JPH0825269B2 - Printing method - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an improvement in a printing method when printing is performed by an offset printing machine such as a sheet-fed printing machine or a rotary printing machine.

(Prior Art) When printing is performed by an offset printing machine, a ghost phenomenon occurs depending on the type of printed matter, which causes a problem of degrading the quality of the printed matter.

As shown in FIG. 1, the ghost phenomenon occurs when there is a step difference in the ratio of the image area that is sharp in the width direction of the printing machine (hereinafter referred to as “image rate”) (the arrow in FIG. 1 indicates the printing direction). ,
That is, it is a phenomenon that occurs when a pattern having a sharp step of ink consumption on the paper surface in the width direction of the printing machine is printed.

In the printing machine as shown in FIG. 3, the gap between the ink key 18 and the ink source roller 19 is changed, and the ink supply amount is adjusted according to the image ratio in the width direction and the size of the printing density to make the ink constant in the width direction. The print density is adjusted so that

However, in a general printing machine, such adjustment in the width direction of the gap between the ink key 18 and the ink source roller 19 can be done only at a pitch width of 30 to 40 mm in the width direction at a minimum although it depends on the printing machine. In the present situation, such an adjustment cannot deal with the case where there is a sharp step difference in the drawing rate as shown in FIG. This is because it is necessary to adjust the above-mentioned gap in the width direction with a width narrower than the pitch width of 30 to 40 mm in order to cope with the sharp step difference of the image rate as described above. This is because the machine cannot do this, and the above-described adjustment with a large pitch does not give a necessary change in the ink amount between the left and right of the step of the image rate.

For this reason, conventionally, even when there is a steep step of the image coverage as shown in FIG. 1, the ink supply amount on the left and right of the step is constant. Then, as shown in FIG. 2, the film thickness was larger in the portion B having a smaller image coverage than in the portion A having a large image coverage. As a result, the print density of the B section becomes higher than the print density of the A section, and a density difference occurs in a portion where the density difference should not originally occur. This is called the ghost phenomenon.

Such a phenomenon is basically caused by the difference in the image rate of the plate pattern of the printing press, and the transfer state of the ink and the dampening water at the ink-forming roller and the ink reciprocating roller near the plate is It was said to be closely related to the ghost phenomenon. In fact, it was empirically known that the extent of occurrence of this ghost phenomenon, that is, the magnitude of the difference in density on the printed matter on the left and right of the step is affected by the ink supply amount and the dampening water supply amount.

However, until now, in order to reduce this ghost phenomenon, it is necessary for an experienced printing operator to adjust the ink supply amount and the dampening water supply amount each time while looking at the printed matter.
It required great care and enormous effort.

This will be described below with reference to the roller arrangement in the offset sheet-fed printing press shown in FIG.

First, the dampening water 6 in the dampening water tank 7 uses isopropyl alcohol having a normal concentration of about 10%, and is supplied to the plate 5 through the water source roller 8, the chrome roller 9, and the swimsuit roller 10.

The control of the amount of the dampening water 6 is mainly controlled by the rotation speed of the chrome roller 9, and the driver adjusts the rotation speed by the light condition of the water on the printed matter and the plate surface.

On the other hand, the ink 17 in the upper part of the drawing is the ink source roller 19, the ink feeding roller 20, the ink reciprocating roller 16, the ink kneading roller 22, the ink reciprocating rollers 14, 15, the ink depositing roller 13,
It is supplied to plate 5 through 13, ...

To control the ink amount, the driver controls the gap between the ink key 18 and the ink source roller 19 and the calling speed of the ink calling roller 20 according to the print density and the image coverage.

Recently, an auto-preset system that controls the ink amount by automatically adjusting the gap between the ink key 18 and the ink source roller 19 in advance according to the image width ratio in the roller width direction has been put into practical use. Is progressing. However, as described above, the adjustment pitch in the width direction is at a minimum of 30 to 40 mm, and the ghost phenomenon cannot be eliminated.

On the other hand, the dampening water supply amount has not yet been quantified because it slightly changes depending on the nip between the water source roller 8 and the chrome roller 9, the temperature, the isopropyl alcohol concentration, and the like.

Therefore, the conventional printing method has a drawback in that the adjustment is time-consuming and a large amount of paper is left behind due to the work relying only on experience and intuition. Note that 21
Is a rider roll and 11 is a transfer roller.

(Problems to Solve the Invention) The present invention quantitatively controls this as a numerical value without relying on experience or intuition in order to reduce the ghost phenomenon, and even those who have insufficient experience can always obtain good quality. An object of the present invention is to provide a printing method that enables printed matter to be printed easily.

(Means for Solving Problems) The invention of the present application uses a roller whose surface is copper-plated as an ink reciprocating roller that comes into contact with an inking roller that supplies ink to a printing plate, and determines an ink water content on the ink reciprocating roller. It is characterized in that it is measured by a measuring means utilizing infrared absorption characteristics, and the amount of dampening water is controlled based on this measurement location to set the ink water content on the ink reciprocating roller to 5 to 10% by weight. The present invention will be further described below based on the embodiment shown in FIG.

FIG. 4 shows an example of a roller arrangement of a printing machine for carrying out the present invention, which is almost the same as that shown in FIG.
The only difference is that the ink water content meter 12 is mounted on the ink reciprocating rollers 14 or 15, respectively. Therefore, the other members are the same as those in FIG. 3, and the same reference numerals are used for the same members.

In FIG. 4, the dampening water supplied to the plate 5 through the swimsuit roller 10 is at the roller nip between the inking roller 13 and the plate 5,
The ink is mixed with the ink supplied to the plate 5 via the inking rollers 13, 13. Then, a part of it goes up to the ink roller group in a state of being mixed with the ink. Therefore, on the ink roller near the plate 5, the ink is in a state of being mixed with dampening water.

Here, the inventor considered that the ghost phenomenon is dominated by the ink transfer state at the ink forming rollers 13, 13 ... and the ink reciprocating rollers 14, 15 near the plate 5. The ink transfer state here is a state that changes depending on the supply amounts of ink and dampening water. From these facts, the mixing state of the ink and the dampening water on the surface of the ink forming rollers 13, 13 ... Or the ink reciprocating rollers 14,15, in other words, the quantitative balance between the ink and the dampening water is determined by the ink forming rollers 13,13. ..., which paid close attention to the fact that it influences the ink transfer state at the ink reciprocating rollers 14 and 15, and this governs the ghost phenomenon.

As a result, the inventor of the present application paid attention to the ink water content as a measurement value of the quantitative balance between the ink and the dampening water, and repeatedly conducted an experiment on this, and found that the ink water content on the ink reciprocating roller was 5 to 10% by weight. It has been found that the ghost phenomenon of printed matter can be avoided by doing so. The water content of the ink here needs to be the above-mentioned water content as a value measured on the ink reciprocating roller.

When the water content of the ink is less than 5% by weight or exceeds 10% by weight, the ghost phenomenon becomes remarkable, which is not preferable. Further, it was also confirmed by experiments that the range of the water content of the ink is substantially the same even when various dampening waters are used.

For the roller for measuring the water content of the ink, it is preferable to use an ink water content meter 12 that utilizes infrared absorption characteristics in order to perform accurate measurement. Further, the surface of the measuring roller needs to have high infrared reflection, and needs to be a metal surface such as a copper-plated surface. For this reason, the inking rollers 13, 13 ... Which are rubber rollers cannot be used as measurement rollers,
One of the reciprocating rollers 14 and 15 which is a metal roller is the roller to be measured.

The reciprocating roller contacting the inking rollers 13, 13 ... Is made of a material other than metal such as nylon roller as shown in FIG.
In the case of 14 ', the ink water content can be measured on the copper-plated roller surface by providing a measuring rubber roller 23 and a copper-plated measuring roller 24 between the ink water content meter 12 and the like. It is necessary to If the reciprocating roller is a rubber roller 14 ″, the ink moisture content meter 12
It is necessary to provide a measuring roller 24 whose surface is plated with copper between and.

Further, for measuring the water content of the ink, an ink water content meter utilizing the infrared absorption characteristics exemplified in Japanese Patent Application No. 58-124418 (Japanese Patent Application Laid-Open No. 60-17304) is preferably used with good accuracy. The surface of the measuring roller needs to have high infrared reflection, and needs to be a metal surface such as a copper-plated surface.

Therefore, the inking rollers 13, 13 ... Which are rubber rollers
Is not suitable as a measuring roller, and any one of the ink reciprocating rollers 14 and 15 which is a metal roller is used as a measuring object roller. An outline of the ink water content meter of Japanese Patent Application No. 58-124418 (Japanese Patent Application Laid-Open No. 60-17304) is shown in FIG.

In the device shown in FIG. 8, the infrared light emitted from the infrared light emitter 25 is focused on the infrared light conduit 31 by the infrared transmission lens 26. During this time, the infrared interference filter is placed on the chopper wheel 27.
Filters that are equipped with 28, 29 and 30 to transmit water absorption wavelength band
28, a filter 29 for transmitting the absorption wavelength band of the ink, and a filter 30 for transmitting the reference wavelength band outside these two absorption wavelength bands are alternately placed in the optical path to sequentially transmit the light of each wavelength band.

These infrared rays are guided by the infrared light guide tube 31 to the surface of the roller 32 having a copper-plated surface and high infrared reflection on the surface and the ink / water mixed liquid film 33 adhered to the roller surface and projected. To do. Infrared absorption and reflection occur on the surfaces of the mixed liquid film 33 and the roller 32, and the reflected light is condensed by the infrared transmission lens 34 and guided to the infrared detection element 35. In the infrared detection element 35, its resistance changes depending on the intensity of the reflected infrared light, and the amplifier 36 voltage-amplifies and converts it. This analog signal
VSG.

On the other hand, a synchronizing device for synchronizing a pulse signal including a pulse detector 38 for detecting the rotational positions of the infrared interference filters 28, 29, 30 provided on the chopper wheel 27 and a pulse detector 37 for detecting the measurement position of the roller 32. There are 39. The output signal of the synchronizer 39 is a trigger pulse Tr, and the peak of each of the analog pulse signal VSG, the signal W in the water absorption wavelength band, the signal I in the ink absorption wavelength band, and the signal S in the reference wavelength band. (See FIG. 9), the A / D converter 40 receives the signal of the toga pulse Tr and receives each of the W, I, and S of the analog signal VSG.
The captured signal is sent to the signal calculator 41. In the signal calculator 41,
The signals W, I, and S are mutually proportionally corrected to calculate the ink film thickness of the emulsified ink film and its water content, and the display 42
Is displayed.

(Example) As shown in FIG. 4, an ink water content meter 12 was set so that the ink water content on the ink reciprocating roller 14 or 15 of the printing machine could be measured using the PS plate having the pattern shown in FIG. Next, the amount of ink supplied was set according to the image rate by an auto preset system, and the rotary dial scale of the chrome roller 9 was changed as shown in Table 1 for printing.

In addition, 10% isopropyl alcohol was used as the dampening water, and TK Bright (trade name) sepia color manufactured by Toyo Ink Co., Ltd. was used as the ink, and the mixing ratio was 67.5% yellow and 7.5% black. % And gold red 25%. In this case, the relationship between ink water content and ghost was measured and the result was
Shown in the table. The ghost is defined as follows by the density difference ratio at each position shown in FIG.

Ghost (%) = (density at position B-density at position A) / density at position B x 100 Table 1 also shows a comparative example. The result of the present invention is the seventh.
It is shown diagrammatically in the figure.

As is clear from the above table and FIG. 7, the ghost phenomenon can be significantly reduced by the method of the present invention. The shaded portion in FIG. 7 is a portion where almost no ghost phenomenon is visually perceived. As described above, the ghost phenomenon could be reduced by setting the water content of the ink on the reciprocating roller to 5 to 10% by weight.

(Effects) As described above, according to the method of the present invention, the ink water content on the reciprocating roller is measured, and printing is performed by controlling the water content so as to minimize the ghost phenomenon. It is extremely useful in the industry because printing can be performed with minimal wasted paper without relying on

[Brief description of drawings]

FIG. 1 is a front view of a PS plate having a design, FIG. 2 is a front view showing a printed state of a printed matter by a conventional printing method, and FIG. 3 is an explanatory view showing an arrangement of rollers showing a conventional printing method. FIG. 5 is an explanatory view showing the arrangement of a roller and an ink water content meter showing an example of the printing method of the present invention, and FIGS. 5 and 6 show the positional relationship between the ink reciprocating roller and the ink water content meter in the printing method of the present invention. FIG. FIG. 7 is a diagram showing the relationship between the water content of ink and the ghost phenomenon, FIG. 8 is a schematic view showing the configuration of a conventionally known ink water content meter suitably used in the present invention, and FIG. 8 of trigger pulse Tr and analog signal VSG of Figure 8
It is explanatory drawing of the relationship with S. 1 ... Non-image area, 2 ... Image area, 3 ... Non-print area, 4 ...
... solid printing section, 5 ... plate, 6 ... dampening water, 8 ... swimwear roller, 9 ... chrome roller, 10 ... swimwear roller, 11 ...
I roller, 12 …… ink water content meter, 14,15,16 …… ink reciprocating roller, 14 'nylon ink reciprocating roller, 1
4 ″ …… Rubber ink reciprocating roller, 17 …… Ink, 18…
Ink key, 19 Ink source roller, 20 Ink feeding roller, 21 Ink roller, 22 Ink mixing roller, 23 Measuring rubber roller, 24 Measuring copper roller, 25 Infrared Light emitter, 26 ... Infrared transmission lens, 27
...... Chopper wheel, 28,29,30 …… Infrared interference filter, 31 …… Infrared light conduit, 32 …… Measurement target roller, 33 ……
Ink and water mixed liquid film, 34 …… infrared transmission lens, 35 ……
Infrared detector, 36 ... Amplifier, 37 ... Pulse detector, 38
...... Pulse detector, 39 …… Synchronizer, 40 …… A / D converter, 41 …… Signal calculator, 42 …… Display.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Seishiro Hamada 4-6-22 Kannon Shinmachi, Nishi-ku, Hiroshima City, Hiroshima Prefecture Mitsubishi Heavy Industries, Ltd. Hiroshima Research Laboratory (56) Reference JP-A-56-2170 (JP, A) ) JP-A-54-159296 (JP, A) JP-A-59-22757 (JP, A)

Claims (1)

[Claims] 1. A roller having a surface plated with copper is used as an ink reciprocating roller in contact with an inking roller for supplying ink to a printing plate, and the ink water content on the ink reciprocating roller is measured by utilizing infrared absorption characteristics. A printing method characterized in that the water content of the ink on the ink reciprocating roller is adjusted to 5 to 10% by weight by controlling the amount of dampening water based on the measured value.