JP3269831B2 - Method and apparatus for controlling ink pigment concentration - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an color management technology in the printing machine such as a gravure printing machine, and more particularly to ink pigment concentration control method and apparatus.

[0002]

2. Description of the Related Art Conventionally, to perform color management in a gravure printing machine, (1) a certain amount of ink is collected from ink used in a printing unit, and only pigment is centrifuged, solvent washed, and dried. Separate and measure the weight, obtain the pigment concentration by calculation, and manage the pigment concentration. (2) Collect a part of the ink used in the printing unit and display it with a small color printer. A method of measuring and managing the color and the developed product visually or as a color difference or an optical density difference with an optical densitometer or a spectrophotometer, etc. (3) Visual inspection of the ink layer of the actually printed printed matter, an optical densitometer, a spectrophotometer A method of managing color differences and optical density differences with a meter or the like has been performed.

[0003]

However, all of the conventional methods have problems. That is, in these methods, measurement takes time, and it is not possible to control the color tone of the ink and the optical density of the ink in the printed matter online and in real time while printing. Furthermore, the above (3)
In the method described in (1), when the error from the target color was found to be outside the allowable limit, all the printed matter was defective, and the loss was large.

[0004] The present invention has been made in view of the above problems, the printing press, the pigment in the ink in real time
Measuring concentration and controlling it to a specified value
It is an object of the present invention to provide a method and an apparatus for controlling the concentration of an ink pigment which can be performed .

[0005]

[0006]

Means for Solving the Problems Ink pigment concentration of the present invention
A control method and apparatus are provided in a printing press for controlling a printing unit .
Between the ink pan and the ink tank for ink adjustment.
To circulate the pump,
The ends of a pair of optical fibers face each other on the same axis.
So that there is a gap between the end faces where the ink flows.
Insert and fix the optical fiber
Light is projected into the ink passing through the gap, and the other optical fiber
Receives the light that has passed through the ink with the
To measure the pigment concentration by detecting at
Depending on the measured value, the ink tank may be filled with high density ink or ink.
It is configured to supply an ink diluent .

[0007]

[0008]

The method for controlling the concentration of the ink pigment of the present invention as described above, and
In the device, the ink pan and ink tank of the printing unit
In the flow of ink circulating between the two ends, the ends of the pair of optical fibers are arranged so as to face each other on the same axis, and to form a gap through which ink flows between the two end faces. The ink passing through the gap is irradiated with light through the optical fiber, the transmitted light is received by the other optical fiber, and the amount of light can be detected by the photodetector. Since the amount of transmitted light is determined by the amount of incident light, the wavelength range of the incident light, the size (thickness) of the gap through which the ink passes, the flow rate of the ink (flow velocity), the color of the pigment, the pigment concentration, etc., specify factors other than the pigment concentration. By doing so, the amount of transmitted light becomes a value corresponding to the pigment concentration, and a signal (voltage, current, etc.) corresponding to the amount of transmitted light detected by the photodetector becomes a signal indicating the pigment concentration. Thus, the pigment concentration can be measured from the output signal from the photodetector. Here, the incident light amount may be fixed, and the output signal from the photodetector may be used as it is as the pigment concentration, or the output signal may be subjected to arithmetic processing to obtain, for example, transmittance (output light amount / input light amount). Alternatively, a signal corresponding to the optical density [−Log ₁₀ (output light quantity / input light quantity)] may be obtained, and the signal may be used as the pigment density. The greater the size of the gap formed between the end faces of the pair of optical fibers, the greater the amount of ink between them and the higher the accuracy, but the greater the amount of light emitted and the more stable the ink flow. May be reduced, and may be determined in consideration of these factors.

In the present invention, as described above, the tip of the optical fiber for measuring the transmitted light amount of the ink is arranged in the flow of the ink. For this reason, there is no error between the end face of the optical fiber and the ink, and there is no light loss at the interface, so that the S / N ratio is high and high-precision measurement is possible. If you do not use optical fiber,
When trying to measure the amount of transmitted ink using a light receiver,
As shown in FIG. 4, the ink 41 flows into the air from the tube 40, and the light emitter 42 and the light receiver 43 are arranged on both sides of the ink 41. Alternatively, as shown in FIG. A window 45 made of a transparent plate is formed on the side
A configuration in which the light emitter 42 and the light receiver 43 are arranged outside the window 45 is conceivable. However, with this configuration,
In the case of FIG. 4, the reflection, refraction, and the change with time at the interface between the ink, the window, and the air at the interface between the ink and the window in the case of FIG.
In the present invention, these disadvantages can be solved by disposing the tips of the pair of optical fibers in the flow of ink. Further, in the present invention, by using a pair of optical fibers, the light source and the photodetector do not come into direct contact with the ink, so that the light source and the photodetector do not become contaminated or damaged, thereby making maintenance easier. There is also.

The light source used in the present invention may be appropriately determined according to the type of the pigment in the ink. When measuring the pigment concentration of an ink in which the hue is the same and only the brightness is changed (the compounding ratio of each color pigment contained in the ink is always the same and only the concentration of each color pigment as a whole is changed) As the light spectrum of the light source, it is preferable to use white light including the entire visible region. In this case, since the pigment composition does not change, light having only a specific band of spectrum (including monochromatic light such as laser) may be used. The transmittance of a specific wavelength (band) can be detected on behalf of the total color pigment concentration. Infrared rays or ultraviolet rays may be used as long as there is a correlation with the concentration of all color pigments.

When measuring the pigment concentration of an ink in which the hue changes (the concentration and the ratio of each color pigment contained in the ink changes), a white light source is used, and if the pigment is only the three primary colors of yellow, red and blue. For example, by arranging a filter on the light source or photodetector side, by measuring the amount of transmitted color light corresponding to each pigment color, the concentration of each color pigment can be measured. In addition, in the case of an ink comprising a special color pigment other than the three primary colors, the spectral transmittance or the tristimulus value (X, Y, or S) over the entire visible wavelength range (wavelength 3800 to 7800 angstroms)
By measuring Z), the concentration of each color pigment can be measured.

The ink for which the pigment concentration is measured in the present invention is mainly a low-viscosity gravure ink. As the pigment, any pigment that absorbs at least a certain wavelength (infrared rays or ultraviolet rays can be used) can be used. For example, red iron pigments such as quinacridone, yellow pigments such as graphite, blue pigments such as phthalocyanine blue and navy blue, black pigments such as carbon black, further, metal powder pigments, pearls such as titanium oxide-coated mica Pigments and the like, and extender (matte) pigments such as silica and calcium carbonate.

As described above, in the present invention , the printing unit
Of ink circulating between the ink pan and the ink tank
Since the pigment concentration can be measured,
Supply high concentration ink or ink diluent to the tank
This makes it possible to set the ink pigment concentration online and in real time.
System .

[0014]

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention shown in the drawings will be described below in detail. FIG. 1 is a schematic sectional view showing an embodiment in which the present invention is applied to a gravure printing machine, and 1 is a printing unit. The printing unit 1 includes an ink pan 3 capable of storing a predetermined amount of ink 2, a plate cylinder 5 for printing on a base paper web 4, an impression cylinder 6, a doctor blade 7, and the like. Reference numeral 9 denotes an ink tank for adjusting the ink, and a stirring propeller 10
It has. 11 is an ink pan 3 and an ink tank 9
And a circulation pipe for circulating the ink between the ink supply pipe 11a and the ink supply pipe 11a and the ink return pipe 11b. Reference numeral 12 denotes a pump attached in the middle of the ink supply pipe 11a, and a gear pump is usually used so that a steady flow without pulsation can be secured. It should be noted that other pumps may be used as long as the pump does not contain bubbles or pulsation. Reference numeral 13 denotes a buffer tank arranged in the middle of the ink supply pipe 11a, which is provided to absorb and reduce fluctuations in the flow rate of ink flowing through the ink supply pipe 11a, or to capture and remove air bubbles.

Reference numeral 15 denotes an ink pigment concentration measuring device for measuring the pigment concentration of the ink flowing in the ink supply pipe 11a. The ink pigment concentration measuring device 15 includes a pair of optical fibers 16a and 16b,
a, a light source 18 and a photodetector 19 mounted inside the case 17 and connected to respective ends of the optical fibers 16a, 16b. Although not particularly limited, white light is used as the light source 18. The photodetector 19 outputs an electric signal corresponding to the amount of received light, for example, a voltage, a current, or the like, and may use, for example, a photodiode, a phototransistor, a phototube, or the like. As shown in an enlarged manner in FIG. 2, mounting brackets 20 are respectively attached to the outer peripheries of the distal ends of the optical fibers 16 a and 16 b, and the distal ends of the optical fibers 16 a and 16 b use the mounting bracket 20, respectively.
The ink supply pipe 11a is inserted and fixed so as to face each other on the same axis extending in a direction perpendicular to the axis of the pipe, and to form a gap 21 between the end faces through which ink flows. Thus, when the ink steadily flows into the ink supply pipe 11a, a part of the ink steadily flows through the gap 21, and the light from the light source 18 is projected onto the ink passing through the gap 21 through one optical fiber 16a. The light transmitted through the ink is sent to the photodetector 19 through the other optical fiber 16b, and the photodetector 19 detects the amount of the light, so that an electric signal corresponding to the pigment concentration of the ink can be output. Here, it is preferable that the mounting positions of the tips of the optical fibers 16a and 16b be places where the ink flows stably, and for this reason, they are linear portions of the ink supply pipe.

In FIG. 1, reference numeral 23 denotes a high-concentration ink supply device for supplying high-concentration ink to the ink tank 9;
It has a high-concentration ink tank 24 containing high-concentration ink, a supply pipe 25, a solenoid valve 26 and the like. Here, the high-density ink contained in the high-density ink tank 24 has the same hue as the ink used for printing (the mixing ratio of each color pigment contained in the ink is the same). It was raised. Reference numeral 28 denotes a solvent,
This is an ink diluent supply device for supplying an ink diluent such as a medium. The ink diluent supply device 28 also includes an ink diluent tank 29 containing the ink diluent and a supply pipe 3.
0, a solenoid valve 31 and the like. The high-concentration ink supply device 23 supplies high-concentration ink to the ink tank 9 when the pigment concentration of the ink in the ink circulation system including the ink pan 3, the ink tank 9, the circulation pipe 11, and the like is reduced. When the pigment concentration of the ink in the ink circulation system becomes high, the ink diluent supply device 28 supplies the ink diluent to the ink tank 9 to lower the pigment concentration in the ink circulation system. It is for. Here, as described above, since the high-concentration ink has the same hue as the ink used for printing, even if the high-concentration ink or the ink diluent is supplied to the ink tank 9, the ink in the ink circulation system is The hue does not change, and only the brightness increases or decreases due to the change in the pigment concentration.

Reference numeral 33 denotes a control device for controlling the supply amounts from the high-concentration ink supply device 23 and the ink diluent supply device 28 based on the values measured by the ink pigment concentration measurement device 15. The control device 33 in the present embodiment includes a first comparator 34, a second comparator 35, and an AND circuit 3
6, a NOR circuit 37, a solenoid valve control circuit 38, and the like. The first comparator 34 obtains a signal corresponding to the upper limit value of the pigment concentration (wt%) in the ink used for printing in advance, which is to be allowed (that is, the signal obtained from the photodetector 19 when the ink having the upper limit value is measured). V _MIN is set, the real-time signal V _IN from the photodetector 19 is compared with the set signal V _MIN, and H is set according to the magnitude of the set signal V _MIN.
And outputs (High) signal or L a (Low) signal as an output C _1. Also, the second comparator 35
Has previously set a signal V _MAX corresponding to the lower limit of the concentration of the pigment in the ink used for printing, which is tolerable. The signal V _IN from the photodetector 19 is set to the set signal V _MAX.
Compared with _MAX , outputs H or L signal according to the magnitude.
Output as ₂ . FIG. 3 is a graph showing operation curves of the first and second comparators 34 and 35. Here, the signals (V _IN , V
_MIN , _VMAX ) are obtained from the amount of transmitted ink, so that the higher the pigment concentration, the lower the signal.

The solenoid valve control circuit 38 responds to signals from the AND circuit 36 and the NOR circuit 37 to control the solenoid valves 26 and 31.
Is controlled to open and close as shown in Table 1.

[0020]

[Table 1]

Next, the operation of the apparatus having the above configuration will be described. During printing, the pump 12 operates, and supplies the ink in the ink tank 9 to the ink pan 3 through the ink supply pipe 11a. Excess ink in the ink pan 3 is returned to the ink tank 9 through the ink return pipe 11b. Thus, the ink circulates through the ink tank 9 and the ink pan 3.

During the circulation of the ink, a pair of optical fibers 16a, 1a are inserted into the ink supply pipe 11a.
The photodetector 19 of the ink pigment concentration measuring device 15 measures the amount of light passing through the gap 21 formed in the gap 21 formed between the end faces of the front end of the ink pigment 6b.
The amount of transmitted ink is a value corresponding to the pigment concentration of all the colors in the ink if the mixing ratio of each color pigment in the ink is constant. In this embodiment, since the high-concentration ink having a constant blending ratio is replenished in the ink circulation system, the blending ratio of each color pigment is always constant. Therefore, the amount of transmitted ink detected by the photodetector 19 is a value corresponding to the pigment concentration of all colors in the ink, and the pigment concentration is measured. Here, a pair of optical fibers 16a, 1
6b is inserted into the linear portion of the ink supply pipe 11a, so that the ink flow in that portion is stable, and a pump 12 with little pulsation and a buffer tank 13 are used. As a result, the speed fluctuation is extremely small, whereby the transmitted light amount according to the pigment concentration of the ink can be measured with high accuracy. Further, the optical fibers 16a, 1
Since the end of 6b is in direct contact with the ink, no air or other material is interposed between the ink and the ink, so that no error occurs at the ink interface, and more accurate measurement is possible. .

During the circulation of the ink, the ink pigment concentration measuring device 15 constantly measures the pigment concentration of the ink passing through the ink supply pipe 11a, and sends the detection signal V _IN to the first and second comparators 34 and 35. Output. The first and second comparators 34 and 35 determine how the pigment concentration of the ink is with respect to the upper and lower limits to be allowed, and as shown in Table 1 above, the solenoid valves 26 and
31 is controlled. That is, when the pigment concentration of the ink is lower than the lower limit value to be allowed (therefore, when the transmitted light amount is large and V _MAX ≤ V _IN ), the solenoid valve of the high-density ink supply device 23 26 is opened to supply high-concentration ink to the ink tank 9. This increases the pigment concentration in the ink circulation system. Conversely, when the pigment concentration of the ink is higher than the upper limit that should be allowed (when the amount of transmitted light is small and V _IN ≦ V _MIN )
To open the solenoid valve 31 of the ink diluent supply device 28,
The diluent is supplied to the ink tank 9 to reduce the pigment concentration in the circulation system. Thus, the pigment concentration of the ink in the ink circulation system is controlled in real time so as to fall between the upper limit value and the lower limit value to be allowed, and printing is performed in the printing unit 1 with the pigment concentration within the allowable range.

In the above embodiment, the solenoid valves 26 and 31 are turned on / off (binary) by the detection signal of the ink pigment concentration measuring device 15, but the present invention is not limited to this. Other control methods may be adopted. For example,
In order to control the ink pigment concentration to a fixed value more precisely and with a small fluctuation width, a detection signal corresponding to the amount of transmitted light from the photodetector 19 [or a transmittance calculated from the detected signal (output light amount / input light amount)] Corresponding to the target pigment concentration and the difference (analog amount) between the setting signal corresponding to the target pigment concentration quantitatively (proportional to the difference, proportional to the differential value of the difference,
A method of continuously varying and controlling the flow rates of the high-concentration ink and the ink diluent flowing through the supply pipes 25 and 30 by an amount equivalent to the integral value of the difference) may be used.

Although the embodiment in which the measurement and control of the concentration of all color pigments are performed when the mixing ratio of each color pigment is fixed has been described above, the present invention is not limited to this case. And its ratio (ie, hue, lightness, and saturation of the ink)
Can be detected and controlled. Pigment is yellow, red,
If only the three primary colors of blue are used, by using a device similar to the ink pigment concentration measuring device 15 shown in FIGS. 1 and 2 and disposing a filter on the light source or the photodetector side, the color light corresponding to each pigment color can be obtained. Is measured, and each color pigment ink may be replenished according to the measured value. In the case of an ink composed of a special color pigment other than the three primary colors, the spectral transmittance or the tristimulus value (X, Y, Z) over the entire visible wavelength range (wavelength 3800 to 7800 angstroms) is measured, and the spectral transmittance or the tristimulus value is measured. What is necessary is just to increase or decrease the replenishment amount of each color pigment ink so that the stimulation value matches the target value. The replenishment amount may be calculated by applying a known color mixing and color matching theory and technique. In this case, the color is controlled to the target color. At this time, the light source and the light detector used in the ink pigment concentration measuring device are configured as a spectrophotometer. (1) White light is incident on the ink from a light source through an optical fiber, the transmitted light is separated by a prism, a diffraction grating, or the like, and the transmitted light amount of each wavelength is sequentially measured. (2) The lights separated by a prism, a diffraction grating, etc. are sequentially
The light enters the ink through an optical fiber for each wavelength, and the amount of transmitted light is detected.

[0026]

As described above, the method and the apparatus for controlling the concentration of the ink pigment according to the present invention can be used in a printing machine.
Knitted ink pan and ink tank for ink adjustment
The ink is circulated between them, and the circulation
Insert the ends of a pair of optical fibers into a tube on the same axis.
To form a gap through which the ink passes
Insert and fix as described above through one optical fiber
Light is projected into the ink passing through the gap, and the other optical
The bar receives the light transmitted through the ink and detects the amount of light.
And measure the pigment concentration by detecting the pigment concentration.
Depending on the measured value of the ink tank, high density ink or
It is designed to supply ink diluent.
Measures the pigment concentration of the ink during printing in real time
And control the ink pigment concentration according to the measured value.
It is possible to always print with ink of desired pigment concentration
That high quality printed matter can be obtained.
Has an effect.

[0027]

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram showing an embodiment in which the present invention is applied to a gravure printing machine.

FIG. 2 is a schematic cross-sectional view showing, on an enlarged scale, a portion in which the tips of a pair of optical fibers are inserted into an ink supply pipe in the embodiment.

FIG. 3 is a graph showing characteristic curves of first and second comparators;

FIG. 4 is a schematic side view showing one example of a device that measures the pigment concentration of ink based on the amount of transmitted light.

FIG. 5 is a schematic cross-sectional view showing another example of an apparatus that measures the pigment concentration of ink based on the amount of transmitted light.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Printing unit 2 Ink 3 Ink pan 4 Base paper web 5 Plate cylinder 6 Impression cylinder 9 Ink tank 11 Circulation piping 11a Ink supply pipe 12 Pump 13 Buffer tank 15 Ink pigment concentration measuring device 16a, 16b Optical fiber 18 Light source 19 Light detector 20 Mounting bracket Reference Signs List 21 gap 23 high-concentration ink supply device 26 solenoid valve 28 ink diluent supply device 31 solenoid valve 33 control device

Continuation of the front page (56) References JP-A-1-113244 (JP, A) JP-A-61-230727 (JP, A) JP-A-47-27885 (JP, U) JP-A-58-65556 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) B41F 31/00-31/38 G01N 21/00-21/61 B41F 31/02 Practical file (PATOLIS) Patent file (PATOLIS) ECLA WPI / L (QUESTEL)

Claims (2)

(57) [Claims] An ink is circulated between an ink pan of a printing unit and an ink tank for ink adjustment.
Insert the ends of a pair of optical fibers into the ink flow.
The ink is placed so as to face each other on one axis and between the end faces.
Place one of the optical fibers so as to form a flowing gap
Light into the ink passing through the gap
And receives the light transmitted through the ink by the other optical fiber
The amount of light is detected by a photodetector to measure the pigment concentration ,
A method for controlling the concentration of an ink pigment, comprising controlling the supply amounts of a high-concentration ink and an ink diluent to the ink tank according to the measured value. 2. An ink pan of a printing unit, an ink tank for adjusting ink, a circulation pipe and a pump for circulating ink between the ink pan and the ink tank, and a high density for supplying a high density ink to the ink tank. an ink feeder, and an ink diluting fluid supply device for supplying ink dilution liquid to the ink tank, and Lee Nki pigment concentration measuring device arranged to measure the ink concentration in the circulation pipe, the ink pigment concentration measurement based on the measurements by the apparatus have a controller for controlling the supply from the high-concentration ink supply device and the ink diluting liquid supplying apparatus, the ink face
The ink concentration measuring device is connected to the tube through which the ink flows.
A pair of optical fibers, each end of which is inside the tube
And between the end faces so as to face each other on the same axis.
To secure the gap where the fluid flows.
Outside the tube of the pair of optical fibers and one of the optical fibers
At the end located on the side of the
The light source to irradiate and the outside of the tube of the other optical fiber
Is located at the end where the optical fiber is located.
Photodetector to detect the pigment concentration in the ink.
An ink pigment concentration control device characterized in that it is configured to detect the amount of light detected by an output device.