Method for producing a coated article

Abstract

To provide a paint color material that exhibits novel coloration by means of a structural color and a pigment color.SOLUTION: The present invention provides a paint color material applied to a support. The paint color material has a core part and a pigment layer including ferric tannate formed around the core part. The paint color material contains particles having a particle diameter corresponding to the wavelength of a structural color, exhibits coloration by means of the structural color and the pigment layer, and allows the coloration to be adjusted depending on the painting thickness.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] This disclosure relates to colorants for paints and methods for manufacturing coated products. [Background technology]

[0002] Regarding colorants for paints, colorants that exhibit structural color, which differs from pigment color due to light absorption, are known. Structural color is a color produced by the interference and scattering of visible light due to the structure of the colorant. Therefore, colorants that exhibit structural color have the advantage of being less susceptible to fading due to sunlight compared to general organic pigments and dyes, and having a lower environmental impact compared to general organic and inorganic pigments. For example, Patent Document 1 discloses a composition containing particles having a core-shell structure that can form a film exhibiting structural color. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2014-47231 [Overview of the project] [Problems that the invention aims to solve]

[0004] As described above, structural color has various advantages. Therefore, there has been a need for technology that can obtain novel and unprecedented colors using structural color. [Means for solving the problem]

[0005] This disclosure can be implemented in the following forms:

[0006] (1) According to a first embodiment of the present disclosure, a colorant for coating a support is provided. The colorant for coating comprises a core portion and a pigment layer containing iron tannate formed around the core portion, and contains particles having a particle size corresponding to the wavelength of the structural color, exhibits color development due to the pigment layer and the structural color, and the color development is adjustable by the coating thickness. With this configuration, in a paint colorant, the intensity ratio between the reflected light of the structural color and the reflected light of the pigment layer can be changed by varying the application thickness, thereby arbitrarily altering the color development. As a result, the paint colorant exhibits novel color development that can be adjusted by the application thickness. (2) In the above embodiment, the color development may be characterized in that it can be adjusted not only by the coating thickness but also by the water absorption of the support. With such an embodiment, the colorant for paint exhibits a novel color development in which the color development can be adjusted not only by the coating thickness but also by the water absorption of the support. (3) A second embodiment of the present disclosure provides a method for manufacturing a coating. This manufacturing method comprises the steps of: applying a coating to a support, the coating having a core portion and a pigment layer containing iron tannate formed around the core portion, and containing particles having a particle size corresponding to the wavelength of the structural color; and adjusting the thickness of the coating on the support to adjust the color development by the pigment layer and the structural color. This embodiment makes it possible to manufacture a coating exhibiting novel colors, in which the color development is adjusted by the coating thickness of the colorant for the coating. [Brief explanation of the drawing]

[0007] [Figure 1] A diagram showing an example of a method for manufacturing colorants for paints. [Figure 2] A diagram showing an example of a method for additionally forming a pigment layer in paint colorants. [Figure 3] A process diagram showing an example of a method for manufacturing a coated material. [Figure 4] A diagram showing the coated material prepared as a sample in the experiment. [Figure 5] A figure showing the reflectance spectra of Sample 1 and Sample 6. [Figure 6]This figure shows the relationship between coating thickness and reflected light intensity ratio in Sample 1. [Figure 7] A figure showing the reflectance spectrum of sample 4. [Figure 8] This figure shows the relationship between coating thickness and reflected light intensity ratio in Sample 4. [Figure 9] A figure showing the reflectance spectrum of sample 5. [Figure 10] This figure shows the relationship between coating thickness and reflected light intensity ratio in Sample 5. [Modes for carrying out the invention]

[0008] A. Embodiments: The paint colorant disclosed herein comprises a core portion and a pigment layer containing iron tannate formed around the core portion, and contains particles having a particle size corresponding to the wavelength of the structural color. The paint colorant exhibits color due to the pigment layer and structural color. Structural color is a color produced by the interference and scattering of visible light due to the structure of the colorant. Therefore, colorants exhibiting structural color are less susceptible to fading due to sunlight compared to general organic pigments and dyes.

[0009] The colorants for paints disclosed herein allow for arbitrary changes in color development by altering the intensity ratio between the reflected light of the structural color and the reflected light of the pigment layer, thereby changing the coating thickness when the colorant is applied to a support. In other words, the color development of the colorant can be adjusted by the coating thickness. As a result, even when using the same colorant, the color development can be made different depending on the coating thickness. For example, by changing the coating method or the tools used for coating, and thus changing the coating thickness of the colorant, it is possible to easily enjoy the differences in color development of the colorant.

[0010] The particles contained in the colorant for the coating have a so-called core-shell shape with a pigment layer as the shell part. That is, the particle is formed by integrating the core part and the pigment layer formed around the core part. Hereinafter, the particle in which the pigment layer is formed around the core part in the present embodiment is also referred to as a colorant particle. In the present embodiment, silica particles formed into spherical shapes with uniform particle diameters are used as the core part. As the core part, it is preferable to use a transparent or translucent material having a low Haze value. The Haze value is an index indicating the degree of cloudiness of a material and can be measured based on JIS K7136.

[0011] The pigment layer contains iron tannate and exhibits a pigment color resulting from iron tannate. The pigment color is a color that occurs when light in a certain wavelength region is absorbed in a substance and the light in the wavelength region that is not absorbed is reflected. General organic or inorganic pigments, dyes, etc. exhibit this pigment color. It is known that iron tannate can be produced, for example, by the reaction of an iron salt such as iron(III) chloride and tannic acid. Also, it is known that iron tannate exhibits different colors depending on its liquidity. Specifically, iron tannate dimerizes and exhibits a blue-violet color under the condition of pH 3.0 to 6.0, and trimerizes and exhibits a reddish-brown or reddish-violet color under the condition of pH 7.0 or higher.

[0012] As described above, the colorant particles have a particle diameter corresponding to the wavelength of the structural color. For example, when the colorant for the coating is applied to a support, the colorant particles are arranged periodically on the support. The colorant for the coating exhibits a structural color with a wavelength corresponding to the particle diameter of the colorant particles due to the arrangement of these colorant particles. For example, when a colloidal crystal of a face-centered cubic lattice is formed by the arrangement of the colorant particles, the wavelength λ of the structural color, the average refractive index n a of the colloidal crystal, and the particle diameter D of the colorant particles satisfy the following relationship of formula (1). λ = 1.633n a D … (1) The average refractive index n a is the refractive index n i of the component i constituting the colloidal crystal and the volume fraction Φ iIt is determined by the following formula (2). n a 2 =Σn i 2 Φ i … (2) In the following, the state where the coloring material for paint is applied to the support is also referred to as the "applied state".

[0013] The particle size of the coloring material particles is determined by the size of the core part and the thickness of the pigment layer. For example, in the present embodiment, the particle size of the coloring material particles is the total value of the particle size of the silica particles constituting the core part and the thickness of the pigment layer. Therefore, by adjusting the diameter of the core part and the thickness of the pigment layer, the particle size of the coloring material particles can be adjusted, and a desired structural color can be exhibited in the applied state.

[0014] When the coloring material for paint exhibits a structural color due to the arrangement of the coloring material particles as in the present embodiment, the period of the structure of the part that exhibits the structural color becomes short, and the angle dependence of the color development of the coloring material becomes low. On the other hand, for example, when the coloring material exhibits a structural color by a part formed in a thin film shape or a multilayer film shape having a uniform film, the period of the structure of the part that exhibits the structural color becomes long. In this case, since the structure of the part that exhibits the structural color is close to a so-called thin film interference model or a multilayer film interference model, the angle dependence of the coloring material becomes high. When the angle dependence of the coloring material is high, the color of the coloring material is likely to be visually recognized as different depending on the angle at which the coloring material is viewed and the irradiation direction of light to the coloring material.

[0015] The coloring material for paint is used by being applied to a support. As the support, for example, various materials and shapes such as glass materials, ceramic materials, metal materials, resin materials, paper, and cloth can be used.

[0016] In addition to the coating thickness, the color development of the coloring material for paint may be adjustable depending on the water absorption of the support to which the coloring material for paint is applied. The water absorption of the support may be adjusted, for example, depending on the material of the support, or may be adjusted by applying a treatment such as coating to the support.

[0017] Figure 1 shows an example of a method for manufacturing a paint colorant according to this embodiment. In this manufacturing method, first, in step S110, a first liquid and a second liquid are prepared. The first liquid is a suspension in which particles such as silica that form the core are suspended in a solution containing iron (Fe) as a solute. The second liquid is a solution containing tannic acid. Next, in step S120, the first liquid and the second liquid are mixed to produce a mixture of the first and second liquids. In step S120, for example, the first liquid and the second liquid are alternately added to water, and the first and second liquids are mixed by stirring or the like. As a result of performing step S120, colorant particles are formed in the mixture of the first and second liquids. After that, in step S130, the colorant particles produced in step S120 are washed to obtain a paint colorant. In step S130, for example, impurities attached to the colorant particles can be washed away by repeatedly adding pure water to the colorant particles, centrifuging the mixture, and discarding the supernatant produced by centrifugation. The pH of the mixture may be adjusted between the start of step S120 and the start of step S130. For example, after the completion of step S120, a base such as sodium hydroxide can be added to the mixture to alter the color development by the pigment layer in the applied state.

[0018] Figure 2 shows an example of a method for additionally forming a pigment layer in a paint colorant. As shown in Figure 2, the thickness of the pigment layer can be increased by further forming a layer containing iron tannate around the pigment layer of the paint colorant. First, in step S210, the third liquid and the fourth liquid are prepared. The third liquid is a suspension in which colorant particles are suspended in a solution containing Fe as a solute. The fourth liquid is a solution containing tannic acid, similar to the second liquid. Next, in step S220, the third liquid and the fourth liquid are mixed in the same way as the first liquid and the second liquid are mixed in step S120 of Figure 1 to produce a mixture of the third liquid and the fourth liquid. As a result of performing step S220, an additional pigment layer is formed around the pigment layer of the colorant particles in the mixture, increasing the thickness of the pigment layer. Then, in step S230, the colorant particles obtained in step S220 are washed in the same way as in step S120 of Figure 1. Similar to the manufacturing method shown in Figure 1, the pH of the mixture may be adjusted between the start of step S220 and the start of step S230. For example, the additional formation of the pigment layer may be omitted, or it may be performed two or more times. By adjusting the number of times the pigment layer is formed, the thickness of the pigment layer in the paint colorant can be adjusted.

[0019] Figure 3 is a process diagram showing an example of a method for manufacturing a coated material. The coated material is manufactured by applying a paint containing the paint colorant of this embodiment onto a support. In this manufacturing method, first, in step S310, the paint and the support are prepared. As the paint, for example, a paint colorant dispersed in a liquid such as water can be used. If a liquid other than water is used, it is preferable to select a liquid that does not cause the color development or structural color of the paint colorant to be lost due to chemical reactions with the colorant particles or the pigment layer. The paint may also contain additives to improve the shelf life of the paint, for example. Next, in step S320, the paint is applied to the support while adjusting the thickness of the paint on the support so that the color development due to the pigment color and structural color is a predetermined color. Specifically, in step S320, for example, the number of times the paint is applied to the support and the amount applied are adjusted so that the thickness of the paint after drying is a predetermined thickness. The application of the paint to the support can be done in any way that results in a finished coating exhibiting structural color. For example, this may be done by dropping or spraying the paint onto the support, using a brush or similar tool, or by spin coating. Then, in step S330, the paint applied to the support is dried by natural drying or the like.

[0020] Furthermore, the thickness of the colorant on the support can be adjusted, for example, after coating in step S320 or after drying in step S330. Additionally, by adjusting the water absorption of the support prepared in step S310, the color development of the colorant in the coated state can also be adjusted by the water absorption of the support.

[0021] The paint colorant of this embodiment described above has a core and a pigment layer made of iron tannate, and contains colorant particles having a particle size corresponding to the wavelength of the structural color. As a result, by changing the coating thickness, the intensity ratio between the reflected light of the structural color and the reflected light of the pigment layer can be changed, and the color development can be arbitrarily changed. Therefore, the paint colorant exhibits a novel color development in which the color development can be adjusted by the coating thickness. Furthermore, since the paint colorant of this embodiment exhibits color development by both the pigment layer and the structural color, it is less likely to lose color due to sunlight, etc., compared to, for example, paint colorants that only develop pigment colors such as general organic pigments and dyes. Moreover, since the color development by the pigment layer is more prone to fading due to sunlight, etc., compared to the structural color, it is possible to enjoy the aging of the color development on the coated object, for example, and the aging of the color development can be used as an indicator of age. In addition, by using materials such as silica or glass containing 50% or more by mass of silica as the material forming the core, it is possible to reduce the environmental impact of colorants compared to general organic and inorganic pigments, and to achieve novel color development of the colorants.

[0022] Furthermore, in this embodiment, the color of the paint is adjusted not only by the coating thickness but also by the water absorption of the support. Therefore, the paint exhibits a novel color that can be adjusted not only by the coating thickness but also by the water absorption of the support.

[0023] B. Experimental results: Various colorants were prepared for the experiment. Furthermore, the effects of the above embodiment were verified by coating a support with the prepared colorants and measuring the reflectance spectrum of the coated material.

[0024] Five types of colorants, colorants A through E, were prepared. Colorants A through C were prepared according to the manufacturing method shown in Figure 1, and a pigment layer was further formed using the method shown in Figure 2. Colorants D and E were prepared using the method described later. For the silica particle aqueous suspension used as the raw material for the silica particles in the core, a silica particle aqueous suspension manufactured by Fuji Chemical Co., Ltd. was used. Specifically, for the preparation of colorants A and B, a silica particle aqueous suspension containing 26.3 mass% of silica particles with an average particle size of 268.3 nm was used, and for the preparation of colorant C, a silica particle aqueous suspension containing 26.8 mass% of silica particles with an average particle size of 322.4 nm was used. The average particle size of these silica particles was calculated based on the particle size distribution measurement results by dynamic light scattering. Specifically, the median diameter (D50) of the silica particles calculated from the measurement results by dynamic light scattering was used as the average particle size. The density of each silica particle aqueous suspension was 2.2 g / cm³. 3 Furthermore, the average particle size of the silica particles contained in the silica particle aqueous suspension used to prepare each colorant was used as the average particle size of the core of each colorant. As the raw material for tannic acid, tannic acid (molecular weight 1701.19) manufactured by Kishida Chemical Co., Ltd. was used.

[0025] In the preparation of colorant A, first, the first solution in step S110 was prepared by mixing 0.05 mL of an aqueous solution of iron(III) chloride hexahydrate with a concentration of 40 g / L and 0.55 mL of a silica particle aqueous suspension using a vortex mixer. Prior to the preparation of the first solution, the silica particle aqueous suspension was irradiated with ultrasound for 90 minutes to improve the dispersibility of the silica particles in the suspension. As the second solution, 0.6 mL of an aqueous solution of tannic acid with a concentration of 13 g / L was prepared. Next, in step S120, using a syringe, one drop (approximately 0.03 mL) each of the first and second solutions was alternately added to 25 mL of pure water, totaling 0.6 mL, and the mixture was stirred using a stirrer to prepare a mixture of the first and second solutions, thereby obtaining colorant particles. After step S120 was completed, the pH of the mixture was adjusted to 8.0 by adding 0.2 mL of 1 mol / L sodium hydroxide aqueous solution to the mixture. Then, in step S130, the mixture was first centrifuged, and the supernatant produced by centrifugation was discarded to obtain a residue containing colorant particles. Next, the residue was mixed with pure water using a vortex mixer, and the resulting suspension was further centrifuged, with the supernatant produced by centrifugation being discarded. This process was repeated to wash the colorant particles.

[0026] Furthermore, a 0.55 mL suspension was prepared by suspending the colorant particles obtained in step S130 in water. The third solution of step S210, shown in Figure 2, was prepared by mixing the prepared colorant suspension with an aqueous solution of iron(III) chloride hexahydrate, similar to that in step S110, using a vortex mixer. Subsequently, steps S220 and S230 were performed in the same manner as steps S120 and S130 to add and form a pigment layer around the colorant particles. In the case of colorant A, the pH of the mixture was adjusted after the completion of step S220, as was done after the completion of step S120, during the process of adding the pigment layer. This process of adding the pigment layer was performed a total of two times.

[0027] In the preparation of colorant B, the same procedure as for colorant A was followed, except that pH adjustment was not performed after the completion of step S120 and step S220. The pH after the completion of step S120 and step S220 for colorant B was 5.0. In the preparation of colorant C, in step S110, the first solution was prepared by mixing 0.05 mL of an aqueous solution of iron(III) chloride with a concentration of 40 g / L iron(III) chloride hexahydrate and 0.55 mL of a silica particle aqueous suspension using a vortex mixer. In step S210, a 0.55 mL suspension was prepared by suspending the colorant in water in step S130, and the third solution was prepared by mixing the prepared colorant suspension with an aqueous solution of iron(III) chloride similar to that used in step S110 using a vortex mixer. In the preparation of colorant C, as with the preparation of colorant B, no pH adjustment was performed after the completion of step S120 and step S220. In the preparation of colorant C, as with the preparation of colorant B, the pH after the completion of step S120 and step S220 was 5.0. Furthermore, in the preparation of colorant C, the same procedure as in the preparation of colorant B was followed, except for parts that are not specifically described.

[0028] Colorants D and E were prepared by mixing an aqueous solution of iron(III) chloride hexahydrate with a second solution. Specifically, 0.05 ml of an aqueous solution of iron(III) chloride hexahydrate with a concentration of 40 g / L of iron(III) chloride hexahydrate and 0.6 ml of a second solution with a concentration of tannic acid of 13 g / L were added to 25 ml of pure water and mixed by stirring with a stirrer to obtain the colorants. In the preparation of colorant D, after the preparation of the mixture was complete, the pH of the mixture was adjusted to 8.0 by adding 0.2 ml of a 1 mol / L aqueous solution of sodium hydroxide. In the preparation of colorant E, no pH adjustment of the mixture was performed, and the pH of the mixture after preparation was 5.0. Note that no washing step was performed in the preparation of colorants D and E.

[0029] The average particle size of the pigment particles contained in pigments B and C was calculated using the same method as the average particle size of the core. Furthermore, by subtracting the particle size of the core from the measured average particle size of the pigment particles, the thickness of the pigment layer formed around the core can be calculated.

[0030] Figure 4 shows the coated samples prepared in the experiment. Figure 4 indicates the type of colorant and support used for each sample, as well as the color development and structural color of the pigment layer in each sample. Each sample shown in Figure 4 was prepared by applying the colorant to a support and then drying it, according to the coating method shown in Figure 3. As shown in Figure 4, samples 1 to 3, samples 6, and samples 7 used a white unglazed ceramic plate manufactured by Nikkatoh as the support. Sample 4 used a transparent glass plate, specifically a transparent slide glass manufactured by Matsunami Glass Industry Co., Ltd., as the support. Sample 5 used white drawing paper, specifically white Montval Canson paper manufactured by Canson, as the support. By adjusting the amount of colorant applied during the preparation of each sample, multiple coated samples with different coating thicknesses were created for each sample.

[0031] The reflectance spectra of coated materials were measured using a USB2000 Miniature Fiber Optic Spectrometer manufactured by Ocean Optics. Specifically, white light was shone onto the sample at an angle perpendicular to the incident light, and the relative reflectance spectrum was measured. A PTFE standard white plate WS-1 manufactured by Ocean Photonics was used as the reference sample for the relative reflectance spectrum measurement. A halogen lamp was used as the white light source. For sample 4, which used transparent glass as the support, the sample was placed on white drawing paper for measurement. The reflected light intensity ratio was calculated from the measured reflectance spectra. The reflected light intensity ratio is the ratio of the reflected light intensity of the structural color to the reflected light intensity of the color development by the dye layer.

[0032] The coating thickness of the coated material was calculated using SEM (scanning electron microscope) images of the cross-section of the coated material. Specifically, four cross-sectional SEM images were observed for each coated material, and the thickness of the portion excluding the support was measured at two points for each SEM image. The average of the thicknesses of these eight measured points was then calculated to determine the coating thickness of the coated material.

[0033] The average particle size of the pigment particles in pigment B was 286.7 nm, and the average particle size of the pigment particles in pigment C was 373.6 nm. In pigments B and C, it is thought that iron tannate was adsorbed onto the silica particles that formed the core, forming a pigment layer containing iron tannate around the core, resulting in the formation of pigment particles with an average particle size larger than the average particle size of the core. Furthermore, the average particle size of the pigment particles in pigment C was larger than that of pigment B. Since the number of times the aforementioned pigment layer was added was the same for both pigment C and pigment B, it is thought that the larger average particle size of the pigment particles in pigment C was due to the average particle size of the core.

[0034] As shown in Figure 4, samples 1 through 5 exhibited both coloration from the pigment layer and structural coloration corresponding to the particle size of the pigment particles. Specifically, samples 1, 4, and 5, which used pigment A, exhibited coloration from the reddish-brown pigment layer and the green structural color. Sample 2, which used pigment B, exhibited coloration from the blue-violet pigment layer and the green structural color. Sample 3, which used pigment C, exhibited coloration from the blue-violet pigment layer and the red structural color. Sample 6, which used pigment D, exhibited reddish-brown from the pigment layer and no structural color. Sample 7, which used pigment E, exhibited blue-violet from the pigment layer and no structural color. It is thought that samples 6 and 7 did not exhibit structural coloration because pigments D and E do not have a core.

[0035] The structural color hue differed between Sample 3, which used colorant C, and the samples using colorant A or colorant B. As mentioned above, the particle size of the colorant particles in colorant C is larger than that of the colorant particles in colorant B. Also, as mentioned above, the only difference between the preparation methods for colorant A and colorant B is the presence or absence of pH adjustment, so the average particle size of the colorant particles in colorant A is considered to be about the same as that of colorant particles in colorant B. Therefore, it is thought that Sample 3 exhibited a longer wavelength red structural color compared to the samples using colorant A or colorant B, corresponding to the particle size of the colorant particles. Thus, in paint colorants, for example, the desired structural color can be expressed by experimentally investigating the relationship between the wavelength of the structural color and the particle size of the colorant particles in advance and adjusting the particle size of the colorant particles so that the desired structural color is expressed.

[0036] Figure 5 shows the reflectance spectra of Sample 1 and Sample 6. In Sample 1, reflected light of the green structural color was observed at each coating thickness. Specifically, reflected light of the structural color was observed at a wavelength of 555.04 nm for coating thicknesses of 5.17 μm, 7.78 μm, 28.54 μm, and 48.59 μm, and at a wavelength of 543.45 nm for a coating thickness of 144.67 μm. In addition, in both Sample 1 and Sample 6, red or reddish-brown reflected light from the dye layer was observed at wavelengths of 700 nm to 750 nm.

[0037] Figure 6 shows the relationship between coating thickness and reflected light intensity ratio in Sample 1. The reflected light intensity ratio in Figure 6 was calculated as the ratio of the reflected light intensity of the structural color at the aforementioned wavelength for each coating thickness to the reflected light intensity at a wavelength of 700 nm. As shown in Figure 6, in Sample 1, the reflected light intensity ratio increased with increasing coating thickness. Furthermore, visual inspection of Sample 1 revealed that the greener the color, the thicker the coating. In Sample 1, it is thought that as the coating thickness increased, the portion of the particles arranged with periodicity increased in the thickness direction, resulting in a stronger reflection of the structural color relative to the reflected light from the coloring caused by the dye layer.

[0038] Figure 7 shows the reflectance spectrum of Sample 4. In Sample 4, as with Sample 1, reflected light of the green structural color was observed at each coating thickness. Specifically, reflected light of the structural color was observed at a wavelength of 553.5 nm for a coating thickness of 4.70 μm, at a wavelength of 567.4 nm for a coating thickness of 17.00 μm, at a wavelength of 551.18 nm for a coating thickness of 23.60 μm, at a wavelength of 538.03 nm for a coating thickness of 180.00 μm, and at a wavelength of 526.41 nm for a coating thickness of 326.00 μm. In addition, in Sample 4, as with Sample 1, red or reddish-brown reflected light from the dye layer was observed at wavelengths of 700 nm to 750 nm.

[0039] Figure 8 shows the relationship between coating thickness and reflected light intensity ratio in Sample 4. The reflected light intensity ratio in Figure 8 was calculated in the same way as the reflected light intensity ratio in Sample 1 shown in Figure 6. As shown in Figure 8, in Sample 4, similar to Sample 1, the reflected light intensity ratio increased with increasing coating thickness. Also, visual inspection of Sample 4 revealed that, similar to Sample 1, the greener the color, the thicker the coating thickness. Therefore, in Sample 4, similar to Sample 1, it is considered that as the coating thickness increased, the portion of the particles arranged with periodicity increased in the thickness direction, and the reflected light of the structural color became stronger compared to the reflected light of the color produced by the dye layer.

[0040] Figure 9 shows the reflectance spectrum of Sample 5. In Sample 5, green structural color reflected light was observed at each coating thickness, similar to Samples 1 and 4. Specifically, structural color reflected light was observed at a wavelength of 545.77 nm for a coating thickness of 45.11 μm, at a wavelength of 543.45 nm for a coating thickness of 78.59 μm, and at a wavelength of 531.80 nm for a coating thickness of 122.44 μm. In addition, in Sample 5, red or reddish-brown reflected light from the dye layer was observed at wavelengths of 700 nm to 750 nm, similar to Samples 1 and 4.

[0041] Figure 10 shows the relationship between coating thickness and reflected light intensity ratio in Sample 5. The reflected light intensity ratio in Figure 10 was calculated in the same way as the reflected light intensity ratios in Sample 1 shown in Figure 6 and Sample 4 shown in Figure 8. As shown in Figure 10, in Sample 5, similar to Samples 1 and 4, the reflected light intensity ratio increased with increasing coating thickness. Also, visually inspecting Sample 5, similar to Samples 1 and 4, the greener the color became with increasing coating thickness. In Sample 5, similar to Samples 1 and 4, it is thought that as the coating thickness increased, the portion of the particles arranged with periodicity increased in the thickness direction, and the reflected light of the structural color became stronger compared to the reflected light of the color development by the dye layer.

[0042] In Sample 1, shown in Figures 5 and 6, the reflected light intensity ratio is larger compared to Sample 4, shown in Figures 7 and 8, and the increase in reflected light intensity ratio with increasing coating thickness is also greater. Since the support for Sample 1 is an unglazed ceramic plate, it has higher water absorption than the glass plate, which is the support for Sample 4. Therefore, during the drying process of the paint on the support when preparing Sample 1, the liquid components contained in the paint are easily absorbed by the support. As a result, compared to cases where a glass plate or the like with lower water absorption than an unglazed ceramic plate is used as the support, the arrangement of the colorant particles is disrupted due to diffusion caused by the absorption of liquid components into the support, making it difficult for the particles to arrange in a periodic manner. On the other hand, in Sample 4, since the liquid components contained in the paint are not easily absorbed by the support during the drying process on the support, it is thought that the particles were more likely to arrange in a periodic manner.

[0043] Furthermore, in Sample 5, shown in Figures 9 and 10, the reflected light intensity ratio is larger compared to Sample 1, shown in Figures 4 and 5, and the increase in the reflected light intensity ratio with increasing coating thickness is greater. Also, compared to Sample 4, shown in Figures 7 and 8, the reflected light intensity ratio is smaller, and the increase in the reflected light intensity ratio with increasing coating thickness is smaller. Since the support for Sample 5 is drawing paper, it has a water absorption rate that is higher than that of a glass plate and lower than that of a bisque plate. Therefore, it is considered that in Sample 5, during the process of drying the paint on the support, the particles were more likely to arrange in a periodic manner compared to Sample 1, and less likely to arrange in a periodic manner compared to Sample 4.

[0044] Furthermore, by referring to experimental results such as those shown in Figures 6, 8, and 10, the color development when a paint containing a colorant is applied to a support can be arbitrarily adjusted by the application thickness of the colorant. For example, by referring to the experimental results shown in Figure 6, the relationship between the application thickness and the reflected light intensity ratio, and the relationship between the reflected light intensity ratio and the resulting color can be investigated, and the colorant can be made to develop the desired hue by applying the colorant to the support with that application thickness. The relationship between the reflected light intensity ratio and the resulting color can be investigated, for example, by visually confirming the color development at a certain reflected light intensity ratio, or by calculating the L*, a*, and b* values ​​in a color space such as the L*a*b* color system from the reflection spectrum and investigating the relationship between these values ​​and the reflected light intensity ratio. In this case, for example, the experimental results in Figure 6 and the changes in each value in the L*a*b* color space can be analyzed and fitted with a function, and the application thickness required to achieve a specific color can be investigated based on the fitted function. Alternatively, for example, the relationship between the application thickness and the resulting color can be investigated. Furthermore, by referring to the experimental results when colorants for paints were prepared using supports with different water absorption properties, as shown in Figures 6, 8, and 10, the relationship between the water absorption of the support and color development can be investigated, and the color development of the coated object can be adjusted by the water absorption of the support.

[0045] Based on the experimental results described above, it was confirmed that a paint colorant containing particles having a core and a pigment layer containing iron tannate formed around the core exhibits novel color development, with the color development adjustable by the coating thickness.

[0046] This disclosure is not limited to the embodiments described above, and can be implemented in various configurations without departing from its spirit. For example, the technical features of the embodiments corresponding to the technical features in each form described in the summary of the invention can be replaced or combined as appropriate in order to solve some or all of the above-described problems, or to achieve some or all of the above-described effects. Furthermore, if a technical feature is not described as essential in this specification, it can be deleted as appropriate.

Claims

1. A paint colorant to be applied to a substrate, The pigment comprises a core and a pigment layer containing iron tannate formed around the core, the pigment having a particle diameter corresponding to the wavelength of the structural color, a color is produced by the pigment layer and the structural color, A color material for paint, characterized in that the color development can be adjusted by the coating thickness.

2. The paint color material according to claim 1, A color material for paint, characterized in that the color development can be adjusted not only by the coating thickness but also by the water absorbency of the support.

3. a step of applying a coating material containing particles having a core portion and a pigment layer containing iron tannate formed around the core portion, the particles having a particle size corresponding to the wavelength of the structural color, to a support; and adjusting the thickness of the paint on the support to adjust the color produced by the pigment layer and the structural color.

Images