Metal Mirror for Fourier Transform Infrared Spectrometer for Hazardous Gas Analysis

Abstract

The objective of the present invention is to provide a metal mirror capable of improving the detection precision and reliability of a Fourier transform infrared spectrometer, a gas cell equipped with said metal mirror, and a Fourier transform infrared spectrometer equipped with said gas cell. The present invention provides a Fourier transform infrared spectrometer capable of precisely detecting gas by increasing the frequency of contact between the gas sample and infrared rays, by forming a Cr-Al-Si-N-Au composite coating layer as a Cr-based hybrid coating film on a metal mirror surface mounted on a gas cell according to the above purpose, thereby minimizing light loss, and accordingly, allowing the beam within the gas cell to reciprocate 17 times between the lower mirror and the upper mirror by the metal mirror, so that the total optical path reaches 20m.

Description

Technology Field

[0001] The present invention relates to a metal mirror for a Fourier transform infrared spectrometer for analyzing harmful gases, and more specifically, to an Au-coated metal mirror provided in a gas cell of a Fourier transform infrared spectrometer for analyzing harmful gases. Background Technology

[0002] A Fourier transform infrared spectrometer is a spectrometer capable of detecting even very small amounts of sample by applying Fourier transform equations to spectral analysis using a Michelson interferometer. Fourier transform infrared spectrometers are also used for the analysis of hazardous gases; they are configured such that a reflective mirror is mounted on a gas cell capable of filling a sample, allowing infrared radiation to be reflected multiple times to detect the sample. By repeatedly reflecting the infrared radiation to lengthen its path, the sample molecules contained in the gas cell can be sufficiently detected by the infrared radiation, thereby enabling high-sensitivity results. Registered Patent No. 10-1677038 proposes a variable mirror to extend the optical path in order to improve the sensitivity of the infrared spectrometer; however, this presents a problem in that precise measurements require a stable mirror position, and controlling the position of the variable mirror is difficult. Furthermore, while a longer optical path can improve the measurement reliability of the spectrometer regarding the sample, the repeated reflection by the mirror leads to the problem of infrared light loss caused by the mirror.

[0003] Furthermore, in the case of Au coating films formed on metal mirrors, corrosion occurs due to reflected light energy and harmful gases. Cracks formed on the surface of the metal mirror due to corrosion cause errors in the optical path of the Fourier transform infrared spectrometer, requiring replacement and shortening the lifespan. The problem to be solved

[0004] Therefore, the objective of the present invention is to provide a high-quality metal mirror that is durable and capable of improving the detection precision and reliability of a Fourier transform infrared spectrometer, a gas cell equipped with said metal mirror, and a Fourier transform infrared spectrometer equipped with said gas cell. means of solving the problem

[0005] In accordance with the above objective, the present invention minimizes light loss by coating Au on a metal mirror surface mounted in a gas cell, and to improve the adhesion of the coating layer, a Cr / CrN buffer layer is formed on the metal mirror substrate, and a Cr-Al-Si-N-Au composite coating layer is formed as a Cr-based hybrid coating film on the buffer layer.

[0006] That is, the present invention is,

[0007] As a mirror arranged in the gas cell of a Fourier transform infrared spectrometer,

[0008] The present invention provides a metal mirror for a gas cell of an infrared spectrometer characterized by including a Cr-Al-Si-N-Au composite coating material on the metal mirror surface.

[0009] In the above, the metal mirror for a gas cell of an infrared spectrometer is provided, characterized in that the coating material formed on the metal mirror surface comprises a multilayer coating material in which a buffer layer containing Cr and CrN is formed between the metal mirror substrate surface and the Cr-Al-Si-N-Au composite coating material, wherein a gradient buffer layer with a gradually changing content of the N component is formed.

[0010] In the above, the metal mirror for a gas cell of an infrared spectrometer is characterized in that the coating material formed on the metal mirror surface is a multilayer coating material formed with a thickness of 4.5 to 5.5 μm, including a buffer layer and a Cr-Al-Si-N-Au composite coating material.

[0011] In the above, a metal mirror for a gas cell of an infrared spectrometer is provided, characterized in that when a crack occurs in a multilayer coating material and propagates, the crack propagates along the side where the coating material is formed without crossing the thickness direction of the multilayer coating material, thereby maintaining the quality of the upper surface of the multilayer coating material.

[0012] In addition, the present invention,

[0013] A method for manufacturing a metal mirror coating material for a gas cell of the above-mentioned infrared spectrometer,

[0014] Place the metal mirror substrate into the vacuum chamber,

[0015] Using a Cr target, an inert gas including Ar and nitrogen (N2) are flowed in a vacuum chamber to form a buffer layer of Cr and CrN composites by physical vapor deposition (PVD), and

[0016] The present invention provides a method for manufacturing a metal mirror coating material for a gas cell of an infrared spectrometer, characterized by forming a multilayer coating material by forming a Cr-Al-Si-N-Au composite coating layer on a buffer layer by physical vapor deposition (PVD) using a CrAlSi alloy target and an Au target, and flowing an inert gas containing Ar and nitrogen (N2).

[0017] In the above, a method for manufacturing a metal mirror coating material for a gas cell of an infrared spectrometer is provided, characterized in that the composition ratio of each constituent element in the CrAlSi alloy target is 25 to 35 at% Al, 5 to 15 at% Si, and the remainder is Cr.

[0018] In the above, the method for manufacturing a metal mirror coating material for a gas cell of an infrared spectrometer is characterized by forming the buffer layer by physical vapor deposition (PVD) using a Cr target and flowing an inert gas including Ar and nitrogen (N2) in a vacuum chamber, and initially proceeding with the process without nitrogen to form a Cr layer, and then gradually increasing the amount of nitrogen supplied to create a gradient in which the N component of the CrN layer increases, thereby forming a gradient in the composition of the buffer layer.

[0019] In the above, in the Cr-Al-Si-N-Au composite coating layer, a DC pulse is applied to each target, and the applied power is 0.45 to 0.55 kW, and

[0020] The present invention provides a method for manufacturing a metal mirror coating material for a gas cell of an infrared spectrometer, characterized by supplying an inert gas supplied into a vacuum chamber at a flow rate of 27 to 33 sccm and nitrogen at a flow rate of 27 to 33 sccm.

[0021] In the above, a method for manufacturing a metal mirror coating material for a gas cell of an infrared spectrometer is provided, characterized in that the temperature of the base material or the deposition process temperature is 270 to 330℃.

[0022] In addition, the present invention,

[0023] A gas cell of a Fourier transform infrared spectrometer is provided, comprising a metal mirror for the gas cell of the above-described infrared spectrometer.

[0024] The above coating layer is formed by the following process.

[0025] That is, in the CrAlSi alloy target, the composition ratio of each constituent element in atomic percent is 25–35 at% Al, 5–15 at% Si, and the remainder is Cr. Au is prepared as a separate target.

[0026] A DC pulse is applied to each target, and the applied power is 0.45 to 0.55 kW.

[0027] The distance between the target and the base material in the vacuum chamber is 8 to 12 cm.

[0028] The base pressure inside the vacuum chamber is 4.5 × 10⁻⁶ -3 Up to 5.5×10 -3 It is Pa.

[0029] The inert gas (Ar) supplied into the vacuum chamber is supplied at a flow rate of 27 to 33 sccm, and nitrogen is supplied at a flow rate of 27 to 33 sccm.

[0030] The operating pressure inside the vacuum chamber is 4.5×10⁻⁶ -1 Up to 5.5×10 -1 It is Pa.

[0031] The temperature of the base material to the deposition process temperature is 270 to 330℃.

[0032] The base material is rotated at 9 to 11 rpm during the process.

[0033] A Fourier transform infrared spectrometer is provided that can precisely detect gas by increasing the frequency of contact between the gas sample and infrared rays through a metal mirror fabricated by forming a coating layer as described above, causing the beam within the gas cell to reciprocate 17 times between the lower mirror and the upper mirror, thereby extending the total optical path to 20m.

[0034] In the above, the upper mirrors placed within the gas cell are arranged as a pair on the left and right, and the lower mirror consists of a single unit.

[0035] In the above, the upper mirror is made of a curved mirror having a predetermined radius of curvature, and the two mirrors on the left and right are arranged symmetrically so that the entire set of the two mirrors forms a single curved surface.

[0036] In the above, the lower mirror is composed of a curved mirror having the same radius of curvature as the upper mirror, and the lengths of the opposing sides are different, with one side being longer.

[0037] In the above, the area enclosed by the longer side of the lower mirror has 9 light reflection points, the area enclosed by the shorter side of the lower mirror has 8 light reflection points, and each of the upper mirrors has 1 light reflection point.

[0038] The present invention is,

[0039] In the gas cell of a Fourier transform infrared spectrometer,

[0040] A first upper mirror and a second upper mirror arranged at the top of the gas cell; and

[0041] A composite mirror arranged at the bottom of the gas cell opposite to the first upper mirror and the second upper mirror; comprising

[0042] The present invention provides a gas cell of a Fourier transform infrared spectrometer characterized in that the first upper mirror, the second upper mirror, and the lower mirror surfaces are formed with a coating layer as an infrared reflective coating.

[0043] In the above, the gas cell of a Fourier transform infrared spectrometer is provided, characterized in that the first upper mirror, the second upper mirror, and the lower mirror are made of Al material.

[0044] In the above, the gas cell of a Fourier transform infrared spectrometer is provided, characterized in that the first upper mirror and the second upper mirror each include one light reflection point, the lower mirror includes 17 light reflection points, 9 points are located in a longer horizontal side region, and 8 points are located in a shorter horizontal side region.

[0045] In the above, the reflection points of the lower mirror are arranged in nearly a straight line with 9 points along the long side and in nearly a straight line with 8 points along the short side, and the light forms a path by alternately moving the reflection points of the lower mirror toward the 9-point side and the 8-point side. A gas cell of a Fourier transform infrared spectrometer is provided.

[0046] In the above, a gas cell of a Fourier transform infrared spectrometer is provided, characterized in that the first upper mirror, the second upper mirror, and the lower mirror have mirror surfaces of curved surfaces having the same radius of curvature. Effects of the invention

[0047] In the case of the CrAlSiN-Au coating of the present invention, the crack size is much smaller than that of conventional Au coating films, and since high energy is required for crack propagation, the waves forming the crack do not pass across the coating film but propagate sideways along the coating film, thereby not compromising the quality of the metal mirror surface.

[0048] The Cr-Al-Si-N-Au composite coating layer of the present invention functions as a self-adaptive coating layer to prevent corrosion of the coating layer by harmful gases.

[0049] The Cr / CrN buffer layer having a gradient according to the present invention strengthens the bonding strength between the substrate and the Cr-Al-Si-N-Au composite coating layer.

[0050] In addition, by fabricating a Gold Metal mirror using a buffer layer and CrAlSiN-Au multi-coating, the adhesion and rigidity of the coating layer are increased, resulting in improved durability and an extended service life.

[0051] According to the present invention, whenever reflected by a mirror, the infrared reflective Au coating reflects with high reflectivity without light loss, so a long path of 17 round trips can be created within the gas cell, and accordingly, the substance can be detected with high reliability.

[0052] The above optical path is designed to pass through almost the entire internal space of the gas cell, so that even minute amounts of sample can be accurately detected. Brief explanation of the drawing

[0053] Figure 1 is a schematic diagram showing the configuration of a Fourier transform infrared spectrometer. Figure 2 is a schematic diagram showing the gas cell of a Fourier transform infrared spectrometer and the metal mirrors installed in the gas cell. Figure 3 is a diagram showing the reflection point and part of the light reflection path for the lower mirror among the metal mirrors. Figure 4 is a photograph showing an Au coating applied to a metal mirror according to the present invention. Figure 5 is a table showing the result of summing the light paths according to the present invention. Figure 6 is a table showing the detection limit concentration according to the light path. Figure 7 schematically shows the structure of the buffer layer and the Cr-Al-Si-N-Au composite coating layer. FIG. 8 shows a cross-section of a conventional Au coating layer and a cross-section of a multilayer coating formed with a Cr / CrN buffer layer and a Cr-Al-Si-N-Au composite coating layer according to an embodiment of the present invention. Figure 9 shows the electrochemical analysis test and results of the multilayer coating of the present embodiment compared with conventional Au coating and no coating. Figure 10 shows a photograph of a metal mirror with a multilayer coating according to the present embodiment. FIG. 11 is a table summarizing the multilayer coating manufacturing process according to the present embodiment. Specific details for implementing the invention

[0054] Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the attached drawings.

[0055] Figure 1 is a schematic diagram showing the configuration of a Fourier transform infrared spectrometer (10).

[0056] It includes a Michelson interferometer and a gas cell capable of filling with a detection sample gas. The gas cell is formed with a material inlet and outlet, and metal mirrors are placed inside to reflect light multiple times. Light from the Michelson interferometer enters the gas cell and travels back and forth multiple times; as the light path changes due to molecules within the cell, even minute substances can be detected. As the light travels back and forth more times, the optical path becomes longer, increasing the probability of collision with the material inside the gas cell, thereby achieving high sensitivity and reliability. Accordingly, the structure of the metal mirrors is controlled to maximize the optical path, and to this end, simulations are performed based on the shape and placement of the metal mirrors.

[0057] Figure 2 is a schematic diagram showing the gas cell of a Fourier transform infrared spectrometer and the metal mirrors installed in the gas cell.

[0058] As described above, to maximize the optical path in a given gas cell, the metal mirror configured by simulation consists of two upper mirrors (200, 210) arranged left and right at the top and one lower mirror (100). The upper mirrors (200, 210) are curved mirrors having a predetermined radius of curvature, and the two mirrors are arranged in a structure where they form a single curved surface. That is, when the first upper mirror (200) and the second upper mirror (210) are arranged left and right, the mirror surfaces of the first upper mirror and the second upper mirror are configured to have the same radius of curvature as a whole.

[0059] The lower mirror (100) is configured to have the same radius of curvature as the two upper mirrors. The area of ​​the lower mirror (100) is larger than that of each of the upper mirrors, and in particular, the opposing horizontal sides (relatively longer sides) are configured to have different lengths. This configuration is related to the path of light.

[0060] Two upper mirrors and one lower mirror arranged within the gas cell have the same radius of curvature, and connecting the three entire mirror surfaces forms a single sphere.

[0061] FIG. 3 is a drawing showing a reflection point and part of the light reflection path for the lower mirror (100) among the metal mirrors.

[0062] The path of light in the gas cell is configured to repeatedly travel back and forth between the upper mirror and the lower mirror. To achieve this, the mirrors are given curved surfaces, and the lengths of the horizontal sides of the lower mirrors are varied. For each upper mirror, the reflection points of the light converge at a single point, while for the lower mirrors, as shown in Fig. 3, there are 9 reflection points along the long horizontal side and 8 reflection points along the short horizontal side. The light path is formed by repeated reflections, such as light traveling to the first upper mirror, reflecting from the reflection point of the first upper mirror, descending to strike point 1 of the lower mirror, reflecting again to strike the reflection point of the second upper mirror, descending to strike point 2 of the lower mirror, reflecting again to ascend to strike the reflection point of the first upper mirror, and descending. In other words, the reflection points of the lower mirrors are arranged almost in a straight line with 9 points along the long horizontal side and 8 points along the short horizontal side, and the light forms a path by alternately moving between the reflection points of the lower mirrors, either towards the 9-point side or the 8-point side. The sample is detected by moving approximately 20m, or more precisely 20.14m, through a total of 17 up-and-down round-trip paths. As such, infrared rays undergo multiple reflections, and light loss occurs due to the reflective surface. When reflected from a metal mirror surface, light loss occurs as some of the light is absorbed by the mirror surface and converted into heat. Therefore, the present invention applies an infrared reflective coating to the mirror surface to reduce light loss.

[0063] In the above, the upper and lower positions of the upper mirror and lower mirror included in the gas cell can be arranged in a reversed manner.

[0064] Figure 4 is a photograph showing an Au coating applied to a metal mirror according to the present invention.

[0065] The lower and upper mirrors use Al as the base material, and are coated with Au using the PVD method to reflect infrared rays almost perfectly.

[0066] The Au coating layer is formed to be 100 to 300 nm, preferably 150 to 250 nm, and the formation method can be carried out by a widely known method.

[0067] It is desirable to form a substrate layer and a buffer layer so that the Au coating layer can adhere to the Al mirror surface with excellent surface roughness. The present invention forms Cu on the Al mirror surface to a thickness of 30 to 70 nm, forms TiN on top of it to a thickness of 50 to 150 nm, and then forms an Au layer on top of it to strengthen adhesion and improve surface roughness. The Cu layer strengthens adhesion, and the TiN layer improves both adhesion and surface roughness.

[0068] The surface roughness of the mirror surface is closely related to light path control, so it is primarily controlled by polishing the Al mirror surface, and the fine surface roughness is improved by forming a base layer and a buffer layer, and the reflectivity of infrared rays is increased by coating an Au layer.

[0069] Due to this Au coating on the mirror surface, there is almost no light loss on the mirror surface even when multiple reflections occur, allowing for the accurate detection of even minute amounts of sample inside the gas cell.

[0070] Figure 5 is a table showing the result of summing the light paths according to the present invention.

[0071] Although the actual length of the gas cell is less than 1m, the total optical path reaches 20m due to 17 points of reflection, and since the optical path passes through most of the space of the gas cell, even minute amounts of material can be detected.

[0072] Figure 6 is a table showing the detection limit concentration according to the light path.

[0073] According to the present invention, a sample at the 0.1 ppm level can be detected.

[0075] Meanwhile, as a modified embodiment of the present invention, the lower mirror substrate surface can be configured by combining a plurality of pieces to form a single mirror surface, thereby allowing the light path to be reflected more frequently. In this case, in addition to the reflection points of the lower mirror being arranged in a single line with 9 points and 8 points respectively, another line of reflection points can be arranged in the middle of the two lines. This enables more dense sample detection in the gas cell space. The lower mirror surface has a shape in which a plurality of pieces are connected as planar pieces having different inclined surfaces, that is, normals at different angles, so that light can be reflected at a desired angle.

[0077] In addition, to provide a durable, high-quality metal mirror, a coating material with improved performance compared to the aforementioned coating material can be formed.

[0078] That is, a Cr / CrN buffer layer is formed on a metal mirror substrate, and a Cr-Al-Si-N-Au composite coating layer is formed as a Cr-based hybrid coating film on the buffer layer to provide a metal mirror that can be used for a long period of time.

[0079] The buffer layer is composed of Cr / CrN, which strengthens the bonding strength between the substrate and the Cr-Al-Si-N-Au composite coating layer, and has a gradient in which the N composition gradually increases toward the top layer. The buffer layer is formed by physical vapor deposition (PVD) using a Cr target in a vacuum chamber by flowing an inert gas such as Ar and nitrogen (N2). Initially, the process is carried out without nitrogen to form the Cr layer, and then the amount of nitrogen supplied is gradually increased to create a gradient in the composition of the buffer layer, thereby increasing the N component of the CrN layer. It is desirable to clean the surface of the metal mirror substrate with plasma before forming the buffer layer. Plasma cleaning can be performed by forming a plasma using an inert gas.

[0080] After forming a buffer layer, a Cr-Al-Si-N-Au composite coating layer is formed to form a multilayer coating.

[0081] The above Cr-Al-Si-N-Au composite coating layer is formed by physical vapor deposition (PVD) using a CrAlSi alloy target and an Au target, and by flowing an inert gas such as Ar and nitrogen (N2).

[0082] The above coating layer is formed by the following process (see FIG. 11).

[0083] That is, in the CrAlSi alloy target, the composition ratio of each constituent element in atomic percent is 25–35 at% Al, 5–15 at% Si, and the remainder is Cr.

[0084] A metal mirror base material is placed inside a vacuum chamber, and the alloy target and the Au target are installed at appropriate positions, respectively.

[0085] The distance between the alloy target, the Au target, and the base material inside the vacuum chamber is set to 8 to 12 cm. The base pressure inside the vacuum chamber is 4.5 × 10⁻⁶. -3 Up to 5.5×10 -3 Do it as Pa.

[0086] DC pulses are applied to the alloy target and the Au target, and the applied power is set to 0.45 to 0.55 kW.

[0087] The flow rate of the inert gas (Ar) supplied into the vacuum chamber is 27 to 33 sccm, and the flow rate of the nitrogen is 27 to 33 sccm. The operating pressure inside the vacuum chamber is 4.5 × 10⁻⁶. -1 Up to 5.5×10 -1 It is Pa.

[0088] The temperature of the base material to the deposition process temperature is set to 270 to 330℃.

[0089] In addition, the base material is rotated at 9 to 11 rpm during the process. That is, the base material is fixed to a rotating jig and rotated to improve the deposition rate.

[0090] The Cr-Al-Si-N-Au composite coating layer formed on the above buffer layer functions as a self-adaptive coating layer, preventing corrosion of the coating layer by harmful gases.

[0091] The coating layer is formed with a thickness of 4.5 to 5.5 μm, including a buffer layer.

[0092] Fig. 8 shows a cross-section of a conventional Au coating layer and a cross-section of a multilayer coating formed with a Cr / CrN buffer layer and a Cr-Al-Si-N-Au composite coating layer of an embodiment of the present invention.

[0093] In the case of the Au coating film formed on the metal mirror, it is shown that many cracks exist in the left and right indentation edge or bottom portions. While the area around the indentation bottom portion exhibits a shape where cracks propagate from the substrate toward the surface, the indentation edge portion appears to show cracks propagating from the surface toward the substrate. Additionally, it can be confirmed that all cracks pass across the coating film. That is, in the bottom portion, cracks are formed in a direction penetrating the thickness of the coating layer, but the crack width is larger toward the substrate and thinner toward the surface, showing a shape where cracks propagate from the substrate toward the surface. In contrast, in the edge portion, the width of the cracks formed in a direction penetrating the thickness of the coating layer is larger toward the surface and thins as it goes toward the substrate, showing a shape where cracks originating from the surface propagate toward the substrate.

[0094] In contrast, in the multilayer coating formed with a Cr / CrN buffer layer and a Cr-Al-Si-N-Au composite coating layer according to the present embodiment, it can be confirmed that the crack size is smaller, and since high energy is required for crack propagation, it can be confirmed that the crack does not pass across the coating film as if penetrating it, but rather propagates sideways along the coating layer (indicated in red). That is, the crack propagates along a direction parallel to the mirror surface, and does not propagate in a direction perpendicular to the mirror surface.

[0095] Therefore, the surface of the coating layer is almost free of cracks, allowing it to become a metal mirror with excellent surface quality. In this regard, the top coating layer of the multilayer coating of this embodiment functions as a self-adaptive coating.

[0096] As described above, the Cr / CrN buffer layer having a gradient in nitrogen composition strengthens the bonding force between the substrate and the Cr-Al-Si-N-Au composite coating layer, thereby providing durability to the multilayer coating and consequently extending the lifespan of the metal mirror.

[0097] Figure 9 shows the electrochemical analysis test and results of the multilayer coating of the present embodiment compared with a conventional Au coating and no coating. It can be confirmed that the multilayer coating according to the present embodiment exhibits much more stable electrochemical corrosion resistance.

[0098] Figure 10 shows a photograph of a metal mirror with a multilayer coating according to the present embodiment.

[0101] Unless otherwise defined in the foregoing, all technical and scientific terms used in this specification have the same meaning as commonly understood by a skilled expert in the technical field to which the present invention pertains. Furthermore, terms defined in commonly used dictionaries are, unless explicitly and specifically defined otherwise, more

[0102] It shall not be interpreted as either excessive or overly. Wherever any part of the specification states that it "includes" a certain component, unless specifically stated otherwise, this means that it does not exclude other components but may include additional components. Additionally, the singular form may include the plural form depending on the context.

[0103] In addition, in this specification, "on top of, on top of, or above" means being located above or below the object part, and does not necessarily mean being located on the upper side with respect to the direction of gravity. In the same context, "inside" includes cases where there is another part in between, in addition to cases where the object is directly placed inside the object.

[0104] In addition, in this specification, the term "between" includes not only cases where objects are in contact with or spaced apart from each other, but also cases where there is another object or part in between.

[0105] Additionally, in this specification, terms such as "first, second" may be used to describe various components, but said components are not limited by said terms, and said terms are used only for the purpose of distinguishing one component from another.

[0107] The rights of the present invention are not limited to the embodiments described above but are defined by what is stated in the claims, and it is obvious that a person skilled in the art can make various modifications and productions within the scope of the rights stated in the claims. Explanation of the symbols

[0111] 10: Fourier Trans Infrared Spectrometer 100: Lower mirror 200, 210: Upper mirror

Claims

Claim 1 A metal mirror for a gas cell of an infrared spectrometer arranged in a gas cell of a Fourier transform infrared spectrometer, comprising a buffer layer containing Cr and CrN on a metal mirror surface and a multilayer coating material including a Cr-Al-Si-N-Au composite coating material on the buffer layer, wherein the buffer layer is a gradient buffer layer in which the content of the N component gradually changes, and when a crack occurs in the multilayer coating material and propagates, the propagation of the crack does not cross the thickness direction of the multilayer coating material but propagates along the side of the multilayer coating material, thereby maintaining the quality of the upper surface of the multilayer coating material. Claim 2 delete Claim 3 A metal mirror for a gas cell of an infrared spectrometer according to claim 1, characterized in that the coating material formed on the metal mirror surface is a multilayer coating material formed with a thickness of 4.5 to 5.5 μm, including a buffer layer and a Cr-Al-Si-N-Au composite coating material. Claim 4 delete Claim 5 A method for manufacturing a metal mirror coating material for a gas cell of an infrared spectrometer according to either claim 1 or 3, wherein a metal mirror substrate is placed in a vacuum chamber, an inert gas containing Ar and nitrogen (N2) is flowed through the vacuum chamber using a Cr target to form a composite buffer layer of Cr and CrN by physical vapor deposition (PVD), and a Cr-Al-Si-N-Au composite coating layer is formed on the buffer layer by physical vapor deposition (PVD) using a CrAlSi alloy target and an Au target to flow an inert gas containing Ar and nitrogen (N2). Claim 6 A method for manufacturing a metal mirror coating material for a gas cell of an infrared spectrometer, characterized in that, in claim 5, the composition ratio of each constituent element in the CrAlSi alloy target is 25-35 at% Al, 5-15 at% Si, and the remainder is Cr. Claim 7 A method for manufacturing a metal mirror coating material for a gas cell of an infrared spectrometer according to claim 5, wherein in forming the buffer layer, an inert gas including Ar and nitrogen (N2) are flowed in a vacuum chamber using a Cr target to form the buffer layer by physical vapor deposition (PVD), and initially the process is carried out without nitrogen to form a Cr layer, and then the amount of nitrogen supplied is gradually increased to provide a gradient in which the N component of the CrN layer increases, thereby forming a gradient in the composition of the buffer layer. Claim 8 A method for manufacturing a metal mirror coating material for a gas cell of an infrared spectrometer, characterized in that, in the Cr-Al-Si-N-Au composite coating layer, a DC pulse is applied to each target and the applied power is 0.45 to 0.55 kW, and the inert gas supplied into the vacuum chamber is supplied at a flow rate of 27 to 33 sccm and nitrogen at a flow rate of 27 to 33 sccm. Claim 9 A method for manufacturing a metal mirror coating material for a gas cell of an infrared spectrometer, characterized in that, in claim 5, the temperature of the base material or the deposition process temperature is 270 to 330℃. Claim 10 A gas cell of a Fourier transform infrared spectrometer comprising a metal mirror for the gas cell of the infrared spectrometer of either paragraph 1 or 3.

Images