Method for flexographic printing color stability and copy consistency based on aluminum aerosol can

Abstract

The invention discloses a method for flexographic color stability and copy consistency based on an aluminum aerosol can, and the method comprises the steps: converting a design file into a spot color file before printing, and carrying out the printing plate linear compensation in an aluminum can flexographic printing plate link, thereby maintaining the stability and continuity of the image-text tone of the aluminum can, and improving the printing quality of the aluminum can. And the conditions that the shapes of the screen dots are not well kept during printing, large screen dots are easy to paste, small screen dots are easy to lose, and even 10% of screen dots cannot be printed are avoided, so that the printing quality is improved, and higher requirements of customers are met.

Description

Technical Field

[0001] The invention relates to a flexographic printing method for an aluminum aerosol can, in particular to a method based on color stability and copy consistency of flexographic printing for an aluminum aerosol can. Background Art

[0002] Aluminum aerosol cans are light and easy to carry. They are easy to use, safe and reliable, and are very popular among users. With the development of printing technology, people began to print patterns on aluminum cans, making aluminum cans not only protect the liquid in the cans, but also have a decorative effect in appearance to attract customers' attention and stimulate consumers' desire to buy.

[0003] Aluminum aerosol cans use a fully automatic aluminum can production line, which goes through the steps of stamping-trimming-washing-internal coating-primer-printing-varnish-neck closing, from raw aluminum blocks to printing and aluminum can molding. The printing part of the aluminum can production line belongs to curved surface flexographic printing, the printing speed is relatively high but the printing pressure cannot be too large (otherwise it will cause deformation or damage to the can), so the shape of the dots is not well maintained, large dots are easy to be blurred, small dots are easy to be lost, and even 10% of the dots may not be printed. Summary of the invention

[0004] In order to overcome the shortcomings of the prior art, the present invention provides a method for flexographic printing color stability and replication consistency based on aluminum aerosol cans.

[0005] The technical solution adopted by the present invention to solve the technical problem is:

[0006] A method for color stability and copy consistency of flexographic printing on aluminum aerosol cans, characterized by comprising the following steps:

[0007] S1. Pre-press color separation, convert the design graphics into spot color mode, and then embed it into the design file.

[0008] S2. Flexographic platemaking linear compensation:

[0009] S2.1: Create a linear test file in the prepress software, that is, a scale consisting of spot color blocks with dot values ​​of 0%, 3%, 5%, 10%, 20%, ... 90%, 95%, 100%.

[0010] S2.2: Calibrate the flexographic platemaking system and output the linear test file of the flexographic plate for each spot color printing unit.

[0011] S2.3: Print on the production line, use a spectrophotometer to measure the chromaticity value of 100% spot color blocks, adjust the ink volume of each spot color printing unit, and make the color difference between the measured value and the standard value ⊿ E ≤3,

[0012] S2.4: For each spot color printing unit, measure the dot density value of each gradation color block from 0 to 100%, with the gradation value as the horizontal coordinate and the dot density value as the vertical coordinate, to form a measurement curve between the gradation value and the corresponding dot density value. The dot density value range is: 0-D ∞ ,

[0013] S2.5: Perform linear compensation for the printing plate based on the dot density value, and retain the effective dot area ratio segment on the measurement curve. The gradation value range of this effective dot area ratio segment is: F start -F effective In order to match the input signal dot area rate 1-100%, the mapping algorithm is used to convert F start -F effective The density relationship corresponding to the ink volume is mapped to the range of 1-100%, and the linear mapping formula is as follows:

[0014] K=F effective -F start

[0015] F i =F start +K / 99*(i-1)i=1,2,……100

[0016] Where K is the effective dot area ratio, Fi is the output dot area ratio value corresponding to the input signal of 1%-100%,

[0017] S3. Printing.

[0018] Prepress color separation includes the following steps:

[0019] S1.1: Open the image file in the design drawing in Photoshop software. S1.2: Select the "Image-Mode-Grayscale" command to retain the grayscale level of the image in the image file.

[0020] S1.3: Select the "Image-Mode-Duotone" command. In the Duotone Options dialog box, select "Monotone" to use different shades of a single color to represent the grayscale levels of the image.

[0021] S1.4: Click on the ink color block to open the "color picker" and select the Pantone spot color in the color library. S1.5: Click on the ink curve to open the "Duotone Curve" panel to adjust the distribution and intensity of the color in the image according to the predetermined effect or load the curve data.

[0022] S1.6: Save the adjusted image file as an EPS format image file.

[0023] S1.7: In graphic design software such as Illustrator / CorelDRAW, insert the color-separated .EPS image file.

[0024] Also includes

[0025] S2.6: Determine the printing standard for flexo printing, determine the target values ​​of dot tone and the measured values ​​of dot tone corresponding to different tone values ​​of the original plate under the printing standard, and form a target curve and a secondary measurement curve, and integrate the target curve, the secondary measurement curve and the ideal linear curve into the same coordinate diagram.

[0026] S2.7: Calculation of the anti-compensation value F for flexographic printing E , which is calculated as follows:

[0027] Draw a vertical line from any point A on the target curve in the horizontal direction and intersect it with the secondary measurement curve at point B. Draw a vertical line from A and intersect it with the horizontal axis at point C. Then draw a vertical line from point B and intersect it with the ideal linear curve at point D. Then draw a horizontal line from point D and intersect it with line segment AC at point E. Point E is the compensation point for dot expansion. In the above, the curve where point B is located is the secondary measurement curve; the curve where point A is located is the target curve; the curve where point D is located is the ideal linear curve; the curve where point E is located is the dot expansion anti-compensation curve.

[0028] The beneficial effects of the present invention are as follows: the method performs plate linear compensation and dot enlargement counter-compensation in the aluminum can flexographic platemaking process, thereby maintaining the stability and continuity of the tone of the aluminum can image and text, avoiding the situation in which the shape of the dots is not well maintained, large dots are easy to be blurred, small dots are easy to be lost, and even 10% of the dots may not be printed, thereby improving the printing quality and meeting the higher demands of customers. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] The present invention is further described below in conjunction with the accompanying drawings and embodiments.

[0030] Figure 1 It is the coordinate diagram of a measurement curve;

[0031] Figure 2 It is a coordinate diagram that integrates the effective dot area ratio segments of the target curve, ideal linear curve, and quadratic measurement curve. DETAILED DESCRIPTION

[0032] The advantages and features of the present disclosure and its implementation methods will be explained by the following embodiments described with reference to the accompanying drawings. However, the present disclosure can be embodied in different forms and should not be interpreted as being limited to the embodiments set forth herein. On the contrary, these embodiments are provided so that the present disclosure will be comprehensive and complete, and will fully convey the scope of the present disclosure to those skilled in the art. In addition, the present disclosure is limited only by the scope of the claims.

[0033] The shapes, sizes, ratios, angles and numbers disclosed in the drawings for describing the embodiments of the present disclosure are only examples, and therefore the present disclosure is not limited to the details shown. Throughout this specification, the same reference numerals refer to the same elements. In the following description, when the detailed description of the relevant known functions or configurations is determined to be unnecessary to blur the focus of the present disclosure, the detailed description will be omitted. In the case of using "including", "having" and "comprising" described in this specification, other parts may be added unless "only" is used. Unless otherwise indicated, the terms in the singular may include plural forms.

[0034] When explaining an element, although not explicitly described, the element is understood to include a range of error.

[0035] When describing a positional relationship, for example, when the positional relationship is described as "on," "above," "below," and "adjacent to," unless "immediately" or "directly" is used, one or more parts may be arranged between two other parts.

[0036] When describing a time relationship, for example, when a time sequence is described as “after,” “subsequently,” “next,” and “before,” discontinuous cases may be included unless “just” or “directly” is used.

[0037] It should be understood that although the terms "first", "second", etc. may be used herein to describe various elements, these elements should not be limited by these terms. These terms are only used to distinguish one element from other elements. For example, a first element may be referred to as a second element, and similarly, a second element may be referred to as a first element without departing from the scope of the present disclosure.

[0038] As those skilled in the art can fully understand, the features of the different embodiments of the present disclosure can be coupled or combined with each other in part or in whole, and can cooperate with each other in various ways and be driven technically. The embodiments of the present disclosure can be performed independently of each other, or can be performed together in a mutually dependent relationship.

[0039] Reference Figure 1 , Figure 2 , this application includes the following steps,

[0040] S1. Pre-press color separation, convert the design graphics into spot color mode, and then embed it into the design file. Aluminum can printing is limited by printing technology and materials, and it is not suitable to use overprinting to produce rich color effects, so spot color is needed to replace multi-color overprinting. If the design graphics are only graphics and text, you can directly define the graphics fill color as printing in graphic design software such as Illustrator / CorelDRAW; if the design graphics contain images, first convert the images into CMYK mode in Photoshop software, and then embed them into the design file. The specific steps are as follows:

[0041] S1.1: Open the image file of the aluminum can design graphic in Photoshop software.

[0042] S1.2: Select the “Image-Mode-Grayscale” command to preserve the grayscale levels of the image.

[0043] S1.3: Select the "Image-Mode-Duotone" command, and in the Duotone Options dialog box, select "Monotone" to use different shades of a single color to represent the grayscale levels of the image.

[0044] S1.4: Click the color block of ink 1 to open the "Color Picker" and select the Pantone spot color in the color library.

[0045] S1.5: Click the curve of Ink 1 to open the "Duotone Curve" panel. You can adjust the distribution and intensity of the color in the image or load the curve data according to the effect.

[0046] S1.6: Save the adjusted image file as a .EPS format file.

[0047] S1.7: In graphic design software such as Illustrator / CorelDRAW, insert the color-separated .EPS image file to complete the prepress color separation.

[0048] S2, flexographic platemaking linear compensation, includes the following steps:

[0049] S2.1: Create a linear test file in the prepress software, that is, a scale consisting of spot color blocks with dot values ​​of 0%, 3%, 5%, 10%, 20%, ... 90%, 95%, 100%.

[0050] S2.2: Calibrate the flexographic platemaking system and output the linear test file of the flexographic plate for each spot color printing unit. For example, if an aluminum can production line has 9 color units, 9 linear test plates should be output.

[0051] S2.3: Print on the production line, use a spectrophotometer to measure the chromaticity value of 100% spot color blocks, i.e. Lab value, and adjust the ink volume of each spot color printing unit so that the color difference between the measured value and the standard value is ⊿E≤3.

[0052] S2.4: For each spot color printing unit, measure the dot density value of each gradation color block from 0 to 100%, with the gradation value as the horizontal axis and the dot density value as the vertical axis. The dot density value range is: 0-D ∞ , forming a measurement curve between the tone value and the corresponding dot density value. The tone value is also the dot area ratio.

[0053] like Figure 1 As shown in the figure, the entire measurement curve has three sections: OA, AB and BC. In the OA section, as the dot area rate increases, the output density value is always 0, that is, the small dots are lost; in the AB section, as the dot area rate increases, the density value of the printed output gradually increases. The dot area rate in this section is called the effective dot area rate section; in the BC section, as the dot area rate increases, the output density value remains unchanged and reaches the saturation density value.

[0054] S2.5: Perform linear compensation for the printing plate based on the dot density value, and retain the effective dot area ratio segment on the measurement curve. The gradation value range of this effective dot area ratio segment is: F start -F effective In order to match the input signal dot area rate 1-100%, the mapping algorithm is used to convert F start -F effective The density relationship corresponding to the ink volume is mapped to the range of 1-100%, and the linear mapping formula is as follows:

[0055] K=F effective -F start

[0056] F i =F start +K / 99*(i-1)i=1,2,……100

[0057] In the formula, K is the effective dot area ratio, F i The output dot area ratio values ​​corresponding to the input signals are 1%-100%.

[0058] In the flexographic printing process of aluminum cans, the ink will indeed increase the dots due to pressure during the transfer process from the ink roller to the flexographic printing plate and finally to the aluminum cans. This enlargement phenomenon is inevitable in the flexographic printing process of aluminum cans, but it can be controlled and optimized through a series of technical means. Therefore, as a further preferred step, it also includes:

[0059] S2.6: Determine the printing standard of flexo printing, determine the target values ​​of dot tone and the measured values ​​of dot tone corresponding to different tone values ​​of the original plate under the printing standard, and form a target curve and a secondary measurement curve. The secondary measurement curve is the dot tone value of each tone color block measured from 0 to 100% after linear plate making and printing. The target curve, the secondary measurement curve and the ideal linear curve are integrated into the same coordinate graph. The coordinate graph also uses the original tone value as the horizontal coordinate and the output dot tone value as the vertical coordinate, such as Figure 2 As shown,

[0060] S2.7: Calculation of the anti-compensation value F for flexographic printing E , which is calculated as follows:

[0061] Draw a vertical line from any point A on the target curve in the horizontal direction and intersect the effective dot area rate segment of the secondary measurement curve at point B. At the same time, draw a vertical line from A in the vertical direction and intersect the horizontal axis at point C. Then draw a vertical line from point B and intersect the ideal linear curve at point D. Then, draw a vertical line from point D and intersect the line segment AC at point E. Point E is the compensation point for dot enlargement. The tone value and dot density value corresponding to the compensation point are input into the device, thereby realizing the anti-compensation of dot enlargement in flexographic platemaking.

[0062] In the above, the curve where point A is located is the target curve; the curve where point B is located is the secondary measurement curve; the curve where point D is located is the ideal linear curve; and the curve where point E is located is the calculated dot gain anti-compensation curve.

[0063] S3, printing,

[0064] In order to achieve color stability and consistency in reproduction of aluminum cans, a primer of a certain thickness must be applied before printing to increase the adhesion between the aluminum can and the ink film layer; after printing, a layer of varnish must be applied to provide good protection for the ink film layer, so that the printing ink will not change color or fall off during high temperature and molding. On the other hand, since the ink on the aluminum can is printed on a smooth metal surface with no absorption capacity, the aluminum can needs to be dried at high temperature after printing.

[0065] To sum up, in order to achieve color stability and reproduction consistency of aluminum can flexo printing, which is essentially different from traditional paper offset printing, this application proposes that aluminum can flexo printing implement standardized steps in the three links of pre-press color separation, plate making dot compensation and printing, which can keep the dot presentation value stable and form a stable and standardized aluminum can flexo printing method.

[0066] The above is a detailed introduction to a method for color stability and reproduction consistency of flexographic printing on aluminum aerosol cans provided by an embodiment of the present invention. Specific examples are used herein to illustrate the principles and implementation methods of the present invention. The description of the above embodiments is only used to help understand the method of the present invention and its core idea. At the same time, for those skilled in the art, according to the idea of ​​the present invention, there will be changes in the specific implementation method and application scope. In summary, the content of this specification should not be understood as a limitation on the present invention.

Claims

1. A method for color stability and replication consistency of flexographic printing on aluminum aerosol cans, characterized by: The following steps are involved: S1. Pre-press color separation, convert the design graphics into spot color mode, and then embed it into the design file. S2. Flexographic platemaking linear compensation: S2.1: Create a linear test file in the prepress software, that is, a scale consisting of spot color blocks with dot values ​​of 0%, 3%, 5%, 10%, 20%, ... 90%, 95%, 100%. S2.2: Calibrate the flexographic platemaking system and output the linear test file of the flexographic plate for each spot color printing unit. S2.3: Print on the production line, use a spectrophotometer to measure the chromaticity value of 100% spot color blocks, adjust the ink volume of each spot color printing unit, and make the color difference between the measured value and the standard value ⊿ E ≤3, S2.4: For each spot color printing unit, measure the dot density value of each gradation color block from 0 to 100%, with the gradation value as the horizontal coordinate and the dot density value as the vertical coordinate, to form a measurement curve between the gradation value and the corresponding dot density value. The dot density value range is: 0-D ∞ , S2.5: Perform linear compensation for the printing plate based on the dot density value, and retain the effective dot area ratio segment on the measurement curve. The gradation value range of the effective dot area ratio segment is: F start -F effective In order to match the input signal dot area rate 1-100%, the mapping algorithm is used to convert F start -F effective The density relationship corresponding to the ink volume is mapped to the range of 1-100%, and the linear mapping formula is as follows: K=F effective -F start F i =F start +K / 99*(i-1)i=1,2,……100 Where K is the effective dot area ratio, Fi is the output dot area ratio value corresponding to the input signal of 1%-100%, S3, printing.

2. The method for color stability and replication consistency of flexographic printing on aluminum aerosol cans according to claim 1, characterized in that: Prepress color separation includes the following steps: S1.1: Open the image file in the design drawing in Photoshop software. S1.2: Select the "Image-Mode-Grayscale" command to preserve the grayscale levels of the image in the image file. S1.3: Select the "Image-Mode-Duotone" command. In the Duotone Options dialog box, select "Monotone" to use different shades of a single color to represent the grayscale levels of the image. S1.4: Click the ink color block to open the "Color Picker" and select the Pantone spot color in the color library. S1.5: Click the ink curve to open the "Duotone Curve" panel, adjust the distribution and intensity of the color in the image according to the desired effect or load the curve data. S1.6: Save the adjusted image file as an EPS format image file. S1.7: In graphic design software such as Illustrator / CorelDRAW, insert the color-separated .EPS image file.

3. The method for color stability and replication consistency of flexographic printing on aluminum aerosol cans according to claim 1, characterized in that: Also includes S2.6: Determine the printing standard for flexo printing, determine the target values ​​of dot tone and the measured values ​​of dot tone corresponding to different tone values ​​of the original plate under the printing standard, and form a target curve and a secondary measurement curve, and integrate the target curve, the secondary measurement curve and the ideal linear curve into the same coordinate diagram. S2.7: Calculation of the anti-compensation value F for flexographic printing E , which is calculated as follows: Draw a vertical line from any point A on the target curve in the horizontal direction and intersect it with the secondary measurement curve at point B. Draw a vertical line from A and intersect it with the horizontal axis at point C. Then draw a vertical line from point B and intersect it with the ideal linear curve at point D. Then draw a horizontal line from point D and intersect it with line segment AC at point E. Point E is the compensation point for dot expansion. In the above, the curve where point B is located is the secondary measurement curve; the curve where point A is located is the target curve; the curve where point D is located is the ideal linear curve; the curve where point E is located is the dot expansion anti-compensation curve.

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