JPH0446927Y2 - - Google Patents

Description

[Detailed description of the invention] [Industrial application field] This invention is designed to determine the pattern area ratio of each ink zone corresponding to each ink key of an offset printing plate in order to preset the ink supply amount for each ink key of an offset printing machine. The present invention relates to a picture area ratio measuring device for measuring picture area ratios, and particularly relates to correction of measured area ratios for printing plates with extremely few pictures, such as encyclopedias, books, and maps.

[Conventional technology]

Recently, in offset printing, an ``ink preset system'' has been widely introduced, which adjusts the amount of ink according to the pattern before printing to reduce paper waste at the beginning of printing. This is done by measuring the image area ratio on the printing plate in advance for each ink zone corresponding to the ink keys of the printing press, and then, based on the measured image area ratio, opening the keys of the ink keys of the ink fountain of the printing press. The amount of ink is determined before printing, and the amount of ink is adjusted according to the pattern before printing. This system has already been put into practical use for some time and is becoming established as a general printing technology.

However, the state of advance adjustment of the ink amount is not perfect, and in reality, it is essential to make fine adjustments manually at the start of printing. This can be caused by various factors such as the emulsification balance of ink and water, the transfer of ink to paper, and the measurement accuracy of the pattern area ratio.The opening degree of the ink key is determined macroscopically from the total pattern area ratio of the ink zone. It can be said that it is impossible to completely perform ink presetting just by doing so.

For this reason, as seen in Japanese Patent Application Laid-Open No. 59-5910, ``A device for measuring the picture area ratio of offset printing plates,'' it Some attempts have been made to correct the image area ratio of printing plates by taking into account trends in ink consumption.

[Problem that the invention attempts to solve]

However, this correction could not avoid the inconvenience caused by the vibration effect of the ink roller.
Generally, the inking mechanism of a printing press consists of a combination of multiple metal rollers and rubber rollers, and ink is supplied from an ink source roller with an ink key to the plate surface of the plate cylinder via multiple rolling rollers and an ink form roller. Therefore, the opening degree of each ink key does not correspond one-to-one to the pattern area ratio of each ink zone. Even if ink is applied to the ink source roller in a stepwise manner, the thickness of the ink film becomes sinusoidal as it passes through the rolling rollers.
That is, ink in each ink zone tends to escape to the adjacent ink zone unless the opening degree of the ink key in the adjacent ink zone is sufficient. Therefore, the amount of ink in each ink zone tends to be insufficient, and the effect of ink presetting is not sufficient.

This idea was made in order to deal with the above-mentioned situation, and when presetting the key opening of the ink key of the ink fountain of the printing machine before printing, based on the pattern area ratio measured in advance, the ink It is an object of the present invention to provide a picture area ratio measuring device capable of avoiding the tendency for the amount of ink in each ink zone to be insufficient due to the vibration effect of a roller.

[Means for solving problems]

According to the picture area ratio measuring device invented by this invention,
When calculating the pattern area ratio for each ink zone by aggregating the pattern area ratio for each measurement point for each ink zone,
The image area ratio of each ink zone is corrected based on the image area ratio of the left and right zones of the ink zone, taking into account the vibration of the ink roller.

[Effect]

According to the picture area ratio measuring device invented by this invention,
Since the minimum value of the area ratio for each ink zone is guaranteed, sufficient ink can be supplied to the pattern area, making it possible to print high quality images and producing the effect of ink presetting.

〔Example〕

An embodiment of the picture area ratio measuring device according to this invention will be described below with reference to the drawings.

FIG. 1 is a schematic diagram of a picture area ratio measuring device according to this embodiment. Here, a laser scan method will be explained as an example of a method for measuring the picture area ratio, but the present invention can be applied to a television camera method, a sensor scan method, etc. without any problem.

In FIG. 1, in order to measure the pattern area ratio on the printing plate 1 for each ink zone 2 corresponding to the ink key, a laser beam from a laser light source 3 is scanned over the printing plate 1 in the X direction and the Y direction by a scanner 4. be done. Beam spot 5 irradiated onto printing plate 1
The reflected light is converted into an electrical signal proportional to the amount of reflected light by the photoelectric conversion element 6, converted into a digital signal by the A/D converter 7, and input to the CPU 8.

Control of the scanner 4 and sampling control of the A/D converter 7 are controlled by the CPU 8.

A calibration mark 9 indicating 0% white (no halftone dots) and 100% black (solid) is printed outside the picture area of the printing plate 1. CPU8 is 0% white (no halftone dot) in advance when measuring the pattern area ratio.
The 100% black (solid) area is measured, and the partial picture area ratio data of the beam spot 5 is obtained from the ratio of the levels of the white level signal, the black level signal, and the output electric signal of the photoelectric conversion element 6. Calculate.
The CPU 8 totals this for each ink zone 2, and
Calculate the required pattern area ratio for each ink zone. The obtained pattern area ratio is set in the printing press, the opening degree of the ink key of the ink fountain of the printing press is determined, and the amount of ink is adjusted in advance.

Here, since the color of the printing plate 1 is green or blue, the laser light source 3 is He-Ne, which has good absorption properties.
A laser is often used, a galvano mirror or a polygon mirror is often used as the scanner 4, and a photomultiplier is often used as the photoelectric conversion element 6 because the amount of reflected light is small.

By the way, even if you calculate the pattern area ratio for each ink zone by simply adding the pattern area ratios for each beam spot 5, the ink preset effect will not be effective for printed materials with extremely few images, such as encyclopedias. There are many things. This is because the measurement accuracy of the pattern area ratio measuring device is the highlight part of the pattern (the pattern area ratio is 5%).
(below) is affected by the grain of the plate material and non-uniformity of the rubber material coated on the surface of the plate material to prevent oxidation, and the ink becomes extremely poor. The cause is thought to be that it is difficult to maintain an emulsification balance with water. In addition, in printed matter with extremely few patterns, there is a large difference in pattern area ratio between the black plate and other color plates even in the same ink zone.
It is difficult to preset an accurate amount of ink depending on the area ratio measured using the same method.

Therefore, in this embodiment, as shown in FIG. 2, correction is performed when the pattern area ratio measured for each beam spot is totaled as the pattern area ratio for each ink zone.

The operation of this embodiment will be explained according to the flowchart shown in FIG.

First, the presence or absence of correction is determined (S1). This can be done by an operator using an operation panel or the like. If there is no need for correction, normal measurement (the area ratio data of beam spots is totaled for each ink zone to determine the pattern area ratio of each ink zone) is performed.

If correction is necessary, it is determined whether the printing plate to be measured is a black plate (S2). In general, encyclopedias have very few pictures and other pictures, and most of the text is made up of fine black ink. Therefore, the black version and other colored versions (indigo, red,
It is necessary to distinguish between the two (yellow) and correct them.

Correction for the black version will be explained. At the start of the measurement, the printing plate 1 is scanned with a laser beam from the laser light source 3, and the pattern area ratio of each beam spot is measured (S3a). The pattern area ratio for each beam spot is totaled to calculate the pattern area ratio for each ink zone (S4).

The pattern area ratio calculated for each ink zone is 10%
Determine whether the following is true (S3). If it is not 10% or less, the pattern area ratio is set as the corrected pattern area ratio of the ink zone (S6), and if it is 10% or less, the corrected pattern area ratio of the ink zone is forcibly set to 10% (S7). Here, the threshold is not only 10%, but also
A value of 5-10% is suitable. This is because the actual pattern area ratio of ink characters is often 5 to 10%, and the pattern area ratio in this range is easily affected by the grain of the printing plate when measuring. This is because, considering the emulsification balance, it is known that ink presetting is more effective if the ink key is forcibly opened to a certain level.

As a result, black characters are printed clearly and stably.

Next, correction for color plates below the black plate will be explained. Here, too, at the start of the measurement, the pattern area ratio is measured for each beam spot (S3b). but,
Next, before totaling the pattern area ratio for each ink zone, the pattern area ratio for each beam spot is corrected.

In other words, the pattern area ratio for each beam spot is 10
% or less (S8). If it is less than 10%, the corrected pattern area ratio for each beam spot is forcibly set to 0% (S9). If it is not 10% or less, the value obtained by multiplying the measured value by 120% is set as the corrected pattern area ratio (S10). Here, the threshold is not only 10%;
A value of 5-10% is desirable. As mentioned above, this value takes into consideration the influence of the grain of the printing plate. Also, it is desirable that the multiplication value is not only 120%, but a value of 100 to 150%. This is a correction that takes into account the image area ratio and ink emulsification balance of color plates other than black plates in the encyclopedia. As a result, ink supply is reduced to zero for white backgrounds to prevent background smearing, and sufficient ink supply is ensured for picture areas, allowing high-quality printing.

After performing the above-described image area ratio correction for each beam spot, the image area ratio for each ink zone is totaled and calculated (S11).

By performing such processing, the effect of ink presetting can be considerably improved for printing printed materials such as encyclopedias.

In this embodiment, the vibration of the ink roller is further corrected.

First, it is determined whether the pattern area ratio of the ink zone is 0% (S12). If it is not 0%,
The value as it is is set as the corrected pattern area ratio (S13).

If it is 0%, it is determined whether the left and right ink zones are 0% (S14). If it is 0%, it is assumed that there is no pattern at all, and the pattern area ratio of the ink zone is set to 0% (S13). If there is a pattern on either the left or right side, in order to compensate for the influence of the vibration of the ink roller, the corrected pattern area ratio is calculated by multiplying the larger pattern area ratio of the left and right ink zones by 25%. (S15). This is because the ink supplied to each ink zone through each ink key tends to escape to the adjacent zone where it is consumed.
This is to ensure that ink is stably supplied to the plate cylinder by utilizing this. Here, the value to be multiplied is 25
%, but 20-50% has been found to be suitable.

As explained above, according to this embodiment, if the area ratio calculated for each ink zone is less than a certain value for a black plate, correction is performed by rounding up,
For plates other than black plates, if the area ratio at each measurement point is below a certain value, the area ratio is corrected to zero, and if it is not below the certain value, the area ratio is multiplied by a predetermined number. After that, when calculating the area ratio by aggregating each correction data for each ink zone, the vibration effect of the ink roller is corrected, so the minimum value of the ink amount for each ink zone for any color plate is calculated. is guaranteed.

Although the present invention has been explained above based on a specific embodiment, the present invention is not limited to the above embodiment, and if the purpose is similar, the effect of ink presetting can be obtained in the same way, so various modifications can be made. It is possible.
For example, in the above embodiment, when calculating the area ratio for each ink zone, if the printing plate is a black plate, the area ratio below a certain value is corrected by rounding up, so the vibration effect of the ink roller is corrected. However, if such round-up correction is not performed, it is necessary to correct the vibration effect of the ink roller for the black plate as well. Further, in the above embodiments, the correction was performed by program processing using a microcomputer or the like, but there is no problem if similar processing is realized by a circuit configuration.

[Effect of idea]

As explained above, according to this invention, when calculating the pattern area ratio for each ink zone by aggregating the pattern area ratio for each measurement point for each ink zone, the pattern area ratio for each ink zone is Since the correction takes into account the vibration of the ink roller based on the pattern area ratio of the left and right zones of the zone,
Since the minimum value of the area ratio for each ink zone is guaranteed, sufficient ink can be supplied to the image area, enabling high-quality printing, and providing an image area ratio measuring device that increases the effectiveness of ink presetting. be done.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of an embodiment of the picture area ratio measuring device according to this invention, and FIG. 2 is a flowchart showing the operation of this embodiment. 1... Printing plate, 2... Ink zone, 3... Laser light source, 4... Scanner, 5... Beam spot, 6... Photoelectric conversion element, 7... A/D converter,
8...CPU.

Claims (1)

[Scope of Claim for Utility Model Registration] In order to preset the ink supply amount for each ink key of a printing press according to the area ratio of the printing plate, the area ratio of each point on the printing plate is measured for each ink zone. In a pattern area ratio measuring device that calculates the area ratio of each ink zone by totaling, if the area ratio of an ink zone is 0% and the area ratio of either the adjacent left or right ink zone is not 0%, the ink zone is A pattern area ratio measuring device characterized in that the area ratio is corrected to a value obtained by reducing the area ratio of the left and right ink zones to a predetermined percentage of the larger area ratio of the area ratios of the left and right ink zones.