A method for color matching between digital printing and flexographic printing

Abstract

The invention belongs to the technical field of printing color matching, specifically a method for color matching between digital printing and flexographic printing, which specifically includes the following steps: S1, daily maintenance and care of the machine, cleaning and maintenance of the parts that have a great impact on the printing quality; S2, using the online density meter provided by the machine to automatically calibrate the machine color; S3, doing preliminary preparations; since there are many uncontrollable factors in the printing equipment, the printing equipment is adjusted to a standard state; the beneficial effects of the invention are: color matching between digital printing and traditional printing, combining the △E advantage of digital printing with traditional printing, so that the printing quality is better, and the brush and process efficiency is effectively improved; the printing and proofing colors can be quickly matched; not only relying on the personal experience of the printing workers, the degree of automation is significantly improved, the printing efficiency is improved, the loss of paper and ink is greatly reduced, and the product competitiveness is improved.

Description

Technical Field

[0001] The invention relates to the technical field of printing color matching, in particular to a method for color matching between digital printing and flexographic printing. Background Art

[0002] In recent years, digital printing technology and its related industries have developed rapidly around the world. Digital printing equipment has been widely used. The continuous development and progress of digital printing technology has made digital printing more and more accepted and recognized by everyone. The image printing quality of some models of digital printing machines is already very close to traditional offset printing. Digital printing has replaced traditional offset printing in many printing market segments, meeting people's demand for personalized and diversified printed products. In China, digital printing is one of the important factors driving the development of the printing industry. Today, digital printing has ushered in a revolutionary era. Compared with flexographic printing, digital printing has incomparable advantages in on-demand printing and variable data printing. In fact, digital printing The core of is digital. Enterprises should effectively use the advantages of digital printing to realize a new business network and operation management model consisting of digital environment, digital resource integration, network transmission, pre-press design and processing, on-demand post-press, logistics network and channels, and business outlets, so as to greatly improve the productivity and competitiveness of enterprises; with the shortening of printing process, the reduction of printing cost and the diversity of printed products, how to achieve the same quality on the basis of quantitative change, and how to match the control of hue, brightness and saturation of printed products with flexographic printing, that is, how to make digital printing equipment and flexographic printing equipment consistent in output quality and color;

[0003] Problems with color management in digital printing Since the actual effect of the color management function of the digital printing machine is not ideal, the color of digital printing cannot match that of flexographic printing and cannot meet the color requirements of printing companies. Summary of the invention

[0004] In view of the problems existing in the existing method for color matching between digital printing and flexographic printing, the present invention is proposed.

[0005] Therefore, the purpose of the present invention is to provide a method for color matching between digital printing and flexographic printing, which solves the problem of color management of digital printing. Since the actual use effect of the color management function of the digital printing machine is not ideal, the color of digital printing cannot match that of flexographic printing and cannot meet the color requirements of printing companies.

[0006] To solve the above technical problems, according to one aspect of the present invention, the present invention provides the following technical solutions:

[0007] A method for color matching between digital printing and flexographic printing, specifically comprising the following steps:

[0008] S1. Carry out daily maintenance and upkeep of the machine, and clean and maintain the parts that have a great impact on printing quality;

[0009] S2, use the machine's built-in online densitometer to automatically calibrate the machine color;

[0010] S3, make preparations in advance; due to the many uncontrollable factors of printing equipment, adjust the printing equipment to the standard state; specifically, S31 adjusts the traditional printing equipment and printing conditions, S32 controls the solid density of printing, S33 adjusts the proportion of the dot enlargement curve, S34 controls the gray balance, S35 adjusts the printing uniformity, and S36 controls the printing speed;

[0011] S4, preparation for digital printing; specifically including S41 printer linearization calibration, S42 recording characteristic curves, S43 color conversion, S44 color matching;

[0012] S5, printed product inspection; specifically includes S51 test evaluation sample and S52 data measurement and result comparison.

[0013] As a preferred solution of the method for color matching between digital printing and flexographic printing described in the present invention, wherein: the S31 adjusts the traditional printing equipment and printing conditions: replaces the rubber blanket, selects a suitable backing, adjusts the pressure between the printing plates and the pH value of the fountain solution, and controls the ambient temperature and humidity; starts printing after preparation, using a color sequence of black / cyan / magenta / yellow.

[0014] As a preferred solution of the method for color matching between digital printing and flexographic printing described in the present invention, wherein: during the entire printing process, printing is performed in accordance with the printing standard and the printed sheets are printed flat, and the density values ​​of each solid primary color when the color difference is minimum are recorded to facilitate color control in actual printing production: the S33 dot enlargement curve ratio adjustment: in the pre-press workflow, the dot enlargement ratio is adjusted to make a corresponding anti-compensation curve for the printing plate to control the effect of dot enlargement on printing; in the plate making process, the dot enlargement curve provided in IS0 12647-2 is used to control traditional printing, and the mid-tone dot enlargement ratio is about 16%.

[0015] As a preferred solution of the method for color matching between digital printing and flexographic printing described in the present invention, the S34 gray balance control: the neutral gray part of the printed product can be controlled well to obtain a qualified printed product; in actual printing production, relevant color management software is used to produce the equipment characteristic curve of the printing machine, which is put into the CTP process to control the corresponding printing plate output, or the G7 calibration curve method is used to produce the printing plate compensation curve to achieve the neutral gray balance of the printed product.

[0016] As a preferred solution of the method for color matching between digital printing and flexographic printing described in the present invention, wherein: the S35 adjusts printing uniformity: adjusts the printing press button to reduce the deviation of the solid density on the printed sheet, the deviation of each ink on the printing surface does not exceed ±0.05, and the deviation of gray balance is as small as possible, not exceeding ±1.0a* or ±2.0b* in the printing area or on the roller.

[0017] As a preferred solution of the method for color matching between digital printing and flexographic printing described in the present invention, the S36 printing speed control: start the machine at a production speed of more than 1000 sheets / hour, and check the solid density, gray balance and uniformity again; if the change of the solid density, gray balance or uniformity of the ink exceeds the numerical value, adjust the printing press to ensure that the qualified printing requirements are obtained, and then speed up again as needed, print at a normal production speed, and ensure that the quality of the printed product is relatively uniform and stable; after completing the above steps, the printing equipment has reached a relatively good state, and at this time, start to make the equipment curve of traditional printing, print IT8.7 / 3 or ECI2002, to make the printing equipment output curve and compare it with the ISO standard sample.

[0018] As a preferred embodiment of the method for color matching between digital printing and flexographic printing of the present invention, the S41 printer linearization calibration is to evaluate the color value of the digital printing machine to produce a predictable color from a specific color input value;

[0019] The S42 records the characterization curve: establishes the color characteristics of each device, and these color characteristics are recorded by generating a "characteristic file" through the cooperation of third-party color management software and hardware; this step is used to produce the characteristic file of the digital printing device.

[0020] As a preferred solution of the method for color matching between digital printing and flexographic printing described in the present invention, wherein: the S43 color conversion: first convert the color mode from RGB to Lab mode, and then to CMYK mode; printing is the process of color copying and reproduction; each device has its own color gamut space, and color conversion of the color gamut space is performed during the copying process; the ICC output curve of the printing press produced during the previous printing is used as the target for simulation matching, and the obtained digital printing press curve is used as the final output curve; S44 color matching: color matching is completed with the help of third-party color management software, and the third-party color management software uses GMG or CGS.

[0021] As a preferred solution of the method for color matching between digital printing and flexographic printing described in the present invention, the S51 test evaluation sample: when all standardized printing processes are ready, print samples on traditional printing equipment and digital printing equipment respectively; the color control strips located at the bite and the tail on this sample can check whether the printed sheet is printed flat; the large color block in the middle is IT8.7 / 3, which can be used for data collection of device characteristics as ICC.

[0022] It also includes S53 color conversion: measure the color blocks from the output sample and compare them with the target value, and the result determines whether it passes; in the third-party color management software, select the data that matches the measured value for verification to obtain the △E color difference value; when all the data has been obtained, start the result comparison; judge the quality of the printed product through a combination of subjective and objective methods; if there is no problem with these two tests, it can be determined that the two printing methods have achieved color matching.

[0023] Compared with existing technologies:

[0024] 1. The color matching of digital printing and traditional printing combines the advantages of digital printing △E with traditional printing, making the printing quality better and the printing and process efficiency effectively improved; the printing and proofing colors can be quickly matched;

[0025] 2. Instead of relying solely on the personal experience of printing workers, the degree of automation has been significantly improved, printing efficiency has been improved, paper and ink losses have been greatly reduced, printing speed has been greatly increased, and product competitiveness has been improved;

[0026] 3. The color of the pattern printed for the first time by the pre-printing machine can be more than 97% close to the customer's standard sample; the control of hue, brightness and saturation is matched with flexographic printing, and the digital printing equipment and flexographic printing equipment are consistent in output quality and color. DETAILED DESCRIPTION

[0027] In order to make the objectives, technical solutions and advantages of the present invention more clear, the embodiments of the present invention will be described in further detail below.

[0028] The present invention provides a method for color matching between digital printing and flexographic printing, which specifically comprises the following steps:

[0029] S1. Carry out daily maintenance and upkeep of the machine, and clean and maintain the parts that have a great impact on printing quality;

[0030] S2, use the machine's built-in online densitometer to automatically calibrate the machine color;

[0031] S3, make preparations in advance; since there are many uncontrollable factors in printing equipment, such as the age of the rubber blanket roller, the control of the water-ink balance of the machine, the dot gain, and the performance of the substrate and ink, which will affect the printing quality, the printing equipment should be adjusted to the standard state; specifically, it includes S31 adjustment of traditional printing equipment and printing conditions, S32 printing solid density control, S33 dot gain curve ratio adjustment, S34 gray balance control, S35 adjustment of printing uniformity, and S36 printing speed control;

[0032] S4, preparation for digital printing; specifically including S41 printer linearization calibration, S42 recording characteristic curves, S43 color conversion, S44 color matching;

[0033] S5, printed product inspection; specifically includes S51 test evaluation sample and S52 data measurement and result comparison.

[0034] The S31 adjusts the traditional printing equipment and printing conditions: the traditional printing equipment and its common spare parts and consumables need to be maintained and properly cared for, such as replacing the rubber blanket, selecting the appropriate backing, adjusting the pressure between the printing plates and the pH value of the fountain solution, and controlling the ambient temperature and humidity; after preparation, printing begins, using the color sequence of black / cyan / magenta / yellow.

[0035] The S32 printing solid density control: during the entire printing process, printing is carried out in accordance with the printing standards and the printed sheets are printed flat (the color difference of the solid color blocks of each primary color on the layout is kept within △E<3), and the density value of each solid primary color when the color difference is minimum is recorded to facilitate color control in actual printing production: The S33 dot expansion curve ratio adjustment: in the pre-press workflow, by adjusting the dot expansion ratio, the corresponding anti-compensation curve of the printing plate is made to control the impact of dot expansion on printing; in the plate making process, the dot expansion curve provided in IS0 12647-2 is used to control traditional printing, and the mid-tone dot expansion ratio is about 16%.

[0036] The S34 gray balance control can control the neutral gray part of the printed product to obtain qualified printed products; in actual printing production, relevant color management software is used to create the equipment characteristic curve of the printing machine, which is placed in the CTP process to control the corresponding printing plate output, or the G7 calibration curve method is used to create a printing plate compensation curve to achieve neutral gray balance of the printed product.

[0037] The S35 adjusts printing uniformity: adjust the printing machine buttons to minimize the deviation of the solid density on the printed sheet. The deviation of each ink on the printed surface should not exceed ±0.05 to make the deviation of the gray balance as small as possible. It is best not to exceed ±1.0a* or ±2.0b* on the printing area or the roller.

[0038] The S36 printing speed control: start the machine at a production speed of more than 1000 sheets / hour (preheat the machine), and check the solid density, gray balance and uniformity again; if the change of the solid density, gray balance or uniformity of the ink exceeds the value, adjust the printing press to ensure that the qualified printing requirements are obtained, and then speed up again as needed, print at a normal production speed, and ensure that the quality of the printed product is relatively uniform and stable; after completing the above steps, the printing equipment has reached a relatively good state, and now start to make the equipment curve (ICC file) of traditional printing, print IT8.7 / 3 or ECI2002, to make the printing equipment output curve and compare it with the ISO standard sample.

[0039] The S41 printer linearization calibration: Calibration refers to a certain process under specified conditions, using a reference standard value to enable a digital printing machine to produce predictable colors from a specific color input value, and then evaluate its color value; usually in order to judge the printing conditions or uncertain factors of the device, regular calibration of the device is more helpful to improve the accuracy of the device's color output;

[0040] The S42 records the characterization curve: different input or output devices have different color expression capabilities; the same set of RGB or CMYK color values ​​will present different color effects when output on different devices; the purpose of characterization is to establish the color characteristics of each device, and these color characteristics are recorded by generating a "characteristic file" through the cooperation of third-party color management software and hardware; this step is used to create a characteristic file (ICC file) for digital printing equipment.

[0041] The S43 color conversion: first convert the color mode from RGB to Lab mode, and then to CMYK mode; printing is the process of color copying and reproduction; each device has its own color gamut space, and color conversion of the color gamut space is required during the copying process; of course, color conversion is by no means 100% "reproduction" but rather it brings out the best color of the device while allowing the operator to predict the result, i.e. "what you see is what you get"; this requires the use of the printing press ICC output curve produced during the previous printing as the target for simulation matching, and the resulting digital printing press curve is used as the final output curve; S44 color matching: color matching is completed with the help of third-party color management software, and the third-party color management software uses GMG or CGS.

[0042] The S51 test evaluation sample: After all standardized printing processes are ready, print samples on traditional printing equipment and digital printing equipment respectively; the color control strips located at the bite and the trail on this sample can check whether the print is printed flat; the large color block in the middle is IT8.7 / 3, which can be used for device characteristics when ICC data collection.

[0043] It also includes S53 color conversion: the process of color verification is usually very simple and can be fully automated in some cases; the color blocks are measured from the output sample and compared with the target value, and the result determines whether it passes; in the third-party color management software, the data that matches the measured value is selected for verification to obtain the △E color difference value; when all the data has been obtained, the result comparison is started; the quality of the printed product is judged by a combination of subjective and objective methods; subjective refers to visual inspection by the human eye to determine whether the color samples of traditional printed sheets and digital printed sheets are close; objective refers to whether the data collected by the two printing methods meet international standards (data collection △E<3); if there is no problem with these two tests, it can be determined that the two printing methods have achieved color matching.

[0044] Although the present invention has been described above with reference to the embodiments, various modifications may be made thereto and parts thereof may be replaced by equivalents without departing from the scope of the present invention. In particular, as long as there is no structural conflict, the various features in the embodiments disclosed in the present invention may be used in combination with each other in any manner, and the fact that these combinations are not exhaustively described in this specification is only for the sake of omitting space and saving resources. Therefore, the present invention is not limited to the specific embodiments disclosed herein, but includes all technical solutions falling within the scope of the claims.

Claims

1. A method for color matching between digital printing and flexographic printing, characterized in that: Specifically include the following steps: S1. Carry out daily maintenance and upkeep of the machine, and clean and maintain the parts that have a great impact on printing quality; S2, use the machine's built-in online densitometer to automatically calibrate the machine color; S3, make preparations in advance; due to the many uncontrollable factors of printing equipment, adjust the printing equipment to the standard state; specifically, S31 adjusts the traditional printing equipment and printing conditions, S32 controls the solid density of printing, S33 adjusts the proportion of the dot enlargement curve, S34 controls the gray balance, S35 adjusts the printing uniformity, and S36 controls the printing speed; S4, preparation for digital printing; specifically including S41 printer linearization calibration, S42 recording characteristic curves, S43 color conversion, S44 color matching; S5, printed product inspection; specifically including S51 test evaluation sample and S52 data measurement and result comparison; It also includes S53 color conversion: measure the color blocks from the output sample and compare them with the target value, and the result determines whether it passes; in the third-party color management software, select the data that matches the measured value for verification to obtain the △E color difference value; when all the data has been obtained, start the result comparison; judge the quality of the printed product through a combination of subjective and objective methods; if there is no problem with these two tests, it can be determined that the two printing methods have achieved color matching.

2. The method for color matching between digital printing and flexographic printing according to claim 1, characterized in that: The S31 adjusts the traditional printing equipment and printing conditions: replaces the rubber blanket, selects a suitable backing, adjusts the pressure between the printing plates and the pH value of the fountain solution, and controls the ambient temperature and humidity; after preparation, printing begins, using a color sequence of black / cyan / magenta / yellow.

3. The method for color matching between digital printing and flexographic printing according to claim 1, characterized in that: The S32 printing solid density control: during the entire printing process, printing is carried out in accordance with the printing standards and the printed sheets are printed flat, and the density values ​​of each solid primary color when the color difference is minimum are recorded to facilitate color control in actual printing production: The S33 dot enlargement curve ratio adjustment: in the pre-press workflow, the dot enlargement ratio is adjusted to make the corresponding anti-compensation curve of the printing plate to control the impact of dot enlargement on printing; in the plate making process, the dot enlargement curve provided in IS0 12647-2 is used to control traditional printing, and the mid-tone dot enlargement ratio is about 16%.

4. The method for color matching between digital printing and flexographic printing according to claim 1, characterized in that: The S34 gray balance control can control the neutral gray part of the printed product to obtain qualified printed products; in actual printing production, relevant color management software is used to create the equipment characteristic curve of the printing machine, which is placed in the CTP process to control the corresponding printing plate output, or the G7 calibration curve method is used to create a printing plate compensation curve to achieve neutral gray balance of the printed product.

5. The method for color matching between digital printing and flexographic printing according to claim 1, characterized in that: The S35 adjusts printing uniformity: adjusts the printing press buttons to reduce the deviation of the solid density on the printed sheet, the deviation of each ink on the printed surface does not exceed ±0.05, and the deviation of the gray balance is as small as possible, not exceeding ±1.0a* or ±2.0b* on the printing area or the roller.

6. The method for color matching between digital printing and flexographic printing according to claim 1, characterized in that: The S36 printing speed control: start the machine at a production speed of more than 1000 sheets / hour, and check the solid density, gray balance and uniformity again; if the change of the solid density, gray balance or uniformity of the ink exceeds the value, adjust the printing press to ensure that the qualified printing requirements are obtained, and then speed up again as needed, print at a normal production speed, and ensure that the quality of the printed product is relatively uniform and stable; after completing the above steps, the printing equipment has reached a relatively good state, and now start to make the equipment curve of traditional printing, print IT8.7 / 3 or ECI2002, to make the printing equipment output curve and compare it with the IS0 standard sample.

7. The method for color matching between digital printing and flexographic printing according to claim 1, characterized in that: The S41 printer linearization calibration: the digital printing press is able to produce predictable colors from a specific color input value, and then evaluates its color value; The S42 records the characterization curve: establishes the color characteristics of each device, and these color characteristics are recorded by generating a "characteristic file" through the cooperation of third-party color management software and hardware; This step is used to create a characteristic file for the digital printing device.

8. The method for color matching between digital printing and flexographic printing according to claim 1, characterized in that: The S43 color conversion: first convert the color mode from RGB to Lab mode, and then to CMYK mode; printing is the process of color copying and reproduction; each device has its own color gamut space, and color conversion of the color gamut space is performed during the copying process; the ICC output curve of the printing press produced during the previous printing is used as the target for simulation matching, and the obtained digital printing press curve is used as the final output curve; S44 color matching: color matching is completed with the help of third-party color management software, and the third-party color management software uses GMG or CGS.

9. The method for color matching between digital printing and flexographic printing according to claim 1, characterized in that: The S51 test evaluation sample: After all standardized printing processes are ready, print samples on traditional printing equipment and digital printing equipment respectively; the color control strips located at the bite and the trail on this sample can check whether the print is printed flat; the large color block in the middle is IT8.7 / 3, which can be used for device characteristics when ICC data collection.