TWI469938B - Scribing method of glass substrate - Google Patents

Description

Glass substrate cutting method

The present invention relates to a method of cutting a glass substrate, and more particularly to a method of cutting a glass substrate in which a tempered glass having a reinforcing layer formed thereon is diced.

A method of forming a dicing groove for cutting a glass substrate is a method of forming using laser light. In this case, a part of the substrate is dissolved and evaporated by irradiating the laser light along the line to cut to form a cutting groove. However, in this method, a part of the substrate which has been dissolved and evaporated has adhered to the surface of the substrate, and the quality is deteriorated. In addition, the cut marks formed in the dissolved and evaporated portions may cause a decrease in the strength of the end face of the substrate.

Therefore, in the other dicing groove forming method, there is a method disclosed in Patent Document 1 or 2. Here, an initial crack is formed at a portion of the start of the dicing groove of the glass substrate, and the initial crack is irradiated with the laser light. Thereby, thermal stress is generated in the laser irradiation portion, and the crack is stretched to form a cutting groove.

Further, Patent Document 3 discloses a laser cutting method for improving the straight angle and the straightness of the cross section of the cut substrate. Here, when a dicing groove is formed in the substrate along the line to be cut, a region in which the dicing groove is not formed is formed in the vicinity of the end of the line to be cut.

[Patent Literature]

Patent Document 1: Japanese Patent Laid-Open No. 3-489

Patent Document 2: Japanese Patent Laid-Open Publication No. 9-1370

Patent Document 3: Japanese Reissue No. 2007/094348

However, in the recent industry of FPD (Flat Panel Display), since the strength of the end surface of the substrate is emphasized, the glass substrate is mainly used for chemically strengthened glass having a reinforcing layer formed on its surface. The chemically strengthened glass is subjected to an ion exchange treatment and has a layer (strengthening layer) having a compressive stress on its surface. Recently, it is used for a cover glass such as a touch panel which particularly requires end face strength ( Cover glass).

Such tempered glass is highly durable and is not easily scratched. Therefore, it is difficult to form an initial crack on the end surface of the tempered glass and form a dicing groove. For example, when the depth of the initial crack is shallow, the cutting groove is not formed. Further, on the other hand, when the initial crack is too deep, the initial crack cannot be stretched along the line to be cut, and the desired cut groove cannot be formed.

In addition, such tempered glass has a strong compressive stress on the surface and tensile stress inside. Therefore, when the tempered glass is irradiated with laser light by a conventional method to form a dicing groove, the crack mainly starts from a cutting groove (crack) formed on the end surface of the substrate on the scanning side of the laser light, and most of them have a thickness direction. The overall situation of stretching. When the crack is formed over the entire depth of the substrate, the substrate is naturally separated along the line to be cut (hereinafter, the substrate is completely cut by cutting and referred to as "full cut"). In this case, the orthogonal scribe step, i.e., the step of forming a dicing groove along a dicing line orthogonal to the previous scribe line becomes extremely difficult.

An object of the present invention is to enable a desired cutting groove to be formed on a tempered glass whose surface has been strengthened relatively easily and stably.

Another object of the present invention is to easily cut a glass substrate into a desired shape.

The method for cutting a glass substrate according to the first aspect of the invention is a method of cutting a tempered glass having a reinforcing layer having a compressive stress on its surface, and includes a first step and a second step. The first step is to form an initial crack that exceeds the depth of the reinforcing layer on the surface of the tempered glass. In the second step, the initial crack is irradiated with laser light to be heated, and the heated region is cooled, and the crack is stretched along the line to be cut.

Here, an initial crack exceeding the depth of the reinforcing layer is formed on the surface of the tempered glass. Thereafter, the initial crack is irradiated with laser light to be heated, and the heated region is further cooled. Thereby the initial crack will extend along the line to be cut.

In the dicing method of the first aspect of the invention, in the first step, the depth of the initial crack is 1.14 times or more and 1.67 times or less the thickness of the reinforced glass reinforcing layer.

Here, when the depth of the initial crack is less than 1.14 times the thickness of the reinforcing layer of the tempered glass, the strengthening layer remains, and even if the heat treatment and the cooling treatment are performed by laser irradiation in the subsequent step, the crack does not occur. Stretching, it is difficult to form a cutting groove. On the other hand, when the depth of the initial crack exceeds 1.67 times the thickness of the reinforcing layer of the tempered glass, the crack may be unsatisfactory due to heating and cooling in the subsequent step, or may be extended in a direction different from the direction in which the cutting line is formed. It is difficult to form the desired cutting groove.

Therefore, in the present invention, the depth of the initial crack is set to be 1.14 times or more and 1.67 times or less the thickness of the reinforcing layer of the tempered glass. Therefore, the desired cutting groove can be stably formed.

The dicing method of the glass substrate according to the third aspect of the invention is the dicing method according to the second aspect of the invention, wherein in the first step, the initial crack is a depth not exceeding 5.4% of the total thickness of the tempered glass.

Even if the depth of the initial crack is 1.14 to 1.67 times as described above as the thickness of the reinforcing layer, when the thickness of the entire glass substrate is thin, when the initial crack is formed deep, cracks may not extend along the line to be cut.

Therefore, in the present invention, the depth of the initial crack is set to not exceed 5.4% of the total thickness of the tempered glass. Therefore, the desired cutting groove can be stably formed.

The method for cutting a glass substrate according to the fourth aspect of the invention is a method of cutting a tempered glass having a reinforcing layer having a compressive stress on its surface, and includes the first step and the second step. In the first step, the initial crack is formed on the surface of the tempered glass from the end surface of the glass substrate on the scanning side from the start of the cutting line to the inner side of the predetermined distance. The second step is to heat the laser beam by irradiating the laser light along the line to cut starting from the initial crack, in addition to the end region on the scanning side, and to cool the heated region so that the crack extends along the line to cut.

Here, an initial crack is formed on the surface of the tempered glass, and thereafter, the initial crack is irradiated with laser light to be heated, and the heated region is further cooled. Thereby the initial crack will extend along the line to be cut. At this time, the initial crack is formed on the end surface of the glass substrate on the scanning side from the start of the cutting line to the predetermined The tempered glass surface on the inner side is irradiated with laser light from the initial crack. That is, in the end region from the glass end surface on the scanning side from the start of the laser light to the initial crack, the heating by the laser light and the cooling treatment of the heating region are not performed.

As described above, since the end portion of the scanning light on the scanning side is not irradiated with the laser light, the natural separation of the substrate which is produced when the tempered glass is cut by a conventional method can be avoided. Therefore, the subsequent processing steps such as orthogonal cutting are easily performed.

In the dicing method according to the fourth aspect of the invention, in the dicing method of the fourth aspect of the invention, the reflective film of the reflected laser light is formed on the surface of the tempered glass at the end portion of the striated side at the beginning of the dicing line. . Further, the second step performs processing on the surface of the tempered glass on which the reflective film is formed.

When the region where the laser light is not irradiated is formed, it can be formed by synchronizing the ON and OFF control of the laser oscillation with the movement of the optical system or the like. However, as in the present invention, the second step can be more easily performed by forming a reflective film in a region where the laser light is not irradiated. Further, as the reflective film, a metal pattern film for reflecting laser light, an ITO (Indium Tin Oxide) film, or the like can be considered.

In the cutting method according to the fourth or fifth aspect of the invention, in the second step, in the second step, the end of the glass substrate on the scanning side from the end of the cutting line is reached to the inner side of the predetermined distance. In the portion region, the heating by the laser irradiation and the cooling of the heating region are stopped.

Here, the laser light is not irradiated on the end region on the scanning side and the end region on the scanning side. Therefore, it is possible to more reliably avoid the self of the substrate Separate.

The dicing method of the glass substrate according to the seventh aspect of the invention is the dicing method according to the sixth aspect of the invention, wherein the second step is to form a reflection of the reflected laser light by the end portion of the cutting line and the end portion of the scanning side. Implemented as a film.

Here, as described above, the second step can be performed more easily by forming the reflective film in the region where the laser light is not irradiated.

In the dicing method according to any one of the fourth to seventh aspects of the present invention, in the first step, the depth of the initial crack is 1.14 times or more the thickness of the reinforced layer of the tempered glass. And 1.67 times or less.

Here, as in the second invention, the desired cutting groove can be stably formed.

The dicing method of the glass substrate according to the ninth invention is the dicing method according to the eighth aspect of the invention, wherein in the first step, the initial crack is a depth not exceeding 5.4% of the total thickness of the tempered glass.

Here, as in the third invention, the desired cutting groove can be stably formed.

As described above, in the present invention, it is possible to form a desired cutting groove relatively easily and stably for the tempered glass whose surface has been strengthened.

Further, in another aspect of the invention, when the tempered glass having the surface strengthened is formed into a dicing groove, complete dicing can be prevented, and the glass substrate can be easily cut into a desired shape.

[Device configuration]

Fig. 1 is a view showing a schematic configuration of a cutting device for carrying out the method of the first embodiment of the present invention. The dicing apparatus 1 is, for example, a device that divides a mother glass substrate into a plurality of substrates used for an FPD (Flat Panel Display). Here, the glass substrate is mainly a chemically strengthened glass in which a reinforcing layer is formed on the surface. As described above, the chemically strengthened glass has a reinforcing layer having a compressive stress on the surface by ion exchange.

The dicing apparatus 1 includes an illuminating unit 2 that irradiates a laser beam toward the glass substrate G, a cooling unit 3, and a moving unit (not shown). The cooling unit 3 sprays a refrigerant source (not shown) through a nozzle 4 to form a cooling spot CP. The moving portion is moved between the glass substrate G and the nozzles 4 of the irradiation unit 2 and the cooling unit 3 along the planned cutting lines SL1 to SL5 set on the glass substrate G.

The illuminating unit 2 has a laser oscillator (for example, a CO ₂ laser) that irradiates the laser beam LB, and irradiates the laser beam LB as a beam spot LS through the optical system to the glass substrate G.

Further, although not shown in the drawings, an initial crack forming means is provided for forming an initial crack as a cutting starting point at the end portion of the glass substrate G. In the initial crack formation means, although a mechanical tool such as an indenter or a cutter wheel is used, an initial crack can be formed by laser ablation processing.

[Cutting method] - First embodiment -

First, as shown in Fig. 1, an initial crack TR as a cutting starting point is formed at the end of the glass substrate G by using an initial crack forming means such as a cutter wheel. At this time, the depth of the initial crack is a depth to the extent that the reinforcing layer having the compressive stress formed on the surface of the tempered glass is removed. Specifically, the thickness of the deep strengthening layer of the initial crack is 1.14 times or more and 1.67 times or less.

Next, the glass substrate G is irradiated with the laser beam LB by the irradiation unit 2. This laser beam LB is irradiated onto the glass substrate G as a beam spot LS. Further, the laser beam LB emitted from the illuminating unit 2 moves relative to the glass substrate G along the planned cutting line SL. The glass substrate G is heated to a temperature lower than the softening point of the glass substrate G by the beam spot LS. Further, the cooling portion CP is caused to follow the moving direction of the beam spot LS.

As described above, although the compressive stress is generated in the vicinity of the heated beam spot LS due to the irradiation of the laser beam LB, after the instant, the cooling portion CP is generated by the injection of the refrigerant, so that vertical cracks are formed. Crack) Effective tensile stress. By the tensile stress, the initial crack TR formed at the end portion of the glass substrate G is used as a starting point, and a vertical crack is formed along the line to cut SL, and a desired dicing groove is formed.

- Second embodiment -

First, as shown in Fig. 2, a glass substrate G on which the reflection films RC1 to RC4 reflecting the laser light are formed is formed in the four end portions. The reflection film RC1 is formed in an end region on the scanning start side where the laser beam is irradiated when the dicing groove is formed along the planned cutting lines SL1 and SL2 (hereinafter referred to as a dicing process). The reflective film RC2 is attached along the cutting line SL1, SL2 In the row cutting process, it is formed in an end region on the scanning side where the laser light is irradiated. Further, the reflective film RC3 is formed on the end portion of the scanning side on which the laser light is irradiated when the cutting process is performed along the cutting planned lines SL3, SL4, SL5, and the reflecting film RC4 is tied along the cutting line SL3, SL4. When SL5 performs the dicing process, it is formed in the end region on the scanning side where the laser light is irradiated. Further, the reflection films RC1, RC3 formed at the end regions on the scanning side are preferably 3 mm to 5 mm wide. Further, the reflection films RC2, RC4 formed on the end region on the side of the scanning side are preferably a width of 8 mm to 20 mm.

Next, an initial crack TR as a cutting start point is formed on the end portion of the glass substrate G by using an initial crack forming means such as a cutter wheel. At this time, the position of the initial crack is adjacent to the reflective film and is the inner side thereof. At this time, the depth of the initial crack is a depth to the extent that the reinforcing layer having the compressive stress formed on the surface of the tempered glass is removed. Specifically, the depth of the initial crack is set to be 1.14 times or more and 1.67 times or less of the thickness of the reinforcing layer.

Next, the glass substrate G is irradiated with the laser beam LB by the irradiation unit 2. This laser beam LB is irradiated onto the glass substrate G as a beam spot LS. Further, the laser beam LB emitted from the illuminating unit 2 moves relative to the glass substrate G along the respective cutting planned lines SL1 to SL5.

At this time, since the reflection films RC1 to RC4 are formed in the end regions on the scanning side and the end scanning side, the laser beam LB is reflected in the end regions without being irradiated to the glass substrate G. Therefore, the glass substrate G is not heated in the region where the reflection films RC1 to RC4 are formed.

In a region where the reflective films RC1 to RC4 are not formed, the glass substrate G is heated to a temperature lower than the softening point of the glass substrate G by the beam spot LS. degree. Further, the heated region is cooled by causing the cooling portion CP to follow the moving direction of the beam spot LS.

As described above, although the compressive stress is generated in the vicinity of the heated beam spot LS due to the irradiation of the laser beam LB, since the cooling portion CP is formed by the injection of the refrigerant in an instant, it is effective for forming the vertical crack. Tensile stress. By the tensile stress, the initial crack TR formed at the end portion of the glass substrate G is used as a starting point, and a vertical crack is formed along the line to cut SL, and a desired dicing groove is formed. Moreover, in the end region where the laser beam LB is not irradiated, even if the crack is not stretched or the crack is stretched, it is only a shallow region.

In the cutting method like the above, the crack does not extend from the initial crack to the full depth of the glass substrate G, and the substrate can be prevented from being naturally cut.

[Verification of cutting glass substrate] <Experimental example according to a conventional example>

Fig. 3 shows an example of a conventional method, that is, a case where laser heating and cooling are performed from the start end to the end end of the planned cutting line without forming a reflecting film. The substrate was a tempered glass having an overall thickness of 0.7 mm and a reinforcing layer thickness of 18 μm. In addition, the condition of the laser beam is a laser output of 200 W and a scanning speed of 200 mm/sec. Further, in Fig. 3, the end region of the glass substrate is not shown.

Figure 3 (a) shows the state after the cutting. Here, the cutting line (cutting groove) is in a state in which the entire depth of the substrate is not stretched (hereinafter, this state is described as "half cut"), and is indicated by a light color line in the drawing.

Fig. 3(b) shows the state after 5 seconds from the start of the cutting process. Here, the cutting line is from the start point side of the cut (the right side of the figure) to the vicinity of the center of the figure. It is completely cut (indicated by dark lines in the illustration).

Fig. 3(b) shows the state after 20 seconds from the start of the cutting process. Here, in all the parts shown in the drawing, the cutting line is completely cut (indicated by a dark line in the drawing).

In this way, the substrate is naturally cut (completely cut) when laser heating and cooling are performed from the start end to the end end of the line to cut.

<Examples and Comparative Examples>

The first table shows the results of verification including an example in which the cutting process was performed by the cutting method of the second embodiment. Here, the glass substrate to be used is the same as the comparative example shown in FIG. In addition, the conditions of the laser beam are also the same as those of the comparative example shown in FIG.

In the first table, "substrate Edge Start" means the end portion of the substrate on the cutting (scanning) start side, and "substrate edge end" means the end portion of the substrate on the cutting (scanning) end side. Further, "shadowing" means a reflective film. In addition, "n/5" means that the dicing process is performed five times, and the dicing process of n-times and half-cutting is not completed.

Further, in these examples, the initial crack is formed at a position on the inner side of the substrate which is cut (scanned) on the side of the substrate by 10 mm.

Furthermore, the shielding conditions are as follows.

"Substrate Edge Start": When the initial crack is shielded, since the crack is not stretched, the range of 5 mm from the end surface of the substrate on the cutting start (scanning) side is masked so as not to cover the initial crack.

"Substrate Edge End": a substrate that is shielded from the end side of the cutting (scanning) The range of the end face is 10 mm. Further, regarding the end side of the mask, when the width is 5 mm, the crack naturally extends to the end surface portion, and the portion is completely cut. Therefore, the shielding width at the end of the cutting (scanning) which is not completely cut is preferably 8 mm or more.

In the case of the reflective film, in the experiment of the first table, an aluminum foil tape was adhered to the surface of the substrate to cope with it.

Under the above conditions, the laser beam is irradiated from the end portion to the end portion of the glass substrate over the entire line.

<Summary of Experimental Examples and Comparative Examples>

As can be seen from the verification of the first table, when it is assumed that the laser beam is not irradiated at least to the end region on the cutting start side (the reflected laser beam is reflected), the half-cut cutting can be realized with a 40% probability. Further, when the cutting end side is shielded in addition to the mask cutting start side, the half cut cutting can be achieved with a probability of 100%.

On the other hand, when the cutting start side is not shielded and only the cutting end side is shielded, the probability of cutting by half cutting can be reduced to 20%. In addition, when the end regions of both sides are not shielded, although they are also shown in Fig. 3, the cutting of the half cut is not possible, and the cutting is completely cut off.

[Investigation on initial cracks]

Next, an experimental example regarding the depth of the initial crack is shown below.

<Experimental Example 1>

Fig. 4 and Fig. 2 are Experimental Example 1 showing the formation of a dicing groove for a tempered glass having an overall thickness of 0.55 mm and a thickness of the reinforcing layer of 18 μm. Specifically, Fig. 4 and Fig. 2 show the relationship between the pressing load of the glass (indenter) and the groove depth at the time of forming the initial crack, and the subsequent laser heating and cooling treatment are performed. The result of the cutting.

At this time, the laser output for heat treatment was 200 W, and the processing speed was 230 mm/sec. Further, the cooling condition is such that a cooling nozzle is disposed at a position where the rear end of the beam is 4 mm in height, and cooling water and air are sent to a portion heated at the beam spot.

From the experimental example 1, it is understood that if the groove depth of the initial crack is 19 to 30 μm (1.05 to 1.67 times the thickness of the reinforcing layer), the desired cutting groove can be formed along the line to be cut. Further, it was found that cracks could not be surely stretched (unstable) when the groove depth was less than 19 μm, and cracks were generated when it exceeded 30 μm, and cracks were formed outside the line to be cut.

Further, an example of the groove depth of the initial crack is shown in Fig. 5. As shown in FIG. 5, the depth until the deepest portion of the predetermined area is reached is referred to as "ditch depth", and a portion of the crack that reaches the deep portion sharply is ignored.

[Experimental Example 2]

Fig. 6 and Fig. 3 show Experimental Example 2 in which a dicing groove was formed for a tempered glass having an overall thickness of 0.7 mm and a thickness of the reinforcing layer of 21 μm. The relationship between the horizontal axis and the vertical axis shown in the figure is the same as in Fig. 4. Further, at this time, the laser output for the heat treatment was 200 W, and the processing speed was 170 mm/sec. Further, the cooling conditions were the same as in Experimental Example 1.

From the experimental example 2, it is understood that if the groove depth of the initial crack is 24 to 50 μm (1.14 to 2.38 times the thickness of the reinforcing layer), a desired cutting groove is formed along the line to be cut. Further, it was found that cracks could not be surely stretched (unstable) when the groove depth was less than 24 μm, and cracks were generated when it exceeded 50 μm, and cracks were formed outside the line to be cut. Further, if the pressing load is about 6 to 24 N, the desired cutting groove can be formed even if the groove depth exceeds 50 μm, but when only the groove depth is emphasized, the groove depth of the initial crack is preferably about 24 to 50 μm.

[Experimental Example 3]

Fig. 7 and Fig. 4 show Experimental Example 3 in which a dicing groove was formed for a tempered glass having an overall thickness of 1.1 mm and a thickness of the reinforcing layer of 34 μm. The relationship between the horizontal axis and the vertical axis shown in the figure is the same as in Fig. 4. Further, at this time, the laser output for the heat treatment was 200 W, and the processing speed was 170 mm/sec. Further, the cooling conditions were the same as in Experimental Example 1.

As is apparent from the experimental example 3, if the groove depth of the initial crack is 24 to 60 μm (0.71 to 1.76 times the thickness of the reinforcing layer), the desired cutting groove can be formed along the line to be cut. Moreover, it can be known that when the crack is too shallow when the groove depth is too shallow (unstable), the crack stretching is unstable when it exceeds 60 μm. Further, in the same manner as in Experimental Example 2, if the pressing load is about 6 N to 24 N, the desired cutting groove can be formed even if the groove depth exceeds 60 μm, but when only the groove depth is emphasized, the groove depth of the initial crack is about 24 to 60 μm is more appropriate.

[to sum up]

From the above, it can be seen that the depth of the initial crack is preferably 1.14 times or more and 1.67 times or less the thickness of the reinforcing layer of the tempered glass in order to form a desired dicing groove along the line to be cut. Further, it is also known that the depth of the initial crack is preferably 30 μm (5.5%) or less when the thickness of the glass sheet is 0.55 mm, 50 μm (7.1%) or less when the thickness of the glass sheet is 0.7 mm, and the thickness of the glass sheet is 1.1 mm. The time is 60 μm (5.4%) or less. In this case, the depth of the initial crack is preferably 5.4% or less of the thickness of the glass sheet.

[feature]

(1) In the second embodiment, since the laser beam is irradiated to the end portion on the scanning side and the scanning end side of the cutting line, the substrate can be half-cut and the natural separation of the substrate can be avoided. Therefore, it is easy to perform a processing step after orthogonal cutting or the like.

(2) In the second embodiment, it is easy to form a reflection film on both end portions of the substrate in order not to be irradiated by the laser beam. The ground forms a non-irradiated area of the laser beam.

(3) When the initial crack is formed, the depth of the initial crack is set to be 1.14 times or more and 1.67 times or less the thickness of the reinforcing layer of the tempered glass, so that the desired dicing groove can be stably formed.

(4) Since the depth of the initial crack is set to 5.4% or less of the total thickness of the tempered glass, it is possible to suppress the crack from spreading in an unexpected direction.

[Other Embodiments]

The present invention is not limited to the above embodiments, and various modifications and changes can be made without departing from the scope of the invention.

In the second embodiment, the non-irradiation region of the laser beam is formed by forming the reflection film on the substrate. However, the laser beam may be turned off at each end region to form a non-irradiation region of the laser beam.

1‧‧‧ cutting device

2‧‧‧ Department of Irradiation

3‧‧‧ Cooling Department

4‧‧‧ nozzle

CP‧‧‧ Cooling parts

G‧‧‧glass substrate

LB‧‧‧Laser beam

LS‧‧‧beam point

RC1, RC2, RC3, RC4‧‧·reflective film

SL1, SL2, SL3, SL4, SL5‧‧‧ cutting line

TR‧‧‧ cutting starting point (initial crack)

Fig. 1 is a schematic configuration diagram of an apparatus for carrying out the cutting method according to the first embodiment of the present invention.

Fig. 2 is a schematic configuration diagram of an apparatus for carrying out the cutting method according to the second embodiment of the present invention.

Fig. 3 is a view showing a pattern in which the substrate is naturally separated when the cutting is performed by a conventional method.

Fig. 4 is a view showing the relationship between the pressing load and the initial crack for forming the initial crack of the tempered glass having a thickness of 0.55 mm, and the cutting result.

Fig. 5 is an enlarged cross-sectional view showing a part of the tempered glass in which the initial crack is formed.

Fig. 6 is a view showing the relationship between the pressing load and the initial crack for forming the initial crack of the tempered glass having a thickness of 0.7 mm, and the cutting result.

Fig. 7 is a view showing the relationship between the pressing load and the initial crack for forming the initial crack of the tempered glass having a thickness of 1.1 mm, and the cutting result.

1‧‧‧ cutting device

2‧‧‧ Department of Irradiation

3‧‧‧ Cooling Department

4‧‧‧ nozzle

CP‧‧‧ Cooling parts

G‧‧‧glass substrate

LB‧‧‧Laser beam

LS‧‧‧beam point

SL‧‧‧ cutting line

TR‧‧‧ cutting starting point (initial crack)

Claims (7)

A method for cutting a glass substrate, wherein the tempered glass having a reinforcing layer having a compressive stress is cut, comprising: a first step of removing a strengthening layer on the surface of the tempered glass to form an initial crack; and The step of heating the laser beam by irradiating the initial crack to the initial crack, and cooling the heated region to extend the crack along the line to be cut; in the first step, the depth of the initial crack is the thickness of the strengthened layer of the strengthened glass. It is 1.14 times or more and 1.67 times or less. The method for cutting a glass substrate according to the first aspect of the invention, wherein, in the first step, the initial crack is a depth not exceeding 5.4% of the total thickness of the tempered glass. A method for cutting a glass substrate is a method of cutting a tempered glass having a reinforcing layer having a compressive stress on a surface thereof, the method comprising: forming a first crack by forming an initial crack on an end surface of a glass substrate on a scanning side from a line to be cut a step of removing the tempered glass on the inner side of the predetermined distance; and a second step of heating the heated area by irradiating the laser light along the line to be cut starting from the initial crack as described above, in addition to the end portion on the scanning side. And causing the crack to extend along the line to be cut; the depth of the initial crack in the first step is tempered glass The thickness of the reinforcing layer is 1.14 times or more and 1.67 times or less. The method for cutting a glass substrate according to the third aspect of the invention, wherein the surface of the tempered glass is formed with a reflection film for reflecting laser light at an end portion on the scanning side at the start of the line to cut, the second The step is performed on the surface of the tempered glass on which the aforementioned reflective film is formed. The method of cutting a glass substrate according to the third aspect of the invention, wherein the end portion of the glass substrate on the scanning side from the end of the cutting line to the inner side of the predetermined distance is in the second step. In the area, the heating by the laser irradiation and the cooling of the heating area are stopped. The method for cutting a glass substrate according to the fifth aspect of the invention, wherein, in the surface of the tempered glass, a reflection of the reflected laser light is formed on the start scanning side and the end side of the scanning planned line, respectively. In the film, the second step is performed on the surface of the tempered glass on which the reflective film is formed. The method of cutting a glass substrate according to claim 3, wherein in the first step, the initial crack is a depth not exceeding 5.4% of the total thickness of the tempered glass.