Covering power evaluation method

Abstract

Provided is a simpler method for evaluating hiding power. A hiding power evaluation method for evaluating the hiding power of a particle-containing body including particles to be subjected to hiding power evaluation, the method including: a step for evaluating the hiding power of a particle-containing body on the basis of the transmission amount (I) of electromagnetic waves of the particle-containing body and a base material and the transmission amount (I0) of electromagnetic waves of a particle-free body and a base material that do not include particles but have the same composition as the particle-containing body; the absorbance (Abs) of the electromagnetic wave is calculated by formula (1). Formula (1): Abs =-log (I / I0).

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 more particularly to a method for evaluating the hiding power of a coating film using a pigment as particles. Background Art

[0002] Conventionally, the hiding power of coatings containing particles such as pigments has been evaluated. For example, the degree to which a coating covers a base color (hiding power) can be measured by measuring the tristimulus values ​​of a coating applied on a white or black base and dried, as in JIS K 5600-4-1:1999K (ISO / FDIS 6504-3:1998).

[0003] In addition, since metallic effect pigments are opaque, it is believed that hiding power depends on the area covered by the metallic effect pigment on the coating surface. Therefore, the water diffusion area (WCA) specified in JIS K 5906:1998 (Non-Patent Document 2) is used as an indicator of hiding power of a coating film using metallic effect pigments.

[0004] The hiding power of the coating film is adjusted by repeatedly adjusting the pigment concentration in the coating or the coating film thickness and visually evaluating the hiding power.

[0005] Prior art literature

[0006] Non-patent literature

[0007] Non-patent document 1: JIS K 5600-4-1: 1999K (ISO / FDIS 6504-3: 1998)

[0008] Non-patent document 2: JIS K 5906: 1998 Summary of the invention Problems to be solved by the invention

[0009] However, the method of Non-Patent Document 1 requires coating paper using a dedicated hiding power test paper.

[0010] The method of Non-Patent Document 2 cannot be applied to pigments that do not float in water. It is also very time-consuming.

[0011] In the existing technology of adjusting hiding power, it is necessary to prepare a coating method for each pigment, which is inefficient. In addition, for new pigments, it is necessary to investigate the coating method.

[0012] Regarding hue, there are Hunter 1948 (L, a, b) color space, CIE 1976 (L * , a * , b *) Although various measurement methods such as color space and gloss can be compared with standard values, the mainstream is still to evaluate hiding power relatively by comparing with standard samples.

[0013] The present invention does not use black and white hiding power test paper, but instead performs absolute and relative evaluation of hiding power by measuring the visible light transmission intensity of coated plates and coated papers such as coated paper (coated paper) and PET film, which are used for color tone evaluation to confirm quality. In this way, the time required for evaluation and the amount of coating used can be reduced.

[0014] Therefore, an object of the present invention is to provide a simpler method for evaluating hiding power. Means of solving the problem

[0015] The present inventors have conducted intensive research to solve the above-mentioned problems. As a result, as described in detail in the examples, the present inventors have found that the absorbance obtained based on the ratio of the light transmittance of the coating film containing the pigment and the coating film without the pigment is proportional to the water surface diffusion area (WCA). That is, according to the present invention, as a substrate, no special test paper is used, and the hiding power of the coating film can be evaluated by measuring the absorbance of the coating film. In addition, according to the present invention, even if the pigment that does not float in water cannot obtain the WCA, a value proportional to the WCA can be obtained to evaluate the hiding power. In addition, it can be seen that the evaluation method of the present invention can evaluate the hiding power not only when the pigment is included in the coating film formed on the substrate, but also when it is mixed in the substrate. In addition, it is further found that by measuring the absorbance of electromagnetic waves other than visible light, the shielding power of electromagnetic waves can be evaluated. Based on the above viewpoints of the present inventors, the hiding power evaluation method, quality management method and quality assurance method of the present invention have the following structure.

[0016] The hiding power evaluation method followed by the present invention is a method for evaluating the hiding power of a particle-containing body containing particles of the hiding power evaluation object, which includes the following steps: based on the transmission amount (I) of electromagnetic waves of the particle-containing body and the substrate, and the transmission amount (I0) of electromagnetic waves of a non-particle-containing body and the substrate that does not contain particles and has the same composition as the particle-containing body, the absorbance (Abs) of the electromagnetic wave is calculated by the following formula (1).

[0017] Formula (1) Abs=-log(I / I0)

[0018] This eliminates the need to use a hiding power test paper as a substrate, and provides a simpler hiding power evaluation method.

[0019] In addition, below, the absorption degree (Abs) of electromagnetic waves may be referred to as absorbance (Abs) when the electromagnetic waves are visible light.

[0020] The hiding power evaluation method according to the present invention preferably includes the step of calculating the value of (absorbance (Abs)) / (concentration of particles containing particle bodies (C)).

[0021] The hiding power evaluation method of the present invention preferably includes the following steps: calculating the thickness (L) of the particle-containing body having the desired hiding power based on the absorbance of the electromagnetic wave of the particle-containing body (Abs), the concentration of the particles (C) and the absorption coefficient of the electromagnetic wave of the particles (ε) by the following formula (2).

[0022] Formula (2) L = Abs / (ε×C)

[0023] The hiding power evaluation method followed by the present invention preferably includes the following steps: using the following formula (3), based on the absorbance of electromagnetic waves of the particle-containing body (Abs), the thickness of the particle-containing body (L) and the absorption coefficient of electromagnetic waves of the particles, the concentration (C) of the particle-containing body having the desired hiding power is calculated.

[0024] Formula (3) C = Abs / (ε×L)

[0025] The hiding power evaluation method followed by the present invention preferably includes the following steps: based on the electromagnetic wave absorbance (Abs) of the particle-containing body with the desired hiding power, the electromagnetic wave absorbance (Abs1) of the first particle-containing body as particles containing only the first particles, and the electromagnetic wave absorbance (Abs2) of the second particle-containing body as particles containing only the second particles, 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 with the desired hiding power are calculated by the following formula (4).

[0026] Formula (4) Abs1×X+Abs2×(1-X)=Abs(0≤X≤1)

[0027] In the hiding power evaluation method followed by the present invention, it is preferred that the particles are contained in a coating film formed on a substrate, or are mixed in the substrate.

[0028] In the hiding power evaluation method followed by the present invention, it is preferred that the particles are pigments.

[0029] In the hiding power evaluation method followed by the present invention, it is preferred that the electromagnetic wave is visible light.

[0030] In the hiding power evaluation method followed by the present invention, it is preferred that the particles are particles having electromagnetic wave shielding properties, and the hiding power is electromagnetic wave shielding power.

[0031] In the hiding power evaluation method followed by the present invention, it is preferred that the electromagnetic wave is an electromagnetic wave other than visible light, and the hiding power is an electromagnetic wave shielding power.

[0032] The quality management method followed by the present invention includes the following steps: a step of determining the absolute hiding power or the relative hiding power by the above-mentioned hiding power evaluation method; and a step of performing quality management of the product based on the absolute hiding power or the relative hiding power.

[0033] The quality assurance method followed by the present invention includes the following steps: a step of determining the absolute hiding power or the relative hiding power by the above-mentioned hiding power evaluation method; and a step of ensuring the quality of the product based on the absolute hiding power or the relative hiding power. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 This is a graph showing the relationship between the absorbance (Abs) and the pigment concentration (C) of the pigment-containing coating films of Examples 1 to 7.

[0035] Figure 2 This is a graph showing the relationship between the value obtained by dividing the absorbance (Abs) of the pigment-containing coating films of Examples 1 to 7 by the pigment concentration (C) and the water diffusion area (WCA) of each pigment.

[0036] Figure 3 This is a graph showing the relationship between the absorbance (Abs) and the pigment concentration (C) of the pigment-containing coating films of Examples 8 to 14.

[0037] Figure 4 This is a graph showing the relationship between the value obtained by dividing the absorbance (Abs) of the pigment-containing coating films of Examples 8 to 14 by the pigment concentration (C) and the water surface diffusion area (WCA) of each pigment.

[0038] Figure 5 This is a graph showing the relationship between the absorbance (Abs) and the pigment concentration (C) of the pigment-containing coating films of Examples 15 to 21.

[0039] Figure 6 This is a graph showing the relationship between the value obtained by dividing the absorbance (Abs) of the pigment-containing coating films of Examples 15 to 21 by the pigment concentration (C) and the water surface diffusion area (WCA) of each pigment.

[0040] Figure 7 This is a graph showing the relationship between the absorbance (Abs) and the pigment concentration (C) of the pigment-containing coating films of Examples 23 and 24. DETAILED DESCRIPTION

[0041] Hereinafter, the hiding power evaluation method of the present invention will be described in detail with reference to specific examples. Note that the present invention is not limited to the embodiments described below, and various modifications can be made without departing from the technical concept of the present invention.

[0042] The hiding power evaluation method followed by the present invention is a method for evaluating the hiding power of a particle-containing body containing particles of the hiding power evaluation object, which includes the following steps: based on the transmission amount (I) of electromagnetic waves of the particle-containing body and the substrate, and the transmission amount (I0) of electromagnetic waves of a non-particle-containing body and the substrate that does not contain particles and has the same composition as the particle-containing body, the absorbance (Abs) of the electromagnetic wave is calculated by the following formula (1).

[0043] Formula (1) Abs=-log(I / I0)

[0044] As one embodiment, a hiding power evaluation method will be described in which the hiding power evaluation object is a coating film containing a pigment and the hiding power thereof with respect to visible light is evaluated.

[0045] First, a coating containing pigment particles is applied to a substrate (hereinafter, also referred to as a "base") and dried to form a pigmented coating film. Next, a non-pigmented coating film (hereinafter, also referred to as a "blank" or "control") having the same composition as the pigmented coating film is formed on the substrate or base, except that the non-pigmented particles are removed. The pigmented coating film is an example of a particle-containing body, and the non-pigmented coating film is an example of a non-particle-containing body.

[0046] As the paint containing the pigment, for example, a known paint in which an aluminum pigment (slurry) is dispersed in nitrocellulose (nitrocellulose) paint, acrylic paint, or water-based paint can be used. The correlation coefficient between Abs and WCA described later varies depending on the affinity between the resin component in the paint and the pigment, so it is preferred to use nitrocellulose paint having a wide affinity.

[0047] The substrate is not limited, and coated plates and coated papers such as coated paper (coated paper) and PET films, which are used for color tone evaluation to check quality, can be used.

[0048] Regarding the method of making the coating film, the same method is used for the pigmented coating film and the non-pigmented coating film, and the conditions such as the paint, coating film thickness, coating plate, coating method, drying temperature, drying method, etc. are kept consistent.

[0049] The coating is performed, for example, by applying the coating on the substrate by a doctor blade method. For example, a commercially available nitrocellulose (nitrocellulose) lacquer is applied by a doctor blade method on a PET film or coated paper (coated paper) to obtain a particle-containing body and a particle-free body.

[0050] For example, a 2 mil (50.8 μm) scraper can be used to orient the pigment, but a 6 mil, 9 mil, etc. scraper can also be used. The coating obtained by coating with 9 mils is 4.5 times thicker than the coating obtained by coating with 2 mils, but due to the disordered orientation of the pigment and the influence of secondary reflection, the absorbance Abs may be slightly less than 4.5 times.

[0051] The pigment-containing coating film thus obtained contains particles of the pigment. In addition to the coating film, the particle-containing body can also be produced by mixing particles of the pigment or the like into a base material.

[0052] For the obtained particle-containing body (containing pigment coating) and non-particle-containing body (not containing pigment coating), measure the transmittance I and I0 of the wavelength of light for evaluating hiding power, and calculate the absorbance (Abs) based on the formula (1) Abs = -log (I / I0). The transmittance I and I0 of light can be measured by a known method. There is no limitation as long as the transmittance of the wavelength of light for evaluating hiding power can be measured. As an example, a spectrophotometer CM-5 (Konica Minolta) can be used. The transmittance measurement requires that the light intensity is strong enough, or the detection capability of the detection device for detecting light passing through the coating is high enough. When using a spectrophotometer, the brightness (L * value) can be regarded as the amount of light transmitted.

[0053] When evaluating the hiding power of visible light, if the substrate or base is not transparent to visible light, the Spectrophotometer CM-5 may not be able to measure the transmittance. In this case, you can also use a white LED light source and an illuminance meter to measure the transmittance.

[0054] When particles with electromagnetic wave shielding properties are used as particles, the hiding power can also be evaluated for electromagnetic waves other than visible light. There is no limitation on the wavelength of the electromagnetic wave for evaluating the hiding power. For example, it can also be applied to long waves, medium waves, short waves, ultrashort waves, microwaves, radio waves, infrared rays, visible light, ultraviolet rays, EUV, X-rays, and gamma rays. When evaluating the hiding power of electromagnetic waves other than visible light, the absorbance (Abs) of the electromagnetic wave of the wavelength for evaluating the hiding power is also calculated based on the formula (1) Abs = -log (I / I0). To measure the transmittance of electromagnetic waves, it is sufficient to select a light source that can irradiate electromagnetic waves of the required wavelength and an electromagnetic wave detector corresponding to the wavelength.

[0055] The absorbance (Abs) value obtained in the above manner reflects the hiding power of particles such as pigments, as described in detail in the Examples.

[0056] By doing so, it is not necessary to use a hiding power test paper as a substrate. In addition, a simpler hiding power evaluation method can be provided.

[0057] In addition, it is preferable to include a step of calculating the value of (absorbance (Abs)) / (concentration of particles containing particles (C)). The present inventors have found that the value of (absorbance (Abs)) / (concentration of particles containing particles (C)) is proportional to WCA (water surface diffusion area). Therefore, by calculating the value of (absorbance (Abs)) / (concentration of particles containing particles (C)), for particles that do not float on water, even if WCA is not measured, the hiding power of the particles can be evaluated in the same manner as when WCA is used.

[0058] The relationship between the thickness (L) of the particle-containing body (pigment-containing coating film), the absorption coefficient (ε) of electromagnetic waves (visible light) of the particles (pigment), and the concentration (C) of the particles (pigment) in the particle-containing body (pigment-containing coating film) is absorbance (Abs) = ε × L × C (Lambert-Beer's law). Therefore, the thickness (L) of the particle-containing body having a desired hiding power can be calculated 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).

[0059] Formula (2) L = Abs / (ε×C)

[0060] Furthermore, the concentration (C) of the particle-containing body having a desired hiding power can be calculated based on the electromagnetic wave absorbance (Abs) of the particle-containing body, the thickness (L) of the particle-containing body, and the electromagnetic wave absorption coefficient (ε) of the particles by the following formula (3).

[0061] Formula (3) C = Abs / (ε×L)

[0062] In the hiding power evaluation method followed by the present invention, for a mixed particle body in which two particles are mixed, the weight ratio of each particle required to obtain a desired hiding power can be calculated. That is, based on the electromagnetic wave absorbance (Abs) of the particle-containing body having the desired hiding power, the electromagnetic wave absorbance (Abs1) of the first particle-containing body containing only the first particle as particles, and the electromagnetic wave absorbance (Abs2) of the second particle-containing body containing only the second particle as particles, the weight ratio (X) of the first particle and the weight ratio (1-X) of the second particle in the mixed particle body containing the first particle and the second particle having the desired hiding power can be calculated by the following formula (4).

[0063] Formula (4) Abs1×X+Abs2×(1-X)=Abs(0≤X≤1)

[0064] The quality management method followed by the present invention includes the following steps: a step of determining the absolute hiding power or the relative hiding power by the above-mentioned hiding power evaluation method; and a step of performing quality management of the product based on the absolute hiding power or the relative hiding power.

[0065] The quality assurance method followed by the present invention includes the following steps: a step of determining the absolute hiding power or the relative hiding power by the above-mentioned hiding power evaluation method; and a step of ensuring the quality of the product based on the absolute hiding power or the relative hiding power.

[0066] Example

[0067] Hereinafter, the hiding power evaluation method of the present invention will be described in detail with reference to specific examples. The present invention is not limited to the embodiments described below, and various modifications can be made without departing from the technical concept of the present invention.

[0068] (Examples 1 to 7)

[0069] As the pigment, aluminum pigments (slurry) A to G described in Table 1 were used. The weights of the slurries shown in a to c in Table 2 were measured and commercially available nitrocellulose lacquer was added respectively to make the total amount 50 g. Then, the mixture was uniformly stirred with a planetary mixer to prepare a coating. Average particle size D 50 The WCA of each pigment was measured based on Non-Patent Document 2.

[0070]

Table 1

[0071]

[0072]

Table 2

[0073]

[0074] The obtained coatings were applied onto PET films using a 2 mils (50.8 μm) applicator and dried at room temperature to obtain pigmented coatings of each example. Nitrocellulose lacquer was applied as a blank using a 2 mils applicator and dried at room temperature to prepare non-pigmented coatings.

[0075] The pigmented coating film and the non-pigmented coating film produced on the PET film were cut into about 6 cm squares together with the PET film to form test pieces. The L* value of the test piece containing the pigmented coating film and the L* value of the test piece without the pigmented coating film were measured using the transmitted light intensity measurement unit of the spectrophotometer CM-5 (manufactured by Konica Minolta Co., Ltd.), and the absorbance Abs was obtained by treating (L* value of the pigmented coating film) / (L* value of the non-pigmented coating film) as the transmittance. The results are shown in Table 3.

[0076]

Table 3

[0077]

[0078] Based on this result, the absorbance Abs is plotted against the pigment concentration C and displayed in Figure 1 In. By Figure 1 It can be seen that, regardless of the type of pigment, the relationship between absorbance Abs and pigment concentration C can be approximated by a straight line passing through the origin. In addition, Table 3 shows the values ​​of the slope Abs / C obtained by the least squares method of these straight lines passing through the origin.

[0079] Corresponding to the above Abs / C, the WCA of each pigment is plotted and displayed in Figure 2 The slope obtained by the least square method is 1538.8. From this result, equation (5) can be derived.

[0080] Depend on Figure 2 It is understood that in the metallic effect pigment, since the ratio Abs / C is proportional to WCA, the absorbance Abs reflects the hiding power.

[0081] (Examples 8 to 14)

[0082] In the same manner as in Example 1, a coating having a pigment concentration C shown in Table 4 was prepared for each aluminum pigment (slurry) A to G. The prepared coating was applied to coated paper using a 2 mils (50.8 μm) applicator and dried at room temperature to obtain a pigmented coating film of each example. Separately, a nitrocellulose varnish used for preparing the coating was directly applied to coated paper using a 2 mils applicator and dried at room temperature to prepare a non-pigmented coating film.

[0083] For each pigmented coating and non-pigmented coating produced, a white LED with a front illuminance of 345,000 lux was irradiated, and a commercially available illuminance meter was used to measure the light transmittance I of each sample coating and the light transmittance I0 of the standard coating. From the light source to the illuminance meter, a cylindrical black ABS resin was used to avoid light leakage and mixing of external light sources. The device structure is as follows: about 40 mm from the light source to the coating, and about 15 mm from the coating to the surface of the illuminance meter. The absorbance Abs of each sample coating calculated based on the measurement results is shown in Table 4.

[0084]

Table 4

[0085]

[0086] Based on this result, the absorbance Abs is plotted against the pigment concentration C and displayed in Figure 3 In. By Figure 3 It can be seen that in the coating film using coated paper, regardless of the pigment, the relationship between absorbance Abs and pigment concentration C can be approximated by a straight line passing through the origin. In addition, the values ​​of the slope Abs / C obtained by the least squares method of these straight lines passing through the origin are shown in Table 5.

[0087]

Table 5

[0088]

[0089] Corresponding to the above Abs / C, the WCA of each pigment is plotted and displayed in Figure 4 In. By Figure 4 It can be seen that when opaque coated paper is used as the substrate, the ratio of Abs / C is proportional to WCA, and the hiding power can be evaluated. The slope obtained by the least squares method is 776.5. Based on this result, formula (6) can be derived.

[0090] (Examples 15 to 21)

[0091] Each coating material was adjusted so that each pigment had a pigment concentration C shown in Table 6. Using each obtained coating material, absorbance Abs was measured 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.

[0092]

Table 6

[0093]

[0094] Based on the results, the absorbance Abs is plotted against the pigment concentration C and displayed in Figure 5 In. By Figure 5 It can be seen that in the coating film using coated paper, regardless of the pigment, the relationship between absorbance Abs and pigment concentration C can be approximated by a straight line passing through the origin. In addition, the values ​​of the slope Abs / C obtained by the least squares method of these straight lines passing through the origin are shown in Table 7.

[0095]

Table 7

[0096]

[0097] Corresponding to the above Abs / C, the WCA of each pigment is plotted and displayed in Figure 6 The slope obtained by the least square method is 224.6. Based on this result, equation (7) can be derived.

[0098] Depend on Figure 6 It can be seen that even when the coating amount of the coating material is changed, the hiding power can be evaluated if the measurement is performed under the same conditions.

[0099] Formula (5) WCA=1538.8×Abs / C

[0100] (When a test coating film is prepared and the transmittance is measured as in Examples 1 to 7)

[0101] Formula (6) WCA = 776.5 × Abs / C

[0102] (When a test coating film is prepared and the transmittance is measured as in Examples 8 to 14)

[0103] Formula (7) WCA = 224.6 × Abs / C

[0104] (When a test coating film is prepared and the transmittance is measured as in Examples 15 to 21)

[0105] As described above, even for a hydrophilic pigment whose WCA cannot be obtained by the method of non-patent document 2, if a coating is formed on a PET film and coated paper and the absorbance Abs and the pigment concentration C are measured, an estimated WCA can be obtained based on the above correlation coefficient. Specifically, the estimated WCA value of the aluminum pigment EMR-B5680 (Toyo Aluminum Slurry) coated with silica, which cannot obtain WCA by the method of non-patent document 2, is 24000 cm 2 / g (weight per 1g of aluminum). The coating and coating film preparation and the measurement of absorbance Abs were carried out in the same manner as in Examples 15 to 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 cm 2 / g).

[0106]

Table 8

[0107]

[0108] (Example 22)

[0109] (Adjustment of pigment hiding power)

[0110] Using a sample pigment having an absorbance Abs at a pigment concentration C, based on the absorbance Abs0 at a pigment concentration C0 of a target pigment having a desired hiding power, by giving a pigment concentration C' = C × Abs0 / Abs that is equivalent to the hiding power at the concentration C0 of the target pigment, a coating having the same hiding power as the target pigment can be prepared using the sample pigment (C0 and C may be equal or different).

[0111] As pigments, aluminum pigments (slurry) A, H, and I described in Table 9 were used, and the slurry was measured in a manner of 0.7 g of each pigment, and commercially available nitrocellulose lacquer was added in a manner of making the total amount 50 g. Then, the coating was uniformly stirred with a planetary mixer. The prepared coating was applied to coated paper using a 9mils (228.6μm) film applicator, and dried at room temperature to obtain each sample coating. In addition, the nitrocellulose lacquer used to prepare the coating was directly applied to the coated paper using a 9mils film applicator, and dried at room temperature to prepare the target coating with the desired hiding power. The absorbance Abs of aluminum pigments A, H, and I and the relative absorbance of the target pigment to the absorbance Abs were obtained by the same measurement method as in Example 15. The relative absorbance is shown in Table 9.

[0112]

Table 9

[0113]

[0114] When the weight ratio of the aluminum pigment H is X and the weight ratio of the aluminum pigment I is (1-X), the following formula (8) can be established.

[0115] Formula (8) (Relative absorbance of the coating containing pigment H to the target coating) × X + (Relative absorbance of the coating containing pigment I to the target coating) × (1-X) = 1 (0≤x≤1)

[0116] The situation of Example 22 is

[0117] 1.34×X+0.69×(1-X)=1.00

[0118] X=0.48.

[0119] Based on the pigment weight ratio calculated by formula (8), aluminum pigment (slurry) H and I were mixed to prepare a mixed pigment. The mixed pigment was collected in such a way that the total weight of the pigments mixed in the paint was 0.7 g, and commercially available nitrocellulose lacquer was added so that the total amount reached 50 g. Then, the mixture was uniformly stirred with a planetary mixer to prepare a paint. The prepared paint was applied to coated paper with a 9 mils (228.6 μm) film applicator and dried at room temperature to obtain a sample coating.

[0120] Separately, nitrocellulose lacquer used to make a coating was directly applied to coated paper using a 9 mils applicator and dried at room temperature to produce a non-pigmented coating film.

[0121] By the same measurement method as in Example 15, the absorbance Abs of the mixed pigment (slurry) was obtained, and the relative absorbance to the absorbance Abs of the target pigment was calculated. As a result, it was confirmed that the relative absorbance value to the target pigment A was 1.02, which was equivalent to the hiding power of the target pigment. Thus, for example, the variation in hiding power between the production batches of the pigment can be suppressed.

[0122] (Example 23)

[0123] 30.0 kg of blue pigment, 75.0 kg of HAWS and 3.0 kg of dispersant as shown in Table 10 were crushed by a bead mill to obtain a slurry with a pigment concentration of 27.8%. The obtained slurry was used instead of the aluminum pigment to measure the absorbance Abs of the pigment concentration C in each coating shown in Table 10 in the same manner as in Example 8. The results are shown in Tables 10 and Figure 7 middle.

[0124]

Table 10

[0125]

[0126] (Example 24)

[0127] 4.6 kg of red pigment shown in Table 10, 25.1 kg of HAWS and 0.5 kg of dispersant were crushed by a bead mill to obtain a slurry as a pigment, and the absorbance Abs was measured in the same manner as in Example 23. The results are shown in Tables 10 and Figure 7 middle.

[0128] Depend on Figure 7 It can be seen that, although the value of Abs / C is not constant for color pigments, a calibration curve that can approximate it can be created.

[0129] The obtained calibration curve can be used for hiding power adjustment, etc., as in studies using aluminum pigments.

[0130] The embodiments and examples disclosed above are illustrative in all aspects and should be considered non-restrictive. The scope of the present invention is not limited to the embodiments and examples above, but includes all modifications and variations within the meaning and scope equivalent to the scope of the claims.

Claims

1. A method for evaluating hiding power, which is a method for evaluating the hiding power of a particle-containing body containing particles of a hiding power evaluation object, wherein: Including the following processes: Based on the electromagnetic wave transmission amount I of the particle-containing body and the substrate and the electromagnetic wave transmission amount I0 of the non-particle-containing body and the substrate having the same composition as the particle-containing body except for the particles, the electromagnetic wave absorbance Abs is calculated by the following formula (1): Formula (1) Abs=-log(I / I0).

2. The hiding power evaluation method according to claim 1, wherein: Including the following processes: The value of (the absorbance Abs) / (the concentration C of the particles in the particle-containing body) is calculated.

3. The hiding power evaluation method according to claim 1, wherein: Including the following processes: The thickness L of the particle-containing body having a desired hiding power is calculated based on the absorbance Abs of the electromagnetic wave of the particle-containing body, the concentration C of the particles, and the absorption coefficient ε of the electromagnetic wave of the particles by the following formula (2): Formula (2) L = Abs / (ε×C).

4. The hiding power evaluation method according to claim 1, wherein: Including the following processes: The concentration C of the particles in the particle-containing body having a desired hiding power is calculated by the following formula (3) based on the electromagnetic wave absorbance Abs of the particle-containing body, the thickness L of the particle-containing body, and the electromagnetic wave absorption coefficient ε of the particles. Formula (3) C = Abs / (ε×L).

5. The hiding power evaluation method according to claim 1, wherein: Including the following processes: Based on the electromagnetic wave absorbance Abs of the particle-containing body having the desired hiding power, the electromagnetic wave absorbance Abs1 of the first particle-containing body containing only the first particles as particles, and the electromagnetic wave absorbance Abs2 of the second particle-containing body containing only the second particles as particles, 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 the desired hiding power are calculated by the following formula (4): Formula (4): Abs1×X+Abs2×(1-X)=Abs, where 0≤X≤1.

6. The hiding power evaluation method according to any one of claims 1 to 5, wherein: The particles are contained in a coating film formed on the substrate, or are mixed in the substrate.

7. The hiding power evaluation method according to claim 6, wherein: The particles are pigments.

8. The hiding power evaluation method according to claim 7, wherein: The electromagnetic wave is visible light.

9. The hiding power evaluation method according to claim 6, wherein: The particles are particles having electromagnetic wave shielding properties, and the covering power is electromagnetic wave shielding power.

10. The hiding power evaluation method according to claim 9, wherein: The electromagnetic waves are electromagnetic waves other than visible light, and the covering power is electromagnetic wave shielding power.

11. A method for quality management of a product, wherein: Including the following processes: A step of specifying absolute hiding power or relative hiding power by the hiding power evaluation method according to claim 6; and A process for performing quality management of a product based on the absolute hiding power or the relative hiding power.

12. A method for ensuring the quality of a product, wherein: Including the following processes: A step of specifying absolute hiding power or relative hiding power by the hiding power evaluation method according to claim 6; and A process for ensuring the quality of a product based on the absolute hiding power or the relative hiding power.

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