TWI779068B - Method for reducing residual stress of glass substrate and device for reducing residual stress of glass substrate - Google Patents

Abstract

The invention can reduce the residual stress of the glass substrate integrally formed with materials with low heat resistance such as resin. In addition, even for glass substrates that usually break within tens of minutes due to high residual stress, the residual stress can be reduced before the breakage occurs. The method for reducing the residual stress of the glass substrate G includes: a laser light irradiation step, which is to irradiate a part of the glass substrate G with a high residual stress with laser light to heat; and a cooling step, which is to irradiate the laser light and heat part of the cooling.

Description

Method for reducing residual stress of glass substrate and device for reducing residual stress of glass substrate

The invention relates to a method for reducing the residual stress of a glass substrate and a device for reducing the residual stress of the glass substrate.

In order to cut out the glass substrate according to the size of the product, a scribing line is formed on the glass substrate by a knife wheel, and then the glass substrate is bent to divide the glass substrate along the scribing line (for example, refer to Patent Document 1) . However, the force applied by the blade of the cutter wheel and the stress applied during breaking will cause residual stress to remain on the scribing line. Therefore, cracks tend to naturally occur along the horizontal direction on the surface of the glass substrate, and the cracks are further expanded by moisture or the like as time passes.

In addition, a technique is known in which the strength of the end surface of the glass substrate is increased by irradiating laser light to the end surface (edge) of the glass substrate to perform fusion chamfering (for example, refer to Patent Document 2). With this fusion chamfering, the fine cracks on the edge of the substrate disappear, and the strength of the end surface is improved. However, in this method, residual stress is generated near the melting portion. Also, the possibility of cracking of the substrate increases due to the residual stress. Specifically, the possibility of failure due to the growth of internal defects over time or subsequent loss increases, and depending on the magnitude of the residual stress, failure may occur within several tens of minutes. [Prior Art Document] [Patent Document]

[Patent Document 1] Japanese Patent Laid-Open No. 6-144875 [Patent Document 2] Japanese Patent No. 5245819

[Problem to be solved by the invention]

In consideration of the above circumstances, methods for reducing the residual stress at the edge of the glass substrate have been previously developed. For example, in the method of reducing the residual stress of the glass substrate, the temperature is raised first, and then slowly cooled. Specifically, first, the entire glass substrate is uniformly heated to a temperature above the glass transition point, secondly, the temperature is maintained for a fixed time, and finally, the entire glass substrate is slowly cooled to normal temperature. Generally speaking, the steps of heating, holding, and slow cooling take several hours or more. In this method, there is an advantage that the residual stress at the edge of the glass substrate can be almost completely removed. Also, it has the advantage that multiple glass substrates can be processed simultaneously in the furnace.

However, since the entire substrate needs to be heated above the glass transition point, it cannot be applied to glass products integrated with materials with low heat resistance such as resin. In FIG. 30 , a glass product in which resin materials P1 and P2 are integrally formed on a glass substrate G is shown. Also, since it takes several hours or more to reduce the residual stress once, it is impossible to reduce the residual stress immediately after the generation of the residual stress. Therefore, it is difficult to apply to glass substrates that have a high probability of being broken within tens of minutes due to high residual stress.

A first object of the present invention is to reduce the residual stress of a glass substrate integrated with a material having low heat resistance such as resin. The second object of the present invention is to reduce the residual stress before the damage occurs even for a glass substrate that usually breaks within tens of minutes due to high residual stress. [Technical means to solve the problem]

Hereinafter, a plurality of aspects will be described as technical means for solving the problems. These aspects can be combined arbitrarily as needed.

A method of reducing the residual stress of a glass substrate according to an aspect of the present invention includes the following steps. ◎Laser light irradiation step, which is to irradiate the part of the glass substrate with high residual stress to heat with laser light. ◎The cooling step is to cool the part heated by irradiation with laser light. In this method, since the portion with high residual stress of the glass substrate is heated, the residual stress of the glass substrate integrally formed with a material having low heat resistance such as resin can be reduced. The reason for this is that since the entire glass substrate is not heated, it is difficult to exert thermal influence on resin and the like. In addition, in this method, the glass substrate is heated for about 1 picosecond to 100 seconds, thereby reducing the residual stress in the heating zone, so even for a glass substrate that usually breaks within tens of minutes, it can be Reduce residual stress before failure occurs. The so-called "the portion with high residual stress is heated" means that there is a portion on the glass substrate that is not heated. The so-called "reducing residual stress" means that the growth of internal defects over time is suppressed, and the residual stress is reduced to such an extent that the glass substrate without external force will not break within a predetermined period of time. In this method, the heated area irradiated with laser light is cooled. Therefore, even if the adjacent areas are heated successively at relatively short time intervals, the residual stress can be reduced in the plurality of heated areas. The reason for this is that, by cooling, the region to become high temperature does not expand in the extending direction of the plurality of heated regions, so the effect of reducing the residual stress is maintained. As a result, lead times are shortened. Cooling can be carried out all the time or after laser light irradiation. The cooled portion may be only a heated portion, or may be the entirety of the glass substrate including the heated portion.

The step of irradiating laser light can also be irradiating multiple laser beams to multiple places at the same time. In this method, reduction of residual stress can be achieved in a short time.

The above-mentioned step of irradiating laser light may also be performed repeatedly to irradiate laser light to different locations. In this method, as a result of the increase in the area irradiated with laser light, the area of the area where the residual stress is reduced increases.

A device for reducing residual stress of a glass substrate according to another aspect of the present invention includes a laser device and a cooling device. A laser device heats a portion of a glass substrate having a high residual stress by irradiating laser light. The cooling device cools the part heated by irradiation with laser light. In this device, the portion with high residual stress of the glass substrate is heated, so that the residual stress of the glass substrate integrally formed with a material having low heat resistance such as resin can be reduced. The reason for this is that since the entire glass substrate is not heated, it is difficult to exert thermal influence on resin and the like. In addition, in this device, the glass substrate is heated for about 1 picosecond to 100 seconds, thereby reducing the residual stress in the heating zone, so even for a glass substrate that usually breaks within tens of minutes, it can be Reduce residual stress before failure occurs. In this device, the heated area irradiated with laser light is cooled. Therefore, even if the adjacent areas are heated successively at relatively short time intervals, the residual stress can be reduced in the plurality of heated areas. The reason for this is that, by cooling, the region to become high temperature does not expand in the extending direction of the plurality of heated regions, so the effect of reducing the residual stress is maintained. As a result, lead times are shortened. Cooling can be carried out all the time or after laser light irradiation. The cooled portion may be only a heated portion, or may be the entirety of the glass substrate including the heated portion.

The laser device can also irradiate multiple laser beams to multiple places at the same time. In this device, residual stress can be reduced in a short time.

The laser device can also repeatedly irradiate the laser light to different places. In this device, as a result of the increase in the area irradiated with laser light, the area of the area where the residual stress is reduced increases. [Effect of Invention]

According to the present invention, it is possible to reduce the residual stress of a glass substrate integrated with a material having low heat resistance such as resin. The reason for this is that since the entire glass substrate is not heated, it is difficult to exert thermal influence on resin and the like. Furthermore, according to the present invention, the residual stress can be reduced before the fracture occurs even for a glass substrate that usually breaks within tens of minutes due to high residual stress. The reason for this is to heat one or several places of the glass substrate for about 1 picosecond to 100 seconds, and perform the heating once or perform the heating multiple times with the heating position shifted, thereby reducing the residual stress in the heated area. .

1. First Embodiment (1) Laser Irradiation Apparatus Fig. 1 shows the overall configuration of a laser irradiation apparatus 1 according to an embodiment of the present invention. Fig. 1 is a schematic diagram of a laser irradiation device according to a first embodiment of the present invention. The laser irradiation device 1 has a function of reducing the residual stress of the portion near the end surface by heating the portion of the glass substrate G where the residual stress is high.

The glass substrate G includes glass forming only and glass combining other members such as resin. Typical examples of the types of glass include soda glass and non-alkali glass used for displays, instrument panels, and the like, but the types are not limited thereto. Specifically, the thickness of the glass is 3 mm or less, for example, in the range of 0.004 to 3 mm, preferably in the range of 0.2 to 0.4 mm.

The laser irradiation device 1 includes a laser device 3 . The laser device 3 has a laser oscillator 15 for irradiating the glass substrate G with laser light, and a laser control unit 17 . The laser control unit 17 can control the driving of the laser oscillator 15 and the laser power.

The laser device 3 has a transmission optical system 5 that transmits laser light to the mechanical drive system side described below. The transmission optical system 5 includes, for example, a condenser lens 19 , a plurality of reflection mirrors (not shown), a mirror (not shown), and the like. The laser irradiation device 1 has a drive mechanism 11 for changing the size of the laser spot by moving the position of the condenser lens 19 along the optical axis direction.

The laser irradiation apparatus 1 has the processing table 7 on which the glass substrate G is mounted. The processing table 7 is moved by the table drive unit 13 . The table drive unit 13 has a moving device (not shown) that moves the processing table 7 in the horizontal direction relative to the processing head (not shown). The moving device has known mechanisms such as guide rails and motors.

The laser irradiation device 1 includes a control unit 9 . The control section 9 has a processor (for example, CPU (Central Processing Unit, central processing unit)), memory device (for example, ROM (Read Only Memory, read-only memory), RAM (Random Access Memory, random access memory) ), HDD (Hard Disk Drive, hard disk drive), SSD (Solid State Drives, solid state drive), etc.), computer systems with various interfaces (eg, A/D converter, D/A converter, communication interface, etc.). The control unit 9 executes various control actions by executing the programs stored in the memory unit (corresponding to a part or all of the memory area of the memory device). The control unit 9 may include a single processor, or may include a plurality of independent processors for each control.

The control unit 9 can control the laser control unit 17 . The control unit 9 can control the drive mechanism 11 . The control unit 9 can control the drive unit 13 . A sensor for detecting the size, shape and position of the glass substrate G, a sensor and a switch for detecting the status of each device, and an information input device are connected to the control part 9; however, this is not shown in the figure.

In FIG. 1, the substrate cooling apparatus 35 which cools a substrate by injecting gas from the front side or the back side of the glass substrate G is shown. The operation of the substrate cooling device 35 is controlled by the control unit 9 . Furthermore, the cooling medium used for cooling is not particularly limited. The substrate cooling device can also be realized by setting the platform on which the glass is placed as a water cooling platform. A substrate cooling mechanism may also be mounted on the laser irradiation apparatus 1 .

(2) Fusion chamfering operation As an example of processing in which residual stress is generated on the glass substrate G, the operation of fusing and chamfering the end surface of the glass substrate G will be described using FIGS. 2 to 4 . Fig. 2 is a schematic diagram of a glass substrate showing movement of a laser spot. Fig. 3 is a cross-sectional photo of a glass substrate after melting and chamfering. Fig. 4 is a graph showing the change in retardation from the end surface toward the center side of the glass substrate after melting and chamfering. As shown in FIG. 2 , facing the glass substrate G, the laser light is irradiated to the portion 21 near the end surface of the glass substrate G, and then the laser spot S is scanned along the end surface 20 of the glass substrate G. At this time, the laser spot S is set so as to move from the end surface 20 of the glass substrate G toward the inner side (central side) of the substrate to a position at a distance of, for example, 10 μm to 150 μm.

By irradiation and scanning of the laser spot S as described above, the portion 21 near the end face of the glass substrate G is heated. In particular, by irradiating the laser light of the mid-infrared light, the laser light is absorbed while being transmitted to the inside of the glass substrate G. Therefore, the end surface 20 of the glass substrate G is heated relatively uniformly not only on the front side, which is the irradiation surface of the laser light, but also on the inside and the entire rear side of the glass substrate G relatively uniformly. Therefore, the end surface 20 of the glass substrate G is melted so that the central portion of the substrate thickness bulges outward, and as a result, the end surface 20 is chamfered as shown in FIG. 3 .

As a result of the above, as shown in FIG. 4 , the retardation (nm) increased in the vicinity of the end surface of the glass substrate G (for example, a region 200 μm away from the end surface 20 ). Retardation is the phase difference produced by the light passing through the object, and it is a value proportional to the stress acting on the object. The so-called higher retardation of an object to which no external force is applied indicates higher residual stress.

(3) Residual stress reduction treatment The residual stress reduction treatment will be described using FIGS. 5 to 8 . 5 to 8 are schematic views of the glass substrate showing the movement of the laser spot according to the first embodiment.

In FIG. 5 , the laser spot S1 is irradiated to one point of the portion 21 near the end surface. In FIG. 6 , the laser spot S2 is irradiated to another point at a different position of the portion 21 near the end face. In FIG. 7 , the laser spot S3 is irradiated to yet another point at a different position of the portion 21 near the end surface. In FIG. 8 , the laser spot S4 is irradiated to yet another point at a different position of the portion 21 near the end face.

If the laser spot is irradiated to a point on the residual stress generating region Z for a certain period of time and heated to a temperature above the glass transition point, the residual stress will decrease in this region. Therefore, as can be seen from FIGS. 5 to 8 , by sequentially heating one point for a specific time, the laser spots S1 to S4 are irradiated to consecutive and adjacent positions in the direction of the end face. As a result, the entire portion 21 near the end face is irradiated. . However, the number, position, irradiation order, and ratio of the laser spots in the portion near the end surface 21 are not limited to this embodiment.

In this embodiment, by repeating the operation of heating one point for a specific time and the operation of heating one point for a specific time by shifting the position, the residual stress generation region Z (hatched region) reaches a temperature equal to or higher than the glass transition point , to reduce the residual stress of the entire portion 21 near the end face. In this embodiment, the laser spot S is finally irradiated to the entire portion 21 near the end face, thereby reducing the residual stress in the entire portion 21 near the end face. However, when it is only necessary to reduce the residual stress in a part of the portion 21 near the end face, the laser spot S can also be irradiated only to a specific area of the portion 21 near the end face, or can only be irradiated to half of the entire portion 21 near the end face. left and right areas.

(4) The shape of the laser spot in the residual stress reduction process The present inventors obtained the following findings based on experiments, and thus conceived the present invention. The so-called discovery means that in the residual stress reduction process, a region that will become a high temperature is required. Contained within a narrow range along the direction of the end face 20 . In this embodiment, one point of the portion 21 in the vicinity of the end face is heated for a specific time, thereby reducing the residual stress in the heated region. 9, 10 and 11 are schematic plan views showing changes in the shape of the laser spot S. FIG. In FIG. 9 , a circular laser spot S100 and an elliptical laser spot S101 elongated in a direction perpendicular to the end face 20 are shown. In FIG. 10 , elliptical laser spots S102 and S103 extending along the end face 20 are shown. In FIG. 11, the laser spot S104 which covers the whole end surface 20 and is long along the end surface 20 is shown. In the case of using the laser spots S100, S101, S102, S103, if the laser output and the specific time for heating are adjusted, the residual stress in the heated area is reduced. Wherein, the order of the residual stress reducing effect is S100≒S101>S102>S103. In the case of using the laser spot S104, even if the laser output and the specific time for heating are adjusted, the residual stress does not decrease. In view of the experimental results shown above, the present inventors came up with the present invention by finding that, in the residual stress reduction process, it is necessary to suppress the region that will become high temperature in the direction along the end surface 20 within a narrow range.

When the laser spot S is circular, for example, the diameter is preferably 4 μm to 20 mm. The larger the diameter of the laser spot S, the larger the treatment area per heating, and the shorter the time required to reduce the residual stress of a specific area. As shown in FIGS. 9 and 10 , the laser spot S can also be elliptical. Wherein, the longer the width of the laser spot S along the direction of the end surface 20 is relative to the width of the laser spot S in the direction intersecting the end surface 20 , the lower the effect of reducing residual stress. The width of the laser spot S along the direction of the end surface 20 is preferably less than 10 times the width of the laser spot S in the direction intersecting the end surface 20 .

The specific time for heating depends on the temperature of the heating zone being heated. That is, as the heating is performed with a higher output, the temperature of the heating zone becomes higher, and the residual stress decreases in a shorter time. The higher the output for heating, the shorter the specific time for heating can be, and the shorter the lead time. The specific time for heating is preferably about 1 picosecond to 100 seconds, for example. The minimum specified time is 1 picosecond which is recognized as the minimum time required for the structure of glass to relax (relaxation time). The lower the temperature of the heating zone, the longer the relaxation time. When the temperature of the heating zone is around the glass transition point, it is preferable to set the specific time for heating to about 100 seconds as the relaxation time. If the specific time for heating is to be extremely short, the glass substrate G needs to be heated to a high temperature in a short time, and the required output will be greatly increased. Therefore, in practice, it is necessary to take into account the advantages of shortening the production time and the output. The heating conditions are determined by the cost increase caused by the rise.

The laser output needs to be of a value capable of heating above the glass transition point. It is properly set according to the size of the laser spot, the laser wavelength, the type of glass or the thickness of the plate. In addition, when the temperature of the heating part of the glass substrate G is about a glass transition point, deformation|transformation of a heating part is hardly recognized. When the temperature of the heating part is higher, the heating part melts and the shape changes. The higher the laser output is, the lower the viscosity of the heating part is, and the deformation will be large in a shorter time. According to the present invention, even when the laser output is high and the shape of the glass substrate G is deformed, the residual stress is reduced. Wherein, when the present invention is applied to a product that has restrictions on the allowable deformation of the glass substrate G, an upper limit should be set for the laser output, so as to prevent the viscosity of the glass substrate G from decreasing and causing the deformation to exceed the allowable value. An example of heating conditions for a specific time will be described for an alkali-free glass with a thickness of 200 μm. A CO ₂ laser with a spot size of 4 mm (wavelength of 10.6 μm) was used, and the conditions were: 3 W, 20 s. Conditions can also be: 4 W, 4 s. Conditions can also be: 6 W, 2 s.

The type (wavelength) of the laser is not particularly limited. The direction in which heat is taken in and out toward the glass substrate G is not particularly limited. Heat can be input from the front side of the glass substrate G, heat can also be input from the back side, or heat can be input from the end surface 20 . In the above embodiment, the residual stress reduction treatment is performed after the fusion chamfering is completed, but the fusion chamfering process and the residual stress reduction treatment may be performed on one glass substrate G in parallel. Specifically, by using two laser beams, the residual stress reduction process was started in the middle of the melting and chamfering operation, and the two processes were performed simultaneously thereafter. In this case, the overall processing time is shortened. Furthermore, in order to use a plurality of laser beams, a plurality of laser oscillators may be prepared, and the laser beams may be branched from one laser oscillator.

As a result of the above, the portion 21 near the end surface of the glass substrate G (that is, the residual stress generating region Z) is heated to a temperature equal to or higher than the glass transition point, and as a result, the residual stress is reduced. In this method, the portion 21 near the end surface of the glass substrate G is heated (that is, the entirety of the glass substrate G is not heated), so that the portion 21 near the end surface of the glass substrate G integrally formed with a material with low heat resistance such as resin can be reduced. 21 residual stress. The reason for this is that it is difficult to affect the resin or the like by heat. Furthermore, the glass substrate is heated for about 1 picosecond to 100 seconds, and the heating is performed once or the heating is performed multiple times with the position staggered. In this way, the residual stress in the heating area is reduced, so even for high residual stress The glass substrate, which usually breaks within tens of minutes due to stress, can also reduce the residual stress before the breakage occurs.

(5) The shortening of the lead time achieved by cooling In the situation where the position is staggered and the above-mentioned specific time heating method is performed, the first heating is carried out, the second heating is carried out by staggering, and the third heating is carried out by staggering …by heating for a specific time one after another. At this time, if you want to shorten the lead time, you need to shorten the time interval between heating operations. However, in the sequence of heating positions as shown in FIG. 12, for example, the area immediately adjacent to the previous heating area becomes the next heating area. In this case, for example, the second heating needs to wait until the temperature of the first heating part drops. The reason for this is that, for example, the second heating region overlaps with the first heating region, corresponding to the above-mentioned "when the portion near the end surface of the glass substrate G is heated, the high temperature portion becomes longer along the end surface".

In the case of performing the above-mentioned staggered irradiation, the time interval between heating operations can be shortened by cooling the substrate. In FIG. 1, the substrate cooling apparatus 35 which cools a substrate by injecting gas from the front side or the back side of the glass substrate G is shown. In this case, the second heating is performed after the first heating area is cooled by air cooling or the like. Thereby, even when heating is performed in the order shown in FIG. 12, time intervals can be shortened.

The reason why the time interval can be shortened as described above is that the part heated by irradiation with laser light is irradiated with laser light again after cooling down. Therefore, even if the next time laser light is irradiated near the heated part, The area that will become high temperature will not expand in the direction along the end surface due to cooling. That is, the reason is that, in this case, it corresponds to the above-mentioned "case where the high temperature portion is suppressed to be narrow along the end surface in the case of heating the portion near the end surface of the glass substrate G". Cooling can be carried out all the time or after laser light irradiation.

Furthermore, the cooling medium used for cooling is not particularly limited. The substrate cooling device can also be realized by setting the platform on which the glass is placed as a water cooling platform. A substrate cooling mechanism may also be mounted on the laser irradiation apparatus 1 .

2. Second Embodiment The specific-time irradiation method of the first embodiment is a point heating method in which laser irradiation is performed one by one for each point, but laser irradiation may also be applied to multiple points at the same time. Such an example will be described as a second embodiment using FIGS. 13 to 16 . In this multi-point simultaneous irradiation method, the substantial processing speed becomes faster. 13 to 16 are schematic diagrams of a glass substrate showing the movement of the laser spot according to the second embodiment.

In FIG. 13 , two discrete laser spots S1 are irradiated to the portion 21 near the end face. In FIG. 14 , it is shown that the residual stress is reduced in the portion 21 near the end face by the operation of FIG. 13 .

In FIG. 15 , two discrete laser spots S2 are irradiated to the portion 21 near the end face. At this time, the two laser spots S2 are irradiated to positions different from the above two laser spots S1 , that is, they are irradiated while being offset therefrom. Also, the two laser spots S2 correspond to the remaining residual stress generation region Z. In FIG. 16 , it is shown that the residual stress is reduced in the portion 21 near the end face by the operation of FIG. 15 .

In the multi-point simultaneous heating method, when the number of heating regions is n points, an output that is n times higher than that of the one-point heating method in the first embodiment is required. Also, in the shielding method described below, a higher output is required corresponding to the area of the shielding portion. The heating conditions per point are the same as those in the first embodiment.

The interval between the heating regions is preferably at least 0.5 times the width of one point of the heating region. When the interval between the heating regions is too narrow, connecting multiple heating regions is equivalent to irradiating one laser spot that is longer along the residual stress generation region Z. That is, corresponding to the above-mentioned "the shape of the heating zone is elongated along the residual stress generating region Z", the effect of reducing the residual stress decreases. Using Fig. 17 and Fig. 18, the change of the distance from the shape of the heating region is shown. 17 and 18 are schematic plan views showing changes in the shape and spacing of heating regions.

In FIG. 17, three circular laser spots S105 are shown. The shape of the laser spot S105 is the same as that of the laser spot S100 in FIG. 9 , and the effect of reducing residual stress is high. Also, the interval between the laser spots S105 is set to be about the same as the width of the laser spots S105. In FIG. 18 , three oval-shaped laser spots S106 that are longer in the direction intersecting the end face 20 are shown. The shape of the laser spot S106 is the same as that of the laser spot S101 in FIG. 9 , and the effect of reducing residual stress is high. Also, the interval between the laser spots S106 is set to be about the same as the width of the laser spots S106. There are many combinations of shapes and intervals of laser spots besides the above.

The processing speed of the residual stress reduction treatment varies depending on the value of the heating zone. For example, when the width of the heating area is 8 mm, 10 points are heated at the same time, the heating time is 1 s, and the residual stress reduction range of each heating area is 4 mm, the processing speed of one irradiation is 4 mm×10 /1 s = 40 mm/s.

Using FIGS. 19 and 20 , a method of performing multi-point simultaneous heating using an optical branching element will be described. Fig. 19 is a schematic diagram showing branching of laser spots using a diffractive optical element or a transmission type spatial light modulator. Fig. 20 is a schematic diagram showing branching of laser spots using reflective spatial light modulators. In FIG. 19 , a diffractive optical element (Diffractive Optical Element, DOE) 31 or a transmissive spatial light modulator (Spatial Light Modulator, SLM) 31 is shown. In FIG. 20, a reflective spatial light modulator (SLM) 33 is shown. In addition, two reflecting mirrors 34 are also shown.

As shown in Figures 13 to 16, when the position is staggered and multi-point simultaneous heating is performed, the method of implementing the first heating, staggering the second heating, and staggering the third heating... , heating for a specific time one after another. At this time, if you want to shorten the lead time, you need to shorten the time interval between heating operations. However, for example, when any one of the second heating regions at multiple places is adjacent to any one of the first heating regions at multiple places, the second heating needs to wait until the first heating part It can only be executed when the temperature is lowered. The reason for this is that, for example, the second heating region overlaps with the first heating region, corresponding to the above-mentioned "when the portion near the end surface of the glass substrate G is heated, the high temperature portion becomes longer along the end surface".

In the case of performing the above-mentioned staggered irradiation, the time interval between heating operations can be shortened by cooling the substrate. For cooling, as shown in FIG. 1 of the first embodiment, a substrate cooling device 35 that cools the substrate by injecting gas from the front side or the back side of the glass substrate G is used. In this case, the second heating is performed after the first heating area is cooled by air cooling or the like. Thereby, even in the case where, for example, the second heating region is a region adjacent to the first heating region, the time interval can be shortened.

The reason why the time interval can be shortened as described above is that the part heated by irradiation with laser light is irradiated with laser light again after cooling down. Therefore, even if the next time laser light is irradiated near the heated part, The area that will become high temperature will not expand in the direction along the end surface due to cooling. That is, the reason is that, in this case, it corresponds to the above-mentioned "case where the high temperature portion is suppressed to be narrow along the end surface in the case of heating the portion near the end surface of the glass substrate G". Cooling can be carried out all the time or after laser light irradiation. Similar to the first embodiment, the configuration, cooling method, and arrangement position of the cooling device are not particularly limited.

(1) First Variation In the second embodiment, the method of performing multi-point simultaneous heating using the light splitting element was described, but multi-point simultaneous heating can also be performed by a shielding method. Using FIGS. 21 to 25 , a method of performing multi-point simultaneous heating by a shielding method will be described as a first modification example. Fig. 21 is a schematic diagram showing beam formation by a cylindrical lens. Fig. 22 is a schematic diagram showing beam formation using a galvanometer scanner. Fig. 23 is a schematic diagram showing beam formation using a polygon mirror. Fig. 24 is a schematic plan view showing the positional relationship between the shielding plate and the glass substrate. Fig. 25 is a schematic front view showing the positional relationship between the shielding plate and the glass substrate. A beam of elongated shape along the end surface 20 is formed by a cylindrical lens 41 ( FIG. 21 ), a galvanometer scanner 43 ( FIG. 22 ), a polygon mirror 45 ( FIG. 23 ), or the like.

Then, as shown in FIGS. 24 and 25 , a plurality of laser spots S are formed by partially shielding the laser beam B using a shielding plate 47 . The shielding plate 47 has a plurality of shielding portions 47a arranged with gaps in the end face direction. The shielding plate 47 needs to reflect or absorb the laser light. In the case of absorbing laser light, heat resistance is required. In the case of absorbing laser light but not having sufficient heat resistance, a forced cooling mechanism for the shielding plate is required. Furthermore, a mechanism (not shown) for moving the shielding plate 47 along the portion 21 near the end surface of the glass substrate G may be provided. In this case, the positions of the plurality of laser spots S can be changed, and the laser spots S can be irradiated to the entire portion near the end surface 21 by repeatedly changing the positions. In the first modification of the second embodiment, the first heating area is also cooled by air cooling or the like before the second heating, thereby shortening the time interval between heating operations and shortening the residual stress reduction treatment production interval time.

(2) Second Modification In the second embodiment, the method of performing multi-point simultaneous heating using the optical branching element was described, but multi-point simultaneous heating can also be performed by scanning the laser light pulse by pulse. Using FIGS. 26 to 29 , a method of simultaneously heating multiple points by scanning laser light pulse by pulse will be described as a second modification. Fig. 26 is a schematic plan view of a laser irradiation device according to a second modification example of the second embodiment. Fig. 27 is a schematic front view of a laser irradiation device. FIG. 28 is a schematic diagram showing the formation of three laser spots using a galvanometer scanner 43 . Figure 29 is a graph showing changes in laser pulse and ray angle with respect to time. As shown in FIGS. 26 and 27 , the laser irradiation device 1A includes a laser oscillator 15 , a beam expander 49 , a condenser lens 19 , and a galvanometer scanner 43 . In addition, the laser irradiation device 1A uses a galvanometer scanner 43 to control the irradiation position of the laser light pulse by pulse, and irradiates the laser light to multiple places approximately simultaneously, thereby forming a state in which multiple points are heated simultaneously.

In the example of Fig. 28, a galvanometer scanner is used to change the beam angle of the laser beam by 1°, whereby the position of the laser spot on the sample surface will move by 10 mm. As shown in Figure 29, when the angle of the light is changed synchronously with the laser pulse oscillating at 500 Hz, the laser light has a round trip in the area of 20 mm at a period of 12 milliseconds, and each of the three laser spots is only Laser light is irradiated for 2 milliseconds in one cycle (12 milliseconds). Also, no laser light is irradiated to the area between the three laser spots. In this case, since the cycle of scanning the laser light is very short, if this action is repeatedly performed for a specific time (for example, 1 second), the three points will be heated simultaneously for a specific time. In the second modification of the second embodiment, the first heating area is also cooled by air cooling or the like before the second heating, thereby shortening the time interval between heating operations and shortening the residual stress reduction treatment production interval time.

3. Other Embodiments As mentioned above, several embodiments of the present invention have been described, but the present invention is not limited to the above embodiments, and various changes can be made within the scope not departing from the gist of the invention. In particular, the plural embodiments and modifications described in this specification can be combined arbitrarily as needed. The present invention can also be applied to situations where fusion chamfering is not performed. The present invention can also be applied to a case where the residual stress generation region is not a portion near the end surface of the glass substrate G, for example, a central portion. [Industrial availability]

The invention can be widely applied to the method for reducing the residual stress of the glass substrate and the device for reducing the residual stress of the glass substrate.

1‧‧‧Laser irradiation device 1A‧‧‧Laser irradiation device 3‧‧‧Laser device 5‧‧‧Transmission optical system 7‧‧‧Processing table 9‧‧‧Control part 11‧‧‧Drive mechanism 13‧ ‧‧Table Drive Unit 15‧‧‧Laser Oscillator 17‧‧‧Laser Control Unit 19‧‧‧Concentrating Lens 20‧‧‧End Face 21‧‧‧Part near End Face 31‧‧‧Diffractive Optical Element or Transmission type spatial light modulator 33‧‧‧reflective spatial light modulator 34‧‧‧mirror 35‧‧‧substrate cooling device 41‧‧‧cylindrical lens 43‧‧‧galvanometer scanner 45‧‧ ‧Polygon mirror 47‧‧‧Shading plate 47a‧‧‧Shading part 49‧‧‧Beam expander B‧‧‧Laser beam G‧‧‧Glass substrate P1‧‧‧Resin material P2‧‧‧Resin material S‧‧ ‧Laser spot S1‧‧‧Laser spot S2‧‧‧Laser spot S3‧‧‧Laser spot S4‧‧‧Laser spot S100‧‧‧Laser spot S101‧‧‧Laser spot S102‧‧‧ Laser spot S103‧‧‧Laser spot S104‧‧‧Laser spot S105‧‧‧Laser spot S106‧‧‧Laser spot Z‧‧‧Residual stress generation area

Fig. 1 is a schematic diagram of a laser irradiation device according to a first embodiment of the present invention. Fig. 2 is a schematic diagram of a glass substrate showing movement of a laser spot. Fig. 3 is a cross-sectional photo of a glass substrate after melting and chamfering. Fig. 4 is a graph showing the change in retardation from the end surface toward the center side of the glass substrate after melting and chamfering. Fig. 5 is a schematic diagram of a glass substrate showing movement of a laser spot. Fig. 6 is a schematic diagram of a glass substrate showing movement of a laser spot. Fig. 7 is a schematic diagram of a glass substrate showing movement of a laser spot. Fig. 8 is a schematic diagram of a glass substrate showing movement of a laser spot. Fig. 9 is a schematic plan view showing changes in the shape of the laser spot. Fig. 10 is a schematic plan view showing changes in the shape of the laser spot. Fig. 11 is a schematic plan view showing changes in the shape of the laser spot. Fig. 12 is a schematic diagram of a glass substrate showing movement of a laser spot. Fig. 13 is a schematic diagram of a glass substrate showing movement of a laser spot according to a second embodiment. Fig. 14 is a schematic diagram of a glass substrate showing movement of a laser spot. Fig. 15 is a schematic diagram of a glass substrate showing movement of a laser spot. Fig. 16 is a schematic diagram of a glass substrate showing movement of a laser spot. Fig. 17 is a schematic plan view showing changes in the shape and interval of heating regions. Fig. 18 is a schematic plan view showing changes in the shape and interval of heating regions. Fig. 19 is a schematic diagram showing branching of laser spots using a diffractive optical element or a transmission type spatial light modulator. Fig. 20 is a schematic diagram showing branching of laser spots using reflective spatial light modulators. Fig. 21 is a schematic diagram showing beam formation by a cylindrical lens. Fig. 22 is a schematic diagram showing beam formation using a galvanometer scanner. Fig. 23 is a schematic diagram showing beam formation using a polygon mirror. Fig. 24 is a schematic plan view showing the positional relationship between the shielding plate and the glass substrate. Fig. 25 is a schematic front view showing the positional relationship between the shielding plate and the glass substrate. Fig. 26 is a schematic plan view of a laser irradiation device according to a second modification example of the second embodiment. Fig. 27 is a schematic front view of a laser irradiation device. Fig. 28 is a schematic diagram showing the formation of three beams. Figure 29 is a graph showing changes in laser pulse and ray angle with respect to time. Fig. 30 is a schematic top view of a conventional glass product integrally formed with a material having low heat resistance.

1‧‧‧Laser irradiation device

3‧‧‧Laser device

5‧‧‧Transmission optical system

7‧‧‧Processing table

9‧‧‧Control Department

11‧‧‧Drive Mechanism

13‧‧‧Taiwan drive unit

15‧‧‧Laser oscillator

17‧‧‧Laser Control Department

19‧‧‧condensing lens

35‧‧‧substrate cooling device

G‧‧‧Glass Substrate

Claims (6)

A method for reducing residual stress of a glass substrate, which is a method for reducing residual stress of a glass substrate, and includes: a laser light irradiation step, which is performed by irradiating laser light to a part of the above-mentioned glass substrate where the residual stress is high Heating; and a cooling step, which is to cool the part heated by irradiating the above-mentioned laser light, wherein the above-mentioned laser light irradiation step is to irradiate one or more laser light to different places successively, and the above-mentioned cooling step is in each After the step of irradiating laser light, the above-mentioned heated part is cooled one by one. The method for reducing the residual stress of a glass substrate as claimed in claim 1, wherein the laser light irradiation step uses a diffractive optical element, a transmission-type spatial light modulator or a reflective spatial light modulator to use the branched laser light as The plurality of laser beams are irradiated to the plurality of places at the same time. The method for reducing the residual stress of a glass substrate according to claim 1 or 2, wherein the glass substrate is a glass substrate integrated with a resin. A device for reducing the residual stress of a glass substrate, which is a device for reducing the residual stress of a glass substrate, and includes: a laser device, which irradiates a part of the glass substrate with a high residual stress with laser light to heat; and A cooling device, which cools the part heated by irradiation of the above-mentioned laser light, wherein the above-mentioned laser device irradiates one or more laser light to different places successively, and the above-mentioned cooling device is sequentially irradiating the above-mentioned laser light After irradiating to different parts, cool down the part irradiated with the above-mentioned laser light one by one. The device for reducing the residual stress of a glass substrate according to claim 4, wherein the laser device uses a diffractive optical element, a transmission-type spatial light modulator, or a reflective-type spatial light modulator to use the branched laser light as the complex number A laser beam is irradiated to multiple places at the same time. The device for reducing the residual stress of a glass substrate according to claim 4 or 5, wherein the glass substrate is a glass substrate integrated with a resin.

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