Method for evaluating concealment ability

Abstract

To provide a method for evaluating hiding power more easily.SOLUTION: A method for evaluating hiding power is a method which evaluates hiding power of a particle-containing body containing particles as a target of evaluation of the hiding power. The method includes the step of calculating an absorbance degree (Abs) of electromagnetic waves by a following expression (1): Abs=-log(I / I0) on the basis of a transmission amount (I) of electromagnetic waves of the particle-containing body and a base material and a transmission amount (I0) of electromagnetic waves of no-particles-containing body with a same composition as that of the particle-containing body other than inclusion of no particles and the base material.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention generally relates to a method for evaluating the hiding power of a particle-containing body containing particles, and specifically relates to a method for evaluating the hiding power of a coating film using a pigment as the particle.

Background Art

[0002] Conventionally, the hiding power of a coating film containing particles such as pigments has been evaluated. For example, the measurement of the degree to which the base color is hidden by the paint (hiding power) can be obtained by actually measuring the tristimulus values of a coated board obtained by applying the paint on white and black bases and drying it, as described in JIS K 560-4-1:1999K (ISO / FDIS 6504-3:1998).

[0003] In addition, since metallic effect pigments do not transmit light, the hiding power is considered to depend on the area of the coating film surface covered by the metallic effect pigment. Therefore, the water surface spreading area (WCA) defined in JIS K 5906:1998 (Non-Patent Document 2) is used as an index representing the hiding power of a coating film using a metallic effect pigment.

[0004] The hiding power of the coating film is adjusted by repeating the adjustment of the pigment concentration or the coating film thickness in the paint and the visual evaluation of the hiding power.

Prior Art Documents

Non-Patent Documents

[0005]

Non-Patent Document 1

Non-Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0006] However, in the method of Non-Patent Document 1, coated paper using a dedicated hiding power test paper is required.

[0007] The method described in Non-Patent Document 2 cannot be applied to pigments that do not float in water. Furthermore, it is time-consuming.

[0008] Conventional techniques for adjusting opacity require preparing a separate paint preparation method for each individual pigment, which is inefficient. Furthermore, it is necessary to investigate the paint preparation method for new pigments.

[0009] Regarding color tones, the Hunter 1948 (L, a, b) color space and CIE 1976 (L * a * , b * While various measurement methods exist, such as color space and gloss, and comparison with standard values ​​is possible, opacity is still primarily evaluated relatively by comparison with standard samples.

[0010] This invention allows for the absolute and relative evaluation of opacity by measuring the visible light transmittance intensity of coated boards and coated papers used for color tone evaluation for quality confirmation, such as art paper (coated paper) and PET film, without using black and white opacity test paper. This reduces the time required for evaluation and the amount of paint used.

[0011] Therefore, the object of the present invention is to provide a simpler method for evaluating concealment. [Means for solving the problem]

[0012] The inventors conducted diligent research to solve the above problems. As a result, as detailed in the examples, the inventors found that the absorbance, which is determined based on the ratio of the light transmittance of a coating film containing a pigment to a coating film without a pigment, is proportional to the water surface diffusion area (WCA). In other words, according to the present invention, the hiding power of a coating film can be evaluated simply by measuring the absorbance of the coating film, without using special test paper as a substrate. Furthermore, according to the present invention, even for pigments that do not float on water and for which the WCA cannot be determined, the hiding power can be evaluated by obtaining a value proportional to the WCA. Moreover, it was found that the evaluation method of the present invention can evaluate the hiding power not only when the pigment is contained in a coating film formed on a substrate, but also when it is kneaded into the substrate. Furthermore, it was also found that the shielding power against electromagnetic waves can be evaluated by measuring the absorption of electromagnetic waves other than visible light. Based on the inventors' above viewpoint, the hiding power evaluation method, quality control method, and quality assurance method of the present invention have the following configurations.

[0013] The present invention provides a method for evaluating the concealment capacity of a particle-containing material containing particles to be evaluated, and includes the step of calculating the electromagnetic wave absorptiveness (Abs) using the following formula (1) based on the amount of electromagnetic wave transmission (I) between the particle-containing material and the substrate, and the amount of electromagnetic wave transmission (I0) between a non-particle-containing material having the same composition as the particle-containing material except that it does not contain particles and the substrate. Equation (1) Abs = -log(I / I0)

[0014] This eliminates the need to use opacity test paper as a base material. Furthermore, it provides a simpler method for evaluating opacity.

[0015] In the following text, the term "absorption (Abs)" for electromagnetic waves may also be referred to as "absorbance (Abs)" when the electromagnetic wave is visible light.

[0016] The method for evaluating opacity according to the present invention preferably includes a step of calculating the value of (absorption (Abs)) / (concentration of particles in the particle-containing material (C)).

[0017] The method for evaluating the shielding power according to the present invention preferably includes a step of calculating the thickness (L) of a particle-containing body having a desired shielding power based on the absorbance (Abs) of electromagnetic waves of the particle-containing body, the concentration (C) of the particles, and the absorption coefficient (ε) of electromagnetic waves of the particles by the following formula (2). Formula (2) L = Abs / (ε × C)

[0018] The method for evaluating the shielding power according to the present invention preferably includes a step of calculating the concentration (C) of the particles of a particle-containing body having a desired shielding power based on the absorbance (Abs) of electromagnetic waves of the particle-containing body, the thickness (L) of the particle-containing body, and the absorption coefficient (ε) of electromagnetic waves of the particles by the following formula (3). Formula (3) C = Abs / (ε × L)

[0019] The method for evaluating the shielding power according to the present invention is based on the absorbance (Abs) of electromagnetic waves of a particle-containing body having a desired shielding power, the absorbance (Abs1) of electromagnetic waves of a first particle-containing body containing only the first particles as the particles, and the absorbance (Abs2) of electromagnetic waves of a second particle-containing body containing only the second particles as the particles. Preferably, it includes a step of calculating the weight ratio (X) of the first particles and the weight ratio (1 - X) of the second particles in the mixed particle-containing body containing the first particles and the second particles having a desired shielding power by the following formula (4). Formula (4) Abs1 × X + Abs2 × (1 - X) = Abs (0 ≤ X ≤ 1)

[0020] In the method for evaluating the shielding power according to the present invention, preferably, the particles are contained in a coating film formed on a substrate or kneaded into the substrate.

[0021] In the method for evaluating the shielding power according to the present invention, preferably, the particles are pigments.

[0022] In the method for evaluating the shielding power according to the present invention, preferably, the electromagnetic waves are visible light.

[0023] In the method for evaluating the shielding power according to the present invention, preferably, the particles are particles having electromagnetic wave shielding performance, and the shielding power is electromagnetic wave shielding power.

[0024] In the concealment evaluation method according to the present invention, it is preferable that the electromagnetic wave is an electromagnetic wave other than visible light, and the concealment force is the electromagnetic wave shielding force.

[0025] A quality control method according to the present invention includes the steps of defining absolute or relative concealment by the concealment evaluation method described above, and performing quality control of the product based on the absolute or relative concealment.

[0026] A quality assurance method according to the present invention includes the steps of defining absolute or relative concealment by the concealment evaluation method described above, and ensuring the quality of the product based on the absolute or relative concealment. [Brief explanation of the drawing]

[0027] [Figure 1] This figure shows the relationship between absorbance (Abs) and pigment concentration (C) of the pigment-containing coating films of Examples 1 to 7. [Figure 2] This figure shows the relationship between the absorbance (Abs) of the pigment-containing coating films of Examples 1 to 7 divided by the pigment concentration (C), and the water surface diffusion area (WCA) of each pigment. [Figure 3] This figure shows the relationship between absorbance (Abs) and pigment concentration (C) of the pigment-containing coating films of Examples 8 to 14. [Figure 4] This figure shows the relationship between the absorbance (Abs) of the pigment-containing coating films of Examples 8 to 14, divided by the pigment concentration (C), and the water surface diffusion area (WCA) of each pigment. [Figure 5] This figure shows the relationship between absorbance (Abs) and pigment concentration (C) of the pigment-containing coating films of Examples 15 to 21. [Figure 6] This figure shows the relationship between the absorbance (Abs) of the pigment-containing coating films of Examples 15 to 21, divided by the pigment concentration (C), and the water surface diffusion area (WCA) of each pigment. [Figure 7] This figure shows the relationship between absorbance (Abs) and pigment concentration (C) of the pigment-containing coating films of Examples 23 and 24. [Modes for carrying out the invention]

[0028] The method for evaluating the concealment capacity of the present invention will be described in detail below with specific examples. It should be noted that the present invention is not limited to the embodiments shown below, and various modifications are possible without departing from the technical spirit of the present invention.

[0029] The present invention provides a method for evaluating the concealment capacity of a particle-containing material containing particles to be evaluated, and includes the step of calculating the electromagnetic wave absorptiveness (Abs) using the following formula (1) based on the amount of electromagnetic wave transmission (I) between the particle-containing material and the substrate, and the amount of electromagnetic wave transmission (I0) between a non-particle-containing material having the same composition as the particle-containing material except that it does not contain particles and the substrate. Equation (1) Abs = -log(I / I0)

[0030] As one embodiment, a method for evaluating the opacity of a coating film containing pigments, where the opacity of visible light is to be evaluated, will be described.

[0031] First, a paint containing pigment particles is applied to a substrate (hereinafter also referred to as the "undercoat") and dried to form a pigment-containing coating film. Next, a pigment-free coating film (hereinafter sometimes referred to as the "blank" or "control"), which has the same composition as the pigment-containing coating film except that it does not contain pigment particles, is formed on the substrate or undercoat. Note that the pigment-containing coating film is an example of a particle-containing material, and the pigment-free coating film is an example of a particle-free material.

[0032] As paints containing pigments, known paints can be used, such as those in which aluminum pigment (paste) is dispersed in nitrocellulose lacquer, acrylic lacquer, or water-based paint. Since the correlation coefficient between Abs and WCA, described later, varies depending on the affinity between the resin component and the pigment in the paint, it is desirable to use a nitrocellulose lacquer that has a wide range of affinity.

[0033] The substrate is not limited to any particular type; coated boards, coated paper, etc., used for color evaluation for quality confirmation, such as art paper (coated paper) or PET film, can be used.

[0034] The method for preparing the coating film should be the same for both pigment-containing and pigment-free coating films, ensuring that conditions such as lacquer, coating film thickness, coating plate, application method, drying temperature, and drying method are consistent.

[0035] Painting is performed, for example, by applying the paint to the substrate using the doctor blade method. For example, using commercially available nitrocellulose lacquer, a particle-containing material and a particle-free material can be obtained by applying it to PET film or art paper (coated paper) using the doctor blade method.

[0036] The film applicator used for the doctor blade can be, for example, 2 mils (50.8 μm) to ensure consistent pigment orientation, but film applicators of 6 mils, 9 mils, etc. may also be used. A coating obtained by applying with 9 mils will be 4.5 times thicker than a coating obtained by applying with 2 mils, but due to the disorder of pigment orientation and the effects of secondary reflections, the absorbance (Abs) may be slightly less than 4.5 times.

[0037] The pigment-containing coating obtained in this way contains pigment particles. The particle-containing material may also be prepared by kneading pigment particles into a substrate, in addition to being a coating.

[0038] For the obtained particle-containing material (pigment-containing coating) and particle-free material (pigment-free coating), the transmittance I and I0 of light at the wavelength to evaluate the opacity are measured, and the absorbance (Abs) is determined based on equation (1) Abs = -log(I / I0). The transmittance I and I0 can be measured by any known method capable of measuring the transmittance of light at the wavelength to evaluate the opacity, and are not limited to this method. For example, a spectrophotometer CM-5 (Konica Minolta) can be used. For transmittance measurement, the light intensity must be sufficiently strong, or the detection capability of the detection device that detects light passing through the coating must be sufficiently high. When using a spectrophotometer, the lightness (L *The value can be treated as the amount of light transmitted.

[0039] When evaluating the opacity of visible light, if the substrate or base material is opaque to visible light, the CM-5 spectrophotometer may not be able to measure transmittance. In such cases, transmittance may be measured using a white LED light source and an illuminometer.

[0040] It is also possible to evaluate the shielding power of electromagnetic waves other than visible light, for example, by using particles that have electromagnetic shielding properties. The wavelength of the electromagnetic wave whose shielding power is to be evaluated is not limited. For example, it can be applied to long waves, medium waves, short waves, very high frequency waves, microwaves, radio waves, infrared rays, visible light, ultraviolet rays, EUV rays, X-rays, and gamma rays. When evaluating the shielding power of electromagnetic waves other than visible light, the absorbance (Abs) of the electromagnetic wave at the wavelength whose shielding power is to be evaluated is determined based on equation (1) Abs = -log(I / I0). To measure the amount of electromagnetic wave transmission, it is sufficient to select a light source that can irradiate electromagnetic waves of the required wavelength and an electromagnetic wave detector corresponding to that wavelength.

[0041] The absorbance (Abs) values ​​obtained in this manner reflect the opacity of particles such as pigments, as will be explained in detail in the examples.

[0042] This eliminates the need to use opacity test paper as a base material. This allows for a simpler method of evaluating concealment capabilities.

[0043] Furthermore, it is preferable to include a step of calculating the value of (absorption (Abs)) / (concentration of particles in the particle-containing material (C)). The inventors have found that the value of (absorption (Abs)) / (concentration of particles in the particle-containing material (C)) is proportional to the WCA (water surface diffusion area). Therefore, by calculating the value of (absorption (Abs)) / (concentration of particles in the particle-containing material (C)), the hiding power of particles that do not float on water can be evaluated in the same way as when WCA is used, without measuring WCA.

[0044] The relationship between the thickness (L) of a particle-containing material (pigment-containing coating), the absorption coefficient (ε) of the particles (pigments) for electromagnetic waves (visible light), and the concentration (C) of the particles (pigments) in the particle-containing material (pigment-containing coating) is given by Absorbance (Abs) = ε × L × C (Lambert-Beer's law). Therefore, the thickness (L) of a particle-containing material with the desired hiding power can be calculated based on the electromagnetic wave absorption (Abs), particle concentration (C), and electromagnetic wave absorption coefficient (ε) of the particles using the following equation (2). Equation (2) L=Abs / (ε×C)

[0045] Furthermore, the concentration of particles (C) in a particle-containing material that has a desired hiding power can be calculated using the following formula (3), based on the electromagnetic wave absorption (Abs) of the particle-containing material, the thickness (L) of the particle-containing material, and the electromagnetic wave absorption coefficient (ε) of the particles. Equation (3) C=Abs / (ε×L)

[0046] In the concealment evaluation method according to the present invention, the weight ratio of each particle required to obtain the desired concealment force can be determined for a mixed particle-containing material that mixes two types of particles. Specifically, based on the electromagnetic wave absorption (Abs) of a particle-containing material having the desired concealment force, the electromagnetic wave absorption (Abs1) of a first particle-containing material containing only the first particle, and the electromagnetic wave absorption (Abs2) of a second particle-containing material containing only the second particle, the weight ratio of the first particle (X) and the weight ratio of the second particle (1-X) in a mixed particle-containing material containing the first and second particles having the desired concealment force can be calculated using the following formula (4). Formula (4) Abs1×X+Abs2×(1-X)=Abs (0≦X≦1)

[0047] A quality control method according to the present invention includes the steps of defining absolute or relative concealment by the concealment evaluation method described above, and performing quality control of the product based on the absolute or relative concealment.

[0048] A quality assurance method according to the present invention includes the steps of defining absolute or relative concealment by the concealment evaluation method described above, and ensuring the quality of the product based on the absolute or relative concealment. [Examples]

[0049] The method for evaluating the concealment capacity of the present invention will be described in detail below, with specific examples. It should be noted that the present invention is not limited to the embodiments shown below, and various modifications are possible without departing from the technical spirit of the present invention.

[0050] (Examples 1-7) Aluminum pigments (pastes) A-G listed in Table 1 were used as pigments. The paste weights shown in Table 2 a-c were measured out, and a total of 50g of commercially available nitrocellulose lacquer was added to each. The mixtures were then uniformly stirred in a planetary mixer to prepare the paint. Average particle size D 50 The particle size distribution was measured using the MT3300EX II (Microtrac-Bel) particle size analyzer. The WCA of each pigment was measured based on Non-Patent Literature 2.

[0051] [Table 1]

[0052] [Table 2]

[0053] Each of the obtained coatings was applied to a PET film using a 2 mils (50.8 μm) applicator and dried at room temperature to obtain the pigment-containing coating film for each example. As a blank, nitrocellulose lacquer was applied with a 2 mils applicator and dried at room temperature to prepare a pigment-free coating film.

[0054] Pigment-containing and pigment-free coatings, fabricated on PET film, were cut into approximately 6 cm squares along with the PET film to serve as test specimens. The L* values ​​of the pigment-containing and pigment-free coating specimens were measured using the transmitted light intensity measurement unit of a CM-5 spectrophotometer (Konica Minolta). The absorbance Abs was determined by treating (L* value of pigment-containing coating) / (L* value of pigment-free coating) as the transmittance. The results are shown in Table 3.

[0055] [Table 3]

[0056] Based on these results, Figure 1 shows the absorbance Abs plotted against pigment concentration C. From Figure 1, it can be seen that for all pigments, the relationship between absorbance Abs and pigment concentration C can be approximated by a straight line passing through the origin. Furthermore, Table 3 shows the values ​​of the slope Abs / C obtained by the least squares method for these straight lines passing through the origin.

[0057] Figure 2 shows the WCA of each pigment plotted against the above Abs / C ratio. The slope obtained by the least squares method was 1538.8. Equation (5) can be derived from this result.

[0058] From Figure 2, it can be seen that in metallic pigments, the Abs / C ratio is proportional to WCA, indicating that the absorbance Abs reflects the opacity.

[0059] (Examples 8-14) In the same manner as in Example 1, paints were prepared using each of the aluminum pigments (pastes) A ​​to G to obtain the pigment concentration C shown in Table 4. The prepared paints were applied to art paper using a 2 mils (50.8 μm) applicator and dried at room temperature to obtain the pigment-containing coatings for each example. Separately, the nitrocellulose lacquer used in the paint preparation was applied to art paper using a 2 mils applicator and dried at room temperature to prepare pigment-free coatings.

[0060] Each of the fabricated pigment-containing and pigment-free coating films was irradiated with a white LED with a frontal illuminance of 345,000 lux, and the light transmittance values ​​I for each sample coating film and I0 for the standard coating film were measured using a commercially available illuminometer. A cylindrical black ABS resin was used between the light source and the illuminometer to avoid light leakage and contamination from external light sources. The apparatus structure was designed so that the distance from the light source to the coating film was approximately 40 mm, and the distance from the coating film to the surface of the illuminometer was approximately 15 mm. The absorbance Abs of each sample coating film calculated from the measurement results is shown in Table 4.

[0061] [Table 4]

[0062] Based on these results, Figure 3 shows the absorbance Abs plotted against the pigment concentration C. From Figure 3, it can be seen that even in coatings using art paper, the relationship between absorbance Abs and pigment concentration C can be approximated by a straight line passing through the origin for all pigments. Furthermore, Table 5 shows the values ​​of the slope Abs / C obtained by the least squares method for these straight lines passing through the origin.

[0063] [Table 5]

[0064] Figure 4 shows the WCA of each pigment plotted against the above Abs / C ratio. From Figure 4, it can be seen that even when opaque art paper is used as the substrate, the Abs / C ratio is proportional to the WCA, and the opacity can be evaluated. The slope obtained by the least squares method was 776.5. Equation (6) can be derived from this result.

[0065] (Examples 15-21) Each paint was prepared so that the pigment concentration C shown in Table 6 was achieved using each pigment. The absorbance Abs was measured using each of the obtained paints in the same manner as in Example 8, except that a 9 mils (228.6 μm) applicator was used. The results are shown in Table 6.

[0066] [Table 6]

[0067] Based on these results, Figure 5 shows the absorbance Abs plotted against the pigment concentration C. From Figure 5, it can be seen that even in coatings using art paper, the relationship between absorbance Abs and pigment concentration C can be approximated by a straight line passing through the origin for all pigments. Furthermore, Table 7 shows the values ​​of the slope Abs / C obtained by the least squares method for these straight lines passing through the origin.

[0068] [Table 7]

[0069] Figure 6 shows the WCA of each pigment plotted against the above Abs / C ratio. The slope obtained by the least squares method was 224.6. Equation (7) can be derived from this result.

[0070] Figure 6 shows that even when the amount of paint applied is changed, it is possible to evaluate the opacity as long as the measurements are taken under the same conditions.

[0071] Equation (5) WCA = 1538.8 × Abs / C (When test coatings are prepared and their transmittance is measured as in Examples 1-7)

[0072] Equation (6) WCA = 776.5 × Abs / C (When test coatings are prepared and their transmittance is measured as in Examples 8-14)

[0073] Equation (7) WCA = 224.6 × Abs / C (When test coatings are prepared and their transmittance is measured as in Examples 15-21)

[0074] As described above, even for hydrophilic pigments for which WCA cannot be obtained using the method described in Non-Patent Document 2, an estimated WCA can be obtained from the correlation coefficient mentioned above by forming a coating film on PET film or art paper and measuring the absorbance Abs and pigment concentration C. Specifically, the estimated WCA value for silica-coated aluminum pigment EMR-B5680 (paste manufactured by Toyo Aluminum), for which WCA cannot be obtained using the method described in Non-Patent Document 2, is 24,000 cm². 2 The value per gram of aluminum was obtained. Paint and coating preparation and measurement of absorbance Abs were carried out in the same manner as in Examples 15-21 (the obtained absorbance Abs and Abs / C are shown in Table 8), and the estimated WCA value was calculated using formula (7) (estimated WCA = 224.6 × 106.7 = 24000 cm²). 2 ( / g).

[0075] [Table 8]

[0076] (Example 22) (Adjusting the opacity of the pigment) Using a sample pigment with absorbance Abs at pigment concentration C, and using the absorbance Abs0 of a target pigment with desired opacity at pigment concentration C0, a pigment concentration C' = C × Abs0 / Abs that gives the same opacity as the target pigment at concentration C0 can be used to prepare a paint with the same opacity as the target pigment (C0 and C may be equal or different).

[0077] Aluminum pigments (pastes) A, H, and I listed in Table 9 were used as pigments. 0.7 g of each pigment paste was measured out, and 50 g of commercially available nitrocellulose lacquer was added to each paste. The mixture was then uniformly stirred in a planetary mixer to prepare the paints. The prepared paints were applied to art paper using a 9 mils (228.6 μm) applicator and dried at room temperature to obtain each sample coating. Separately, the nitrocellulose lacquer used for paint preparation was applied to art paper using a 9 mils applicator and dried at room temperature to prepare a target coating with the desired opacity. The absorbance Abs of aluminum pigments A, H, and I was determined using the same measurement method as in Example 15, and the relative absorbance to the target pigment's absorbance Abs was calculated. The relative absorbances are shown in Table 9.

[0078] [Table 9]

[0079] When the weight percentage of aluminum pigment H is X and the weight percentage of aluminum pigment I is (1-X), the following equation (8) can be established. Equation (8) (Relative absorbance of the coating film containing pigment H relative to the target coating film) × X + (Relative absorbance of the coating film containing pigment I relative to the target coating film) × (1 - X) = 1 (0 ≤ x ≤ 1)

[0080] In the case of Example 22 1.34 × X + 0.69 × (1 - X) = 1.00 X = 0.48 This is the result.

[0081] Based on the pigment weight ratio calculated by formula (8), aluminum pigments (pastes) H and I were mixed to prepare a mixed pigment. A sample of the mixed pigment was taken so that the total weight of the pigment to be incorporated into the paint was 0.7 g, and a commercially available nitrocellulose lacquer was added to make a total of 50 g. The mixture was then uniformly stirred in a planetary mixer to prepare the paint. The prepared paint was applied to art paper using a 9 mils (228.6 μm) applicator and dried at room temperature to obtain the sample coating film. In addition, the nitrocellulose lacquer used for paint preparation was applied directly to art paper using a 9-mil applicator and dried at room temperature to create a pigment-free coating.

[0082] Using the same measurement method as in Example 15, the absorbance Abs of the mixed pigment (paste) was determined, and the relative absorbance with respect to the absorbance Abs of the target pigment was calculated. The result showed that the relative absorbance value with respect to target pigment A was 1.02, confirming that it has the same opacity as the target pigment. This makes it possible to suppress variations in opacity that occur between manufacturing lots of pigments, for example.

[0083] (Example 23) As pigments, 30.0 kg of the blue pigment shown in Table 10, 75.0 kg of HAWS, and 3.0 kg of dispersant were crushed in a bead mill to obtain a slurry with a pigment concentration of 27.8%. Using the slurry obtained in place of the aluminum pigment, the absorbance Abs was measured at pigment concentration C in each paint shown in Table 10, as in Example 8. The results are shown in Table 10 and Figure 7.

[0084] [Table 10]

[0085] (Example 24) The slurry obtained by crushing 4.6 kg of the red pigment shown in Table 10, 25.1 kg of HAWS, and 0.5 kg of dispersant in a bead mill was subjected to absorbance measurement (Abs) in the same manner as in Example 23. The results are shown in Table 10 and Figure 7.

[0086] Figure 7 shows that, although the Abs / C value is not constant for chromatic pigments, it is possible to create a calibration curve that provides an approximation.

[0087] The resulting calibration curve can be used for opacity adjustment and other purposes, similar to the studies using aluminum pigments.

[0088] The embodiments and examples disclosed above should be considered in all respects to be illustrative and not restrictive. The scope of the present invention is indicated by the claims rather than the embodiments and examples above, and includes all modifications and variations in the sense and scope equivalent to the claims.

Claims

1. A method for evaluating the hiding power of particles in a particle-containing material that includes the particles to be evaluated for hiding power, The particle-containing material is formed on a substrate that does not contain the particles, The amount of electromagnetic waves transmitted between the particle-containing material and the substrate (I), and the amount of electromagnetic waves transmitted between the non-particle-containing material, which has the same composition as the particle-containing material except that it does not contain the particles, and the substrate (I ０ A method for evaluating concealment capacity, comprising the step of calculating the electromagnetic wave absorptiometry (Abs) based on the following formula (1). Equation (1) Abs = -log(I / I ０ )

2. A method for evaluating the hiding power of particles in a particle-containing material that includes the particles to be evaluated for hiding power, The particle-containing material is composed of the particles kneaded into the substrate and the substrate, The amount of electromagnetic waves transmitted (I) by the particle-containing material and the amount of electromagnetic waves transmitted (I) by a non-particle-containing material having the same composition as the particle-containing material except that it does not contain the particles. ０ A method for evaluating concealment capacity, comprising the step of calculating the electromagnetic wave absorptiometry (Abs) based on the following formula (1). Equation (1) Abs = -log (I / I ０ )

3. A method for evaluating the hiding power according to claim 1 or claim 2, comprising the step of calculating the value of (absorption (Abs)) / (concentration (C) of the particles in the particle-containing material).

4. A method for evaluating the hiding power according to claim 1 or claim 2, comprising the step of calculating the thickness (L) of the particle-containing material having a desired hiding power based on the absorption rate (Abs) of the electromagnetic waves of the particle-containing material, the concentration (C) of the particles, and the absorption coefficient (ε) of the particles, using the following formula (2). Formula (2) L=Abs / (ε×C)

5. A method for evaluating the hiding power according to claim 1 or claim 2, comprising the step of calculating the concentration (C) of the particles in the particle-containing material having a desired hiding power based on the electromagnetic wave absorption (Abs) of the particle-containing material, the thickness (L) of the particle-containing material, and the electromagnetic wave absorption coefficient (ε) of the particles, using the following formula (3). Formula (3) C=Abs / (ε×L)

6. The electromagnetic wave absorption (Abs) of the particle-containing material containing the particles having the desired hiding power, and the electromagnetic wave absorption (Abs) of the first particle-containing material containing only the first particles as particles. １ ) and the electromagnetic wave absorption (Abs) of a second particle-containing material that contains only the second particle as a particle. ２ A method for evaluating the hiding power according to claim 1 or 2, comprising the step of calculating the weight ratio of the first particles (X) and the weight ratio of the second particles (1-X) in a mixed particle containing the first particles and the second particles having the desired hiding power, based on the above, using the following formula (4). Formula (4) Abs １ ×X + Abs ２ ×(1 - X) = Abs (0 ≤ X ≤ 1)

7. The method for evaluating opacity according to claim 6, wherein the particles are pigments.

8. The method for evaluating concealment capacity according to claim 7, wherein the electromagnetic wave is visible light.

9. The method for evaluating concealment power according to claim 1 or claim 2, wherein the particles are particles having electromagnetic wave shielding performance, and the concealment power is electromagnetic wave shielding power.

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