JPH0854371A - Apparatus for measuring moisture content of printing ink - Google Patents

Abstract

PURPOSE:To improve a reliability of an apparatus by making the apparatus possible to automatically measure/control a moisture content of a printing ink of an Indian ink color and to be easily set in any printing machine. CONSTITUTION:A corona charger 25 is arranged in the vicinity of the surface of a conductor roller 21 among a group of ink rollers of a printing machine, and surface potential-measuring devices 27, 28 are disposed on the downstream side from the corona charger 25. A moisture content is obtained by measuring a charge potential. Although the charge potential is proportional to a film thickness of a printing ink, the film thickness can be measured by the photoacoustic technique even in the case of an Indian color ink. Therefore, the moisture content of the Indian color ink can be identified by measuring the charge potential and the film thickness after obtaining a calibration graph of relation between the charge potential and the moisture content per 1mum of a printing ink of a known moisture.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a water content measuring device for printing ink, particularly for measuring the water content of black ink.

[0002]

2. Description of the Related Art Conventionally, an optical sensor has been put into practical use as a water content sensor for printing inks other than black ink. A typical example thereof will be described with reference to FIG. 6. This water content sensor utilizes the fact that the absorption wavelength of infrared rays differs between the printing ink and water, and the ratio of the absorption rates at each absorption wavelength (water content) Is to seek.

The water content sensor will be described in detail below.
The light emitted from the infrared light emitter 1 is condensed by the lens 2 and passed through the interference filter 3. This interference filter 3 includes
Water absorption wavelength λ _w , printing ink absorption wavelength λ _i , and reference wavelength λ _r that is not absorbed by water / printing ink are installed. The infrared rays of (3) are applied to the printing ink film (emulsified ink film) 6 on the printing ink roller 5 through the optical conduit 4.

Then, the reflected light from the printing ink film 6 is received by the photoelectric element 7 and is amplified by the amplifier 8 to be A / D.
The data is output to the converter 9 to convert the analog signal into a digital signal, the digital signal is sent to the computer 10, processed there, and then recorded on the plotter 11. Reference numeral 12 is a synchronizer.

[0005]

In the conventional moisture content sensor shown in FIG. 6, the black ink absorbs light in a wide range from infrared to ultraviolet. Therefore, the water content of the black ink should be measured. Not applicable. A method that indirectly obtains information about the water content from the ultrasonic waves generated during ink separation cannot be applied to the actual printing machine due to noise, etc., and is directly related to the water content. There is a demand for a completely new printing water content measuring device capable of identifying the water content by measuring the physical properties of the printing ink.

The present invention has been proposed in view of the above problems, and an object thereof is to automatically measure and control the water content of a black-color printing ink, which is easy for any printing machine. The present invention aims to provide a water content measuring device for printing ink which can be installed in the device and can improve the reliability of the device.

[0007]

In order to achieve the above object, the apparatus for measuring the water content of a printing ink of the present invention has a corona charger in the vicinity of the surface of a conductor roller in an ink roller group of a printing machine. However, a surface potential measuring device is arranged downstream of the corona charger. In the water content measuring device for the printing ink, the water content in the ink is calculated based on the measured values from the ink film thickness measuring device arranged near the surface of the conductor roller and the ink film thickness measuring device and the surface potential measuring device. It may be provided with a computing unit for performing.

[0008]

The apparatus for measuring the water content of printing ink according to the present invention is constructed as described above, and has the following functions. That is, the electric resistance of the printing ink changes greatly depending on the water content, and the charge holding ability also changes. Therefore, the water content can be obtained by measuring the charge potential. This charging potential is
Although proportional to the film thickness of the printing ink, the film thickness can be measured by the photoacoustic method or the like even in the case of the black printing ink. Therefore, if the relationship between the charging potential per 1 μm and the water content of a printing ink having a known water content is set in advance in a calibration graph, the water content of the black printing ink can be identified by measuring the charging potential and the film thickness. is there.

[0009]

EXAMPLES Next, the water content measuring apparatus for printing ink of the present invention will be explained with reference to the examples shown in the drawings. FIG. 1 shows the water content measuring apparatus for printing ink of the present invention. 21 of FIG.
Is a conductor roller (copper-plated metal roller), 22 is a printing ink film on the copper-plated metal roller 21, 23 is a deposition roller, and 24 is a plate cylinder.

A corona charger 25 is provided near the surface of the copper-plated metal roller 21, and a corona charger 2 is provided 26.
5, a high-voltage power supply connected to 5, a surface potential measuring head 27 disposed downstream of the corona charger 25, a surface potential measuring device main body 28 connected to the surface potential measuring head 27,
Reference numeral 29 denotes an ink film thickness measuring device disposed on the downstream side of the surface potential measuring device head 27, and 30 denotes the surface potential measuring device main body 2
8 and the ink film thickness measuring device 29.

In the above-mentioned water content measuring apparatus for printing ink, a corona charger 25 and a surface potential measuring device 27 are sequentially arranged in the circumferential direction around one conductor roller 21 of the ink supply system of the printing machine.
28 are provided. A corona charger is used as the charger 25, and surface potential meters are used as the surface potential measuring devices 27 and 28. For corona charging, the highest accuracy can be obtained by the pulse charging method in which the conductor roller 21 is charged once for one revolution, and then the charging is stopped for a time when the charging potential is sufficiently attenuated.

The following functions are carried out in the water content measuring device for printing ink. That is, the electric resistance of the printing ink changes greatly depending on the water content, and the charge holding ability also changes. Therefore, the water content can be obtained by measuring the charge potential. This charging potential is proportional to the film thickness of the printing ink, but the film thickness can be measured by the photoacoustic method or the like even in the case of black printing ink. Therefore, if the relationship between the charging potential per 1 μm and the water content of a printing ink having a known water content is set in advance in a calibration graph, the water content of the black printing ink can be identified by measuring the charging potential and the film thickness. is there.

In order to verify the principle of the apparatus for measuring the water content of the above printing ink, an experiment was carried out by the ink transfer test apparatus shown in FIG. In FIG. 2, 21 is a copper-plated metal roller (conductor roller), 22 is a printing ink film on the copper-plated metal roller 21, 25 is a corona charger, 26 is a high voltage power supply, and 31 is a function generator.

Reference numeral 27 is a surface potential measuring device head disposed downstream of the corona charger 25, 28 is a surface potential measuring device main body, 32 is a recorder, and 33 is a film thickness / water content meter. Three
Reference numerals 4 and 35 are rubber rollers, 36 is a swing roller, 37 is a chrome-plated metal roller, 38 is a rubber roller, and 39 is dampening water. In the initial state, the rubber roller 35 is separated from the chrome-plated metal roller 37. In this state, the rocking roller 36 is coated with an appropriate amount of printing ink, and the rubber roller 3
4. The copper-plated metal roller 21 and the swing roller 36 are rotated in association with each other to form a uniform printing ink film on these three rollers.

Then, the rubber roller 35 is brought into contact with the copper-plated metal roller 21, and dampening water 29 is supplied to the copper-plated metal roller 21 via the rubber roller 38, the chrome-plated metal roller 37, and the rubber roller 35. The supply speed of the dampening water is controlled by adjusting the slip state between the rubber roller 35 and the chrome-plated metal roller 37. Along with this, the water content of the printing ink on the copper-plated metal roller 21 changes.

On the other hand, a corona charger 25 and a surface potential measuring head 27 are sequentially arranged around the copper-plated metal roller 21 in the circumferential direction. And corona charger 2
5 is a high voltage power supply 26 and a function generator 31
Connected to. Also, the surface potential measuring head 27
Is connected to the surface potential measuring device main body 28 and the recorder 32.

The high voltage power source 26 includes a MODEL 610.
C (manufactured by TREX), function generator 31
WIDE-BAND FUNCTION GENERATION
RATOR MODEL FG-143 (manufactured by NF Circuit Design Block Co., Ltd.)
ODEL344 (made by TREX), recorder 32,
Fast response MODEL2931 PHOTOCORDE
R (made by Yokogawa Electric Co., Ltd.) was used.

For the blue printing ink, HYPLUS
MZ (BLUE) (manufactured by Toyo Ink Co., Ltd.) and NEWVS ink (manufactured by Godo Ink Co., Ltd.) were used as the black printing ink. The distances between the copper-plated metal roller 21, the corona charger 25, and the surface potential measuring head 27 are all set to 3 mm, and the copper-plated metal roller 21 is at ground potential. The peripheral speed of the copper-plated metal roller 21 etc. is 3 m /
set to s.

Three types of corona charging methods were investigated: (1) DC corona charging, (2) low frequency AC corona charging, and (3) pulse corona charging. (1) The DC corona charging method uses a blue printing ink when the printing ink film is 5 μm and no dampening water is added.
There is a charging potential of about 0 V and about 35 V for black printing ink, and the charging potential gradually decreases as the water content increases,
With a water content of about 12%, both inks drop to a charging potential of around 10V. Therefore, it can be sufficiently applied to the identification of the water content, but there arises a problem that the charging potential increases and the film thickness also changes with the passage of time. However, if the AC corona discharger is set on the downstream side of the surface potential measuring head 27 and the charge is removed every time, this problem will be solved.

(2) The low-frequency AC corona charging is for solving the above-mentioned problems of time-dependent changes in charging potential and film thickness. In the experiment, the corona charger 25 was set to +7.5 for 2 seconds.
KV, 0.25H _Z to apply the next two seconds -7.5KV
AC corona charging was performed. As a result, the time variation of the charging potential and the film thickness was suppressed to be low. Moreover, in order to correlate the value of the difference in charging current between positive charging and negative charging with the water content,
The effect of the zero-point shift of the surface potential measuring devices 27 and 28 is offset, and the accuracy of water content identification is also improved.

(3) The pulse corona charging method is for further minimizing the film thickness change due to charging as compared with the low frequency corona charging method. In the DC corona charging method and the low frequency AC corona charging described above, the copper-plated metal roller 21 rotates many times during one charging. The charging potential of the printing ink decreases exponentially as a charging wave, but the charging potential is not sufficiently attenuated in a short period of one rotation of the copper-plated metal roller 21, so that the charging potential is accumulated during many rotations. Go on. Since this residual potential component does not depend so much on the water content, when this value becomes large, the charging potential width that changes depending on the water content becomes small and the measurement accuracy deteriorates.

The pulse corona charging method solves this problem, and the change in film thickness due to charging is further reduced as compared with the above-mentioned low frequency corona charging method. When the copper-plated metal roller 21 (φ200 mm) rotates once for 0.21 seconds, the charging potential is reduced to about 0 V in about 0.6 seconds. So + 7.5KV, corona charging for 0.21 seconds,
Then, the experiment was conducted by pulse charging of 1.19H _Z with one cycle of charging rest of 0.63 seconds thereafter. Since a slight variation in the film thickness is unavoidable, the film thickness and water content of the indigo printing ink standardized by the printing ink film thickness measured by a separate means were measured by the infrared absorption method. The film thickness of the black printing ink was measured by the photoacoustic method shown in FIG. 5, and the water content was measured by the Karl Fischer method.

In this way, the relationship between the charging potential per 1 mm and the water content was examined for the indigo printing ink and the black printing ink in FIGS. 3 and 4, and the relationship between the charging potential and the water content was obtained. It can be seen that a strong correlation is obtained. The principle of the above-described photoacoustic film thickness meter is shown in FIG. Irradiate the sample with light pulsed by the chopper, at that time,
An acoustic wave generated by heat generation in a sample is captured by a microphone, and the film thickness is identified from the sound pressure proportional to the film thickness.

In the apparatus for measuring the water content of printing ink shown in FIG. 1, the corona charger 25 and the surface potential measuring devices 27 and 28, which were subjected to an experiment for verifying the effectiveness of the pulse corona charging method, were set according to the positional relationship. . With respect to the indigo printing ink and the black printing ink, the film thickness and the water content were measured by the existing measurement method, and the results of examining the relationship between the charging potential and the water content are shown by the circles in FIGS. 3 and 4. Indicated. It can be seen that the calibration graph created by the ink transfer test device shown in FIG. 2 can be applied with high accuracy even in the printing ink water content measuring device shown in FIG.

In the pulse corona charging method,
By changing the polarity of pulse charging alternately between positive and negative, it is possible to further reduce the change in film thickness due to charging. If film thickness fluctuation can be ignored in steady operation, it is not necessary to intentionally install a film thickness meter.

[0026]

According to the apparatus for measuring the water content of printing ink of the present invention, since the charging potential directly correlating with the electric resistance which remarkably changes depending on the water content is measured, the ink for printing black ink which has hitherto been relied upon manually. It is possible to automatically measure and control the water content. Since it is non-contact and compact, it can be easily installed on any printing machine.

Further, since the surface potential measuring device is resistant to gap fluctuation and vibration, the reliability of the device can be improved.

[Brief description of drawings]

FIG. 1 is a system diagram showing an embodiment of a water content measuring apparatus for printing ink according to the present invention.

FIG. 2 is a system diagram showing an ink transfer test device for verifying the principle of the water content measuring device for the printing ink.

FIG. 3 is a calibration graph of electrostatic potential and water content of indigo printing ink.

FIG. 4 is a calibration graph of charging potential and water content of black printing ink.

FIG. 5 is an explanatory view showing the principle of a film thickness meter by a photoacoustic method.

FIG. 6 is a system diagram showing a conventional moisture content sensor.

[Explanation of symbols]

 21 Conductor Roller (Copper Plated Metal Roller) 22 Printing Ink Film 23 Wearing Roller 24 Plate Cylinder 25 Corona Charger 26 High Voltage Power Supply 27 Surface Potential Meter Head 28 Surface Potential Meter Main Body 29 Ink Film Thickness Meter 30 Computing Unit

Claims (2)

[Claims] 1. A printing ink, wherein a corona charger is provided near the surface of a conductor roller in an ink roller group of a printing machine, and a surface potential measuring device is provided downstream of the corona charger. Water content measuring device. 2. An ink film thickness measuring device arranged near the surface of the conductor roller, and a calculation for calculating the water content in the ink based on the measured values from the ink film thickness measuring device and the surface potential measuring device. The water content measuring device for printing ink according to claim 1, further comprising a container.