JP2018138310A - Laser processing apparatus for hole and laser processing method - Google Patents

Abstract

An object of the present invention is to provide a laser processing apparatus for a hole that can perform deep hole processing on an opaque material and a transparent material. A piping for introducing an atmospheric fluid 15 into a processing sample storage container, a pressure control unit 30 inside the processing sample storage container, and a temperature control unit 4 inside the processing sample storage container are provided. A laser optical system for introducing the laser beam 34 from the outside to the inside, and the temperature and pressure of the atmosphere fluid inside the processing sample storage container so that the dimensionless temperature t1 obtained by the following equation is 300 or more. Is controlled to generate convection of the atmospheric fluid inside the hole formed in the processing sample, thereby forming a hole in the processing sample. (Where α is the volume expansion coefficient of the atmosphere fluid, g is the gravitational acceleration, ν is the kinematic viscosity of the atmosphere fluid, κ is the temperature diffusivity of the atmosphere fluid, T0 is the temperature of the atmosphere fluid outside the hole, T1 is the temperature of the hole fluid. The temperature of the inner wall, a is the radius of the hole, and l is the depth of the hole.)

Description

  The present invention relates to a laser processing apparatus and a laser processing method for holes, and more particularly to a laser processing apparatus and a laser processing method for deep holes having a high aspect ratio that is a hole diameter with respect to the hole depth.

  Processing with a laser beam is often used for low-depth processing such as surface layer processing such as marking and surface treatment, and cutting processing of a relatively thin plate material. On the other hand, in the processing of a closed space with a high depth represented by deep hole processing, firstly, the laser beam is reflected and scattered on the wall surface and does not reach the bottom of the hole. It is said that deep hole machining with a laser beam is difficult because there is no means for discharging the scraps outside the hole. For this reason, there is substantially no laser processing technology for deep holes having an aspect ratio, which is the ratio of the hole depth and the hole diameter, exceeding 100.

  In the case of a transparent material, laser light can be collected from the back side opposite to the front side where holes are formed (see, for example, Non-Patent Document 1). For this reason, it is not necessary to allow the laser beam to pass through the hole to be formed, and the first problem can be avoided. Even in this case, it is not easy to exceed the aspect ratio of 100. For example, it has been attempted to realize deeper hole processing by using etching processing with a corrosive solution (see, for example, Non-Patent Document 2). However, even in this case, the hole depth only extends several times. This is due to the fact that the problem of discharging the second processing waste is not completely eliminated, but in addition, problems such as excessive expansion of the hole diameter due to etching and non-uniformity of the hole diameter. This is also because it newly occurs.

  In recent years, an optical processing method called the LIBWE method has also been proposed (see, for example, Non-Patent Document 3). In this method, the pigment dissolved in the atmospheric fluid is ablated and explosive processing is performed by the pressure. Therefore, it can be said to be a kind of machining, and it is characterized by machining with a smooth surface. This method is also claimed to be capable of high-aspect deep hole machining, but in terms of work discharge, there is no significant advantage in principle compared to conventional laser machining, and in fact innovative machining results Considering that it does not appear, it is considered that the deep hole processing performance itself in the above method is not so high.

Thermal physical processing in general fluids such as air and water (D. J. Hwang et al., Appl. Phys. A 79, 605-612 (2004)) Etching-assisted processing in water (Y. Kondo, Jpn. J. Appl. Phys. 38, 1146-1148 (1999)) Laser-induced backside wet etching (LIBWE) (X. Ding et al., J Photochem Photobiol A Chem., 166, 129, (2004))

  As described above, a deep hole laser processing apparatus and laser processing method having a high aspect ratio, which is a hole diameter with respect to the hole depth, have not been substantially obtained.

  Then, this invention is providing the laser processing apparatus for holes which can process the deep hole to an opaque material and a transparent material.

（ここで、αは前記雰囲気流体の体積膨張率、ｇは重力加速度、νは前記雰囲気流体の動粘度、κは前記雰囲気流体の温度拡散率、Ｔ_０は前記穴の外側の前記雰囲気流体の温度、Ｔ_１は前記穴の内壁の温度、ａは前記穴の半径、ｌは前記穴の深さである。） The hole laser processing apparatus according to the present invention has a wall that partitions the outside and the inside, a window through which the laser beam can be transmitted for storing the processing sample inside and guiding the laser light from the outside to the inside A processing sample storage container having a portion on the wall;
An atmospheric fluid pipe for introducing an atmospheric fluid into the processing sample storage container;
A pressure control unit for controlling the pressure inside the processing sample storage container;
A temperature control unit for controlling the temperature inside the processing sample storage container;
A laser optical system for introducing laser light from the outside into the inside through the window;
And the temperature of the ambient fluid inside the processing sample storage container by the pressure control unit and the temperature control unit so that the dimensionless temperature t ₁ obtained by the following formula is 300 or more. And the pressure is controllable, and convection of the atmospheric fluid is generated inside the hole formed in the processing sample to form a hole in the processing sample.

(Where α is the volume expansion coefficient of the ambient fluid, g is the acceleration of gravity, ν is the kinematic viscosity of the ambient fluid, κ is the temperature diffusivity of the ambient fluid, and T ₀ is the ambient fluid outside the hole. Temperature, T ₁ is the temperature of the inner wall of the hole, a is the radius of the hole, and l is the depth of the hole.)

（ここで、αは前記雰囲気流体の体積膨張率、ｇは重力加速度、νは前記雰囲気流体の動粘度、κは前記雰囲気流体の温度拡散率、Ｔ_０は前記穴の外側の前記雰囲気流体の温度、Ｔ_１は前記穴の内壁の温度、ａは前記穴の半径、ｌは前記穴の深さである。）
前記加工用試料にレーザ光を照射して、前記加工用試料に形成する前記穴の内部に前記雰囲気流体の対流を生じさせて、前記加工用試料に穴を形成するステップと、
を含む。 The hole laser processing method according to the present invention includes a step of arranging a processing sample in a partitioned region and introducing an ambient fluid around the processing sample;
Controlling the temperature and pressure of the ambient fluid around the processing sample so that the dimensionless temperature t ₁ obtained by the following formula is 300 or more;

(Where α is the volume expansion coefficient of the ambient fluid, g is the acceleration of gravity, ν is the kinematic viscosity of the ambient fluid, κ is the temperature diffusivity of the ambient fluid, and T ₀ is the ambient fluid outside the hole. Temperature, T ₁ is the temperature of the inner wall of the hole, a is the radius of the hole, and l is the depth of the hole.)
Irradiating the processing sample with laser light to cause convection of the atmospheric fluid inside the hole formed in the processing sample, and forming a hole in the processing sample;
including.

  According to the laser processing apparatus and the laser processing method for holes according to the present invention, deep holes having a high aspect ratio that is a hole diameter with respect to the hole depth can be formed for both the transparent material and the opaque material.

It is the schematic which shows the structure of the laser processing apparatus for holes which concerns on Embodiment 1. FIG. FIG. 2 is an enlarged view of the inside of the processing sample storage container of FIG. 1. It is a schematic diagram which shows the state in which the streamline has reached the hole bottom and convection has arisen. It is a mimetic diagram showing the state where the streamline does not reach the hole bottom, is accompanied by a staying part, and sufficient convection is not obtained as a whole. It is the schematic which shows the temperature-pressure dependence of the coefficient part ((alpha) g / (nu) kappa) of a light hill formula. (A) is the schematic which shows the mode of the laser beam which injects into a hole, (b) is the schematic which shows the refraction | bending of the laser beam which arises in the boundary layer of the cold part of the atmosphere around a hole, and a warm part. (C) is a schematic diagram showing total reflection of laser light generated in the boundary layer between the cold part and the warm part inside the hole. It is a graph which shows an example of the relationship of the reflectance with respect to the incident angle of p polarized light (radial polarized light) and s polarized light (azimuth polarized light). FIG. 10 is a schematic diagram showing the incidence and emission of laser light on a processing sample that is an opaque material and a transparent material in the hole laser processing apparatus according to the fifth embodiment. It is the schematic which shows an example of the output by the coupling monitor of FIG. It is the schematic which shows an example of the output by the processing hole observation camera of FIG.

(Background to the present invention)
The present inventor has studied the following problems in deep hole processing of opaque materials and transparent materials.

1. In the case of opaque material processing (metal etc.) (Problem 1-1) Deep hole processing to an opaque material is very difficult. The reason is that the inventor
(1) The laser beam is absorbed and scattered by the wall surface of the hole and attenuated.
(2) Residual processing waste in the hole, absorption and scattering due to residual bubbles in the atmospheric fluid occur,
(3) Refraction scattering of the processing laser beam due to the jet generated in the hole opening occurs.
I found that there are problems. Because of these problems, the depth of drilling a metal with a laser beam is only about several millimeters when the hole diameter is 100 μm.
(Problem 1-2) Special polarized light is effective for high-efficiency drilling, but difficult to apply to deep-hole drilling. High-efficiency drilling using special polarized light such as radial polarized light and azimuth polarized light whose polarization directions are axially symmetric has been proposed. Radial polarized light is advantageous when the hole is shallow, and azimuth polarized light is advantageous as it becomes deeper. As shown in FIG. 6, radial polarized light (p-polarized light) has a large absorption with respect to a plane perpendicular to the beam and is efficiently converted into heat, and azimuth polarized light (s-polarized light) is horizontal to the beam. This is because the reflectivity is high with respect to a smooth surface, and the light is efficiently reflected and propagated in the hole to reach the bottom of the hole. However, the effect is up to a depth of several millimeters (M. Meier et al., Proc. Of SPIE 6053 605312, (2006)). Lose.

2. In the case of transparent material processing (glass etc.) (Problem 2) With transparent materials, deep hole processing is still very difficult, although not as opaque materials. The transparent material can be irradiated with laser light from the back surface opposite to the surface on which the hole of the material is provided. For this reason, it is not necessary to consider the problems (1) and (3) of (Problem 1-1). However, the above problem (2) still remains, and in addition to this, transparent materials are often brittle materials, so the thermal effects such as thermal shock are more important than the opaque materials in which metal is the main work piece. Must be used. In order to avoid such a restriction, the processing waste is removed with an ablation pressure as high as possible while working with ultrashort pulse laser light or ultraviolet light as much as possible to clear the problem of (2) above. The conflicting requirements must be met, which is actually difficult. As a result, the hole depth of 1 mm is the limit when removing directly. However, since it can be altered even with a beam power below the removal processing threshold, a method of machining a deep hole of several mm by corroding and removing with an etching solution after the alteration has been developed. However, if this method is used, the hole diameter may change depending on the depth, the residue of the corrosive liquid residue in the hole, and the dissolved base material must be discharged outside the hole. However, this is not a technique that enables deep hole machining. The LIBWE method is also expected to have a limit on the hole depth for the same reason.

(About the present invention that has been made through the discovery of the underlying invention and further examination)
The present inventor has made various studies and found that deep hole processing can be performed by laser processing using a supercritical fluid as an atmospheric fluid, and has led to a basic invention. In other words, it was confirmed that deep hole machining 10 times or more that of the prior art can be performed in a transparent material by laser machining in an atmosphere of supercritical carbon dioxide. Supercritical carbon dioxide is carbon dioxide pressurized and / or heated to a critical point of 7.4 MPa and 31 ° C. or higher. By drilling deep holes in the supercritical carbon dioxide as the atmospheric fluid by back irradiation of the laser beam to the opposite side of the hole opening, drilling can be performed at least 10 times deeper than in water and air. Thus, it was confirmed that the hole diameter was stable. With respect to this processing mechanism, the present inventor believes that there is a possibility that heat and processing waste removal due to convection of the supercritical fluid shown in FIG.

  Furthermore, in the metal processing which is an opaque material, it is necessary to make a laser beam enter from the opening part side of a hole unlike back surface irradiation like glass processing. For this reason, the present inventor has further found that since the jet or convection due to machining interferes with the laser beam, the efficiency of introducing the laser beam into the machining hole, that is, decoupling becomes a problem. That is, the incident beam may be reflected and refracted by the convection temperature boundary surface, and may not reach the hole. In this regard, the present inventor suggests that the same refractive index distribution as that of the optical fiber appears in the hole due to convection, and that the light reaches the hole bottom without attenuation and can perform deep hole processing. I found it. Furthermore, as will be described later, the present inventor applied the Light Hill equation to the convection in the hole and controlled the temperature and pressure conditions of the atmospheric fluid, not limited to the supercritical fluid, to control the convection in the hole. In particular, the inventors have found that the above problem (2) can be solved, and have reached the present invention. Therefore, the shape of the temperature boundary surface is made a convergence type as shown in FIG. 5 by the convection control by the temperature control in the vicinity of the machining hole depending on the beam incident condition, and the loss due to the decoupling can be prevented.

（ここで、αは前記雰囲気流体の体積膨張率、ｇは重力加速度、νは前記雰囲気流体の動粘度、κは前記雰囲気流体の温度拡散率、Ｔ_０は前記穴の外側の前記雰囲気流体の温度、Ｔ_１は前記穴の内壁の温度、ａは前記穴の半径、ｌは前記穴の深さである。） The laser processing apparatus for holes according to the first aspect has a wall that partitions the outside and the inside, stores the processing sample inside, and transmits the laser light for guiding the laser light from the outside to the inside A processing sample storage container having an open window on the wall;
An atmospheric fluid pipe for introducing an atmospheric fluid into the processing sample storage container;
A pressure control unit for controlling the pressure inside the processing sample storage container;
A temperature control unit for controlling the temperature inside the processing sample storage container;
A laser optical system for introducing laser light from the outside into the inside through the window;
And the temperature of the ambient fluid inside the processing sample storage container by the pressure control unit and the temperature control unit so that the dimensionless temperature t ₁ obtained by the following formula is 300 or more. And the pressure is controllable, and convection of the atmospheric fluid is generated inside the hole formed in the processing sample to form a hole in the processing sample.

(Where α is the volume expansion coefficient of the ambient fluid, g is the acceleration of gravity, ν is the kinematic viscosity of the ambient fluid, κ is the temperature diffusivity of the ambient fluid, and T ₀ is the ambient fluid outside the hole. Temperature, T ₁ is the temperature of the inner wall of the hole, a is the radius of the hole, and l is the depth of the hole.)

  The hole laser processing apparatus according to the second aspect is the temperature and pressure of the atmospheric fluid inside the processing sample storage container by the pressure control unit and the temperature control unit in the first aspect. As the depth of the hole formed in the sample for processing increases, the first temperature and pressure condition at a temperature higher than the critical point of the atmospheric fluid and lower than the critical point is The second temperature and pressure condition is the same as the temperature of the first temperature and pressure condition, and the second temperature and pressure condition is higher than the critical point. The holes may be formed in the processing sample by sequentially shifting to the temperature and pressure condition of 3.

  The laser processing apparatus for holes according to a third aspect is the laser device according to the first or second aspect, wherein the laser optical system includes a central low-temperature layer and a high temperature on the inner wall side that are generated inside the hole formed in the processing sample. A laser beam may be incident on the processing sample inside from the outside through the window under a condition of an incident angle that satisfies a total reflection condition in the waveguide structure formed by a double layer with the layer.

  In the laser processing apparatus for holes according to a fourth aspect, in the third aspect, the laser optical system makes p-polarized laser light incident on the processing sample inside from the outside through the window portion. May be.

  The hole laser processing apparatus according to a fifth aspect is the light extracted from the inside of the hole formed in the processing sample to the outside through the window portion in any of the first to fourth aspects. You may further provide the camera which images the image by.

  In the laser processing apparatus for holes according to a sixth aspect, in the fifth aspect, the laser optical system is configured such that the laser beam for illumination enters the processing sample inside from the outside through the window portion. May be.

  In the laser processing apparatus for holes according to a seventh aspect, in the fifth or sixth aspect, the laser optical system is optimal for the processing sample detected based on an image captured by the camera. A laser beam may be incident on the processing sample inside from the outside through the window under the condition of an incident angle.

  In the laser processing apparatus for holes according to an eighth aspect, in the third aspect, the atmospheric fluid may be a supercritical fluid or a superfluid fluid.

（ここで、αは前記雰囲気流体の体積膨張率、ｇは重力加速度、νは前記雰囲気流体の動粘度、κは前記雰囲気流体の温度拡散率、Ｔ_０は前記穴の外側の前記雰囲気流体の温度、Ｔ_１は前記穴の内壁の温度、ａは前記穴の半径、ｌは前記穴の深さである。）
前記加工用試料にレーザ光を照射して、前記加工用試料に形成する前記穴の内部に前記雰囲気流体の対流を生じさせて、前記加工用試料に穴を形成するステップと、
を含む。 The laser processing method for holes according to the ninth aspect includes a step of arranging a processing sample in a partitioned area and introducing an ambient fluid around the processing sample;
Controlling the temperature and pressure of the ambient fluid around the processing sample so that the dimensionless temperature t ₁ obtained by the following formula is 300 or more;

(Where α is the volume expansion coefficient of the ambient fluid, g is the acceleration of gravity, ν is the kinematic viscosity of the ambient fluid, κ is the temperature diffusivity of the ambient fluid, and T ₀ is the ambient fluid outside the hole. Temperature, T ₁ is the temperature of the inner wall of the hole, a is the radius of the hole, and l is the depth of the hole.)
Irradiating the processing sample with laser light to cause convection of the atmospheric fluid inside the hole formed in the processing sample, and forming a hole in the processing sample;
including.

  The hole laser processing method according to a tenth aspect is the above ninth aspect, wherein the temperature and pressure of the ambient fluid around the processing sample is controlled to control the depth of the hole formed in the processing sample. As the depth increases, the temperature is equal to or higher than the critical point of the atmospheric fluid and is the same temperature as the temperature of the first temperature and pressure condition from the first temperature and pressure condition at a pressure lower than the critical point. After passing through the second temperature and pressure condition on the higher pressure side, the processing sample is sequentially shifted to a third temperature and pressure condition having the same temperature as the first temperature and pressure condition and the same density as the critical point. You may form a hole in.

  The laser processing method for holes according to an eleventh aspect according to the ninth or tenth aspect is based on a double layer of a central low temperature layer and a high temperature layer on the inner wall side that are generated inside the hole formed in the processing sample. A laser beam may be incident on the processing sample under an incident angle condition that satisfies the total reflection condition in the waveguide structure.

  In the hole laser processing method according to a twelfth aspect, in the eleventh aspect, p-polarized laser light may be incident on the processing sample to form a hole in the processing sample.

  In the laser processing method for holes according to a thirteenth aspect, in any one of the ninth to twelfth aspects, the step of capturing an image by light taken out from the inside of the hole formed in the processing sample is provided. Further, it may be included.

  The laser processing method for holes according to a fourteenth aspect is the method according to the thirteenth aspect, wherein the laser beam for illumination is incident on the processing sample and is taken out from the inside of the hole formed in the processing sample. You may take the picture by the light.

  The hole laser processing method according to the fifteenth aspect is the processing according to the thirteenth or fourteenth aspect, wherein the processing is performed under the condition of an optimal incident angle to the processing sample detected based on the captured image. Laser light may be incident on the sample for use.

  In the laser processing method for holes according to the sixteenth aspect, in any of the ninth to fifteenth aspects, a supercritical fluid or a superfluid fluid may be used as the atmospheric fluid.

  Hereinafter, a laser processing apparatus for holes and a laser processing method for holes according to embodiments will be described with reference to the accompanying drawings. In the drawings, substantially the same members are denoted by the same reference numerals.

(Embodiment 1)
FIG. 1 is a schematic diagram showing a configuration of a hole laser processing apparatus 20 according to the first embodiment. FIG. 2 is an enlarged view of the inside of the processing sample storage container 10 of FIG. 1 and 2 show the x axis, the y axis, and the z axis orthogonal to each other for convenience. The y-axis penetrates the paper surface from the front to the back. Each axis is provided for convenience of explanation, and is not for specifying the direction of the hole laser processing apparatus 20.
The hole laser processing apparatus 20 includes a processing sample storage container 10, an atmospheric fluid pipe 22, a pressure control unit 30, a temperature control unit 4, and laser optical systems 34 and 35. The processing sample storage container 10 has a wall 11 that partitions the outside and the inside, and stores a processing sample 13 inside, and a window portion through which laser light for guiding laser light 34 from the outside to the inside can be transmitted. 12 on the wall 11. The atmospheric fluid 15 is introduced into the processing sample storage container 10 by the atmospheric fluid piping 22. The pressure control unit 30 controls the pressure inside the processing sample storage container 10. The temperature control unit 4 controls the temperature inside the processing sample storage container 10. Laser light 34 is introduced from the outside to the inside through the window 12 by the laser optical systems 34 and 35.

（ここで、αは雰囲気流体１５の体積膨張率、ｇは重力加速度、νは雰囲気流体１５の動粘度、κは雰囲気流体１５の温度拡散率、Ｔ_０は穴１４の外側の雰囲気流体１５の温度、Ｔ_１は穴１４の内壁の温度、ａは穴１４の半径、ｌは穴１４の深さである。）
図１及び図２において、穴１４は、ｚ方向に沿って形成される。 In this hole laser processing apparatus 20, a processing sample storage container is provided by the pressure control unit 30 and the temperature control unit 4 so that the dimensionless temperature t ₁ obtained by the following Light Hill equation is 300 or more. 10 controls the temperature and pressure of the atmospheric fluid 15 inside. Thereby, the convection of the atmospheric fluid 15 is generated inside the hole 14 formed in the processing sample 13, and the hole 14 can be formed in the processing sample 13.
The formula of Light Hill is as the following formula (1).

(Where α is the volume expansion coefficient of the ambient fluid 15, g is the acceleration of gravity, ν is the kinematic viscosity of the ambient fluid 15, κ is the temperature diffusivity of the ambient fluid 15, and T ₀ is the ambient fluid 15 outside the hole 14. (T ₁ is the temperature of the inner wall of the hole 14, a is the radius of the hole 14, and l is the depth of the hole 14.)
1 and 2, the hole 14 is formed along the z direction.

(Function)
As shown in FIG. 5, the hole being processed has an open end and a closed end (processed end) at both ends of the hole, and the inside and outside of the hole are filled with atmospheric fluid. The inner wall of the hole 14 is hot due to the amount of heat supplied by the processing laser beam 34, and the ambient fluid 15 outside the hole 14 is cold. At this time, if the buoyancy generated in the high temperature portion is excellent in the frictional resistance of the fluid, the high temperature fluid is discharged out of the hole by the upward flow due to free convection. Instead, the low temperature fluid outside the hole moves to the bottom of the hole at the center of the hole 14. By flowing in, heat exchange and processing waste can be discharged. This is called an open siphon heat exchanger as a heat exchanger, and has been used for turbine blades of jet engines. Such a convection phenomenon is formulated by M. Lighthill, Quart. Journ. Mech. And Applied Math., Vol. VI, Pt. 4 (1953) p398-p439), and Hasegawa, S. Hasegawa, K. Nishikawa. , and K. Yamagata, Bulletin of JSME, Vol. 6, No. 22, 1963, p230-p250), and the theory of Light Hill reproduces the actual phenomenon within the range where laminar flow is maintained. It has been shown that it can.

The present inventor tried to apply the above-mentioned Light Hill equation to the analysis of the convection phenomenon in the machining hole, found the relationship between the control of the temperature and pressure conditions of the atmospheric fluid and the convection phenomenon in the machining hole, and reached the present invention. Is. FIG. 3A is a schematic diagram showing a state where the streamline 18 reaches the bottom of the hole 14 and convection occurs. FIG. 3B is a schematic diagram showing a state in which sufficient convection is not obtained as a whole with the staying portion 19 in which the streamline 18 does not reach the bottom of the hole 14, processing waste, surplus heat, etc. cannot move by convection. It is. According to this theory, it is theoretically shown that a general fluid that can be used at normal temperature and pressure, such as water and air, does not convect at all in a small-diameter deep hole formed by laser light (FIG. 3B). Convection ease, depending dimensionless temperature t _1, the scale of the machined hole, temperature, is centrally organized regardless of the ambient fluid used. If the dimensionless temperature t ₁ does not exceed 300 (≈10 ^2.5 ), a staying portion remains in the hole. For example, assuming that the hole diameter is 200 μm in water and air, convection does not occur even in a hole having a depth of 500 μm ( FIG. 3B). If convection does not occur, heat generated by machining is not effectively discharged, and machining waste generated by machining tends to accumulate in the hole.

Therefore, the present inventor has examined the use of supercritical fluids such as supercritical carbon dioxide as the atmospheric fluid. These supercritical fluids cause convection even in a narrow hole and improve heat and waste discharging performance. The right side of the above formula (1) includes items determined by processing conditions such as the size and temperature of the processing hole, as well as a coefficient portion (αg / νκ) determined by the atmospheric fluid such as α, g, ν, and κ. the supercritical carbon dioxide has a characteristic that these values are higher dimensionless temperature t ₁ all. As a result, as shown in FIG. 4, this coefficient portion (αg / νκ) is 10 ³ to 10 ⁶ times the dimensionless temperature t under a temperature and pressure condition of 20 ° C. or higher and 2 MPa or higher compared to water, air, etc. ₁ is high and convection is very likely (FIG. 3A). As a result, for example, at a critical point (approximately 31 ° C., 7.4 MPa), a convection can be obtained even in a hole of 1 m or more if the hole has a diameter of 200 μm. Note that the atmospheric fluid is not limited to the supercritical fluid, and may be any fluid as long as the dimensionless temperature t ₁ is 300 (10 ^2.5 ) or more. When the dimensionless temperature t ₁ is 300 or more, convection by the atmospheric fluid occurs in the entire hole from the bottom to the top of the hole in the hole. Further, the dimensionless temperature t ₁ exceeds 300 and is preferably about 10 ^3.6 (= 3981) because the convection momentum increases. On the other hand, the non-dimensional temperature t ₁ is increased convective momentum exceeds 10 ^3.6 dull, the risk of turbulent comes higher. Since elements due to turbulence is not only the dimensionless temperature t _1, 10 ^3.6 is not an absolute upper limit of the dimensionless temperature t _1, the dimensionless temperature t ₁ is 10 ^{3 Even if .6} is exceeded, turbulent flow does not always occur. On the other hand, generation of turbulent flow can be suppressed by setting the dimensionless temperature t ₁ to 10 ^3.6 or less.

Atmosphere fluid may be any non-dimensional temperature t ₁ is 300 or more, not limited to a supercritical state, the critical point, subcritical state, or may be a non-critical state. Further, the atmospheric fluid may be, for example, a cryogenic ⁴ He or ³ He superfluid fluid. Furthermore, the atmospheric fluid is not limited to carbon dioxide, and for example, methane (critical point 190.4K, 4.60 MPa), ethane (critical point 305.3K, 4.87 MPa), ethanol (critical point 513.9K, 6.14 MPa). ), Acetone (critical point 508.1K, 4.70 MPa), water (critical point 647.3K, 22.12 MPa), or the like may be used.

  In the hole laser processing apparatus 20, the processing sample 13 is sealed in the processing sample storage container 10, the atmosphere fluid 15 is introduced into the processing sample storage container 10, and the internal temperature and pressure conditions are controlled. The laser beam 34 is introduced through the window portion 12 provided on the wall 11 to perform laser processing. Therefore, this hole laser processing apparatus 20 can be organized into four systems such as a structural system such as the processing sample storage container 10 and the like, introduction of atmospheric fluid and its pressure control system, temperature control system, and laser optical system.

<Structural system such as sample storage container for processing>
The processing sample 13 is enclosed in the processing sample storage container 10. The processing sample storage container 10 is further disposed in the thermostat 1 for temperature control. In addition, the processing sample storage container 10 is provided with a pressure-resistant window 12 for allowing the laser beam to pass through the wall 11. In addition, as the window part 12, in the case of a transparent material, it is a laser beam for processing on the surface opposite to the side where holes are formed, and in the case of an opaque material, a processing laser is formed on the surface where holes are formed. Two light incident windows and two camera observation windows are preferably provided. The processing sample storage container 10 is connected to the pressure adjustment container 26. In order to obtain the maximum effect of convection, it is desirable that the actual window part is installed at the upper part and / or the lower part of the container because the opening part of the processing hole must always face upward. That is, the window part is provided in the upper part and / or the lower part in the z-axis direction. In addition, although the convection effect cannot be obtained when the opening end of the hole is downward, the convection effect can be obtained in the lateral direction (x direction or y direction), although the effect is inferior.
Further, the processing sample storage container 10 can be moved in the z-axis direction by the driving unit 16 and can adjust the focal position of the laser optical system to an appropriate position of the hole as the depth of the hole increases. .

<Temperature control system>
In this hole laser processing apparatus 20, temperature control in the thermostat 1 and the processing sample storage container 10 therein is performed by a heating device 2 that heats the thermostat 1, a temperature sensor 3, and a temperature control unit 4. Yes.

<Pressure control system>
The liquefied carbon dioxide, which is an atmospheric fluid, is transferred from the liquefied carbon dioxide container 21 to the processing sample storage container 10 via the pipe 22, the valve 23, the MFC (mass flow controller) 24, the leak valve 25, the pressure adjustment container 26, and the closing valve 27. Filled with a pump (not shown). Further, when liquefied carbon dioxide or a pump cannot be used, the pressure adjusting container 26 may be filled with a necessary amount of dry ice and filled into the processing sample storage container 10 via the closing valve 27. There are two pressure vessels to be used, which are connected to each other by piping and have different roles. One pressure vessel is a processing sample storage container 10 for storing the processing sample 13, and includes a pressure-resistant window 12 through which a laser beam 34 is incident. The other pressure vessel is a pressure adjustment vessel 26 for pressure adjustment. The pressure in the processing sample storage container 10 is controlled by the pressure sensor 29 and the pressure control unit 30 in the pressure adjusting container 26 which is the other connected pressure container, and the temperature of the processing sample storage container 10 is adjusted. By doing so, the temperature and pressure in the processing sample storage container 10 are controlled. The pressure in the pressure adjusting container 26 can also be adjusted by heating with the heating device 28. At this time, since the piping connecting the two pressure vessels 10 and 26 is sufficiently thin and long, the pressure between the vessels is the same, but the temperature is independent. Therefore, the pressure and temperature can be controlled by separate feedback controls. The accuracy of temperature and pressure control required for experiments near the critical point (point e in FIG. 4) requires high accuracy of 0.01 MPa and 0.01 ° C. Therefore, the method for controlling both temperature and pressure has a limit in accuracy. . For this reason, the density inside the processing sample storage container 10 is made constant by automatically shutting off the piping valve between the two pressure vessels at the moment when the temperature and pressure conditions are within the allowable range, and stabilized near the critical point only by temperature control. Let Stabilization can be realized by monitoring the temperature sensor 7 in addition to the thermostat 1 and using high-speed temperature control using the Peltier element control unit 8 by heating and cooling by the Peltier element 6 in combination. Further, exhaust from the processing sample storage container 10 is performed via a discharge pipe 31, a leak valve 32, and an MFC (mass flow controller) 33. Further, since the exhaust is accompanied by rapid cooling, the exhaust rate is controlled by using the Peltier element control unit 8 so that the temperature in the processing sample storage container 10 is stabilized while heating by the thermostat 1 and the Peltier element 6. Performs exhaust valve feedback to be controlled.

<Laser optical system>
The laser beam 34 is introduced into the processing sample storage container 10 through the window 12 provided on the wall 11 of the processing sample storage container 10. The hole 14 is formed by the laser beam 34 that has reached the processing sample 13. In order to determine the optimum incident angle of the laser beam 34 for processing, for example, monitoring may be performed as shown in a fifth embodiment described later. In this case, a laser beam for illumination may be irradiated instead of the laser beam for processing. When the illumination light is collected at the opening of the hole 14, only the light ray that has entered through the temperature boundary layer outside the hole and incident at an incident angle that can propagate through the hole reaches the hole bottom. And only the light ray that can propagate out of the hole is returned to the condenser lens. The return light is collimated by the condensing lens and detected by a camera (not shown in FIG. 1, “coupling monitor 48” in FIG. 7). The optimal incident angle of the light beam can be obtained depending on the detection position of the camera, and the beam profile of the processing laser beam can be adjusted so that the light can be condensed at the incident angle.

  As a method for adjusting the beam profile, various means such as a light intensity modulation device using a liquid crystal polarizing element and a beam diameter expansion / contraction device using a beam expander can be considered at the position 45 in FIG. If a liquid crystal polarizing element is used, the polarization distribution in the beam can also be controlled. In order to make p-polarized light and s-polarized light enter the hole, radial polarized light and azimuth polarized light are generated, respectively. Various types of polarized light can be considered, such as polarized light having more complex polarization. In addition, by providing an element having a polarization measurement function in front of the coupling monitor 48, the polarization state and its distribution easily passing through the hole are measured and reflected in the incident polarization distribution, thereby including the incident light including the polarization. Beam optimization can be performed. For example, an optical element that gives a polarization measurement function enters the position of reference numeral 47. However, an axially symmetric polarized beam generator similar to that used for reference numeral 45 can be used as having the same function. . However, at the position of reference numeral 47, it is necessary to make the light incident direction opposite to that arranged at reference numeral 45.

(Embodiment 2)
FIG. 4 is a schematic diagram showing temperature-pressure dependence of the coefficient part (αg / νκ) of the Light Hill equation. Note that only the exponent of the value of the coefficient part (αg / νκ) is displayed on the contour lines in FIG. FIG. 4 shows nine points from point a to point i in a range in which the horizontal axis indicates temperature and the vertical axis indicates pressure, and indicates the temperature-pressure condition. Among these nine points, points a, b, and c are arranged on the same density line from the low temperature side to the high temperature side. The points d, e, and f are arranged on the same density line from the low temperature side to the high temperature side. This e point is a critical point. The points g, h, and i are arranged on the same density line from the low temperature side to the high temperature side. On the other hand, points a, d, and g are arranged on the same temperature line. Further, the points b, e, and h are arranged on the same temperature line. The points c, f and i are arranged on the same temperature line. In addition, each point other than e point of a critical point is an illustration, Comprising: It is not limited to these.

As shown in FIG. 4, the value of the coefficient part (αg / νκ) becomes the largest near the critical point (point e in FIG. 4) (about 10 ¹⁶ or more (diverging to practically infinite ∞ at the critical point). It is difficult to measure accurate values)). Also, at a pressure below the critical point, the value of the coefficient part (αg / νκ) decreases from 10 ¹³ to 10 ¹² . On the other hand, in the pressure range above the critical point, the value of the coefficient part (αg / νκ) somewhat decreases because the kinematic viscosity increases with the increase in density due to the pressure increase. That is, the coefficient part (αg / νκ) has a high value of about 10 ¹⁵ along a line (Wisdom's Line) of the same density extending from the critical point to the high temperature and high pressure side, and the coefficient is low on the low pressure side from the above line. The value of the part (αg / νκ) decreases rapidly to about 10 ¹² . On the other hand, on the high pressure side from the above line, the value of the coefficient part (αg / νκ) slightly decreases due to the increase in density due to the increase in pressure as described above, but only decreases from 10 ¹⁴ to 10 ¹³ .
In normal temperature water and air, the values of the coefficient part (αg / νκ) of the Light Hill equation are 1.08 × 10 ⁸ and 1.83 × 10 ⁶ , respectively.

In the laser processing apparatus for holes according to the second embodiment, the temperature of the atmospheric fluid 15 inside the processing sample storage container 10 and the temperature are controlled by the pressure control unit 30 and the temperature control unit 4 according to the depth of the holes 14. It is characterized by controlling the pressure. That is, as the depth of the hole 14 formed in the processing sample 13 becomes deeper, the temperature is higher than the critical point of the atmospheric fluid 15 and is lower than the critical point at the first temperature and pressure condition (for example, FIG. 4). From the point i and point h), the second temperature and pressure condition (for example, points c and b in FIG. 4) is the same as the temperature of the first temperature and pressure condition and higher than the critical point. 1 is shifted to a third temperature and pressure condition (for example, point f and point e in FIG. 4) having the same density as the critical point and the same density as the critical point. Form. As a result, when the depth of the hole 14 is shallow, the hole may be formed so as not to generate turbulent flow under the condition (10 ¹² ) where the value of the coefficient part (αg / νκ) of the Light Hill equation is relatively small. it can. Furthermore, it can be set as the temperature-pressure condition in which the convection inside the hole 14 occurs under the condition (10 ¹⁴ to 10 ¹⁵ ) where the value of the coefficient portion (αg / νκ) is relatively large as the hole becomes deeper.

(Function)
For convection occurs inside the hole dimensionless temperature t ₁ is but need more than 300, as described above, it does not mean that the higher the better, but preferred to increase the degree of convection until 10 ^3.6 When it gets higher, it becomes turbulent. At this time, the transport phenomenon becomes active between the upward flow and the downward flow, and the effects of heat exchange and mass exchange are difficult to reach the bottom of the hole. Therefore, the dimensionless temperature t ₁ needs to be maintained within a range where laminar flow is maintained. Considering this in an actual machining process, the hole depth increases as the machining progresses. Therefore, in order to keep the dimensionless temperature t ₁ within a certain range, the coefficient part (αg / νκ) of the Light Hill equation It is necessary to keep the state of convection constant by adjusting this part as the hole depth increases. From the calculation result of FIG. 4, for example, as an initial state, the coefficient portion (αg / νκ) is started by starting from the state of point i in the figure and moving to the state c point and the state f point as the hole depth increases. By increasing the value of, drilling can be gradually advanced while maintaining a laminar flow. Further, the value of the coefficient portion (αg / νκ) can be maximized by approaching the state e point which is a critical point. For example, when machining the hole diameters of 200 μm, 100 μm, and 50 μm, the temperature part is relayed to the state of i point → c point → f point → e point shown in FIG. / Νκ) can be increased. Alternatively, as another example, it is possible to start from the state h point and shift to the state b point and the state e point as the hole depth increases.

(Embodiment 3)
FIG. 5A is a schematic diagram showing a state of laser light incident on the hole, and FIG. 5B shows a laser generated in the boundary layer 44 between the cold part 42 and the warm part 43 in the atmosphere around the hole. FIG. 5C is a schematic diagram showing total reflection of laser light generated in the boundary layer 44 between the cold part 42 and the warm part 43 inside the hole.
In the laser processing apparatus for holes according to the third embodiment, the laser optical system is a waveguide formed by a double layer of a low temperature layer 42 at the center and a high temperature layer 43 on the inner wall side that is formed inside the hole 14 formed in the processing sample 13. The laser beam 34 is incident on the processing sample 13 from the outside through the window 12 under the condition of an incident angle that satisfies the total reflection condition in the structure. As a result, the laser beam 34 is totally reflected by the waveguide structure formed by the double layer of the central low temperature layer 42 and the inner wall side high temperature layer 43 generated inside the hole 14 and can reach the hole bottom without attenuation.

(Function)
According to FIG. 5A showing the state of convection, a temperature boundary layer 44 is formed between the low temperature part 42 near the center of the hole 14 and the high temperature part 43 around the outer wall of the hole 14 along with the convection 41. Yes. A difference in temperature represents a difference in density, and a difference in density is a difference in refractive indexes n ₁ and n ₂ . The presence of the temperature boundary layer 44 is the presence of a boundary layer having refractive indexes n ₁ and n ₂ , and has a function of refracting and reflecting light. The refractive index distribution in the processed hole has a high refractive index n _{1 at the} center and a low refractive index n ₂ (<n ₁ ) near the outer wall, which indicates that this is the same refractive index structure as the optical fiber. That is, a waveguide structure is formed in the hole. Therefore, by making the processing laser beam 34 incident on the temperature boundary layer 44 at an angle that makes total reflection or more, it becomes possible to propagate the inside of the hole without attenuation by repeating total reflection, and deep hole processing is possible. It becomes. In addition, when the inner wall temperature of the processed hole decreases due to the progress of cooling, the temperature difference of the temperature boundary layer 44 is reduced and the optical waveguide function is weakened. In this case, the transmitted light component indicated by the broken line arrow in FIG. Since the inner wall of the hole that has appeared and the temperature has decreased is heated, the temperature is increased again to regenerate the optical waveguide. As described above, once an optical waveguide having a two-layer structure of atmospheric fluid is formed, the optical waveguide is repaired and maintained as long as light is continuously incident.

(Embodiment 4)
FIG. 6 is a graph showing a relationship of reflectance with respect to incident angles of p-polarized light (radial polarized light) and s-polarized light (azimuth polarized light). As shown in FIG. 6, radial polarized light (p-polarized light) has an angle (Brewster angle) at which the incident angle is low and the reflectance is 0.
In the hole laser processing apparatus and laser processing method according to Embodiment 4, the incident angle from the low temperature portion 42 around the hole 14 to the high temperature portion 43 is matched with the incident angle (Brewster angle) at which the reflectance is zero. It is characterized by. As a result, when laser light is incident on the hole 14 from the outside, the boundary layer 44 between the low temperature portion 42 and the high temperature portion 43 formed around the hole 14 can be completely transmitted. Thereby, attenuation of transmitted light due to reflection at the boundary layer 44 around the hole 14 (broken arrow in FIG. 5B) can be suppressed, and the laser light 34 can be efficiently incident into the hole 14. .

(Function)
Reflection and refraction characteristics due to changes in refractive index are affected by polarization, and p-polarized light and s-polarized light have different dependency on reflectance and transmittance with respect to the incident angle. As shown in an example in FIG. 6, in axially symmetric processing such as a hole, when the radial polarization is p-polarization and azimuth polarization, s-polarization is incident. Here, when the incident angle exceeds a certain angle, total reflection occurs, and in the case of radial polarized light (p-polarized light), the transmittance becomes 100% at a certain angle. Here, in the case of FIG. 5, it can be seen that light is incident from the high refractive index region (low temperature portion 42) to the low refractive index region (high temperature portion 43) at the entrance and inside the hole. In out-of-hole convection, reflection occurs depending on the incident angle, and decoupling occurs so that light does not enter the processed hole. However, by using radial polarization (p-polarization) and appropriately controlling the convection form and the incident angle, The boundary layer 44 between the low temperature part 42 and the high temperature part 43 can be completely transmitted. On the other hand, since the incident angle is larger in the boundary layer 44 between the high refractive index region (low temperature portion 42) and the low refractive index region (high temperature portion 43) of the waveguide in the hole, total reflection occurs. As described above, by controlling the incident angle and the polarization, it is possible to make the coupling efficiency and the transmission efficiency substantially non-attenuated. In addition, when maintaining the convection by irradiating the processing sample 13 with light, azimuth polarized light may be incident coaxially. For controlling the polarization, for example, an axially symmetric polarized beam generator may be used.

(Embodiment 5)
FIG. 7 is a schematic view showing the incidence and emission of laser light on the processing sample 13 which is an opaque material and a transparent material in the hole laser processing apparatus according to the fifth embodiment. FIG. 8A is a schematic diagram showing an example of output from the coupling monitor 48 of FIG. FIG. 8B is a schematic diagram illustrating an example of output from the processing hole observation camera 50 of FIG. 7 is a surface on the side where the hole 14 is provided, and the surface B is a surface opposite to the side where the hole 14 is provided. FIG. 7 shows that the incident surface of the laser beam 34 can be appropriately selected depending on whether the processing sample 13 is an opaque material or a transparent material. That is, when the processing sample 13 is an opaque material, the laser beam 34 is incident from the surface A. On the other hand, when the processing sample 13 is a transparent material, the laser beam 34 can be incident from the surface B.
The laser processing apparatus for holes according to the fifth embodiment is different from the laser processing apparatus for holes according to the first embodiment in that a coupling monitor 48 and a processing hole observation camera 50 are provided. As shown in FIG. 7, incident light such as processing laser light and illumination light is reflected by the half mirror 46 a via the axially symmetric polarized beam generator arranged at the position of 45, and is holed by the condenser lens 35. The light is condensed toward the inside of 14. The condensed light reaches the hole bottom via the waveguide structure in the hole 14. For example, when an axially symmetric polarized beam generator is provided at the position of 45, axially symmetric radial and azimuth polarized light can be generated. Further, an optical device including a beam diameter adjustment function, a beam intensity distribution adjustment function, and the like may be provided at the position denoted by reference numeral 45, for example.

  The light from the inside of the hole 14 goes straight through the half mirror 46 a, and the light that goes straight through the next half mirror 46 b reaches the coupling monitor 48 via the polarization distribution analyzer 47. On the other hand, the light reflected by the half mirror 46 b forms an image of the processed hole by the processed hole observation camera 50 through the imaging lens 49. In the coupling monitor 48, for example, as shown in FIG. 8A, an angle corresponding to the optimum incident angle is brightly reflected in the ring shape 52. Therefore, the optimum incident angle can be detected by the coupling monitor 48. Further, with the processing hole observation camera 50, for example, as shown in FIG. 8B, the opening portion of the hole 14 having the hole diameter 54 on the surface of the processing sample 13 can be observed.

(Function)
The angle of incidence appropriate for actual laser processing varies with changes in the processing depth of laser processing, changes in conditions, and time. Therefore, in the hole laser processing apparatus according to the fifth embodiment, by monitoring the processing state, an ideal incident angle can be determined as needed, and appropriate processing can always be performed by following the incident conditions. The monitoring is performed by observing the processed hole from the opening side of the hole 14. Specifically, a coupling monitor 48 and a processing hole observation camera 50 are provided. If the laser beam can be coupled normally in the vicinity of the machining hole and can reach the inside of the machining hole without attenuation, the reflection of the light reaching the bottom of the hole and the light emission during machining at the bottom of the hole should be visible from outside the hole. is there. Therefore, it is possible to determine whether or not the hole bottom can be processed by observing light coming out of the hole and out of the hole. As shown in FIG. 8A, a specific angle θ that is incident at the total reflection angle at the refractive index boundary layer of the inner wall surface of the hole, is introduced into the hole without attenuation, and satisfies the condition of being reflected at the bottom of the hole. The light beam that passes through is reflected brightly in the ring shape 52 corresponding to the specific angle. By detecting this specific angle θ, an optimum incident angle can be obtained. Coupling monitor 48, it can also be used as hole depth detector, which can be fed back to the control of the dimensionless temperature t _1. If the depth of the hole changes, the brightness of the ring and the angle θ also change. However, if the dimensionless temperature t ₁ becomes insufficient with respect to the hole depth, the progress of the hole stops and these changes also stop. Therefore, the temperature of the dimensionless temperature t ₁ atmosphere fluid, a feedback sensor for measuring the timing of raising a pressure control. Moreover, the opening of the hole 14 on the surface of the processing sample 13 can be observed by the processing hole observation camera 50, and focusing on the hole can be performed.

  Using the hole laser processing apparatus and the laser processing method according to the present invention, it is shown by the Light Hill theory that a hole having a radius of 100 μm can maintain convection even at a hole depth of 1 m. In other words, it shows that the machining waste removal performance by convection can be maintained even at such a depth, and a hole having such a depth may actually be opened. Such a high-aspect (about 5000) narrow hole is unprecedented and is expected to contribute to unprecedented manufacturing in various fields. For example, when a large number of pores are provided in a metal material, a light porous material having a very large surface area can be obtained. If the pores are filled with a refrigerant having high heat exchange efficiency, it can be used as a material for heat exchange. When the surface area is simply compared, the hole diameter and the surface area are in inverse proportion even with the same removal volume. Therefore, the heat exchanger that has been processed to have a large-diameter hole or groove can be reduced in diameter by this technique to improve the efficiency.

  Further, if fine pores can be freely formed in the bulk transparent material, a microfluidic device such as μTAS can be formed without going through the two-dimensional flow path laminating step. Since the processing method according to the present invention is a physical removal process that does not involve chemical treatment, it is a simple manufacturing method regardless of the material. Therefore, the degree of freedom in designing the fluid device can be increased, and the appearance of a more advanced device can be expected. In addition, high-mix low-volume production that does not assume mass production is possible. For example, in an artificial organ, the density of microchannels simulating capillaries is important, but the thickness of the substrate of the two-dimensional channel defines the limit of integration. With the hole laser processing apparatus and processing method according to the present invention capable of deep hole processing as described above, it is possible to drill such a flow path in the same pattern as an actual capillary blood vessel, which is close to a real organ. This leads to the development of artificial organs. Moreover, improvement of reliability can be expected for power devices such as microthrusters by eliminating the lamination process.

  It should be noted that the present disclosure includes appropriately combining any of the various embodiments and / or examples described above, and each of the embodiments and / or examples. The effect which an Example has can be show | played.

  In the laser processing apparatus and laser processing method for holes according to the present invention, a deep hole having a high aspect ratio, which is a hole diameter with respect to the hole depth, can be formed for both the transparent material and the opaque material.

1 Temperature chamber 2 Heating device 3 Temperature sensor (temperature chamber)
4 Temperature controller 6 Peltier element 7 Temperature sensor (container)
8 Peltier element control unit 10 Sample storage container 11 Wall 12 Window 13 Processing sample 14 Hole 15 Atmospheric fluid 16 Drive unit 18 Stream line 19 Retention unit 20 Hole laser processing device 21 Liquid carbon dioxide (liquefied carbon dioxide) container 22 Carbon dioxide piping 23 Valve 24 MFC (mass flow controller)
25 Leak valve 26 Pressure regulating container 27 Closure valve 28 Heating device 29 Pressure sensor 30 Pressure control unit 31 Discharge piping 32 Leak valve 33 MFC (mass flow controller)
34 Laser light 35 Objective lens 41 Convection 42 Atmospheric fluid (cold part), low temperature layer 43 Atmospheric fluid (warm part), high temperature layer 44 Boundary layer (temperature boundary layer)
45 Axisymmetric polarized beam generator, beam diameter adjuster, beam intensity distribution adjuster 46a, 46b Half mirror 47 Polarization distribution analyzer 48 Coupling monitor 49 Imaging lens 50 Processing hole observation camera 52 Ring-shaped high brightness part 54 Hole diameter

Claims (16)

A processing sample storage container having a wall for partitioning the outside and the inside, storing a processing sample inside, and having a window portion on the wall through which the laser light can be transmitted to guide the laser light from the outside to the inside When,
An atmospheric fluid pipe for introducing an atmospheric fluid into the processing sample storage container;
A pressure control unit for controlling the pressure inside the processing sample storage container;
A temperature control unit for controlling the temperature inside the processing sample storage container;
A laser optical system for introducing laser light from the outside into the inside through the window;
And the temperature of the ambient fluid inside the processing sample storage container by the pressure control unit and the temperature control unit so that the dimensionless temperature t ₁ obtained by the following formula is 300 or more. And a laser processing apparatus for a hole that is capable of controlling a pressure and that forms a hole in the processing sample by causing convection of the atmospheric fluid in the hole formed in the processing sample.

(Where α is the volume expansion coefficient of the ambient fluid, g is the acceleration of gravity, ν is the kinematic viscosity of the ambient fluid, κ is the temperature diffusivity of the ambient fluid, and T ₀ is the ambient fluid outside the hole. Temperature, T ₁ is the temperature of the inner wall of the hole, a is the radius of the hole, and l is the depth of the hole.)   The pressure control unit and the temperature control unit control the temperature and pressure of the atmospheric fluid inside the processing sample storage container to increase the depth of the hole formed in the processing sample. Accordingly, from the first temperature and pressure condition at a temperature higher than the critical point of the atmospheric fluid and lower than the critical point, the temperature is the same as the temperature of the first temperature and pressure condition and higher than the critical point. After passing through the temperature and pressure conditions of 2, the holes are formed in the processing sample by sequentially shifting to the third temperature and pressure conditions having the same temperature as the first temperature and pressure conditions and the same density as the critical point. The laser processing apparatus for holes according to claim 1.   The laser optical system includes the window under the condition of an incident angle satisfying a total reflection condition in a waveguide structure including a double layer of a central low temperature layer and an inner wall side high temperature layer formed inside a hole formed in the processing sample. The laser processing apparatus for holes according to claim 1 or 2, wherein a laser beam is incident on the processing sample inside from outside through a section.   4. The laser processing apparatus for holes according to claim 3, wherein the laser optical system makes p-polarized laser light incident on the processing sample inside from the outside through the window portion. 5.   The hole laser according to any one of claims 1 to 4, further comprising a camera that captures an image of light extracted from the inside to the outside of the hole formed in the processing sample through the window. Processing equipment.   The hole laser processing apparatus according to claim 5, wherein the laser optical system makes illumination laser light incident on the processing sample inside from the outside through the window portion.   The laser optical system applies a laser beam from the outside to the internal processing sample through the window under the condition of an optimal incident angle to the processing sample detected based on an image captured by the camera. The laser processing apparatus for holes according to claim 5 or 6, wherein light is incident.   The laser processing apparatus for holes according to any one of claims 1 to 7, wherein the atmospheric fluid is a supercritical fluid or a superfluid fluid. Placing the processing sample in the partitioned area and introducing an ambient fluid around the processing sample;
Controlling the temperature and pressure of the ambient fluid around the processing sample so that the dimensionless temperature t ₁ obtained by the following equation is 300 or more;

(Where α is the volume expansion coefficient of the ambient fluid, g is the acceleration of gravity, ν is the kinematic viscosity of the ambient fluid, κ is the temperature diffusivity of the ambient fluid, and T ₀ is the ambient fluid outside the hole. Temperature, T ₁ is the temperature of the inner wall of the hole, a is the radius of the hole, and l is the depth of the hole.)
Irradiating the processing sample with laser light to cause convection of the atmospheric fluid inside the hole formed in the processing sample, and forming a hole in the processing sample;
A method for laser processing for holes, comprising:   The temperature and pressure of the ambient fluid around the processing sample are controlled, and as the depth of the hole formed in the processing sample becomes deeper, the critical temperature is equal to or higher than the critical point of the ambient fluid. From the first temperature and pressure condition lower than the point, the first temperature and pressure condition passes through the second temperature and pressure condition that is the same as the temperature of the first temperature and pressure condition and higher than the critical point. The hole laser processing method according to claim 9, wherein the hole is formed in the processing sample by sequentially shifting to a third temperature and pressure condition having the same density as the critical point and the same density as the critical point.   A laser beam is applied to the processing sample under the condition of an incident angle satisfying the total reflection condition in the waveguide structure of the double layer of the central low temperature layer and the inner wall side high temperature layer generated inside the hole formed in the processing sample. The laser processing method for holes according to claim 9 or 10, which is incident.   The hole laser processing method according to claim 11, wherein a hole is formed in the processing sample by injecting p-polarized laser light into the processing sample.   The laser processing method for holes according to any one of claims 9 to 12, further comprising a step of capturing an image by light extracted from the inside of the hole formed in the processing sample to the outside.   14. The laser processing method for holes according to claim 13, wherein an image of a laser beam for illumination is incident on the processing sample, and an image is picked up by light extracted from the inside of the hole formed in the processing sample.   The laser processing method for holes according to claim 13 or 14, wherein laser light is incident on the processing sample under a condition of an optimum incident angle to the processing sample detected based on the captured image.   The laser processing method for holes according to any one of claims 9 to 15, wherein a supercritical fluid or a superfluid fluid is used as the atmospheric fluid.

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