Measuring cell and optical analysis device

Abstract

[Problem] To provide a measurement cell and an optical analysis device capable of suppressing the generation of particles due to corrosion and deterioration and improving the performance of maintaining an airtight state. [Solution] An optical cell (1) comprises: a first cell flange (7a) which includes a gas flow passage (5) through which a substance to be measured flows, and which is disposed on the incident side of light from a light source (light emitting element) (3); a second cell flange (7b) which is disposed adjacent to the first cell flange (7a) and which includes the gas flow passage (5); a light incident window portion (2a) which is joined to a portion of the first cell flange (7a) and upon which light is incident; and a light emission window portion (2b) which is joined to a portion of the second cell flange (7b) and through which light is emitted. A thin film layer (28ax, 28aY, 28aZ) comprising metal atoms is applied to a joining surface (28a) of the light incident window portion (2a) and the first cell flange (7a).

Description

Measuring cell and optical analysis device Cross Reference

[0001] This application claims priority based on Japanese Patent Application No. 2023-118525 filed in Japan on July 20, 2023, the entire contents of which are incorporated herein by reference.

[0002] The present invention relates to a measurement cell and an optical analysis device that use a light-emitting element to optically analyze the concentration of a substance to be measured in a measurement cell by absorptiometry.

[0003] Conventionally, optical analyzers of this type are known to be connected to a gas supply device and the main gas line of a semiconductor manufacturing device, and are arranged so that the substance to be measured flows into the measurement cell inline from an inlet and an outlet provided at both ends of the measurement cell constituting the optical analyzer, allowing concentration measurement (see Patent Document 1).

[0004] International Publication No. 2020 / 158506

[0005] In semiconductor manufacturing equipment, durability of used parts is desired over a long period of time, and a sealing method that can maintain corrosion resistance and airtightness of the measurement cell over a long period of time and has low particle generation is also required for the optical detector of the optical analyzer. Furthermore, since the semiconductor manufacturing process places the utmost importance on quality and production efficiency, a sealing method with high airtightness is also desired for the optical detector of the optical analyzer.

[0006] Conventionally, the cell flange and the brittle breakable light-transmitting window portion that constitute the measurement cell have been made airtight by using a sealing material such as a gasket to maintain the airtight state. However, when this sealing material is used, it is structurally difficult to maintain airtight performance over a long period of time due to the risk of damage to the brittle breakable light-transmitting window material, deformation and deterioration of the sealing material, and difficulty in managing the gap in the sealing portion.

[0007] Furthermore, if a sealing material made of synthetic resin, which is less likely to break due to the brittle fracture of the light-transmitting window portion, is used, the gas permeability of the sealing material becomes an issue, making it difficult to ensure the airtightness required for semiconductor manufacturing equipment, and there is also a risk that particles may be generated due to corrosion or deterioration.

[0008] SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a measurement cell and an optical analysis device that can suppress the generation of particles due to corrosion or deterioration and improve the ability to maintain an airtight state.

[0009] (1) In one embodiment for achieving the above object, a measurement cell has a flow path through which a substance to be measured flows, and includes a first cell flange arranged on the incident side of light from a light source (light-emitting element), a second cell flange arranged adjacent to the first cell flange and having a flow path, a cylindrical light entrance window portion joined to at least a part of the first cell flange through which light enters, and a cylindrical light exit window portion joined to at least a part of the second cell flange through which light exits, and a thin film layer made of metal atoms is applied to the joining surface between the light entrance window portion and the first cell flange. (2) Another embodiment of a measurement cell for achieving the above object is a measurement cell having a flow path through which a substance to be measured flows, the measurement cell comprising: a first cell flange arranged on the incident side of light from a light-emitting element; a second cell flange arranged adjacent to the first cell flange and having a flow path; a third cell flange arranged on the detection side of light from the light-emitting element; a cylindrical light entrance window joined to at least a portion of the first cell flange for admitting light; and a cylindrical light exit window joined to at least a portion of the third cell flange for exiting light, wherein a thin film layer composed of metal atoms is applied to the joining surface between the light entrance window and the first cell flange and the joining surface between the light exit window and the third cell flange. (3) In another embodiment of the measurement cell, a thin film layer composed of metal atoms is preferably applied to the joining surface between the light exit window and the second cell flange. (4) In another embodiment of the measurement cell, a thin film layer composed of metal atoms is preferably applied to the joining surface between the first cell flange and the second cell flange. (5) In a measurement cell according to another embodiment, it is preferable that the end face of the light entrance window on the light exit window side in the optical axis direction is flat, and a gap is formed between the end face of the light entrance window on the light entrance window side and the end face of the light exit window on the light entrance window side. (6) In a measurement cell according to another embodiment, a recess may be formed on the light exit window side of the light entrance window, and a gap may be formed between the recess and the end face of the light exit window on the light entrance window side. (7) In a measurement cell according to another embodiment, the end face of the light entrance window on the optical axis direction is flat, and a convex portion is formed on the light entrance window side of the light exit window, and a gap may be formed between the end face and the top of the convex portion.(8) In a measurement cell according to another embodiment, an end face of the light entrance window in the optical axis direction and an end face of the light exit window on the light-emitting element side may be integrally bonded to form an integrated window, and a gap may be formed within the integrated window. (9) The materials constituting the light entrance window and the light exit window are preferably sapphire glass, quartz glass, diamond glass, CaF2 glass, BaF2 glass, MgF2 glass, LiF glass, AlF3 glass, SrF2 glass, or KBr glass. Note that the material constituting the light-transmitting window is selected depending on the light absorbed by the substance to be measured, and is therefore not limited to the embodiments. (10) An optical analysis device having a measurement cell having a flow path through which a substance to be measured flows, and a transmitted light detector that detects the transmitted light in the measurement cell as light passes through a light entrance window, wherein the measurement cell has a first cell flange arranged on the incident side of light from a light-emitting element (light source), a second cell flange arranged adjacent to the first cell flange and having a flow path, a cylindrical light entrance window joined to at least a part of the first cell flange through which light enters, and a cylindrical light exit window joined to at least a part of the second cell flange through which light exits, and a thin film layer made of metal atoms is applied to the joint surface between the light entrance window and the first cell flange.

[0010] According to the present invention, it is possible to provide a measurement cell and an optical analysis device that can suppress the generation of particles due to corrosion or deterioration and improve the performance of maintaining an airtight state.

[0011] 1 is a diagram showing the overall configuration of a concentration detection system including an optical analysis device used in an embodiment of the present invention. It is an exploded perspective view showing the configuration of a measurement cell used in an embodiment of the present invention. It is a cross-sectional view taken along line A-A in FIG. 2. It is a cross-sectional view taken along line B-B in FIG. 2. It is a partially transparent view showing the configuration of a measurement cell used in an embodiment of the present invention. (a) is a diagram for explaining the structure of a measurement cell used in an embodiment, and (b) is a diagram for explaining the structure of an optical cell according to Modification 1. (a) is a cross-sectional view for explaining the structure of a measurement cell according to Modification 2, (b) is a diagram for explaining the structure of a light entrance window, and (c) is a longitudinal cross-sectional view in the optical axis direction of (b). FIG. 8 is a diagram for explaining a method of joining a first cell flange 7a and a light entrance window 2a, where (a) shows the state before joining and (b) shows the state after joining. (a) is a cross-sectional view for explaining the structure of a measurement cell according to Modification 3, (b) is a diagram for explaining the structure of a light exit window, and (c) is a longitudinal cross-sectional view in the gas flow path direction of the measurement cell. 10A is a diagram for explaining an example of joining a diaphragm to a second cell flange 7b, with the inside of the circle being an enlarged view of the joined portion, and FIG. 10B is a diagram for explaining the structure of a light incident window portion of Modification 4. FIG. 10B is a diagram for explaining an example of beam welding a first cell flange 7a to a second cell flange 57b. FIG. 10C is a diagram for explaining another example of beam welding a first cell flange 7a to a second cell flange 67b. FIG. 10D is a cross-sectional view for explaining the structure of a measurement cell according to Modification 7.

[0012] REFERENCE SIGNS LIST 1 Measurement cell 2a Light entrance window 2b, 2c Light exit window 3 Light emitting element (light source) 4 Detection unit 6 Gap 7a First cell flange 7b, 57b, 67b Second cell flange 7c Third cell flange 20 Optical analysis device 28a, 28b, 28c Joint surface

[0013] Hereinafter, embodiments of the present invention will be described with reference to the drawings. Note that the embodiments described below do not limit the inventions according to the claims. Furthermore, not all of the elements and combinations thereof described in the embodiments are necessarily essential to the solution of the present invention.

[0014] In this embodiment, FIG. 1 is a diagram showing the overall configuration of a concentration detection system including an optical analysis device 20. FIG. 2 is an exploded perspective view showing the configuration of a measurement cell 1. FIG. 3 is a cross-sectional view taken along line A-A in FIG. 2. FIG. 4 is a cross-sectional view taken along line B-B in FIG. 2. FIG. 5 is a partially transparent view showing the configuration of the measurement cell 1. FIG. 6(a) is a diagram illustrating the structure of a measurement cell used in this embodiment, partially showing an enlarged view of the joint between flanges, and FIG. 6(b) is a diagram illustrating the structure of an optical cell according to Modification 1. FIG. 7(a) is a longitudinal cross-sectional view illustrating the structure of a measurement cell according to Modification 2, FIG. 7(b) is a diagram illustrating the structure of a light entrance window, and FIG. 7(c) is a longitudinal cross-sectional view of the light entrance window in the optical axis direction. FIG. 8 is a diagram illustrating a method for joining a first cell flange 7a and a light entrance window 2a, with FIG. 8(a) showing the state before joining and FIG. 8(b) showing the state after joining. 9(a) is a cross-sectional view illustrating the structure of a measurement cell according to Modification 3, (b) is a view illustrating the structure of a light exit window, and (c) is a longitudinal cross-sectional view of the measurement cell in the gas flow path direction. FIG. 10(a) is a view illustrating an example of joining a diaphragm to a second cell flange 7b, with the circled portion showing an enlarged view of the joining portion, and (b) is a view illustrating the structure of a light entrance window according to Modification 4. FIG. 11 is a view illustrating an example of beam welding the first cell flange 7a to the second cell flange 57b. FIG. 12 is a view illustrating another example of beam welding the first cell flange 7a to the second cell flange 67b. FIG. 13 is a cross-sectional view illustrating the structure of a measurement cell according to Modification 7.

[0015] [Optical analysis device] The optical analysis device 20 is connected to a gas supply device 22 and a main gas line 23 of a semiconductor manufacturing device 21, and is arranged so that the substance to be measured (a substance flowing in the direction of the arrow in Figure 1) flows inline into the measurement cell 1 from an inlet 20a and an outlet 20b provided at both ends of the measurement cell 1 that constitutes the optical analysis device 20, allowing the concentration of the substance to be measured to be measured.

[0016] As shown in Figure 2, the optical analysis device 20 according to this embodiment comprises a measurement cell 1, a light-emitting element 3 that emits light (note that the term "light-emitting element" is a broader concept than a light source, and includes, but is not limited to, light sources such as lamps equipped with light-emitting elements that emit ultraviolet light of a predetermined wavelength and semiconductor light sources), and a detection unit 4 that detects transmitted light. Note that because this is an inline structure in which the substance to be measured flows directly, the parts that come into contact with the substance to be measured are made of a material that is resistant to corrosion (intergranular corrosion) at the contact points, such as non-magnetic austenitic stainless steel (SUS316L) or titanium, to enhance corrosion resistance.

[0017] [Measurement Cell] As shown in Figure 2, the measurement cell 1 has a first cell flange 7a, a second cell flange 7b, a light entrance window 2a, and a light exit window 2b. The first cell flange 7a and the second cell flange 7b are made of, for example, SUS316L or titanium. The light entrance window 2a and the light exit window 2b are made of, for example, sapphire glass, quartz glass, diamond glass, CaF2 glass, BaF2 glass, MgF2 glass, LiF glass, AlF3 glass, SrF2 glass, or KBr glass.

[0018] The first cell flange 7a has a through hole 37a that passes light emitted from a light-emitting element (hereinafter referred to as the "light source") 3. The through hole 37a is formed to extend in the light propagation direction (the direction of the solid arrow in FIG. 3). The second cell flange 7b is disposed adjacent to the first cell flange 7a. The second cell flange 7b has a through hole 37b that passes light that has passed through the through hole 37a, and a through hole 37c that passes gas. The through hole 37b is formed to extend in the light propagation direction, and the through hole 37c is formed to extend in the gas propagation direction (the direction of the dashed arrow in FIG. 3). The through hole 37a and the through hole 37b form an optical path (the solid arrow in FIG. 3) that passes light. The through hole 37c forms a gas flow path 5 that passes gas.

[0019] The light entrance window 2a is a cylindrical, brittle, breakable, light-transmitting window that transmits light passing through the through-hole 37a. The material of the light entrance window 2a is preferably sapphire, which has high transmittance and resistance to detection light used in concentration measurement, such as ultraviolet light, and is mechanically and chemically stable. However, other stable materials, such as quartz glass, can also be used. In addition, diamond glass, CaF2 glass, BaF2 glass, MgF2 glass, LiF glass, AlF3 glass, SrF2 glass, and KBr glass may also be used. In this specification, light includes not only ultraviolet light but also at least infrared light and visible light, and may include electromagnetic waves of any wavelength. Furthermore, translucency means that the internal transmittance of the light irradiated onto the measurement cell 1 is sufficiently high to enable concentration measurement.

[0020] 2, 5 and 6, the light incident window 2a is bonded to a part (bonding surface 28a) of the light emitting end surface 47a of the first cell flange 7a so as to cover the through hole 37a. The bonding method will be described later.

[0021] The light exit window 2b is a cylindrical, brittle, breakable, light-transmitting window that transmits light passing through the through-hole 37b. The material of the light exit window 2b is preferably sapphire, which has high transmittance and resistance to detection light used in concentration measurement, such as ultraviolet light, and is mechanically and chemically stable. However, other stable materials, such as quartz glass, can also be used. Other materials include diamond glass, CaF2 glass, BaF2 glass, MgF2 glass, LiF glass, AlF3 glass, SrF2 glass, and KBr glass. As shown in FIGS. 2, 5, and 8, the light exit window 2b is bonded to a portion (bonding surface 28b) of the light exit end surface 47b of the second cell flange 7b so as to cover the through-hole 37b. The bonding method will be described later.

[0022] As shown in FIGS. 3 to 6 , the first cell flange 7a and the second cell flange 7b are joined at a portion of the light-exiting end surface 47a of the first cell flange 7a (joint surface 28a in FIG. 6(a)) and a portion of the light-incident end surface 47c of the second cell flange 7b (joint surface 28c). As shown in FIG. 6(a) , a gap 6 exists between the light-incident window 2a and the light-exit window 2b to allow the flow of gas. This gap is appropriately designed (e.g., between 20 μm and 100 mm) by changing the thicknesses of the light-incident window 2a, the light-exit window 2b, the first cell flange 7a, and the second cell flange 7b depending on the analyte. While the light-incident window 2a and the light-exit window 2b have been described as being cylindrical, they are not limited to cylindrical shapes and may be cylindrical, for example, as long as they are capable of being joined as described below.

[0023] [Joining Method] <Joining the First Cell Flange 7a and the Light Entry Window 2a> As shown in Figure 8(b), thin film layers 38aX, 38aY, and 38aZ are formed between the joining surface 28b of the light entry window 2a and the joining surface 28a of the first cell flange 7a to form the joining portion 8a. The thin film layers 38aX, 38aY, and 38aZ are made of metal atoms (e.g., gold, silver, nickel, copper, titanium, and aluminum). The first cell flange 7a and the light entry window 2a are joined by bonding the metal atoms together using solid-state bonding, which bonds them in a solid state.

[0024] Specifically, in a vacuum, a metal underlayer (e.g., titanium, 38aX1 in FIG. 8(a)) with good adhesion and affinity is formed on the bonding surface 28b of the light incident window 2a using sputtering, made of sapphire glass or quartz glass, and then metal atoms with good affinity for the metal underlayer (e.g., gold, 38aX2 in FIG. 8(a)) are formed thereon to form a underlayer (thin film) 38aX. Similarly, a metal underlayer (38aZ in FIG. 8(b)) with good adhesion and affinity is formed on the bonding surface 28a of the SUS material or the like that constitutes the first cell flange 7a, and then metal atoms with good affinity for the metal underlayer (e.g., gold, 38aY in FIG. 8(a)) are formed thereon to form a underlayer. The light incident window 2a and the first cell flange 7a are then brought into contact. The metal atoms then diffuse and rearrange to form a single unit, completing the bonding process. By bonding the metal atoms together in this way, an intermolecular bond is formed, and the direct bonding ensures airtightness at the bonding surfaces 28a and 28b.

[0025] <Joining of second cell flange 7b and light exit window 2b> The joining of second cell flange 7b and light exit window 2b at joint 8b is similar to the joining at joint 8a described above, and therefore will not be described here. Therefore, bonding metal atoms together forms an intermolecular bond, and direct bonding ensures airtightness at the bonding surfaces 28a, 28b. Bonding metal atoms together in this way forms an intermolecular bond, and direct bonding ensures airtightness between second cell flange 7b and light exit window 2b.

[0026] <Joining the First Cell Flange 7a and the Second Cell Flange 7b> As shown in FIG. 6(a), the first cell flange 7a and the second cell flange 7b are joined by forming thin film layers 28aX, 28aY, and 28aZ between the joining surface 28a of the first cell flange 7a and the joining surface 28c of the second cell flange 7b to form a joint 8c. The thin film layers 28aX, 28aY, and 28aZ are composed of metal atoms (e.g., gold, silver, nickel, copper, titanium, and aluminum). The first cell flange 7a and the second cell flange 7b are joined by solid-state bonding, bonding the metal atoms together in a solid state. Therefore, bonding the metal atoms together forms intermolecular bonds, and the direct bonding ensures airtightness at the joining surfaces 28a and 28c. Bonding the metal atoms together in this way forms intermolecular bonds, and the direct bonding ensures airtightness between the first cell flange 7a and the second cell flange 7b. If the cell flange is made of a metal material such as SUS material, or if a hollow (doughnut-shaped) diaphragm is used instead of the first cell flange, beam welding or the like may also be used for joining. The diaphragm will be described later.

[0027] [Effects of the Present Embodiment] For example, in conventional techniques such as brazing and diffusion bonding (thermocompression bonding), which are conventional methods of joining by applying heat, a joining object is sandwiched between materials to be joined and heated to a temperature at which the materials melt. However, when cooled to room temperature, stress is generated inside the materials, and in joining materials with different linear expansion coefficients, such as glass material (sapphire glass or quartz glass) and SUS material, the expansion during heating and the contraction during cooling after joining can cause warping or cracks in the materials.

[0028] In contrast, the present embodiment provides the following advantages. (1) Because this method is room-temperature bonding, any material can be bonded as long as the surface roughness and flatness are ensured. Using a bonding area also enables bonding of dissimilar materials with different linear expansion coefficients. (2) Because adhesives, O-rings, screws, metal seals, gasket seals, etc. are not used, the number of parts can be significantly reduced. This significantly increases design freedom and allows for simpler and more compact designs. Furthermore, the use of metal atoms (gold, titanium, etc.), which are more chemically stable than adhesives or brazing materials, provides excellent corrosion resistance. Furthermore, deterioration of airtightness due to deterioration of sealing materials and corrosion associated with sealing materials can be reduced. (3) Because the structure does not use any synthetic resin sealing materials to seal the brittle, breakable light-transmitting window material, there is no loss of airtightness due to gas permeation. (4) It is possible to bond components that cannot be exposed to high temperatures, enabling a structure that does not deteriorate even in harsh environments. Furthermore, because there is no temperature change before and after bonding, no stress due to heating remains, and accurate positioning and bonding can be achieved in the atmosphere. (5) The bonded interface is integrated, eliminating voids and providing excellent airtightness. (6) There is no leaching of adhesive or O-ring components (particles, etc.), making it usable in areas where this is a problem. Furthermore, organic solvents can be used for cleaning after bonding.

[0029] [Modification 1] In the measurement cell according to Modification 1, the light entrance window 2a and the light exit window 2b are shaped as shown in FIG. 6(b) so as to form a gap 6 in the line of the gas flow path 5. Specifically, the light exit window 2b is configured by integrally molding a base portion 52 and a convex portion 53. Furthermore, a gap 6 is formed between the end face of the light entrance window 2a on the light exit window 2b side and the top of the convex portion 53 of the light exit window 2b. The joining points (8a to 8c) and joining method are the same as those in the above embodiment, and therefore a description thereof will be omitted. According to Modification 1, the line of the gap 6 and the line of the gas flow path 5 are aligned in a straight line, allowing for smooth gas outflow.

[0030] [Variation 2] The light entrance window 2a constituting the measurement cell according to Variation 2 has a generally cylindrical shape and is formed by integrally molding the body 13 and the end portions 10, 10 at both ends of the body 13, as shown in FIGS. 7(a) to 7(c). A groove (recess) 15 of a predetermined width is formed circumferentially by making the radial thickness of the body 13 smaller than the radial thickness of the end portions 10. A gap 16 for measuring absorbance is formed in the body 13. The light exit window 2b has a cylindrical shape, and the end face of the light entrance window 2a facing the detection unit 4 is joined to the end face of the light exit window 2b facing the light entrance window 2a, forming a joint 8d (see FIG. 7(a)). The joining method for the joints 8a to 8c is the same as in the above embodiment, and therefore will not be described here. The inflowing gas flows out through the groove 15 and the gap 16. According to Variation 2, the inflowing gas flows out through the groove 15 and the gap 16, resulting in smooth gas outflow. The effect of this modification 2 is that the gap can be easily controlled and dimensional accuracy is improved because the window portion is integrally formed.

[0031] [Variation 3] As shown in Figures 9(a) to 9(c), the measurement cell according to Variation 3 does not have a light entrance window, but instead has a hollow (donut-shaped) diaphragm 18 bonded to the light exit window 2b. Light from the light source passes through the hollow portion of the diaphragm 18 and reaches the detection unit. As shown in Figure 9(b), this light exit window 2b is integrally molded with a base portion 62 and a protrusion 63. The radial thickness of the protrusion 63 is smaller than the radial thickness of the base portion 62, providing a path for gas to flow circumferentially. A gap 26 for measuring absorbance is formed in the protrusion 63. The end face of the base portion 62 facing the light source 3 is bonded to the second cell flange 7b, forming a joint 8b. The diaphragm 18 is bonded to the end face of the protrusion 63 facing the light source 3, forming a thin film layer 38a2 (joint: see Figure 9(c)). This joining method replaces the cell flange, which is the joining target of the joining method for the joining portion 8a described above, with a diaphragm. The joining method is similar to that for the joining portion 8a, and therefore will not be described here. Note that this variation 3 does not include the first cell flange 7a that appears in the above-described embodiment. The inflowing gas flows out along the circumferential direction of the convex portion 63. According to variation 3, the inflowing gas flows out along the circumferential direction of the convex portion 63, resulting in smooth gas outflow. Reference numeral 26 denotes a gap for measuring absorbance. Furthermore, since the diaphragm 18 replaces the first cell flange of the above-described embodiment, the thickness of the measurement cell in the light source direction is reduced, resulting in a more compact design. For convenience, variation 3 has been described as having no light entrance window and the light exit window 2b functioning as a window. However, this light exit window 2b functions as an integrated window, with the light entrance window and light exit window of the above-described embodiment being integrally formed. The effect of variation 3 is that the integrated formation of the window facilitates gap management and improves dimensional accuracy.

[0032] [Variation 4] As shown in FIGS. 10(a) and 10(b), the measurement cell according to Variation 4 does not have a light exit window, but instead has a hollow (donut-shaped) diaphragm 19 bonded to the light entrance window 2a. Light from the light source passes through the hollow portion of the diaphragm 19 and reaches the detection unit side. As shown in FIG. 10(a), the light entrance window 2a is formed by integrally molding a base portion 72 and a protrusion 73. The radial thickness of the protrusion 73 is made smaller than the radial thickness of the base portion 72, forming a path for gas to flow in the circumferential direction. A gap 76 is formed in the protrusion 73 to allow gas to pass through. As shown in FIG. 10(b), the end face of the base portion 72 facing the detection unit 4 is bonded to the second cell flange 7b, forming a bonding portion 8f. The diaphragm 19 is bonded to the second cell flange 7b to form a thin film layer (bonding portion: see FIG. 8(a)) 38a. These bonding methods are similar to those described above, and therefore will not be described here. Note that this fourth modification does not include the first cell flange 7a that appears in the above-described embodiment. The inflowing gas flows out along the circumferential direction of the convex portion 73 and through the gap 76. According to the fourth modification, the inflowing gas flows out along the circumferential direction of the convex portion 73 and through the gap 76, resulting in smooth gas outflow. Reference numeral 76 denotes a gap for measuring absorbance. Furthermore, since the diaphragm 19 replaces the first cell flange of the above-described embodiment, the thickness of the measurement cell in the light source direction is reduced, resulting in a more compact design. Regarding the fourth modification, for convenience, it has been described that the light entrance window 2a functions as a window without a light exit window. However, this light entrance window 2a functions as an integrated window, with the light entrance window and light exit window of the above-described embodiment being integrally formed. The effect of this fourth modification is that the integrated formation of the window facilitates gap management and improves dimensional accuracy.

[0033] [Variation 5] The measurement cell according to Variation 5 is the same as Variation 1 except for the joining method between the first cell flange 7a and the second cell flange 57b (corresponding to symbol 7b in Variation 1) and the structure (shape) of the second cell flange 57b. Therefore, the same reference numerals are used for similar parts, and a description of similar points will be omitted. As shown in FIG. 11 , the second cell flange 57b has a step portion 57c along the circumferential direction on the first cell flange 7a side, and the outer periphery of the first cell flange 7a is beam-welded to the step portion 57c of the second cell flange 57b. Therefore, the joining of the lower surface of the first cell flange 7a and the upper surface of the second cell flange 57b (joining at joint 8c in FIG. 6(a)) as in Variation 1 can be omitted, thereby reducing manufacturing costs. The above-described beam joining may be performed while maintaining the joined state between the lower surface of the first cell flange 7a and the upper surface of the second cell flange 57b (joining at joint 8c in FIG. 6(a)). In this case, the joints 8c and 8d are double-jointed, so that a stronger joint is realized.

[0034] [Variation 6] The measurement cell according to Variation 6 is the same as Variation 2 except for the joining method between the first cell flange 7a and the second cell flange 67b (corresponding to symbol 7b in Variation 2) and the structure (shape) of the second cell flange 67b. Therefore, the same reference numerals are used for similar parts, and a description of similar points will be omitted. As shown in FIG. 12, the second cell flange 67b has a step portion 67c along the circumferential direction on the first cell flange 7a side, and the outer periphery of the first cell flange 7a is beam-welded to the step portion 67c of the second cell flange 67b. Therefore, the joining of the lower surface of the first cell flange 7a and the upper surface of the second cell flange 67b (joining at joint 8c in FIG. 7(a)) as in Variation 1 can be omitted, thereby reducing manufacturing costs. Note that the beam joining described above may be performed while maintaining the joined state between the lower surface of the first cell flange 7a and the upper surface of the second cell flange 67b (joining at joint 8c in FIG. 7(a)). In this case, the joints 8c and 8d are double-jointed, achieving a stronger bond. The shapes of the first and second cell flanges in the above-described Modifications 5 and 6 are not limited to those shown in FIGS. 11 and 12 , as long as they have an area that can be joined to each other. [Modification 7] The measurement cell according to Modification 7 is identical to Modification 1 except for the provision of a third cell flange 7c having the same shape as the first cell flange 7a and a light exit window 2c having the same shape as the light entrance window 2a, and the elimination of the light exit window 2b. Therefore, the same reference numerals are used for similar parts, and a description of similar points will be omitted. As shown in FIG. 13, the measurement cell according to Modification 7 has a first cell flange 7a, a second cell flange 7b, a third cell flange 7c, a light entrance window 2a, and a light exit window 2c. The first cell flange 7a has a through-hole 37a that allows light emitted from a light-emitting element (hereinafter referred to as a "light source") 3 to pass through. The second cell flange 7b is disposed adjacent to the first cell flange 7a. The second cell flange 7b has a through-hole 37b (see FIG. 3) for passing light that has passed through the through-hole 37a, and a through-hole 37c (see FIG. 3) for passing gas. The third cell flange 7c has a through-hole (reference number omitted) for passing light that has passed through the through-hole 37b.As shown in Figures 2, 5, and 6, the light entrance window 2a is bonded to a portion (bonding surface 28a) of the light exit end surface 47a of the first cell flange 7a so as to cover the through-hole 37a. The light exit window 2c is a cylindrical light exit window that allows light passing through the through-hole 37b to pass and transmits light passing through the through-hole formed in the third cell flange 7c. The light exit window 2c is bonded at bonding points 8e and 8f. The bonding method for bonding points 8e and 8f is the same as the bonding method for bonding points 8a and 8c, so a description thereof will be omitted. According to Variation 7, the second cell flange 7b is disposed between the first cell flange 7a and the third cell flange 7c, thereby more firmly fixing the second cell flange 7b. As shown in Figures 11 and 12, the first cell flange and the second cell flange, and the third cell flange and the second cell flange may be beam-bonded.

Claims

1. A measurement cell having a flow path through which a substance to be measured flows, comprising: a first cell flange arranged on the incident side of light from a light-emitting element; a second cell flange arranged adjacent to the first cell flange and having the flow path; a cylindrical light entrance window portion joined to at least a part of the first cell flange through which the light enters; and a cylindrical light exit window portion joined to at least a part of the second cell flange through which the light exits, wherein a thin film layer made of metal atoms is applied to the joining surface between the light entrance window portion and the first cell flange.

2. A measurement cell having a flow path through which a substance to be measured flows, comprising a first cell flange arranged on the incident side of light from a light-emitting element, a second cell flange arranged adjacent to the first cell flange and having the flow path, a third cell flange arranged on the detection side of light from the light-emitting element, a cylindrical light entrance window portion joined to at least a part of the first cell flange through which the light is incident, and a cylindrical light exit window portion joined to at least a part of the third cell flange through which the light exits, wherein a thin film layer consisting of metal atoms is applied to the joint surface between the light entrance window portion and the first cell flange and the joint surface between the light exit window portion and the third cell flange.

3. The measuring cell according to claim 1, characterized in that a thin film layer made of metal atoms is applied to the joint surface between the light exit window portion and the second cell flange.

4. A measuring cell as described in claim 1 or 3, characterized in that a thin film layer made of metal atoms is applied to the joining surfaces of the first cell flange and the second cell flange.

5. The measurement cell described in claim 1, characterized in that the end face of the light entrance window portion in the optical axis direction facing the light exit window portion is flat, and a gap is formed between the end face of the light entrance window portion in the optical axis direction and the end face of the light exit window portion on the light entrance window portion side.

6. The measurement cell as described in claim 1, characterized in that a recess is formed on the light entrance window side of the light exit window, and a gap is formed between the recess and the end face of the light exit window on the light entrance window side.

7. The measurement cell described in claim 1, characterized in that the end face of the light entrance window portion in the optical axis direction facing the light exit window portion is flat, a convex portion is formed on the light entrance window portion side of the light exit window portion, and a gap is formed between the optical axis end face and the top of the convex portion.

8. The measurement cell according to claim 1, characterized in that an integral window portion is formed by integrally forming an end face in the optical axis direction of the light entrance window portion and an end face of the light exit window portion on the light emitting element side by bonding, and a gap is formed within the integral window portion.

9. The measuring cell according to claim 1, characterized in that the light entrance window and the light exit window are made of a material selected from the group consisting of sapphire glass, quartz glass, diamond glass, CaF2 glass, BaF2 glass, MgF2 glass, LiF glass, AlF3 glass, SrF2 glass and KBr glass.

10. An optical analysis device comprising the measurement cell according to claim 1 or 2, and a transmitted light detector for detecting the transmitted light in the measurement cell when the light passes through the light entrance window.

Images