JP2001113668A - Controller for dampening water supply amount, offset printer having the controller, and method for controlling dampening water supply amount - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a controller for a dampening water supply amount and a method for controlling the amount to contribute to a reduction in a production cost of printing and particularly adapted to an automatic control by decreasing a spoilage for causing a decrease in a water content while maintaining good color tone quality on a printed product and a printer having them. SOLUTION: The controller for a dampening water supply amount and a method for controlling the amount regulate a rotating amount of a water fountain roller so that a lowest water content falls within a predetermined range between an upper limit and a lower limit from distribution data of the content of a mixture layer of an ink and a dampening water on a metal roller of inking rollers. The offset printer has the controller and the method.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an offset printing press,
In particular, the present invention relates to a control device for a supply amount of dampening water in a rotary press, an offset printing press having the same, and a control method therefor.

[0002]

2. Description of the Related Art In an offset printing press, it is necessary to maintain an optimum supply amount of not only ink but also dampening solution. When the dampening solution supply amount changes, the inlaid shape of the halftone dot changes, and it becomes impossible to maintain the reference color tone of the printed matter only by adjusting the ink supply amount.

In general, when the amount of dampening water supplied is small, the amount of ink that can be applied to the halftone dots of the plate increases, the print reproduction color gamut increases, and the ink deposition shape becomes stable. The color tone is stable and the paper does not absorb extra water, so the register is good and it is considered good. However, when the amount of the dampening solution is below the threshold value, printing troubles such as background stains and stains caused by remaining blanks occur. Therefore, the best supply of dampening water is considered to be the best in terms of quality immediately before a printing failure occurs due to shortage of dampening water.

However, it takes a long experience to determine whether or not the dampening water supply is on the verge of causing a printing failure due to a shortage of dampening water. For this reason, inexperienced printing press operators fear printing trouble due to insufficient supply of dampening solution, and perform excessive supply of dampening solution, resulting in a narrow print reproduction color gamut and unstable color tone.
When a misregistered printed matter is produced and the dampening water amount exceeds the threshold value, a printing trouble such as a water mark is caused to cause an increase in scuffing.

[0005] Aiming at quality stability and reduction of scrap, for example,
As disclosed in Japanese Patent Publication No. 7-98396, as one method of controlling the supply amount of dampening solution, a mixture of ink and dampening solution present on the metal rollers in the inking roller group is used by using infrared rays. The ink film thickness and the water film thickness are measured from the above layers, and the water content value is calculated from these two values, and the water content value with the water content as the quality target (hereinafter referred to as the quality target water content value) is calculated. At the center, there is a type in which the supply amount of dampening water is controlled by adjusting the rotation amount of the water supply roller so that the deviation therefrom becomes as small as possible.

However, the variation in the water content value from the quality target water content value always varies depending on the pattern of the printed matter, paper, etc., various settings of the printing press, the printing environment, and the like. It is extremely difficult. Therefore,
Although the water content value as the quality target is very close to the water content value which is a threshold value at which a printing failure (printing failure) due to a shortage of dampening water supply occurs, it is actually controlled by the control to be tried. The achieved moisture content value is difficult to foresee and it can be hopelessly below the threshold value. In the prior art, it is a method of minimizing the deviation from the quality target moisture content value,
For this reason, there has been a concern that a failure may occur every time the actual moisture content value falls below the threshold at which a printing failure occurs due to insufficient dampening solution supply.

[0007]

DISCLOSURE OF THE INVENTION The present invention has been made in view of the above-mentioned problems of the prior art, and is based on the fact that the color tone of a printed product is maintained at a good level and the water content is excessively reduced. Technology that controls the supply of dampening water that can reduce the occurrence of scouring, and is particularly suitable for automatic control, and that is intended to contribute to reducing production costs associated with printing. Another object of the present invention is to provide a control device, a control method, and a printing press having the control device, which can achieve the control. In this case, the term “scratch” generally means a defective print. In this case, in particular, it refers to a background stain, a stain caused by a blank residue, or a misregistration.

[0008]

According to a first aspect of the present invention, a mixture of ink and dampening solution present on a metal roller in an inking roller group of an offset printing press is provided. Input means for inputting data indicating the moisture content distribution in which the moisture content of the layer is distributed along the width direction of the metal roller, the moisture content distribution within a certain range between the set upper and lower limits. Determination means for determining whether or not a minimum water content in the data of the above exists; and, if the minimum water content does not exist within the certain range, the water level is adjusted so that the minimum water content falls within a certain range. A damping-water supply amount control device, comprising: a water-source-roller adjusting means for adjusting a rotation amount of a roller;

According to a second aspect of the present invention, there is provided an offset printing press including the dampening solution supply control device according to the first aspect.

According to the third aspect of the present invention, a measurement is performed to obtain data on the water content of a layer of a mixture of ink and dampening solution present on a metal roller in the inking roller group of the offset printing machine, A method for controlling the supply amount of dampening water based on the measurement result, wherein the lowest water content among the water contents distributed along the width direction of the metal roller is the set upper limit and lower limit. A dampening water supply amount is controlled by adjusting a rotation amount of a water source roller so that the minimum water content falls within the predetermined range. This is a method for controlling the supply amount.

According to a fourth aspect of the present invention, when data of the water content of the layer of the mixture of the ink and the fountain solution is obtained, the layer of the mixture of the ink and the fountain solution is irradiated with infrared rays. 4. The method according to claim 3, wherein measurement using reflected light is used.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION When calibrating with this machine,
The lowest one of the water content values distributed along the width direction on the metal rollers in the inking roller group of the printing press is set as the quality target water content value used for the quality target.

2. The value obtained by adding a small increment appropriately set as a safety margin to the quality target moisture content value is the lower limit of the guideline for controlling the moisture content value, and the width of the variation range of the moisture content that does not affect the color tone is also appropriately set. Then, a value obtained by adding a small value to the quality target moisture content value is set as an upper limit of a guide for controlling the moisture content value, and a lower limit (%) and an upper limit (%) are set.
Here, [lower limit] <[upper limit]. The safety margin and the width may be appropriately set according to the situation (including the measurement accuracy). However, under the constraint of [lower limit] <[upper limit], each is at most a number (%) or less. Of the degree.

3. The dampening water supply is controlled under the following conditions so that the minimum moisture content value on the metal roller is within the range.

(A) If the minimum water content falls below the lower limit, increase the number of rotations of the water supply roller. (B) If the minimum water content value exceeds the upper limit, reduce the number of rotations of the water supply roller. (C) If the minimum water content value is within the range between the lower limit and the upper limit, the rotation speed of the water source roller is not changed (including the lower and upper limits).

The water content (%) in the present invention is defined as 100 × [fountain solution] / [ink and fountain solution (entire mixture)] (%). Then, the characteristics of the ink or dampening solution to be substituted into this definition formula may be appropriately selected and used as long as they can be measured, as long as the characteristics are related to the amount of ink or dampening solution present at the place. . For example, for each of the ink and the fountain solution, not only the mass or the weight but also the absorption amount for infrared rays, the thickness of the film, and the like may be used. When appropriately setting the lower limit and the upper limit used for the control, characteristics substituted into the definition of the water content (%) may be considered.

[0017]

EXAMPLES <Examples> When the operator calibrated the printer, the lowest one of the water content values distributed on the metal rollers in the inking roller group of the printing press was used as the quality target water content value used for the quality target. When the water content was determined, each absorption characteristic of the ink and the fountain solution with respect to infrared rays was used.

2. The lower limit is the value obtained by adding 1% as a safety margin to the quality target moisture content value, and the width of the moisture content range that does not affect the color tone is 2%. [Quality target moisture content value + 1%]
To [quality target moisture content + 3%].

The dampening water supply was controlled under the following conditions so that the minimum water content value on the metal roller was within this range.

(A) The minimum moisture content value is equal to the quality target moisture content value +
If it is less than 1%, increase the rotation speed of the water supply roller. (B) If the minimum water content value is greater than the quality target water content value + 3%, reduce the rotation speed of the water supply roller. (C) When the minimum water content value is equal to or higher than the target quality water content value + 1% and equal to or lower than the target quality water content value + 3%, the rotation speed of the water supply roller is not changed.

<Comparative Example> In order to compare with the conventional control method, the minimum water content value on the metal roller was damped so that the deviation from the quality target water content value as a center value was minimized. The water supply was controlled. Other than that is the same as the embodiment.

The rate of occurrence of scouring and the maximum variation in color tone caused by improper supply of dampening solution were compared between the case of the control according to the present invention and the case of the conventional control. The results are as shown in Table 1. In addition, the definition of the occurrence rate (%) in the table is as follows. 100 × [number of scraps] / [total number of prints (= number of good prints + number of scraps)] (%) In the table, ΔE indicates a color difference, and points A, B, and C indicate patterns of printed matter. Shows the locations selected from among the following. Point A: Part of human skin [skin color] Point B: Part of clothes [gray] Point C: Leather part of bag (handbag) [brown]

[0023]

[Table 1]

[0024]

According to the present invention, by using the above-described control technique, it is possible to reduce the occurrence of scouring caused by excessively low water content while maintaining good color tone of printed matter. A control device and a control method that can control the supply amount of dampening solution as much as possible, which is a technology suitable for automatic control and can contribute to reduction of production costs related to printing, and a printing machine equipped with the same Could be provided.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating an outline of a dampening water supply amount control device according to the present invention.

[Explanation of symbols]

 1 ... Control device for dampening water supply

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Takeshi Ono 1-5-1, Taito, Taito-ku, Tokyo Toppan Printing Co., Ltd. F-term (reference) 2C034 BB23 2C250 DC05 EB20 2G059 AA05 BB08 BB15 CC09 EE01 EE02 FF06 GG10 HH01 KK01 MM05

Claims (4)

[Claims] 1. A water content distribution wherein the water content of a layer of a mixture of ink and dampening solution present on a metal roller in an inking roller group of an offset printing press is distributed along the width direction of the metal roller. Input means for inputting data indicating, within a certain range between the set upper limit and lower limit, determining means for determining whether or not the lowest water content in the data of the water content distribution exists, and When the minimum moisture content does not exist within the certain range,
A dampening water supply amount control device, comprising: a water roller adjusting means for adjusting the rotation amount of the water roller so that the minimum water content falls within a predetermined range. 2. An offset printing press comprising the dampening water supply control device according to claim 1. 3. Measurement is performed to obtain data on the water content of a layer of a mixture of ink and fountain solution present on a metal roller in an inking roller group of an offset printing press, and dampening is performed based on the measurement result. A method for controlling a water supply amount, wherein a minimum water content among water contents distributed along a width direction of the metal roller does not exist within a certain range between a set upper limit and a lower limit. In this case, a dampening water supply amount is controlled by adjusting a water supply roller rotation amount such that the minimum water content falls within the predetermined range. 4. A method for irradiating a layer of a mixture of an ink and a dampening solution with infrared rays to obtain data on the water content of the layer of the mixture of the ink and the dampening solution and measuring the reflected light. The method according to claim 3, wherein the dampening solution is supplied.