Calibration Method for Electronically Engraved Gravure Plate Making

Abstract

The present invention discloses a calibration method for electronic engraving gravure plate making. By inputting different current values at set intervals without calibration, a printed four-color step wedge is obtained. Then, the density values and the solid density value on the four-color step wedge are measured to obtain the relationship between the density values of the four-color step wedge and the corresponding engraving current values. The density values are respectively converted into tone values a, and the relationship between the density value D<subgt;t< / subgt; and the current value is converted into the relationship between the tone value a and the engraving current value. A tone value increase curve is set, and the tone value increase curve is converted into a printing reproduction curve. According to the relationship between the tone value a and the engraving current value, the target tone value is obtained through the printing reproduction curve, so as to obtain the engraving current value A, and finally linearization calibration is carried out. The calibration method of the present invention solves the quality problems such as dot gain and low printing density in the existing electronic engraving plate making method.

Description

Technical Field

[0001] The present invention belongs to the technical field of intaglio printing and electronic engraving intaglio plate making, and relates to a correction method for electronic engraving intaglio plate making. Background Art

[0002] With the improvement of living standards, people have higher requirements for the quality of printed matter. High-quality printed matter can not only provide users with a good sense of use, but also accurately convey the information to be expressed. Intaglio printing can truly reproduce the effect of the original manuscript, with rich and clear levels, bright and vivid colors. In addition, it can use water-based ink and alcohol-soluble ink, meeting the requirements of green environmental protection printing. It can be widely applied to various media such as films, composite materials, and papers, and has become the second largest printing branch besides lithographic offset printing and is the main printing method for packaging printing.

[0003] In the intaglio printing industry, it is commonly said that "three points depend on printing, and seven points depend on plate making" to describe the importance of intaglio plate making. Due to different plate making processes, intaglio plate making methods are divided into two categories: etching plate making and engraving plate making. Etching plate making methods include Blum engraving and photogravure; engraving plate making methods include manual engraving plate making and electronic engraving plate making.

[0004] However, in the process of intaglio printing, problems such as dot gain and low printing density may occur due to changes in the properties of paper and ink, resulting in color deviation in printing and affecting the quality of printed matter. At present, most literatures only discuss and analyze the factors affecting intaglio printing and intaglio plate making. The literature "Research on the Quality Parameters of Electronic Engraving Intaglio Plate Making" (Chen Shurong, dissertation, Beijing Institute of Graphic Communication, 2013) analyzes the influence of quality parameters of electronic engraving intaglio plate making, such as engraving line number, screen angle, engraving needle angle, dot value, etc. on the quality of printed matter. The literature "Common Problems and Solutions in Plastic Intaglio Electro-engraving Plate Making" (Ma Lan, Printing Today, 2003 (01): 67-69) analyzes the common problems of printed matter caused by intaglio electro-engraving plate making and their solutions. However, there is no prior art research on the correction method for electronic engraving intaglio plate making.

[0005] Therefore, the present invention aims at electronic engraving intaglio plate making and corrects it during the intaglio printing process to ensure the quality of printed matter. Summary of the Invention

[0006] The purpose of the present invention is to provide a correction method for electronic engraving intaglio plate making, which solves the quality problems such as dot gain and low printing density in printed matter existing in the prior art of electronic engraving plate making method.

[0007] The technical solution adopted by the present invention is that the correction method for electronic engraving intaglio plate making is specifically implemented according to the following steps:

[0008] Step 1, during the process of making an intaglio plate by electronic engraving, input different current values at set intervals without correction to obtain the cyan (C), magenta (M), yellow (Y), and black (K) four-color step wedges for printing;

[0009] Step 2, measure the density value D of each color block on the cyan (C), magenta (M), yellow (Y), and black (K) four-color step wedges obtained in Step 1 t and the solid density value D of the cyan (C), magenta (M), yellow (Y), and black (K) four colors. s According to the engraving current value corresponding to each color block on the cyan (C), magenta (M), yellow (Y), and black (K) four-color step wedges in Step 1, the density value D of each color block on the cyan (C), magenta (M), yellow (Y), and black (K) four-color step wedges can be obtained t and the relationship with the engraving current value corresponding to each color block;

[0010] Step 3, use the Murray-Davies formula to convert the density value D of each color block on the cyan (C), magenta (M), yellow (Y), and black (K) four-color step wedges obtained in Step 2 t into the tone value a respectively, and then convert the relationship between the density value D and the current value in Step 2 t into the relationship between the tone value a and the engraving current value;

[0011] Step 4, set the tone value increase curve, and change the abscissa of the tone value increase curve to the tone value a, and use the sum of the ordinate value of the tone value increase curve and the tone value a as the printing reproduction curve for the ordinate;

[0012] Step 5, according to the relationship between the tone value a and the engraving current value obtained in Step 3, obtain the target tone value through the printing reproduction curve in Step 4, so as to obtain the engraving current value A;

[0013] Step 6, perform linearization correction.

[0014] The feature of the present invention also lies in that

[0015] in Step 1, the current value is a value after normalization, that is, 0 - 255.

[0016] In Step 3, the Murray-Davies formula is as follows:

[0017] (1)

[0018] In formula (1), a represents the tone value; D t represents the dot reflection density of each color block on the four-color step wedge or the relative density of each color block on the four-color step wedge. If it is the relative density, then D t represents the absolute density of each color block minus the density of the paper; D s represents the solid density of the cyan (C), magenta (M), yellow (Y), and black (K) four colors or the relative density of the cyan (C), magenta (M), yellow (Y), and black (K) four colors. If it is the relative density, then Ds It represents the absolute density of each color block minus the density of the paper.

[0019] The specific process of Step 5 is as follows:

[0020] Step 5.1: According to the printing reproduction curve obtained in Step 4, input the tone value a, and then obtain the target tone value.

[0021] Step 5.2: According to the relationship between the tone value a and the engraving current value obtained in Step 3, substitute the target tone value as the tone value a into the relationship between the tone value a and the engraving current value, so as to obtain the engraving current value A.

[0022] The specific process of Step 6 is as follows:

[0023] Step 6.1: Set up standard cyan C, magenta M, yellow Y, and black K four-color step wedges.

[0024] Step 6.2: For each color block of the standard cyan C, magenta M, yellow Y, and black K in Step 6.1, according to the printing reproduction curve in Step 4, obtain the corresponding target tone value A. Then, according to the relationship between the tone value a and the engraving current value obtained in Step 3, substitute the target tone value A as the tone value a into the relationship between the tone value a and the engraving current value, so as to obtain the engraving current value B.

[0025] Step 6.3: Use the engraving current value B obtained in Step 6.2 to repeat the process of Step 1 to re-engrave the four-color step wedge, proof it again, measure it according to Step 2, and convert it into the tone value b according to Step 3.

[0026] Step 6.4: For each color block of the standard cyan C, magenta M, yellow Y, and black K in Step 6.1, obtain the target tone value B of each color block according to the printing reproduction curve in Step 4.

[0027] Step 6.5: Compare the tone value b obtained in Step 6.3 and the target tone value B obtained in Step 6.4 for each color block.

[0028] Step 6.6: If the difference between the tone value b and the target tone value B in Step 6.5 is greater than 1%, repeat Steps 6.2 to 6.5 until the difference is less than 1%, then the calibration is completed.

[0029] In Step 6.1, the color blocks of the standard cyan C, magenta M, yellow Y, and black K four-color step wedges are arranged in ascending order of color depth. Each color block increases from the tone value of 0% to 100% at a set interval.

[0030] The beneficial effect of the present invention is that the calibration method for electronic engraved intaglio plate making of the present invention can ensure the quality of printed products through effective calibration during the printing process, and at the same time can reduce unnecessary waste and save time. Brief Description of the Drawings

[0031] Figure 1 is the tone value increase curve in the method of the present invention;

[0032] Figure 2 is the printing reproduction curve in the method of the present invention. Detailed Embodiment

[0033] The present invention will be described in detail below in conjunction with the drawings and the detailed embodiment.

[0034] The present invention provides a calibration method for gravure plate making by electronic engraving, which is specifically implemented according to the following steps:

[0035] Step 1, during the process of gravure plate making by electronic engraving, different current values are given to the engraving head, and different-sized cells will be engraved. Different amounts of ink will be transferred during printing, resulting in different tones. Without calibration, different normalized current values from 0 to 255 are input at set intervals, and a four-color step wedge plate of cyan C, magenta M, yellow Y, and black K with gradually changing but irregular colors will be engraved, and proofing will be carried out to obtain the printed four-color step wedges of cyan C, magenta M, yellow Y, and black K;

[0036] Step 2, use a spectrophotometer to measure the density value D of each color block on the four-color step wedges of cyan C, magenta M, yellow Y, and black K obtained in Step 1 t and the solid density values D of cyan C, magenta M, yellow Y, and black K; s According to the engraving current value corresponding to each color block on the four-color step wedges of cyan C, magenta M, yellow Y, and black K in Step 1, the relationship between the density value D of each color block on the four-color step wedges of cyan C, magenta M, yellow Y, and black K t and the engraving current value corresponding to each color block can be obtained;

[0037] Step 3, use the Murray-Davis formula to convert the density value D of each color block on the four-color step wedges of cyan C, magenta M, yellow Y, and black K obtained in Step 2 t into the tone value a respectively, so as to convert the relationship between the density value D and the current value in Step 2 t into the relationship between the tone value a and the engraving current value;

[0038] The Murray-Davis formula is as follows:

[0039] (1)

[0040] In formula (1), a represents the tone value; D tRepresents the dot reflection density of each color patch on the four-color step wedge or the relative density of each color patch on the four-color step wedge. If it is the relative density, then D t Represents the absolute density of each color patch minus the density of the paper; D s Represents the solid density of cyan C, magenta M, yellow Y, and black K or the relative density of cyan C, magenta M, yellow Y, and black K. If it is the relative density, then D s Represents the absolute density of each color patch minus the density of the paper;

[0041] Step 4: Set the tone value increase curve, and change the abscissa of the tone value increase curve to the tone value a, and change the ordinate to the sum of the ordinate value of the tone value increase curve and the tone value a as the printing reproduction curve. The ordinate of the printing reproduction curve represents the target tone value;

[0042] Among them, as Figure 1 shown, the tone value increase curve adopts one of the relevant curves in the ISO 12647 standard or a custom curve;

[0043] Step 5: According to the relationship between the tone value a and the engraving current value obtained in Step 3, obtain the target tone value through the printing reproduction curve in Step 4, so as to obtain the engraving current value A;

[0044] Step 5.1: According to the printing reproduction curve obtained in Step 4, input the tone value a, then the target tone value is obtained;

[0045] Step 5.2: According to the relationship between the tone value a and the engraving current value obtained in Step 3, substitute the target tone value as the tone value a into the relationship between the tone value a and the engraving current value, so as to obtain the engraving current value A;

[0046] Step 6: Linearization correction;

[0047] Step 6.1: Set the standard cyan C, magenta M, yellow Y, and black K four-color step wedges;

[0048] The color patches of the standard cyan C, magenta M, yellow Y, and black K four-color step wedges are arranged in ascending order of color depth. The tone value of each color patch increases from 0% to 100% at a certain interval (usually 10%, and the interval can be reduced in the highlight and shadow parts). For example, the tone value of each color patch is 0%, 2%, 3%, 5%, 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, 95%, 97%, 98%, 100%;

[0049] Step 6.2: For each color patch of standard cyan C, magenta M, yellow Y, and black K in Step 6.1, obtain the corresponding target tone value A according to the printing reproduction curve in Step 4. Then, based on the relationship between the tone value a and the engraving current value obtained in Step 3, substitute the target tone value A as the tone value a into the relationship between the tone value a and the engraving current value, thereby obtaining the engraving current value B.

[0050] Step 6.3: Use the engraving current value B obtained in Step 6.2 to repeat the process of Step 1 to re-engrave the four-color step wedge, proof again, measure according to Step 2, and convert to the tone value b according to Step 3.

[0051] Step 6.4: For each color patch of standard cyan C, magenta M, yellow Y, and black K in Step 6.1, obtain the target tone value B for each color patch according to the printing reproduction curve in Step 4.

[0052] Step 6.5: Compare the tone value b obtained in Step 6.3 and the target tone value B obtained in Step 6.4 for each color patch.

[0053] Step 6.6: If the difference between the tone value b and the target tone value B in Step 6.5 is greater than 1%, repeat Steps 6.2 to 6.5 until the difference is less than 1%, then the calibration is completed.

[0054] Embodiment

[0055] Step 1: During the process of electronic engraving intaglio plate making, applying different current values to the engraving head will engrave different-sized cells, and different amounts of ink will be transferred during printing, thereby producing different tones. Without calibration, input different normalized current values from 0 to 255 at set intervals, then an intaglio plate of cyan C, magenta M, yellow Y, and black K four-color step wedges with gradually changing but irregular colors will be engraved and proofed to obtain the printed four-color step wedges.

[0056] Step 2: Use a spectrophotometer to measure the density value D of each color patch on the cyan C, magenta M, yellow Y, and black K four-color step wedges obtained in Step 1 t and the solid density values D of cyan C, magenta M, yellow Y, and black K; according to the engraving current value corresponding to each color patch on the cyan C, magenta M, yellow Y, and black K four-color step wedges in Step 1, the density value D of each color patch on the cyan C, magenta M, yellow Y, and black K four-color step wedges can be obtained s and the relationship between the density value D of each color patch and the corresponding engraving current value, as shown in Table 1. t Table 1 Relationship between the density value of each color patch on the four-color step wedge and the corresponding engraving current value of each color patch

[0057]

[0058] ​

[0059] Step 3: Use the Murry-Davis formula to convert the density value D of each color block of the cyan C, magenta M, yellow Y, and black K four-color step wedges obtained in Step 2 t into the tone value a respectively, so as to convert the relationship between the density value D in Step 2 t and the current value into the relationship between the tone value a and the engraving current value, as shown in Table 2;

[0060] Table 2 Relationship between tone value a and engraving current value

[0061]

[0062] Step 4: Set the tone value increase curve (as Figure 2 shown, select Curve A in the tone scale expansion curve of ISO 12647-2), and change the abscissa of the tone value increase curve to the tone value a, and change the ordinate to the sum of the ordinate value of the tone value increase curve and the tone value a as the printing reproduction curve. The ordinate of the printing reproduction curve represents the target tone value;

[0063] Step 5.1: According to the printing reproduction curve obtained in Step 4, input the tone value a, and then the target tone value can be obtained, as shown in Table 3;

[0064] Step 5.2: According to the relationship between the tone value a and the engraving current value obtained in Step 3, substitute the target tone value as the tone value a into the relationship between the tone value a and the engraving current value, so as to obtain the engraving current value A;

[0065] Table 3 Tone value a and target tone value

[0066]

[0067] Step 6.1: Set the standard cyan C, magenta M, yellow Y, and black K four-color step wedges;

[0068] The color blocks of the standard cyan C, magenta M, yellow Y, and black K four-color step wedges are arranged in ascending order of color depth. Each color block increases from the tone value of 0% at a certain interval (usually 10%, and the interval can be reduced in the highlight and shadow parts) to 100%. Set the tone value of each color block to 0%, 2%, 3%, 5%, 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, 95%, 97%, 98%, 100%;

[0069] Step 6.2: For each color patch of standard cyan C, magenta M, yellow Y, and black K in Step 6.1, obtain the corresponding target tone value A according to the printing reproduction curve in Step 4. Then, based on the relationship between the tone value a and the engraving current value obtained in Step 3, substitute the target tone value A as the tone value a into the relationship between the tone value a and the engraving current value, so as to obtain the engraving current value B, as shown in Table 4;

[0070] Table 4 Engraving Current Value B

[0071]

[0072] Step 6.3: Use the engraving current value B obtained in Step 6.2 to repeat the process of Step 1 to re-engrave the four-color step wedge, proof again, measure according to Step 2, and convert to the tone value b according to Step 3;

[0073] Step 6.4: For each color patch of standard cyan C, magenta M, yellow Y, and black K in Step 6.1, obtain the target tone value B for each color patch according to the printing reproduction curve in Step 4, as shown in Table 5;

[0074] Table 5 Tone Value b and Target Tone Value B

[0075]

[0076] Step 6.5: Compare the tone value b obtained in Step 6.3 and the target tone value B obtained in Step 6.4 for each color patch;

[0077] Step 6.6: If the difference between the tone value b and the target tone value B in Step 6.5 is greater than 1%, repeat Steps 6.2 to 6.5 until the difference is less than 1%, then the calibration is completed.

Claims

1. A correction method for gravure plate making by electronic engraving, characterized in that The implementation is specifically carried out according to the following steps: Step 1, during the process of gravure plate making by electronic engraving, without correction, different current values are input at set intervals to obtain the four-color step wedges of cyan (C), magenta (M), yellow (Y), and black (K) for printing; Step 2: Measure the density value D of each color block on the cyan C, magenta M, yellow Y, and black K four-color step wedges obtained in Step 1 t and the solid density values D of cyan C, magenta M, yellow Y, and black K s , based on the engraving current value corresponding to each color block on the cyan C, magenta M, yellow Y, and black K four-color step wedges in Step 1, the density value D of each color block on the cyan C, magenta M, yellow Y, and black K four-color step wedges can be obtained t the relationship between the density value D and the engraving current value corresponding to each color block; Step 3: Use the Murray-Davies formula to convert the density value D of each color block of the cyan C, magenta M, yellow Y, and black K four-color step wedges obtained in Step 2 t into the tone value a respectively, and then convert the relationship between the density value D in Step 2 t and the current value into the relationship between the tone value a and the engraving current value; Step 4, set the tone value increase curve, and change the abscissa of the tone value increase curve to tone value a, and change the ordinate to the sum of the ordinate value of the tone value increase curve and tone value a as the printing reproduction curve; Step 3, according to the relationship between the tone value a and the engraving current value obtained in Step 3, obtain the target tone value through the printing reproduction curve in Step 4, so as to obtain the engraving current value A; Step 6, linearization correction; The specific process of Step 6 is as follows: Step 6.1, set the standard four-color step wedges of cyan (C), magenta (M), yellow (Y), and black (K); Step 6.2, for each color block of the standard cyan (C), magenta (M), yellow (Y), and black (K) in Step 6.1, according to the printing reproduction curve in Step 4, obtain the corresponding target tone value A, and then according to the relationship between the tone value a and the engraving current value obtained in Step 3, substitute the target tone value A as the tone value a into the relationship between the tone value a and the engraving current value, so as to obtain the engraving current value B; Step 6.3, use the engraving current value B obtained in Step 6.2 to repeat the process of Step 1 to re-engrave the four-color step wedges, proof again, measure according to Step 2, and convert to tone value b according to Step 3; Step 6.4, for each color block of the standard cyan (C), magenta (M), yellow (Y), and black (K) in Step 6.1, obtain the target tone value B of each color block according to the printing reproduction curve in Step 4; Step 6.5, compare the tone value b obtained in Step 6.3 and the target tone value B obtained in Step 6.4 for each color block; Step 6.6, if the difference between the tone value b and the target tone value B in Step 6.5 is greater than 1%, repeat Steps 6.2 to 6.5 until the difference is less than 1%, then the correction is completed.

2. The calibration method for gravure plate making by electronic engraving according to claim 1, wherein In Step 1, the current value is the value after normalization, that is, 0 to 255.

3. The calibration method for electronic engraving gravure plate making according to claim 1, characterized in that, In Step 3, the Murray-Davies formula is as follows: （1） In formula (1), a represents the tone value; D t represents the dot reflection density of each color patch on the four-color step wedge or the relative density of each color patch on the four-color step wedge. If it is the relative density, D t represents the absolute density of each color patch minus the density of the paper; D s represents the solid density of the four colors C, M, Y, K or the relative density of the four colors C, M, Y, K. If it is the relative density, D s represents the absolute density of each color patch minus the density of the paper.

4. The calibration method for electronic engraving gravure plate making according to claim 1, characterized in that, The specific process of Step 5 is as follows: Step 5.1, according to the printing reproduction curve obtained in Step 4, input the tone value a, then the target tone value is obtained; Step 5.2, according to the relationship between the tone value a and the engraving current value obtained in Step 3, substitute the target tone value as the tone value a into the relationship between the tone value a and the engraving current value, so as to obtain the engraving current value A.

5. The calibration method for gravure plate making by electronic engraving according to claim 1, wherein, In Step 6.1, the color blocks of the standard four-color step wedges of cyan (C), magenta (M), yellow (Y), and black (K) are arranged in ascending order of color depth, and each color block increases from 0% of the tone value to 100% at a set interval.

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