JP2013041124A - Infrared optical film, scan mirror and laser beam machine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an infrared optical film capable of resolving polarization anisotropy of a laser beam according to oscillation of a scan mirror while realizing high reflectance.SOLUTION: An infrared optical film includes a gold (Au) film 2 of 0.01-1.0 μm thick formed on a substrate 1 and, on the gold film 2, a low refractive index layer with refractive index nL of 1.3-1.4 and a high refractive index layer refractive index nH of 1.9-2.1 are alternately arranged, in such a manner as a first layer 3a: 0.26λ≤nLd1≤0.28λ, a second layer 4a: 0.25λ≤nHd2≤0.26λ, a third layer 3b: 0.25λ≤nLd3≤0.27λ, a fourth layer 4b: 0.22λ≤nHd4≤0.24λ, a fifth layer 3c: 0.21λ≤nLd5≤0.23λ, a sixth layer 4c: 0.17λ≤nHd6≤0.19λ, a seventh layer 3d: 0.16λ≤nLd7≤0.18λ, and an eighth layer 4d: 0.17λ≤nHd8≤0.20λ (where, λ represents laser beam wavelength, d1-d8 represent film thickness of respective layers).

Description

  The present invention relates to an infrared optical film, a scan mirror, and a laser processing machine that are applied to a scan mirror used in a laser processing machine for drilling a printed circuit board or the like, and in particular, can form a highly accurate processing hole. Is.

  As a technology that supports the recent digital consumer electronics market, there is a laser processing technology for forming fine holes in a printed circuit board. In a laser processing machine for drilling, an optical mirror called a scan mirror is swung about a rotation axis, and a laser beam is scanned on a workpiece. This enables efficient drilling, and the latest model achieves a processing speed of about 2000 holes / minute. In order to reflect high-energy laser light, an infrared optical film having high reflectivity is formed on the surface of the scan mirror. An Au mirror is generally known as the most versatile reflection mirror. The reflectance of the Au mirror is about 99.0%.

  In view of the lack of mechanical strength of Au films in conventional infrared optical films, laser reflectors in which a Cr layer, an Au layer, and a Mo layer are formed in order from the substrate side have been proposed (for example, patents) Reference 1). However, in this case, there is a problem that the reflectance is lower than that of the Au mirror.

  In another conventional infrared optical film, a Cr layer and an Au layer of a metal film are formed from the substrate side, and a ZnSe layer, a Ge layer, a ZnSe layer, and a Ge layer are sequentially formed thereon, and the reflectance is increased. An infrared laser reflecting mirror to be enhanced has been proposed (for example, see Patent Document 2). In this case, the reflectance is 99.5% or more.

  In addition, other conventional infrared optical films have proposed circular polarization mirrors that circularly polarize laser light having a wavelength of 10.6 μm when used at an incident angle of 45 degrees (for example, Patent Document 3 and Patent Document). 4). By using the circularly polarized mirror, it is possible to prevent the inclination of the cut surface in laser processing of a sheet metal or the like.

Japanese Patent Laid-Open No. 5-228677 JP 2003-302520 A Japanese Patent No. 2850683 Japanese Patent No. 2850684

  In a conventional laser drilling machine, a laser oscillator that oscillates linearly polarized laser light is used to construct an optical system. When drilling a printed circuit board, if the laser beam is linearly polarized, the processed hole becomes elliptical due to the difference in the absorption rate of the P wave / S wave. FIG. 34 shows the absorption rate of copper (Cu) with respect to the incident angle. When the incident angle is 10 degrees or more, the absorption rate of the P wave is larger than the absorption rate of the S wave. That is, when linearly polarized laser light is used, anisotropy exists in the absorption, and the machining hole becomes elliptical. The Au mirror described above and the reflection mirror proposed in Patent Document 1 and Patent Document 2 do not have a function of controlling the phase difference between the P wave and the S wave, and the polarization anisotropy cannot be eliminated. Therefore, when these reflecting mirrors are applied to a scan mirror of a drilling laser processing machine, linearly polarized laser light emitted from an oscillator is used as it is for processing a printed circuit board. That is, there is a problem that the processed hole becomes elliptical.

  In addition, when the circularly polarized mirror proposed in Patent Document 3 and Patent Document 4 is applied to a scan mirror, the polarization anisotropy cannot be eliminated with a laser drilling machine that uses laser light with a wavelength of 9.28 μm. The laser beam cannot be circularly polarized. That is, there is a problem that the processed hole becomes elliptical.

  Furthermore, the circularly polarizing mirror normally used with a fixed incident angle does not have a polarization control function that allows the scanning mirror to oscillate, and has a problem that the processed hole becomes elliptical.

  The present invention has been made to solve the above-described problems. An infrared optical film, a scan mirror, and a laser processing machine capable of eliminating polarization anisotropy and forming a highly accurate processing hole are provided. The purpose is to provide.

The infrared optical film of the present invention is
A gold (Au) film formed on a substrate to a thickness of 0.01 to 1.0 μm, a low refractive index layer having a refractive index nL of 1.3 to 1.4 on the gold film, and a refractive index Infrared optical film in which n layers of 1.9 to 2.1 and high refractive index layers are alternately stacked, and each of the first to eighth layers is laminated.
The optical film thickness of each of the layers is from the gold film side to the first layer 0.26λ ≦ nLd1 ≦ 0.28λ,
The second layer 0.25λ ≦ nHd2 ≦ 0.26λ,
The third layer 0.25λ ≦ nLd3 ≦ 0.27λ,
The fourth layer 0.22λ ≦ nHd4 ≦ 0.24λ,
The fifth layer 0.21λ ≦ nLd5 ≦ 0.23λ,
The sixth layer 0.17λ ≦ nHd6 ≦ 0.19λ,
The seventh layer 0.16λ ≦ nLd7 ≦ 0.18λ,
The eighth layer 0.17λ ≦ nHd8 ≦ 0.20λ,
(Where, λ = wavelength of laser light, d1 to d8 are film thicknesses of the respective layers).

The infrared optical film of the present invention is
A gold (Au) film formed on a substrate to a thickness of 0.01 to 1.0 μm, a low refractive index layer having a refractive index nL of 1.3 to 1.4 on the gold film, and a refractive index Infrared optical film in which n layers of 1.9 to 2.1 and high refractive index layers are alternately stacked, and each of the first to eighth layers is laminated.
The optical film thickness of each of the layers is from the gold film side to the first layer 0.26λ ≦ nLd1 ≦ 0.28λ,
The second layer 0.25λ ≦ nHd2 ≦ 0.26λ,
The third layer 0.25λ ≦ nLd3 ≦ 0.27λ,
The fourth layer 0.22λ ≦ nHd4 ≦ 0.24λ,
The fifth layer 0.21λ ≦ nLd5 ≦ 0.23λ,
The sixth layer 0.17λ ≦ nHd6 ≦ 0.19λ,
The seventh layer 0.16λ ≦ nLd7 ≦ 0.18λ,
The eighth layer 0.17λ ≦ nHd8 ≦ 0.20λ,
(Where λ is the wavelength of the laser beam, and d1 to d8 are the film thicknesses of the above layers),
While realizing high reflectivity, the processing hole is rounded by eliminating the polarization anisotropy of the laser light according to the swing of the scan mirror.

It is sectional drawing which shows the structure of the infrared optical film of Embodiment 1 of this invention. It is sectional drawing which shows the other structure of the infrared optical film of Embodiment 1 of this invention. It is sectional drawing which shows the other structure of the infrared optical film of Embodiment 1 of this invention. It is a figure which shows the structure of the film-forming apparatus which forms the infrared optical film shown in FIG. It is a figure which shows the structure of the scan mirror provided with the infrared optical film of Embodiment 2 of this invention. It is a figure which shows the structure of the laser processing machine provided with the scan mirror of Embodiment 3 of this invention. It is a figure which shows the optical characteristic of the infrared optical film of Example 1 of this invention. It is a figure which shows the optical characteristic of the infrared optical film of the reference example 1. It is a figure which shows the optical characteristic of the infrared optical film of Example 2 of this invention. It is a figure which shows the optical characteristic of the infrared optical film of Example 3 of this invention. It is a figure which shows the optical characteristic of the infrared optical film of Example 4 of this invention. It is a figure which shows the optical characteristic of the infrared optical film of the reference example 2. It is a figure which shows the optical characteristic of the infrared optical film of Example 5 of this invention. It is a figure which shows the optical characteristic of the infrared optical film of Example 6 of this invention. It is a figure which shows the optical characteristic of the infrared optical film of Example 7 of this invention. It is a figure which shows the optical characteristic of the infrared optical film of the reference example 3. It is a figure which shows the optical characteristic of the infrared optical film of Example 8 of this invention. It is a figure which shows the optical characteristic of the infrared optical film of Example 9 of this invention. It is a figure which shows the measurement result of the roundness of a processing hole using the scan mirror provided with the infrared optical film of the prior art example 1. FIG. It is a figure which shows the measurement result of the roundness of a processing hole using the scan mirror provided with the infrared optical film of the prior art example 2. It is a figure which shows the measurement result of the roundness of a processing hole using the scan mirror provided with the infrared optical film of the prior art example 3. It is a figure which shows the measurement result of the roundness of a processing hole using the scan mirror provided with the infrared optical film of the reference example 1 shown in FIG. It is a figure which shows the measurement result of the roundness of a processing hole using the scan mirror provided with the infrared optical film of the reference example 2 shown in FIG. It is a figure which shows the measurement result of the roundness of a processing hole using the scan mirror provided with the infrared optical film of the reference example 3 shown in FIG. It is a figure which shows the measurement result of the roundness of a process hole using the scan mirror provided with the infrared optical film of Example 1 shown in FIG. It is a figure which shows the measurement result of the roundness of a processing hole using the scan mirror provided with the infrared optical film of Example 2 shown in FIG. It is a figure which shows the measurement result of the roundness of a processing hole using the scan mirror provided with the infrared optical film of Example 3 shown in FIG. It is a figure which shows the measurement result of the roundness of a processing hole using the scan mirror provided with the infrared optical film of Example 4 shown in FIG. It is a figure which shows the measurement result of the roundness of a processing hole using the scan mirror provided with the infrared optical film of Example 5 shown in FIG. It is a figure which shows the measurement result of the roundness of a processing hole using the scan mirror provided with the Example 6 infrared optical film shown in FIG. It is a figure which shows the measurement result of the roundness of a processing hole using the scan mirror provided with the infrared optical film of Example 7 shown in FIG. It is a figure which shows the measurement result of the roundness of a processing hole using the scan mirror provided with the infrared optical film of Example 8 shown in FIG. It is a figure which shows the measurement result of the roundness of a processing hole using the scan mirror provided with the Example 9 infrared optical film shown in FIG. It is a figure which shows the absorptance of copper with respect to an incident angle. It is a figure which shows the relationship between the phase difference in the P wave and S wave of a laser beam, and the roundness of a processing hole.

Embodiment 1 FIG.
Embodiments of the present invention will be described below. 1 is a cross-sectional view showing the configuration of an infrared optical film according to Embodiment 1 of the present invention, and FIGS. 2 and 3 are cross-sectional views and diagrams showing other configurations of the infrared optical film according to Embodiment 1 of the present invention. 4 is a diagram showing a configuration of a film forming apparatus for forming the infrared optical film shown in FIGS. FIGS. 7 to 18 show the optical characteristics of the infrared optical films of the embodiments and reference examples of the present invention. FIGS. 19 to 33 include the embodiments of the present invention, the reference examples, and the conventional infrared optical films. It is a figure which shows the measurement result of the roundness of a processing hole using the scan mirror.

1 to 3, the infrared optical film includes a substrate 1, a gold film 2 as a reflective layer that reflects the laser light formed on the substrate 1, and a first layer 3 a formed on the gold film 2 in order. The second layer 4a, the third layer 3b, the fourth layer 4b, the fifth layer 3c, the sixth layer 4c, the seventh layer 3d, and the eighth layer 4d. The gold film 2 is formed to a thickness of 0.01 to 1.0 μm.
The first layer 3a, the third layer 3b, the fifth layer 3c, and the seventh layer 3d are formed of a low refractive index layer L having a refractive index nL of 1.3 to 1.4, and the second layer 4a, The fourth layer 4b, the sixth layer 4c, and the eighth layer 4d are formed of a high refractive index layer H having a refractive index nH of 1.9 to 2.1.

And the optical film thickness of each layer is
First layer 3a 0.26λ ≦ nLd1 ≦ 0.28λ,
Second layer 4a 0.25λ ≦ nHd2 ≦ 0.26λ,
Third layer 3b 0.25λ ≦ nLd3 ≦ 0.27λ,
Fourth layer 4b 0.22λ ≦ nHd4 ≦ 0.24λ,
Fifth layer 3c 0.21λ ≦ nLd5 ≦ 0.23λ,
Sixth layer 4c 0.17λ ≦ nHd6 ≦ 0.19λ,
7th layer 3d 0.16λ ≦ nLd7 ≦ 0.18λ,
8th layer 4d 0.17λ ≦ nHd8 ≦ 0.20λ,
(Where λ = wavelength of laser light, d1 to d8 are film thicknesses of the respective layers 3a to 3d and 4a to 4d).
In the infrared optical film, the optical film thickness nd of each layer affects the optical performance. The optical film thickness of the infrared optical film is a physical quantity determined by the product of the refractive index n and the physical film thickness d of each layer.

  Further, as shown in FIG. 2, it is conceivable to form an adhesion film 5 between the gold (Au) film 2 and the first layer 3a. This is only required to improve the adhesion between the metal of the gold film 2 and the non-metal of the first layer 3a. ZrO2) is conceivable. In addition, since the materials of the low refractive index layer and the high refractive index layer are different between the layers 3a, 4a, 3b, 4b, 3c, 4d, 3d, and 4d, an adhesion layer that enhances adhesion between them is formed. Is also possible. Further, as shown in FIG. 3, it is conceivable to form a protective film 6 on the eighth layer 4d. This may be any material that can protect the eighth layer 4d, that is, the layers 3a to 3d, 4a to 4d, and improve environmental resistance. For example, yttrium oxide (Y2O3), hafnium oxide (HfO2), Zirconium oxide (ZrO2) is conceivable. Note that other materials may be used for the adhesion film 5 and the protective film 6 as long as they do not substantially affect phase control and reflectance, and a transmission material in the infrared region is preferable.

  First, as shown in FIG. 35, the inventor confirmed the relationship between the roundness of the processed hole and the phase difference of the laser beam through experiments. As can be seen from this figure, the roundness increases as the phase difference approaches 90 degrees, and shows a tendency to rapidly decrease below 60 degrees. When the phase difference is 60 degrees or more, the variation in roundness is ± 1%, and a high-quality processed hole with small individual difference can be realized. On the other hand, when the phase difference is 60 degrees or less and 30 degrees or more, the roundness varies as much as ± 4%, and the product quality is remarkably lowered. That is, it is necessary to set the lower limit value regarding the phase difference of the laser light to 60 degrees. Since the roundness is symmetric with respect to the phase difference of 90 degrees, the upper limit value of the phase difference is 120 degrees. Therefore, when the phase difference is 60 degrees or more and 120 degrees or less, 90% or more, which is a demand from the market regarding the roundness, is achieved, and the variation in roundness is within ± 1%. Further, in a laser processing machine that performs processing using a high-energy laser beam, the reflection mirror needs to have a reflectance of 99% or more in order to prevent energy loss / mirror damage. Therefore, the above-described infrared optical film in the present invention achieves both the phase difference control of laser light and the reflectance of 99% or more.

  Next, a method for forming this infrared optical film will be described. Generally, physical vapor deposition (PVD method), chemical vapor deposition (CVD), wet plating, or the like can be used. The formation method is not particularly limited. From the viewpoint of productivity, the physical vapor deposition method is preferable for forming the infrared optical film of the present invention. Among physical vapor deposition methods, a method for forming an infrared optical film by vacuum vapor deposition is shown below. FIG. 4 is a cross-sectional view showing a configuration of a vacuum evaporation apparatus as a film forming apparatus. In the vacuum deposition method, the inside of the vacuum chamber 14 is evacuated and film formation is performed at a low pressure. Energy is input to the raw material stored in the crucible 15 by the electron gun 8, and the raw material is melted and evaporated. The material then adheres to the substrate 12 attached to the upper substrate dome 13. Thus, since there is a process of evaporation → adhesion, it is called “evaporation”.

  And since the several crucible 15 can be accommodated in the rotation stage 7, various materials can be used. An optical film thickness meter 11 is used to control the film thickness of the infrared optical film. The optical film thickness meter 11 monitors the change in the film thickness on the monitor substrate 10, and when the target is reached, the shutter 9 is closed to stop the film formation. The substrate dome 13 is provided with a rotation mechanism to make the film thickness uniform. In the actual film forming process, the Au film is 5.0 ± 0.2 mm / sec, the YF3 film is 8.0 ± 0.5 mm / sec, the YbF3 film is 7.0 ± 0.5 mm / sec, and the ZnS film is 10 mm. The film was formed at a rate of 0.0 ± 0.5 cm / sec, and the degree of vacuum was maintained at 1.0 × 10 −3 Pa or less in order to prevent foreign matter / water from entering.

  The low refractive index material in the present invention is composed of yttrium fluoride (YF3), a mixture containing yttrium fluoride (YF3), ytterbium fluoride (YbF3), or a mixture containing ytterbium fluoride (YbF3). The refractive index is in the range of 1.3 to 1.4. On the other hand, the high refractive index material in the present invention is made of zinc sulfide (ZnS) or a mixture containing zinc sulfide (ZnS), and has a refractive index in the range of 2.1 to 2.3.

Examples and reference examples according to the present invention will be described below.
[Example 1]
Gold film (Au film) thickness: 500 nm
Optical thickness of the first layer 3a (YbF3): 0.264λ
Optical thickness of the second layer 4a (ZnS): 0.250λ
Optical film thickness of the third layer 3b (YbF3): 0.253λ
Optical thickness of the fourth layer 4b (ZnS): 0.223λ
Optical thickness of the fifth layer 3c (YbF3): 0.215λ
Optical thickness of the sixth layer 4c (ZnS): 0.186λ
Optical thickness of the seventh layer 3d (YbF3): 0.179λ
Optical thickness of the eighth layer 4d (ZnS): 0.177λ
(Λ = 9.28 μm: wavelength of laser light)
The YbF3 having a refractive index nL: 1.39 is used as the low refractive index layer, and ZnS having a refractive index nH: 2.20 is used as the high refractive index layer, and the infrared optical film of Example 1 is formed by vacuum deposition. Created. And the optical characteristic measured with the infrared spectrophotometer and the infrared ellipsometer is shown in FIG. As is apparent from the figure, the phase difference of the laser beam is controlled within the range of 63 degrees to 87 degrees in the range of the incident angle of 45 degrees ± 8 degrees. Further, since the reflectance is 99.0% or more, it functions as a reflection mirror in a laser processing machine for drilling using high energy laser light.

[Reference Example 1]
Gold film (Au film) thickness: 500 nm
Optical film thickness of the first layer (YbF3): 0.264λ
Optical film thickness of the second layer (ZnS): 0.250λ
Optical film thickness of the third layer (YbF3): 0.253λ
Optical thickness of the fourth layer (ZnS): 0.223λ
Optical film thickness of the fifth layer (YbF3): 0.215λ
Optical thickness of the sixth layer (ZnS): 0.165λ
Optical thickness of the seventh layer (YbF3): 0.179λ
Optical thickness of the eighth layer (ZnS): 0.177λ
(Λ = 9.28 μm: wavelength of laser light)
An infrared optical film of Reference Example 1 was prepared by vacuum evaporation using YbF3 having a refractive index of 1.39 as the low refractive index layer and ZnS having a refractive index of 2.20 as the high refractive index layer.
In Reference Example 1, the optical film thickness of the sixth layer is formed thinner than the sixth layer 4c of Example 1 shown above, and is outside the scope of the present invention. The other part is the same infrared optical film as in Example 1. And the optical characteristic measured with the infrared spectrophotometer and the infrared ellipsometer is shown in FIG. As is apparent from the figure, the phase difference of the laser beam is within the range of 33 to 60 degrees within the range of the incident angle of 45 degrees ± 8 degrees, and satisfies the target phase difference range (60 to 120 degrees). Not.

[Example 2]
Gold film (Au film) thickness: 500 nm
Optical film thickness of the first layer 3a (YbF3): 0.277λ
Optical thickness of the second layer 4a (ZnS): 0.250λ
Optical film thickness of the third layer 3b (YbF3): 0.265λ
Optical thickness of the fourth layer 4b (ZnS): 0.227λ
Optical thickness of the fifth layer 3c (YbF3): 0.210λ
Optical thickness of the sixth layer 4c (ZnS): 0.173λ
Optical thickness of the seventh layer 3d (YbF3): 0.177λ
Optical thickness of the eighth layer 4d (ZnS): 0.197λ
(Λ = 9.28 μm: wavelength of laser light)
An infrared optical film of Example 2 is formed by vacuum evaporation using YbF3 having a refractive index nL: 1.39 as a low refractive index layer and ZnS having a refractive index nH: 2.20 as a high refractive index layer. did. FIG. 9 shows optical characteristics measured by an infrared spectrophotometer and an infrared ellipsometer. As is apparent from the figure, the phase difference of the laser beam is controlled within the range of 63 degrees to 84 degrees in the range of the incident angle of 45 degrees ± 8 degrees. Further, since the reflectance is 99.0% or more, it functions as a reflection mirror in a laser processing machine for drilling using high energy laser light.

[Example 3]
Gold film (Au film) thickness: 500 nm
Optical film thickness of the first layer 3a (YbF3): 0.261λ
Optical thickness of the second layer 4a (ZnS): 0.252λ
Optical film thickness of the third layer 3b (YbF3): 0.251λ
Optical thickness of the fourth layer 4b (ZnS): 0.222λ
Optical thickness of the fifth layer 3c (YbF3): 0.214λ
Optical thickness of the sixth layer 4c (ZnS): 0.178λ
Optical thickness of the seventh layer 3d (YbF3): 0.175λ
Optical thickness of the eighth layer 4d (ZnS): 0.191λ
(Λ = 9.28 μm: wavelength of laser light)
An infrared optical film of Example 3 is formed by vacuum evaporation using YbF3 having a refractive index nL: 1.39 as a low refractive index layer and ZnS having a refractive index nH: 2.20 as a high refractive index layer. did. And the optical characteristic measured with the infrared spectrophotometer and the infrared ellipsometer is shown in FIG. As is apparent from the figure, the phase difference of the laser beam is controlled within the range of 63 to 85 degrees in the range of the incident angle of 45 degrees ± 8 degrees. Further, since the reflectance is 99.0% or more, it functions as a reflection mirror in a laser processing machine for drilling using high energy laser light.

[Example 4]
Gold film (Au film) thickness: 500 nm
Optical thickness of the first layer 3a (YbF3): 0.263λ
Optical thickness of the second layer 4a (ZnS): 0.250λ
Optical film thickness of the third layer 3b (YbF3): 0.251λ
Optical thickness of the fourth layer 4b (ZnS): 0.229λ
Optical thickness of the fifth layer 3c (YbF3): 0.226λ
Optical thickness of the sixth layer 4c (ZnS): 0.170λ
Optical thickness of the seventh layer 3d (YbF3): 0.175λ
Optical thickness of the eighth layer 4d (ZnS): 0.193λ
(Λ = 9.28 μm: wavelength of laser light)
An infrared optical film of Example 4 is formed by vacuum deposition using YbF3 having a refractive index nL: 1.39 as a low refractive index layer and ZnS having a refractive index nH: 2.20 as a high refractive index layer. did. And the optical characteristic measured with the infrared spectrophotometer and the infrared ellipsometer is shown in FIG. As is apparent from the figure, the phase difference of the laser beam is controlled within the range of 64 degrees to 86 degrees in the range of the incident angle of 45 degrees ± 8 degrees. Further, since the reflectance is 99.0% or more, it functions as a reflection mirror in a laser processing machine for drilling using high energy laser light.

[Reference Example 2]
Gold film (Au film) thickness: 500 nm
Optical film thickness of the first layer (YbF3): 0.263λ
Optical film thickness of the second layer (ZnS): 0.250λ
Optical film thickness of the third layer (YbF3): 0.282λ
Optical thickness of the fourth layer (ZnS): 0.229λ
Optical film thickness of the fifth layer (YbF3): 0.226λ
Optical thickness of the sixth layer (ZnS): 0.170λ
Optical thickness of the seventh layer (YbF3): 0.152λ
Optical thickness of the eighth layer (ZnS): 0.193λ
(Λ = 9.28 μm: wavelength of laser light)
An infrared optical film of Reference Example 2 was prepared by vacuum deposition using YbF3 having a refractive index of 1.39 as the low refractive index layer and ZnS having a refractive index of 2.20 as the high refractive index layer. In Reference Example 2, the optical thicknesses of the third layer and the seventh layer were made thicker than the third layer 3b of Example 4 shown above and thinner than the seventh layer 3d, and were outside the scope of the present invention. is there. The other part is the same infrared optical film as in Example 4. And the optical characteristic measured with the infrared spectrophotometer and the infrared ellipsometer is shown in FIG. As is apparent from the figure, the phase difference of the laser beam is within the range of 31 degrees to 55 degrees within the range of the incident angle of 45 degrees ± 8 degrees, and satisfies the target phase difference range (60 degrees to 120 degrees). Not.

[Example 5]
Gold film (Au film) thickness: 500 nm
Optical thickness of the first layer 3a (YbF3): 0.264λ
Optical thickness of the second layer 4a (ZnS): 0.259λ
Optical film thickness of the third layer 3b (YbF3): 0.251λ
Optical thickness of the fourth layer 4b (ZnS): 0.237λ
Optical thickness of the fifth layer 3c (YbF3): 0.211λ
Optical thickness of the sixth layer 4c (ZnS): 0.174λ
Optical thickness of the seventh layer 3d (YbF3): 0.177λ
Optical thickness of the eighth layer 4d (ZnS): 0.196λ
(Λ = 9.28 μm: wavelength of laser light)
An infrared optical film of Example 5 is formed by vacuum evaporation using YbF3 having a refractive index nL: 1.39 as a low refractive index layer and ZnS having a refractive index nH: 2.20 as a high refractive index layer. did. FIG. 13 shows optical characteristics measured by an infrared spectrophotometer and an infrared ellipsometer. As is apparent from the figure, the phase difference of the laser beam is controlled within the range of 63 degrees to 88 degrees in the range of the incident angle of 45 degrees ± 8 degrees. Further, since the reflectance is 99.0% or more, it functions as a reflection mirror in a laser processing machine for drilling using high energy laser light.

[Example 6]
Gold film (Au film) thickness: 500 nm
Optical film thickness of the first layer 3a (YF3): 0.265λ
Optical thickness of the second layer 4a (ZnS): 0.250λ
Optical film thickness of the third layer 3b (YF3): 0.254λ
Optical thickness of the fourth layer 4b (ZnS): 0.225λ
Optical thickness of the fifth layer 3c (YF3): 0.214λ
Optical thickness of the sixth layer 4c (ZnS): 0.181λ
Optical thickness of the seventh layer 3d (YF3): 0.177λ
Optical thickness of the eighth layer 4d (ZnS): 0.172λ
(Λ = 9.28 μm: wavelength of laser light)
An infrared optical film of Example 6 is formed by vacuum deposition using YF3 having a refractive index nL: 1.36 as a low refractive index layer and ZnS having a refractive index nH: 2.20 as a high refractive index layer. did. And the optical characteristic measured with the infrared spectrophotometer and the infrared ellipsometer is shown in FIG. As is apparent from the figure, the phase difference of the laser beam is controlled within the range of 65 degrees to 82 degrees in the range of the incident angle of 45 degrees ± 8 degrees. Further, since the reflectance is 99.1% or more, it functions as a reflection mirror in a laser processing machine for drilling using high energy laser light.

[Example 7]
Gold film (Au film) thickness: 500 nm
Optical thickness of the first layer 3a (YF3): 0.272λ
Optical thickness of the second layer 4a (ZnS): 0.259λ
Optical film thickness of the third layer 3b (YF3): 0.254λ
Optical thickness of the fourth layer 4b (ZnS): 0.226λ
Optical thickness of the fifth layer 3c (YF3): 0.214λ
Optical thickness of the sixth layer 4c (ZnS): 0.184λ
Optical thickness of the seventh layer 3d (YF3): 0.162λ
Optical thickness of the eighth layer 4d (ZnS): 0.195λ
(Λ = 9.28 μm: wavelength of laser light)
An infrared optical film of Example 7 is formed by vacuum evaporation using YF3 having a refractive index nL: 1.36 as a low refractive index layer and ZnS having a refractive index nH: 2.20 as a high refractive index layer. did. FIG. 15 shows optical characteristics measured by an infrared spectrophotometer and an infrared ellipsometer. As is apparent from the figure, the phase difference of the laser beam is controlled within the range of 65 degrees to 90 degrees in the range of the incident angle of 45 degrees ± 8 degrees. Further, since the reflectance is 99.1% or more, it functions as a reflection mirror in a laser processing machine for drilling using high energy laser light.

[Reference Example 3]
Gold film (Au film) thickness: 500 nm
Optical film thickness of the first layer (YF3): 0.251λ
Optical thickness of the second layer (ZnS): 0.259λ
Optical film thickness of the third layer (YF3): 0.254λ
Optical thickness of the fourth layer (ZnS): 0.226λ
Optical thickness of the fifth layer (YF3): 0.214λ
Optical thickness of the sixth layer (ZnS): 0.166λ
Optical thickness of the seventh layer (YF3): 0.162λ
Optical thickness of the eighth layer (ZnS): 0.195λ
(Λ = 9.28 μm: wavelength of laser light)
An infrared optical film of Reference Example 2 was prepared by vacuum evaporation using YF3 having a refractive index of 1.36 as the low refractive index layer and ZnS having a refractive index of 2.20 as the high refractive index layer. In Reference Example 3, the optical thicknesses of the first layer and the sixth layer are formed thinner than the first layer 3a and the sixth layer 4c of Example 7 described above, and are outside the scope of the present invention. The other part is the same infrared optical film as in Example 7. And the optical characteristic measured with the infrared spectrophotometer and the infrared ellipsometer is shown in FIG. As is apparent from the figure, the phase difference of the laser beam is in the range of 37 ° to 66 ° within the range of the incident angle of 45 ° ± 8 °, and satisfies the target phase difference range (60 ° to 120 °). Not.

[Example 8]
Gold film (Au film) thickness: 500 nm
Optical film thickness of the first layer 3a (YF3): 0.265λ
Optical thickness of the second layer 4a (ZnS): 0.250λ
Optical film thickness of the third layer 3b (YF3): 0.267λ
Optical thickness of the fourth layer 4b (ZnS): 0.231λ
Optical thickness of the fifth layer 3c (YF3): 0.219λ
Optical thickness of the sixth layer 4c (ZnS): 0.174λ
Optical thickness of the seventh layer 3d (YF3): 0.175λ
Optical thickness of the eighth layer 4d (ZnS): 0.191λ
(Λ = 9.28 μm: wavelength of laser light)
An infrared optical film of Example 8 is formed by vacuum deposition using YF3 having a refractive index nL: 1.36 as a low refractive index layer and ZnS having a refractive index nH: 2.20 as a high refractive index layer. did. And the optical characteristic measured with the infrared spectrophotometer and the infrared ellipsometer is shown in FIG. As is apparent from the figure, the phase difference of the laser beam is controlled within the range of 65 degrees to 100 degrees in the range of the incident angle of 45 degrees ± 8 degrees. Further, since the reflectance is 99.1% or more, it functions as a reflection mirror in a laser processing machine for drilling using high energy laser light.

[Example 9]
Gold film (Au film) thickness: 500 nm
Optical thickness of the first layer 3a (YF3): 0.261λ
Optical thickness of the second layer 4a (ZnS): 0.254λ
Optical film thickness of the third layer 3b (YF3): 0.255λ
Optical thickness of the fourth layer 4b (ZnS): 0.228λ
Optical thickness of the fifth layer 3c (YF3): 0.224λ
Optical thickness of the sixth layer 4c (ZnS): 0.178λ
Optical thickness of the seventh layer 3d (YF3): 0.165λ
Optical thickness of the eighth layer 4d (ZnS): 0.181λ
(Λ = 9.28 μm: wavelength of laser light)
An infrared optical film of Example 9 is formed by vacuum evaporation using YF3 having a refractive index nL: 1.34 as a low refractive index layer and ZnS having a refractive index nH: 2.20 as a high refractive index layer. did. And the optical characteristic measured with the infrared spectrophotometer and the infrared ellipsometer is shown in FIG. As is apparent from the figure, the phase difference of the laser beam is controlled within the range of 63 degrees to 87 degrees in the range of the incident angle of 45 degrees ± 8 degrees. Further, since the reflectance is 99.2% or more, it functions as a reflecting mirror in a laser processing machine for drilling using high energy laser light.

  Next, the performance of the infrared optical film of each example described above, the infrared optical film of each reference example, and the infrared optical film used to obtain a higher reflectance than before are compared. First, scan mirrors on which the respective infrared optical films were formed were prepared and attached to a laser processing machine for drilling, and the roundness of the processed holes was evaluated. Conventional scan mirrors formed with infrared optical films are: Conventional Example 1: Au mirror, Conventional Example 2: Reflection mirror in which a dielectric / semiconductor multilayer film is formed on an underlayer such as an Au film to increase the reflectivity (For example, Unexamined-Japanese-Patent No. 2003-302520), Conventional example 3: Circularly polarized mirror (For example, patent 2850683). 19 to 21 show the roundness of a processed hole formed by attaching a scan mirror to which the infrared optical film of Conventional Examples 1 to 3 is applied to a laser processing machine. FIG. 19 shows the evaluation of the scan mirror of Conventional Example 1, FIG. 20 shows the scan mirror of Conventional Example 2, and FIG. 21 shows the evaluation of the scan mirror of Conventional Example 3. 19 and 20, the roundness of the processed hole is as low as about 83% and does not reach 90% of the market demand. In FIG. 21, the roundness is 90% or more in part, but the roundness changes ± 4% or more according to the change in the incident angle, which indicates that the processed hole shape varies greatly.

  22 to 24 show the roundness of a processed hole formed by attaching a scan mirror to which the infrared optical film of each reference example is applied to a laser processing machine. FIG. 22 is a diagram showing an evaluation with respect to Reference Example 1 shown above, FIG. 23 is a reference example 2 shown above, and FIG. 24 is a diagram showing an evaluation with respect to Reference Example 3 shown above. In an infrared optical film having an optical film thickness outside the range of the present invention, the roundness variation is as large as ± 3% according to the change in the incident angle, and a roundness of 90% or more cannot be realized. 25 to 33 are diagrams showing the roundness of a processing hole formed by attaching the scan mirror to which the infrared optical film of the first to ninth embodiments described above is applied to a laser processing machine. Even when the scan mirror is swung within an incident angle range of 45 ± 8 degrees, the roundness of 90% or more is always realized, and the variation in roundness is within ± 1%.

  In each of the above embodiments, the low refractive index layer is formed of ytterbium fluoride (YbF3) or yttrium fluoride (YF3) having a refractive index of 1.39. However, the present invention is not limited to this. However, if it is formed of a low refractive index layer having a refractive index nL of 1.3 to 1.4, the same effects as those of the above embodiments can be obtained. That is, even if it is formed of either a mixture containing yttrium fluoride (YF3) or a mixture containing ytterbium fluoride (YbF3), it is presumed that the same effects as those of the above-described embodiments are obtained. In addition, although an example in which the high refractive index layer is formed of zinc sulfide (ZnS) having a refractive index of 2.20 has been shown, the present invention is not limited thereto, and the refractive index nH is 1.9 to 2.1. It is estimated that the same effects as those in the above embodiments can be obtained.

  According to the infrared optical film of the first embodiment configured as described above, processing is achieved by eliminating the polarization anisotropy of the laser light according to the oscillation of the scan mirror while realizing high reflectivity. Hole roundness can be achieved. In addition, this can be surely executed when the wavelength of the laser light is 9.28 μm. The low refractive index layer is made of any of yttrium fluoride (YF3), a mixture containing yttrium fluoride (YF3), ytterbium fluoride (YbF3), or a mixture containing ytterbium fluoride (YbF3). Since the high refractive index layer is formed of zinc sulfide (ZnS), the material absorption in the infrared region is small, and the phase difference of the laser light is controlled while realizing high reflectivity. By eliminating the polarization anisotropy, the processing hole can be made circular. Further, since the adhesion layer is provided between the gold film and the first layer, the adhesion between the gold film and the first layer is ensured, and the adhesion layer is made of yttrium oxide (Y2O3), cerium oxide (CeO2). By using hafnium oxide (HfO 2) and zirconium oxide (ZrO 2), it is possible to have more reliable adhesion without degradation of performance / film quality due to moisture absorption. Moreover, since the protective layer is provided on the eighth layer, each layer can be protected from the outside. Furthermore, by using a protective layer of yttrium oxide (Y 2 O 3), hafnium oxide (HfO 2), or zirconium oxide (ZrO 2), high hardness can be realized and further reliable protection can be achieved.

Embodiment 2. FIG.
FIG. 5 is a diagram showing the configuration of a scan mirror on which the infrared optical film of the present invention is formed. In the figure, the surface of the holding body 17b of the scan mirror 16 is mirror-finished, and an infrared optical film 17a is formed thereon. A rib structure is formed on the back surface of the holding body 17b to reduce weight while maintaining strength. Since the optical performance is determined by the infrared optical film 17a, the substrate material of the scan mirror 16 does not function optically. However, the substrate of the scan mirror 16 is desirably lightweight and highly rigid, and for example, boron carbide (B4C), silicon carbide (SiC), or beryllium (Be) is preferably used. However, there is no particular limitation. It is also conceivable to form an adhesion film between the holding body 17b and the infrared optical film 17a. This may be anything that improves the adhesion between the holding body 17b and the infrared optical film 17a. For example, chromium (Cr) or nickel (Ni) is preferable. The adhesion film may be formed by the same film formation method as the infrared optical film 17a.

  According to the scan mirror of the second embodiment configured as described above, since the infrared optical film of the present invention is used, polarization anisotropy can be eliminated.

Embodiment 3 FIG.
FIG. 6 is a diagram showing a configuration of a laser processing machine provided with the scan mirror of the present invention. In the figure, in the laser processing machine 29, the linearly polarized laser beam 18 emitted from the laser oscillator 28 is applied to the first polarizing means 20 through the reflection mirror 19, and is split into two laser beams 21 and 22 here. . One laser beam 21 passes through the reflection mirror 19, and the other laser beam 22 is scanned in the biaxial direction by the first galvano scanner 23 in which the scan mirror 16 is disposed, and the two laser beams 21 and 22 are scanned. Is then scanned by the second galvano scanner 25 in which the scan mirror 16 is disposed, and the workpiece 27 is irradiated and processed through the fθ lens 26. Since the first polarizing means 20 and the second polarizing means 24 use the characteristic that the laser light is linearly polarized light, it is preferable to apply the scan mirror 16 of the present invention to the second galvano scanner 25.

  According to the laser beam machine of the third embodiment configured as described above, since the scan mirror using the infrared optical film of the present invention is provided, the machining hole can be formed in a desired perfect circle. .

1 substrate, 2 gold film, 3a first layer, 3b third layer, 3c fifth layer, 3d seventh layer,
4a 2nd layer, 4b 4th layer, 4c 6th layer, 4d 8th layer, 5 adhesion layer, 6 protective layer, 16 scan mirror, 17a infrared optical film, 29 laser processing machine.

Claims (11)

A gold (Au) film formed on a substrate to a thickness of 0.01 to 1.0 μm, a low refractive index layer having a refractive index nL of 1.3 to 1.4 on the gold film, and a refractive index Infrared optical film in which n layers of 1.9 to 2.1 and high refractive index layers are alternately stacked, and each of the first to eighth layers is laminated.
The optical film thickness of each of the layers is from the gold film side to the first layer 0.26λ ≦ nLd1 ≦ 0.28λ,
The second layer 0.25λ ≦ nHd2 ≦ 0.26λ,
The third layer 0.25λ ≦ nLd3 ≦ 0.27λ,
The fourth layer 0.22λ ≦ nHd4 ≦ 0.24λ,
The fifth layer 0.21λ ≦ nLd5 ≦ 0.23λ,
The sixth layer 0.17λ ≦ nHd6 ≦ 0.19λ,
The seventh layer 0.16λ ≦ nLd7 ≦ 0.18λ,
The eighth layer 0.17λ ≦ nHd8 ≦ 0.20λ,
(Wherein λ = wavelength of laser light, d1 to d8 are film thicknesses of the respective layers). The infrared optical film according to claim 1, wherein the wavelength of the laser beam is 9.28 μm. The low refractive index layer is formed of either yttrium fluoride (YF3) or a mixture containing yttrium fluoride (YF3), ytterbium fluoride (YbF3), or a mixture containing ytterbium fluoride (YbF3). And
The infrared optical film according to claim 1, wherein the high refractive index layer is formed of zinc sulfide (ZnS). The infrared optical film according to any one of claims 1 to 3, further comprising an adhesion layer between the gold film and the first layer. 5. The adhesion layer according to claim 4, wherein the adhesion layer is formed of at least one of yttrium oxide (Y2O3), cerium oxide (CeO2), hafnium oxide (HfO2), and zirconium oxide (ZrO2). Infrared optical film. 6. The infrared optical film according to claim 1, further comprising a protective layer on the eighth layer. The infrared optical film according to claim 6, wherein the protective layer is formed of at least one of yttrium oxide (Y 2 O 3), hafnium oxide (HfO 2), and zirconium oxide (ZrO 2). 8. A scan mirror, wherein the infrared optical film according to claim 1 is disposed and formed on a holder.   The scan mirror according to claim 8, further comprising an adhesion film between the infrared optical film and the holding body.   The scan mirror according to claim 9, wherein the adhesion film is formed of at least one of chromium (Cr) and nickel (Ni). A laser processing machine comprising the scan mirror according to any one of claims 8 to 10.

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