JP5562254B2 - Brittle material splitting apparatus and splitting method - Google Patents

Description

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

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

  According to laser scribing, 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 at the time of cleaving, the presence of a lower limit value of the applied plate thickness, and the like can be eliminated.

  The principle of laser scribing is as follows. Only glass is heated locally, and the laser beam is irradiated to such an extent that vaporization, melting and cracks 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. 9 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 from the beginning (negative value in FIG. 9), 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. It changes to (positive value in FIG. 9).

  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 to be equal to or less than the fracture toughness value, so that 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.

This glass laser scribing method was first developed by Mr. Kondratenko, and the Japanese Patent of Patent Document 1 was established. FIG. 10A shows the principle of the laser cleaving method according to Patent Document 1. As the laser light, CO ₂ laser light is used, and 99% of the energy in the beam spot 1 of the CO ₂ laser light is absorbed in the glass surface layer having a depth of 3.7 μm of the glass 2, over the entire thickness of the glass 2. Not transparent. This is due to the extremely large absorption coefficient of glass at the CO ₂ laser wavelength. The depth of the laser scribe is usually about 100 μm even if it is assisted by the heat conduction 4 in the glass 2.

  The glass 2 is highly brittle, and can be mechanically cleaved by applying a stress in accordance with the scribe line. This process of breaking all by application of mechanical stress is called breaking. That is, when the laser scribing method is adopted, a subsequent process called “break” is indispensable for dividing the glass, and since the break process is necessary, the practicality is limited and the spread is not necessarily complete. There wasn't.

  Considering the desire to completely sever the glass using a laser beam, laser scribing is not necessarily sufficient because laser scribing adds an after-process called breaking. Therefore, a full-body cleaving technique using a laser beam is needed and expected. However, in Patent Document 1, it is claimed that the laser scribing technique is superior because full-body cleaving has some drawbacks as described later, and the effectiveness of full-body cleaving is negative. Shows a strong position.

  As another prior document relating to the laser scribing technique, in Patent Document 2, a laser beam is irradiated onto a glass substrate, and an elliptical laser spot LS1 that is elongated in the Y-axis direction along the scanning direction of the glass substrate; It is described that an elliptical laser spot LS2 that is elongated along the X-axis direction is formed at a predetermined distance away. However, the object of the invention described in Patent Document 2 is not intended for full-body cleaving at all, and is intended only to perform stable laser scribing.

  On the other hand, when the laser beam 5 that is transmitted through the glass 2 as shown in FIG. 10B and is partially absorbed is irradiated, the transmitted light is cleaved with respect to the total thickness of the glass 2. 6 is generated, the glass 2 can be cleaved only in this step, and a break is not necessary. This cleaving is called full-body cleaving with a laser.

  In addition to the technical features of the laser cleaving method described above, the adoption of full body cleaving has the benefits of full body cleaving, such as eliminating the need for breaks and enabling free-curve cleaving. You will be able to improve. The applicant of the present application has proposed Patent Documents 3 and 4 for this full-body cleaving technique.

Japanese Patent No. 3027768 International Publication No. 03/008168 Pamphlet JP 2007-76077 A Japanese Unexamined Patent Publication No. 2007-261885

Since the cleaving according to Patent Document 1 is not a full-body cleaving, the breaking process is necessary and the practicality is limited as described above. In the full-body cleaving technique using laser proposed in Patent Documents 3 and 4, when a highly versatile CO ₂ laser beam is used as a laser light source, most of it is absorbed on the surface of the glass, so that it is applied as it is. It is not possible. In addition, as pointed out in Patent Document 1 in the full-body cleaving technique, when the cleaving position is separated from the workpiece end due to the so-called size effect, the cleaving speed is remarkably reduced, and the cleaving position is close to the end of the glass. There is a disadvantage that the split section is bent. The disadvantage due to the size effect will be described with reference to FIG.

First, the low speed property, which is the first drawback of full body breaking of glass, will be described. In FIG. 11A, consider a case where the glass plate 2 is cleaved with the widths W ₁ and W ₂ being large. When the laser beam 5 is scanned along the cleaving line 7 in the cleaving direction 3, a tensile tension is generated on the glass plate 2 by the above-described principle due to heating by laser beam irradiation, and the glass plate 2 follows the scanning locus of the laser beam 5. It will be divided. In FIG. 11A, this deformation is exaggerated, and the actual movement of the glass after breaking is about several microns.

At this time, if the widths W ₁ and W ₂ of the glass plate 2 on both sides of the breaking line 7 are large, the scanning speed of the laser beam 5 is significantly reduced. First, the tensile stresses F ₀ and F ₁ necessary for cleaving the glass plate 2 must overcome the resistance to deformation described above. This resistance acts on the area of the glass plate 2 and increases remarkably when the widths W ₁ and W _{2 of} the glass plate ₂ are large. Since the cleaving of the glass plate 2 must be performed against a large resistance, it is necessary to reduce the scanning speed of the laser beam 5 and relatively increase the amount of heating by the laser beam 5.

As a result, the scanning speed of the laser beam 5 has to be low, so the cleaving speed is naturally limited. This tendency becomes more prominent as the distance between the position of the breaking line 7 and the end of the glass plate 2 is larger, that is, as the widths W ₁ and W _{2 of the} broken glass plate 2 in FIG. For example, when the widths W ₁ and W ₂ of the glass plate 2 after cleaving are a distance of 500 mm, full body cleaving cannot be performed unless the scanning speed of the laser light 5 is set to a remarkably low speed of about 10 mm / s. .

Next, the fact that the fractured surface of the brittle material is curved with respect to the planned fracture position, which is another drawback of full body cleavage of the brittle material, will be described. As described with reference to FIG. 11A, the cleaving when the laser beam 5 is scanned along the cleaving line 7 in the cleaving direction 3 is performed in the creeping direction by the tensile stresses F ₀ and F ₁ acting on the glass plate 2. . At that time, when there is an imbalance in the above-described resistance force on both sides, a force is exerted on the split section to bend with respect to the planned cutting line. This is shown in FIG. FIG. 11B shows that when the width W ₃ is small, the resistance on the width W ₃ side is small, so that it is greatly curved, and the fractured section after cleaving is curved in a bow shape. This tendency is remarkable when the widths W ₁ and W ₃ of the glass plate 2 after cleaving are imbalanced, particularly when one width W ₃ is particularly small. Also in this case, as described above, the deformation of the workpiece is shown exaggerated more than the actual one of several microns.

  The present invention solves these problems of the prior art. While realizing the high quality of thermal stress cleaving by laser, the cleaving speed is greatly increased, and the cleaved surface is curved with respect to the planned cleaving line. It is an object of the present invention to provide a brittle material splitting device and a splitting method that can split a full body in a straight line.

  The brittle material splitting apparatus according to the present invention heats the brittle material along the planned fracture line from the side of the initial crack formed on the planned fracture line with respect to the planned fracture line assumed for the brittle material. A brittle material splitting device that splits the brittle material by relatively moving a heating position along the planned cutting line, and irradiating the brittle material with a laser beam along the planned cutting line Laser beam irradiation means for generating a heated portion, and cooling means for locally cooling the brittle material at a position behind the heating portion with respect to the moving direction along the planned cutting line, and the laser beam irradiation. The means includes a first beam irradiation unit that forms a first laser beam irradiation region located in front of the moving direction in the heating portion, and the movement of the first laser beam irradiation region in the heating portion. Characterized in that it comprises a second beam irradiation unit for forming a second laser beam irradiation region elongated along the expected splitting line behind the counter.

  In the brittle material dividing apparatus according to the present invention, the laser power applied to the first laser beam irradiation region formed by the first beam irradiation unit is applied to the second laser beam irradiation region formed by the second beam irradiation unit. It is preferably greater than the laser power provided. According to this configuration, the thermal energy necessary for dividing the brittle material can be efficiently given to the brittle material.

  In the brittle material splitting device according to the present invention, the laser power density of the first laser beam irradiation region formed by the first beam irradiation unit may be the second laser beam irradiation formed by the second beam irradiation unit. It is preferably lower than the laser power density of the region. According to this configuration, it is possible to give thermal energy necessary for dividing the brittle material without melting the surface of the brittle material.

  In the brittle material splitting device according to the present invention, the position of the first laser beam irradiation region formed by the first beam irradiation unit may be a position away from the rear end of the second laser beam irradiation region. A distance in a direction along the planned cutting line may be variable with respect to a cooling position formed by locally cooling by means. According to this configuration, the time-dependent state of thermal diffusion inside the brittle material can be changed.

  In this case, the distance between the position of the first laser beam irradiation region and the cooling position may be set based on at least one of the cleaving speed and the thickness of the brittle material. According to this configuration, the time until the brittle material heated in the first laser beam irradiation region starts to cool and / or the time until the temperature conduction due to thermal diffusion reaches the back surface of the brittle material is adjusted and set. be able to.

  In the brittle material splitting device according to the present invention, the first laser beam irradiation region may have a substantially circular shape. According to this configuration, the laser beam irradiated from the first beam irradiation unit can be used as it is or simply by changing the beam diameter.

  In the brittle material dividing apparatus according to the present invention, the shape of the first laser beam irradiation region may be a shape obtained by dividing a substantially circular central portion with a predetermined width. According to this configuration, it is possible to improve the linearity of the fractured surface.

  In this case, the first laser beam forming the first laser beam irradiation region may be generated by arranging a shield having a predetermined width in the center of the optical path of the laser beam from the first beam irradiation unit. . According to this configuration, the shape of the irradiation region of the first laser beam can be made into a shape obtained by dividing the substantially circular central portion with a predetermined width by a very simple method.

  In the brittle material splitting apparatus according to the present invention, the second laser beam forming the second laser beam irradiation region may be a diffractive optical element or a plano-convex cylindrical beam from the laser beam from the laser light source of the second beam irradiation unit. It may be generated by shaping through a lens. According to this configuration, the irradiation position shape of the second laser beam can be made non-circular by a very simple method.

  The brittle material splitting device according to the present invention further includes initial crack forming means for forming an initial crack at an end portion of the fracture line of the brittle material, and the first beam irradiation unit and the second beam irradiation unit include the first beam irradiation unit and the second beam irradiation unit. You may make it move along the said cutting planned line from the position of an initial crack. According to this configuration, the start of crack expansion for cleaving the brittle material can be performed with a low threshold.

  Further, in the brittle material splitting device according to the present invention, the laser beam irradiation means distributes a laser power of 50% or more to the first beam irradiation unit, and a laser power of less than 50% to the second beam irradiation unit. A beam splitter may be included. According to this configuration, one laser beam device is sufficient, and costs can be reduced.

  The method for cleaving a brittle material according to the present invention comprises heating the brittle material along a planned fracture line, and relatively moving the brittle material and the heating position along the planned fracture line to cleave the brittle material. A method for cleaving a brittle material, wherein an initial crack is formed at an end portion of the brittle material on the planned fracture line, and the brittle material is heated with the first laser beam and the second laser beam starting from the initial crack. The first laser beam is a beam positioned in front of the second laser beam in the movement direction along the planned cutting line, and the second laser beam is elongated along the planned cutting line. The beam is shaped, and a position separated from the rear end of the second laser beam by a predetermined position is locally cooled.

For the first and second laser beams in the present invention, for example, a CO ₂ laser generally used for surface laser scribing can be used. When the brittle material is cleaved by the second laser beam, the thermal energy of the second laser beam is efficiently conducted in the thickness direction of the brittle material by heating the front of the cleaved position by the first laser beam. By cooling the predetermined position, a crack that reaches the back surface of the brittle material is generated immediately below the cooling position. Therefore, the brittle material is heated by the first and second laser beams and then cooled by moving the first beam irradiating unit, the second beam irradiating unit, and the cooling means relatively along the planned cutting position of the brittle material. Can be cut full body along the planned cutting position.

  Thus, according to the present invention, the full-body cleaving speed of the brittle material can be greatly increased as compared with the prior art while realizing the high quality of thermal stress cleaving by the laser. Moreover, since the brittle material can be separated over almost the entire length of the processing length only by the thermal stress due to the laser, the occurrence of cullet accompanying the breaking process can be greatly suppressed. Furthermore, the split section can be cut into a straight line without being bent with respect to the planned cutting line.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a conceptual diagram showing the positional relationship and temperature characteristics of a laser beam for explaining the principle of a brittle material cleaving method according to the present invention, where (a) shows the irradiation position of a first laser beam and the irradiation position of a second laser beam. FIG. 2B is a conceptual plan view showing the positional relationship between the cooling positions and the cooling position. FIG. 1B shows a temperature profile when heating by the first laser beam and the second laser beam in FIG. FIG. 2C is a conceptual plan view for explaining a phenomenon caused by the positional deviation of the first laser beam and the second laser beam in FIG. It is a conceptual perspective view of the principal part for demonstrating the principle of the brittle material cleaving method by this invention. It is a conceptual diagram which shows the structure of the cleaving apparatus in Example 1 of the cleaving method of a brittle material by this invention. BRIEF DESCRIPTION OF THE DRAWINGS It is a cross-sectional conceptual diagram of the principal part for demonstrating in detail the principle of the cutting method of a brittle material by this invention, (a) is a cross-sectional conceptual diagram, (b) is the AA 'line cross section of Fig.4 (a). FIG. It is a perspective view explaining the broken cross section of the glass substrate cut | disconnected by the cleaving method of the brittle material by this invention. It is a conceptual diagram which shows the structure of the cleaving apparatus in Example 2 of the cleaving method of a brittle material by this invention. FIG. 5 is a conceptual diagram showing the positional relationship and temperature characteristics of a laser beam in Embodiment 2 of the cleaving method for a brittle material according to the present invention, where (a) is the irradiation position of the first laser beam, the irradiation position of the second laser beam, and cooling. FIG. 7B is a conceptual plan view showing the positional relationship between positions, and FIG. 7B is a diagram showing a temperature profile when heating by the first laser beam and the second laser beam in FIG. It is. In the embodiment of the method for cleaving brittle material according to the present invention, when initial heat is applied to one side of a non-alkali glass having a thickness of 0.7 mm, the temperature distribution graph plots the state of temperature change inside the glass over time. is there. FIG. 6 is a characteristic diagram illustrating changes in radial stress component σ _x and tangential stress component σ _y when there is a temperature increase in a 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 cut. It is a conceptual perspective view explaining the size effect in the conventional laser cleaving method of glass, (a) shows the case where the cleaving width on both sides of the glass plate is large, (b) shows the case where the cleaving width on one side of the glass plate is small. FIG. It is a figure which shows the processing experiment result of the full body cleaving which uses the non-alkali glass of thickness 0.7mmt.

  The principles and embodiments of the present invention will be described below in detail with reference to the drawings. In the following description, a glass substrate will be described as an example of the brittle material.

  FIG. 3 schematically shows the configuration of a glass substrate full-cut device according to an embodiment of the present invention. The glass substrate 11 is placed on a movable table 32, and the movable table 32 is moved in the XY plane by an XY driving device. In the figure, only the servo motor 33 for driving the Y axis, which is the moving direction of the glass, and the shaft axis are shown, and the X axis driving system is not shown.

In the present embodiment, _two laser oscillators for heating the glass, that is, the CO ₂ laser 21 and the CO ₂ laser 25 are used. The laser beam 22 emitted from the CO ₂ laser 21 is reflected vertically downward by the reflecting mirror 23 and shaped so as to have a predetermined beam diameter through the condenser lens 24. The beam that has passed through the condensing lens 24 is irradiated on the surface of the glass substrate 11 as it is, but in some cases, a beam shield 35 (see FIG. 6) as a beam attenuating unit is disposed on the beam transmission path. Accordingly, the shape of the beam is partially deformed. In any case, a first beam irradiation region by the first laser beam is formed on the glass substrate 11 by the laser beam 22. The position at which the first beam irradiation region is formed on the glass substrate 11 is adjusted by changing the folding angle of the reflecting mirror 23. In FIG. 3, the folding angle of the reflecting mirror 23 is set to be close to 90 °, but the first angle is set by shaking the same angle from about 80 ° to 110 ° and simultaneously aligning the position of the condenser lens 24. The position of the beam irradiation area is adjusted. Alternatively, the position of the first beam irradiation region can also be obtained by assembling one unit that fixes the relative position between the reflecting mirror 23 and the condenser lens 24 and moving the unit horizontally along the optical axis direction of the laser beam 22. Adjustment is possible.

A laser beam 26 emitted from the CO ₂ laser 25 is reflected vertically downward by a reflecting mirror 28 via a beam expander 27. When the laser beam 26 having a beam diameter of φ4 mm passes through the beam expander 27, the beam diameter is expanded by about four times to become a beam of φ16 mm. The expanded beam passes through the diffractive optical element 29 and is shaped into an elongated beam, thereby forming a second beam irradiation region by the second laser beam on the glass substrate 11.

  A cooling device 30 is installed behind the second beam irradiation region by the second laser beam. As the cooling device 30, a two-tube type cooling nozzle is used, and water is injected from the inner cylindrical tube and air is injected from the outer cylindrical tube. A cooling point is formed on the glass substrate 11 by spraying the mixed medium of water and air toward the glass. An initial crack forming device 31 is provided in front of the first laser beam. The initial crack forming apparatus 31 includes a diamond cutter at a lower end portion, and has an elevating mechanism that moves the diamond cutter up and down. By interlocking the elevating mechanism and the servo motor 33 for driving the Y axis, an initial crack can be formed at the end of the glass substrate 11.

In this embodiment, two CO ₂ lasers are used, but only one CO ₂ laser is used, a beam splitter is arranged on the beam transmission path, and the beam is divided into two paths. Transmission may be performed. In this case, the energy distribution rate by the beam splitter is such that energy of 50% or more is distributed to the first laser beam side that irradiates the front side, and energy that is less than 50% is applied to the second laser beam side that irradiates the rear side. Should be distributed.

  FIG. 1 (a) shows the mutual positional relationship between the irradiation position of the first laser beam, the irradiation position of the second laser beam, and the cooling position on the glass substrate surface for explaining the principle of the method of cleaving the brittle material according to the present invention. FIG. 1B is a diagram showing a temperature profile when heating by the first laser beam and the second laser beam in FIG. 1A is superimposed on the surface of the glass substrate, and FIG. FIG. 2C is a conceptual plan view for explaining a phenomenon caused by positional deviation of the first laser beam and the second laser beam in FIG. FIG. 2 is a conceptual perspective view of the main part for explaining the principle of the brittle material cleaving method according to the present invention.

  As shown in FIG. 1A, the basic principle of the method for cleaving a brittle material according to the present invention is that a first beam irradiation region 13 and a second beam irradiation are observed from the front of the cleaving along the planned cutting line 12 of the glass substrate 11. The region 14 and the cooling point (or cooling position) 15 are arranged in order.

As shown in FIG. 3, the first beam irradiation region 13 is generated by reflecting the laser beam 22 from the CO ₂ laser 21 in a predetermined direction by the reflecting mirror 23 and adjusting the laser beam 22 to a predetermined beam diameter through the condenser lens 24. The cross-sectional shape is a circle or an ellipse, and these are collectively referred to as a substantially circle throughout the specification and claims. The first beam irradiation region 13 is a laser beam having such an intensity that only the glass substrate 11 is locally heated and no melting or cracking occurs.

  The second beam irradiation region 14 is located behind the first beam irradiation region 13, and the cross-sectional shape thereof is shaped into an elongated shape in a direction along the planned cutting line 12 of the glass substrate 11. That is, in the second beam irradiation region 14, as shown in FIG. 1A, the length a in the direction along the planned cutting line 12 of the glass substrate 11 is longer than the length b in the width direction, which is the perpendicular direction. It is a circular beam. The ratio a / b of the length a in the length direction along the planned cutting line 12 to the length b in the width direction of the elongated non-circular beam is preferably about 26 to 30.

Such an elongate non-circular beam is obtained by spreading the laser beam 26 from the CO ₂ laser 25 to a diameter of a predetermined magnification by the beam expander 27 and reflecting the laser beam 26 in a predetermined direction by the reflecting mirror 28, and then diffracting optical element or flat beam. It is generated by passing through a beam shaping means 29 such as a convex cylindrical lens and shaping it. The second beam irradiation region 14 is also a laser beam having such an intensity that only heating locally occurs on the glass substrate 11 and melting and cracks do not occur.

  Next, the operation will be described. In FIG. 2, first, the initial crack 16 is formed by the initial crack forming device 31 at the end of the planned cutting line 12 of the glass substrate 11. This initial crack 16 is the starting position for cleaving the glass substrate 11. Next, the glass substrate 11 placed on the table 32 is moved in the Y direction by the Y-axis drive servomotor 33, and the direction of the initial crack 16 corresponding to the starting position of the planned cutting line 12 of the glass substrate 11. Begin heating the glass. As shown in FIG. 1A, the direction of the first beam irradiation region 13, the second beam irradiation region 14, and the cooling point 15 is arranged in a straight line. It can be moved to match. At this time, as shown in FIG. 1C, due to insufficient adjustment, the center position of the first beam irradiation region 13 and the center position of the second beam irradiation region 14 with respect to the planned cutting line 12 of the glass substrate 11 are minute values Δd. Since the surface quality of the divided glass cross section may be deteriorated if it is shifted by only a distance, the center position of the first beam irradiation region 13 and the center position of the second beam irradiation region 14 are not shifted from the planned cutting line 12. It is necessary to adjust the position accurately.

  Next, from the state in which the position of the initial crack 16 formed in the glass substrate 11 and the direction of the first beam irradiation region 13, the second beam irradiation region 14, and the column of the cooling point 15 coincide, When the glass substrate 11 placed on the table 32 is moved in the Y direction by the servo motor 33 while jetting the coolant from the cooling device 30 while irradiating the laser beam, the glass substrate 11 placed on the table 32 is moved. The row of the first beam irradiation region 13, the second beam irradiation region 14, and the cooling point 15 by the refrigerant moves relatively along the planned cutting line 12, and the cleaving action starts.

  As shown in FIG. 1A, the basic principle of the method for cleaving a brittle material according to the present invention is that a first beam irradiation region 13 and a second beam irradiation are observed from the front of the cleaving along the planned cutting line 12 of the glass substrate 11. It is arranging the area | region 14 and the cooling point 15 in order. The first beam irradiation region 13 preheats the forefront part of the cleaving of the glass substrate 11 and heats the position by the subsequent second beam irradiation region 14 to a state immediately before the cleaving starts. FIG. 1B is a temperature profile on the surface of the glass substrate 11 at this time. That is, the temperature profile 141 by the second beam irradiation region 14 is superimposed on the temperature profile 131 by the first beam irradiation region 13, and the position irradiated with the second beam irradiation region 14 on the surface of the glass substrate 11 is a high temperature just before the start of cleaving. To be heated. The heat due to this heating is conducted in the thickness direction of the glass substrate 11.

  When the coolant is jetted from the cooling device 30 onto the glass substrate 11 preheated in the substantially circular first beam irradiation region 13 and heated in the elongated second beam irradiation region 14, as shown in FIG. A crack expanded directly from the initial crack 16 directly proceeds in the depth direction of the glass substrate 11, and the crack is in the Y direction of the row of the glass substrate 11, the first beam irradiation region 13, the second beam irradiation region 14, and the cooling point 15. In accordance with the relative movement, the glass substrate 11 further proceeds along the planned cutting line 12. As a result, a split section 17 is generated over the entire thickness of the glass substrate 11.

  This will be described in more detail with reference to FIG. FIG. 4 is a conceptual cross-sectional view of the main part for explaining in detail the principle of the method of cleaving the brittle material according to the present invention in FIG. 2, (a) is a cross-sectional conceptual diagram, (b) is a cross-sectional conceptual diagram of FIG. It is AA 'line sectional drawing.

  When the row of the first beam irradiation region 13, the second beam irradiation region 14, and the cooling point 15 is scanned in the Y direction with respect to the glass substrate 11, the glass substrate 11 is first heated in the first beam irradiation region 13, and the heating is performed. As a result of the scanning in the Y direction, the heat due to the heat is conducted in the direction of the back surface of the glass substrate 11 to form a heating region 130 in the glass substrate 11. Next, the glass substrate 11 is heated in the second beam irradiation region 14, and the heat due to the heating is conducted in the back surface direction of the glass substrate 11 as scanning in the Y direction, and a heating region 140 is formed in the glass substrate 11. The Similarly, the cooling by the cooling point 15 in the rear part of the second beam irradiation region 14 is conducted in the rear surface direction of the glass substrate 11 as the glass substrate 11 is scanned in the Y direction, so that a cooling region 150 is formed in the glass substrate 11. .

  As a result, the heat distribution of the glass substrate 11 immediately below the cooling point 15 is as shown in FIG. 4B, and the glass substrate 11 continues to the heating region 130 heated to the vicinity of the back surface by the first beam irradiation region 13 and subsequent to it. Cooling by the cooling point 15 acts on the heating region 140 heated by the second beam irradiation region 14, and a crack advances in the depth direction of the glass substrate 11 immediately below the cooling point, and on the back surface of the glass substrate 11. To reach the entire thickness direction. This phenomenon proceeds along the planned cutting line 12 of the glass substrate 11 as the glass substrate 11 is scanned in the Y direction, and the cutting that reaches the back surface of the glass substrate 11 proceeds along the planned cutting line 12.

  FIG. 8 is a graph showing a temperature distribution with respect to the thickness direction of the glass. In the description using FIG. 4A described above, regarding the state of heat propagation in the thickness direction of the glass, heat is simply propagated at a constant linear function from the front to the back of the glass. Explained as if to do. However, since the heat propagation inside the glass is actually to be calculated based on the thermal diffusion equation, one example of the result of applying the equation to the non-alkali glass is illustrated.

The graph of FIG. 8 shows the temperature distribution in the thickness direction when assuming that a uniform heat distribution of 20 J / cm ² is applied to one side of an infinitely large non-alkali glass having a thickness of 0.7 mm. Is calculated, and the result is graphed. The horizontal axis of the graph shows the depth of heat propagation, that is, the thickness (mm) of the glass, and the vertical axis shows the temperature rise, that is, how much the temperature of the glass rises from the initial state. The reason why a plurality of curves are shown in the graph is that the graphs are displayed in an overlapping manner by changing the state using the elapsed time after the initial heating as a parameter.

By simply applying an initial amount of heat of 20 J / cm ^{2 to} one side of the glass, the heated glass surface instantaneously exceeds 400 ° C., but then the surface temperature of the glass rapidly decreases. At the same time as the temperature of the heating surface decreases, heat from the surface is transmitted to the back surface without heating, so that the temperature rises and slightly exceeds 100 ° C. The parameters of the elapsed time are calculated by sampling 10 samples from the time up to 1.0 second. From the shorter elapsed time, T1 = 30 msec, T2 = 40 msec, T3 = 50 msec, T4 = 75 msec, T5 = 100 msec, T6 = 200 msec, T7 = 300 msec, T8 = 400 msec, T9 = 700 msec, T10 = 1000 msec. It can be seen from this graph that there is a large temperature difference of 400 ° C between the front and back of the 0.7 mm thick glass after T1, ie 30 msec, but the temperature difference is relaxed to about 50 ° C after T6, ie 200 msec. It is that you are. Further, after T7, that is, 300 msec, the temperature difference is slightly less than 30 ° C., and it can be said that the front surface and the back surface are at substantially the same temperature.

In this embodiment using a CO ₂ laser, an energy source for full-body cleaving by propagation of thermal energy supplied by the first laser beam irradiated forward in the traveling direction to the back surface of the glass. It is characterized by being used as In order to perform such full body cleaving, it is necessary that the thermal energy absorbed on the glass surface is diffused evenly in the glass to some extent. Then, how much distance L is provided between the cooling point and the irradiation region of the first laser beam along the planned cutting line is one important item. Here, if the moving speed of the glass is V and the moving time required for the glass surface irradiated with the first laser beam to move below the cooling point is τ, the relationship of L = V · τ holds. As described above, a time of 200 to 300 msec is required for the temperatures of the front and back of the glass to be substantially the same. In other words, if the moving speed of the glass is 180 mm / s, it moves a distance of 36 mm for an elapsed time of 200 msec and 54 mm for an elapsed time of 300 msec. Accordingly, the distance L between the cooling point and the irradiation region of the first laser beam needs to be at least 36 mm, preferably 54 mm or more.

  Thus, how much distance L should be provided between the cooling point and the irradiation region of the first laser beam depends on the moving speed of the glass and the thickness of the glass. More specifically, it also relates to a physical constant related to the thermal diffusion rate inside the glass, that is, the thermal conductivity, specific heat, and density of the glass. It is also related to the boundary conditions on the back side of the glass. In other words, it is also affected by whether the back surface of the glass is fixed by means that comes into close contact with the metal table or by means that floats in the air.

  In the present embodiment, the crack expanded from the initial crack 16 immediately below the cooling point essentially proceeds in the depth direction of the glass substrate 11, so that an imbalance occurs in the tensile stress acting in the creeping direction of the glass substrate 11. The split section 17 is not curved with respect to the planned cutting line 12. Further, the cracked surface 17 formed by causing the crack to advance only by the thermal stress caused by the laser does not generate microcracks, and the mechanical strength of the divided glass substrate 11 is high.

  At the end portion on the planned cutting line 12 on the side opposite to the initial crack 16, the tensile stress sufficient to break the full body is lost. When approaching, the split 17 stops. At this time, as shown in FIG. 5, a region 18 in which the fractured surface 17 does not occur remains at the end of the glass substrate 15. In this region 18, the split section 17 does not occur, but a scribe groove 19 is formed on the surface. Therefore, if necessary, the glass can be completely divided by using a simple break means. In this case, since the glass substrate 11 has already been cleaved full body over almost the entire processing length, the occurrence of cullet associated with the breaking process can be greatly suppressed.

In the glass cutting apparatus shown in FIG. 3, as the first beam irradiation region 13, the laser beam 22 from the CO ₂ laser 21 with an output of 165 W was reflected vertically downward by the reflecting mirror 23 and condensed through the condenser lens 24. As a result, a circular beam irradiation region close to a Gaussian distribution with a beam diameter of 15 mm is formed on the glass substrate 11. As the second beam irradiation region 14, a laser beam 26 having an output of 98 W and a beam diameter of 4 mm from the CO2 laser 25 was used. The laser beam 26 is expanded to a beam diameter of 16 mm via a beam expander 27 and further transmitted vertically downward by a reflecting mirror 28. When a laser beam having a beam diameter of 16 mm passes through the diffractive optical element 29, an elongated beam having a length a of 26 mm and a width b of 1 mm is formed on the glass substrate 11.

  Thus, 165 W is applied to the first beam irradiation region 13 by the first laser beam, and 98 W is applied to the second beam irradiation region 14 by the second laser beam. That is, the thermal energy given to the first beam irradiation region 13 is set to be larger than the thermal energy given to the second beam irradiation region 14 even if the loss of beam transmission is taken into consideration on the glass substrate 11.

Regarding the laser power density, the laser power density of the first laser irradiation region 13 is 0.93 W / mm 2, and the laser power density of the second laser irradiation region 13 is 3.77 W / mm ² . That is, the laser power density of the first beam irradiation region 13 is set lower than the laser power density of the second laser irradiation region 13.

  As the glass substrate 11, a non-alkali glass having a thickness of 0.7 mm and a total length of 580 mm was used. As the cooling device, a two-tube type cooling nozzle was used, and water was injected from the inner cylindrical tube and air was injected from the outer cylindrical tube. The distance between the rear end of the second beam irradiation region 14 and the cooling point 15 was set to 5 mm. Processing was performed at a relative movement distance between the glass substrate 11 and the first beam irradiation region 13, the second beam irradiation region 14, and the row of the cooling points 15, that is, the glass cutting processing speed was 180 mm / s. As a result, full body cleaving was possible over a length of 540 mm excluding the terminal portion of the glass substrate 11 of about 40 mm. The linearity accuracy of the cleaving at this time was within ± 250 μm. Under the same conditions, even when the glass having a width of 290 mm and a length of 580 mm was cleaved at a position 15 mm away from the end surface, the linearity accuracy was ± 250 μm, and there was no influence of bending due to the so-called size effect.

  When the beam diameter of the first beam irradiation region 13 was changed from 10 mm to 16 mm, and the distance between the rear end of the second beam irradiation region 14 and the cooling point 15 was changed from 3 to 7 mm, almost the same cleaving result was obtained. The scanning speed increases the distance between the cooling point and the second beam irradiation region 14 and the distance between the second beam irradiation region 14 and the first beam irradiation region 13 simultaneously with increasing the power of the CO 2 lasers 21 and 25. Thus, it was confirmed that the speed could be further increased. Moreover, even when the ratio a / b to the length a and the width b of the elongated non-circular second beam irradiation region 14 was changed in the range of 26 to 30, substantially the same cleaving result was obtained.

  FIG. 6 is a conceptual diagram illustrating a brittle material cleaving apparatus according to a second embodiment. FIG. 7 shows a beam profile for heating. This beam profile is obtained by shielding the central portion of the output beam from the condenser lens 24 in the first beam irradiation region 13 with a beam shield 35 having a predetermined width in the glass cutting apparatus shown in FIG. It is. For example, a metal rod having a diameter of 2 mm is disposed on the beam path through which the beam is transmitted. Then, since a part of the first laser beam is shielded by the metal rod, a so-called shadow part is projected on the glass substrate, and the part is not heated. In the second embodiment, the shape of the first beam irradiation region 130 is a shape obtained by dividing a substantially circular central portion with a predetermined width w as shown in FIG. When the blocking portion 133 having a predetermined width w in the first beam irradiation region 130 is set to be slightly larger than the beam width e of the second beam irradiation region 14, the first beam irradiation region 130 is formed on the glass surface. There is no portion where the heating region and the heating region by the second laser beam overlap. Accordingly, the temperature profile on the glass substrate surface by the first beam irradiation region 13 and the second beam irradiation region 14 is as shown in FIG. 7B, and the thermal energy 141 used for heating the cleavage line and the cleavage The thermal energy 131 for heating the portions on both sides of the planned line can be separated.

  The cleaving process in Example 2 was essentially the same as in Example 1, and full-body cleaving was possible as in Example 1. In the first embodiment, the thermal energy for heating the planned cutting line is the thermal energy obtained by superimposing the laser beam irradiated by the first laser beam on the planned cutting line and the second beam irradiation region 14. Supplied. However, according to the second embodiment, since the thermal energy for heating the planned cutting line is supplied only by the first laser beam 14, the setting of the laser power to be irradiated becomes easy. As a result, there is an advantage that the linearity accuracy is improved, and full body cleaving can be performed with an accuracy within ± 100 μm over a total length of 540 mm.

  FIG. 12 summarizes the results of whether or not full-body cleaving is achieved when a glass cleaving experiment is performed in the configuration of the processing apparatus shown in FIG. As the beam profile, the substantially circular first beam irradiation method shown in FIG. The glass used is a non-alkali glass with a thickness of 0.7 mm. As a processing procedure, a method was adopted in which a glass having an outer width of 550 mm and a processing direction length of 290 mm was cut into strips from one end face at a constant interval (30 mm).

  As can be seen from the description in the table of FIG. 12, when the laser power P1 applied to the first beam irradiation region is set larger than the laser power P2 applied to the second beam irradiation region, the full body cleaving is performed. Is achieved in good condition (see machining conditions # 1, # 5, # 6, # 9, # 10, # 11). When the laser power P1 was set to be substantially the same as the laser power P2, the length of the uncut glass end portion tended to be slightly longer (see processing conditions # 2 and # 7). On the other hand, when the laser power P1 is smaller than the laser power P2, it is not preferable that full-body cleaving is not achieved, the length of the glass end portion is increased, or the surface quality of the cleaved surface is deteriorated. Machining results were obtained (see machining conditions # 3, # 4, and # 8). In particular, in order to achieve a high processing speed (for example, 200 mm / s or more), it has been found effective to set the laser power P1 far larger than the laser power P2 (processing conditions # 9, # 10). , # 11). Further, when the processing speed V was set to 230 mm / s, the distance L between the cooling position and the first beam irradiation region was set to 95 mm. By substituting these numerical values into the relational expression of L = V · τ, a value of τ = 413 (msec) is obtained. This value τ indicates the elapsed time required for the glass surface heated by the irradiation of the first laser beam to move to the cooling position. On the other hand, from the graph of the simulation result shown in FIG. 8 described above, a consideration result that an elapsed time of 200 msec or 300 msec or more is required as the time until the graph becomes flat and reaches thermal equilibrium is obtained. Since the value of this elapsed time τ = 413 (msec) is a value of 300 msec or more, it does not contradict the result of consideration based on FIG. In other words, it has been found that the distance L between the cooling position and the first beam irradiation region should be set longer as the processing speed V increases.

  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 brittle material splitting apparatus and cleaving method 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. If the brittle material splitting apparatus and cutting method according to the present invention are introduced into the manufacturing process of flat panel displays and the like, a great effect can be expected in improving processing speed, processing quality, economy, etc., and overcoming the weaknesses of the prior art. .

  DESCRIPTION OF SYMBOLS 11 Glass substrate, 12 Planned cutting line, 13 1st laser beam, 14 2nd laser beam, 15 Cooling point or cooling position, 16 Initial crack, 170% cross section, area where 180% cross section does not occur, 19 Scribe groove , 21 CO2 laser, 22 laser beam, 23 reflector, 24 condenser lens, 25 CO2 laser, 26 laser beam, 27 beam expander, 28 reflector, 29 beam shaping means, 31 cooling device, 31 initial crack forming device, 32 Table, 33 XY drive device, 131 Temperature profile by first laser beam, 133 Shielded portion, 141 Temperature profile by second laser beam.

Claims (15)

A position where the brittle material is heated along the planned cutting line from the side of the initial crack formed on the planned cutting line, and heated along the planned cutting line, with respect to the planned cutting line assumed for the brittle material A brittle material splitting device for splitting the brittle material by relatively moving,
Laser beam irradiation means for generating a heated portion by irradiating the brittle material with a laser beam along the planned cutting line;
A cooling means for locally cooling the brittle material at a position behind the heating portion with respect to a moving direction along the planned cutting line,
The laser beam irradiation means includes: a first beam irradiation unit that forms a first laser beam irradiation region located in front of the moving direction at the heating portion; and the first laser beam irradiation region at the heating portion. A second beam irradiation unit that forms a second laser beam irradiation region having an elongated shape along the planned cutting line behind the moving direction of
The brittle material dividing apparatus, wherein the first laser beam irradiation region has a shape obtained by dividing a substantially circular central portion with a predetermined width.   The first laser beam forming the first laser beam irradiation region is generated by arranging a shield having a predetermined width at the center of the optical path of the laser beam from the first beam irradiation unit. The brittle material dividing device according to claim 1. The brittle material dividing device according to claim 1, wherein the first laser beam irradiation region has a Gaussian distribution intensity distribution .   The first laser beam irradiation region has a length along the planned cutting line shorter than the second laser beam irradiation region and a length in a direction perpendicular to the planned cutting line is longer than the second laser beam irradiation region, and 4. The brittle material dividing apparatus according to claim 3, wherein a laser power given to the first laser beam irradiation region is larger than a laser power given to the second laser beam irradiation region.   The first laser beam irradiation region has a length along the planned cutting line shorter than the second laser beam irradiation region and a length in a direction perpendicular to the planned cutting line is longer than the second laser beam irradiation region, and The brittle material dividing device according to claim 3, wherein the laser power density is lower than that of the second laser beam irradiation region.   The position of the first laser beam irradiation region formed by the first beam irradiation unit is a cooling position formed by locally cooling a position away from the rear end of the second laser beam irradiation region by the cooling means. In contrast, the brittle material dividing device according to claim 3, wherein a distance in a direction along the planned cutting line is variable. The distance between the cooling position and the position of the first laser beam irradiation area of the brittle material according to claim 6, characterized in that it is set based on at least one of cleaving rate and thickness of the brittle material Splitting device.   The second laser beam forming the second laser beam irradiation region is generated by shaping the laser light from the laser light source of the second beam irradiation unit through a diffractive optical element or a plano-convex cylindrical lens. The brittle material dividing device according to claim 1, wherein   The laser beam irradiation unit includes a beam splitter that distributes a laser power of 50% or more to the first beam irradiation unit and distributes a laser power of less than 50% to the second beam irradiation unit. The brittle material dividing apparatus according to claim 3. A brittle material cleaving method that heats along a fracturing line of a brittle material, cleaves the brittle material by relatively moving the brittle material and the heating position along the fracturing line,
Forming an initial crack at the end of the brittle material on the planned cutting line;
The brittle material is heated with the first laser beam and the second laser beam starting from the initial crack, and the first laser beam moves in the moving direction along the planned cutting line with respect to the second laser beam. Is a beam having a shape obtained by dividing a substantially circular central portion with a predetermined width , and the second laser beam is a beam having an elongated shape along the planned cutting line,
Locally cooling a position away from the rear end of the second laser beam by a predetermined position;
Thereby, a split cross section extending from the initial crack to the back surface of the brittle material is formed from the brittle material end to the vicinity of the end portion on the planned cutting line, and from the vicinity of the end portion on the planned cutting line to the end. A brittle material cleaving method, comprising: forming a scribe groove on a rear surface in a moving direction, and then breaking along a scribe groove formed on a surface in the vicinity of a terminal end portion on the planned cutting line.   The brittle material cleaving method according to claim 10, wherein the first laser beam irradiation region has a substantially circular cross-sectional shape and a Gaussian distribution of intensity distribution.   The laser power given to the first laser beam irradiation region formed by the first laser beam is larger than the laser power given to the second laser beam irradiation region formed by the second laser beam. The method for cleaving a brittle material according to claim 10 or 11.   The first laser beam irradiation region formed by the first laser beam has a length along the planned cutting line shorter than the second laser beam irradiation region, and a length in a direction perpendicular to the planned cutting line is the second laser. The brittleness according to claim 10 or 11, wherein the brittleness is longer than the beam irradiation region and has a laser power density lower than a laser power density of the second laser beam irradiation region formed by the second laser beam. Material cleaving method.   The position of the first laser beam irradiation region formed by the first laser beam is compared with the cooling position formed by locally cooling the position away from the rear end of the second laser beam. The method for cleaving a brittle material according to claim 10 or 11, wherein a distance in a direction along the planned cleaving line is variable. The distance between the position of the first laser beam irradiation region and the cooling position is set based on at least one of a cleaving speed and a thickness of the brittle material. Cleaving method.

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