Method for evaluating the degree of surface coverage of dyes and silicon oxide coatings, and method for comparing and evaluating the degree of surface coverage of metal oxide particles coated with silicon oxide coatings.

Abstract

This invention provides a dye capable of evaluating the degree of surface coverage of metal oxide particles coated with a silicon oxide film, a method for evaluating the degree of surface coverage of a silicon oxide film using the dye, and a method for comparing and evaluating the degree of surface coverage of metal oxide particles coated with a silicon oxide film. [Solution] A dye represented by the following general formula (1), used to evaluate the degree of surface coverage of metal oxide particles coated with a silicon oxide film. [C1] TIFF2026106039000039.tif32170

Description

[Technical Field]

[0001] The present invention relates to a method for evaluating the degree of surface coverage of a dye and a silicon oxide coating, and a method for comparing and evaluating the degree of surface coverage of metal oxide particles coated with a silicon oxide coating. [Background technology]

[0002] Metal oxide particles, such as zinc oxide particles, are added to various compositions to impart functions such as UV shielding and gas barrier properties. When metal oxide particles are applied to a composition, the surface of the metal oxide particles is treated with a surface treatment agent to match the properties of the composition or to suppress the catalytic activity of the metal oxide particles.

[0003] For example, when zinc oxide particles are incorporated into oily cosmetics or emulsion-type oil phases, zinc oxide particles that have been surface-treated with a silane coupling agent having an alkoxy group are used (see, for example, Patent Document 1).

[0004] However, while it has been possible to confirm that metal oxide particles, such as zinc oxide particles, are surface-treated by surface treatment agents such as silane coupling agents by improving their dispersibility in the oil phase, there has been no method to quantitatively and accurately confirm the extent to which the surface treatment of the metal oxide particles has progressed. Therefore, there was a need for a simple and accurate method to evaluate the surface condition of metal oxide particles.

[0005] To solve this problem, dyes that can selectively adsorb onto hydroxyl groups bonded to metal atoms (hereinafter sometimes abbreviated as "metallic hydroxyl groups") and evaluation methods that use these dyes to evaluate the extent to which the surface treatment of metal oxide particles has progressed are known (see, for example, Patent Document 2). [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] International Publication No. 2017 / 130632 [Patent Document 2] International Publication No. 2023 / 163108 [Summary of the Invention] [Problems to be Solved by the Invention]

[0007] Regarding the red dye described in Patent Document 2, the degree of surface treatment with a surface treatment agent having no metal hydroxyl group such as a silane coupling agent can be evaluated. However, for metal oxide particles coated with a silicon oxide film, since the dye reacts with the OH groups on the surface of the silicon oxide film, it has not been possible to quantitatively and accurately confirm the degree to which the coating treatment of the silicon oxide film on the surface of the metal oxide particles has progressed.

[0008] Therefore, there has been a need for a method for simply and accurately evaluating the surface state of metal oxide particles coated with a silicon oxide film.

[0009] The present invention has been made in view of the above circumstances, and an object thereof is to provide a dye capable of evaluating the degree of surface coating by silicon oxide coating of metal oxide particles coated with a silicon oxide film, a method for evaluating the degree of surface coating of a silicon oxide film using the dye, and a method for comparative evaluation of the degree of surface coating of metal oxide particles coated with a silicon oxide film. [Means for Solving the Problems]

[0010] The present invention has the following aspects. [1] A dye represented by the following general formula (1), which is used for evaluating the degree of surface coating of metal oxide particles coated with a silicon oxide film.

[0011] [Chemical Formula] (However, M is Sn or Ge, R1 is an alkyl group or a phenyl group, Y1 and Y2 are hydrogen, a halogen group, a methyl group, an alkoxy group, a phenyl group, a diphenylamide group, a thiophenyl group, or a phenylethynyl group, and Z is a single bond or represented by formula (2) below.)

[0012] [ka] (However, R2 is an alkyl group or a phenyl group.)

[0013] [2] A step of preparing a solution by mixing a dye represented by the following general formula (1) with an organic solvent, The steps include: preparing metal oxide particles coated with a silicon oxide film, A step of evaluating the color x of the solution, The steps include: adding metal oxide particles coated with the silicon oxide film to the aforementioned solution to prepare a mixture A, and evaluating the color a of the mixture A; A method for evaluating the surface coverage of a silicon oxide film, comprising the steps of evaluating the difference between the aforementioned color x and the aforementioned color a, and evaluating the amount of metal hydroxyl groups of the metal oxide particles from the obtained evaluation results.

[0014] [ka] (However, M is Sn or Ge, R1 is an alkyl group or a phenyl group, Y1 and Y2 are hydrogen, a halogen group, a methyl group, an alkoxy group, a phenyl group, a diphenylamide group, a thiophenyl group, or a phenylethynyl group, and Z is a single bond or represented by formula (2) below.)

[0015] [ka] (However, R2 is an alkyl group or a phenyl group.)

[0016] [3] A method for evaluating the degree of surface coverage of metal oxide particles coated with a silicon oxide film, using a dye represented by the following general formula (1): The steps include: mixing the aforementioned dye with an organic solvent to prepare a solution; The steps include: preparing metal oxide particles and silicon oxide-coated metal oxide particles obtained by coating the metal oxide particles with a silicon oxide film; The steps include: adding the metal oxide particles to the aforementioned solution to prepare a mixture A, and evaluating the color a of the mixture A; The steps include: adding the silicon oxide-coated metal oxide particles to the aforementioned solution to prepare a mixture B, and evaluating the color b of the mixture B; A method for evaluating the surface coverage of a silicon oxide coating, comprising the steps of: evaluating the difference between the obtained color a and the obtained color b; and evaluating the difference between the amount of metal hydroxyl groups a of the metal oxide particles and the amount of metal hydroxyl groups b of the silicon oxide coated metal oxide particles from the obtained evaluation results.

[0017] [ka] (However, M is Sn or Ge, R1 is an alkyl group or a phenyl group, Y1 and Y2 are hydrogen, a halogen group, a methyl group, an alkoxy group, a phenyl group, a diphenylamide group, a thiophenyl group, or a phenylethynyl group, and Z is a single bond or represented by formula (2) below.)

[0018] [ka] (However, R2 is an alkyl group or a phenyl group.)

[0019] [4] A method for comparing and evaluating the degree of surface coverage of metal oxide particles 1 coated with a silicon oxide film and metal oxide particles 2 coated with a silicon oxide film, using a dye represented by the following general formula (1): The steps include: mixing the aforementioned dye with an organic solvent to prepare a solution; The steps include preparing metal oxide particles 1 coated with a silicon oxide film and metal oxide particles 2 coated with a silicon oxide film, A step of evaluating the color x of the solution, The steps include: adding the metal oxide particles 1 to the solution to prepare a mixture A, and evaluating the color a1 of the mixture A; The steps include: adding the metal oxide particles 2 to the aforementioned solution to prepare a mixed solution B, and evaluating the color b1 of the mixed solution B; The steps include evaluating the difference between the obtained color x and the obtained color a1, and evaluating the amount of metallic hydroxyl groups a of the metal oxide particles 1 from the obtained evaluation results, The steps include evaluating the difference between the obtained color x and the obtained color b1, and evaluating the amount of metal hydroxyl groups b of the metal oxide particles 2 from the obtained evaluation results, A method for comparing and evaluating the degree of surface coverage of metal oxide particles coated with a silicon oxide film, comprising the step of evaluating the difference between the amount of metal hydroxyl groups a and the amount of metal hydroxyl groups b.

[0020] [ka] (However, M is Sn or Ge, R1 is an alkyl group or a phenyl group, Y1 and Y2 are hydrogen, a halogen group, a methyl group, an alkoxy group, a phenyl group, a diphenylamide group, a thiophenyl group, or a phenylethynyl group, and Z is a single bond or represented by formula (2) below.)

[0021] [ka] (However, R2 is an alkyl group or a phenyl group.)

[0022] [5] A method for evaluating the degree of surface coverage of a silicon oxide film on the surface of metal oxide particles when the metal oxide particles are surface-treated with a silicon oxide film, The process involves mixing a dye represented by the following general formula (1) with an organic solvent to prepare a solution, The process involves preparing metal oxide particles 1 before surface treatment and metal oxide particles 2 after surface treatment, The steps include measuring the absorbance x of the solution, The steps include: adding the metal oxide particles 1 before surface treatment to the solution to prepare a mixture A, and measuring the absorbance a1 of the mixture A; The steps include: adding the surface-treated metal oxide particles 2 to the solution to prepare a mixture B, and measuring the absorbance b1 of the mixture B; The steps include: calculating the rate of decrease a2 in the absorbance of the mixed solution A by dividing the value obtained by subtracting the absorbance a1 from the absorbance x by the absorbance x ((x-a1) / x); The steps include: calculating the rate of decrease b2 in the absorbance of the mixed solution B by dividing the value obtained by subtracting the absorbance b1 from the absorbance x by the absorbance x ((x-b1) / x); The steps include: calculating the amount of dye adsorbed onto the metal oxide particles 1 a3 (mol / g) by multiplying the absorbance reduction rate a2 by the number of moles of the dye contained in the mixed solution A and dividing by the amount of metal oxide particles 1 added to the solution A (a2 × number of moles of dye contained in the mixed solution A / amount of metal oxide particles 1 added to the solution A); The steps include: calculating the amount of dye adsorbed onto the metal oxide particles 2 b3 (mol / g) by multiplying the absorbance reduction rate b2 by the number of moles of the dye contained in the mixed solution B and dividing by the amount of metal oxide particles 2 added to the solution B (b2 × number of moles of dye contained in the mixed solution B / amount of metal oxide particles 2 added to the solution B); A method for evaluating the surface coverage degree of a silicon oxide film, comprising the step of calculating the degree of coverage of the silicon oxide film by the surface treatment by subtracting from 100 the value obtained by dividing the adsorption amount b3 by the adsorption amount a3 and multiplying the result by 100 (100 - ((b3 / a3) × 100)).

[0023] [ka] (However, M is Sn or Ge, R1 is an alkyl group or a phenyl group, Y1 and Y2 are hydrogen, a halogen group, a methyl group, an alkoxy group, a phenyl group, a diphenylamide group, a thiophenyl group, or a phenylethynyl group, and Z is a single bond or represented by formula (2) below.)

[0024] [ka] (However, R2 is an alkyl group or a phenyl group.)

[0025] [6] A method for evaluating the degree of surface coverage of a silicon oxide film on the surface of metal oxide particles when the metal oxide particles are surface-treated with a silicon oxide film, The process involves mixing a dye represented by the following general formula (1) with an organic solvent to prepare a solution, The process involves preparing metal oxide particles 1 before surface treatment and metal oxide particles 2 after surface treatment, The steps include measuring the absorbance x of the solution, The steps include: adding the metal oxide particles 1 before surface treatment to the solution to prepare a mixture A, and measuring the absorbance a1 of the mixture A; The steps include: adding the surface-treated metal oxide particles 2 to the solution to prepare a mixture B, and measuring the absorbance b1 of the mixture B; The steps include: calculating the rate of decrease a2 in the absorbance of the mixed solution A by dividing the value obtained by subtracting the absorbance a1 from the absorbance x by the absorbance x ((x-a1) / x); The steps include: calculating the rate of decrease b2 in the absorbance of the mixed solution B by dividing the value obtained by subtracting the absorbance b1 from the absorbance x by the absorbance x ((x-b1) / x); The steps include: calculating the amount of dye adsorbed onto the metal oxide particles 1 a3 (mol / g) by multiplying the absorbance reduction rate a2 by the number of moles of the dye contained in the mixed solution A and dividing by the amount of metal oxide particles 1 added to the solution A (a2 × number of moles of dye contained in the mixed solution A / amount of metal oxide particles 1 added to the solution A); The steps include: calculating the amount of dye adsorbed onto the metal oxide particles 2 b3 (mol / g) by multiplying the absorbance reduction rate b2 by the number of moles of the dye contained in the mixed solution B and dividing by the amount of metal oxide particles 2 added to the solution B (b2 × number of moles of dye contained in the mixed solution B / amount of metal oxide particles 2 added to the solution B); A method for evaluating the surface coverage of a silicon oxide film, comprising the step of calculating the degree of uncovered silicon oxide film using the value obtained by dividing the adsorption amount b3 by the adsorption amount a3.

[0026] [ka] (However, M is Sn or Ge, R1 is an alkyl group or a phenyl group, Y1 and Y2 are hydrogen, a halogen group, a methyl group, an alkoxy group, a phenyl group, a diphenylamide group, a thiophenyl group, or a phenylethynyl group, and Z is a single bond or represented by formula (2) below.)

[0027] [ka] (However, R2 is an alkyl group or a phenyl group.) [Effects of the Invention]

[0028] The dye of the present invention can be adsorbed onto metal hydroxyl groups, while it does not readily react with OH groups, i.e., silanol groups, present on the surface of the silicon oxide coating. Therefore, the degree of surface coverage of metal oxide particles coated with silicon oxide can be evaluated.

[0029] According to the method for evaluating the degree of surface coverage of a silicon oxide film of the present invention, the dye of the present invention can be adsorbed onto metal hydroxyl groups, while it does not readily react with the silanol groups of the silicon oxide film. Therefore, the degree of coverage of metal oxide particles by the silicon oxide film can be evaluated.

[0030] According to the method for comparing and evaluating the degree of surface coverage of metal oxide particles coated with the silicon oxide film of the present invention, the dye of the present invention can be adsorbed onto metal hydroxyl groups, while it does not readily react with the silanol groups of the silicon oxide film. Therefore, the amount of metal hydroxyl groups contained in the silicon oxide coated metal oxide particles can be evaluated qualitatively and quantitatively. [Modes for carrying out the invention]

[0031] Embodiments of the present invention, including a method for evaluating the surface coverage of a dye and silicon oxide film, and a method for comparing and evaluating the surface coverage of metal oxide particles coated with a silicon oxide film, will be described. This embodiment is provided to give a better understanding of the spirit of the invention and does not limit the present invention unless otherwise specified.

[0032] [Pigment] The dye in this embodiment is a compound represented by the following general formula (1). The dye in this embodiment is used to evaluate the degree of surface coverage of metal oxide particles coated with a silicon oxide film.

[0033] [ka] (However, M is Sn or Ge, R1 is an alkyl group or a phenyl group, Y1 and Y2 are hydrogen, a halogen group, a methyl group, an alkoxy group, a phenyl group, a diphenylamide group, a thiophenyl group, or a phenylethynyl group, and Z is a single bond or represented by formula (2) below.)

[0034] [ka] (However, R2 is an alkyl group or a phenyl group.)

[0035] When R1 and R2 are alkyl groups, they are not particularly limited as long as they do not inhibit the reaction in which the dye of this embodiment coordinates to the metal hydroxyl group. The number of carbon atoms in the alkyl group is preferably 1 or more, more preferably 1 to 20, and even more preferably 3 to 10.

[0036] In this embodiment, Y1 and Y2 are exemplified by hydrogen, halogen groups, methyl groups, alkoxy groups, phenyl groups, diphenylamide groups, thiophenyl groups, or phenylethynyl groups. However, Y1 and Y2 are not particularly limited as long as they are groups whose color changes depending on electron-withdrawing, electron-donating, or conjugation expansion. In other words, Y1 and Y2 may be any groups that can color the material. The above halogen group is one selected from the group consisting of F, Cl, Br, and I. Y1 and Y2 may be the same group or different groups.

[0037] Specific examples of compounds represented by the above general formula (1) include, for example, the dyes represented by the following formulas (3) and (4).

[0038] [ka]

[0039] The dye represented by formula (3) above is orange in color and absorbs light at a wavelength of around 457 nm.

[0040] [ka]

[0041] The dye represented by formula (4) above is yellow and absorbs light at a wavelength of around 454 nm.

[0042] The dye in this embodiment adsorbs to metal hydroxyl groups, while being less reactive with silicon dioxide particles and silanol groups of silicon dioxide coatings. The mechanism is presumed to be as follows: The dye in this embodiment has an N=C group in its structure. If the structure at this point were an N=N red dye, the N=N would act as an amine on the Si-OH group, which acts as an acid. Therefore, the N=N in the red dye would react with the Si-OH group, destroying the structure of the red dye and making proper evaluation impossible. Alternatively, because the metallic hydroxyl group has a higher nucleophilicity ranking than the silanol group, it can selectively adsorb to the dye regardless of whether the dye structure is N=N or N=C. However, because the silanol group has a lower nucleophilicity ranking, it cannot selectively adsorb to the silanol group in the dye of this embodiment, which has an N=C structure. In other words, by selecting an N=C structure instead of an N=N structure, the resulting dye does not react with or adsorb to silanol groups, making it possible to evaluate the progress of the reaction of surface treatment agents containing silanol groups, such as silicon dioxide coatings.

[0043] The dye in this embodiment does not react with the hydroxyl groups of water or alcohol. Furthermore, it reacts poorly with silanol groups. Therefore, when the dye in this embodiment comes into contact with metal oxide particles coated with a silicon oxide film, the dye selectively adsorbs onto the metal hydroxyl groups present on the surface of the silicon oxide-coated metal oxide particles. In other words, the dye adsorbs to areas not covered by the silicon oxide film, causing the color of the dye to change from its original color to a color on the shorter wavelength side. The method for bringing the above-mentioned dye into contact with the silicon oxide-coated metal oxide particles is not particularly limited. For example, the dye and the silicon oxide-coated metal oxide particles may be directly mixed and brought into contact. Alternatively, contact may be brought into contact by adding the silicon oxide-coated metal oxide particles to a solution obtained by dissolving the dye in an organic solvent. From the viewpoint of ensuring uniform contact, it is preferable to add the silicon oxide-coated metal oxide particles to a solution obtained by dissolving the dye in an organic solvent and then bring the dye and silicon oxide-coated metal oxide particles into contact.

[0044] The metallic hydroxyl group in this embodiment is not particularly limited as long as the dye of this embodiment adsorbs it, but Si-OH is excluded. The metal of the metallic hydroxyl group may be a typical metal element, a transition metal element, a lanthanide, or an actinide. In this embodiment, a metallic hydroxyl group refers to a hydroxyl group bonded to a metal atom, and the metal may be in any form. For example, it may be in the state of a metal, or it may be in the state of a compound such as an oxide.

[0045] The dye represented by the general formula (1) above undergoes hexa-coordination when the five-coordinating M reacts with a metal hydroxyl group. This change in coordination number increases the electron density of M, and the R1 group becomes perpendicular, reducing its electron-withdrawing properties. Consequently, the LUMO energy level rises, resulting in a broader bandgap. In other words, the five-coordinating dye in the general formula (1) undergoes hexa-coordination upon reaction with a metal hydroxyl group, causing the absorption peak to shift to shorter wavelengths. Therefore, when the dye is adsorbed onto a metal hydroxyl group, the yellow dye changes to a greenish color. By utilizing this color change of the dye, the amount of metal hydroxyl groups in silicon oxide-coated metal oxide particles can be quantitatively evaluated. This allows for the evaluation of the degree to which the metal oxide particles are surface-coated by the silicon oxide film.

[0046] Furthermore, since the amount of metallic hydroxyl groups in the dye of this embodiment is evaluated by the change in color, it is also possible to visually evaluate the approximate amount of metallic hydroxyl groups, that is, the degree of surface coverage of the metal oxide particles by the silicon oxide film. The dye of this embodiment is highly stable and easy to handle, and it allows for the simple and accurate evaluation of whether or not metal hydroxyl groups are present on the surface of silicon dioxide-coated metal oxide particles, and the amount of metal hydroxyl groups present.

[0047] [Method for manufacturing pigments] (First Embodiment) The method for producing the dye according to this embodiment comprises a mixing step of mixing a ligand represented by the following general formula (5) or a ligand represented by the following general formula (6) with a metal source represented by the following general formula (7), and a coordination step of coordinating the metal source represented by the following general formula (7) to the ligand represented by the following general formula (5) or a ligand represented by the following general formula (6).

[0048] [ka] (However, Y1 and Y2 are hydrogen, halogen groups, methyl groups, alkoxy groups, phenyl groups, diphenylamide groups, thiophenyl groups, or phenylethynyl groups.)

[0049] [ka] (However, Y1 and Y2 are hydrogen, halogen groups, methyl groups, alkoxy groups, phenyl groups, diphenylamide groups, thiophenyl groups, or phenylethynyl groups, and R is an alkyl group or a phenyl group.)

[0050] [ka] (However, M is at least one selected from the group consisting of Sn, Ge, and Bi, and R is an alkyl group or a phenyl group.)

[0051] Both the ligand represented by the above general formula (5) and the ligand represented by the above general formula (6) can be synthesized by the corresponding condensation reaction of an aldehyde and an amine.

[0052] The method for coordinating the above-mentioned ligand with the above-mentioned metal source is not particularly limited; the ligand and the above-mentioned metal source can be mixed and reacted. From the viewpoint of obtaining a homogeneous reactant, it is preferable in the mixing step to mix the ligand, the metal source, and an organic solvent having 3 or more carbon atoms, and to coordinate the metal source to the ligand in the mixture.

[0053] The case in which a ligand represented by the above general formula (5) or the above general formula (6) is reacted with a metal source represented by the above general formula (7) will be described in detail. The method for producing the dye according to this embodiment comprises a mixing step of putting a ligand represented by the general formula (5) or the ligand represented by the general formula (6), a metal source represented by the general formula (7), and an organic solvent having 3 or more carbon atoms into a container and mixing them to form a mixed solution, and a coordination step of coordinating the metal source represented by the general formula (7) to the ligand represented by the general formula (5) or the ligand represented by the general formula (6) by a dehydration reaction.

[0054] Following the mixing step, a step may be performed to replace the air in the above container with another atmosphere. The other atmosphere may be, for example, a nitrogen atmosphere, an inert atmosphere, or a reduced-pressure atmosphere. From the viewpoint of reaction efficiency, a nitrogen atmosphere or an inert atmosphere is preferred.

[0055] The method for carrying out the dehydration reaction is not particularly limited; for example, the above mixture can be heated. If the above mixture contains an organic solvent with 3 or more carbon atoms, the mixture may be circulated.

[0056] In this embodiment, since a dehydration reaction is carried out, the organic solvent having 3 or more carbon atoms is not particularly limited as long as it can be mixed with water. From the viewpoint of removing unreacted substances by filtration, it is more preferable that the organic solvent having 3 or more carbon atoms does not dissolve the ligand and the metal source. Examples of such organic solvents include methanol, ethanol, 1-propanol, acetone, tetrahydrofuran, acetonitrile, and pyridine. Among these, acetone is preferred due to its ease of handling.

[0057] The amount of the organic solvent added to the above mixture is not particularly limited as long as it is an amount that can uniformly mix the ligand and the metal source. For example, the content of the organic solvent in the above mixture may be 0% by mass or more and 99% by mass or less, 10% by mass or more and 99% by mass or less, 30% by mass or more and 99% by mass or less, 50% by mass or more and 99% by mass or less, 70% by mass or more and 99% by mass or less, or 80% by mass or more and 99% by mass or less.

[0058] The heating temperature when heating the above mixture to carry out the dehydration reaction is not particularly limited as long as the dehydration reaction proceeds. For example, it may be 50°C to 100°C, or 60°C to 90°C.

[0059] The heating time when heating the above mixture is not particularly limited as long as the metal source coordinates to the ligand and the dye is produced. For example, it may be between 1 hour and 24 hours, or between 2 hours and 13 hours. The production of the dye can also be confirmed by the color of the reactants, so the heating time may be adjusted while observing the color of the reactants.

[0060] If the above mixture is heated to carry out a dehydration reaction, the dye of this embodiment can be obtained by diluting off the organic solvent from the mixture after the dehydration reaction. The method for diluting off the organic solvent is not particularly limited; the mixture can simply be dried. From the viewpoint of removing unreacted products, the dye of this embodiment may be obtained by filtering the mixture after the dehydration reaction and diluting off the organic solvent from the filtrate.

[0061] The method for producing the pigment in this embodiment may include a washing step after the dehydration reaction. If it is desired to wash away organic solvents with three or more carbon atoms used during the mixing of the above ligand and the above metal source, hexane, toluene, chloroform, etc., can be used as the washing organic solvent. A washed dye can be obtained by mixing a washing organic solvent with the obtained dye and then removing the organic solvent from the mixture. The method for removing the organic solvent is not particularly limited as long as the organic solvent is removed; it can be removed by heating and drying or vacuum drying.

[0062] If unreacted substances are to be removed, the unreacted substances can also be removed by mixing the above-mentioned washing organic solvent with the obtained dye, filtering the mixture, and then diluting off the organic solvent from the filtrate.

[0063] (Second embodiment) The method for producing the dye according to this embodiment comprises a mixing step of mixing a ligand represented by the above general formula (5) or a ligand represented by the above general formula (6), a metal source represented by the following general formula (8), a base, and an organic solvent, and a coordination step of coordinating the metal source represented by the following general formula (8) to the ligand represented by the above general formula (5) or a ligand represented by the above general formula (6).

[0064] [ka] (However, M is at least one selected from the group Sn, Ge, and Bi, R is an alkyl group or a phenyl group, and A is a halogen group.)

[0065] The case in which a ligand represented by the above general formula (5) or the above general formula (6) is reacted with a metal source represented by the above general formula (8) will be described in detail. The method for producing the dye according to this embodiment comprises a mixing step of putting a ligand represented by the general formula (5) or a ligand represented by the general formula (6), a metal source represented by the general formula (8), a base, and an organic solvent into a container and mixing them to form a mixed solution, and a coordination step of coordinating the metal source represented by the general formula (8) to the ligand represented by the general formula (5) or the ligand represented by the general formula (6) by a deoxidation reaction.

[0066] Following the mixing step, a step may be performed to replace the air in the above container with another atmosphere. The other atmosphere may be, for example, a nitrogen atmosphere, an inert atmosphere, or a reduced-pressure atmosphere. From the viewpoint of reaction efficiency, a nitrogen atmosphere or an inert atmosphere is preferred.

[0067] The method for carrying out the deoxidation reaction is not particularly limited; it is sufficient as long as the base can trap the acid. For example, the mixture can be stirred at room temperature. The amount of base used should be the amount necessary to allow the deoxidation reaction to proceed. Therefore, the amount of base should be mixed in an amount of 2 to 20 times the molar amount of the metal source.

[0068] The base is not particularly limited as long as it can trap the acid, but it is preferable to use a tertiary amine, and more preferably a tertiary alkylamine. Examples of bases that can be used include trimethylamine, triethylamine, diisopropylethylamine, tributylamine, trioctylamine, diazabicycloundecene, diazabicyclononene, and pyridine. Among these, triethylamine is preferred because it is easy to handle.

[0069] The organic solvent is not particularly limited as long as it does not inhibit the deoxidation reaction and does not dissolve the by-product salt. For example, tetrahydrofuran can be used as such an organic solvent. The amount of the above-mentioned organic solvent added is not particularly limited as long as it is an amount that can uniformly mix the above-mentioned ligand, the above-mentioned metal source, and the above-mentioned base. For example, the content of the above-mentioned organic solvent in the above-mentioned mixture may be 1% by mass or more and 99% by mass or less, 10% by mass or more and 99% by mass or less, 30% by mass or more and 99% by mass or less, 50% by mass or more and 99% by mass or less, 70% by mass or more and 99% by mass or less, or 80% by mass or more and 99% by mass or less.

[0070] The stirring time in the deoxidation process is not particularly limited as long as the above-mentioned dye is produced. For example, it may be between 1 hour and 24 hours, or between 2 hours and 13 hours. The production of the above-mentioned dye can also be confirmed by the color of the reactants, so the stirring time may be adjusted while observing the color of the reactants.

[0071] In this embodiment, the method for producing the pigment preferably includes a step to remove the by-product salt after the deoxidation reaction. The method for removing the salt is not particularly limited, and for example, filtration can be used.

[0072] The dye of this embodiment can be obtained by removing the organic solvent from the mixture after the deoxidation reaction, or from the filtrate obtained by filtering the mixture after the deoxidation reaction.

[0073] In this embodiment, the method for producing the dye may include steps to isolate the dye or to recrystallize it in order to increase the purity of the dye after removing the by-product salt.

[0074] According to the method for producing the pigment of this embodiment, the pigment of the above embodiment can be obtained by the above steps.

[0075] [solution] The solution of this embodiment comprises the dye of the above-described embodiment and an organic solvent. Since the above-mentioned dye is dissolved in the solution of this embodiment, if the organic solvent is colorless and transparent, it will be colored to a color of the same type as the dye.

[0076] The organic solvent is not particularly limited as long as it can dissolve the above-mentioned dye, but examples include methanol, ethanol, propanol, butanol, pentanol, hexanol, toluene, tetrahydrofuran, xylene, hexane, chloroform, benzene, methyl ethyl ketone, methyl isobutyl ketone, acetone, propylene glycol monomethyl ether, ethyl acetate, and butyl acetate. Furthermore, from the viewpoint of the concentration stability of the solution, it is preferable that the organic solvent has a high boiling point. In the solution of this embodiment, an organic solvent that readily dissolves the dye may be appropriately selected and used.

[0077] The concentration of the dye contained in the solution of this embodiment is not particularly limited, as long as the number of moles of the dye is greater than the number of moles of metal hydroxyl groups contained in the sample. To quantitatively evaluate the amount of metallic hydroxyl groups, the amount of the dye in this embodiment should be increased sufficiently within the range in which the dye dissolves. To simply qualitatively evaluate the adsorption of metallic hydroxyl groups visually, the concentration of the dye should be adjusted to a concentration in which the color change is easily observable. The concentration of the above-mentioned dye contained in the solution of this embodiment is, for example, 1 × 10⁻⁶ -10 It may be between mol / L and 1 mol / L.

[0078] If you want to evaluate the amount of metal hydroxyl groups on the surface of metal oxide particles, the concentration of the dye contained in the solution of this embodiment is 1 × 10⁻⁶ -3 mol / L or more 1×10 -7 It is preferable that the concentration is mol / L or less, and 1 × 10 -4 mol / L or more 1×10 -6 It is more preferable that the concentration is mol / L or less.

[0079] The solution of this embodiment may contain other components besides the above-mentioned dye and organic solvent, as long as they do not impair the effects of the present invention.

[0080] The dye contained in the solution of this embodiment selectively adsorbs to the metal hydroxyl groups contained in metal oxide particles that are exposed on the surface of silicon oxide-coated metal oxide particles without being coated with silicon oxide, and does not react with hydroxyl groups such as water or alcohol. Furthermore, it does not react easily with silanol groups contained in the silicon oxide coating. Therefore, the amount of metal hydroxyl groups exposed on the surface of the silicon oxide-coated metal oxide particles, i.e., in areas not covered by the silicon oxide coating, can be qualitatively and quantitatively evaluated without being affected by moisture. As a result, the extent to which the silicon oxide coating covers the metal oxide particles can be qualitatively and quantitatively evaluated. Moreover, since the dye of this embodiment does not react with hydroxyl groups such as water or alcohol, the solution of this embodiment is highly stable even in the atmosphere and easy to store.

[0081] When silicon oxide-coated metal oxide particles for evaluation are added to the solution of this embodiment, the silicon oxide-coated metal oxide particles precipitate in the solution, reducing the amount of dye contained in the solution, and thus the color of the solution becomes lighter. Furthermore, the dye adsorbed on the silicon oxide-coated metal oxide particles changes from its original color to a color on the shorter wavelength side. Therefore, to evaluate the degree of surface coating of metal oxide particles by silicon oxide coating, the color of the dye before and after adsorption onto the silicon oxide coated metal oxide particles may be used for evaluation, or the color of the solution before and after addition of the silicon oxide coated metal oxide particles may be used for evaluation.

[0082] [Method for evaluating the degree of silicon dioxide coating] The method for evaluating the degree of silicon dioxide coating in this embodiment includes the steps of: preparing a solution by mixing a dye represented by the above general formula (1) with an organic solvent; preparing metal oxide particles coated with silicon dioxide; evaluating the color x of the solution; preparing a mixed solution A by adding the silicon dioxide-coated metal oxide particles to the solution and evaluating the color a of the mixed solution A; and evaluating the difference between the color x and the color a, and evaluating the amount of metal hydroxyl groups in the metal oxide particles from the obtained evaluation results.

[0083] The evaluation of the above colors x and a may be performed visually, or by measuring physical quantities related to color, such as absorbance.

[0084] This paper describes a method for accurately evaluating the amount of metallic hydroxyl groups on the surface of silicon dioxide-coated metal oxide particles using absorbance. For simplicity, the evaluation method described uses silicon dioxide-coated metal oxide particles as the sample and an orange dye represented by the general formula (3) above, which absorbs light at 457 nm. Furthermore, let n (mol) be the amount of the dye in the above solution, and h (g) be the amount of silicon dioxide-coated metal oxide particles added to the above solution. Also, let S (m²) be the specific surface area of ​​the silicon dioxide-coated metal oxide particles. 2 Let's assume it's / g).

[0085] Using an absorbance meter, measure the absorbance of the above solution at 457 nm, and let the absorbance value be x (color x).

[0086] Adding silicon dioxide-coated metal oxide particles to the above solution and mixing them is required to obtain mixture A. From the viewpoint of enhancing the reaction between the dye and the metal hydroxyl group, heating is preferred during mixing. The heating temperature is preferably such that the organic solvent in the solution does not volatilize; for example, mixing at 40°C to 70°C is preferred. The heating temperature should be adjusted to be lower than the boiling point of the organic solvent. The mixing time should be until the color of the solution stops changing; for example, mixing for 1 to 12 hours is acceptable. The amount of silicon dioxide-coated metal oxide particles added to the above solution is not particularly limited as long as the amount is such that the color change of the solution is easily observable. For example, if the concentration of the above dye is 1 × 10 -3 mol / L ~ 1 × 10 -7 1 mg to 10 mg of the sample may be added to 3 mL to 10 mL of the above solution, which is mol / L.

[0087] The organic solvent is not particularly limited as long as it can dissolve the above-mentioned dye, but examples include methanol, ethanol, propanol, butanol, pentanol, hexanol, toluene, tetrahydrofuran, xylene, hexane, chloroform, benzene, methyl ethyl ketone, methyl isobutyl ketone, acetone, propylene glycol monomethyl ether, ethyl acetate, and butyl acetate. Furthermore, from the viewpoint of the concentration stability of the solution, it is preferable that the organic solvent has a high boiling point. In the method for evaluating the degree of silicon dioxide coating in this embodiment, an organic solvent that readily dissolves the dye may be appropriately selected and used.

[0088] If metal oxide particles coated with silicon dioxide precipitate in mixture A, it is preferable to remove the metal oxide particles to which the dye has been adsorbed from mixture A by centrifugation or filtration, and then evaluate the absorbance of mixture A.

[0089] Using an absorbance meter, measure the absorbance of the above mixture A at 457 nm, and let the absorbance value be a (color a).

[0090] A method for evaluating the difference between the above-mentioned color x and color a, and for evaluating the amount of metallic hydroxyl groups in the above-mentioned sample, will be specifically explained. The absorbance of the above mixture A at 457 nm is measured, and this absorbance value is denoted as a1. The absorbance reduction rate a2 is calculated using the following formula (21). The rate of decrease in absorbance of mixture A is a2 = (x - a1) / x (21) Since the decrease in absorbance is a result of the reaction between the metal hydroxyl group and the dye, the rate of decrease in absorbance a2 can be considered as the adsorption rate of the dye to the metal oxide particles.

[0091] The amount of dye adsorbed per gram of silicon dioxide-coated metal oxide particles, a3 (mol / g), can be calculated using the following formula (22). The amount of dye adsorbed per gram of metal oxide particles coated with silicon oxide a3 (mol / g) = the adsorption rate of the dye to the metal oxide particles coated with silicon oxide × the amount of dye (mol) / the mass of the metal oxide particles coated with silicon oxide (g) = a2 × n (mol) / h (g) (22) Since the above dye and metal hydroxide react in a 1:1 molar ratio, the value calculated from the above formula (22) indicates the amount of metal hydroxide contained per gram of the metal oxide particles coated with silicon oxide.

[0092] When it is desired to exclude the influence of the size of the metal oxide particles coated with silicon oxide, a3 may be divided by the specific surface area S of the metal oxide particles coated with silicon oxide. That is, in the following formula (23), the amount of dye adsorbed per square meter of the metal oxide particles coated with silicon oxide a4 (mol / m 2 ) can be calculated. The amount of dye adsorbed per square meter of the metal oxide particles coated with silicon oxide a4 indicates the amount of metal hydroxide contained per square meter of the metal oxide particles coated with silicon oxide. 2 ) 2 The amount of dye adsorbed per square meter of the metal oxide particles coated with silicon oxide a4 2 indicates the amount of metal hydroxide contained per square meter of the metal oxide particles coated with silicon oxide. The amount of dye adsorbed per square meter of the metal oxide particles coated with silicon oxide a4 (mol / m 2 ) = a3 (mol / g) / S (m 2 / g) (23) 2 / g)

[0093] When it is desired to obtain the amount of metal hydroxide in terms of the number rather than the mole, the results of the above formula (22) or the above formula (23) may be multiplied by Avogadro's number (6.02×10 23 per mol).

[0094] According to the method for evaluating the coating degree of silicon oxide of the present embodiment, the amount of dye adsorbed on the metal oxide particles can be obtained from the change amount of the color of the above solution. Therefore, the amount of metal hydroxide contained in the metal oxide particles coated with silicon oxide can be qualitatively and quantitatively evaluated, and as a result, the coating degree of the metal oxide particles with silicon oxide can be evaluated.

[0095] [Method for evaluating the surface coverage of silicon oxide coatings] (First Embodiment) The method for evaluating the degree of surface coverage of a silicon oxide film according to this embodiment is a method for evaluating the degree of surface coverage of metal oxide particles coated with a silicon oxide film using a dye represented by the above general formula (1), and comprises the steps of: preparing a solution by mixing the dye and an organic solvent; preparing metal oxide particles and silicon oxide coated metal oxide particles obtained by coating the metal oxide particles with a silicon oxide film; preparing a mixed solution A by adding the metal oxide particles to the solution and evaluating the color a of the mixed solution A; preparing a mixed solution B by adding the silicon oxide coated metal oxide particles to the solution and evaluating the color b of the mixed solution B; evaluating the difference between the obtained color a and color b, and evaluating the difference between the amount of metal hydroxyl groups a of the metal oxide particles and the amount of metal hydroxyl groups b of the silicon oxide coated metal oxide particles from the obtained evaluation results.

[0096] The evaluation of the above colors a and b may be performed visually, or by measuring physical quantities related to color, such as absorbance.

[0097] This paper describes a method for accurately evaluating the amount of metallic hydroxyl groups on the surface of metal oxide particles and silicon oxide-coated metal oxide particles using absorbance. For simplicity, the evaluation method described uses an orange dye represented by the general formula (3) above, which absorbs light at 457 nm. Furthermore, let n (mol) be the amount of the dye in the above solution, and h (g) be the amount of metal oxide particles and silicon oxide-coated metal oxide particles added to the above solution. Also, let S (m²) be the specific surface area of ​​the metal oxide particles and silicon oxide-coated metal oxide particles. 2 Let's assume it's / g).

[0098] Using an absorbance meter, measure the absorbance of the above solution at 457 nm, and let the absorbance value be x (color x).

[0099] Metal oxide particles are added to the above solution and mixed to obtain mixture A. From the viewpoint of enhancing the reaction between the dye and the metal hydroxyl group, heating is preferred during mixing. The heating temperature is preferably such that the organic solvent in the solution does not volatilize; for example, mixing at 40°C to 70°C is preferred. The heating temperature should be adjusted to be lower than the boiling point of the organic solvent. The mixing time should be until the color of the solution stops changing; for example, mixing for 1 to 12 hours is acceptable. The amount of metal oxide particles added to the above solution is not particularly limited as long as the amount is such that the color change of the solution is easily observable. For example, if the concentration of the above dye is 1 × 10 -3 mol / L ~ 1 × 10 -7 1 mg to 10 mg of the sample may be added to 3 mL to 10 mL of the above solution, which is mol / L.

[0100] The organic solvent is not particularly limited as long as it can dissolve the above-mentioned dye, but examples include methanol, ethanol, propanol, butanol, pentanol, hexanol, toluene, tetrahydrofuran, xylene, hexane, chloroform, benzene, methyl ethyl ketone, methyl isobutyl ketone, acetone, propylene glycol monomethyl ether, ethyl acetate, and butyl acetate. Furthermore, from the viewpoint of the concentration stability of the solution, it is preferable that the organic solvent has a high boiling point. In the method for evaluating the amount of metal hydroxyl groups in this embodiment, an organic solvent that readily dissolves the dye may be appropriately selected and used.

[0101] If metal oxide particles have precipitated in mixture A, it is preferable to remove the metal oxide particles to which the dye has been adsorbed from mixture A by centrifugation or filtration, and then evaluate the absorbance of mixture A.

[0102] Using an absorbance meter, measure the absorbance of the above mixture A at 457 nm, and let the absorbance value be a (color a).

[0103] Silicon oxide-coated metal oxide particles are added to the above solution and mixed to obtain mixture B. From the viewpoint of enhancing the reaction between the dye and the metal hydroxyl group, heating is preferred during mixing. The heating temperature is preferably such that the organic solvent in the solution does not volatilize; for example, mixing at 40°C to 70°C is preferred. The heating temperature should be adjusted to be lower than the boiling point of the organic solvent. The mixing time should be until the color of the solution stops changing; for example, mixing for 1 to 12 hours is acceptable. The amount of silicon dioxide-coated metal oxide particles added to the above solution is not particularly limited as long as it is an amount that makes the color change of the solution easily noticeable. For example, if the concentration of the above dye is 1 × 10 -3 mol / L ~ 1 × 10 -7 1 mg to 10 mg of the sample may be added to 3 mL to 10 mL of the above solution, which is mol / L.

[0104] As the organic solvent, the same one used in mixture A can be used.

[0105] If silicon dioxide-coated metal oxide particles precipitate in mixture B, it is preferable to remove the silicon dioxide-coated metal oxide particles to which the dye has been adsorbed from mixture A by centrifugation or filtration, and then evaluate the absorbance of mixture B.

[0106] Using an absorbance meter, measure the absorbance of the above mixture B at 457 nm, and define the absorbance value as b (color b).

[0107] This document specifically describes a method for evaluating the difference between the above-mentioned color a and color b, and for evaluating the difference between the amount of metallic hydroxyl groups a in the metal oxide particles and the amount of metallic hydroxyl groups b in the silicon oxide coated metal oxide particles. The absorbance of the above mixture A at 457 nm is measured, and this absorbance value is denoted as a1. The absorbance reduction rate a2 is calculated using the following formula (31). The rate of decrease in absorbance of mixture A is a2 = (x - a1) / x (31) Since the decrease in absorbance is a result of the reaction between the metal hydroxyl group and the dye, the rate of decrease in absorbance a2 can be considered as the adsorption rate of the dye to the metal oxide particles or silicon oxide-coated metal oxide particles.

[0108] The amount of dye adsorbed per gram of metal oxide particles or per gram of silicon oxide-coated metal oxide particles a3 (mol / g) can be calculated using the following formula (32). The amount of dye adsorbed per gram of metal oxide particles or per gram of silicon oxide-coated metal oxide particles a3 (mol / g) = Adsorption rate of dye to metal oxide particles or silicon oxide-coated metal oxide particles × Amount of dye (mol) / Mass of metal oxide particles or silicon oxide-coated metal oxide particles (g) = a2 × n (mol) / h (g) (32) Since the above dye and metal hydroxyl groups react in a 1:1 molar ratio, the value calculated from equation (32) above indicates the amount of metal hydroxyl groups contained per gram of metal oxide particles or per gram of silicon oxide-coated metal oxide particles.

[0109] If you want to eliminate the effect of the size of the metal oxide particles or silicon oxide coated metal oxide particles, you can divide a3 by the specific surface area S of the metal oxide particles or silicon oxide coated metal oxide particles. That is, in the following formula (33), 1 m 2 Per 1 m of silicon dioxide-coated metal oxide particles 2 Adsorption amount of dye per unit a4 (mol / m²) 2 It is possible to calculate the following for metal oxide particles 1m 2 Per 1 m of silicon dioxide-coated metal oxide particles 2 The amount of dye adsorbed per unit area a4 is equal to 1 m of metal oxide particles. 2 Per 1 m of silicon dioxide-coated metal oxide particles 2 This indicates the amount of metallic hydroxyl groups contained in each unit. Metal oxide particles 1m 2 Per 1 m of silicon dioxide-coated metal oxide particles 2 Adsorption amount of dye per unit a4 (mol / m²) 2 ) = a3 (mol / g) / S (m 2 / g) (33)

[0110] If you want to determine the amount of metallic hydroxyl groups in terms of individual units rather than moles, you can use Avogadro's number (6.02 × 10) in the result of equations (32) or (33) above. 23 You may also multiply by (pieces / mol).

[0111] According to the method for evaluating the amount of metallic hydroxyl groups in this embodiment, the amount of dye adsorbed onto the metal oxide particles or silicon oxide-coated metal oxide particles can be determined from the amount of color change of the solution. Therefore, the amount of metallic hydroxyl groups contained in the metal oxide particles or silicon oxide-coated metal oxide particles can be evaluated qualitatively and quantitatively.

[0112] (Second embodiment) The method for evaluating the degree of surface coverage of a silicon oxide film according to this embodiment is a method for evaluating the degree of surface coverage of a silicon oxide film on the surface of metal oxide particles when metal oxide particles are surface-treated with a silicon oxide film, and comprises the steps of: preparing a solution by mixing a dye represented by the above general formula (1) and an organic solvent; preparing metal oxide particles 1 before coating with a silicon oxide film and metal oxide particles 2 after coating the metal oxide particles 1 with a silicon oxide film; and measuring the absorbance x of the solution. The steps are: to prepare a mixed solution A by adding metal oxide particles 1 before coating with the silicon oxide film to the solution and measuring the absorbance a1 of the mixed solution A; to prepare a mixed solution B by adding metal oxide particles 2 after coating with the silicon oxide film to the solution and measuring the absorbance b1 of the mixed solution B; to calculate the rate of decrease a2 of the absorbance of the mixed solution A by subtracting the absorbance a1 from the absorbance x and dividing the result by the absorbance x ((x-a1) / x); and to calculate the rate of decrease a2 of the absorbance of the mixed solution A by subtracting the absorbance a1 from the absorbance x The steps are: to calculate the rate of decrease b2 of the absorbance of the mixed solution B by subtracting a2 and dividing the result by the absorbance x ((x-b1) / x); to calculate the amount of dye adsorbed onto the metal oxide particles 1 a3 (mol / g) by multiplying the rate of decrease a2 of the absorbance by the number of moles of the dye contained in the mixed solution A and dividing by the amount of metal oxide particles 1 added to the solution A (a2 × number of moles of dye contained in the mixed solution A / amount of metal oxide particles 1 added to the solution A); and to calculate the amount of dye adsorbed onto the metal oxide particles 1 a3 (mol / g) by multiplying the rate of decrease a2 of the absorbance by the number of moles of the dye contained in the mixed solution B The method includes the steps of: calculating the amount of adsorption b3 (mol / g) of the dye onto the metal oxide particles 2 by multiplying the number of moles of the dye present and dividing by the amount of the metal oxide particles 2 added to the solution B (b2 × number of moles of dye in the mixed solution B / amount of metal oxide particles 2 added to the solution B); and calculating the degree of surface coverage of the silicon oxide film due to the surface treatment by subtracting from 100 the value obtained by dividing the adsorption amount b3 by the adsorption amount a3 and multiplying the result by 100 (100 - ((b3 / a3) × 100)).

[0113] The method for evaluating the surface coverage of the silicon oxide film in this embodiment will be described in detail. Prepare metal oxide particles 1 before coating with a silicon oxide film. Also, prepare metal oxide particles 2, which are metal oxide particles 1 coated with a silicon oxide film. Metal oxide particles 1 are added to the above solution and stirred to prepare mixture A1. Metal oxide particles 1 are removed from mixture A1 by centrifugation to obtain mixture A2 for evaluation. Furthermore, metal oxide particles 2 are added to the above solution and stirred to prepare mixed solution B1. The metal oxide particles 2 are removed from mixed solution B1 by centrifugation to obtain mixed solution B2 for evaluation.

[0114] Measure the absorbance of mixture A2 and mixture B2. When evaluating using the orange dye represented by general formula (3), measure the absorbance at a wavelength of 457 nm.

[0115] Calculate the percentage decrease in absorbance between mixture A2 and mixture B2. The rate of decrease in absorbance of mixture A2, a2 ​​= the adsorption rate of the dye to the metal oxide particles 1 contained in mixture A2 = (absorbance of the above solution x - absorbance of mixture A2 a1) / absorbance of the above solution x ((x-a1) / x) The rate of decrease in absorbance of mixture B2, b2 = the adsorption rate of the dye to the metal oxide particles 2 contained in mixture B2 = (absorbance of the above solution x - absorbance of mixture B2 b1) / absorbance of the above solution x ((x-b1) / x) A decrease in absorbance at 457 nm for orange pigment indicates that the pigment is adsorbed; therefore, the percentage decrease in absorbance can be converted to the percentage of pigment adsorption.

[0116] Calculate the amount of dye adsorbed per gram of particles in mixture A (a3, mol / g) and the amount of dye adsorbed per gram of particles in mixture B (b3, mol / g). The amount of dye adsorbed onto metal oxide particles 1 a3 (mol / g) = Adsorption rate of dye onto metal oxide particles 1 (decrease in absorbance of mixture A2 a2) × Amount of dye (mol) / Mass of metal oxide particles 1 (g) The amount of dye adsorbed onto metal oxide particles 2, b3 (mol / g), is calculated as follows: Adsorption rate of dye onto metal oxide particles 2 (decrease in absorbance of mixture B2, b) × Amount of dye (mol) / Mass of metal oxide particles 2 (g)

[0117] Note that the amount of adsorbed pigment (mol / g) is calculated using Avogadro's number (6.02 × 10⁻¹⁰). 23 You can also convert this to the amount of dye adsorbed (particles / g) by multiplying by the number of particles / mol. Furthermore, by dividing the amount of adsorbed pigment (particles / g) by the specific surface area of ​​the metal oxide particles, the amount of adsorbed pigment per unit area of ​​the metal oxide particles (particles / m²) can be calculated. 2 You may calculate ).

[0118] The dye in this embodiment reacts with the metal hydroxyl groups present on the surface of the metal oxide particles in a 1:1 ratio. Therefore, the amount of dye adsorbed (mol / g) represents the amount of metal hydroxyl groups present on the surface of metal oxide particle 1 or metal oxide particle 2, i.e., the amount of untreated (uncoated) metal hydroxyl groups that are not covered by the silicon oxide film (mol / g). Therefore, the amount of untreated metal hydroxyl groups in metal oxide particle 1 (mol / g) = the amount of dye adsorbed by metal oxide particle 1 (mol / g). Furthermore, the amount of untreated metal hydroxyl groups in metal oxide particle 2 (mol / g) equals the amount of dye adsorbed by metal oxide particle 2 (mol / g).

[0119] Next, the degree of surface coverage of the silicon oxide film is calculated using the following method. Surface coverage percentage of silicon oxide film = (100 - ((b3 / a3) × 100)) The higher the value of the silicon oxide film's surface coverage, the more the metal oxide particles are covered by the silicon oxide film.

[0120] According to the method for evaluating the surface coverage of the silicon oxide film of this embodiment, it is possible to quantitatively evaluate the extent to which the metal hydroxyl groups on the surface of the metal oxide particles have been surface-treated by the surface treatment agent.

[0121] (Third embodiment) The method for evaluating the surface coverage of a silicon oxide film according to this embodiment is a method for evaluating the surface coverage of a silicon oxide film on the surface of metal oxide particles when metal oxide particles are surface-treated with a silicon oxide film, and comprises the steps of: preparing a solution by mixing a dye represented by the above general formula (1) and an organic solvent; preparing metal oxide particles 1 before surface treatment and metal oxide particles 2 after surface treatment obtained by surface-treating the metal oxide particles 1; measuring the absorbance x of the solution; preparing a mixed solution A by adding the metal oxide particles 1 before surface treatment to the solution and measuring the absorbance a1 of the mixed solution A; preparing a mixed solution B by adding the metal oxide particles 2 after surface treatment to the solution and measuring the absorbance b1 of the mixed solution B; calculating the rate of decrease a2 of the absorbance of the mixed solution A by dividing the value obtained by subtracting the absorbance a1 from the absorbance x by the absorbance x ((x-a1) / x); and the absorbance The steps are as follows: calculate the rate of decrease b2 in the absorbance of the mixture B by subtracting the absorbance b1 from the degree x and dividing the result by the absorbance x ((x-b1) / x); and calculate the amount of dye adsorbed onto the metal oxide particles 1 a3 (mol / g) by multiplying the rate of decrease a2 in absorbance by the number of moles of the dye contained in the mixture A and dividing by the amount of metal oxide particles 1 added to the solution A (a2 × number of moles of dye contained in the mixture A / amount of metal oxide particles 1 added to the solution A). The method includes the steps of: dispensing; calculating the amount of dye adsorbed onto the metal oxide particles 2 b3 (mol / g) by multiplying the rate of decrease in absorbance b2 by the number of moles of the dye contained in the mixed solution B and dividing by the amount of metal oxide particles 2 added to the solution B (b2 × number of moles of dye contained in the mixed solution B / amount of metal oxide particles 2 added to the solution B); and calculating the degree of uncoated silicon oxide film using the value obtained by dividing the adsorbed amount b3 by the adsorbed amount a3.

[0122] In the third embodiment, the method for evaluating the degree of coverage of the silicon oxide coating is to replace the calculation formula (100-((b3 / a3)×100)) in the second embodiment with b3 / a3 or b3 / a3×100, thereby calculating the degree of uncovered surface of the metal oxide particles in the silicon oxide coating.

[0123] According to the method for evaluating the degree of surface coverage of the silicon oxide film of this embodiment, it is possible to quantitatively evaluate to what extent the surface of metal oxide particles is covered by the silicon oxide film, or not covered at all. [Examples]

[0124] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the following examples.

[0125] [Manufacturing Example 1] (Ligand preparation) 4-bromo-2-hydroxybenzaldehyde and 2-amino-5-bromophenol were mixed in a molar ratio of 1:1 and dissolved in 100 mL of ethanol to prepare the mixture. Next, this mixture was stirred at 100°C for 12 hours to carry out a dehydration reaction, yielding a mixture containing 4,4'-dibromo-bromo-2,2'-dihydroxyazobenzene, which is a ligand for the orange pigment. Next, the mixture after the dehydration reaction was cooled to 5°C to precipitate 4,4'-dibromo-2,2'-dihydroxyazobenzene, and then the mixture was dried to recover 4,4'-dibromo-2,2'-dihydroxyazobenzene.

[0126] (Preparation of orange pigment) A mixture was prepared by mixing 1 mmol of 4,4'-dibromo-2,2'-dihydroxyazobenzene as a ligand, 1 mmol of diphenyl tin(IV) oxide as a metal source, and 30 mL of acetone. Next, this mixture was stirred at 70°C for 3 hours to carry out a dehydration reaction and coordinate the metal source to the ligand. The mixture after the dehydration reaction was filtered, the filtrate was collected, and the solvent was removed from the filtrate to obtain the dye represented by the following formula (9) (Tin,[4-bromo-2-[[[2-(hydroxy-κO)-4-bromophenyl]imino-κN]methyl]phenolato(2-)-κO]diphenyl-,(TB-5-12)-(9CI,ACI)) in Production Example 1. Visual inspection of the obtained dye revealed that the dye was orange.

[0127] [ka]

[0128] (Preparation of a solution containing orange pigment) Dissolving 250 nmol (0.16 mg) of the orange pigment from Production Example 1 in toluene to make 5 mL yields 5 × 10⁻¹⁰ of Production Example 1. -5 A mol / L solution was obtained. Visual inspection of the solution revealed that it was orange.

[0129] [Example 1] (Preparation of evaluation samples) The following samples were prepared for measurement. • Silicon oxide particles (specific surface area 35 m²) 2 / g, manufactured by Nippon Aerosil Co., Ltd., Aerosil 50) • Zinc oxide particles 1 (specific surface area 40 m²) 2 (manufactured by Sumitomo Osaka Cement Co., Ltd.) • Silicon oxide coated zinc oxide particles 2 (A silica coating is formed by coating 100 parts by mass of zinc oxide particles with 20 parts by mass of sodium silicate, equivalent to silica.) • Silicon oxide-coated zinc oxide particles 3 (a silica coating formed by applying 35 parts by mass of tetraethoxysilane (equivalent to silica) to 100 parts by mass of surface-treated zinc oxide particles 2) To the solution containing orange pigment from Production Example 1, 10 mg of silicon dioxide particles was added and the mixture was stirred at 60°C for 4 hours to prepare mixed solution X1. Silicon dioxide particles were removed from mixture X1 by centrifugation to obtain mixture X2 for evaluation. To the solution containing the orange pigment from Production Example 1, 4 mg of zinc oxide particles 1 were added and the mixture was stirred at 60°C for 4 hours to prepare mixture A1. Zinc oxide particles 1 were removed from mixture A1 by centrifugation to obtain mixture A2 for evaluation. To the solution containing the orange pigment from Production Example 1, 4 mg of silicon dioxide-coated zinc oxide particles 2 were added and the mixture was stirred at 60°C for 4 hours to prepare mixture B1. The silicon dioxide-coated zinc oxide particles 2 were removed from mixture B1 by centrifugation to obtain mixture B2 for evaluation. To the solution containing the orange pigment from Production Example 1, 4 mg of silicon dioxide-coated zinc oxide particles 3 were added and the mixture was stirred at 60°C for 4 hours to prepare mixture C1. The silicon dioxide-coated zinc oxide particles 3 were removed from mixture C1 by centrifugation to obtain mixture C2 for evaluation.

[0130] The absorbance at 457 nm of the solution containing the orange pigment from Production Example 1, mixture X2, mixture A2, mixture B2 of silicon dioxide-coated zinc oxide particles 2, and mixture C2 of silicon dioxide-coated zinc oxide particles 3 were measured using a spectrophotometer (model: V-770, manufactured by JASCO Corporation). As a result, the absorbance of the solution from Production Example 1 was 0.730, the absorbance of the mixture X2 was 0.718, the absorbance of mixture A2 was 0.361, the absorbance of mixture B2 of surface-treated zinc oxide particles 2 was 0.589, and the absorbance of mixture C2 of surface-treated zinc oxide particles 3 was 0.692. The results are shown in Table 1. The percentage decrease in absorbance for each of the following was calculated: Mixture X2, Mixture A2, Mixture B2, and Mixture C2. The rate of decrease in absorbance of mixture X2 = the adsorption rate of the dye to the silicon dioxide particles contained in mixture X2 = (absorbance of solution from manufacturing example 1 - absorbance of mixture X2) / absorbance of solution from manufacturing example 1 = 0.016 The rate of decrease in absorbance of mixture A2 = the adsorption rate of the dye to zinc oxide particles 1 contained in mixture A2 = (absorbance of solution in manufacturing example 1 - absorbance of mixture A2) / absorbance of solution in manufacturing example 1 = 0.505 The rate of decrease in absorbance of mixture B2 containing silicon dioxide-coated zinc oxide particles 2 = the adsorption rate of the dye to silicon dioxide-coated zinc oxide particles 2 contained in mixture B2 = (absorbance of solution in manufacturing example 1 - absorbance of mixture B2) / absorbance of solution in manufacturing example 1 = 0.193 The rate of decrease in absorbance of the mixture C2 containing silicon dioxide-coated zinc oxide particles 3 = the adsorption rate of the dye to the silicon dioxide-coated zinc oxide particles 3 contained in the mixture C2 = (absorbance of the solution in production example 1 - absorbance of the mixture C2) / absorbance of the solution in production example 1 = 0.052 A decrease in absorbance at 457 nm for orange pigment indicates that the pigment is adsorbed; therefore, the percentage decrease in absorbance can be converted to the percentage of pigment adsorption. The amount of dye adsorbed per gram of particles (mol / g) contained in each of the following mixtures was calculated: Mixture X2, Mixture A2, Mixture B2, and Mixture C2. The amount of dye adsorbed per gram of silicon dioxide particles (mol / g) = Adsorption rate of dye to silicon dioxide particles × Amount of dye (mol) / Mass of silicon dioxide particles (g) = 0.016 × 2.5 × 10 -7 (mol) / 0.01(g) = 4.10 × 10 -7 (mol / g) Similarly, the amount of dye adsorbed per gram of zinc oxide particles (mol / g) is 3.16 × 10⁻⁶. -5 (mol / g), the amount of dye adsorbed per gram of silicon dioxide-coated zinc oxide particles 2 (mol / g) is 1.21 × 10⁻⁶ -5 (mol / g), the amount of dye adsorbed per gram of silicon dioxide-coated zinc oxide particles 3 (mol / g) is 3.26 × 10⁻⁶ -6 It was (mol / g).

[0131] The orange pigment in Production Example 1 reacts in a 1:1 ratio with the metallic hydroxyl groups present on the surface of the zinc oxide particles. Therefore, the amount of adsorbed orange pigment (mol / g) represents the amount of metallic hydroxyl groups present on the surface of zinc oxide particle 1, silicon oxide-coated zinc oxide particle 2, or silicon oxide-coated zinc oxide particle 3, i.e., the amount of metallic hydroxyl groups not coated by the silicon oxide film (mol / g). Therefore, the amount of uncoated metal hydroxyl groups on zinc oxide particle 1 (mol / g) = the amount of dye adsorbed on zinc oxide particle 1 (mol / g) = 3.16 × 10 -5 This is expressed as (mol / g). Furthermore, the amount of uncoated metal hydroxyl groups in silicon oxide-coated zinc oxide particle 2 (mol / g) equals the amount of dye adsorbed by silicon oxide-coated zinc oxide particle 2 (mol / g), and the amount of uncoated metal hydroxyl groups in silicon oxide-coated zinc oxide particle 3 (mol / g) equals the amount of dye adsorbed by silicon oxide-coated zinc oxide particle 3 (mol / g). The orange pigment in Production Example 1 does not react in a 1:1 ratio with the metal hydroxyl groups present on the surface of the silicon dioxide particles. Therefore, the adsorption amount (mol / g) of the orange pigment can be used as an indicator to check the degree of adsorption to the metal hydroxyl groups present on the surface of the silicon dioxide particles. In other words, the larger the adsorption amount (mol / g) of the orange pigment, the more easily the orange pigment is adsorbed to the metal hydroxyl groups present on the surface of the silicon dioxide particles. The adsorption amount of orange pigment (mol / g) is Avogadro's number 6.02 × 10⁻¹⁰ 23 The amount of orange pigment adsorbed per gram (particles / g) was calculated by multiplying by the specific surface area (m²). The results are shown in Table 1. Furthermore, the amount of orange pigment adsorbed (particles / g) was multiplied by the specific surface area (m²). 2 Divide by ( / g) to find the amount of orange pigment adsorbed (particles / nm) 2 The result was calculated. The results are shown in Table 1. Next, the coverage rate (surface treatment rate) of zinc oxide particles by the silicon oxide coating was calculated using the following calculation. Coverage rate of silicon oxide film on zinc oxide particle 1 (%) = 100 - (Amount of untreated metal hydroxyl groups on zinc oxide particle 1 (mol / g) / Amount of untreated metal hydroxyl groups on zinc oxide particle 1 (mol / g) × 100) = 0 Coverage rate of silicon oxide film on surface-treated zinc oxide particles 2 (%) = 100 - (Amount of untreated metal hydroxyl groups on surface-treated zinc oxide particles 2 (mol / g) / Amount of untreated metal hydroxyl groups on zinc oxide particles 1 (mol / g) × 100) = 61.8% The coverage rate of the silicon oxide coating on silicon oxide-coated zinc oxide particle 3 (%) = 100 - (Amount of untreated metal hydroxyl groups on silicon oxide-coated zinc oxide particle 3 (mol / g) / Amount of untreated metal hydroxyl groups on zinc oxide particle 1 (mol / g) × 100) = 89.7% The higher the coverage rate of the silicon oxide film, the more the zinc oxide particles are coated with the silicon oxide film.

[0132] [Manufacturing Example 2] (Production of yellow pigment) Except for using σ-salicylideneaminophenol as a ligand, the same procedure as in Production Example 1 was followed to obtain the dye shown in the following formula (10) (Tin,[2-[[[2-(hydroxy-κO)phenyl]imino-κN]methyl]phenolato(2-)-κO]diphenyl-,(TB-5-12)-(9CI,ACI)) in Production Example 2. Visual inspection of the obtained dye revealed that the color was a deep yellow.

[0133] [ka]

[0134] (Preparation of a solution containing yellow pigment) Dissolving 250 nmol (0.12 mg) of the yellow dye from Production Example 2 in toluene to make 5 mL yields 5 × 10⁻¹⁰ of Production Example 2. -5 A mol / L solution was obtained. Visual inspection of the solution revealed that it was yellow.

[0135] [Example 2] The evaluation samples were performed in the same manner as in Example 1, except that the yellow pigment from Production Example 2 was used instead of the orange pigment from Production Example 1, and the absorbance at a wavelength of 454 nm was measured instead of 457 nm. The results are shown in Table 2.

[0136] [Manufacturing Example 3] (Production of red pigment) Except for using 2,2'-dihydroxyazobenzene as the ligand, the dye shown in formula (11) below was obtained in the same manner as in Production Example 1. Visual inspection of the obtained dye revealed that the color of the dye was red.

[0137] [ka]

[0138] (Preparation of a solution containing red pigment) By dissolving 250 nmol (0.12 mg) of the red dye from Production Example 3 in toluene to a volume of 5 mL, 5 × 10⁻¹⁰ of Production Example 3 is obtained. -5 A mol / L solution was obtained. Visual inspection of the solution revealed that it was red.

[0139] [Comparative Example] The evaluation samples were performed in the same manner as in Example 1, except that the red dye from Production Example 3 was used instead of the orange dye from Production Example 1, and the absorbance at a wavelength of 545 nm was measured instead of 457 nm. The results are shown in Table 3.

[0140] [Table 1]

[0141] [Table 2]

[0142] [Table 3]

[0143] [result] To evaluate the degree of coating of zinc oxide particles in silicon oxide-coated zinc oxide particles, it is preferable to use a dye that readily adsorbs to the hydroxyl groups on the surface of the zinc oxide particles but does not adsorb to the hydroxyl groups on the surface of the silicon oxide coating. The orange and yellow pigments are not easily adsorbed by silica particles but are easily adsorbed by zinc oxide particles 1. Therefore, it was confirmed that they are ideal for evaluating the extent to which zinc oxide particles are coated by the silicon oxide film in silicon oxide-coated zinc oxide particles. [Industrial applicability]

[0144] The present invention provides a dye that selectively adsorbs to metal hydroxyl groups contained in silicon oxide-coated metal oxide particles, does not react with hydroxyl groups of water or alcohol, and is less reactive with silanol groups of the silicon oxide coating. The dye of the present invention allows for easy evaluation of the amount of metal hydroxyl groups contained in silicon oxide-coated metal oxide particles (the amount of metal hydroxyl groups not coated by the silicon oxide coating). Therefore, the industrial value of using the dye of the present invention as a diagnostic agent is significant.

Claims

1. A dye represented by the following general formula (1), used to evaluate the degree of surface coverage of metal oxide particles coated with a silicon oxide film. 【Chemistry 1】 (However, M is Sn or Ge, R1 is an alkyl group or a phenyl group, Y1 and Y2 are hydrogen, a halogen group, a methyl group, an alkoxy group, a phenyl group, a diphenylamide group, a thiophenyl group, or a phenylethynyl group, and Z is a single bond or represented by the following formula (2).) 【Chemistry 2】 (However, R2 is an alkyl group or a phenyl group.)

2. The process involves a step of preparing a solution by mixing a dye represented by the following general formula (1) with an organic solvent, The steps include: preparing metal oxide particles coated with a silicon oxide film, A step of evaluating the color x of the solution, The steps include: adding metal oxide particles coated with the silicon oxide film to the aforementioned solution to prepare a mixture A, and evaluating the color a of the mixture A; A method for evaluating the surface coverage of a silicon oxide film, comprising the steps of evaluating the difference between the aforementioned color x and the aforementioned color a, and evaluating the amount of metal hydroxyl groups of the metal oxide particles from the evaluation results obtained. 【Transformation 3】 (However, M is Sn or Ge, R1 is an alkyl group or a phenyl group, Y1 and Y2 are hydrogen, a halogen group, a methyl group, an alkoxy group, a phenyl group, a diphenylamide group, a thiophenyl group, or a phenylethynyl group, and Z is a single bond or represented by the following formula (2).) 【Chemistry 4】 (However, R2 is an alkyl group or a phenyl group.)

3. A method for evaluating the degree of surface coverage of metal oxide particles coated with a silicon oxide film, using a dye represented by the following general formula (1): The steps include: mixing the aforementioned dye with an organic solvent to prepare a solution; The steps include: preparing metal oxide particles and silicon oxide-coated metal oxide particles obtained by coating the metal oxide particles with a silicon oxide film; The steps include: adding the metal oxide particles to the solution to prepare a mixture A, and evaluating the color a of the mixture A; The steps include: adding the silicon oxide-coated metal oxide particles to the aforementioned solution to prepare a mixture B, and evaluating the color b of the mixture B; A method for evaluating the surface coverage of a silicon oxide coating, comprising the steps of: evaluating the difference between the obtained color a and the obtained color b; and evaluating the difference between the amount of metal hydroxyl groups a of the metal oxide particles and the amount of metal hydroxyl groups b of the silicon oxide coated metal oxide particles from the obtained evaluation results. 【Transformation 5】 (However, M is Sn or Ge, R1 is an alkyl group or a phenyl group, Y1 and Y2 are hydrogen, a halogen group, a methyl group, an alkoxy group, a phenyl group, a diphenylamide group, a thiophenyl group, or a phenylethynyl group, and Z is a single bond or represented by the following formula (2).) 【Transformation 6】 (However, R2 is an alkyl group or a phenyl group.)

4. A method for comparing and evaluating the degree of surface coverage of metal oxide particles 1 coated with a silicon oxide film and metal oxide particles 2 coated with a silicon oxide film, using a dye represented by the following general formula (1): The steps include: mixing the aforementioned dye with an organic solvent to prepare a solution; The steps include preparing metal oxide particles 1 coated with a silicon oxide film and metal oxide particles 2 coated with a silicon oxide film, A step of evaluating the color x of the solution, The steps include: adding the metal oxide particles 1 to the solution to prepare a mixture A, and evaluating the color a1 of the mixture A; The steps include: adding the metal oxide particles 2 to the solution to prepare a mixture B, and evaluating the color b1 of the mixture B; The steps include evaluating the difference between the obtained color x and the obtained color a1, and evaluating the amount of metal hydroxyl groups a of the metal oxide particles 1 from the obtained evaluation results, The steps include evaluating the difference between the obtained color x and color b1, and evaluating the amount of metal hydroxyl groups b of the metal oxide particles 2 from the obtained evaluation results, A method for comparing and evaluating the degree of surface coverage of metal oxide particles coated with a silicon oxide film, comprising the step of evaluating the difference between the amount of metal hydroxyl groups a and the amount of metal hydroxyl groups b. 【Transformation 7】 (However, M is Sn or Ge, R1 is an alkyl group or a phenyl group, Y1 and Y2 are hydrogen, a halogen group, a methyl group, an alkoxy group, a phenyl group, a diphenylamide group, a thiophenyl group, or a phenylethynyl group, and Z is a single bond or represented by the following formula (2).) 【Transformation 8】 (However, R2 is an alkyl group or a phenyl group.)

5. A method for evaluating the degree of surface coverage of metal oxide particles by a silicon oxide coating when metal oxide particles are surface-treated with a silicon oxide coating, The process involves a step of preparing a solution by mixing a dye represented by the following general formula (1) with an organic solvent, The process involves preparing metal oxide particles 1 before surface treatment and metal oxide particles 2 after surface treatment, The steps include measuring the absorbance x of the aforementioned solution, The steps include: adding the metal oxide particles 1 before surface treatment to the solution to prepare a mixed solution A, and measuring the absorbance a1 of the mixed solution A; The steps include: adding the surface-treated metal oxide particles 2 to the solution to prepare a mixture B, and measuring the absorbance b1 of the mixture B; The steps include: calculating the rate of decrease a2 in the absorbance of the mixed solution A by dividing the value obtained by subtracting the absorbance a1 from the absorbance x by the absorbance x ((x-a1) / x); The steps include: calculating the rate of decrease b2 in the absorbance of the mixed solution B by dividing the value obtained by subtracting the absorbance b1 from the absorbance x by the absorbance x ((x - b1) / x); The steps include: calculating the amount of dye adsorbed onto the metal oxide particles 1 a3 (mol / g) by multiplying the absorbance reduction rate a2 by the number of moles of the dye contained in the mixed solution A and dividing by the amount of metal oxide particles 1 added to the solution A (a2 × number of moles of dye contained in the mixed solution A / amount of metal oxide particles 1 added to the solution A); The steps include: calculating the amount of dye adsorbed onto the metal oxide particles 2 b3 (mol / g) by multiplying the absorbance reduction rate b2 by the number of moles of the dye contained in the mixed solution B and dividing by the amount of metal oxide particles 2 added to the solution B (b2 × number of moles of dye contained in the mixed solution B / amount of metal oxide particles 2 added to the solution B); A method for evaluating the surface coverage degree of a silicon oxide film, comprising the step of calculating the surface coverage degree of the silicon oxide film due to the surface treatment by subtracting from 100 the value obtained by dividing the adsorption amount b3 by the adsorption amount a3 and multiplying the result by 100 (100 - ((b3 / a3) × 100)). 【Chemistry 9】 (However, M is Sn or Ge, R1 is an alkyl group or a phenyl group, Y1 and Y2 are hydrogen, a halogen group, a methyl group, an alkoxy group, a phenyl group, a diphenylamide group, a thiophenyl group, or a phenylethynyl group, and Z is a single bond or represented by the following formula (2).) 【Chemistry 10】 (However, R2 is an alkyl group or a phenyl group.)

6. A method for evaluating the degree of surface coverage of metal oxide particles by a silicon oxide coating when metal oxide particles are surface-treated with a silicon oxide coating, The process involves a step of preparing a solution by mixing a dye represented by the following general formula (1) with an organic solvent, The process involves preparing metal oxide particles 1 before surface treatment and metal oxide particles 2 after surface treatment, The steps include measuring the absorbance x of the aforementioned solution, The steps include: adding the metal oxide particles 1 before surface treatment to the solution to prepare a mixed solution A, and measuring the absorbance a1 of the mixed solution A; The steps include: adding the surface-treated metal oxide particles 2 to the solution to prepare a mixture B, and measuring the absorbance b1 of the mixture B; The steps include: calculating the rate of decrease a2 in the absorbance of the mixed solution A by dividing the value obtained by subtracting the absorbance a1 from the absorbance x by the absorbance x ((x-a1) / x); The steps include: calculating the rate of decrease b2 in the absorbance of the mixed solution B by dividing the value obtained by subtracting the absorbance b1 from the absorbance x by the absorbance x ((x - b1) / x); The steps include: calculating the amount of dye adsorbed onto the metal oxide particles 1 a3 (mol / g) by multiplying the absorbance reduction rate a2 by the number of moles of the dye contained in the mixed solution A and dividing by the amount of metal oxide particles 1 added to the solution A (a2 × number of moles of dye contained in the mixed solution A / amount of metal oxide particles 1 added to the solution A); The steps include: calculating the amount of dye adsorbed onto the metal oxide particles 2 b3 (mol / g) by multiplying the absorbance reduction rate b2 by the number of moles of the dye contained in the mixed solution B and dividing by the amount of metal oxide particles 2 added to the solution B (b2 × number of moles of dye contained in the mixed solution B / amount of metal oxide particles 2 added to the solution B); A method for evaluating the surface coverage of a silicon oxide film, comprising the step of calculating the degree of uncovered silicon oxide film using the value obtained by dividing the adsorption amount b3 by the adsorption amount a3. 【Chemistry 11】 (However, M is Sn or Ge, R1 is an alkyl group or a phenyl group, Y1 and Y2 are hydrogen, a halogen group, a methyl group, an alkoxy group, a phenyl group, a diphenylamide group, a thiophenyl group, or a phenylethynyl group, and Z is a single bond or represented by the following formula (2).) 【Chemistry 12】 (However, R2 is an alkyl group or a phenyl group.)

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