JPH046746B2 - - Google Patents

Description

[Detailed description of the invention]

<Industrial Application Field> The present invention relates to a method for preparing a colorant using a computer color matching method that combines color measurement technology and computer technology, and particularly relates to a method for preparing a colorant using a computer color matching method that combines color measurement technology and computer technology. The present invention aims to provide a new method for preparing colorants that solves the problems of the computer color matching method. <Prior art> In coloring factories for dyeing, plastic coloring, etc., or in factories manufacturing or using paints, inks, etc., the preparation (color matching) of these colorants is an extremely important operation. was carried out by highly skilled technicians. The technicians who carry out this color matching require an extremely high level of skill, and their processing capacity is not necessarily high.The productivity of coloring work is limited by the number of these technicians and their processing capacity. It was hot. Therefore, with the goal of streamlining this color matching work, so-called computer color matching (hereinafter referred to as CCM) combines color measurement technology and computer technology.
) is becoming popular. In this CCM, the scattering coefficient (S) and extinction coefficient specific to the colorant contained in the colored layer are
Color matching calculations are performed based on the ratio (K/S) of (K). For example, taking the case of color matching using three types of dyes as an example, the outline of the calculation is as follows. First, the reflectance R 1 λ, R 2 λ, R 3 λ of the fiber dyed with the unit concentration of colorants ₁ , ₂ , and ₃ for each wavelength (λ) is calculated.
Measure. Measure the reflectance R ₀ λ of the fiber itself and substitute it into the Kubelka-Munk function equation (1) to calculate the ratio of the extinction coefficient and scattering coefficient of the dyed material and the fiber itself at each wavelength (for example, at intervals of 10 to 20 nm). Find (K/S). K/S=(1-R) ² /2R...(1) If the K/S of the fiber itself is (K/S) ₀ , the wavelength λ
The following equation (2) holds approximately. (K/S) _n =C ₁ (K/S) ₁ +C ₂ (K/S) ₂ +C ₃ (
K/S) ₃ + (K/S) ₀ ...(2) (where (K/S) _n indicates the (K/S) value of the mixed dye, and C ₁ , C ₂ , C ₃ are the dyes The staining concentrations of 1, 2, and 3 are (K/S) ₁ , (K/S) ₂ , (K/S) ₃ ,
From the above equation (1), which shows the (K/S) value per unit density of dyes 1, 2, and 3, the reflectance of the mixed dye is: The tristimulus value calculated from this reflectance R _n
From Xm, Ym, Zm, the target color tristimulus values Xs, Ys,
Color matching was performed by finding C ₁ , C ₂ , and C ₃ that were equal to Zs. This method is called the Metameritsukumatsuchi method.
The objective is to match the target color with the calculated color of the colorant mixture under a specific light source. These tristimulus values were proposed as a color display method in the field of color science (CIE in 1931), and are currently widely used. This is the tristimulus value of X, Y, and Z that takes into account the visual sensitivity at the wavelength (λ), and the spectral energy of the light source.
From Pλ and the spectral reflectance ρλ of the colored material, Color is expressed numerically by the value given by λ・Pλ・dλ. Here, λ, λ, and λ are spectral tristimulus values (also called color matching functions) unique to the human eye, and the light source spectral energy Pλ takes different values depending on the type of light source. A unique value is taken for each light source, such as the D ₆₅ light source, A light source, C light source, and F light source, which are generally used as standard light sources. The value of the spectral reflectance ρλ of the colored material is a value measured by a spectrophotometer. Therefore, the determination of color difference based on these tristimulus values also depends on the spectral energy Pλ of the light source.
, each light source has its own tristimulus value for each colored object. On the other hand, C ₁ , C ₂ , and C ₃ are determined so that the reflectance R _n and the reflectance of the target color are equal at each wavelength.
The so-called isometric method is also known. This method attempts to perform color matching so that the spectral reflectance curves of the dyed material and the color sample perfectly match, and is a color matching method that does not cause any color difference even if the light source changes. <Problems to be Solved by the Invention> Currently, the most widely used method in computer color matching is the metamerit matching method described above. This method makes the color difference between the target color and the target color 0 under a certain light source, such as D ₆₅ or A light source, so the colors appear to match under a certain light source, but those specific light sources Because they do not universally exist in nature, their colors often appear different under familiar light sources, which is a cause of decreasing reliability in CCM. This is because the spectral reflectances at each wavelength do not match, and is called conditional matching. Therefore, according to Metameritsukumatsuchi method,
When performing CCM, the actual situation is to find out from the results the mixing ratio of colorants with a low degree of metamerism, and then use that. In CCM based on the metameritism method, the color difference is set to 0 under a specific light source, so there are cases where the reverse metameritism is further increased. On the other hand, in the isometric match method, the spectral reflectance for each wavelength is made equal, but in color matching of a mixture of several color materials, the spectral reflectance is made equal for all wavelength ranges. That was almost impossible. Therefore, in reality, the combination of each coloring material is determined by calculating the difference in reflectance for each wavelength as close to 0 as possible. However, in this case, the formulation was determined in a way that ignored the spectral sensitivity characteristics of the human eye, so it involved the same problem as the metameric combination. As described above, the above-mentioned methods used in conventional CCM have various problems and are still not sufficient. The present invention is a new system that solves these problems.
This paper aims to provide a method for blending color materials using CCM. <Means for Solving the Problems> That is, the present invention provides a method for determining the blending ratio of colorants using a computer color matching method _.
Spectral tristimulus values (λ, λ, λ) at spectral wavelength (λ) for the absolute value ρabs (λ) of the difference between (λ) and the spectral reflectance ρcal (λ) obtained from the calculated colorant formulation It is an object of the present invention to provide a method for preparing a colorant, which is characterized in that the colorant mixing ratio is determined when the value obtained by multiplying the load factor obtained from the weight factor and the cumulative value thereof becomes the minimum. When looking at the relationship between the spectral reflectance curve and the luminous sensitivity, in the visible limit range of 400 nm or around 700 nm, the spectral reflectance curve obtained from the calculation of the colorant preparation with respect to the spectral reflectance curve of the target color Even if the reflectance deviates greatly, it will have little effect on the color difference in luminous sensitivity, but on the contrary, it will have a very large effect on the intermediate range of the visible region. Therefore, by multiplying the absolute value ρ _abs (λ) of the difference in spectral reflectance at each wavelength by a weighting coefficient consisting of the spectral tristimulus values, we can determine the colorant with a small color difference in terms of visual sensitivity of the human eye. This allows the adjustment ratio to be determined. The spectral tristimulus values (also referred to as color matching functions) are defined in JIS Z8701, and these values can be used as they are or values based on this can be used. JIS
The spectral tristimulus values for each wavelength shown in Z8701 are as follows. Here the wavelength is 440n
m, the maximum peak of the stimulation amount is at 580 nm, and
The minimum peak is at 500nm, and further at 700n
At m, 680nm, and 400nm, the amount of stimulation is very small.
It can be seen that the amount of stimulation to the red, green, and blue (RGB) optic nerve of the human eye varies greatly depending on the wavelength. Value of wavelength λ (nm) color matching function Γ 400 0.082556 420 0.78398 Γ 440 2.11834 460 2.02 480 1.04761 Γ 500 0.5999 520 0.85152 540 1.2647 560 1.5934 Γ 580 1.78795 600 1.694 620 1.23564 640 0.62292 660 0.2259 Γ 680 0.06377 Γ 700 0.015461 or less, The method for preparing the colorant according to the present invention will be specifically explained. First, using the case of mixing three types of color materials A, B, and C as an example, the reflectance of the color matching target color is ρ _Target , the reflectance of the calculated color is ρ _cal , and the absolute value of the difference is Δρ (= |ρ _cal −ρ _Target |), the amount of change in reflectance per unit amount of coloring material is ∂ρ/∂C, and the amount of change in the blending ratio of each coloring material to be determined is ΔC _A , ΔC _B , ΔC _C , and from 400 nm to 700 nm. of
Using the case of 16 wavelengths at 20nm intervals as an example,
The following formulas are obtained. κ ₄₀₀ +Δρ ₄₀₀ =κ ₄₀₀・∂ρ ₄₀₀ ／∂C _A・ΔC _A +κ ₄₀₀
・∂ρ ₄₀₀ /∂C _B・ΔC _B +κ ₄₀₀・∂ρ ₄₀₀ /∂C _C・ΔC _C κ ₄₂₀・Δρ ₄₂₀ =κ ₄₂₀・∂ρ ₄₂₀ /∂C _A・ΔC _A +κ ₄₂₀
・∂ρ ₄₂₀ /∂C _B・ΔC _B +κ ₄₂₀・∂ρ ₄₂₀ /∂C _C・ΔC _C 〓 〓 〓 〓 κ ₇₀₀・Δρ ₇₀₀ =κ ₇₀₀・∂ρ ₇₀₀ /∂C _A・ΔC _A +κ ₇₀₀
・∂ρ ₇₀₀ /∂C _B・ΔC _B +κ ₇₀₀・∂ρ ₇₀₀ /∂C _C・ΔC _C (Here, κλ represents the weight coefficient consisting of the spectral tristimulus values for each wavelength, κλ=λ+λ+λ ) As shown above, the formula holds only for the number of measurement wavelengths,
ΔC A , ΔC _B , corresponding to the blended amounts of colorants A, B, _{and C} ,
Sixteen equations are created for the three unknowns of ΔC _C. If, for example, the least squares method is used to solve this equation, it can be summarized into the following three equations. ₇₀₀ 〓 〓 ⁼⁴⁰⁰ (κλ・∂ρλ／∂C _A )・κλ・Δρλ＝ ₇₀₀ 〓 〓 ⁼⁴⁰⁰ (κλ・∂ρλ／∂C _A ) ²・ΔC _A + ₇₀₀ 〓 〓 〓 ⁼⁴⁰⁰ (κλ・∂ ρλ／∂C _A )・(κλ・∂ρλ／∂C _B
)・ΔC _B + ₇₀₀ 〓 〓 〓 ⁼⁴⁰⁰ (κλ・∂ρλ／∂C _A )・(κλ・∂ρλ／∂C _C
)・ΔC _{C 700} 〓 〓 ⁼⁴⁰⁰ (κλ・∂ρλ／∂C _B )・κλ・Δρλ＝ ₇₀₀ 〓 〓 〓 ⁼⁴⁰⁰ (κλ・・∂ρλ／∂C _B )・(κλ・∂ρλ／∂
C _A )・ΔC _A + ₇₀₀ 〓 〓 ⁼⁴⁰⁰ (κλ・∂ρλ／∂C _B ) ²・ΔC _B + ₇₀₀ 〓 〓 〓 ⁼⁴⁰⁰ (κλ・∂ρλ／∂C _B )・(κλ・∂ρλ／ ∂C _C
)・ΔC _{C 700} 〓 〓 ⁼⁴⁰⁰ (κλ・∂ρλ／∂C _B )・κλ・Δρλ＝ ₇₀₀ 〓 〓 〓 ⁼⁴⁰⁰ (κλ・∂ρλ／∂C _C )・(κλ・∂ρλ／∂C _A
)・ΔC _A + ₇₀₀ 〓 〓 〓 ⁼⁴⁰⁰ (κλ・∂ρλ／∂C _C )・(κλ・∂ρλ／∂C _B
)・ΔC _B + ₇₀₀ 〓 〓 ⁼⁴⁰⁰ (κλ・∂ρλ／∂C _C ) ²・ΔC _C Solve these equations to find ΔC _A , ΔC _B , and ΔC _C , respectively. Then, from the obtained ΔC _A , ΔC _B , and ΔC _C , determine the blended amounts of coloring materials C _A , C _B , and C _C , calculate the calculated spectral reflectance from these blended amounts, and compare it with that of the target color. The accuracy of color matching can be predicted by Furthermore, the accuracy of color matching can be confirmed by determining the color difference from the target color from the determined spectral reflectance. If the color difference under a particular light source is extremely large, try changing to or adding another color material component and try again.
It is also possible to perform CCM to achieve more accurate color matching. In addition, the above-mentioned weight coefficient κλ is expressed as κλ=λ・Pλ・λ・
It can also be easily made into the form Pλ+λ・Pλ.
The above-mentioned weight coefficient that includes the spectral light source energy is effective when a visual color difference under a specific light source is particularly required, and the degree of metamerity is lower than that of the conventional metameritism matching method. This allows you to find the exact mixing ratio. <Example> Example 1 Determining the blending amount using yellow, red, blue, and black monochrome ink bases for a colored object (print sample) consisting of the spectral reflectance listed in Table 1-(2) as the target color are subjected to computer color matching using the conventional metameric matching method (referred to as XYZ Match) and the blending method based on the present invention (referred to as R% Match) to determine the blending amounts shown in Table 1-(1). The proportions in Table 1-(1) indicate the amount (%) of each monochromatic ink base alone; in actual printing ink, the remaining percentages include varnish, solvent, additives, etc.

[Table] The spectral reflectance was calculated based on the amount of preparation obtained from each method, and the results of comparison with that of the target color for each wavelength are shown in Table 1-(2).

[Table] The XYZ tristimulus values and color difference under the D ₆₅ light source and A light source were determined from each calculated spectral reflectance, and the results are shown in Table 1-(3). Further, the spectral reflectance curves based on the amounts of each compounded are shown in FIG.

【table】

[Table] From the above results, the conventional Metamerits Match method shows very good results with a color difference of 0 for both the D ₆₅ light source and the A light source. However, it can be seen that in the spectral reflectance curve shown in FIG. 1, there is a deviation from that of the target color. On the other hand, if the compounding method of the present invention is followed, the XYZ tristimulus values or the color difference based thereon will be different from that of the target color, but the spectral reflectance curve shown in Figure 1 will be different from that of the target color. It is possible to obtain similar results, and it is possible to perform color matching similar to the so-called isometric matching method. Example 2 As target colors, yellow, yellow,
The blending amounts of each monochrome ink base of red, blue, and black (different ink bases were used for yellow and blue than in Example 1) were determined in the same manner as in Example 1, and the results are shown in Table 2-(1). get.

[Table] The spectral reflectance was calculated based on the blended amount obtained by each method, and the results of comparison with that of the target color are shown in Table 2-(2).

【table】

[Table] From each reflectance in Table 2-(2), the same as Example 1
Calculate the XYZ tristimulus values and color difference, and show the results in Table 2.
- Shown in (3). Further, the respective spectral reflectance curves are shown in FIG.

[Table] From the above results, with the conventional Metameritsuku Match method, a blend amount with a color difference of 0 or close to 0 is obtained for both the D ₆₅ light source and the A light source, and when this calculation prescription is adopted, it is as if perfect color matching is achieved. It looks like it can be done. Both the D ₆₅ light source and the A light source have a blended amount with a large color difference. However, in the spectral reflectance curve in Figure 2,
It can be said that R% Match provides a reflectance curve closer to that of the target color. It is generally said that a color difference (ΔE) of 0.5 or less means that the visual color difference is hardly noticeable. Therefore, under the A light source, the value is as high as 1.00, indicating that there is a high possibility that problems will occur. Although the reflectance curve is closer to the target color than the conventional Metameritsukumachi method, the color difference under A light source is large, so it may be necessary to change to another ink base or perform CCM again by adding an additional ink. It can be said that this is what is shown. <Effects> As shown in the examples above, if the method of the present invention is followed, it is possible to perform larch mating that is approximated by the isometric mating method, and the problem of conditional matching in the conventional metameric mating method can be greatly overcome. It can be greatly improved. Therefore, when colorants are prepared based on the results obtained according to the method of the present invention, extremely excellent color matching with low metamerity can be achieved. In addition, in one method of the present invention, the absolute value of the deviation of the spectral reflectance curve ρ _abs (λ) is expressed as κλ=λ+λ+
It is multiplied by the weight coefficient determined by zλ, but if the purpose is to eliminate color difference under a specific light source, the weight coefficient is κλ = λ・Pλ+λ・Pλ+
It is also possible to use λ·Pλ (where Pλ represents the spectral light source energy of a specific light source) to achieve the desired color matching. Furthermore, by determining the color difference from the target color from the spectral reflectance curve corresponding to the blended amount obtained by the method of the present invention, the degree of color difference under a specific light source can be evaluated in advance. . Therefore, in the conventional Metameritsukumatsuchi method, the blending amount is determined so that the tristimulus values X, Y, and Z are each 0, and color matching accuracy can only be evaluated after mixing based on that amount. In the method of the present invention, by calculating the color difference between each light source, the suitability of the formulation can be predicted in advance, which can be said to be useful for improving the efficiency of the compounding work.

[Brief explanation of drawings]

FIG. 1 shows the respective spectral reflectance curves obtained by the printed sample made in Example 1, the conventional metameric match method, and the compounding method based on the present invention. FIG. 2 shows the spectral reflectance curves obtained by the printed sample of Example 2, the conventional metameric match method, and the compounding method according to the present invention.

Claims (1)

[Claims] 1. In a method of determining the blending ratio of colorants using a computer color matching method, the spectral reflectance ρ Target (λ) of the color matching target color is determined from the spectral reflectance ρ _Target (λ) and the calculated colorant blending ratio. Spectral reflectance ρ _cal
(λ), the absolute value of the difference ρ _abs (λ) is multiplied by the burden coefficient (κλ) found from the spectral tristimulus values (λ, λ, λ) at each spectral wavelength (λ), and this is integrated. 1. A method for preparing a coloring agent, characterized in that the mixing ratio of the coloring agent is determined at which the value of the coloring agent is minimized. 2. The method for preparing a colorant according to claim 1, wherein the weight coefficient (κλ) is expressed as κλ=λ+λ+λ. 3 The burden factor (κλ) is κλ=λ・Pλ+λ・
The method for preparing a coloring agent according to claim 1, which is represented by Pλ+λ·Pλ (where Pλ indicates spectral light source energy of a specific light source).