Printing ink color matching method based on ink layer thickness control

Abstract

The invention provides a printing ink color matching method based on ink layer thickness control. The printing ink color matching method comprises the following steps: (1) preparing a target ink thickness gradient sample page and obtaining the reflectivity of the target ink thickness gradient sample page; (2) measuring the reflectivity of the actual printing sample of the target ink, calculating the reflectivity difference, and obtaining the printing pressure of the gradient sample of the primary color ink during proofing according to the printing pressure and the reflectivity difference; (3) preparing gradient sample pages of primary color ink on the white paper and the black paper respectively, obtaining the reflectivity of the gradient sample pages, and measuring the paper reflectivity of each sample page; (4) calculating the product of the absorption of the primary color ink and the thickness of the ink layer, and the product of the scattering coefficient and the thickness of the ink layer; (5) measuring the reflectivity of a target ink printing specimen and the reflectivity of paper in the specimen; and (6) calculating the formula of the target ink. The influence of the thickness of the ink layer is considered in the formula model, and the consistency of the thickness of the ink layer of the proofing sample and the thickness of the ink layer of the original printing target ink sample is effectively controlled.

Description

Technical Field

[0001] The invention relates to the technical field of printing ink color matching, and in particular to a printing ink color matching method based on ink layer thickness control. Background Art

[0002] In the printing, coating and other industries, companies often only purchase a few basic color inks (i.e., base color inks), and then use these base color inks to mix and produce other color inks required for production. At present, the prior art proposes to directly use the Kubelka-Munk (KM) model to calculate the formula of unknown inks. These ink color matching methods based on the KM model believe that the reflectivity of the ink layer is only related to the absorption coefficient and the scattering coefficient, and has nothing to do with the thickness of the ink layer. In actual applications, it is found that the color difference of the inks configured by these methods is large or small and lacks stability. Summary of the invention

[0003] The purpose of the present invention is to provide a printing ink color matching method based on ink layer thickness control to solve the above technical problems.

[0004] The technical solution of the present invention is a printing ink color matching method based on ink layer thickness control, comprising the following steps:

[0005] Step (a), prepare the target ink, prepare thickness gradient samples of the target ink with different ink layer thicknesses according to the range of printing pressure, and the printing pressure is p l , l = 1, 2, ..., L, measure the reflectivity of the thickness gradient sample of the target ink

[0006] Step (ii): prepare a sample of the actual printing of the target ink and measure its reflectivity r t (λ), calculate the reflectivity difference between the thickness gradient sample of the target ink and the actual printed product

[0007] Step (iii), taking printing pressure pl as the horizontal coordinate, reflectivity difference As the ordinate, a fitting curve is obtained; the printing pressure corresponding to the minimum reflectivity difference in the fitting curve is selected as the printing pressure p when the base color ink gradient sample is proofed d ;

[0008] Step (iv), select m kinds of primary color inks, and prepare gradient samples of the primary color inks on white and black paper respectively; the percentage of the primary color ink in the jth gradient sample of the i-th primary color ink is expressed as 1≤i≤m;

[0009] Step 5:

[0010] The reflectance of the gradient sample obtained in step (iv) is measured. The reflectance of the gradient sample on the white paper is The reflectances of the gradient samples on black paper are Measure the reflectivity of each sample paper, the reflectivity of white paper Black paper reflectivity Calculate the product k of the absorption coefficient of the jth gradient sample of the i-th base color ink and the ink layer thickness j,i (λ)h, and the product of the scattering coefficient and the ink layer thickness s j,i (λ)h;

[0011] Step (six), calculate the product K of the absorption of the base color ink and the ink layer thickness i (λ)h, and the product of the scattering coefficient and the ink layer thickness S i (λ)h; measure the reflectivity r of the target ink printed sample T (λ) and the reflectivity r of the paper in the sample P (λ); according to the absorption of the base color ink and the product of the ink layer thickness K i (λ)h, scattering coefficient and ink layer thickness product S i (λ)h, reflectivity r of the sample printed with the target ink T (λ) and the reflectivity r of the paper in the sample P (λ) Calculate the target ink formula.

[0012] As a further preference of the above scheme:

[0013] In the step (a), the printing pressure is gradually increased in grades from a minimum value to a maximum value according to the range of the printing pressure, and the target ink is spread on the same paper to obtain samples of the target ink with different ink layer thicknesses.

[0014] As a further preference of the above scheme:

[0015] The reflectivity difference between the thickness gradient sample of the target ink and the actual printed product in step (ii) The calculation formula is:

[0016]

[0017] As a further preference of the above scheme:

[0018] In the step (iv) of preparing a gradient sample of the base color ink on white paper: selecting the base color ink, mixing it with the diluent according to different percentages, and printing it at a pressure of p d Download n gradient samples on white paper.

[0019] As a further preference of the above scheme:

[0020] In the step (iv) of preparing a gradient sample of the base color ink on the black paper: select the base color ink, mix it with the diluent according to different percentages, and print it at a printing pressure of p d Download n gradient samples on black paper.

[0021] As a further preference of the above scheme:

[0022] The product k of the absorption coefficient of the jth gradient sample of the i-th primary color ink and the ink layer thickness in the step (V) is j,i (λ)h, and the product of the scattering coefficient and the ink layer thickness s j,i The calculation formula for (λ)h is:

[0023]

[0024] As a further preference of the above scheme:

[0025] The product K of the absorption of the base color ink and the ink layer thickness in step (six) i (λ)h, and the product of the scattering coefficient and the ink layer thickness S i The calculation formula for (λ)h is:

[0026]

[0027]

[0028] In the formula, i represents the base color ink index, j represents the index of the gradient sample, and j=1, 2, ...n.

[0029] As a further preference of the above scheme:

[0030] The formula calculation formula of the target ink is:

[0031]

[0032] The beneficial effects of the present invention are as follows: the influence of ink layer thickness is taken into account in the formulation model, and the consistency of the ink layer thickness of the proofing sample and the ink layer thickness of the original printing target ink sample is effectively controlled to improve the stability and accuracy of the difference between the predicted target spectrum and the target spectrum, as follows:

[0033] In practical applications, the ink configuration method must be implemented under the premise of considering the thickness control of the target ink sample. Only when the thickness of the ink layer is large enough and the light flux incident on the ink layer is completely absorbed, the relationship in the KM theory that "the reflectivity of the ink layer is only related to the absorption coefficient and the scattering coefficient, and has nothing to do with the thickness of the ink layer" is established; otherwise, the reflectivity of the ink layer is also affected by the thickness of the ink layer. At this time, even if the ink layer of the proofing sample is thick enough during the configuration process, it cannot effectively solve the problems existing in the aforementioned prior art. In actual configuration, the actual printed product is usually used as the target ink sample. However, the ink layer of the actual printed product (especially the offset printed product) is relatively thin. The thin ink layer may cause the amount of diluent in the formula estimation to be much higher than the actual amount. When the configured ink is used in actual printing, the color on the sample will be lighter than the target ink print, resulting in a larger color difference.

[0034] Based on the foregoing, the present invention proposes a printing ink color matching method based on ink layer thickness control, in which the influence of ink layer thickness is taken into account in the formula model, and the stability and accuracy of the difference between the predicted target spectrum and the target spectrum are improved by effectively controlling the consistency of the ink layer thickness of the proofing sample and the ink layer thickness of the original printed target ink sample, which is of great significance to the development and application of the automatic ink color matching system. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] The accompanying drawings are used to provide a further understanding of the present invention and constitute a part of the specification. Together with the embodiments of the present invention, they are used to explain the present invention and do not constitute a limitation of the present invention. In the accompanying drawings:

[0036] Figure 1 In the embodiment of the present invention, for the 2# target formula, the formula is calculated by the method based on the KM model in the prior art, the ink is mixed according to the formula, and the spectral reflectivity of the color development sample on the white cardboard is calculated by the method of the present invention, and the ink is mixed according to the formula, the spectral reflectivity of the color development sample on the white cardboard is calculated, and the spectral reflectivity of the 2# original target ink color development sample is calculated. DETAILED DESCRIPTION

[0037] The present invention is further described below in conjunction with specific embodiments. These embodiments are only used to illustrate the present invention and are not used to limit the scope of the present invention. Now, in conjunction with the drawings of the specification, the structural features of the present invention are described in detail. In the embodiment, the spectrophotometer model is X-Rite's SP64, the measurement wavelength range is 400-700nm, the wavelength interval is 10nm, the base color ink and the diluent are yellow, magenta, and cyan of the folding-resistant series of Shengweike, respectively, the paper is white cardboard specially used for cigarette packs, the color development instrument model is Caibang flagship NB600, and the printing pressure range is 0-1700N. It should be noted that the present invention is not limited to the above-mentioned inks, papers and measuring equipment, and is also applicable to other types and brands of inks, papers and measuring equipment.

[0038] Example

[0039] This embodiment provides a printing ink color matching method based on ink layer thickness control, comprising the following steps:

[0040] Step (a), prepare target ink, prepare target ink thickness gradient samples with different ink layer thicknesses according to the range of printing pressure, and the printing pressure is p l , l = 1, 2, ..., L, measure the reflectivity of the target ink thickness gradient sample Specifically include:

[0041] (1) Prepare target ink thickness gradient samples

[0042] First, according to the printing pressure range of the color developing instrument, the printing pressure of the color developing instrument is adjusted to the minimum value, the target ink is taken, and the target ink is developed on the paper by using the color developing instrument to obtain the thinnest ink layer target ink thickness gradient sample, and the printing pressure of this sample is recorded as p1; in the practice of printing enterprises, the printed products are continuous, and the aforementioned target ink can be the ink matched for the last printing, which is saved as the target ink matched for this time; in this embodiment, the minimum printing pressure starts from 5N, that is, p1=5N, and the target ink is the 2# target ink in the comparative example; in this step, the paper is preferably a white card;

[0043] Then, within the adjustable range of the printing pressure of the colorimeter, the printing pressure is gradually increased, one level at a time, and the colorimeter is used to sequentially apply equal amounts of target ink on paper of the same specifications to obtain target ink thickness gradient samples with different ink layer thicknesses from thin to thick, as well as the corresponding reflectivity of the samples. and printing pressure p l , l=1,2,…,L; in this embodiment, L=20, that is, for every increase of 5N printing pressure, a sample sheet with target ink thickness gradient is printed;

[0044] (2) Measure the reflectivity of the target ink thickness gradient sample

[0045] The reflectivity of each target ink thickness gradient sample was measured using a spectrophotometer SP64 and recorded as λ represents the wavelength, λ∈[400,700], and the wavelength interval is 10nm;

[0046] Step (ii): Measure the reflectivity of the actual printed product of the target ink

[0047] The reflectivity of the actual printed product of the target ink was measured using a spectrophotometer SP64. t (λ), λ represents the wavelength, λ∈[400,700], and the wavelength interval is 10nm;

[0048] The aforementioned actual printed matter refers to: a sample printed with the target ink in actual printing production;

[0049] Step (iii): Calculate the reflectivity difference between the target ink thickness gradient sample and the target ink actual print

[0050] Calculate the reflectivity difference between the target ink thickness gradient sample and the target ink actual print The calculation is as follows (1):

[0051]

[0052] Where l = 1, 2, ..., L

[0053] Step (iv), obtaining reflectivity difference With printing pressure p l The changing curve

[0054] Printing pressure p l is the horizontal axis, reflectivity difference The least square method is used to fit the curve of printing pressure and reflectivity p = a1 (e t ) 2 +a2(e t )+a3, where a1, a2 and a3 are 0.2064, -30.13445 and 1103.4556 respectively, p and e t represent the printing pressure and reflectivity difference, respectively;

[0055] Step 5: Obtain proofing printing pressure

[0056] Find the minimum reflectivity difference point in the curve of step (iv), and calculate the printing pressure at this point using the gradient descent method based on the fitting curve obtained in step (iv), that is, the pressure corresponding to the minimum spectral difference in the curve, as the printing pressure p for subsequent base color ink gradient sample proofing d In this embodiment, p d =73N;

[0057] In this embodiment, the purpose of steps (1) to (5) is to obtain the printing pressure, so as to control the thickness of the ink displayed on the paper by the color display instrument, that is, to obtain how much printing pressure is required when the color display instrument is used to display the color on the paper, so that the color of the ink thickness can be consistent with the color of the actual printed sample of the target ink;

[0058] Step (six): Prepare base color ink gradient sample on white paper

[0059] Select m kinds of primary color inks and prepare primary color ink gradient samples on white paper; the percentage of primary color ink in the jth gradient sample of the i-th primary color ink is expressed as 1≤i≤m;

[0060] In this embodiment, three Siegwerk primary color inks are used, namely yellow ink, magenta ink and cyan ink, so m=3; the details are as follows:

[0061] In this embodiment, the index of the yellow ink is 1, that is, i=1, that is, the percentage of the yellow primary color ink in the jth gradient sample of the yellow primary color ink is When preparing a gradient sample of yellow base ink on white paper: select yellow base ink, mix it with diluent, and print it at a pressure of p d The color is spread on white paper; n yellow base ink gradient samples are prepared according to different mixing percentages of yellow base ink and diluent; assuming that the percentage of yellow base ink in the jth gradient sample of the yellow base ink is The diluent is and Where 1≤j≤n. The yellow base color ink is mixed with a diluent to prepare 12 yellow base color ink gradient samples; in this embodiment, when the base color ink is yellow base color ink, n is 12, The values ​​are 3.25%, 12.5%, 25%, 37.5%, 50%, 60%, 70%, 75%, 80%, 85%, 90%, 95%;

[0062] When preparing magenta base color ink gradient samples on white paper: repeat step (six), 12 magenta base color ink gradient samples on white paper, n is 12, The values ​​are 3.25%, 12.5%, 25%, 37.5%, 50%, 60%, 70%, 75%, 80%, 85%, 90%, 95%;

[0063] When preparing cyan primary color ink gradient samples on white paper: repeat step (six) to prepare 12 cyan primary color ink gradient samples on white paper, n is 12, The values ​​are 3.25%, 12.5%, 25%, 37.5%, 50%, 60%, 70%, 75%, 80%, 85%, 90%, 95%;

[0064] It should be noted that the method of the present invention has no restrictions on the order and quantity of selecting the primary color inks; in this embodiment, three colors, yellow, magenta and cyan, are selected as the primary color inks;

[0065] Step (VII): Prepare base color ink gradient sample on black paper

[0066] Using the same m kinds of primary color inks as in step (six), a primary color ink gradient sample is prepared on black paper. The percentage of the primary color ink in the jth gradient sample of the i-th primary color ink is expressed as 1≤i≤m;

[0067] In this step, three Siegwerk primary color inks are also used, namely yellow ink, magenta ink and cyan ink, so m=3; in this embodiment, the index of yellow ink is 1, that is, i=1, that is, the percentage of yellow primary color ink in the jth gradient sample of yellow primary color ink is The details are as follows:

[0068] When preparing a yellow base color ink gradient sample on black paper: Use yellow base color ink, mix with diluent, and print at a pressure of p d The next color is developed on black paper; n base color ink gradient samples are prepared according to different mixing percentages of base color ink and diluent; assuming that the base color ink percentage in the jth gradient sample of the yellow base color ink is The diluent is and The yellow base color ink is mixed with a diluent to prepare 12 yellow base color ink gradient samples; in this embodiment, when the base color ink is yellow base color ink, n is 12, The values ​​are 3.25%, 12.5%, 25%, 37.5%, 50%, 60%, 70%, 75%, 80%, 85%, 90%, 95%;

[0069] When preparing magenta base color ink gradient samples on black paper: repeat the above step (IX) to prepare 12 magenta base color ink gradient samples on black paper, n is 12, The values ​​are 3.25%, 12.5%, 25%, 37.5%, 50%, 60%, 70%, 75%, 80%, 85%, 90%, 95%;

[0070] When preparing cyan primary color ink gradient samples on black paper: repeat the above step (IX) to prepare 12 cyan primary color ink gradient samples on black paper, n is 12, The values ​​are 3.25%, 12.5%, 25%, 37.5%, 50%, 60%, 70%, 75%, 80%, 85%, 90%, 95%;

[0071] It should be noted that the method of the present invention has no restrictions on the order and quantity of selecting the primary color inks; in this embodiment, three colors, yellow, magenta and cyan, are selected as the primary colors.

[0072] Step (eight), calculating the product of the absorption coefficient of the mixture of the base color ink and the diluent and the ink layer thickness, and the product of the scattering coefficient and the ink layer thickness

[0073] The reflectance of the base color ink gradient samples obtained in steps (six) and (seven) was measured by a spectrophotometer. The reflectance of the base color ink gradient samples on white paper was respectively The reflectance of the base color ink gradient samples on black paper are Use a spectrophotometer to measure the reflectivity of the paper sample and the reflectivity of white paper Black paper reflectivity The product of the absorption coefficient and the ink layer thickness of each primary color ink, and the product of the scattering coefficient and the ink layer thickness are calculated using a formula;

[0074] The product k of the absorption coefficient of the jth gradient sample of the i-th base color ink and the ink layer thickness is j,i (λ)h, and the product of the scattering coefficient and the ink layer thickness s j,i The calculation formula for (λ)h is:

[0075]

[0076] In formula (2), λ represents the wavelength, λ∈[400,700], the wavelength interval is 10nm, and h represents the thickness of the ink layer in the sample;

[0077] Step (IX): Calculate the product of the absorption of the base color ink and the ink layer thickness, and the product of the scattering coefficient and the ink layer thickness

[0078] The absorption coefficient of the base color ink and the product of the ink layer thickness K are calculated using the sequential quadratic programming method through the following formula relationship: i (λ)h, and the product of the scattering coefficient and the ink layer thickness S i (λ)h;

[0079] The above formula relationship is as follows:

[0080]

[0081] In step (10), i represents the primary color ink index, and in the embodiment, represents three primary color inks of yellow, magenta and cyan respectively, j represents the index of the gradient sample, and j=1, 2, ... n, n=12;

[0082] Step (XI): measuring the reflectivity of the target ink print

[0083] Use a spectrophotometer to measure the reflectivity r of the target ink print T (λ), and the reflectivity of the paper in the printed matter r P (λ);

[0084] In this embodiment, λ represents the wavelength λ∈[400,700], and the wavelength interval is 10nm;

[0085] Step (12): Calculate the formula of the target ink

[0086] According to the results of steps (IX) to (XI), the target ink formula is calculated using the following formula, that is, the percentage of each base color ink in the target ink. The percentage of the base color ink in the target ink in the formula is calculated as follows:

[0087]

[0088] The percentage of diluent in the above formula is calculated as follows:

[0089]

[0090] In formula (4), are the predicted ratios calculated for the yellow primary ink, the magenta primary ink, and the cyan primary ink, i.e., the aforementioned formula; if The percentage of diluent is Verification of the Example

[0091] The method of the above embodiment is verified below, including the following steps:

[0092] Step (a), preparation of target ink

[0093] Using the calculated % yellow base ink, Percentage of base color ink, % cyan base ink and The percentage of diluent is fully mixed to obtain the target ink;

[0094] Step (ii): Prepare target ink test sample

[0095] Using a colorimeter, the target ink prepared in step (i) is spread on white cardboard at a printing pressure of 73N;

[0096] Step (iii), measuring the reflectivity of the target ink test sample;

[0097] Use SP64 to measure the sample prepared in step (2) to obtain the reflectivity

[0098] Step (iv), calculating the chromaticity values ​​of the printing target ink sample and the proofing target ink sample;

[0099] Using the three-stimulus calculation formula, the reflectivity r of the printed target ink sample is T (λ), calculate the CIELab chromaticity value under D65 standard light source and 2 degree field of view, i.e. L, a, b;

[0100] Using the three-stimulus calculation formula, the reflectivity of the printed target ink sample Calculate the CIELab chromaticity value under D65 standard light source and 2 degree field of view

[0101] Step (V), calculating the color difference between the printing target ink sample and the proofing target ink sample;

[0102] Using CIE1976DE color difference formula, calculate the chromaticity value L, a, b and The color difference between .

[0103] Comparative Example

[0104] In order to verify the effectiveness of the method of the present invention, two target colors 1# and 2# were selected in this comparative example, and the ink formula was obtained by the method in the prior art patent "A printing ink color matching method based on KM theory, publication number CN113910796A", and the ink formula was obtained by comparing the color matching method of the present invention. The color difference of the formulas obtained by the two methods was compared, and the comparison results are shown in Table 1 below.

[0105] Table 1 Comparison of formulation and color difference

[0106]

[0107]

[0108] According to the data in Table 1, in the color matching of target color 1#, the color difference between the predicted spectrum of the formula calculated by the existing patent method and the original target measurement spectrum is 2.4226, while the color difference using the method of the present invention is 0.6901, which is reduced by 71.51%; the color difference between the actual proofing measurement of the formula calculated by the existing patent method and the original target measurement spectrum is 3.0245, while the color difference using the method of the present invention is 0.9731, which is reduced by 67.83%. Therefore, in the color matching of target color 1#, the color matching accuracy of the method of the present invention is significantly higher than that of the existing patent method.

[0109] Further, according to the data in Table 1, in the color matching of target color 2#, the color difference between the predicted spectrum of the formula calculated by the existing patent method and the original target measurement spectrum is 2.4128, while the spectrum difference using the method of the present invention is 0.7365, which is reduced by 69.48%; the color difference between the actual proofing measurement of the formula calculated by the existing patent method and the original target measurement spectrum is 2.9052, while the color difference using the method of the present invention is 0.8516, which is reduced by 70.69%. In the color matching of target color 2#, the color matching accuracy of the method of the present invention is significantly higher than that of the existing patent method.

[0110] Combination Figure 1 , Figure 1The formula calculated for the target ink 2# in the embodiment and the spectral reflectance effect for mixing are: the formula is calculated by the method based on the KM model of the existing patent, the ink is mixed according to the formula, the color is displayed on white cardboard, and the actual proofing sample is obtained, and the spectral reflectance is measured; the formula is calculated by the method of the present invention, and the ink is mixed according to the formula, the color is displayed on white cardboard, and the actual proofing sample is obtained, and the spectral reflectance is measured; and the spectral reflectance of the original target ink 2# after the color is displayed on white paper and the actual proofing sample is obtained. It can be seen from the figure that the actual proofing spectrum curve of the formula obtained by the method based on the KM model has a deviation of about 0.05 from the actual proofing spectrum of the target ink in the 430-480nm and 570-700nm bands; the actual proofing spectrum curve of the formula obtained by the patent is closer to the curve of the actual proofing spectrum of the target ink, and the two reflectance spectra basically overlap, reflecting that the formula calculated by the patent can reproduce the color of the target ink, indicating that the patent can accurately calculate the formula composition of any ink.

[0111] The present invention has been described in detail with reference to the aforementioned embodiments. For those skilled in the art, it is still possible to modify the technical solutions described in the aforementioned embodiments, or to replace some of the technical features therein by equivalents. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A printing ink color matching method based on ink layer thickness control, characterized in that: The following steps are involved: Step (a), prepare the target ink, prepare thickness gradient samples of the target ink with different ink layer thicknesses according to the range of printing pressure, and the printing pressure is p l , l = 1, 2,, L, measure the reflectivity of the thickness gradient sample of the target ink Step (ii): prepare a sample of the actual printing of the target ink and measure its reflectivity r t (λ), calculate the reflectivity difference between the thickness gradient sample of the target ink and the actual printed product Step (iii), taking printing pressure pl as the horizontal coordinate, reflectivity difference As the ordinate, the fitting curve is obtained; Select the printing pressure corresponding to the minimum reflectivity difference in the fitting curve as the printing pressure p for the base color ink gradient sample. d ; Step (iv), select m kinds of primary color inks, and prepare gradient samples of the primary color inks on white and black paper respectively; the percentage of the primary color ink in the jth gradient sample of the i-th primary color ink is expressed as 1≤i≤m; Step 5: The reflectance of the gradient sample obtained in step (iv) is measured. The reflectance of the gradient sample on the white paper is The reflectances of the gradient samples on black paper are Measure the reflectivity of each sample paper, the reflectivity of white paper Black paper reflectivity Calculate the product k of the absorption coefficient of the jth gradient sample of the i-th base color ink and the ink layer thickness j,i (λ)h, and the product of the scattering coefficient and the ink layer thickness s j,i (λ)h; Step (six), calculate the product K of the absorption of the base color ink and the ink layer thickness i (λ)h, and the product of the scattering coefficient and the ink layer thickness S i (λ)h; measure the reflectivity r of the target ink printed sample T (λ) and the reflectivity r of the paper in the sample P (λ); according to the absorption of the base color ink and the product of the ink layer thickness K i (λ)h, scattering coefficient and ink layer thickness product S i (λ)h, reflectivity r of the sample printed with the target ink T (λ) and the reflectivity r of the paper in the sample P (λ) Calculate the target ink formula.

2. The printing ink color matching method based on ink layer thickness control according to claim 1, characterized in that: In the step (a), the printing pressure is gradually increased in grades from a minimum value to a maximum value according to the range of the printing pressure, and the target ink is spread on the same paper to obtain samples of the target ink with different ink layer thicknesses.

3. The printing ink color matching method based on ink layer thickness control according to claim 1, characterized in that: The reflectivity difference between the thickness gradient sample of the target ink and the actual printed product in step (ii) The calculation formula is:

4. The printing ink color matching method based on ink layer thickness control according to claim 1, characterized in that: In the step (iv) of preparing a gradient sample of the base color ink on white paper: selecting the base color ink, mixing it with the diluent according to different percentages, and printing it at a pressure of p d Download n gradient samples on white paper.

5. The printing ink color matching method based on ink layer thickness control according to claim 1, characterized in that: In the step (iv) of preparing a gradient sample of the base color ink on the black paper: select the base color ink, mix it with the diluent according to different percentages, and print it at a printing pressure of p d Download n gradient samples on black paper.

6. The printing ink color matching method based on ink layer thickness control according to claim 1, characterized in that: The product k of the absorption coefficient of the jth gradient sample of the i-th primary color ink and the ink layer thickness in the step (v) is j,i (λ)h, and the product of the scattering coefficient and the ink layer thickness s j,i The calculation formula for (λ)h is:

7. The printing ink color matching method based on ink layer thickness control according to claim 1, characterized in that: The product K of the absorption of the base color ink and the ink layer thickness in step (six) i (λ)h, and the product of the scattering coefficient and the ink layer thickness S i The calculation formula for (λ)h is: In the formula, i represents the base color ink index, j represents the index of the gradient sample, and j=1, 2, n.

8. The printing ink color matching method based on ink layer thickness control according to claim 1, characterized in that: The formula calculation formula of the target ink is:

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