laser heating unit 18 to the tensile stresses 13, 14, 15 by the belt-shaped heating unit 12. Becomes larger than the fracture toughness value, and the glass substrate 11 is cleaved full-body. When the laser heating unit 18 scans the strip heating unit 12 in the direction of the arrow 22 from the initial crack 21 formed at one end of the strip heating unit 12 of the glass substrate 11, the glass substrate 11 follows the scanning of the laser heating unit 18. The breaking line proceeds in the direction of arrow 22. That is, the full body cutting of the glass substrate 11 is performed by superimposing the surface heat source heating in the preheating and the scanning of the local heat source by the laser beam irradiation.

The breaking line does not advance ahead of the laser heating unit 18 in the direction of travel. The reason for this will be described with reference to FIG. The laser heating unit 18 is subjected to compressive stress in addition to the tensile stress 19 due to thermal stress. When the glass substrate 11 is heated by the laser heating unit 18, compressive stresses 25 and 26 act from the periphery of the laser heating unit 18 toward the laser heating unit 18. As a result, the front end 28 of the breaking line 27 is blocked by the compressive stresses 25 and 26 of the laser heating unit 18 and stops near the rear end 29 in the direction of travel of the laser heating unit 18. As a result, the position of the tip 28 of the breaking line 27 can be freely controlled by the position of the laser heating unit 18. In addition, since the tip 28 of the breaking line 27 follows the movement of the laser heating unit 18, the moving speed of the tip 28 of the breaking line 27 can be freely controlled by the moving speed of the laser heating unit 18. Further, since the position of the breaking line 27 is also determined by the position of the laser heating unit 18, the position of the breaking line can be controlled.

Next, the basic principle of the present invention will be described in more detail using a stress intensity factor. FIG. 7 is a graph for explaining the principle of operation of the present invention using a stress intensity factor. 7A and 7B, the horizontal axis represents the position x / L in the length direction normalized with respect to the length L of the glass substrate 11, and the vertical axis represents the fracture toughness value K1c of the glass substrate 11. The normalized stress intensity factor K1 is shown.
FIG. 7A shows the distribution of the stress intensity factor K1 in a state where only the laser beam from the laser heating unit 18 is irradiated to the position of x / L = 0.2 without performing the band-shaped preheating on the glass substrate 11. FIG. . At the position x / L = 0.2 where the laser beam is irradiated, a compressive stress is applied and there is no stress intensity factor K1.

In the present invention, the laser beam from the laser heating unit 18 is not used for directly cleaving the thermal stress on the glass substrate 11, but is used for the start of cleaving, the position control of cleaving, and the speed control of cleaving. Good. Therefore, the stress intensity factor K1 is smaller than the fracture toughness value K1c over almost the entire length with respect to the length L of the glass substrate 11. In the vicinity of the laser beam, the stress intensity factor K1 is slightly increased. In the vicinity of x / L = 0.25 to 0.27 on the leading edge side, the stress intensity factor K1 is slightly larger than the fracture toughness value K1c. Is possible. However, if the glass substrate 11 is cleaved using the state of the stress intensity factor K1> fracture toughness value K1c at this position, the cleaved line is bent and proceeds, so that it cannot be used in practice. In the present invention, the peak 32 near x / L = 0.15, which is the trailing edge side of the laser beam, is used. However, as described above, the laser beam is not used for directly cleaving the thermal stress on the glass substrate 11 but is used for cleaving start, cleaving position control, and cleaving speed control.

When the laser beam is scanned in the direction of increasing the position x / L in the length direction of the glass substrate 11, the peak 32 near x / L = 0.15 on the trailing edge side of the laser beam follows the scanning of the laser beam. Then, the glass substrate 11 is scanned in the direction of increasing x / L. That is, since the position of the peak 32 moves depending on the position of the laser beam, the position can be controlled by the guide of the laser beam. Therefore, the tip position and the dividing speed of the breaking line of the glass substrate according to the present invention described later can be controlled by the scanning position and the scanning speed of the laser beam.

FIG. 7B shows a state in which the glass substrate 11 is only subjected to strip-shaped preheating. As described above, since the preheated state is the state immediately before cleaving, the stress intensity factor K1 is set to be smaller than the fracture toughness value K1c. K1S is the stress intensity factor of the initial crack, and 34 is the position of the initial crack.

In the present invention, first. A state in which only the preheating is performed around the planned cutting line of the glass substrate 11, that is, the state shown in FIG. 7B, and the laser beam from the laser heating unit 18 shown in FIG. Then, the laser beam is scanned along the planned cutting line at the preheated position. FIG. 8A shows a state in which the laser beam explained in FIG. 7A is superimposed on the preheated glass substrate 11 explained in FIG. 7B. The laser beam is irradiated so that the peak 32 on the trailing edge side of the laser beam described in FIG. 7A corresponds to the position 34 of the initial crack 33. The curve of the stress intensity factor K1 at this time is a curve obtained by adding the stress intensity factor K1 in FIG. 7A and the stress intensity factor K1 in FIG. In this state, the cleaving of the glass substrate 11 is started by the laser beam irradiation, and the stress intensity factor K1 at the initial crack position 34 of the glass substrate 11 by the laser beam irradiation is a peak 32 on the trailing edge side of the laser beam. At the position, the fracture toughness value K1c becomes larger, and the glass substrate 11 starts to be cleaved from the initial crack 33. The tip of the cleaving line 35 due to this cleaving stops at a position 36 where the stress intensity factor K1 is smaller than the fracture toughness value K1c. The position 36 where the cleaving stops corresponds to the trailing edge side in the traveling direction of the laser beam, and as described with reference to FIG. 6, the tip of the cleaving line stops near the trailing edge in the traveling direction of the laser beam.

When the laser beam is scanned in the direction of increasing x / L of the glass substrate 11, the breaking line 35 is a laser as shown in FIGS. 8B, 8C, 8D, and 8E. When the laser beam advances following the position and speed of the beam and the laser beam exceeds the end of the glass substrate 11, the stress intensity factor K1 becomes smaller than the fracture toughness value K1c, and the breaking line 35 is formed as shown in FIG. The tip temporarily stops when the position x / L is around 0.9. If the preheating state is continued in this state, the breaking line 35 is slowed down due to the inertia of the breaking force until then, but the breaking continues, that is, the end of the glass substrate 11, that is, x / L. = 1 is reached, and the glass substrate 11 is completely cleaved.
Specific examples of the present invention will be described below.

FIG. 9 is a conceptual perspective view of a cleaving apparatus for carrying out a full-body cleaving method for a brittle material in the first embodiment of the present invention. The glass substrate 11 is placed on a stage 41 movable in the direction of arrow A. A surface heat source 43 such as a far-infrared lamp is disposed above the glass substrate 11. The surface heat source 43 heats a region including the planned cutting line 45 of the glass substrate 11 to form a preheating region 44. In the preheating region 44, the surface heat source 43 and the glass substrate 11 are separated from each other, so that the heating temperature distribution of the surface heat source 43 can have a distribution shape in which a high temperature is formed in a band shape. it can. An initial crack 46 is formed in an extension of the planned cutting line 45 at the end of the glass substrate 11.

The initial position of the stage 41 is set such that the laser beam 48 from the laser light source 47 irradiates the position of the initial crack 46 on the planned cutting line 45 of the glass substrate 11. In this state, the laser light source 47 irradiates the planned cutting line 45 of the glass substrate 11 with the laser beam 48. Irradiation with the laser beam 48 acts as a local heat source. When the stage 41 is moved in the direction of the arrow A in this state, the laser beam 48 scans the planned cutting line 45 of the glass substrate 11, and the glass substrate 11 is cut at full speed at a high speed by the above-described cutting principle. That is, the full body cleaving of the glass substrate 11 is performed by superimposing the surface heat source heating by the preheating and the scanning of the local heat source by the laser beam irradiation. In addition, even if this superimposition is not exactly the same time, the local heat source may be scanned before the temperature rise due to heating of the surface heat source is reduced by cooling. At this time, the tip of the breaking line moves according to the moving speed of the stage 41, and the position is controlled by the position of the laser beam 48 as described above. The scanning of the laser beam 48 may be performed by scanning the laser beam 48 from the laser light source 47 in addition to the movement of the stage 41 in the arrow A direction.
Since the laser beam from the laser device used as the laser light source is not used for directly cleaving the glass substrate 11, a laser device with a small power may be used. Specifically, a CO ₂ laser, a CO laser, a YAG laser, a semiconductor laser, or the like can be used. The laser beam can precisely control the size and shape of the local heat source, the temperature distribution, and the like.

Next, specific cleaving conditions for cleaving the glass substrate 11 with the configuration of Example 1 shown in FIG. 9 will be described. As the glass substrate 11, a Yb-added non-alkali glass substrate having a thickness of 0.7 mm, a width of 580 mm, and a length of 510 mm is used, a semiconductor laser having an output of 1 kW and a wavelength of 976 mm is used as a laser light source 47 as a local heat source, and a laser beam 48 Was condensed to a width of 0.5 mm and a length of 2.5 mm on the surface of the glass substrate 11. The surface heat source 43 for preheating uses an infrared heater having a length of 950 mm and an output of 1 kW. This is set at a position 200 mm above the cleaving position in the center of the width of the glass substrate 11 and irradiated at room temperature of 25 ° C. for 3 minutes. The temperature of the central portion of the glass substrate 11 rose to 70 degrees C. The temperature distribution had the highest cleaving position at the center of the width, the shape was a mountain shape, the full width at half maximum was about 200 mm, and it was uniform in the length direction, and the end in the width direction of the glass substrate 11 was hardly different from room temperature. Such a wide strip heating condition was most effective. Under these conditions, there is no problem even with a workpiece that cannot be heated to a high temperature, such as a glass substrate for a liquid crystal display, at a temperature as low as 70 ° C. even at the highest temperature portion. After the substrate was preheated, it was cleaved by irradiation with a laser beam 48 from the end where the initial crack 46 was formed. The cleaving speed reaches 250 mm / s, and the cleaving speed when cleaving under the condition where the conventional preheating shown in FIG. 10 is not performed is 5 times faster than when the cleaving speed does not reach 50 mm / s. It can be seen that the effect is very high. This cleaving speed can be further increased by adjusting the cleaving conditions.

According to the present embodiment, since preheating can be performed by a far infrared lamp, the configuration of the apparatus is simple and inexpensive, and a linear heat source such as a nichrome wire is brought into contact with the glass substrate as in Non-Patent Document 1. Since it is not necessary, handling is easy and work efficiency is also good.
Since the glass substrate 11 is held in a state immediately before cleaving by preheating, even if the initial crack 45 is not formed, if the laser beam 48 as a local heat source is sufficiently strong, the microcrack can be naturally generated only by irradiation. The cleaving can be started from the end portion of the glass substrate 11 containing. Therefore, the initial crack 45 is not always necessary.

FIG. 11 shows a second embodiment of the present invention. In this embodiment, a high frequency voltage e is applied from the power source 53 between the electrodes 51 and 52 brought into contact with the front and back surfaces of the glass substrate 11 without using a laser device as a local heat source, and dielectric generated in the glass substrate 11. The glass substrate 11 is locally heated by heat generated by the loss. In FIG. 11, 54 schematically shows the capacitance of the glass substrate 11, and 55 schematically shows the dielectric loss of the glass substrate 11. Other configurations and operations are the same as those in FIG.
FIG. 11 is a cross-sectional view at a certain position, but when the electrodes 51 and 52 are made into a number of divided electrodes and the voltage applied to each of them is sequentially changed, the cutting line 41 can be cut along without moving the stage 41. In this case, a higher speed can be realized than in the case of laser light irradiation.

Example 3 uses a micro heat source such as a nichrome wire or a solder iron as a local heat source. Other configurations and operations are the same as those in FIG.

FIG. 12 shows an embodiment in which a nichrome wire 49 is used in place of the far-infrared lamp in the first embodiment as the surface heat source 42 for preheating. One or a plurality of nichrome wires 49 are arranged in contact with or separated from the back surface of the glass substrate 11 to act as a planar heat source. Other configurations and operations are the same as those in FIG.

As described above in detail, the present invention preliminarily heats the cutting position of the brittle material with a surface heat source, maintains the cutting position in a state immediately before the cutting, and provides a local heat source at the pre-heated cutting position. The full body is cleaved along the planned cleaving position by scanning. According to the present invention, the full body thermal stress that can greatly increase the cleaving speed as compared with the conventional full body cleaving while having the high quality of the fractured surface of the full body cleaving technology by the laser. Cleaving can be realized. Further, even in high-speed cleaving, there is no striped pattern on the cut surface, and full-body thermal stress cleaving having high smoothness can be realized.

  Cutting of glass used for flat panel displays such as liquid crystal displays and plasma displays is currently performed with a diamond cutter, and the necessity of a cleaning process after cutting to generate cullet, and the strength reduction due to the presence of microcracks, etc. Presents the problem. The full body thermal stress cleaving according to the present invention can be used for cleaving glass used in flat panel displays such as liquid crystal displays and plasma displays, and cleaving various brittle materials such as quartz, ceramics and semiconductors.

Characteristic diagram showing changes in radial stress component σ _x and tangential stress component σ _y when there is a temperature rise in the Gaussian distribution centered at the origin for explaining the principle of thermal stress generation in the laser cleaving method It is a conceptual perspective view explaining the conventional laser cleaving method of glass, (a) is a surface scribe, (b) is a schematic diagram in the case of full body cleaving Graph explaining the principle of glass breaking with a conventional wire heat source BRIEF DESCRIPTION OF THE DRAWINGS It is a top view which shows the state when a brittle material substrate for demonstrating the cleaving method in the Example of this invention is heated in strip | belt shape, (a) is the state of thermal-stress generation | occurrence | production, (b) is a state of a glass substrate by thermal stress. Cleaved from one side It is a figure for demonstrating the cutting method in the Example of this invention, and is a top view which shows a state when a local heat source is scanned in the state which preliminarily heated the brittle material board | substrate in the strip | belt shape It is a figure for demonstrating the cleaving method in the Example of this invention, and a top view explaining the progress of the cleaving line when a glass substrate is heated with a local heat source (A), (b) is the graph for demonstrating the principle of operation of the cleaving method in the Example of this invention by a stress intensity factor. (A)-(f) is a graph for demonstrating the process of the cleaving method in the Example of this invention. The conceptual perspective view of the cleaving apparatus which enforces the full body cleaving method of the brittle material in Example 1 of this invention Graph showing cleaving speed against substrate width when cleaving without preheating The conceptual perspective view of the cleaving apparatus which enforces the full body cleaving method of the brittle material in Example 2 of this invention The conceptual perspective view of the cleaving apparatus which enforces the full body cleaving method of the brittle material in Example 4 of this invention

Explanation of symbols

1 Irradiation laser light for surface scribing
2 Glass substrate 3 Scanning direction of irradiation laser light 4 Propagation by heat conduction of generated heat 5 Full-body cutting irradiation laser light 6 Cutting 11 Glass substrate 12 Band-shaped heating parts 13, 14, 15 Tensile stress 16, 17 Expansion force 18 Initial crack 19 Laser heating part 20 Tensile tension 22 Scanning direction 25, 26 Compressive stress 27 Breaking line 28 Breaking line tip 29 Near the rear end of the laser heating part in the traveling direction 31 Peak near the leading edge side of the laser beam 32 Peak on the trailing edge side of the laser beam 33 Initial crack 34 Initial crack position 35 Split line 36 Position where the stress intensity factor K1 is smaller than the fracture toughness value K1c 41 Stage 43 Surface heat source 44 Preheating region 45 Planned fracture line 46 Initial crack 47 Laser light source 48 Laser beam 49 Nichrome wire 51, 52 Electrode 53 Power supply 54 Capacitance of glass substrate 55 Glass substrate Dielectric loss

Claims (10)

Preliminarily heating the cleaved position of the brittle material with a surface heat source, applying a tensile stress due to thermal stress to the cleaved position of the brittle material and holding it in the state immediately before cleaving, and supplying the local heat source at the preheated cleaved position The full-body cleaving method of a brittle material, wherein the tensile stress is increased by scanning and full-body cleaving is performed along the planned cleaving position. The full body cleaving method for a brittle material according to claim 1, wherein the speed of the full body cleaving is controlled by a scanning speed of a local heat source. The full body cleaving method for a brittle material according to claim 1, wherein the position of the cleaving line in the full body cleaving is controlled by a scanning position of a local heat source. 2. The full body cleaving method for a brittle material according to claim 1, wherein the timing for starting the full body cleaving is controlled by the timing of starting scanning of a local heat source. The full-body cleaving method for a brittle material according to claim 1, wherein an initial crack is formed at an end portion of the brittle material at the planned cleaving position. 2. The full-body cleaving method for a brittle material according to claim 1, wherein the surface heat source is a far-infrared lamp arranged on one main surface of the brittle material so as to be spaced apart. The full-body cleaving method for a brittle material according to claim 1, wherein the surface heat source is a belt-like heat source disposed on or in contact with one main surface of the brittle material. The full body cleaving method for a brittle material according to claim 1, wherein the local heat source is a laser beam. The full body cleaving method for a brittle material according to claim 1, wherein the local heat source is due to dielectric loss based on a high frequency voltage applied between electrodes brought into contact with the front and back surfaces of the brittle material. 2. The full body cleaving method for a brittle material according to claim 1, wherein the local heat source is a minute heat source.