JP5083486B2 - Printing control method and printing control apparatus - Google Patents

Description

  The present invention relates to a print control method and a print control apparatus that measure color management data for each printed matter printed by an offset printing press and enable appropriate ink key control based on the measured color management data.

  As a printing control method for improving the printing quality, color management data is measured for a plurality of printed matter printed by the printing press, and the printing press is included so that the plurality of color management data are included in an allowable range determined from a target value. There is a printing control method for controlling the printing. The print target value setting method for setting the target value includes a first method for setting a predetermined reference value, and color management data of an OK sheet obtained by color matching by an operator after starting printing. A second method for setting as a target value is used.

  The color management data is obtained by measuring a color bar including a color patch such as black (K), indigo (C), red (M), yellow (Y) or an actual pattern arranged in the margin of the printed material. Generally, it represents a density value or a colorimetric value.

  A target value necessary for managing print quality is set based on a density value or a colorimetric value. For example, in offset printing, when a predetermined reference value is set as in the first method, Generally, a standard value unique to a printing company is used, or a standard value of an industry standard that is generally well known. As domestic industry standards, ISO / Japan Color offset sheet-fed printing color standard, Japan Color Color Reproduction Printing 2001 (Japan Society for Printing Science), etc. are known.

  The first method for setting a predetermined reference value is widely used in Europe and the United States, and SWOP (Specifications for Web Offset Publications) is used as a reference value in the United States.

  In recent years, even in Japan, there is an advantage that anyone can stably obtain almost uniform print quality, so interest in print control based on reference values has rapidly increased, and color management data about printed matter has been set to a desired target value. A print control apparatus for controlling the printing machine to fit is commercially available. For sheet-fed offset printing presses, an offline printing control device that measures color management data of color bars laid out in the margin of printed matter offline and controls ink keys based on this color management data has been put to practical use. In an offset rotary printing press, in-line type print control devices that measure in-line color management data of color bars laid out in the margin of printed matter and control ink keys based on this color management data have been put into practical use. It is commercially available.

  These printing control devices control the ink key so that the color management data measured during printing is within the tolerance range determined based on the target value (to meet the target), and adjust to the appropriate ink amount. I do.

  By setting a predetermined reference value in such a print control apparatus and starting printing, it is possible to stably obtain a printed matter whose measured color management data is within an allowable range. .

  When using a print control method that uses reference values in printing, it is possible to quickly adjust to uniform print quality at all times, but in actual printing, color differences due to different ink lots, use of various papers, Due to subtle changes in the state of the daily printing press, the color tone and tone of the printed matter always changes slightly. For this reason, even if the print control is performed using the target value at the time of printing, the color tone and tone do not always match the color sample, so if the color sample does not match the color tone or tone, the delicate tone of the operator Matching is required.

  While checking the printed matter visually, the operator appropriately grasps the change in color tone and tone due to the above-mentioned various causes, appropriately adjusts the tone if necessary, and expressive printed matter that matches the color sample (OK sheet) It is possible to obtain Therefore, after starting printing with a predetermined reference value as a target, the color management data of an OK sheet obtained by tone matching by the operator or a printed material in the vicinity of this OK sheet is measured, and this color management data is the target value. Used as. This setting of the target value is the second method.

  Note that the second method includes a case where an operator performs tone adjustment from the time of printing and an OK sheet is created.

  When the print control is performed using the target value set based on the color management data corresponding to the OK sheet, control is performed to return the subsequent sheet to the OK sheet by the amount changed from the OK sheet. A printed matter similar to an OK sheet can be obtained, and a high-quality printed matter can be obtained until completion. (For example, refer to Patent Document 1.)

  In particular, when an off-line or in-line type print control device is used, a printed matter similar to the OK sheet can be obtained stably and skilllessly by controlling the ink amount based on the color management data corresponding to the OK sheet. It is possible and effective.

JP 2003-191443 A

  In the ink key opening adjustment method of the offset printing press using the color bar as described above, even if each CMYK single color is kept the same color while continuing printing for a long time, the secondary color or the tertiary color A phenomenon that the color changes may occur. This is because the ink viscosity and tack value (resistance when the ink is torn) changes while printing is continued for a long time, and the rate at which the post-printed ink is transferred onto the preprinted ink (ink trapping rate) changes. This is thought to be caused by

  Further, in Patent Document 1, in the ink key opening adjustment method of an offset printing machine using a color bar, as color management data, a flat mesh between 60% and 85% of each color of CMYK is used instead of the solid density of each color of CMYK. A method of measuring a density and calculating a deviation from a target density and adjusting the ink key opening based on the deviation is disclosed, and this method is described as being capable of producing a printed matter with a matching pattern tone.

  The feature of this method is that the size of the halftone dot to be printed changes as the viscosity of the ink changes while printing for a long time or dirt such as ink and paper dust accumulates on the blanket. By adjusting the film thickness of the film, it is offset and the same tone is maintained. That is, the greater the change in the size of the halftone dot, the greater the ink film thickness adjustment amount.

  On the other hand, the process ink used in general commercial offset printing has a tack value of each ink (resistance when the ink is torn) so that a certain color is reproduced when two or more colors of ink are overlaid. Designed). Since the tack value of ink changes depending on the ink film thickness and ink viscosity, if the ink film thickness changes greatly, the change of tack value also increases, and the rate at which the post-printed ink is transferred onto the preprinted ink (ink trapping rate) Therefore, the color expressed by overlapping two or more inks may change.

  In order to solve the above-described problem, the present invention can appropriately control a color expressed by overlapping two or more inks, and can perform appropriate ink key control even in long-time printing. And providing a printing control apparatus.

Specific means taken for realizing the present invention will be described below.
A printing control method according to an example of the present invention is a printing control method for adjusting an ink key opening of an offset printing machine based on color management data obtained by measuring a patch constituting a color bar.
The color management data has an initial target value set in advance,
When the amount representing ink trapping changes during printing of the offset printing machine, the target value of the color management data is reset based on the amount of change in the ink trapping ,
This is a printing control method that adjusts the ink key opening so that the color management data measured after that becomes an appropriate ink amount so as to approach the reset target value.

  In this way, by changing the target value of color management data flexibly according to changes in ink trapping, secondary and tertiary color changes due to fluctuations in ink trapping are reduced even during long-term printing control. An appropriate target value can be set.

More specifically, the amount of change in ink trapping is calculated in a uniform color space calculated from the results of measurement of a C and M multiply patch, a C and Y multiply patch, and an M and Y multiply patch. Control can be performed by expressing the change in the hue angle and the target hue angle.

More preferably, the amount of change in ink trapping is calculated from the result of measuring a patch of C100% and M100%, a patch of C100% and Y100%, and a patch of M100% and Y100%. Control can be performed by expressing the change in the hue angle in the uniform color space and the target hue angle. This is because the rate of transfer of the post-printing ink onto the pre-printed ink can be evaluated purely without being affected by the paper by using a patch of 100%. In that sense, it is desirable that at least the preprinted ink be 100%.

  In another specific method, a C100% and M100% multiplying patch, a C100% and Y100% multiplying patch, an M100% and Y100% multiplying patch, a C100% single color patch, It can be obtained by measuring an M100% single color patch and a Y100% single color patch and substituting each into the following equation to obtain an ink trapping rate.

  Ink trapping rate = {(Post-print ink density of patch with two colors superimposed)-(Post-print ink density of pre-print ink single color patch)} / (Post-print ink density of post-print ink single color patch)

  At this time, the patches measured to calculate the ink trapping rate are C100% and M100% monochromatic patches arranged at both ends of the multiplying patch of C100% and M100% in the color bar, and C100% and Y100. % 100% and Y100% single color patches are arranged at both ends of the patch, and M100% and Y100% single color patches are arranged at both ends of the patch. More effective.

A more accurate trapping rate can be calculated by arranging patches for calculating the trapping rate next to each other in the color bar.
Further , the target value of the present invention is controlled using data obtained by measuring a flat patch of each color of CMYK between 60% and 85% in which the change in tack value becomes larger as the color management data. Is more effective.

  In the present invention, the target value of the color management data can be flexibly raised and lowered according to the change of the ink trapping, and even in the long-time printing control, the color change of the secondary color and the tertiary color due to the change of the ink trapping. It is possible to set an appropriate target value for reducing.

  A slight change in the balance of ink (K), indigo (C), red (M), and yellow (Y) prevents the balance from being lost in a pattern that tends to appear as a change in color tone, and is similar to a color sample. Quality prints can be obtained.

  In the present embodiment, the color management data is mainly described as representing density values, but it may also represent colorimetric values.

  FIG. 1 is a block diagram illustrating an example of a print control apparatus that performs a print control method according to the present embodiment.

  FIG. 1 shows an example in which the printing control device 1 is applied to the ink key control device 2 and attached to a printing press (offset rotary press) 3.

  The print control apparatus 1 includes an acquisition unit 4, a designation reception unit 5, an extraction unit 6, a calculation unit 7, a setting unit 8, a control execution unit 9, and a display unit 10.

  The measuring heads 11a and 11b are the colors of the web 16 after passing through the printing units 12 to 15 of black (K), indigo (C), red (M), and yellow (Y) provided in the printing press 3. Measure management data. Each printing unit 12 to 15 is provided with a blanket cylinder 17, a plate cylinder 18, and an ink roller 19. In FIG. 1, the blanket cylinder 17, the plate cylinder 18, and the ink roller 19 are denoted only for the printing unit 12, and the numerals for the other printing units 13 to 15 are omitted.

  The acquisition unit 4 acquires each color management data measured by the measurement heads 11a and 11b. The acquired color management data history may be recorded in a recording unit (not shown).

  The designation receiving unit 5 receives an OK sheet designation from the operator. Alternatively, a target density value for each color is received.

  The extraction unit 6 selects the color management data corresponding to the OK sheet from the acquired color management data based on the specification of the OK sheet, and at least one other color determined based on the specification of the OK sheet. Extract management data.

  Other color management data is extracted according to a predetermined rule. For example, the color management data measured for several sheets before printing the OK sheet, several sheets after printing the OK sheet, and several sheets before and after printing the OK sheet are extracted. Further, for example, color management data measured at a time point before, a time point after, and a time point before and after a time when the OK sheet is printed may be extracted. Further, the color management data may be extracted with a predetermined interval.

  The calculation unit 7 calculates a target value for each color based on the plurality of extracted color management data or based on the target density value designated by the designation receiving unit 5. For example, the calculation unit 7 compares the plurality of extracted color management data, excludes data whose difference from other data is larger than a predetermined level, and obtains an average value of each color based on the remaining data. The target value. Also, the target value is controlled as needed based on the amount of change in ink trapping.

  The setting unit 8 obtains a control execution value such as an ink key operation amount so that the color management data measured and measured by the measurement heads 11a and 11b belongs to a predetermined allowable range determined by the target value. The execution value is output to the ink key control device 2 via the control execution unit 9.

  The display unit 10 graphically displays current and past color management data, a set target value, an OK sheet designation button for accepting designation of an OK sheet, and the like.

FIG. 2 is a diagram illustrating an example of a measurement target portion on a printed material (printed paper surface).
A color bar 21 including a single-color solid patch and a single-color flat mesh patch is arranged in a margin portion of the print layout 20 on the web 16.

  In the in-line type color management device 1, the color bar 21 printed on the web 16 is measured during printing.

  As a parameter to be measured, a density value or a CIELAB value may be used. Below, the case where the density value which has a high correlation with the ink amount and is generally used in the printing site is used will be described.

  The in-line type printing control apparatus 1 measures the entire color bar 21, compares the measured color management data with a target value, obtains the ink key opening so as to obtain an appropriate ink amount, and supplies the ink key control apparatus 2 with the ink key. Outputs the opening.

  In a general in-line type printing control apparatus, one measuring head is provided on each of the upper printing surface side and the lower printing surface side of the printing press. Measure the entire bar. In this case, the frequency of measuring individual patches of the color bar by each measuring head is once per scan. In a general inline type printing control apparatus, although it depends on the width of the web, it takes about 30 seconds for one scanning. For this reason, the individual patch measurement frequency of the color bar is once every 30 seconds. When the printing speed is 1000 RPM, the measurement frequency is once per 500 printed materials. In a general in-line type printing control apparatus, such a measurement frequency is sufficient to appropriately adjust the amount of ink on the paper surface during printing.

Next, a first embodiment will be described.
First, in commercial off-wheels, at least 60% to 85% of flat mesh patches of CMYK colors, C100% and M100% multiplying patches, and C100% and Y100% multiplying arranged perpendicular to the paper running direction. The color of each patch constituting the color bar including the patch and 7 patches of the patch of M100% and Y100% is measured by scanning the measurement head.

  At this time, the patch does not necessarily need to be a patch of 100%, and it is sufficient if the hue angle that is a reference of the patch is known. However, in order to suppress the influence of the paper, the patch of 100% is used. Is preferred.

  Next, the color measurement results of the C100% and M100% multiplied patch, the C100% and Y100% multiplied patch, and the M100% and Y100% multiplied patch are plotted in a uniform color space, for example, CIELAB space. The hue angle is calculated. At this time, the target hue angle may be calculated in advance by inputting a hue angle serving as a reference value in advance or by measuring a printed material as a sample.

  Here, with respect to Blue expressed by multiplying C100% and M100%, the hue angle measured and calculated during printing is compared with the target value, and when the deviation exceeds the threshold value, Adjust the target density of 60% to 85% flat patch. When the hue angle changes in the positive direction, the target density of C is increased or the target density of M is decreased. When the hue angle changes to minus, the target density of C is lowered or the target density of M is raised.

  Similarly, for Green expressed by multiplying C100% and Y100%, if the hue angle exceeds the allowable range and changes in the positive direction, the Y target density is increased or the C target density is decreased. When the hue angle changes to minus, the Y target density is lowered or the C target density is raised.

  Similarly, for Red expressed by multiplying M100% and Y100%, if the hue angle changes in the plus direction beyond the allowable range, the target density of M is increased or the target density of Y is decreased. When the hue angle changes to minus, the target density of M is lowered or the target density of Y is raised.

  When controlling the ink key by measuring the solid density of each color of CMYK, a 100% patch of each color of CMYK is used in place of the 65% to 85% flat mesh patch of each color of CMYK.

In the first embodiment, an example performed for CM multiplication blue will be described.
Printing was carried out by a method in which the density of the C single color was always adjusted to the reference density and the target density of M was adjusted. The threshold and the adjustment amount were as follows. In this embodiment, the solid density is used as color management data under ink key control.
Threshold value: CM multiplicative blue --- 0.07 rad
Adjustment amount: Solid density--0.04, 80% density --- 0.025

  The blue hue angle of the OK sheet on the CIELAB ab space was calculated to be -1.27 rad.

  Since the ink trapping rate of the M ink on the C ink during printing was changed, the hue angle of Blue that was continuously calculated was changed by +0.10 rad. Therefore, when the solid density target value of M was lowered by 0.04 of the adjustment amount, the hue angle of Blue became −1.25 rad, and the color returned to an OK sheet.

  Next, a second embodiment will be described. In this embodiment, flat mesh patches between 60% and 85% are used as color management data for ink key control.

  First, when designing the patches constituting the color bar, C100% and M100% monochromatic patches are applied to both ends of the C100% and M100% multiplying patches, and C100% and Y100 are applied to both ends of the C100% and Y100% multiplying patches. In the case where the M100% and Y100% monochromatic patches are arranged on both ends of the M100% and Y100% multiply patches, the ink trapping rate can be calculated by the following equation.

  Ink trapping rate = {(Post-print ink density of patch with two colors superimposed)-(Post-print ink density of pre-print ink single color patch)} / (Post-print ink density of post-print ink single color patch)

  For example, the ink trapping rate in the case of a cross patch of C100% and M100% is as follows.

  Ink trapping rate = {(M density of patch of C100% and M100% multiplied) − (M density of C100% monochrome patch)} / (M density of M100% monochrome patch)

  Here, for Blue expressed by multiplying C100% and M100%, the ink trapping rate measured and calculated during printing is compared with the target value, and if the deviation exceeds the threshold value, C or M Adjust the target density of the flat mesh patch between 60% and 85%. When the ink trapping rate increases, the target density of C is increased or the target density of M is decreased. When the ink trapping rate changes in a decreasing direction, the target density of C is lowered or the target density of M is raised.

  Similarly, for Green expressed by multiplying C100% and Y100%, if the ink trapping rate changes in a direction that decreases beyond the allowable range, the target density of Y is increased or the target density of C is decreased. . When the ink trapping rate changes in the increasing direction, the Y target density is lowered or the C target density is raised.

  Similarly, with respect to Red expressed by multiplying M100% and Y100%, if the ink trapping rate changes in a direction that increases beyond the allowable range, the target density of M is increased or the target density of Y is decreased. . When the ink trapping rate changes in a decreasing direction, the target density of M is decreased or the target density of Y is increased.

  When controlling the ink key by measuring the solid density of each color of CMYK, the target density of the 100% patch of each color of CMYK is adjusted instead of the flat mesh patch between 60% and 85% of each color of CMYK.

  The present invention can be used for ink key control of an offset printing press.

It is a block diagram which shows an example of the printing control apparatus which enforces the printing control method which concerns on embodiment of this invention. It is a figure which shows an example of the measurement object part in printed matter.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Print control apparatus, 2 ... Ink key control apparatus, 3 ... Printing machine, 4 ... Acquisition part, 5 ... Designation reception part, 6 ... Extraction part, 7 ... Calculation part, 8 ... Setting part, 9 ... Control execution part, 10 ... Display unit, 11a, 11b ... Measuring head, 12-15 ... Printing unit, 16 ... Web, 17 ... Blanket cylinder, 18 ... Plate cylinder, 19 ... Ink roller, 20 ... Printing layout, 21 ... Color bar

Claims (8)

In the printing control method for adjusting the ink key opening of the offset printing press based on the color management data obtained by measuring the patches constituting the color bar,
The color management data has an initial target value set in advance,
When the amount representing ink trapping changes during printing of the offset printing machine, the target value of the color management data is reset based on the amount of change in the ink trapping,
A print control method for adjusting the ink key opening so as to obtain an appropriate amount of ink to bring the color management data measured thereafter close to the reset target value,
The amount of change in the ink trapping is determined by calculating the hue angle in the uniform color space and the target calculated from the measurement results of the C and M multiplied patch, the C and Y multiplied patch, and the M and Y multiplied patch. The amount of change from the hue angle
The color management data is the density of each CMY color obtained by measuring a flat mesh patch between 60% and 85% of each CMY color,
When the hue angle calculated from the result of measuring the patch of C and M changes in the positive direction with respect to the target hue angle, the target value of C density is increased, or the M density If the target value is lowered or changes in the negative direction, the target value of the C density is lowered or the target value of the M density is raised and set again.
When the hue angle calculated from the result of measuring the patch of C and Y changes in the positive direction with respect to the target hue angle, the target value of Y density is increased, or the value of C density If the target value is lowered or changes in the negative direction, the target value of Y density is lowered or the target value of C density is raised and set again.
When the hue angle calculated from the result of measuring the M and Y multiplied patch changes in the positive direction with respect to the target hue angle, the target value of the M density is increased, or the Y density If the target value is lowered or changes in the negative direction, the target value of the M density is lowered or the target value of the Y density is raised and set again.
A printing control method for adjusting an ink key opening degree so that the density of each of the CMY colors measured thereafter becomes an appropriate amount of ink so as to approach the reset target value. In the printing control method for adjusting the ink key opening of the offset printing press based on the color management data obtained by measuring the patches constituting the color bar,
The color management data has an initial target value set in advance,
When the amount representing ink trapping changes during printing of the offset printing machine, the target value of the color management data is reset based on the amount of change in the ink trapping,
A print control method for adjusting the ink key opening so as to obtain an appropriate amount of ink to bring the color management data measured thereafter close to the reset target value,
The amount of change in the ink trapping is calculated from the result of measuring the C100% and M100% patch, the C100% and Y100% patch, and the M100% and Y100% patch. The amount of change between the hue angle and the target hue angle at
The color management data is the density of each CMY color obtained by measuring a flat mesh patch between 60% and 85% of each CMY color,
If the hue angle calculated from the result of measuring the patch of C100% and M100% changes in the positive direction with respect to the target hue angle, either increase the target value of C density, If the target value of density is lowered or changes in the minus direction, the target value of C density is lowered or the target value of M density is raised and set again.
If the hue angle calculated from the result of measuring the patch of C100% and Y100% changes in the positive direction with respect to the target hue angle, either increase the Y density target value or If the target value of density is lowered or changes in the negative direction, the target value of Y density is lowered or the target value of C density is raised and set again.
If the hue angle calculated from the result of measuring the M100% and Y100% patch has changed in the positive direction with respect to the target hue angle, either increase the target value of M density or If the target value of density is lowered or changes in the negative direction, the target value of M density is lowered or the target value of Y density is raised and set again.
A printing control method for adjusting an ink key opening degree so that the density of each of the CMY colors measured thereafter becomes an appropriate amount of ink so as to approach the reset target value. In the printing control method for adjusting the ink key opening of the offset printing press based on the color management data obtained by measuring the patches constituting the color bar,
The color management data has an initial target value set in advance,
When the amount representing ink trapping changes during printing of the offset printing machine, the target value of the color management data is reset based on the amount of change in the ink trapping,
A print control method for adjusting the ink key opening so as to obtain an appropriate amount of ink to bring the color management data measured thereafter close to the reset target value,
The amounts representing the ink trapping are C100% and M100% multiplying patches, C100% and Y100% multiplying patches, M100% and Y100% multiplying patches, C100% single color patches, and M100%. And the ink trapping ratio obtained by substituting each into the following equation:
Ink trapping rate = {(Post-print ink density of patch with two colors superimposed)-(Post-print ink density of pre-print ink single color patch)} / (Post-print ink density of post-print ink single color patch)
The color management data is the density of each CMY color obtained by measuring a flat mesh patch between 60% and 85% of each CMY color,
Ink trapping ratio in the patch of C100% and M100%
= {(M density of C100% multiplied by M100% patch)-(M density of C100% monochrome patch)} / (M density of M100% monochrome patch)
However, if it changes in a direction that is higher than the target ink trapping rate, the target value of C density is increased or the target value of M density is decreased, and if it changes in a decreasing direction, the density of C Lower the target value for M or increase the target value for the M density,
A printing control method for adjusting an ink key opening degree so that the density of each of the CMY colors measured thereafter becomes an appropriate amount of ink so as to approach the reset target value.   The patches measured to calculate the ink trapping ratio are C100% and M100% monochromatic patches arranged at both ends of a C100% and M100% multiply patch in the color bar, and C100% and Y100%. 4. The patch according to claim 3, wherein C100% and Y100% monochromatic patches are arranged at both ends of the multiplying patch, and M100% and Y100% monochromatic patches are arranged at both ends of the multiplying patch of M100% and Y100%. Print control method. In a print control device that adjusts the ink key opening of an offset printing machine based on color management data obtained by measuring patches constituting a color bar,
The color management data has an initial target value set in advance,
When the amount representing ink trapping changes during printing of the offset printing machine, the target value of the color management data is reset based on the amount of change in the ink trapping,
A print control device that adjusts the ink key opening so that the color management data measured after that becomes an appropriate ink amount so as to approach the re-set target value,
The amount of change in the ink trapping is determined by calculating the hue angle in the uniform color space and the target calculated from the measurement results of the C and M multiplied patch, the C and Y multiplied patch, and the M and Y multiplied patch. The amount of change from the hue angle
The color management data is the density of each CMY color obtained by measuring a flat mesh patch between 60% and 85% of each CMY color,
When the hue angle calculated from the result of measuring the patch of C and M changes in the positive direction with respect to the target hue angle, the target value of C density is increased, or the M density If the target value is lowered or changes in the negative direction, the target value of the C density is lowered or the target value of the M density is raised and set again.
When the hue angle calculated from the result of measuring the patch of C and Y changes in the positive direction with respect to the target hue angle, the target value of Y density is increased, or the value of C density If the target value is lowered or changes in the negative direction, the target value of Y density is lowered or the target value of C density is raised and set again.
When the hue angle calculated from the result of measuring the M and Y multiplied patch changes in the positive direction with respect to the target hue angle, the target value of the M density is increased, or the Y density If the target value is lowered or changes in the negative direction, the target value of the M density is lowered or the target value of the Y density is raised and set again.
A printing control apparatus that adjusts the ink key opening so that the density of each of the CMY colors measured thereafter becomes an appropriate ink amount so as to approach the reset target value. In a print control device that adjusts the ink key opening of an offset printing machine based on color management data obtained by measuring patches constituting a color bar,
The color management data has an initial target value set in advance,
When the amount representing ink trapping changes during printing of the offset printing machine, the target value of the color management data is reset based on the amount of change in the ink trapping,
A print control device that adjusts the ink key opening so that the color management data measured after that becomes an appropriate ink amount so as to approach the re-set target value,
The amount of change in the ink trapping is calculated from the result of measuring the C100% and M100% patch, the C100% and Y100% patch, and the M100% and Y100% patch. The amount of change between the hue angle and the target hue angle at
The color management data is the density of each CMY color obtained by measuring a flat mesh patch between 60% and 85% of each CMY color,
If the hue angle calculated from the result of measuring the patch of C100% and M100% changes in the positive direction with respect to the target hue angle, either increase the target value of C density, If the target value of density is lowered or changes in the minus direction, the target value of C density is lowered or the target value of M density is raised and set again.
If the hue angle calculated from the result of measuring the patch of C100% and Y100% changes in the positive direction with respect to the target hue angle, either increase the Y density target value or If the target value of density is lowered or changes in the negative direction, the target value of Y density is lowered or the target value of C density is raised and set again.
If the hue angle calculated from the result of measuring the M100% and Y100% patch has changed in the positive direction with respect to the target hue angle, either increase the target value of M density or If the target value of density is lowered or changes in the negative direction, the target value of M density is lowered or the target value of Y density is raised and set again.
A printing control apparatus that adjusts the ink key opening so that the density of each of the CMY colors measured thereafter becomes an appropriate ink amount so as to approach the reset target value. In a print control device that adjusts the ink key opening of an offset printing machine based on color management data obtained by measuring patches constituting a color bar,
The color management data has an initial target value set in advance,
When the amount representing ink trapping changes during printing of the offset printing machine, the target value of the color management data is reset based on the amount of change in the ink trapping,
A print control device that adjusts the ink key opening so that the color management data measured after that becomes an appropriate ink amount so as to approach the re-set target value,
The amounts representing the ink trapping are C100% and M100% multiplying patches, C100% and Y100% multiplying patches, M100% and Y100% multiplying patches, C100% single color patches, and M100%. And the ink trapping ratio obtained by substituting each into the following equation:
Ink trapping rate = {(Post-print ink density of patch with two colors superimposed)-(Post-print ink density of pre-print ink single color patch)} / (Post-print ink density of post-print ink single color patch)
The color management data is the density of each CMY color obtained by measuring a flat mesh patch between 60% and 85% of each CMY color,
Ink trapping ratio in the patch of C100% and M100%
= {(M density of C100% multiplied by M100% patch)-(M density of C100% monochrome patch)} / (M density of M100% monochrome patch)
However, if it changes in a direction that is higher than the target ink trapping rate, the target value of C density is increased or the target value of M density is decreased, and if it changes in a decreasing direction, the density of C Lower the target value for M or increase the target value for the M density,
A printing control apparatus that adjusts the ink key opening so that the density of each of the CMY colors measured thereafter becomes an appropriate ink amount so as to approach the reset target value.   The patches measured to calculate the ink trapping ratio are C100% and M100% monochromatic patches arranged at both ends of a C100% and M100% multiply patch in the color bar, and C100% and Y100%. 8. The patch according to claim 7, wherein C100% and Y100% monochromatic patches are arranged at both ends of the multiplying patch, and M100% and Y100% monochromatic patches are arranged at both ends of the multiplying patch of M100% and Y100%. Print control device.

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