JP7164136B2 - Laser cutting method - Google Patents

Description

The present disclosure relates to a laser cutting method for cutting minerals or the like by irradiating laser light.

For example, sapphire crystal is characterized by transparency, hardness second only to diamond, chemical stability, and good thermal conductivity. Therefore, processed sapphire is used in various industrial fields such as watch window materials and semiconductor substrate materials.
In addition, since sapphire crystals are brittle, high-precision processing that suppresses material chipping requires high-rigidity processing equipment. There is a problem that the cost required for processing, etc. is high, such as that wear is likely to progress.
At present, the means of dividing sapphire with a thickness of several millimeters or more is limited to machining, and there is a need to expand the range of thicknesses that can be processed and to develop a low-cost processing method.

When cutting a thin sapphire plate having a thickness of 1 [mm] or less, laser processing is used in addition to mechanical processing.
For example, there is a laser processing method of irradiating sapphire or the like with a laser beam (solid-state UV laser) having a wavelength of 355 [nm] to generate cracks in the sapphire or the like (for example, Patent Document 1).
In this laser processing method, a pulsed laser beam is emitted from a light source and focused inside an object to be processed such as sapphire using a convex lens. By focusing the pulsed laser beam inside the object, cracks are generated between the front and back surfaces of the object to cut the object.

In addition, there is a laser processing method in which a pulsed laser beam with a wavelength of 355 [nm] is focused and irradiated above the surface of an object to be processed such as sapphire to form V-shaped damage on the surface of the object to be processed (for example, patent Reference 2).
In this laser processing method, a pulsed laser beam emitted from a light source is condensed in front of an object to be processed using an objective lens, and this laser beam is scanned along a planned processing position to cause damage suitable for cutting. I am letting
When laser light is focused, plasma is generated at the focal position where the spatial energy density is high. In this laser processing method, the laser beam is condensed in front of the object to be processed so that plasma does not cause unintended damage to the object to be processed.

JP-A-2005-288503 Japanese Patent Application Laid-Open No. 2006-114786

Sapphire has a Mohs hardness of 9, and expensive machining tools such as high-rigidity NC machining machines and diamond tools are indispensable for high-precision machining. In addition, each of the tools described above wears out due to machining operations, and must be replaced after being used for a certain period of time.
In addition, when processing sapphire by machining, a grinding fluid is required to accelerate processing and cool the processing tool, and the grinding fluid must also be replaced after a certain period of use.
Since sapphire is a hard and brittle material, it is necessary to suppress damage due to mechanical stress during processing, and multiple processes such as rough processing and finishing processing are essential. Therefore, processing of sapphire may take several hours to several tens of hours.
Also, when cleaving sapphire using a laser beam, unless the laser beam is controlled with high precision, it is difficult to cause appropriate damage at the position to be processed, and the cleaving can be performed as desired. be unable to do so.

In addition, there are the following problems when applying laser processing to sapphire.
Sapphire has low light absorption in a wide wavelength range of 0.3 to 4.5 [μm], and in order to perform laser processing in the above wavelength range, high energy or high peak power short pulse laser light etc. is required. A laser light source for output is required.
When the above-described short-pulse laser light is used, the processing amount per hour is very small, so it is not suitable for cutting a material having a thickness of several [mm].

In order to cut the sapphire having the thickness as described above, an initial groove serving as a processing starting point is provided in advance in the sapphire. An absorptive laser beam (having a wavelength that is easily absorbed by sapphire) is irradiated along the grooves to generate heat in the irradiated portion and generate thermal stress. Technological development is being carried out in which this thermal stress causes cracks to grow along the initial grooves, thereby breaking the sapphire.
In this technique, since the crack is propagated along the initial groove to perform the cutting, the material removal allowance (for example, removal allowance of several hundred μm) required in conventional machining is not required. In addition, machining tools, grinding fluid, etc. are no longer required, so a significant reduction in machining costs and shortening of machining time can be realized. In this technique, it is possible to cut sapphire with a thickness of 10 [mm] by using a CO ₂ laser beam and providing an initial groove with a groove depth of several tens [μm] in sapphire.

For example, the wavelength of CO ₂ laser light is 9.6 to 10.6 [μm]. Further, sapphire has a light absorptivity of 100[%] at the above wavelength. Therefore, when processing thick sapphire, if a CO ₂ laser beam with a power necessary for cutting is applied, the sapphire may be unexpectedly cracked or melted.
In addition, since the CO ₂ laser light is absorbed on the surface of sapphire, the temperature rise in the thickness direction of sapphire is also wide, so the quality of processing (for example, the perpendicularity of the cutting part and the presence or absence of undulations) is low. Become.

The present disclosure has been made to solve the above problems, and provides a laser cutting method that suppresses the construction time and the like and improves the quality of the cutting process.

A laser cutting method according to the present disclosure includes a first step of forming a minute defect in a cutting object, and a second step of oscillating a first laser beam having a light absorption rate of 1% or more and less than 50% of the cutting object. a third step of irradiating the micro defect with the first laser beam; and a thermal stress generated by the irradiation of the first laser beam, the interior of the cutting object starting from the micro defect. and a fourth step of cleaving the object to be cut by growing a crack in the cleaving object, and the third step is characterized by irradiating the first laser beam with a laser output of 60 [W] or more. do.

In the first step, the surface of the object to be cut is subjected to a polishing treatment, and an initial groove that serves as a starting point for the propagation of the crack and guides the propagation of the crack is formed on the surface of the object to be broken by machining or the second step. The minute defects are formed by processing using a laser beam.

In the first step, the surface of the object to be cut is subjected to a grinding process, and an initial groove that serves as a starting point for the propagation of the crack and guides the propagation of the crack is formed on the surface of the object to be broken by machining or the second step. The minute defects are formed by processing using a laser beam.

In the first step, the surface of the object to be cut is subjected to a grinding process to form minute scratches on the surface of the object to be cut, which guide the crack growth, thereby forming the minute defects. do.

In the first step, the microdefects are formed by processing using a second laser beam (short pulse laser) to provide starting points for crack growth and initial grooves for guiding the crack growth on the surface of the object to be cut. and in the third step, the first laser beam is irradiated following the irradiation of the second laser beam.

Further, in the fourth step, when the crack is propagated, a temperature adjustment part provided in a holding mechanism part that holds the cutting object is used so that the crack propagates in the part where the cutting is performed. It is characterized in that the temperature of the cutting object held by the holding mechanism is adjusted.

In addition, the fourth step includes a fifth step of sweeping the first laser beam and propagating the crack using a sweeping mechanism portion that moves a holding mechanism portion holding the cutting object; When propagating the crack in the fifth step, using a temperature adjustment unit provided in the holding mechanism unit that holds the cutting object and a laser output adjustment unit that adjusts the laser output of the first laser light and a sixth step of adjusting the temperature of the object to be cut held by the holding mechanism and adjusting the output of the first laser beam so that the crack develops in the portion to be cut. , the sixth step, wherein the control unit controls the sweep mechanism unit, the temperature adjustment unit, and the laser output adjustment unit to perform preset cooperative operations or to operate independently of each other. It is characterized by

Further, the third process is characterized by irradiating the first laser light of a parallel beam.

The first step is characterized by forming the minute defects in sapphire, which is the object to be cut, and the second step is by irradiating a CO laser beam as the first laser beam.

According to the present disclosure, sapphire can be excellently cleaved at desired portions.

BRIEF DESCRIPTION OF THE DRAWINGS It is explanatory drawing which shows schematic structure of the laser cutting apparatus of the Example using the laser cutting method of this indication. 1. It is explanatory drawing which shows the cutting using the laser cutting apparatus of FIG. FIG. 4 is an explanatory diagram showing laser light transmission characteristics of a sapphire plate; FIG. 4 is an explanatory diagram showing light absorption when a sapphire plate is irradiated with a CO ₂ laser beam; FIG. 4 is an explanatory view showing cracks that occur when a sapphire plate is irradiated with a CO ₂ laser beam (when the sapphire plate is excessively irradiated with the first laser beam). FIG. 4 is an explanatory diagram showing light transmission when a CO laser beam is applied to a sapphire plate; FIG. 4 is an explanatory view showing cracks that occur when a CO laser beam is applied to a sapphire plate;

An embodiment of the invention will be described below.
(Example)
FIG. 1 is an explanatory diagram showing a schematic configuration of a laser cutting apparatus of an embodiment using the laser cutting method of the present disclosure.
The laser cleaving apparatus of FIG. 1 includes a holding mechanism section 101 that holds the sapphire plate 1 to be cleaved, and a temperature adjustment section 102 that adjusts the temperature of the sapphire plate 1 . This laser cutting apparatus also includes a laser light source 103 (first laser light source) for irradiating the sapphire plate 1 with the laser beam 3, and a sweeping mechanism 104 for moving the holding mechanism 101 and the like. The laser light source 103 includes a laser output adjustment section 103a that adjusts the intensity (laser output) of the laser beam 3 under the control of the control section 105, which will be described later.
Further, the laser cutting device has a laser optical system 106 on the output side of the laser light source 103 (near the portion where the laser beam 3 is output). The laser optical system 106 has a function of shaping the laser beam 3 incident from the laser light source 103 into a beam shape for irradiating the sapphire plate 1 .
This laser cutting apparatus also includes a control section 105 that controls the temperature adjustment section 102 , the laser output adjustment section 103 a and the sweep mechanism section 104 .

The laser cutting apparatus described here is configured, for example, to cut a plate-like sapphire plate 1, but the laser cutting method of the present invention is not limited to plate-like sapphire, and any shape can be used. of sapphire can be cleaved.
In addition, the laser cutting method of the present invention is not limited to the cutting of sapphire. It can be cleaved in the same way as sapphire by irradiating with a laser beam.

The holding mechanism part 101 is configured to support the side surface, the bottom surface, the bottom end, or the like of the sapphire plate 1 and hold the sapphire plate 1 while exposing the surface of the sapphire plate 1 upward.
The temperature adjustment unit 102 is provided in the holding mechanism unit 101, for example, and adjusts the temperature of the sapphire plate 1 supported and fixed to the holding mechanism unit 101. Specifically, the temperature of the sapphire plate 1 as a whole is excessively increased by laser light irradiation. It is configured to suppress high temperature (for example, to cool any portion).
A laser light source 103 oscillates a laser beam (first laser beam) used for laser cutting of the sapphire plate 1, and a laser optical system 106 is configured with, for example, a focusing lens so as to irradiate with an arbitrary beam shape. It is

A laser light source 103 is a CO laser oscillator that outputs laser light having a wavelength described later. Further, the laser light source 103 illustrated here is configured to output a laser beam 3 having a circular beam cross section.
The laser beam 3 has an intensity suitable for cleaving the sapphire plate 1 by the laser optical system 106, and has an arbitrary beam cross-sectional shape such as the above-mentioned circular shape or knife shape that can obtain a temperature distribution suitable for cleaving. It is molded to be Also, the laser beam 3 is shaped by the laser optical system 106 so as to obtain an arbitrary energy distribution shape such as a Gaussian shape or a top hat shape.
The laser beam 3 illustrated here has a shape that converges at an arbitrary focal position, but it may be a parallel beam shape (parallel beam) that does not converge, or a beam shape that diverges in the irradiation direction. good.

The sweep mechanism unit 104 moves the holding mechanism unit 101 in an arbitrary direction (development direction of cracks 21 described later) so that the laser beam 3 emitted from the laser light source 103 is swept over the surface of the sapphire plate 1. is configured as
The control unit 105 includes an electronic device such as a processor, and controls the operation of the temperature adjustment unit 102, the operation of the sweep mechanism unit 104, and the operation of the laser light source 103 in accordance with arbitrary operation settings previously made by a user or the like. It is configured to control operations in cooperation with each other.
Also, the control unit 105 may be configured to control the above operations in cooperation with each other in any combination.
In addition, the control unit 105 operates the temperature adjustment unit 102, the sweep mechanism unit 104, and the laser light source 103 (output from the laser output adjustment unit 103a) according to arbitrary operation settings previously made by a user or the like. adjustment) may be configured to be independently controlled.
Further, the control unit 105 may be configured to allow a user or the like to select and set either the control of the cooperative operation or the control of the independent operation.

Note that the sapphire plate 1 is subjected to a polishing process, a grinding process, or the like before it is held in the laser cutting apparatus of FIG. 1 so as to have minute defects. Here, the description of the configuration, operation, etc. of a device for applying a polishing process, a grinding process, or the like to the sapphire plate 1 to form microdefects will be omitted.

Next, the operation will be explained.
In the laser cleaving method of the present invention, before the sapphire plate 1 is installed and fixed to the laser cleaving apparatus shown in FIG.
As the minute defects, for example, a portion of the sapphire plate 1 to be cleaved is subjected to a polishing process using a polishing apparatus or the like to form a polished portion having minute polishing scratches.
In addition, as a micro defect, a predetermined laser beam (second laser light) to form an initial groove 2, which will be described later. The portion of the initial groove 2 guides the progress of the crack that occurs when cutting.

Alternatively, for example, the portion of the sapphire plate 1 to be cleaved is ground using a grinding device or the like to form a ground portion having a plurality of fine grinding scratches. In addition, the edge of the portion to be cut (ground portion) of the sapphire plate 1 is irradiated with a predetermined laser beam (second laser beam) using a machine tool or the like or using an appropriate laser processing device or the like. However, an initial groove 2, which will be described later, may be provided. The portion of the initial groove 2 guides the progress of the crack that occurs when cutting.

Alternatively, for example, without providing the initial groove 2 or the like, a plurality of fine grinding scratches that can cause splitting using a grinding device or the like are provided, and they serve as starting points for cracks when performing splitting, and also provide cracks. You may make it induce|guide|derive progress of.
In addition, as a micro defect of the sapphire plate 1, a machine tool or an appropriate laser processing device (second laser light source) is used for the edge of the sapphire plate 1 without providing the above-mentioned polished portion or ground portion. The initial groove 2 may be provided by

FIG. 2 is an explanatory view showing cutting using the laser cutting apparatus of FIG. The sapphire plate 1 shown in FIG. 2 has already been subjected to a process for providing microdefects, and for example, initial grooves 2 are provided as microdefects.
FIG. 2 shows thermal stress and the like generated in the sapphire plate 1 when the initial grooves 2 provided in the sapphire plate 1 are irradiated with the laser beam 3 (first laser beam) from the laser light source 103 . be.
In FIG. 2, the portion of the sapphire plate 1 irradiated with the laser beam 3 is shown as an enlarged area A, and the portion of the area A in which the initial grooves 2 are formed is shown as an enlarged area B. In the drawing, an arrow 4 indicates the direction in which the sapphire plate 1 held by the holding mechanism 101 moves as the sweeping mechanism 104 operates.

After holding the sapphire plate 1 provided with the initial grooves 2 in the holding mechanism 101 of the laser cutting device, the laser light source 103 is operated to oscillate a laser beam in which the light absorption rate of the sapphire plate 1 becomes a value described later. (second process). The laser optical system 106 shapes the passing laser light into an arbitrary beam shape, and irradiates this as a laser beam 3 to the minute defect (initial groove 2) of the sapphire plate 1 (third process).
In the area A of the sapphire plate 1, the position (beam spot 3a) irradiated with the laser beam 3 generates heat, and the portion heated by this heat becomes a compressive stress field 10 where compressive stress acts due to thermal expansion. Around the compressive stress field 10, there is a portion with a temperature lower than that of the compressive stress field 10, and this portion becomes a tensile stress field 11 in which a tensile stress 11a acting in the opposite direction of the compressive stress is generated. When the sapphire plate 1 is irradiated with the laser beam 3, thermal stress (compressive stress, tensile stress 11a) is generated as described above.

When the sapphire plate 1 is irradiated with the laser beam 3 so that the beam spot 3a is positioned near the initial groove 2 to generate thermal stress, the tensile stress 11a acts on the initial groove 2, starting from the initial groove 2. The crack grows in the direction indicated by the arrow 12 (extending direction of the initial groove 2).
When the laser beam 3 is applied to the sapphire plate 1 as described above and the sapphire plate 1 is swept, for example, in the direction of the arrow 4, cracks progress from the initial grooves 2 in the opposite direction of the arrow 4, and the sapphire plate 1 is broken. performed (fourth step).

FIG. 3 is an explanatory diagram showing laser light transmission characteristics of a sapphire plate. In this figure, the horizontal axis indicates the wavelength λ of laser light, and the vertical axis indicates the transmittance of each wavelength λ transmitted through an arbitrary sapphire plate (sapphire single crystal). FIG. 3 shows laser light transmission characteristics of an arbitrary sapphire single crystal with a thickness of 0.5 [mm], for example.
A sapphire single crystal transmits 80 [%] or more of light having a wavelength λ of approximately 5 [μm] or less. That is, it absorbs everything.

FIG. 4 is an explanatory diagram showing light absorption when the sapphire plate 1 is irradiated with the CO ₂ laser beam 30 .
_The CO ₂ laser beam has, for example, a wavelength λ of 10.6 [μm] as shown in FIG.

FIG. 5 is an explanatory diagram showing cracks that occur when the sapphire plate 1 is irradiated with the CO ₂ laser beam 30 . For example, when the sapphire plate 1 is irradiated with a CO ₂ laser beam 30 having a circular beam cross section (irradiated toward the initial groove 2), a circular beam spot, that is, a compressive stress field 10 is generated, and this portion heats up. As described above, the CO ₂ laser beam 30 is completely (100%) absorbed by the surface of the sapphire plate 1, so that the circular portion of the surface generates heat and the temperature distribution spreads from this portion.
When a strong output CO ₂ laser beam 30 is irradiated to break the thick sapphire plate 1, the temperature distribution spreads from the beam spot on the surface of the sapphire plate 1, and the thermal stress distribution (compressive stress field 10 and tensile stress The range of the field 11 ) changes from a circular shape on the surface of the sapphire plate 1 , and also diffuses in the direction perpendicular to the extending direction of the initial grooves 2 .

FIG. 5 shows the distribution of thermal stress on the surface of the sapphire plate 1 when the irradiation of the first laser beam (for example, the CO ₂ laser beam 30) is excessive. Also, the temperature distribution and thermal stress distribution diffuse. The distribution of the thermal stress inside the thickness of the sapphire plate 1 is diffused from the surface of the sapphire plate 1 and does not follow the initial grooves 2 .
That is, when the initial groove 2 is irradiated with the CO ₂ laser beam 30, the thermal stress generated at the position of the initial groove 2 (and its surroundings) is the initial The distribution along the groove 2 is not obtained. Therefore, the crack 20 generated by this thermal stress is more likely to grow in an unexpected direction without being guided to the initial groove 2 .

For example, when the sapphire plate 1 having a thickness of 5 [mm] is irradiated with the CO ₂ laser beam 30 whose output is increased according to the thickness (for cutting), the thermal stress generated in the sapphire plate 1 is Since the distribution has a collapsed (diffused) shape as described above, cracks develop in an unexpected direction, and many undulations occur in the shape of the fractured portion.
Further, for example, when the sapphire plate 1 having a thickness of 15 [mm] is irradiated with a CO ₂ laser beam 30 whose output is increased according to the thickness (for cutting), the irradiated portion melts. or chipping occurs.

FIG. 6 is an explanatory diagram showing light transmission when the sapphire plate 1 is irradiated with the laser beam 3 .
The laser cutting apparatus of this embodiment has a CO laser light source as the laser light source 103, and irradiates the sapphire plate 1 with a laser beam 3 having a wavelength λ of about 5.5 [μm].
For example, CO laser light with a wavelength λ of 5.5 [μm] has a light absorption rate as low as about 10 [%] in the sapphire plate 1, which is about 1/10 of CO ₂ laser light.
When the sapphire plate 1 is irradiated with a laser beam 3 having a wavelength λ of 5.5 [μm], the laser beam 3 penetrates through the thickness of the sapphire plate 1 (at a distance d from the surface of the sapphire plate 1) as shown in FIG. That is, thermal stress can be generated also in the interior between the front surface and the back surface of the sapphire plate 1 .
In other words, when the object to be cut is, for example, the sapphire plate 1, a CO laser beam with a wavelength λ of 5.5 [μm], which makes the light absorption rate of the sapphire plate 1 about 10 [%] as described above. is preferred.
A suitable laser beam (first laser beam) used in the present invention has a wavelength λ at which the light absorption rate of the object to be cut is 1% or more and less than 50%.
Such a laser beam with a wavelength λ is transmitted from the surface of the cutting object to a suitable position (depth) toward the inside of the thickness of the cutting object, and the portion irradiated with the laser beam (desired (limited range of That is, when a laser beam having the above light absorption rate is irradiated, cracks can be generated within a limited range (desired position) within the thickness of the object to be cut.

FIG. 7 is an explanatory diagram showing cracks that occur when the sapphire plate 1 is irradiated with the laser beam 3 .
When the sapphire plate 1 is irradiated with a laser beam 3 having a circular beam cross-sectional shape after passing through a laser optical system 106 from a laser light source 103 (irradiated toward the initial grooves 2), a beam spot 3a, that is, The circular part heats up.
More specifically, since the laser beam 3 penetrates through the thickness of the sapphire plate 1 as described above, when the sapphire plate 1 is irradiated with the laser beam 3 having an intensity (laser output) that enables cutting, the circular shape of the surface is irradiated. A substantially cylindrical or conical portion extending in the thickness direction from the shaped portion generates heat.

The laser beam 3 has a wavelength λ with low light absorption as described above. Therefore, the temperature rise of the sapphire plate 1 irradiated with the laser beam 3 is suppressed, resulting in a uniform temperature distribution. occur. That is, a generally cylindrical or conical thermal stress field is generated.
When irradiating the sapphire plate 1 with the laser beam 3 (CO laser light), the temperature rise can be suppressed in areas other than the irradiation position of the sapphire plate 1 compared to the case of irradiating with the CO ₂ laser beam 30. . That is, it becomes possible to generate a thermal stress field only at the location where the cutting is to be performed.

When the initial groove 2 is irradiated with the laser beam 3, a thermal stress field is generated so as to envelop the portion irradiated with the laser beam 3 (part of the initial groove 2), and the laser beam 3 traces the initial groove 2. is swept (operating the sweep mechanism 104), the thermal stress field moves along the initial groove 2, and the crack 21 progresses in the extending direction of the initial groove 2.
Note that the initial groove 2 illustrated in FIG. 7 is extended to the portion where the crack 21 is propagated, and is not formed only at the edge portion of the sapphire plate 1 .

In order to cause the cracks 21 to follow the initial grooves 2, in other words, to break the sapphire plate 1 by propagating the cracks 21 along the extension direction of the initial grooves 2, for example, a laser in the laser light source 103 A laser beam 3 with an output of 60 [W] or more is irradiated.
When the laser beam 3 with a laser output lower than 60 [W] is irradiated, no thermal stress that causes cracks occurs at the irradiated position of the object to be cut, such as the sapphire plate 1 . In addition, it takes a considerable amount of time to generate a thermal stress strong enough to generate cracks. If the irradiation time becomes long in this way, the heat generated at the irradiation position of the laser beam 3 diffuses and conducts over a wide area in the object to be cut such as the sapphire plate 1 . That is, the thermal stress is generated even in the portion where the crack should not be generated, and it becomes difficult to propagate the crack in the desired direction.
For example, when the laser beam 3 with a laser output of 50 [W] was irradiated, no cracks occurred in the sapphire plate 1 with a thickness of 6 to 15 [mm].
Therefore, using the laser beam 3 with a laser output of 60 [W] or more, the irradiation time to the same part of the object to be cut (sapphire plate 1) is shortened, and heat (temperature distribution) is applied to the part where the crack 21 is not generated. Diffusion is suppressed, the accuracy of cutting the sapphire plate 1 at a desired position is increased, and the processing quality of the cut portion is improved. In other words, a laser beam 3 with a laser output of 60 [W] or more is used so that a crack is generated at a desired position before other parts are heated. In addition, this laser output is suppressed in relation to the sweep speed (irradiation time) and the like to the extent that the object to be cut such as the sapphire plate 1 is not excessively irradiated.

For example, an initial groove 2 is provided (extended) in advance on a sapphire plate 1 having a thickness of 15 [mm], and when a laser beam 3 is irradiated so as to follow the initial groove 2, the initial groove 2 is followed. It has been confirmed that the sapphire plate 1 can be cleaved without the occurrence of damage such as unexpected cracks due to cracks 21 generated in the sapphire plate 1 .
Further, for example, when the laser beam 3 is irradiated to the sapphire plate 1 having a thickness of 20 [mm] in which the initial grooves 2 are not provided, a crack 21 is generated following the trajectory of the laser beam 3 sweeping, resulting in an unexpected crack. It has been confirmed that the sapphire plate 1 can be cleaved without causing such damage.

When the sapphire plate 1 is cleaved by irradiating the laser beam 3 (fourth process), the temperature control unit 102 is operated to apply heat to the sapphire plate 1 heated by the irradiation of the laser beam 3 to a temperature suitable for cleaving or crack development. The temperature of the sapphire plate 1 is adjusted so as to produce a gradient.
Specifically, in order to generate the crack 21 only in the part to be cut (to prevent the crack 21 from growing in a part other than the part to be cut or to prevent an unexpected crack from occurring), for example, the sapphire plate 1 is Cooling water or the like is brought into contact with the portion, and the temperature is adjusted so that the thermal temperature gradient (thermal stress) inside the sapphire plate 1 is in an optimum state.

When breaking the sapphire plate 1, the sweeping mechanism unit 104 is operated to move the holding mechanism unit 101 in a predetermined direction to move the sapphire plate 1 held by the holding mechanism unit 101, and the sapphire plate 1 is irradiated. The laser beam 3 is swept (fifth process).
Therefore, the operation of the sweeping mechanism unit 104 and the operation of the temperature control unit 102 are coordinated so that the fracture of the sapphire plate 1 or the crack 21 develops satisfactorily (sixth process).

Specifically, the temperature adjustment unit 102 or the holding mechanism unit 101 is provided with a temperature sensor or the like for measuring the temperature of the sapphire plate 1 held by the holding mechanism unit 101, and a signal ( A signal indicating the temperature of the sapphire plate 1 ) is input to the control unit 105 . Further, in the controller 105, a desired operation or control pattern or the like (for example, operation control for favorably propagating the sapphire plate 1 or the crack 21) is set in advance. The above-mentioned control patterns and the like set in the control unit 105 include, for example, adjustment of the intensity (laser output) of the laser beam 3 by the laser output adjustment unit 103a.
Further, the control unit 105 may be set so that the sweep mechanism unit 104, the temperature adjustment unit 102, and the laser output adjustment unit 103a perform arbitrary independent operations.

After the sapphire plate 1 is held by the laser cutting device, the control unit 105 acquires an output signal from a temperature sensor or the like and detects the temperature of the sapphire plate 1 along with the start of irradiation with the laser beam 3 . Further, when the irradiation of the laser beam 3 is started, the operation control of the sweep mechanism unit 104 is started. , the sweep mechanism 104 is controlled to start sweeping the laser beam 3 (moving the sapphire plate 1).

When the controller 105 detects that a signal obtained from a temperature sensor or the like exceeds a preset threshold value (temperature) while the irradiation of the laser beam 3 is being swept as described above, the controller 105 adjusts the temperature. For example, the sapphire plate 1 is cooled by controlling the portion 102 to appropriately adjust the state of the heat-temperature gradient generated inside the sapphire plate 1 so that cracks 21 are generated only in the portions to be cleaved. In other words, it prevents the crack 21 from extending to areas other than the part to be cut and the occurrence of unexpected cracks.
Further, when the irradiation of the laser beam 3 is being swept as described above, the laser output adjustment unit 103 controlled by the control unit 105 causes the crack 21 to grow (the irradiation of the laser beam 3 to the sapphire plate 1 so that the crack 21 does not abruptly stop), for example, according to a control pattern set in advance in the control unit 105, or the output signal of the above-mentioned temperature sensor or the like Corresponding to the temperature of the sapphire plate 1 shown, the laser beam 3 emitted from the laser light source 103 is adjusted to an appropriate laser output.
The coordinated operation of the sweep mechanism unit 104, the temperature control unit 102, and the laser output control unit 103a is an example. In addition, the sweep mechanism section 104, the temperature adjustment section 102, and the laser output adjustment section 103a may be operated.

The laser cleaving apparatus described here holds the sapphire plate 1 having the initial grooves 2 in advance, and is configured to irradiate the laser beam 3 for propagating the cracks 21. However, the laser cleaving method of the present invention Furthermore, a laser cutting device equipped with a second laser light source (laser processing device or the like) that oscillates a second laser beam for forming the initial grooves 2 may be used.
The laser cutting device equipped with the second laser light source irradiates the position where the initial groove 2 is to be formed with the second laser beam (first process), and the initial groove formed by the irradiation of the second laser beam. A laser beam 3 is applied to the groove 2 (third process). In other words, this laser cutting apparatus irradiates the laser beam 3 so as to follow the second laser beam, and sweeps these laser beams so that the laser beam 3 follows the second laser beam. .

For the second laser beam, for example, a wavelength of 355 [nm] to 1064 [nm], which is transmitted through the sapphire plate 1, is applied. have. Thereby, it is possible to form the initial grooves 2 having an appropriate depth in the sapphire plate 1 .
When the laser cleaving apparatus is configured with the second laser light source as described above, the sapphire plate 1 having no initial grooves 2 (microdefects) is installed and fixed in the laser cleaving apparatus, and the sapphire plate 1 can be cut.

REFERENCE SIGNS LIST 1 sapphire plate 2 initial groove 3 laser beam 3a beam spot 4 arrow 10 compressive stress field 11 tensile stress field 11a tensile stress 12 arrows 20, 21 crack 30 _CO2 laser beam 101 holding mechanism section 102 temperature control section 103 laser light source 103a laser output Adjustment unit 104 Sweep mechanism unit 105 Control unit 106 Laser optical system

Claims (4)

a first step of forming a ground portion having a plurality of grinding scratches on the surface of sapphire using a grinding device and holding the sapphire in a holding mechanism;
a second step of oscillating CO laser light with a wavelength of 5.5 [μm] ;
a third step of irradiating the sapphire with the CO laser beam having a circular beam cross section ;
a fourth step of generating thermal stress from the surface of the sapphire to the inside of the thickness of the sapphire by the CO laser beam that is transmitted through the sapphire, thereby propagating a crack in the sapphire and breaking the sapphire;
has
The third step is
irradiating the ground portion of the edge portion of the sapphire with the CO laser beam having a laser output of 60 [W] or more so that the distribution of the thermal stress on the surface of the sapphire becomes the circular shape ;
The fourth step is
The distribution of the thermal stress generated by the irradiation of the CO laser light is applied to the ground portion of the sapphire by using the sweeping mechanism section for moving the holding mechanism section. on the surface of the sapphire, sweeping at a speed at which the irradiation time to the same portion of the sapphire is suppressed so as to move while maintaining the circular shape;
Starting from the ground portion of the edge of the sapphire, the crack is propagated along the sweep direction of the sweep mechanism,
A laser cutting method characterized by: The fourth step is
When the crack is propagated, the temperature of the sapphire held in the holding mechanism is adjusted by using the temperature adjustment part provided in the holding mechanism so that the crack propagates in the part to be cleaved. do,
The laser cutting method according to claim 1, characterized in that: The fourth step is
When the sweeping mechanism section is used to sweep the CO laser beam to propagate the crack, a temperature adjusting section provided in the holding mechanism section and a laser output adjusting section for adjusting the laser output of the CO laser light are provided. A fifth step of adjusting the temperature of the sapphire held by the holding mechanism and adjusting the output of the CO laser beam so that the crack develops in the portion where the cleaving is performed ,
The fifth step is
The control unit controls the sweep mechanism unit, the temperature adjustment unit, and the laser output adjustment unit so as to perform a preset coordinated operation or as independent operations.
The laser cutting method according to claim 1, characterized in that: The third step is
irradiating the CO laser light in a parallel beam;
The laser cutting method according to any one of claims 1 to 3, characterized in that:

Images