Patent Publication Number: US-2023150061-A1

Title: Laser processing apparatus

Description:
TECHNICAL FIELD 
     The present disclosure relates to a laser processing apparatus. 
     BACKGROUND ART 
     In the related art, an electro-optical element such as a KTN crystal, in which an upper and lower surfaces are sandwiched and held by two metal blocks via a graphite sheet, is known. Since the deflection characteristics of this electro-optical element strongly depend on the temperature, a Peltier device is disposed inside two metal blocks in order to prevent the temperature rise when a voltage is applied, and the temperature of the electro-optical element is controlled to be constant with high precision. 
     Citation List 
     Patent Literature 
     [PTL 1] Japanese Unexamined Patent Application Publication No. 2017-203847. 
     SUMMARY OF INVENTION 
     Technical Problem 
     Incidentally, in a laser processing apparatus that performs processing using laser, the optical deflector of Patent Document 1 may be used to deflect the laser. In this case, a graphite sheet is irradiated with some of the laser (the beam profile bottom) applied to the electro-optical element of the optical deflector, and the graphite sheet is melted, so that a part of the graphite sheet may adhere to the electro-optical element. When the graphite sheet adheres to the electro-optical element, the laser is absorbed by the graphite sheet adhering to the surface of the electro-optical element, which may cause the temperature of the electro-optical element to rise. Further, when the metal electrodes on the upper and lower parts of the electro-optical element are irradiated with the laser, the temperature rise of the irradiated portion causes the temperature rise of the KTN crystal. The change in the temperature of the electro-optical element changes the characteristics of light deflection and reduces the accuracy of the laser irradiation position on the point to be processed. 
      Therefore, an object of the present disclosure is to provide a laser processing apparatus capable of preventing a temperature rise of an electro-optical element, stabilizing the temperature of the electro-optical element, and controlling laser deflection with high accuracy. 
     Solution to Problem 
     A laser processing apparatus of the present disclosure includes: an electro-optical element; a laser irradiation unit that irradiates the electro-optical element with laser; a pair of electrodes provided on both sides of the electro-optical element so as to sandwich the electro-optical element therebetween; a cushioning material having conductivity provided between the pair of electrodes and the electro-optical element; and a shield material that is provided on an incident side of the electro-optical element, in an irradiation direction of the laser, intersecting a direction in which an electric field applied by the pair of electrodes is applied, and prevents incidence of the laser onto the cushioning material. 
     Another laser processing apparatus of the present disclosure includes: an electro-optical element; a laser irradiation unit that irradiates the electro-optical element with laser; a pair of electrodes provided on both sides of the electro-optical element so as to sandwich the electro-optical element therebetween; a cushioning material having conductivity provided between the pair of electrodes and the electro-optical element; and a window material that is provided on an incident side of the electro-optical element, in an irradiation direction of the laser, intersecting a direction in which an electric field applied by the pair of electrodes is applied, and covers the electro-optical element. 
     Advantageous Effects of Invention 
     According to the present disclosure, it is possible to prevent the temperature rise of the electro-optical element, stabilize the temperature of the electro-optical element, and control the laser irradiation position with high accuracy. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG.  1    is a diagram schematically showing a laser processing apparatus according to Embodiment 1. 
         FIG.  2    is a two-sided view schematically showing an optical deflector. 
         FIG.  3    is an explanatory diagram relating to the dimensions of an optical deflector. 
         FIG.  4    is a diagram schematically showing an optical deflector of a laser processing apparatus according to Embodiment 2. 
         FIG.  5    is a two-sided view schematically showing an optical deflector of a laser processing apparatus according to Embodiment 3. 
         FIG.  6    is a diagram schematically showing an optical deflector of a laser processing apparatus according to Embodiment 4. 
         FIG.  7    is a two-sided view schematically showing an optical deflector of a laser processing apparatus according to Embodiment 5. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     Hereinafter, embodiments according to the present disclosure will be described in detail with reference to the drawings. In addition, the present invention is not limited to these embodiments. In addition, the components in the following embodiments include those that can be easily replaced by those skilled in the art, or those that are substantially the same. Further, the components described below can be appropriately combined, and when there are a plurality of embodiments, each embodiment can be combined. 
     Embodiment 1 
       FIG.  1    is a diagram schematically showing a laser processing apparatus according to Embodiment 1.  FIG.  2    is a two-sided view schematically showing a KTN crystal and the circumference thereof.  FIG.  3    is an explanatory diagram relating to the dimensions of the KTN crystal and the circumference thereof. As shown in  FIG.  1   , the laser processing apparatus  10  according to Embodiment 1 is an apparatus capable of irradiating a work piece  5  with the laser L to process the work piece  5 . 
     As shown in  FIG.  1   , the laser processing apparatus  10  includes a laser irradiation device  11 , a scanning optical system  12 , a focus optical system  13 , and a support table  6 . 
     The laser irradiation device  11  is a device that outputs laser L. The laser irradiation device  11  may use a pulse wave or a continuous wave, as the laser L to be output. Further, the laser irradiation device  11  may emit the laser L in a single mode or a multi-mode. Since the KTN crystal contains a plurality of elements (Ka, Ta, Nb) and it is difficult to increase the size, the laser irradiation device  11  includes a reduction optical system that reduces the beam diameter and converts the beam into parallel light such that the KTN crystal can be irradiated with laser light. 
     The laser L emitted from the laser irradiation device  11  is a processing laser, and is a high-power laser having an output of 1 W or more. Specifically, the frequency of the laser L is about 1 kHz to 1000 kHz, and the output of the laser L is about 10 W to 10 kW. The wavelength of the laser L is not particularly limited, but may be a wavelength band suitable for the KTN crystal that is the electro-optical element  21  provided in the scanning optical system  12  described later. 
     The scanning optical system  12  is an optical system that scans the laser L emitted from the laser irradiation device  11  on the work piece  5 . The scanning optical system  12  includes a scanner  20  capable of operating laser within the surface of the work piece  5 . The scanner  20  is an optical deflector using the electro-optical element  21 . 
     The focus optical system  13  is an optical system that condenses the laser L emitted from the scanning optical system  12  at a focal point and applies the condensed laser L on the work piece  5 . The focus optical system  13  includes an optical member such as a condensing lens. 
     The support table  6  supports the work piece  5  at a predetermined position. The support table  6  may be a moving stage for moving the work piece  5  in the horizontal plane. The laser L emitted from the laser irradiation device  11  irradiates the surface of the work piece  5  disposed on the support table  6 . 
     The laser processing apparatus  10  configured as described above emits the laser L from the laser irradiation device  11 , and guides the emitted laser L to the scanning optical system  12 . The laser processing apparatus  10  scans the scanning optical system  12  with the incident laser L to change the irradiation position of the laser L on the surface of the work piece  5 . The laser processing apparatus  10  inputs the laser L emitted from the scanning optical system  12  to the focus optical system  13 , and applies the condensed laser L on the work piece  5 . 
     Next, the scanner  20  will be described with reference to  FIGS.  2  and  3   . As shown in  FIGS.  2  and  3   , the scanner  20  includes an electro-optical element  21 , a pair of electrodes  22 , a cushioning material  23 , an insulation material (insulating portion)  24 , and a shield material  25 . Inside the electrode  22 , a temperature control element such as a Peltier device is included in order to control the temperature with high accuracy. The scanner  20  controls the electron density in the electro-optical element  21  by applying a voltage to the electro-optical element  21  by the pair of electrodes  22  in the direction facing each other, thereby changing the refractive index and deflecting the laser L in the application direction of the voltage. The laser L incident on the scanner  20  is broad laser emitted from a laser oscillator, or collimated laser whose beam diameter is controlled by a reduction optical system required to enter collimated light into an electro-optical element. 
     A KTN crystal is used for the electro-optical element  21 , and the electro-optical element  21  is provided on the optical path of the laser L. The size of the KTN crystal is small, for example, the plate thickness of the irradiation surface on which the laser is incident is about 1 to 2 mm. The electro-optical element  21  is irradiated with the laser L. 
     For example, a copper electrode is applied to the pair of electrodes  22 . The pair of electrodes  22  are provided on both sides of the electro-optical element  21  so as to sandwich the electro-optical element therebetween. A voltage is applied to the pair of electrodes  22  in the directions facing each other. The irradiation direction of the laser and the application direction of the voltage are orthogonal to each other. 
     The cushioning materials  23  are provided between the electro-optical element  21  and the pair of electrodes  22 , respectively. The cushioning material  23  has conductivity. The cushioning material  23  is, for example, a carbon film. 
     The insulation material  24  is provided on the incident side of the electro-optical element  21  in the irradiation direction of the laser L. Further, the insulation material  24  is provided between the shield material  25  and the electrode  22 , which will be described later, and insulates the shield material  25  and the electrode  22 . The insulation material  24  also functions as a support member for supporting the shield material  25 . 
     The shield material  25  is provided on the incident side of the insulation material  24  in the irradiation direction of the laser L. Further, the shield material  25  shields the laser L from entering the cushioning material  23 . The shield material  25  is formed in a plate shape and has an opening  30  through which the laser L passes. The opening  30  is formed in the central portion of the shield material  25  and is a rectangular opening. Therefore, the shield material  25  is formed in a four-sided frame shape. The shield material  25  is made of metal, and the shield material  25  is not particularly limited to metal, and ceramic may be applied, for example. Further, the shield material  25  prevents the incidence of the laser L onto at least the cushioning material  23 , and specifically, covers a part of the electrodes  22  and the cushioning material  23  so as to prevent incidence of the laser L thereto. 
     Next, the dimensions of the shield material  25  will be described with reference to  FIG.  3   . In the orthogonal plane orthogonal to the irradiation direction of the laser L, the direction in which the pair of electrodes  22  face each other is the height direction, and the direction orthogonal to the height direction is the width direction. Here, the length of the shield material  25  in the width direction is A, the length of the opening  30  of the shield material  25  in the width direction is B, and the length of the electro-optical element  21  in the width direction is C. Further, the length of the shield material  25  in the height direction is a, the length of the opening  30  of the shield material  25  in the height direction is b, and the length of the electro-optical element  21  in the height direction is c. Further, the thickness of the cushioning material  23  in the height direction is d. Further, the beam diameter φ of the laser L is 2R. 
     In the width direction, the length A of the shield material  25  is equal to or greater than the length C of the electro-optical element  21 . The length B of the opening  30  of the shield material  25  is larger than the beam diameter φ2R of the laser L, and is equal to or less than the length C of the electro-optical element  21 . 
     In the height direction, the length a of the shield material  25  is equal to or greater than the total length (c + 2d) of the electro-optical element  21  and the cushioning materials  23  on both sides. Further, the length a of the shield material  25  is preferably twice or more the beam diameter φ2R of the laser L. The length b of the opening  30  of the shield material  25  is larger than the beam diameter φ2R of the laser L and is smaller than the length c of the electro-optical element  21 . In the shield material  25 , the length ((c - b)/2) between the opening  30  of the shield material  25  and the cushioning material  23  is 0.1 mm or more or 10% or more of the beam diameter φ2R, whichever is smaller. 
      When the laser L is incident on the scanner  20  as described above, the laser L is incident on the electro-optical element  21  through the opening  30  of the shield material  25 . At this time, the laser L is prevented from being incident on the cushioning material  23  by the shield material  25 . 
     In Embodiment 1, the shield material  25  has an opening  30  formed therein, but the configuration is not particularly limited as long as the cushioning material  23  can be covered. For example, the shield material  25  has a divided structure, and may be configured to cover the cushioning materials  23  on both sides of the electro-optical element  21 , respectively. 
     Further, in Embodiment 1, the insulation material  24  is provided between the shield material  25  and the electrode  22 , but the configuration is not particularly limited. Since the insulating state between the shield material  25  and the electrode  22  needs to be maintained, air may be applied as an insulating portion between the shield material  25  and the electrode  22 . 
     Embodiment 2 
     Next, the laser processing apparatus  10  according to Embodiment 2 will be described with reference to  FIG.  4   . In addition, in Embodiment 2, in order to avoid duplicate description, the parts different from Embodiment 1 will be described, and the parts having the same configuration as Embodiment 1 will be described with the same reference numerals.  FIG.  4    is a diagram schematically showing an optical deflector of the laser processing apparatus according to Embodiment 2. 
     In the laser processing apparatus  10  of Embodiment 2, the shape of the opening  30  of the shield material  25  of the scanner  20  is circular instead of rectangular. Even when the opening  30  has a circular shape, the dimensions of the opening  30  shown in Embodiment 1 are satisfied. In the laser processing apparatus  10  of Embodiment 2, by making the opening  30  circular, it is possible to apply the laser L aiming at the center of the opening  30 . 
     Embodiment 3 
     Next, the laser processing apparatus  10  according to Embodiment 3 will be described with reference to  FIG.  5   . In addition, even in Embodiment 3, in order to avoid duplicate description, the parts different from Embodiments 1 and 2 will be described, and the parts having the same configuration as those of Embodiments 1 and 2 will be described with the same reference numerals.  FIG.  5    is a two-sided view schematically showing the optical deflector of the laser processing apparatus according to Embodiment 3. 
     The laser processing apparatus  10  of Embodiment 3 further includes a cooling unit  31  in addition to the scanner  20  of Embodiment 2. The cooling unit  31  cools the shield material  25  and also cools the electro-optical element  21  via the shield material  25 . The cooling unit  31  includes a cooling block  33  and a pipe  34  connected to the cooling block  33 . The cooling block  33  is provided at a portion located on one electrode  22  side of the shield material  25 , and is provided so as to extend in the width direction. The cooling block  33  is formed of metal, and a flow path  35  through which cooling water flows is formed inside the cooling block  33 . The pipe  34  is connected to the flow path  35  of the cooling block  33  to circulate the cooling water. Therefore, the cooling unit  31  cools the shield material  25  by circulating cooling water through the pipe  34  to the cooling block  33 , and also cools the electro-optical element  21  via the shield material  25 . 
      In Embodiment 3, the cooling unit  31  is provided on the shield material  25 , but the cooling unit  31  and the shield material  25  may be integrated. That is, the cooling water flow path through which the cooling water flows may be formed in the shield material  25 , and the cooling water may flow through the cooling water flow path. Further, in Embodiment 3, the cooling unit  31  has a water-cooled structure using cooling water, but may have an air-cooled structure. For example, the cooling unit  31  includes fins provided on the shield material  25  and an air cooling fan that sends cooling air toward the fins. The cooling unit  31  cools the shield material  25  by sending cooling air toward the fins by an air cooling fan. 
     Embodiment 4 
     Next, the laser processing apparatus  10  according to Embodiment 4 will be described with reference to  FIG.  6   . In addition, even in Embodiment 4, in order to avoid duplicate description, the parts different from Embodiments 1 to 3 will be described, and the parts having the same configuration as those of Embodiments 1 to 3 will be described with the same reference numerals.  FIG.  6    is a diagram schematically showing an optical deflector of the laser processing apparatus according to Embodiment 4. 
      The laser processing apparatus  10  of Embodiment 4 further includes a window material  41  in addition to the scanner  20  of Embodiments 1 and 2. The window material  41  of Embodiment 4 may be applied to Embodiment 3. 
     The window material  41  is provided on the incident side of the electro-optical element  21  in the irradiation direction of the laser L, and covers the electro-optical element  21 . Further, the window material  41  is provided between the electro-optical element  21  and the shield material  25 . The window material  41  is glass such as quartz. The window material  41  is formed in a plate shape and also functions as an insulation material. The window material  41  prevents the adhesion of dust to the electro-optical element  21 . 
     Embodiment 5 
     Next, a laser processing apparatus  10  according to Embodiment 5 will be described with reference to  FIG.  7   . In addition, even in Embodiment 5, in order to avoid duplicate description, the parts different from Embodiments 1 to 4 will be described, and the parts having the same configuration as those of Embodiments 1 to 4 will be described with the same reference numerals.  FIG.  7    is a two-sided view schematically showing the optical deflector of the laser processing apparatus according to Embodiment 5. 
     The laser processing apparatus  10  of Embodiment 5 is obtained by omitting the shield material  25  and the insulation material  24  from the scanner  20  of Embodiment 4. That is, the scanner  20  of Embodiment 5 includes an electro-optical element  21 , a pair of electrodes  22 , a cushioning material  23 , and a window material  41 . The window material  41  is provided on the incident side of the electro-optical element  21  in the irradiation direction of the laser L, and covers the electro-optical element  21 . The window material  41  prevents the adhesion of dust to the electro-optical element  21 . 
     As described above, the laser processing apparatus  10  described in the present embodiment is understood as follows, for example. 
     The laser processing apparatus  10  according to the first aspect includes an electro-optical element  21 , a laser irradiation unit (laser irradiation device  11 ) that irradiates the electro-optical element  21  with laser L, a pair of electrodes  22  provided on both sides of the electro-optical element  21  so as to sandwich the electro-optical element  21  therebetween, a cushioning material  23  having conductivity provided between the pair of electrodes  22  and the electro-optical element  21 , and a shield material  25  that is provided on an incident side of the electro-optical element  21 , in an irradiation direction of the laser L, intersecting a direction in which a voltage applied by the pair of electrodes  22  is applied, and prevents incidence of the laser L onto the cushioning material  23 . 
     According to this configuration, the shield material  25  can prevent the laser L from being incident on the cushioning material  23 . Therefore, it is possible to prevent the cushioning material  23  from being irradiated with a part of the laser L, which prevents the cushioning material  23  from being melted and evaporated by the irradiation of a part of the laser L and adhering to the electro-optical element  21 , so that the temperature rise caused by the cushioning material  23  adhering to the electro-optical element  21  absorbing the laser light can be prevented, the temperature of the electro-optical element  21  can be stabilized, and the irradiation position of the laser can be controlled with high accuracy. 
     In a second aspect, the electro-optical element  21  is a KTN crystal. 
     According to this configuration, it is possible to stabilize the temperature of the KTN crystal whose light deflection characteristics are likely to change depending on the temperature. 
     In a third aspect, the shield material  25  is formed in a plate shape and has an opening  30  through which the laser L passes. 
     According to this configuration, by forming the opening  30 , it is possible to handle the shield material  25  as a unit, while allowing the laser L to enter the electro-optical element  21 . 
     In a fourth aspect, in an orthogonal plane orthogonal to the irradiation direction of the laser, a direction in which the pair of electrodes  22  face each other is a height direction, and a direction orthogonal to the height direction is a width direction, and in the shield material  25 , the length of the opening  30  in the height direction is larger than the beam diameter φ of the laser L, and smaller than the length of the electro-optical element  21  in the height direction, and a length between the opening  30  and the cushioning material  23  is 0.1 mm or more or 10% or more of the beam diameter, whichever is smaller. 
     According to this configuration, the laser L can be appropriately incident on the electro-optical element  21  while appropriately covering the cushioning material  23 . 
     In a fifth aspect, a length of the opening  30  in the width direction is larger than the beam diameter φ of the laser L and is equal to or less than a length of the electro-optical element  21  in the width direction. 
     According to this configuration, the laser L can be appropriately incident on the electro-optical element  21  without leaking the laser L from the electro-optical element  21 . 
     In a sixth aspect, the shield material is made of metal, and further includes an insulating portion provided between the shield material and the electrode. 
     According to this configuration, the electrical connection between the shield material  25  and the electrode  22  can be prevented. 
      In a seventh aspect, the laser L incident on the electro-optical element  21  is collimated laser. 
     According to this configuration, since the collimated laser L can be incident on the electro-optical element  21 , the laser L can be suitably deflected by the electro-optical element  21 . 
     In an eighth aspect, a cooling unit  31  that cools the shield material  25  is further provided. 
     According to this configuration, the shield material  25  can be cooled by the cooling unit  31 , and the electro-optical element  21  can be cooled via the shield material  25 . 
     In a ninth aspect, a window material  41  that is provided on the incident side of the electro-optical element  21  in the irradiation direction of the laser L and covers the electro-optical element  21  is further provided. 
     According to this configuration, the window material  41  can prevent the adhesion of dust to the electro-optical element  21 . Therefore, it is possible to prevent the temperature rise of the electro-optical element  21  due to the irradiation of the dust with the laser L. 
     In a tenth aspect, the window material  41  is provided between the electro-optical element  21  and the shield material  25 . 
     According to this configuration, since the window material  41  can be disposed closer to the electro-optical element  21  than the shield material  25 , it is possible to suitably prevent dust from adhering to the electro-optical element  21 . 
     In an eleventh aspect, the shield material  25  is made of metal, and the window material  41  functions as an insulation material  24  provided between the shield material  25  and the electrode  22 . 
     According to this configuration, the window material  41  can also function as the insulation material  24  that insulates the conductivity between the electrode  22  and the shield material  25 , so that it is not necessary to provide the window material  41  and the insulation material  24 , respectively, and the configuration can be simplified. 
     The laser processing apparatus  10  according to the twelfth aspect includes an electro-optical element  21 , a laser irradiation unit (laser irradiation device  11 ) that irradiates the electro-optical element  21  with laser L, a pair of electrodes  22  provided on both sides of the electro-optical element  21  so as to sandwich the electro-optical element  21  therebetween, a cushioning material  23  having conductivity provided between the pair of electrodes  22  and the electro-optical element  21 , and a window material  41  that is provided on an incident side of the electro-optical element  21 , in an irradiation direction of the laser L, intersecting a direction in which a voltage applied by the pair of electrodes  22  is applied, and covers the electro-optical element  21 . 
     According to this configuration, the window material  41  can prevent the adhesion of dust to the electro-optical element  21 . Therefore, it is possible to prevent the temperature rise of the electro-optical element  21  due to the irradiation of the dust with the laser L, and to stabilize the temperature of the electro-optical element  21 . 
     Reference Signs List 
     
         
           5  Work piece 
           6  Suport table 
           10  Laser processing apparatus 
           11  Laser irradiation device 
           12  Scanning optical system 
           13  Focus optical system 
           20  Scanner 
           21  Electro-optical element 
           22  Electrode 
           23  Cushioning material 
           24  Insulation material 
           25  Shield material 
           30  Opening 
           31  Cooling unit 
           33  Cooling block 
           34  Pipe 
           35  Flow path 
           41  Window material 
         L Laser