JPH10272765A - Inking roller - Google Patents

Abstract

PROBLEM TO BE SOLVED: To ensure a stabilized print image quality by setting the rubber hardness of a single urethane rubber layer formed on a roller core metal such that the single urethane rubber layer has a specified hardness when the surface temperature thereof has a specified level thereby preventing generation of paper powder streak or blanc contamination (white ground contamination). SOLUTION: Since an inking roller 2 is provided by forming a single urethane rubber layer 12 on a roller core metal 11 with the rubber hardness of the single urethane rubber layer 12 being set at 40-45 deg. when the surface temperature thereof is 25 deg.C, generation of paper powder streak (white streak) due to missing of ink can be prevented effectively. The rubber hardness is based on JIS spring type hardness test type A. The inking roller is especially suitable for an inking unit having a doctor blade in a waterless offset printer, it may be employed in other waterless printers or a doctor blade type inking unit for water offset printer employing a PS plate, etc.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an inking roller used in an inking device of an offset printing press.

[0002]

2. Description of the Related Art Conventionally, an inking device for an offset printing press has an inking provided with a doctor blade which is pressed against an inking roller so as to form an ink film having a predetermined thickness on the peripheral surface of the inking roller. It is also known that the apparatus is known and that such an inking roller is formed by forming one or two rubber layers on a roller cored bar. For example, it is disclosed in JP-A-62-51453.

[0003] In addition, as disclosed in the same publication, when forming two rubber layers, the inner layer may be made of soft nitrile rubber (NBR) and the outer layer may be made of hard nitrile rubber. It is known.

[0004]

However, such a conventional inking roller (using a nitrile rubber) is used.
Because the amount of plasticizer used to form the material is large, it reacts with the ink, and the plasticizer in the rubber solid is extracted by the pressure contact of the doctor blade. The hardness increases by 10 degrees or more from the initial hardness, and the roller diameter also decreases by 0.5 mm or more.

Conventionally, paper dust mixed from the surface of the paper into the ink fountain of the doctor blade via the blanket, the plate surface, and the inking roller is deformed when the rubber hardness is set to an initial value. Although it passes through between the surface and the tip of the blade, the outer circumference of the rubber is not deformed due to the increase in rubber hardness. No longer formed, and the paper-clogged portion appears as streaks on the ink film surface, and also appears on the printing surface.

[0006] When the diameter of the rubber roller is smaller than the initial value due to the removal of the plasticizer, the ink film thickness set by pushing the doctor blade into the rubber surface is reduced due to the reduced diameter of the rubber roller. , The ink film thickness increases, and the printing density on the printing surface becomes high.

Further, as the roller diameter becomes smaller, the surface speed of the plate cylinder during rotation and the surface speed of the rubber roller become unequal, and a slip is induced to cause blank stains (stain on a white background on a picture of a printed matter. (Also called white background stain)
Had the drawback of easily occurring.

The present invention has been made in view of the above-mentioned drawbacks, and since the plasticizer content of urethane rubber is significantly smaller than that of nitrile rubber, the change in rubber hardness and diameter Since it has excellent stability, it is suitable for an ink forming roller used in a doctor blade type inking device.

Further, the rubber layer is made of a urethane rubber single layer, and the hardness of the rubber layer is set to 40 ° C. when the single layer surface temperature is 25 ° C.
It has been found that by providing the angle of 45 degrees, it is possible to effectively prevent the occurrence of paper dust streaks and white stains (white background stains) and to obtain a stable print image quality, thereby completing the invention.

[0010]

That is, an ink forming roller according to the present invention is an ink forming roller used in an inking device having a doctor blade of an offset printing press, and is a urethane rubber formed on a roller core metal. The rubber hardness of the single layer was 4 when the single layer surface temperature was 25 ° C.
It is characterized by being provided so as to be 0 degree to 45 degrees.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a front view showing an inking device of an offset printing press. In FIG.
An auxiliary ink forming roller 3, a first kneading roller 4, a second kneading roller 5, a doctor blade 6, an ink fountain 7 and the like are provided. Are mounted so that they can be pressed against and separated from a plate (not shown) wound around the plate cylinder 8.

At the time of printing, as shown in FIG.
The inking roller 2 and the auxiliary inking roller 3 are pressed against a plate (not shown) wound around the plate cylinder 8 at a predetermined pressure, and at the same time, a shaft portion of the plate cylinder 8 (not shown). ) And the shaft portion 11 a of the inking roller 2.
The gear (not shown) mounted on the gear (see FIG. 2) is engaged with the gear, and therefore, the inking roller 2 is driven and rotated by the plate cylinder 8.

At this time, since the plate cylinder 8 rotates clockwise,
The inking roller 2 is rotated counterclockwise, so that the first and second kneading rollers 4 and 5 pressed against the inking roller 2 are rotated clockwise, and the plate cylinder 8 and the second
Auxiliary inking roller 3 pressed against kneading roller 5
Is rotated counterclockwise.

For this reason, the ink in the ink fountain 7 is attached to the peripheral surface of the roller along with the rotation of the ink application roller 2 and is transferred. When the ink passes through the area where the doctor blade 6 is pressed against the ink, the predetermined film thickness is obtained. Is formed. The doctor blade 6 is provided with a pressure cam 9 so that a predetermined film thickness can be formed in accordance with the rotation amount of the pressure cam 9.
And presses against the ink forming roller 2.

Further, the ink adhering to the outer periphery of the ink forming roller 2 is made to have an ink surface in an uneven state suitable for printing by the first kneading roller 4.
Is attached to the surface of a plate (not shown) wound around the plate. At that time, the auxiliary inking roller 3
Collects excess ink on the plate surface, and returns them to the inking roller 2 via the second kneading roller 5.

As described above, since the ink is supplied directly to the ink forming roller 2 via the doctor blade 6, the amount of ink adhering to the peripheral surface of the ink forming roller 2 is always constant regardless of the pattern of the plate. Will be kept. Therefore, the operator only needs to adjust the density of the entire printed matter.

However, since the doctor blade 6 is pressed against the inking roller 2, when foreign matter such as paper powder is caught between the doctor blade 6 and the inking roller 2, the foreign matter is immediately locally applied to the peripheral surface of the roller. Insufficiency of ink occurs, and as a result, paper dust streaks (white streaks) due to ink loss occur in printed matter. When such a situation occurs, it is difficult to cope with the situation via the first kneading roller 4, and other measures are required.

However, in the present invention, as shown in FIG. 2, the inking roller 2 is formed by forming a urethane rubber single layer 12 on a roller core 11 and furthermore, Since the rubber hardness is set so as to be 40 to 45 degrees when the surface temperature of the single layer is 25 ° C., it is possible to effectively prevent the generation of the paper dust streaks (white streaks) due to the above-mentioned ink loss. it can. The rubber hardness referred to herein is based on the JIS spring type hardness test A type (all rubber hardness described below is based on this standard).

Table 1 shows the change over time in the outer diameter and rubber hardness of the ink forming roller 2 when printing was performed using the above-described inking device 1 shown in FIG. 1 (an embodiment according to the present invention). Where the change in the outer diameter of the roller is shown in mm.

[0020]

[Table 1] Further, Table 2 shows that the ink forming roller 2 of the inking device 1
Are shown in the case of printing with a conventional ink forming roller (Comparative Example). In FIG. 3,
Although such a conventional inking roller is shown, the inking roller includes an inner layer 13 (having a hardness of 25 degrees) made of soft nitrile rubber on a roller core 11,
The outer layer 14 made of hard nitrile rubber (having a hardness of 40
) To form a two-layer rubber layer.

[0021]

[Table 2] When both are compared, the inking roller 2 according to the example is superior in both the dimensional stability and the hardness stability since the roller outer diameter and the amount of change in rubber hardness with time are small. I understand.

That is, in Comparative Example A, although the number of printed sheets is less than half the number of printed sheets in the example, paper hardness (white streaks) due to paper dust or the like is generated. It has reached a level that is easy to do (near 50 degrees).
For this reason, it is difficult to satisfactorily print a number close to the number of prints (about 1.6 million sheets) in the embodiment, and even if it is printed, the rubber hardness thereof becomes an unusable level.

This is because, in Comparative Example B in which the number of printed sheets is about 1.5 million, the rubber hardness has reached a level (close to 50 degrees) where paper dust lines (white stripes) due to paper dust or the like are easily generated. It is clear even if. In Comparative Example B, since the outer diameter of the roller was greatly reduced,
If the pressure by the pressure is not adjusted to a predetermined value, the effect becomes insufficient and a predetermined print density cannot be obtained.

On the other hand, in the embodiment, the change in rubber hardness is only 1 to 3 degrees even when about 1.6 million sheets are printed, and the outer diameter of the roller is also reduced by 0.2 mm. For this reason, even if the ink forming roller 2 having a rubber hardness of 42 degrees is used, paper dust lines (white lines) are generated for a longer time than the conventional ink forming roller. It can be seen that it is advantageous to obtain a longer life.

In each of the above Examples and Comparative Examples A and B, the outer diameter of the roller was measured when the rotation was stopped after use. Therefore, during printing, the doctor blade is pressed against the inking roller, so that frictional heat is generated during printing, and the doctor blade expands under the influence of the doctor blade to increase the outer diameter of the roller. You.

For this reason, a peripheral speed difference from the plate cylinder is generated, and slip is induced to easily cause blank stain (white background stain). In addition, the ink is also heated, and the viscosity of the ink decreases due to the temperature rise. As a result, the ink easily adheres to the silicon coating of the plate material (white background during printing). ) Is more likely to occur.

However, the inking roller 2 according to the present invention
According to this, it is possible to effectively prevent such a fatal situation from occurring. That is, in general, a roller having a low rubber hardness is easy to thermally expand, and
In addition, frictional heat is generated, and Blanc stains (white background stains) accelerated.
The ink forming roller 2 according to the present invention
Since the rubber hardness is set in the range of 40 to 45 degrees, the occurrence of blank stain (white background stain) can be effectively prevented.

Table 3 shows a blank stain (white background stain) in another example (another embodiment according to the present invention) when printing is performed using the above-described inking apparatus 1 shown in FIG.
And the generation state of paper dust streaks. In this example, the inking roller 2 has a urethane rubber single layer 12 having a rubber hardness of 45 degrees when its surface temperature is 25 ° C.

[0029]

[Table 3] Table 4 shows the rubber hardness of the urethane rubber single layer 12 in another example (another comparative example) using an inking roller provided at 38 degrees when the single layer surface temperature was 25 ° C.

[0030]

[Table 4] In both tables, the rubber hardness of each of the ink forming rollers at the start (at the start of printing) is the set hardness (45 degrees, 38 degrees).
The reason for the lowering of the degree than the degree is due to the fact that the inking device was operated at a low speed to stabilize the viscosity of the ink to a level suitable for printing. The room temperature, plate temperature, and ink temperature in both tables are all in ° C., ○ indicates no occurrence, and X indicates occurrence.

When both are compared, the rubber hardness is 38.
In the comparative example using a degree of inking roller,
In contrast to the case where the number of printed sheets is 2000 and blank stains (white background stains) are generated, in the embodiment using the ink forming roller 2 having a rubber hardness of 45 degrees, such is not generated. Since no scumming (smearing on a white background) occurs even on 10,000 sheets, it can be seen that the inking roller 2 according to the present invention is more advantageous.

In addition, the influence of the printing temperature was examined, and the results are shown in Table 5. Room temperature, plate temperature,
The ink temperature is in ° C., and O indicates no occurrence. In this example (another embodiment according to the present invention), the inking roller 2 has a surface temperature of the urethane rubber single layer of 35 ° C. At 39 ° C (42-43 at 25 ° C)
And a cooler of a floor-standing air-cooling type was used.

When a large amount of printed matter is continuously printed using waterless ink, the temperature of the plate surface during printing rises to cause background smear on the printed material. Need to be cooled by a cooler,
Even if the material of the rubber roller is other than urethane rubber, the use of a cooler is necessary.

[0034]

[Table 5] At the time of printing 4000 sheets, practically negligible blank stain (white stain) was generated (indicated by △ in the table), but when the cooler was operated and cooled, it disappeared. And the temperature of the plate cylinder 8 and the ink is set to 200
The level could be reduced to the level before the printing of zero sheets. Therefore, the ink application roller 2 according to the present invention has an advantage that the temperature of the plate cylinder 8 and the ink is controlled to a predetermined value via the cooler, so that the occurrence of blank stain (white background stain) can be easily prevented. . Note that it is difficult to adjust the rubber hardness of urethane rubber by adding a predetermined agent (additive) like nitrile rubber.
It is preferable to consider the degree of variation,
What is necessary is just to set to 0 degree-45 degree.

As described in detail above, in the present invention, the ink forming roller is formed by forming a urethane rubber single layer on the roller core metal, and furthermore, the rubber hardness of the urethane rubber single layer is determined by measuring the surface of the single layer. The temperature is set to be 40 to 45 degrees when the temperature is 25 degrees Celsius. For this reason, even if this ink forming roller is used for an inking device having a doctor blade, a fatal situation such as a blank stain (white stain) or a paper dust streak (white streak from which an image is missing) occurs. Can be effectively prevented, and the printing density can be stabilized.

The inking roller according to the present invention comprises:
In particular, it is suitable to be used for an inking device having a doctor blade of a waterless offset printing press, but it is also suitable for other bladeless inking devices such as a waterless printing press or a water-based offset printing press using a PS plate. May be used.

[0037]

As described above, according to the present invention, an ink forming roller suitable for use in an inking device having a doctor blade of an offset printing press, that is, a blank stain (white background stain) or a paper dust line (image Missing white streak)
It is possible to obtain an ink forming roller capable of preventing the occurrence of the above.

[Brief description of the drawings]

FIG. 1 is a front view showing a schematic configuration of an inking device of an offset printing press.

FIG. 2 is a sectional view of an inking roller according to the present invention.

FIG. 3 is a cross-sectional view of a conventional inking roller.

[Explanation of symbols]

 DESCRIPTION OF REFERENCE NUMERALS 1 inking device 2 inking roller 3 auxiliary inking roller 4 first kneading roller 5 second kneading roller 6 doctor blade 7 ink fountain 8 plate cylinder 9 pressure cam 10 contact / separation lever 11 roller core 12 urethane rubber single layer

Continued on the front page (72) Inventor Tetsuo Tomimura 1-1-45 Oe, Otsu City, Shiga Prefecture Toray Engineering Co., Ltd.

Claims (1)

[Claims] 1. An ink forming roller for use in an inking device having a doctor blade of an offset printing machine, wherein the rubber hardness of a urethane rubber single layer formed on a roller core is determined by measuring the single layer surface temperature at 25 ° C. At 40 degrees ~
An inking roller provided at 45 degrees.