JP2003169223A - Color tone control method for printer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for easily calculating an ink concentration difference to make a color tone of a commercial printed matter equal to that obtained when generating a printer profile thereby simplifying color tone control without the need for receiving a target spectral reflectance and measurement of an OK sheet. <P>SOLUTION: The color tone control method comprises inputting a color coordinate difference of a control object color between a profile generation pattern printed matter and the commercial printed matter and ink concentration of the commercial printed matter, defining a function (f) to calculate an ink concentration difference by which the color coordinates of the control object color of the profile generation pattern printed matter are made nearly matched with those of the commercial printed matter, and controlling an ink key of the printer on the basis of the ink concentration difference calculated by the function (f) to control the color tone. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a color tone control method in a printing machine, and more particularly, to a printing plate prepared by using color development characteristic data (hereinafter abbreviated as a profile) in the printing machine, and the same conditions as those used when creating the profile. The present invention relates to a color tone control method for a printing machine, which enables quick, easy, and automatic color tone adjustment when the color tone changes due to a change in the color reproduction state of the printing machine even though the printing has been performed by.

[0002]

2. Description of the Related Art In the printing world, in order to match the color reproduction characteristics of individual devices such as a printing press and a plate making system, the halftone dot area ratio and the color of the printing press (for example, the color coordinates defined by the International Lighting Commission) are used. Value, CIE-L *, a *, b
For example, ICC (Internet) that describes the correspondence with *)
different color devices, by creating color development characteristic data such as a profile of a regional color consortium) and converting digital data so that the colorimetric value of the printed matter approximates the desired color on the upstream side based on the data. A color management system is used in which the color reproducibility is matched.

However, even if the digital data is converted by using such a profile on the upstream side and a printing plate is created, in order to obtain a desired color on the printed matter, the printing machine at the time of creating the profile is required. It is necessary to keep various conditions in the actual printing until the actual printing.However, the conditions for creating the profile and the conditions for actually printing may be different, and the color reproduction state on the printing machine depends on various causes. It could change.

That is, even if the material conditions such as ink and printing paper and the ink density are the same as when the profile was created, a rocking roller, a watering roller, etc. for evenly distributing the ink to the ink roller in the printing machine. Movement,
A slight variation such as the printing pressure of the blanket cylinder may affect the color reproduction state subtly, and the color reproduction state may differ due to machine-to-machine error, humidity, temperature, time from the start of printing, etc. The phenomenon that the color of the tone part does not match occurs.

Therefore, a phenomenon occurs in which the color reproduction state at the time of profile creation differs from the color reproduction state at the time of actual printing. In such a case, it is necessary to manually control by looking at the print result of the commercial print. In some cases, it is necessary to recreate the profile of the current printing press, feed it back to the upstream side, and remake the printing plate. Moreover, in this way, controlling the color tone by manual control requires skill of the operator,
It takes time to reach the desired color, and a large amount of waste paper is produced, and the method of recreating the profile to make the printing plate naturally requires a great deal of time and money,
Not cost effective.

In order to deal with such a problem, for example, JP-A-7-205412, JP-A-11-99629, JP-A-11-216847, and JP-A-2001.
No. 277473 discloses that the input target spectral reflectance and the measurement results such as a color chart on an OK sheet (a reference printed matter such as a proof or a temporary proof) and a commercial printed matter (customer's printed matter). There is disclosed a method and an apparatus which calculate a difference from a measurement result such as a color chart and control the ink key by using the difference so that such color tone control can be automated to some extent.

That is, first, in Japanese Unexamined Patent Publication No. 7-205412, a difference-ink density spectrum is detected from an ink density spectrum of an image portion of an OK sheet and an image portion of a printed matter, and the difference-ink density spectrum is overprinted. Representing a linear combination function of the ink density spectrum in each printing ink used in the above, a method for detecting the adjustment command for the ink supply mechanism from the proportional coefficient of the linear combination function to control the color tone is shown.

Next, in Japanese Patent Laid-Open No. 11-99629, the spectral reflectance of a color scale printed on a printed matter is measured, and a deviation from a target spectral reflectance which is input in advance is obtained, and the deviation is calculated. An example is shown in which the ink amount is controlled by filtering and integrating the color matching function and the spectral distribution of the observation light source, and calculating the ink solid density deviation that minimizes the deviation from the target spectral reflectance from this integrated value. Has been done.

Further, in Japanese Unexamined Patent Publication No. 11-216847, an image portion of a printed matter is scanned with light from a visible light region to a near infrared region in which black ink has a rated value of absorption, and this value and a target color value. And the color space coordinate value L defined by CIE
A device is shown which calculates *, a *, b * and controls the ink amount so as to reduce the difference.

Further, in Japanese Unexamined Patent Publication No. 2001-277473, from the measurement results of an OK sheet and a commercial printed matter, a coefficient for correcting the amount of dot weight in the Neugebauer equation and the amount of density reduction in the overprinted portion are calculated, and Method to calculate the ink density deviation from Neugebauer's formula by calculating the spectral density and solid density and calculating the proportional constant for calculating the minute change in spectral reflectance from these values, and controlling the ink supply amount It is shown.

[0011]

However, in all of these conventional techniques, the input target spectral reflectance or OK is input.
It tries to control the ink supply amount by comparing the measurement result of the sheet and the measurement result of the commercial printed matter and based on the deviation, even if the printing machine profile is fed back to the upstream side and the printing plate is created based on it. , It is necessary to measure the OK sheet and input the target spectral reflectance, and it is difficult to say that the created printing machine profile is effectively used.

Therefore, in the present invention, the ink density difference that makes the color tone of a commercial print equivalent to that at the time of creating a printing press profile can be easily and easily calculated without inputting a target spectral reflectance and measuring an OK sheet. Therefore, it is an object to provide a method for facilitating color tone control.

[0013]

In order to solve the above problems, according to the present invention, as described in claim 1, a profile (coloring characteristic data) describing a correspondence relationship between a halftone dot area ratio of a printing machine and coloration is described. In the color tone control method for a printing press, a plate is created based on the above, and the color to be controlled is measured by measuring the control target color of the commercial print by the plate. From the color difference between the target colors and the ink density of the commercial print, an ink density difference that substantially matches the color tones of the control target colors in the commercial print and the picture print for profile creation is calculated, and printing is performed with the ink density difference. It is characterized by controlling the ink key of the machine to control the color tone.

As described above, the color tone of the control target color in the commercial print and the profile creation pattern print is determined from the color difference between the control target colors in the profile print design print and the commercial print and the ink density of the commercial print. By making it possible to calculate the ink density difference that substantially matches, it is possible to easily reproduce a color reproduction state similar to the color reproduction state at the time of profile creation, and input the target spectral reflectance and measure the OK sheet. Without this, color tone control can be performed easily and easily.

The calculation of the ink density difference which makes the color tone equal to that at the time of profile creation is performed by, as described in claim 2, the color tone of the control target color in the profile printed picture printed material and the commercial printed material substantially match. The ink density difference to be caused is a color difference in control target colors between a plurality of comparative prints printed in a plurality of color reproduction states different from that at the time of profile creation and the profile creation picture print, and each of the comparative prints. Ink density at
The ink density difference that substantially matches the color tones of the control target colors in each of the comparison prints and the profile creation pattern print is accumulated as data, and based on the accumulated data, the profile creation pattern print and the commercial print And the ink density of the commercial printed matter are input, and an ink density difference that substantially matches the color tone of the controlled color in the commercial printed matter and the profile creation picture printed matter is output. It is characterized in that it is calculated by a function defined as follows.

If the function is defined in advance in this way, the color difference between the control target colors of the commercial printed material and the profile design picture printed material and the ink density of the commercial printed material are input to this function. , It is possible to obtain an ink density difference that substantially matches the color tones of a commercial printed matter and a profile printed picture printed matter, without inputting a target spectral reflectance or measuring an OK sheet, and easily,
The color difference can be easily controlled by calculating the density difference.

When calculating the ink density difference for the definition of the function and the color tone control in the commercial printed matter, not only the ink density of the commercial printed matter but also the definition of the function and the commercial quantity are used as described in claims 3 and 4. In calculating the ink density difference for color tone control in the printed matter, the dot gain and the trapping amount, or the ink density-dot gain characteristic and the ink density-trapping characteristic in each of the profile creation picture printed matter, the comparative printed matter, and the commercial printed matter. Is added. When calculating the ink density difference for color tone control in the definition of the function and commercial printed matter, instead of the ink density in each of the profile creation picture printed matter, the comparative printed matter, and the commercial printed matter, ink density-dot gain characteristics and Ink density-trapping characteristics are used.

Since the ink density, the dot gain, and the trapping amount are originally correlated with each other, if the ink density is known, the ink density difference that substantially matches the color tones of the control target color in the commercial print and the profile creation picture print is output. Although the function to be defined can be defined, by adding or using the dot gain and the trapping amount, or the ink density-dot gain characteristic and the ink density-trapping characteristic in this way, the definition of the function and the ink for color tone control in commercial printed matter can be performed. The density difference can be calculated more accurately and easily.

As for the control object color, as described in claim 5, the control object color is gray.

By defining the control object color as gray and defining the function with respect to gray in this way, since gray is located in the center of the color space and three colors of yellow, magenta and cyan are used, Color matching of colors other than gray can be performed together, and color matching can be performed easily and efficiently.

Further, the control target color is, as described in claim 6, characterized in that the control target color is a specific color such as a flesh color, sky blue, or green of trees.

That is, in commercial printing, it is necessary to finely adjust the color tone. For example, by defining a function for a specific color such as flesh color, sky blue, and green of trees, the color tone of these specific colors changes. Even in such a case, the color tone at the time of profile creation can be easily obtained, and efficient pre-print preparation can be performed.

[0023]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be exemplarily described in detail below with reference to the drawings. However, the dimensions, materials, shapes, relative positions, and the like of the constituent parts described in this embodiment are not intended to limit the scope of the present invention thereto, unless otherwise specified, and are merely It is only an example.

FIG. 1 is a diagram for explaining the principle of a color tone control method in a printing machine according to the present invention, and FIG. 2 is a table for creating data for defining a function used in the color tone control method in a printing machine according to the present invention. FIG. 3 for explaining the method of
Is a diagram for explaining a function used in a color tone control method in a printing machine according to the present invention, FIG. 4 is a diagram for explaining a color tone control method in a printing machine according to the present invention, and FIG. 5 is an ink density and a dot gain. 6 is a graph showing the correlation between the ink density and the trapping, and FIG.
7 and 8 are diagrams for explaining another embodiment of the function used in the color tone control method in the printing machine according to the present invention.

In the figure, reference numeral 1 denotes a printed matter of a profile creating picture. In the present invention, the profile creating picture printed matter 1 is, for example, as shown in FIG. 2, a profile creating color chart 2 having a 420 color picture. The color bar 3 is printed on the margin. 4 in FIG.
Is a reference color coordinate value G _T (L _T *, which is obtained by measuring the spectral reflectance of the color bar in the profile-designed printed matter 1 with a color tone measuring device (not shown)
a _T *, b _T *) to represent a normal color, the L * a * b * color system (C) defined by the International Commission on Illumination as described above is used.
IELAB), also the color coordinates of the XYZ color system of the International Commission on Illumination CIE, the L * u * v * color system (CIEUV), the spectral reflectance, and the wavelength bands of cyan, magenta, and yellow. A value obtained by dividing the absorption wavelength band into three and calculating the integral value of the spectral reflectance for each wavelength band is used. In the following description, the color coordinate values of the L * a * b * color system are used as an example. I will explain. However, this is an example, and it is obvious that any color system or measurement value may be used.

Reference numeral 5 is a comparative printed matter before color matching, in which the ink film thickness of the printing machine is printed with the same standard film thickness as when the profile was created, when the color reproduction condition was different from that when the profile was created. As shown in FIG. 2, the comparative printed matter 5 before the alignment has a color bar 6 similar to the color bar 3 in the profile printed picture printed matter 1 in the margin as shown in FIG.
To print. Although the comparative printed matter 5 is referred to as a comparative printed matter for convenience of description, it may be an ordinary commercial printed matter (customer's printed matter). 7 is a comparative color coordinate value G (L *, a *, b *), which is calculated from the measured spectral reflectance of the color bar 6 in the comparative printed matter 5 before color matching, 8
This comparative color coordinate value G (L *, a *, b *) as a reference color coordinate value _{G T (* L T, a} T *, b T *) be the color difference calculated by the difference processing , Here L * a * b * as described above
The color coordinate value difference (ΔL *, Δa *, Δb *) is obtained because the description is made using the color system (CIELAB). Reference numeral 9 is a comparative printed matter after the color tones of the control target colors in the color bar 6 of the comparative printed matter 5 before color matching and the color bar 3 of the profile printed picture printed matter 1 are matched, and 10 is the color bar, 11 Is the color coordinate value after color matching G ′ (L *, a *, b, which is calculated from the measured spectral reflectance of the color bar 10 in the comparative printed matter 9 after the color matching.
*), 12 are color coordinate values G '(L *, a
*, B *) as a reference color coordinate value _{G T (L T *, a} T *, b T *)
It means that and are almost the same.

Reference numeral 31 in FIG. 3 is for comparison before color matching.
Cyan of color bar 6 in printed matter 5 (D_C), Maze
Input (D_M), Yellow (D_Y), Black (D_K)of
Ink density. This ink density is for comparison before color matching.
The printed matter 5 is printed with the ink film thickness of the printing machine as the standard film thickness.
It is basically a standard concentration because it is the 32 is the same
Ann (DG_C), Magenta (DG_M), Yellow (DG
_Y), Black (DG _K) Dot gain, 33 is the same
Between cyan and magenta (TR_B), Between cyan and yellow
(TR_G), Between magenta and yellow (TR_R) Track
Ping, 34, 35, 36, 37 are comparisons before color matching
Profile of color bar 6 in printed matter 5
The color tone of the color bar 3 in the picture print for creation 1
Cyan (ΔD_C), Magenta (Δ
D_M), Yellow (ΔD_Y), Black (ΔD_K)
Ink density change (ink density difference), 38
Color difference (color coordinate value difference ΔL *, Δa *, Δb *) 8, in
Concentration (D_C, D_M, D_Y, D_K) 31, dot gain
(DG_C, DG_M, DG_Y, DG_K) 32, trappin
Gu (TR_B, TR_G, TR_R) 33 as input
Concentration change (ΔD_C, ΔD_M, ΔD_Y, ΔD_K) 3
The function f outputs 4, 35, 36, and 37.

In FIG. 4, 40 is the color coordinate value of the control target color in the comparison printed matter 5 before color matching, 41 is the color coordinate value of the control target color in the profile creation pattern printed matter 1, which is the comparison printed matter before color matching. The color to be controlled in No. 5 is color-matched with the color coordinate value 41 of the color to be controlled in the profile printed picture printed matter 1 as a target. Four
2, 44 and 46 are color coordinate values of the evaluation color in the comparison printed matter 5 before color matching, 43, 45 and 47 are color coordinate values of the evaluation color in the profile creation pattern printed matter 1, 50 in FIGS. 7 and 8. 53 is another embodiment of the function used in the color tone control method in the printing machine according to the present invention, 51 is the characteristic between the ink density and the dot gain as shown in FIG.
Is a characteristic between the ink density and the trapping as shown in FIG.

First, the principle of the present invention will be briefly described with reference to FIG. 1. In the present invention, the reference color coordinate value of the control target color in the profile-producing pattern printed matter 1 is set to G.
_{Let T} be a comparison of control target colors in the comparative printed matter 5 before color matching, which is printed in a state in which the color reproduction state is different from that at the time of profile creation, using a printing plate created based on the profile of the profile printed picture printed matter 1. When the use color coordinate value is G, the difference between the two colors, that is, the color coordinate value difference (ΔL *, Δa *, Δb *) 8 is calculated, and this color coordinate value difference (ΔL *, Δa *, Δb *) is calculated. ) 8 and the ink density of the comparative printed matter 5 as input, the color coordinate value difference (ΔL *, Δ
a *, Δb *) 8 ink density difference ΔD _C
34, ΔD _M 35, ΔD _Y 36, ΔD _K 37 so that the comparative printed matter 9 after color matching can be calculated.
It is the one that makes it possible to obtain.

By doing so, the color coordinate value G'of the control target color in the comparative printed matter 9 after color matching is
It can be made substantially equal to the reference color coordinate value G _T, and the color tone at the time of profile creation can be easily obtained even if the color reproduction state changes from that at the time of profile creation.

The present invention will be described in more detail below with reference to FIGS. 2, 3 and 4. First, the color chart 2 of the pattern-making pattern printed matter 1 printed with the standard ink film thickness shown in FIG. The patch of the control target color on the bar 3 is measured by a color tone measuring device (not shown), and the spectral reflectance is obtained. Then, for the control target color, the reference color coordinate value G _T (L _T *, a _T *, b _T *) 4 shown at the time of profile creation 41 in FIG. 4A is calculated, and the measurement result of the color chart 2 is calculated. Based on the profile, a profile is created, and based on the profile, a printing plate of the comparative printed matter 5 before color matching is created. Then, using the printing plate, the standard film thickness is used as in the case of creating the profile.
The comparative printed matter 5 before the color matching is printed.

In this printing, the color reproduction state of the printing machine is changed, and the color tone of the color to be controlled is different from that at the time of profile creation, and the color coordinate value is 40 before film thickness control in FIG. 4A. In the case of the position shown as, the control target color of the color bar 6 in the comparative printed matter 5 is measured by a color tone measuring device (not shown), and the spectral reflectance is calculated to obtain the spectral reflectance shown in FIG.
In addition to calculating the comparative color coordinate value G (L *, a *, b *) 7 shown as before film thickness control 40 in (A), the ink densities D _C , D in the comparative printed matter 5 before color matching are calculated.
_M , D _Y , D _K 31, dot gain DG _C , DG _M , D
G _Y , DG _K 32, trapping TR _B , TR _G , TR
_R 33 is calculated, and the color coordinate value for comparison G (L
*, A *, b *) 7 and the reference color coordinate value _{G T (L T *, a} T
*, B _T *) 4 is subjected to difference processing to obtain a color difference, that is, a color coordinate value difference (ΔL *, Δa *, Δb *) 8.

Then, adjust the ink key of the printing machine.
To change the ink film thickness and change the control target color to Fig. 4 (A).
The color coordinate value shown as 40 before film thickness control in the profile
Color matching so that it almost matches the color coordinate value of 41 when creating the file
To do. Then, the color bar in the printed matter 9 after color matching is
-Color coordinate value G '(L *, a *, b
*) 11 is calculated and the color coordinate value G '(L
*, A *, b *) 11 and standard color coordinate value G_T(L_T*, A
_T*, B_T*) 4 is almost the same as shown in 12.
Check and check the ink density on the printed matter for comparison 5 before color matching.
Degree D_C, D_M, D_Y, D_K31 for comparison after color matching
Ink density D in printed matter 9_C’、 D_M’、 D_Y’,
D_KInk density difference from ', ΔD_C34, ΔD_M35, Δ
D_Y36, ΔD _K37 is calculated.

These data, that is, the comparative color coordinate value G (L *, a *, b *) 7 and the reference color coordinate value G _T (L
_T *, a _T *, b _T *) 4 and color coordinate value difference (ΔL *, Δa
*, Δb *) 8, ink density D _C , D _M , D _Y , D _K 31, and dot gain D in the comparative printed matter 5 before color matching
G _C , DG _M , DG _Y , DG _K 32, trapping TR
_B , TR _G , TR _R 33, difference in ink density before and after color matching ΔD _C 34, ΔD _M 35, ΔD _Y 36, ΔD
_K 37 is calculated and stored for each color reproduction state different from that at the time of profile creation. Then, based on the plurality of accumulated data, the color difference, that is, the color coordinate value difference (ΔL
*, Δa *, Δb *) 8, and ink densities D _C , D _M , D _Y , D _K 31, and dot gains DG _C , D before color matching
_{G M, DG Y, DG K} 32, trapping _TR B, TR
By inputting _G and TR _R 33, the ink density difference ΔD _C 34, ΔD _M 35, ΔD _Y 36, and ΔD _K 3 of the control target color are input.
The function f38 shown in FIG. 3 for calculating 7 is defined. This function is, for example, ink density D, trapping T
The following formula (1) may be used, in which R and the dot gain DG are input, and the spectral wavelength R (λ) of the color to be controlled or the color coordinate values L *, a *, and b * are output. f {D, TR, DG, etc} → Color {R (λ), L *, a *, b *} (1) Note that this function is based only on the spectral wavelength and the color coordinate values in the Lab color system. However, as described above, the color coordinate values of the XYZ color system, the Luv color system, etc., and the wavelength band are divided into three by the main absorption wavelength band of each ink of cyan, magenta, and yellow, and the spectral reflectance for each wavelength band Needless to say, it may be a function for obtaining a value obtained by obtaining the integral value of.

If the function f is defined in this way,
Color tone in commercial printed matter is different from that in profile creation
In this case, as shown in FIG. 3, the color coordinate value difference of the control target color is 8,
Ink density 31 and dot gain 3 in commercial printed matter
2. By inputting trapping 33, profile
Ink density difference ΔD to reproduce the color tone at the time of creation
_C34, ΔD_M35, ΔD_Y36, ΔD_KGot 37
And control the ink key of the printing machine based on this ink density difference
Color profile easily and automatically when creating a profile
It is possible to obtain the key.

In daily commercial operation, the color coordinate value difference 8, ink density 31, dot gain 32, trapping 33, ink density difference ΔD _C 34, ΔD _M 35 is obtained every time a color reproduction state different from that at the time of profile creation. , ΔD _Y 3
6, the data such as ΔD _K 37 is accumulated, and the function f is updated, the more accurately the ink density difference ΔD _C 3
4, ΔD _M 35, ΔD _Y 36, and ΔD _K 37 are obtained, and the intelligent printing machine becomes smarter the more it is printed.

In the above description, it has been described that the function f is defined for the control target color, but in this case, a color other than the control target color, for example, a plurality of evaluation colors 43 as shown in FIG. 4B. , 45, 47 are deviated from the color coordinates 42, 44, 46 at the time of creating the profile, it becomes impossible to know how the film thickness control (ink density control) changes. Therefore, if a function f is similarly defined for a plurality of evaluation colors and it is possible to calculate how the evaluation colors change when the control target colors are color-matched, it is possible to calculate in advance each color. You can see how the color changes.

Further, although the specific color to be controlled is not mentioned in the above description, when gray is the color to be controlled, for example, gray is located in the center of the color space, and yellow, Since the three colors of magenta and cyan are used, it is possible to perform color matching of colors other than gray, and it is possible to easily and efficiently perform color matching. Also, in commercial printing, skin color, sky blue,
It is necessary to subtly adjust the color tone of specific colors such as green of trees.By defining functions for these colors, even when the color tone of these specific colors changes, the color tone at the time of profile creation can be easily adjusted. Therefore, it is possible to efficiently prepare before printing.

Further, in the above description, in defining the function f
To include dot gain DG and trapping TR
As described above, these values are as shown in FIGS. 5 and 6.
Has a correlation with the ink density D and has a constant relationship with the ink density D.
It changes with the staff. That is, in FIG.
(A) is cyan ink density D_CAnd dot gain DG_C
Graph showing the relationship between the two, (B) is the magenta ink density
D_MAnd dot gain DG_MGraph showing the relationship of
(C) is the yellow ink density D_YAnd dot gain DG
_Y(D) is a graph showing the relationship between
Degree D_KAnd dot gain DG_KIs a graph showing the relationship between
In FIG. 6, (A) is the cyan ink density D.
_CAnd blue overlaid with magenta M on cyan C
Trapping TR_BGraph showing the relationship with (B)
Is the cyan ink density D_CAnd yellow on cyan C
Green trapping TR with Y overprinted_GSeki
The graph showing the relationship, (C) is the magenta ink density D_M
And red overprinted with yellow Y on magenta M
Trapping TR_RIt is a graph showing the relationship with.

As can be seen from these graphs,
If the number of cases is constant, the ink density and dot gain on the printed matter
, Or the ink density and trapping amount are almost constant.
Tend to change over time. Therefore, based on the above-mentioned FIG.
As described in the explanation of the principle of the present invention based on
Value difference (ΔL *, Δa *, Δb *) 8 and ink density D_C, D
_M, D_Y, D_KInk density difference ΔD_CThree
4, ΔD_M35, ΔD_Y36, ΔD_KTo get 37
Is possible, and furthermore, this ink density difference ΔD_C34,
ΔD_M35, ΔD_Y36, ΔD_KGot exactly 37
Therefore, these ink density-dot gain characteristics (D-DG characteristics
Properties), ink density-trapping characteristics (D-TR characteristics)
May be added to the parameter to define the function f.

FIGS. 7 and 8 show another embodiment in which the function f used in the color tone control method in the printing machine according to the present invention is defined in accordance with the above idea. In FIGS. 7 and 8, 51 is an ink density-dot gain characteristic (D-DG characteristic), and 52 is an ink density-trapping characteristic (D-TR).
Characteristics), and in the embodiment of FIG. 7, these color coordinate value differences (Δ
By inputting L *, Δa *, Δb *) 8, ink density-dot gain characteristic (D-DG characteristic) 51, and ink density-trapping characteristic (D-TR characteristic) 52, the ink density difference ΔD _C 34, A function f50 for obtaining ΔD _M 35, ΔD _Y 36, and ΔD _K 37 is defined, and in the embodiment of FIG.
In addition to these color coordinate value differences (ΔL *, Δa *, Δb *) 8, ink density-dot gain characteristics (D-DG characteristics) 51, ink density-trapping characteristics (D-TR characteristics) 52,
Ink density D of each color in comparative printed matter before color matching
By inputting _C , D _M , D _Y , and D _K 31, the ink density differences ΔD _C 34, ΔD _M 35, ΔD _Y 36, and ΔD _K 3
The function f53 for obtaining 7 is defined.

That is, as shown in FIG. 7, the color coordinate value difference (ΔL
*, Δa *, Δb *) 8, ink density-dot gain characteristics (D-DG characteristics) 51, and ink density-trapping characteristics (D-TR characteristics) 52 are input. When the ink density is changed by the dot gain characteristic (D-DG characteristic) 51 and the ink density-trapping characteristic (D-TR characteristic) 52, that is, the ink density difference ΔD _C 34, ΔD _M 35, ΔD _Y 3
6, it is possible to predict how the dot gain and the trapping will move when ΔD _K 37 is given, so that it is possible to predict how much the color coordinate value will move, and thereby the color tone adjustment can be performed more accurately. it can. Further, as shown in FIG. 8, in addition to the ink density-dot gain characteristics (D-DG characteristics) 51, the ink density-trapping characteristics (D-TR characteristics) 52, the ink densities D _C , D _M , D _Y , D _K 3
When 1 is also input, the point corresponding to the ink density 31 in these ink density-dot gain characteristics (D-DG characteristics) 51 and ink density-trapping characteristics (D-TR characteristics) 52 can be specified, so color tone adjustment It can be done more accurately.

In the above description, trapping between cyan and magenta (TR _B ), cyan and yellow (TR _G ), and magenta and yellow (TR _R ) is used as trapping. There are black and cyan, black and magenta, and black and yellow, which may be used as necessary. Further, in the above description, the case where the function f is defined on the assumption of four colors of cyan, magenta, yellow, and black has been described, but it is also possible to use only three colors of cyan, magenta, and yellow and not use black. The same configuration is possible, and in this case, the ink densities D _C , D _M , D _Y , and D _K 31 of the comparative printed matter before color matching, the dot gains DG _C , DG _M , DG _Y , and DG _K 32, and the output are the same. Ink density difference ΔD _C 34, ΔD _M 35, ΔD _Y 3
6, the black component in ΔD _K 37, that is, the ink density D _K , the dot gain DG _K , the ink density difference ΔD
_The function f may be defined excluding _K 37.

[0044]

As described above, according to the present invention described in claim 1, from the difference in color between the control target colors in the profile printed picture printed matter and the commercial printed matter, and the ink density of the commercial printed matter, the commercial By making it possible to calculate the ink density difference that makes the color tones of the control target colors in the printed matter and the pattern printed matter for profile creation approximately match, it is possible to easily reproduce a color reproduction state that is close to the color reproduction state at the time of profile creation. It is possible to easily and easily control the color tone without inputting the target spectral reflectance and measuring the OK sheet.

According to the second aspect of the present invention, the color difference between the control target colors in the profile-designed pattern printed matter and the comparative printed matter printed in a color reproduction state different from that at the time of profile creation, By defining a function from the ink density in the comparative printed matter and the ink density difference that causes the control target color of the comparative printed matter to substantially match the control target color in the profile design picture printed matter, the ink density in the commercial printed matter By inputting the color difference between the control target color of the profile creation picture print and this function, it is possible to obtain the ink density difference that makes the color tones of the commercial print and the profile creation picture print approximately match, and to obtain the target. To easily control the color tone by calculating the density difference without inputting the spectral reflectance or measuring the OK sheet. It can be.

According to the present invention as set forth in claims 3 and 4, since the ink density, the dot gain, and the trapping amount are originally correlated with each other, if the ink density is known, the commercial printed matter and the profile design picture printed matter can be obtained. The function that outputs the ink density difference that makes the color tones of the control target color substantially match can be defined, but it is necessary to add or use the dot gain and the trapping amount, or the ink density-dot gain characteristic and the ink density-trapping characteristic in this way. As a result, the definition of the function and the calculation of the ink density difference for controlling the color tone in the commercial printed matter can be performed more accurately and easily.

Then, according to the present invention as set forth in claim 5, by defining the function with respect to the gray patch,
Gray is located in the center of the color space and uses the three colors of yellow, magenta, and cyan, so you can also match colors other than gray, and you can easily and efficiently match colors. It will be possible.

Further, according to the present invention as defined in claim 6, a function is defined for a specific color such as skin color, sky blue, and green of trees which needs to be finely adjusted in color tone in commercial printing. By setting the color tone, the color tone at the time of profile creation can be easily obtained even when the color tone of these specific colors changes, and efficient pre-print preparation becomes possible.

[Brief description of drawings]

FIG. 1 is a diagram for explaining the principle of a color tone control method in a printing machine according to the present invention.

FIG. 2 is a diagram for explaining a method of creating data for defining a function used in the color tone control method in the printing machine according to the present invention.

FIG. 3 is a diagram for explaining a function used in a color tone control method in a printing machine according to the present invention.

FIG. 4 is a diagram for explaining a color tone control method in the printing machine according to the present invention.

FIG. 5 is a graph showing a correlation between ink density and dot gain.

FIG. 6 is a graph showing a correlation between ink density and dot gain.

FIG. 7 is a diagram for explaining another embodiment of the function used in the color tone control method in the printing machine according to the present invention.

FIG. 8 is a diagram for explaining another embodiment of the function used in the color tone control method in the printing machine according to the present invention.

[Explanation of symbols]

8 Color coordinate value difference (ΔL *, Δa *, Δb *) 31 Ink density of each color in the comparative print before color matching 32 Dot gain of each color in the comparative print before color matching 33 In the comparative print before color matching Trapping of each color 34, 35, 36, 37 Change in ink density 38 Function f

─────────────────────────────────────────────────── ─── Continued Front Page (51) Int.Cl. ⁷ Identification Code FI Theme Coat (Reference) H04N 1/46 ZF Term (Reference) 2C250 DB04 EA23 EB32 EB40 2G020 AA08 DA02 DA03 DA04 DA05 DA12 DA34 DA43 5C074 AA11 BB16 DD01 DD16 DD26 FF07 FF15 HH04 5C077 MM27 MP08 PP34 PP36 PP37 TT08 5C079 HB03 HB08 HB12 LA02 LB02 NA03 NA27 PA07

Claims (6)

[Claims] 1. A printing plate is prepared on the basis of a profile (coloring characteristic data) describing a correspondence relationship between a halftone dot area ratio of a printing press and color development, and a control target color of a commercial print by the printing plate is measured. A color tone control method in a printing press for controlling a color tone, comprising: a commercial printed matter and the profile creation based on a color difference in control target colors between the profile printed picture printed material and the commercial printed material, and an ink density of the commercial printed material. A color tone control method for a printing press, comprising: calculating an ink density difference that substantially matches the color tones of control target colors in a printed design print, and controlling the ink key of the printing press based on the ink density difference to control the color tone. 2. The ink density difference that causes the color tones of control target colors in the profile-printed pattern printed matter and the commercial printed matter to substantially match is different from each other in a plurality of comparisons printed in a plurality of color reproduction states different from those in the profile creation. Of the color difference in the control target colors of the printed matter for printing and the profile printed design printed matter, the ink density in each of the comparative printed matter, and the color tone of the controlled target color in each of the comparative printed matter and the profile created design printed matter. Accumulated ink density differences are accumulated as data, and based on the accumulated data, the color difference between the control target colors in the profile creation picture printed matter and the commercial printed matter and the ink density of the commercial printed matter are input. The color tones of the control target color in the commercial printed matter and the profile-designed picture printed matter are substantially the same. 2. The calculation is performed by a function defined so that the ink density difference according to
A color tone control method for a printing machine described in 1. 3. The dot gain and the trapping amount, or the ink in each of the profile creation picture printed matter, the comparative printed matter, and the commercial printed matter, when calculating the ink density difference for controlling the color tone in the commercial printed matter and the definition of the function. 3. The color tone control method for a printing press according to claim 2, wherein the density-dot gain characteristic and the ink density-trapping characteristic are added. 4. When the definition of the function and the calculation of the ink density difference for controlling the color tone in the commercial print, the ink density in each of the profile creation picture print, the comparative print and the commercial print is replaced with the ink density. The method according to claim 2, wherein the dot gain characteristic and the ink density-trapping characteristic are used. 5. The color tone control method for a printing press according to claim 1, wherein the control target color is gray. 6. The color tone control method for a printing press according to claim 1, wherein the color to be controlled is a specific color such as a flesh color, sky blue, and green of trees.