Friction test analysis device, friction test analysis method and base material for friction test

Abstract

To provide a friction test analysis device, a friction test analysis method and base material for friction test, each enabling adsorption behavior of a compound included in liquid to be analyzed under frictional environment with high sensitivity.SOLUTION: A friction test analysis device 10 comprises base material 1 for analysis, analytical equipment 2 and friction test equipment 3 and analyzes a compound included in liquid, the base material for analysis is comprised of ATR crystal and metal and includes a plane in a part, a plurality of recesses is disposed in the plane, and the metal is embedded in the recess. The analytical equipment is equipment for analyzing a compound adsorbed on a surface of the metal, that the base material for analysis includes, according to an ATR-SEIRAS method (Attenuated Total Reflection-Surface Enhanced Infrared Absorption Spectroscopy). The friction test equipment includes a test piece 3a and a driving jig 3b which rotationally drives the test piece. The driving jig rotationally drives the test piece while pressurizing it in contact with the plane of the base material for analysis including the recesses.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a friction test analysis device, a friction test analysis method, and a substrate for friction test analysis. [Background technology]

[0002] Analysis of friction between materials has been widely conducted in the past, and analysis of friction between metals contributes to the development of lubricating oil compositions. Various additives are added to lubricating oil compositions, and the lubricating performance of the lubricating oil composition depends on the behavior of adsorption and desorption of the additives on metal surfaces. Therefore, when considering what kind of additives should be used to meet the required performance of the lubricating oil composition, it is extremely important to understand the behavior of adsorption and desorption of the additives on metal surfaces.

[0003] For example, Patent Document 1 describes an analysis method that employs the ATR-SEIRAS (Attenuated Total Reflection-Surface Enhanced Inflated Absorption Spectroscopy) method to enable detailed observation of the adsorption and desorption behavior of an adsorptive compound contained in a liquid on a metal surface. Patent Document 2 describes a total reflection absorption spectrum measuring device that can be configured compactly and reliably visually observes the contact state of a sample in the total reflection measurement method (ATR method) employed in the surface analysis of polymer films, semiconductors, etc., and in the analysis of samples that significantly absorb infrared light, such as aqueous solutions. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2012-177657 A [Patent Document 2] JP 2017-181049 A Summary of the Invention [Problem to be solved by the invention]

[0005] Meanwhile, with the development of industry, the required performance regarding friction of materials is becoming more stringent day by day, and therefore there is a demand for more sensitive analysis that is more in line with actual usage conditions regarding the behavior of compounds contained in liquids, for example, the behavior of various additives used in the above-mentioned lubricating oil composition. In the case of a lubricating oil composition, since it is used to lubricate a friction surface where metals come into contact with each other, it is necessary to understand the behavior of the compounds in the lubricating oil composition, i.e., the additives, on the friction surface. However, the analysis method described in Patent Document 1 does not involve a friction test, so it is not possible to observe the behavior on the friction surface. In addition, the measurement device described in Patent Document 2 is not capable of performing a friction test, so it is not possible to observe the behavior on the friction surface. Therefore, these analysis methods and measurement devices cannot grasp the behavior of the lubricating oil composition, and further the behavior of the additives used in the lubricating oil composition, under an environment that corresponds to the actual use. Therefore, when actually used, there is a concern that problems such as damage to equipment may occur due to behavior different from the results of analysis using these analysis methods and measurement devices. Furthermore, the measurement device described in Patent Document 2 cannot perform measurements by surface-enhanced infrared spectroscopy, and therefore is unable to handle more sensitive analyses.

[0006] The present invention has been made in consideration of the above circumstances, and has an object to provide a friction test analysis device, a friction test analysis method, and a substrate for friction test analysis, which are capable of analyzing the adsorption behavior of a compound contained in a liquid under a friction environment with high sensitivity. [Means for solving the problem]

[0007] The present inventors have conducted intensive research in view of the above problems and have found that the problems can be solved by the following invention. That is, the present invention provides a friction test analysis device, a friction test analysis method, and a friction test analysis substrate having the following configurations.

[0008] 1. An analytical device for analyzing compounds contained in a liquid, comprising an analytical substrate, an analytical instrument, and a friction test instrument, the analytical substrate is made of an ATR crystal and a metal, has a flat surface on a part thereof, a plurality of recesses are arranged on the flat surface, and the metal is embedded in the recesses; the analytical instrument is an instrument for analyzing the compound adsorbed on the surface of the metal of the analytical substrate by an ATR-SEIRAS method (attenuated total reflection-surface enhanced infrared spectroscopy); The friction tester includes a test piece and a drive jig that rotates the test piece, the driving jig rotates and drives the test piece while pressing the test piece against the flat surface having the recess of the analytical substrate. Friction test analysis equipment. 2. An analytical method for analyzing a compound contained in a liquid, comprising: The compound adsorbed on the metal surface is analyzed by ATR-SEIRAS (attenuated total reflection-surface enhanced infrared spectroscopy) while conducting a friction test. Friction test analysis method. 3. A friction test analysis substrate comprising an ATR crystal and a metal, having a flat surface on one side, a plurality of recesses arranged on said flat surface, and said metal embedded in said recesses. Effect of the Invention

[0009] According to the present invention, it is possible to provide a friction test analysis device, a friction test analysis method, and a substrate for friction test analysis, which are capable of analyzing with high sensitivity the adsorption behavior of a compound contained in a liquid under a friction environment. [Brief description of the drawings]

[0010] [Figure 1] FIG. 2 is a schematic diagram of a friction test analysis device according to the present embodiment. [Diagram 2] FIG. 2 is a schematic diagram of an analytical substrate for explaining the configuration of the analytical substrate and the shape of a recess. [Diagram 3] FIG. 2 is a schematic diagram for explaining the arrangement of recesses in an analytical substrate. [Figure 4] 1 is an SEM image of the surface of an analytical substrate used in the examples. [Diagram 5] 1 is an absorption spectrum measured in Example 1. [Figure 6] 1 is an absorption spectrum measured in Comparative Example 2. [Figure 7] FIG. 2 is a plot of the difference between the area of ​​the absorption spectrum measured in Example 1 and the area of ​​the absorption spectrum measured in Comparative Example 2. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] Hereinafter, an embodiment of the present invention (hereinafter, sometimes referred to as "the present embodiment") will be described. In this specification, the upper and lower limit values ​​of the numerical ranges of "greater than or equal to", "less than or equal to", and "to" are values ​​that can be combined arbitrarily, and the numerical values ​​of the examples can also be used as the upper and lower limit values. Furthermore, provisions that are considered to be preferable can be adopted arbitrarily. In other words, one provision that is considered to be preferable can be adopted in combination with one or more other provisions that are considered to be preferable. It can be said that a combination of preferable things is more preferable.

[0012] [Friction test and analysis equipment] The friction test analysis device of this embodiment is An analytical device for analyzing a compound contained in a liquid, the analytical device comprising an analytical substrate, an analytical instrument, and a friction test instrument, the analytical substrate is made of an ATR crystal and a metal, has a flat surface on a part thereof, a plurality of recesses are arranged on the flat surface, and the metal is embedded in the recesses; the analytical instrument is an instrument for analyzing the compound adsorbed on the surface of the metal of the analytical substrate by an ATR-SEIRAS method (attenuated total reflection-surface enhanced infrared spectroscopy); The friction tester includes a test piece and a drive jig that rotates the test piece, the driving jig rotates and drives the test piece while pressing the test piece against the flat surface having the recess of the analytical substrate. That is it.

[0013] The friction test analysis device of this embodiment employs a friction test device equipped with a test piece and a drive jig for rotating the test piece, so that the compounds contained in the lubricating oil composition, i.e., additives, can be provided under a friction environment that corresponds to the actual usage situation, and therefore the behavior of the compounds under the usage environment can be accurately understood.

[0014] The friction test analysis device of this embodiment employs an instrument for analysis by the ATR-SEIRAS method (total reflection absorption-surface enhanced infrared spectroscopy). Here, the ATR method (total reflection absorption method) utilizes the phenomenon that when infrared light is totally reflected at the contact surface when the compound to be measured and the ATR crystal of the analytical substrate come into contact, the light is absorbed and reflected near the surface of the measurement object, and is a method for measuring the absorption spectrum of the measurement object from the totally reflected light. In addition, SEIRAS (surface enhanced infrared absorption spectroscopy) is a method for enhancing the infrared absorption intensity of the measurement object molecules adsorbed on a metal thin film made of metals such as gold, silver, copper, platinum, iron, and nickel to about 100 times the normal intensity. The ATR-SEIRAS method (attenuated total reflection absorption-surface-enhanced infrared spectroscopy) employed in the friction test analysis device of this embodiment applies the SEIRAS (surface-enhanced infrared absorption spectroscopy) technique to the ATR method (attenuated total reflection absorption method), making it possible to observe in detail the adsorption behavior of compounds contained in a liquid on a metal surface, which could not be grasped by the conventional attenuated total reflection absorption method (ATR method) alone, and to perform analysis with high sensitivity.

[0015] In the friction test analysis device of this embodiment, the ATR-SEIRAS method (attenuated total reflection-surface enhanced infrared spectroscopy) is adopted, and the adsorption behavior on the metal surface can be observed in detail and analyzed with high sensitivity, more specifically, due to the following phenomenon. In the friction test analysis device of this embodiment, the compound to be measured can be present on the friction surface between the test piece and the metal surface embedded in the recess of the flat surface of the analytical substrate that rotates and presses the test piece to cause friction. This enhances the infrared absorption intensity of the measurement object adsorbed on the metal surface present in the vicinity of the friction surface, and the absorption spectrum of the infrared light totally reflected via the ATR crystal that forms the analytical substrate can be measured. Here, since the infrared absorption intensity is enhanced, it becomes possible to perform analysis with high sensitivity.

[0016] The friction test analysis device of this embodiment will be described in detail with reference to a schematic diagram. Fig. 1 is a schematic diagram of the friction test analysis device of this embodiment. The friction test analysis device 10 shown in Fig. 1 includes an analytical substrate 1, an analytical instrument 2, and a friction test instrument 3. It is shown that the analytical substrate 1 is composed of an ATR crystal 1a and a metal 1b, has a flat surface on which a plurality of recesses are arranged, and the metal 1b is embedded in the recesses, and the analytical device 2 is capable of focusing infrared light on the friction surface of the analytical substrate 1 in contact with a test piece 3a of a friction test device 3, and measuring the absorption spectrum of the total reflected light from the friction surface. The friction test device 3 is also shown to include a test piece 3a and a driving jig 3b, and also includes a pressing jig, which is omitted in Fig. 1, for pressing the test piece 3a so as to come into contact with the flat surface of the analytical substrate 1 on which the metal 1b is embedded.

[0017] [Base material for analysis] The analytical substrate will be described with reference to FIG. Fig. 2 is a schematic diagram for explaining the configuration of the analytical substrate and the shape of the recesses. The analytical substrate used in the device of this embodiment is typically configured as shown in Fig. 2, that is, composed of an ATR crystal 1a and a metal 1b, in which the ATR crystal 1a has a flat surface on one side, a plurality of recesses are arranged on the flat surface, and the metal 1b is embedded in the recesses.

[0018] (ATR crystal) Examples of ATR crystals constituting the analytical substrate include crystals of silicon (Si), germanium (Ge), diamond, sapphire, fused quartz, calcium fluoride, barium fluoride, magnesium fluoride, zinc selenide, etc., among which silicon (Si) is preferred. This is because it is easy to form multiple recesses on the plane of the ATR crystal and to embed metal in the recesses, making it easy to fabricate the analytical substrate. In addition, it is inexpensive.

[0019] (metal) Preferred examples of metals constituting the analytical substrate include gold, silver, copper, platinum, iron, nickel, etc., and gold is particularly preferred. By using these metals, infrared light can be collected more easily, and compounds are easily adsorbed on the surfaces of these metals, allowing for more stable and highly sensitive analysis.

[0020] (Regarding the shape of the recess) The analytical substrate must have a plurality of recesses on its flat surface, otherwise it will be difficult to bring the metal part of the analytical substrate into contact with the test piece, making it difficult to analyze compounds adsorbed on the metal surface, and it will also be difficult to collect infrared light, making it difficult to perform a stable analysis.

[0021] The shape of the recesses in the plane of the analytical substrate is not particularly limited as long as it allows the metal to be embedded therein, and examples of shapes in a plan view include triangles (equilateral triangles, isosceles triangles, right-angled triangles, etc.), quadrangles (squares, rectangles, trapezoids, etc.), polygons such as pentagons and hexagons, ellipses, circles, etc. Taking into consideration the ease of forming the recesses, triangles, quadrangles, ellipses, and circles are preferred, equilateral triangles, squares, and circles are more preferred, and squares and circles are even more preferred. Examples of the cross-sectional shape of the recess include quadrilaterals such as squares, rectangles, and trapezoids, triangles such as isosceles and equilateral triangles, and shapes similar to these, for example, U-shapes, etc. Among these, squares and rectangles are preferred, that is, the recesses are preferably prisms and cylinders as described below.

[0022] For example, even if an attempt is made to form a recess having a quadrangular prism shape (the recess has a quadrangular shape in plan view and cross-sectional view), a curve will result when a straight portion is machined due to factors such as manufacturing accuracy, and as a result, the recess has a quadrangular shape in plan view that is close to a circle or ellipse with the corners of the rectangle rounded off, and the cross-sectional shape may have a quadrangular shape that is close to a U-shape with the corners of the rectangle rounded off, resulting in a shape that is close to a truncated square pyramid with the corners of the quadrangular prism rounded off. In this specification, except for cases where the cross-sectional shape of the recess is intentionally U-shaped, when the result is a U-shape due to manufacturing accuracy, etc., it will be treated as a quadrangle, that is, the shape of the recess will be treated as a quadrangular prism.

[0023] In the device of this embodiment, the shapes of the recesses may all be the same, or a combination of a plurality of types may be used. In consideration of more stable and highly sensitive analysis of the compounds adsorbed on the metal surface, ease of forming the recesses, etc., it is preferable that the shapes of the recesses are all the same.

[0024] The shape of the recess may be a prism, a truncated pyramid, a pyramid, etc. when the shape in plan view is polygonal, but considering particularly the more stable and highly sensitive analysis of the compound adsorbed on the metal surface, it is preferable that the bottom surface of the recess has a flat surface, and it is preferably a prism (triangular prism, square prism, hexagonal prism, etc.) or a truncated pyramid (triangular pyramid, square pyramid, hexagonal pyramid, etc.), and more preferably a prism (triangular prism, square prism, hexagonal prism, etc.). In the case of a prism, the shape in cross section of the recess is a quadrangle such as a square or a rectangle, in the case of a truncated pyramid, it is a trapezoid, and in the case of a pyramid, it is a triangle such as an isosceles triangle.

[0025] In addition, in the case of an ellipse or circle, the shape may be a cylinder (elliptical cylinder, cylinder), a truncated cone (elliptical cone, circular truncated cone), a cone (elliptical cone, circular cone), etc., but as in the case of a polygon, a cylinder (elliptical cylinder, cylinder) and a truncated cone (elliptical cone, circular truncated cone) are preferred, and a cylinder (elliptical cylinder, cylinder) is more preferred. The handling of the shape of the recess when manufacturing accuracy and the like are taken into consideration is as explained above with respect to the shapes of the recess in plan view and cross section.

[0026] The multiple recesses on the plane of the analytical substrate may be arranged irregularly or in a pattern; however, taking into consideration the ease of forming the recesses and the ease of performing a more stable and highly sensitive analysis, it is preferable that they are arranged in a pattern. From the same viewpoint, it is preferable that the plurality of recesses are arranged at equal intervals in a pattern.

[0027] The arrangement of a plurality of recesses on the plane of an analytical substrate will be described with reference to Fig. 3. Fig. 3 shows an example of the arrangement of a plurality of recesses on the plane of an analytical substrate. Figures (3-1a) to (3-1c) show the arrangement when the shape of the recesses is a rectangle in plan view. For example, as shown in Figures (3-1a), (3-1c) and (3-2a), a pattern in which a square or rectangular lattice is formed when the center points of the recesses are connected, and a pattern in which an equilateral triangular lattice is formed when the center points of the recesses are connected, as shown in Figures (3-1b) and (3-2b), are representatively preferred. In addition, although not shown in Figure 3, a pattern in which an isosceles triangle or a hexagonal lattice is formed when the center points of the recesses are connected (for example, in Figure 3-1b, the hexagonal lattice corresponds to the case where the second and fourth recesses from the left in the second row from the top are missing). ) and the like are also preferred. As shown in Figure (3-1c), the distance w1' between the vertical recesses and the distance w1'' between the horizontal recesses may be different, or may be the same as in Figures (3-1a) and (3-1b).

[0028] The width (w1) of the recess is not necessarily specified because it varies depending on the scale of the device, the size of the analytical substrate and the test piece, but is usually 0.1 μm or more, preferably 0.15 μm or more, more preferably 0.20 μm or more, and the upper limit is preferably 1.5 μm or less, more preferably 1.3 μm or less, and even more preferably 1.1 μm or less. Within the above range, recesses are easily formed, and more stable and highly sensitive analysis can be performed.

[0029] The depth (d) of the recesses cannot be generally stated because it can vary depending on the scale of the device, the size of the analytical substrate and the test piece, but is usually 0.01 μm or more, preferably 0.02 μm or more, more preferably 0.04 μm or more, and the upper limit is preferably 0.2 μm or less, more preferably 0.1 μm or less, and even more preferably 0.08 μm or less. As mentioned above, the upper and lower limits of these numerical ranges can be arbitrarily combined, and typical examples include combinations of 0.01 μm or more and 0.2 μm or less, 0.02 μm or more and 0.1 μm or less, and 0.04 μm or more and 0.08 μm or less. Within the above range, recesses are easily formed, and more stable and highly sensitive analysis can be performed.

[0030] The aspect ratio of the recess (width (w1) / depth (d)) is preferably 1.0 or more, more preferably 1.1 or more, and even more preferably 1.2 or more, with the upper limit being preferably 8.0 or less, more preferably 7.0 or less, and even more preferably 5.5 or less. As mentioned above, the upper and lower limits of these numerical ranges can be combined arbitrarily, and typical examples include combinations of 1.0 or more and 8.0 or less, 1.1 or more and 7.0 or less, and 1.2 or more and 5.5 or less. Within the above ranges, recesses are easy to form, and more stable and highly sensitive analysis can be performed.

[0031] In addition, the distance (w2) between adjacent recesses is not necessarily specified because it may vary depending on the scale of the device, the size of the analytical substrate and the test piece, etc., but is 0.005 μm or more, preferably 0.01 μm or more, more preferably 0.10 μm or more, and even more preferably 0.15 μm or more, and the upper limit is preferably 1.0 μm or less, more preferably 0.90 μm or less, and even more preferably 0.80 μm or less. As mentioned above, the upper and lower limits of these numerical ranges can be arbitrarily combined, and typical examples include combinations of 0.01 μm or more and 1.0 μm or less, 0.10 μm or more and 0.90 μm or less, and 0.15 μm or more and 0.80 μm or less. Within the above range, recesses are easily formed, and more stable and highly sensitive analysis can be performed.

[0032] The shape and dimensions of the recesses, and the distance between adjacent recesses may be the same or different, but are preferably the same from the viewpoint of performing a more stable and highly sensitive analysis. From the same viewpoint, when the dimensions of the recesses and the distance between adjacent recesses are different, it is preferable that the dimensions of the recesses and the distance between adjacent recesses are all within the above-mentioned numerical ranges. The distance between adjacent recesses may vary depending on the shape of the recesses, and in this specification, the distance between the closest points is defined as the distance between adjacent recesses.

[0033] In view of the above, it is preferable that the multiple recesses on the plane of the analytical substrate used in the device of this embodiment are arranged in a pattern, and that the shape of the recesses is rectangular, and in particular, it is preferable that the recesses having a rectangular shape are arranged in a lattice pattern.

[0034] (About the shape of the metal) The shape of the metal in plan view is the same as the shape of the recesses, since the metal is embedded in the recesses arranged on the plane of the ATR crystal. The thickness of the metal embedded in the recess is preferably 5 nm or more, more preferably 8 nm or more, and even more preferably 10 nm or more, with the upper limit being preferably 100 nm or less, more preferably 50 nm or less, even more preferably 30 nm or less, and even more preferably 15 nm or less. As mentioned above, the upper and lower limits of these numerical ranges can be arbitrarily combined, and typical examples include combinations of 5 nm or more and 100 nm or less, 8 nm or more and 50 nm or less, 10 nm or more and 30 nm or less, and 10 nm or more and 15 nm or less. When the thickness of the metal is within the above range, it becomes easier to collect infrared light, and the compound adsorbed on the surface of the metal can be analyzed more stably and with high sensitivity. In addition, it becomes easier to form the metal so as to be embedded in the recess.

[0035] (Shape of analytical substrate) The shape of the analytical substrate, i.e., the shape of the ATR crystal used to constitute the analytical substrate, is not particularly limited as long as it has a flat surface on which a plurality of recesses can be formed at least partially, and examples thereof include a plate shape, a hemisphere, a semicylinder, a triangular prism, a square prism, and various pyramid truncations such as a triangular pyramid truncation, a square pyramid truncation, and a circular cone truncation. Among these, the plate shape and the hemisphere shape are preferred. Since it is easy to collect infrared light on the friction surface and to measure the absorption spectrum of the total reflected light, it is easy to perform a highly sensitive analysis and is easy to handle.

[0036] The size of the analytical substrate cannot be generalized because it can vary depending on the scale of the device, the size of the test piece, etc., but for example, in the case of a plate shape, the length and width are preferably 5 mm or more, more preferably 10 mm or more, and even more preferably 15 mm or more, and the upper limit is preferably 50 mm or less, more preferably 40 mm or less, and even more preferably 30 mm or less. As mentioned above, the upper and lower limits of these numerical ranges can be arbitrarily combined, and typical examples include combinations of 5 mm or more and 50 mm or less, 10 mm or more and 40 mm or less, and 15 mm or more and 30 mm or less. It is easy to form recesses, and more stable and highly sensitive analysis can be performed, and it is easy to handle. From the same viewpoint, the thickness is preferably 0.5 mm or more, more preferably 1 mm or more, and even more preferably 2 mm or more, with the upper limit being preferably 20 mm or less, more preferably 15 mm or less, even more preferably 10 mm or less, and even more preferably 5 mm or less. As mentioned above, the upper and lower limits of these numerical ranges can be arbitrarily combined, and typical examples include combinations of 0.5 mm or more and 20 mm or less, 1 mm or more and 15 mm or less, 2 mm or more and 10 mm or less, and 2 mm or more and 5 mm or less.

[0037] When the analytical substrate is hemispherical, the diameter is preferably within the range of values ​​explained above for the length and width of the plate shape. Furthermore, when the analytical substrate is a semi-cylinder, the vertical and horizontal lengths of the rectangular base are preferably within the numerical range described above for the thickness of the plate shape, and the vertical length is preferably within the numerical range described above for the vertical and horizontal lengths of the plate shape.

[0038] (Manufacturing analytical substrates) The analytical substrate can be produced, for example, through a recess forming step of forming a plurality of recesses on the plane of the ATR crystal, and a metal embedding step of embedding a metal in the plurality of recesses. An example of this will be described in more detail below.

[0039] The recess forming step can be carried out, for example, by the following method. The formation of the multiple recesses is carried out by preparing an ATR crystal having a flat surface, coating the surface with a resist composition containing an ionizing radiation curable resin or the like, exposing the surface to ionizing radiation such as ultraviolet light, X-rays, or electron beams to form a resist film having the desired pattern (negative type), and developing the resist film with a resist-soluble developer to form the desired resist pattern (negative type). Next, etching is performed to a desired depth by a method such as dry etching using plasma gas to form multiple recesses on the flat surface of the ATR crystal, and the resist film is removed using sulfuric acid, hydrogen peroxide, or the like, thereby forming multiple recesses on the flat surface of the ATR crystal.

[0040] Next, the metal embedding step can be carried out, for example, by the following method. The metal is the one described above, and a thin metal film is formed on the plane of the ATR crystal on which the above-mentioned multiple recesses are formed by a chemical plating method (wet method) such as electroless plating; a method (cyclic method) such as sputtering, vacuum deposition, ion plating, or CVD; among these, electroless plating and vacuum deposition are preferable. Note that a thin metal film is also formed on the regions (protrusions) other than the recesses on the plane of the ATR crystal, but the thin metal film formed in these regions may be left as it is or may be removed. In either case, the analysis results are not affected.

[0041] [Analytical equipment] The analytical instrument used in the apparatus of this embodiment is an instrument that analyzes the compounds adsorbed on the metal surface of the above-mentioned analytical substrate by ATR-SEIRAS (attenuated total reflection-surface enhanced infrared spectroscopy).

[0042] As shown in Figure 1, the analytical instrument has a function of focusing infrared light on the friction surface of the analytical substrate that contacts the test piece of the friction test instrument and measuring the absorption spectrum of the total reflected light from the friction surface. This makes it possible to analyze compounds adsorbed on the metal surface of the analytical substrate by ATR-SEIRAS (attenuated total reflection-surface enhanced infrared spectroscopy).

[0043] [Friction testing equipment] The apparatus of this embodiment includes a friction testing instrument. The friction testing device is an instrument equipped with a test piece and a driving jig for rotating the test piece, and the driving jig is a jig that can rotate the test piece while pressing it against a flat surface having a recess of an analytical substrate so that the test piece is in contact with the flat surface.

[0044] (Test piece) The test piece is rotated while being pressed against a flat surface having a recess of the analytical substrate, thereby generating friction between the test piece and the metal surface embedded in the recess of the flat surface. A liquid containing the subject of analysis is supplied to the friction surface between the test piece and the metal surface, and a compound contained in the liquid is present, so that the compound is adsorbed onto the metal surface under frictional conditions. By enhancing the infrared absorption intensity and measuring the absorption spectrum of infrared light, highly sensitive analysis is possible.

[0045] The test piece can be used without any particular limitation as long as it generates friction with the flat surface of the analytical substrate, and its shape is preferably a disk shape, a cylinder shape, a sphere shape, an elliptical sphere shape, etc. Among these, a cylinder shape, a sphere shape, and an elliptical sphere shape are preferred, and a sphere shape is particularly preferred. This is because the friction state on the friction surface is likely to be stable, and the compound adsorbed on the surface of the metal can be analyzed more stably and with high sensitivity.

[0046] The size of the test piece cannot be generalized because it varies depending on the scale of the device, the size of the analytical substrate, etc., but the diameter is preferably 1 mm or more, more preferably 3 mm or more, and even more preferably 5 mm or more, and the upper limit is preferably 50 mm or less, more preferably 40 mm or less, and even more preferably 30 mm or less. This is because the friction state on the friction surface is likely to be stable, and the compound adsorbed on the surface of the metal can be analyzed more stably and with high sensitivity.

[0047] The material of the test piece can be any material that generates friction with the flat surface of the analytical base material, and generally, any material with excellent wear resistance can be used, such as high carbon chromium steel such as SUJ2; stainless steel such as SUS304, SUS304L, SUS316, and SUS316L; and other materials such as Hastelloy, Incoloy, Inconel, and two-phase alloys.

[0048] (Drive jig) The driving jig may be a jig that can rotate and press the test piece at the same time, or may be a jig that has a mechanism for rotating and a separate mechanism for pressing.

[0049] The rotation speed of the rotary drive is not particularly limited as long as the test piece is rotated and friction is generated between the metal surface embedded in the recess of the flat surface of the analytical substrate, and it can be changed depending on the actual use of the compound to be analyzed, so it cannot be generally stated, but it is preferably 0.01 m / s or more, more preferably 0.03 mm / s or more, even more preferably 0.05 mm / s or more, and even more preferably 0.08 mm / s or more, and the upper limit is preferably 1.0 mm / s or less, more preferably 0.75 mm / s or less, even more preferably 0.50 mm / s or less, and even more preferably 0.15 mm / s or less.As mentioned above, the upper and lower limits of these numerical ranges can be arbitrarily combined, and typical examples include combinations of 0.01 m / s or more and 1.0 mm / s or less, 0.03 mm / s or more and 0.75 mm / s or less, 0.05 mm / s or more and 0.50 mm / s or less, and 0.08 mm / s or more and 0.15 mm / s or less. When the rotation speed is within the above range, the friction state on the friction surface tends to be stable, and the compounds adsorbed on the metal surface can be analyzed more stably and with high sensitivity.

[0050] The pressing load of the driving tool is not particularly limited as long as it can generate friction between the metal surface embedded in the recess of the flat surface of the analytical substrate, and it cannot be generally stated because it can change depending on the actual use of the compound to be analyzed, but it is preferably 0.1N or more, more preferably 0.3N or more, even more preferably 0.5N or more, and even more preferably 0.8N or more, and the upper limit is preferably 5N or less, more preferably 3N or less, and even more preferably 1.5N or less. As mentioned above, the upper and lower limits of these numerical ranges can be arbitrarily combined, and typical examples include combinations of 0.1N or more and 5N or less, 0.3N or more and 3N or less, 0.5N or more and 1.5N or less, and 0.8N or more and 1.5N or less. When the pressing load is within the above range, the friction state on the friction surface is likely to be stable, and the compound adsorbed on the surface of the metal can be analyzed more stably and with high sensitivity.

[0051] (others) The friction test analysis device of this embodiment may have a storage tank 4, as shown in Fig. 1. Analysis can be started by storing a liquid containing a compound to be measured in the storage tank, and analysis can be easily performed.

[0052] [Friction test analysis method] The friction test analysis method of the present embodiment includes: An analytical method for analyzing a compound contained in a liquid, comprising the steps of: The compound adsorbed on the metal surface is analyzed by ATR-SEIRAS (attenuated total reflection-surface enhanced infrared spectroscopy) while conducting a friction test. Friction test analysis method.

[0053] The friction test analysis method of this embodiment can be performed, for example, by using the friction test analysis device of this embodiment described above. Therefore, the friction test analysis method of this embodiment can analyze the adsorption behavior of a compound contained in a liquid in a friction environment with high sensitivity.

[0054] [Substrate for friction test analysis] The friction test analysis substrate of this embodiment is The optical fiber is made of an ATR crystal and a metal, has a flat surface on a part thereof, has a plurality of recesses on the flat surface, and has the metal embedded in the recesses. This is a substrate for friction test analysis.

[0055] The friction test analysis substrate of this embodiment can be used as an analysis substrate in the friction test analysis device of this embodiment, for example. That is, the details of the friction test analysis substrate of this embodiment are the same as those described as an analysis substrate that can be used in the friction test analysis device.

[0056] [One aspect of the present invention provided] In this embodiment, the following 1 to 14 are provided. 1. An analytical device for analyzing compounds contained in a liquid, comprising an analytical substrate, an analytical instrument, and a friction test instrument, the analytical substrate is made of an ATR crystal and a metal, has a flat surface on a part thereof, a plurality of recesses are arranged on the flat surface, and the metal is embedded in the recesses; the analytical instrument is an instrument for analyzing the compound adsorbed on the surface of the metal of the analytical substrate by an ATR-SEIRAS method (attenuated total reflection-surface enhanced infrared spectroscopy); The friction tester includes a test piece and a drive jig that rotates the test piece, the driving jig rotates and drives the test piece while pressing the test piece against the flat surface having the recess of the analytical substrate. Friction test analysis equipment. 2. The friction test analysis device according to claim 1, wherein the analytical substrate is in the form of a plate. 3. The friction test analysis device according to claim 1, wherein the analytical substrate is hemispherical. 4. The friction test analysis device according to any one of the above 1 to 3, wherein the ATR crystal is silicon. 5. The friction test analysis device according to any one of 1 to 4 above, wherein the metal is at least one selected from the group consisting of gold, silver, copper, platinum, iron and nickel. 6. The friction test analysis device according to any one of 1 to 5 above, wherein the thickness of the metal is 5 nm or more and 100 nm or less. 7. The friction test analysis device according to any one of 1 to 6 above, wherein the recesses have a shape selected from a triangle, a rectangle, an ellipse and a circle in a plan view, and are arranged in a pattern. 8. The friction test analysis device according to any one of the above 1 to 7, wherein the test piece has a shape selected from the group consisting of a disk shape, a cylinder shape, a sphere shape, and an elliptical sphere shape. 9. The friction test analysis device according to any one of the above items 1 to 8, wherein the liquid is a lubricating oil composition containing the compound. 10. An analytical method for analyzing a compound contained in a liquid, comprising: The compound adsorbed on the metal surface is analyzed by ATR-SEIRAS (attenuated total reflection-surface enhanced infrared spectroscopy) while conducting a friction test. Friction test analysis method. 11. The friction test analysis method according to the above item 10, wherein the analysis is carried out using the analysis device according to any one of the above items 1 to 9. 12. A friction test analysis substrate comprising an ATR crystal and a metal, having a flat surface on one side, a plurality of recesses arranged on said flat surface, and said metal embedded in said recesses. 13. A friction test analysis substrate as described in 12 above, wherein the recesses have a shape selected from a triangle, a rectangle, an ellipse, and a circle when viewed in a plane, and are arranged at equal intervals on the plane in a pattern. 14. A substrate for friction test analysis as described in 12 or 13 above, which is used in the analytical device as described in any one of 1 to 9 above. EXAMPLES

[0057] The present invention will now be described in detail with reference to examples, but the present invention is not limited to these examples in any way.

[0058] [Friction test analysis device] The apparatus used had the configuration shown in Figure 1. The analytical substrate and friction test equipment constituting the apparatus are outlined below.

[0059] (Base material for analysis) An analytical substrate was prepared using hemispherical silicon (Si) as the ATR crystal, with multiple recesses (rectangles with a length of 0.81 μm and a width of 0.81 μm in plan view, and a depth of 0.04 μm) on the plane of the ATR crystal, with the metal embedded in the recesses being Au with thicknesses (8, 19, 12, 15, and 30 nm) as shown in Table 1. The analytical substrate was produced according to the method for producing the analytical substrate described above, more specifically, a resist film was formed on the surface of the ATR crystal, a resist pattern was formed to form the following pattern, and then etching was performed to remove the resist film to form the following pattern, and further a thin film of Au having the above thickness was formed by vacuum deposition so as to be embedded in the recesses. In addition, the multiple recesses all have the same shape and are arranged in a pattern (grid shape, distance between adjacent recesses (w2): 0.19 μm). An SEM image of the surface of the analytical substrate used in this example is shown in FIG.

[0060] (Friction testing equipment) The test piece used in the friction test device was a sphere (diameter: 12.7 mm) made of SUJ2.

[0061] (Liquid containing compounds) The liquid containing the compound to be measured has a dynamic viscosity of 5 mm 2 A hydrocarbon lubricant base oil having a viscosity of 100°C (23±3°C) was used, and the content of the compound to be measured was adjusted to 5% by mass. 4-Cyano-4'-pentylbiphenyl was used as the compound to be measured.

[0062] (Analysis and evaluation of measurement targets) The feasibility of analyzing the target compound was evaluated based on the following evaluation criteria. (Evaluation Criteria) A: High sensitivity analysis has become possible. C: Analysis was not possible.

[0063] (Evaluation of the effect of enhancing infrared absorption intensity) In each example, the liquid containing the compound was a poly-α-olefin solution of oleic acid (oleic acid content: 0.1 mass%, poly-α-olefin: 40°C kinematic viscosity 48 mm 2 The absorption area of ​​the wavelength caused by C=O due to oleic acid when the analysis was performed instead of the conventional oleic acid (1.0 mass % oleic acid solution, 40°C kinematic viscosity 48 mm3 / s) was defined as Ar1. 2 When the analysis was performed instead of using the 1000 nm wavelength absorption spectrum (100 nm / s), the absorption area of ​​the wavelength caused by C=O due to oleic acid was defined as Ar2. In this case, the numerical value calculated by the following formula was defined as the enhancement effect index, and the numerical value was evaluated based on the following evaluation criteria. Enhancement effect index = Ar1 / Ar2 / 10 x 100 (Evaluation Criteria) A: The enhancement effect index is 5 or higher. B: The enhancement effect index was 2 or more and less than 5. C: The enhancement index was less than 2.

[0064] Example 1 In an apparatus having the configuration shown in FIG. 1 (thickness of Au in the analytical substrate: 8 nm), a liquid containing the above compound was supplied to the reservoir. Then, the friction tester was operated (rotation speed: 0.1 m / s, pressing load: 1 N). Infrared light was focused on the friction surface between the test piece of the friction tester and the analytical substrate, and the absorption spectrum of the totally reflected infrared light was measured. The measured absorption spectrum is shown in FIG. 5. FIG. 5 shows the absorption spectrum measured every 25 μm from the contact center of the ball at 0 μm position to +200 μm and -200 μm in the shear direction. The analysis and enhancement effects were evaluated by the methods described above, and the results are shown in Table 1.

[0065] (Examples 2 to 5) The absorption spectrum was measured in the same manner as in Example 1, except that the analytical substrate was changed to one having an Au thickness shown in Table 1. The analysis and enhancement effects were evaluated by the methods described above, and the results are shown in Table 1.

[0066] Comparative Example 1 The analysis was carried out in the same manner as in Example 2, except that no friction test equipment was used. Although the compounds to be measured could be analyzed, the results could not be said to be those obtained under a friction environment.

[0067] Comparative Example 2 The absorption spectrum was measured in the same manner as in Example 1, except that an analytical substrate in which Au was not embedded in the recesses (an ATR crystal in which multiple recesses were formed and no Au was provided) was used. The measured absorption spectrum is shown in Figure 6. Figure 6 shows the absorption spectrum measured every 25 µm from the contact center of the ball as the 0 µm position to +200 µm and -200 µm in the shear direction. The analysis and enhancement effects were evaluated by the methods described above, and the results are shown in Table 1.

[0068] Comparative Example 3 In Example 1, the absorption spectrum was measured in the same manner as in Example 1, except that the analytical substrate used had no recesses and was entirely coated with 50 nm thick Au by vapor deposition. The analysis and the enhancement effect were evaluated by the above-mentioned methods. The results are shown in Table 1.

[0069] [Table 1]

[0070] From the results of the Examples and Comparative Examples, it was confirmed that when the friction test analysis device of the present embodiment was used, both the analytical evaluation and the evaluation of the enhancing effect were excellent, and the adsorption behavior of a compound contained in a liquid under a friction environment can be analyzed with high sensitivity. On the other hand, in Comparative Example 1, since an apparatus not having a friction tester was used, it was naturally impossible to perform measurements under a friction environment. In Comparative Example 2, since no metal was embedded in the analytical substrate, the evaluation of the enhancement effect was poor, and it was found that analysis could not be performed with high sensitivity. In addition, Comparative Example 3 is an example in which an analytical substrate without a recess was used, but it was found that the enhancement effect could not be obtained unless the metal was embedded in the recess.

[0071] Regarding the absorption spectra of FIGS. 5 and 6, the structures of peaks 1 to 6 shown in the figures in the compound to be measured (4-cyano-4'-pentylbiphenyl) which exhibits these peaks are as follows: Peak 1. (3050-2750cm -1 ): All CH bonds Peak 2. (2250-2200cm -1 ):CN bond Peak 3. (1630-1480cm -1 ): C-C bond in phenyl group Peak 4. (1480-1350cm -1 ): C—H bond in alkyl group (pentyl group) Peak 5. (1200-1170cm-1 ):CH bond in phenyl group (in-plane measurement) Peak 6. (880-750cm -1 ):CH bond in phenyl group (out-of-plane measurement)

[0072] In order to make the change in absorption easier to understand for the absorption spectra in Figures 5 and 6, the absorption area of ​​each substituent was calculated, and the difference calculated by the following method was plotted in Figure 7. The difference was calculated as (Example, Figure 5) - k (coefficient) x (Comparative Example, Figure 6), where the coefficient k is "Peak 4. (1480 to 1350 cm -1 The differences in the other peaks were determined so that the absorption area of ​​"C-H bond in the alkyl group (pentyl group)" was zero. Note that (a) to (f) in FIG. 7 respectively show the differences in the above peaks 1 to 6, and (d), which corresponds to peak 4 in FIG. 7, is zero. In Figure 7, the absorption difference between (a) and (e) is small, but the absorption difference of the C-H bond in the out-of-plane measurement of the phenyl group in Figure 7(f) is specifically increased around the contact area between the ball and the prism (100-200 μm). Here, the enhanced absorption of the C-H bond in the out-of-plane measurement of the phenyl group is considered to mean that the aromatic ring is oriented parallel to the surface of the analytical substrate. This is because it is known that surface-enhanced infrared spectroscopy enhances the absorption of vibrations perpendicular to the surface of the analytical substrate and reduces the absorption of vibrations horizontal to zero (see, for example, Review of Polarography, Vol. 62, No. 2 / 3, (2016)). [Industrial Applicability]

[0073] The friction test analysis device of this embodiment is an apparatus capable of analyzing the adsorption behavior of compounds contained in a liquid under a friction environment with high sensitivity. The friction test analysis device of this embodiment can grasp the adsorption behavior of various additives used in a lubricating oil composition under a friction environment, and therefore can be suitably used for designing a lubricating oil composition.

Claims

1. An analytical apparatus comprising analytical substrates, analytical instruments, and friction testing equipment, for analyzing compounds contained in a liquid, The analytical substrate is composed of ATR crystals and a metal, has a flat surface in part, has a plurality of recesses arranged on the flat surface, and the metal is embedded in the recesses. The aforementioned analytical instrument is an instrument that analyzes the compound adsorbed on the surface of the metal on the analytical substrate using the ATR-SEIRAS method (total internal reflection absorption-surface enhanced infrared spectroscopy), The friction testing apparatus comprises a test piece and a drive jig for rotating the test piece. The drive jig rotates the test piece while pressing it against the plane having the recess of the analytical substrate. Friction testing and analysis device.

2. The friction test analysis apparatus according to claim 1, wherein the analytical substrate is in the form of a plate.

3. The friction test analysis apparatus according to claim 1, wherein the analytical substrate is hemispherical.

4. The friction test and analysis apparatus according to any one of claims 1 to 3, wherein the ATR crystal is silicon.

5. The friction test and analysis apparatus according to any one of claims 1 to 3, wherein the metal is at least one selected from gold, silver, copper, platinum, iron, and nickel.

6. The friction test and analysis apparatus according to any one of claims 1 to 3, wherein the thickness of the metal is 5 nm or more and 100 nm or less.

7. The friction test and analysis apparatus according to any one of claims 1 to 3, wherein the recesses have a shape selected from a triangle, a square, an ellipse, and a circle as a plan view, and are arranged in a pattern.

8. The friction test and analysis apparatus according to any one of claims 1 to 3, wherein the test piece has a shape selected from a disc, a cylinder, a sphere, and an ellipsoid.

9. The friction test and analysis apparatus according to any one of claims 1 to 3, wherein the liquid is a lubricating oil composition containing the compound.

10. An analytical method for analyzing compounds contained in a liquid, The compound adsorbed on the metal surface is analyzed using the ATR-SEIRAS method (total internal reflection absorption-surface enhanced infrared spectroscopy) while performing a friction test. Methods for friction testing and analysis.

11. The friction test analysis method according to claim 10, wherein the analysis is performed using the analytical apparatus described in any one of claims 1 to 3.

12. A substrate for friction testing and analysis, comprising ATR crystals and a metal, having a flat surface in part, with a plurality of recesses arranged on the flat surface, and the metal embedded in the recesses.

13. The friction test analysis substrate according to claim 12, wherein the recesses have a shape selected from a triangle, a square, an ellipse, and a circle as a plan view, and are arranged at equal intervals on the plane in a pattern.

14. A friction test analysis substrate according to claim 12 or 13, used in the analytical apparatus according to any one of claims 1 to 3.

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