JP2002307644A - Method for preventing printing failure from occurring in offset rotary press - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for more effectively preventing a printing failure attributed to delamination from occurring. SOLUTION: This method is invented for preventing a printing failure attributed to delamination in an offset rotary press from occurring and also for preventing the printing failure in the offset rotary press characterized in that the angle of a halftone dot outputted to a printing plate is set within 30 deg.. In addition, this method is invented for preventing the printing failure due to delamination in the offset rotary press, and for preventing the printing failure in the offset rotary press which is characterized in that the angle of a halftone dot outputted to the printing press is 0 deg. and the shape of the halftone dot is linear.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for preventing printing defects due to delamination in an offset rotary printing press.

[0002]

2. Description of the Related Art In web offset printing presses for printing on rolled paper, a phenomenon called "delamination" in which the paper is picked up on a blanket cylinder may occur. This is the imbalance of the dot area ratio of the upper and lower trunk blanket,
This phenomenon is likely to occur in the case of high ink adhesiveness, insufficient tension in the printing press, and the like, and printing deficiencies such as white spots and dubbing of a printed image occur due to this phenomenon.

[0003] This delamination will be described with reference to FIG. FIG. 7 is an explanatory diagram showing the traveling properties of the printing paper in a normal state and when delamination occurs. Printing paper 1
0 travels from right to left, and the ink on the blanket is transferred to the printing paper 10 while passing between the lower body blanket 11 and the upper body blanket 12 on the upstream side, and a print image of a predetermined color is formed. After printing on the back and front sides of printing paper, the upper and lower blankets on the downstream side (not shown)
, Where a print image of another color is printed.

[0006] The reason why the upper body blanket 12 advances in the running direction of the printing paper 10 as compared with the lower body blanket 11 is called a stacker amount. Always about 5
The winding is to suppress the fluctuation of the tension when the printing paper 10 passes between the upper and lower drum blankets. Accordingly, the normal running property of the printing paper is such that it runs around the upper and lower body blankets by about 5 ° as indicated by the solid line, and normal printing can be performed by maintaining the running property in this state.

On the other hand, the dotted line Y and the dotted line Z show the running state of the printing paper when the delamination occurs, and the dot area ratio of the lower body blanket 11 is large (the ink coverage is large). When the halftone dot area ratio of the upper body blanket 12 is small (the amount of ink is small), the printing paper 10 is pulled toward the lower body blanket 11, so that the running state Y when the delamination occurs as indicated by a dotted line. Delamination occurs, and in the opposite case, the printing paper 10 is pulled toward the upper body blanket 12 side.
A delamination like the running state Z at the time of occurrence of the delamination indicated by the dotted line occurs.

With reference to FIG. 9, a description will be given, with reference to FIG. 9, of a printing failure as shown in a print image 17 in which a blank printing failure occurs in FIG. 8 among the printing failures due to the delamination. FIG. 9 is an explanatory diagram showing ink transferability to printing paper when delamination occurs. In FIG. 9, when the halftone dot area ratio of the lower body blanket 11 is large (the amount of the lower body ink 13 is large) and the halftone dot area ratio of the upper body blanket 12 is small (the amount of the upper body ink 14 is small). On the lower body blanket 11 side, the printing paper 10 is normally wound like the winding amount X around the blanket, whereas on the upper body blanket 12 side, the printing paper 10 is pulled toward the lower body blanket 11 side, and A delamination like the running state Y at the time of the delamination occurs, and a normal winding amount cannot be maintained. As a result, the ink transfer from the upper cylinder blanket 12 to the printing paper 10 becomes insufficient, and printing proceeds in this state, so that a small amount of ink residue 18 is generated on the upper cylinder blanket 12 and finally the ink residue 18 Is deposited and dried.

FIG. 10 shows a state in which ink residue 18 is deposited on the upper cylinder blanket and dried. FIG. 10 is an explanatory view showing an aspect in which the ink film portion is formed on the upper barrel blanket. As shown in FIG. 10, an ink film portion 19 due to ink residue is formed on the upper cylinder blanket 12, and the ink film portion 19 is inferior to the peripheral portion in ink adhesion. It is thought that a defect will occur.

[0008] Conventionally, in order to prevent printing defects caused by such delamination, the purpose of reducing the difference in tension between the upper and lower blankets has been to reduce the viscosity of ink or increase the tension of the printing press due to the addition of additives.
In order to prevent the delamination itself, measures such as installation of an air nozzle device have been adopted.

[0009] However, when additives are contained in the ink, printing conditions such as color tone change, the tension of the printing press is increased to cause paper breakage, and a new air nozzle device or the like is used to prevent delamination itself. In addition, there are problems such as the necessity of installation of various facilities and a reduction in the work space of the printing operator.

[0010]

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems, and to provide a method of preventing printing defects in an offset rotary printing press for preventing printing defects due to delamination. To provide.

[0011]

Means for Solving the Problems As a result of intensive studies in view of the above, the present inventors have invented a method for preventing printing defects in an offset rotary printing press of the present invention.

A method for preventing printing defects in an offset rotary printing press according to the present invention is a method for preventing printing defects due to delamination in an offset rotary printing press. ° or less.

In the above invention, the halftone dot shape is one type of halftone dot shape selected from a circle, an ellipse, an inverted circle, an inverted ellipse, a square, a rhombus, a diamond, a linear shape, and a mixed molding. I do.

In the above invention, the halftone dot shape is preferably linear.

The method for preventing printing defects in an offset rotary printing press according to the present invention is a method for preventing printing defects caused by delamination in an offset rotary printing press, wherein the halftone dot angle output to the printing plate is zero. °, and the dot shape is linear.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A method for preventing printing defects in an offset rotary printing press according to the present invention will be described below in detail with reference to the drawings.

FIG. 1 is an explanatory view showing a method for preventing printing defects in an offset rotary printing press according to the present invention.
In FIG. 1, the halftone dot angle 2 of the print image 1 indicates 0 ° parallel to the running direction of the printing paper. The halftone dot angle 4 of the print image 3 indicates 45 °. The halftone dot angle 6 of the print image 5 is
It shows 90 ° perpendicular to the running direction of the printing paper.

However, depending on the film or the printing plate output machine,
Since the halftone dot angle parallel to the running direction of the printing paper may be 90 °, the numerical value of the halftone dot angle conforms to a film or a printing plate output machine.

Each of the print images 1, 3, and 5 in FIG. 1 has a band solid image on the back side of the printing paper and a gradation image on the front side of the printing paper so as to overlap the position of the band solid image. This is a printed image, and shows the printing state of the gradation image on the front side.

As shown in FIG. 1, a clear gradation image can be seen in the print image 1 when the halftone dot angle 2 parallel to the running direction of the printing paper is 0 °.
This is a method for preventing printing defects due to delamination in the present invention. On the other hand, in each of the print images 3 and 5, a white spot-like print defect such as a virtual image of a solid band image has occurred inside the gradation image. Here, when the halftone dot angle 4 corresponding to the print image 3 is 45 ° and the halftone dot angle 6 corresponding to the print image 5 is 90 °, when the halftone dot angle is from 45 ° to 90 °, a white spot is formed. It can be seen that print defects are conspicuous.

That is, as specified in the present invention, by setting the dot angle to 30 ° or less, preferably to 0 °, printing defects due to delamination can be prevented. However, when the halftone dot angle exceeds 30 ° and 90 °
, The occurrence of printing failure due to delamination becomes severe.

Printing of the print image shown in FIG. 1 will be further described with reference to FIG. FIG. 2 is an explanatory diagram showing print positions of a solid band image and a gradation image. On the back side of the printing paper, a solid band image 7 which is a heavy image having a dot area ratio of 100% is printed by the lower body blanket. Also, on the front side of the printing paper, a dot area ratio of 0 to
A gradation image 8 expressing a gradation from a light image of 100% to a heavy image is printed by the upper body blanket. The printing position relationship between the images is such that the solid band image is printed at the printing position 9 within the dotted frame shown inside the gradation image 8 with respect to the gradation image 8. However, the solid band image is printed on the back side of the printing paper.

As described above, the print image on the front side when printed by the arrangement on the back and front sides in FIG. 2 is shown in FIG.
Are the print images 1, 3, and 5, respectively.

Next, the phenomenon that delamination occurs due to the upper and lower body blankets will be described with reference to FIGS. On the upper body blanket 12 side, upper body ink 14 corresponding to a light image is printed on the front side of the printing paper 10. On the other hand, on the lower body blanket 11 side, the lower body ink 13 corresponding to the heavy image is printed on the back side of the printing paper 10. The upper and lower cylinder blankets are arranged such that the cylinder cores are displaced from each other, and the upper and lower cylinder inks 14 and 13 of the upper and lower cylinder blankets are respectively printed on the upper and lower cylinder blankets 12 and 11 with an amount X wrapped around the printing paper. No. 10 is printed on the back side.

FIG. 3 is an explanatory diagram showing the running properties of the printing paper when delamination occurs. In FIG. 3, the printing paper 10 is pulled toward the lower body blanket 11 when the lower body ink 13 is printed on the printing paper 10 in an unbalanced state at the position of the winding amount X of the lower body blanket 11, The printing paper travels as indicated by the dotted line indicated by Y, and the upper body ink 14 of the upper body blanket 12 is insufficiently printed on the printing paper 10, resulting in so-called delamination.

FIG. 4 is an explanatory diagram showing the running property of the printing paper in a normal state. In FIG. 4, the upper and lower trunk blanket 1
At the positions of the winding amount X of 2 and 11, the printing paper is running in a well-balanced state, the upper body ink 14 and the lower body ink 13 are both normally printed on the printing paper 10, and no delamination occurs.

FIGS. 3 and 4 described above will be described more specifically. FIG. 5 is a perspective view showing the traveling properties of the printing paper during the printing of the discontinuous upper body image corresponding to FIG. In FIG. 5, a heavy image such as the band solid image 7 is arranged on the lower body blanket 11 side, and a light image is arranged on the upper body blanket 12 side to print on the back and front sides of the printing paper 10. In the halftone dot angle of 90 ° parallel to the width direction of the upper body blanket 12, that is, in the discontinuous upper body image 15, the upper body image 15 is arranged discontinuously with respect to the traveling direction of the printing paper 10. Since the torso image 15 intermittently contacts the printing paper 10, the tension when the printing paper 10 is peeled from the upper blanket 12 is weaker than that when the halftone dot angle is 0 °. Accordingly, when the halftone dot area ratio of the upper and lower cylinder blankets is unbalanced and the halftone dot angle is 90 °, the printing paper 10 is pulled toward the lower cylinder blanket 11 and the upper cylinder blanket 12
On the side, delamination such as the running state Y of the printing paper indicated by the dotted line occurs, and the normal winding amount X cannot be maintained. As a result, the printed image appears as a blank white print defect. This is as shown in the print image 17 in which a blank-form print failure has occurred, as described above with reference to FIG.

On the other hand, FIG. 6 is a perspective view showing the traveling properties of the printing paper when printing a continuous upper body image corresponding to FIG. FIG. 6 shows a lower trunk blanket 11 similar to FIG.
A heavy image such as a band solid image 7 is arranged on the side, a light image is arranged on the upper body blanket 12 side, and printing is performed on the back and front sides of the printing paper 10. In the halftone dot angle of 0 ° perpendicular to the width direction of the upper body blanket 12, that is, in the continuous upper body image 16, the upper body image 16 is arranged continuously with respect to the traveling direction of the printing paper 10, and always has the upper body image 16. Since the image 16 is in contact with the printing paper 10, the tension when the printing paper 10 is peeled from the upper body blanket 12 is stronger than that when the halftone dot angle is 90 °. Therefore, even if the halftone dot area ratio of the upper and lower body blankets is unbalanced, in the case where the halftone dot angle is at 0 °, it is possible to keep the difference in tension when the printing paper 10 peels off from the upper and lower body blankets small. Printing paper 10 on the upper body blanket 12 side
Is normally wound like the amount of winding X around the upper body blanket, and therefore, does not cause white-out printing defects.

In FIGS. 5 and 6 described above, the halftone dot angles are 90 ° and 0 °, respectively. However, in the present invention, when printing in single color or multicolor, white dots caused by delamination are generated. The halftone dot angle that does not cause missing printing defects is to be within 30 °. However, in the case of multi-color printing, if a halftone angle within 30 ° is used among existing halftone angles, printing failure such as moiré may occur. In that case, reduce moiré. It is preferable to adjust the dot angles of other colors around the dot angle set within 30 ° for the purpose of. It is also conceivable to use a plurality of halftone dot shapes in combination with the halftone dot shape, and printing defects such as moiré may occur depending on the printed image. In this case, screen lines are used for the purpose of reducing moiré. It is preferable to shift the number in the direction of high definition.

In the present invention, as the dot shape, one kind of dot shape selected from a circle, an ellipse, an inverted circle or an inverted ellipse, a square, a rhombus, a diamond, a linear shape, and a mixed shape can be arbitrarily used. Although there is no particular limitation, it is preferable that the halftone dot shape that is more effective against blank printing defects is a linear halftone dot shape.

Further, in the present invention, the halftone dot angle is set to 0 °.
In addition, in the combination in which the halftone dot shape is linear, an extremely excellent effect can be exhibited in preventing printing failure due to delamination.

Such a combination of the halftone dot angle and the halftone dot shape will be described with reference to FIG. 1. The halftone dot angle 2 of the printed image 1 in FIG. 1 is 0 °, and the halftone dot shape in FIG. It is linear from shape.

A description will be given with reference to the perspective view of FIG. 6 which shows the running property of the printing paper during continuous printing of the upper body image.
And a light image is arranged on the upper body blanket 12 side to print on the back and front sides of the printing paper 10. The halftone dot angle of 0 ° perpendicular to the width direction of the upper trunk blanket 12, that is, a continuous upper trunk image 16
In the figure, the upper torso image 16 is continuously arranged in the running direction of the printing paper 10, and the upper torso image 16 is always
The printing paper 10 is in contact with the upper body blanket 1
The tension at the time of peeling from 2 is stronger than that at a halftone angle of 90 °, and the halftone dot shape is more linear and continuous than an intermittent shape such as a diamond shape. Is strong. Therefore, even if the halftone dot area ratio of the upper and lower body blankets is unbalanced, if the halftone dot angle is 0 ° and the halftone dot shape is linear, the tension at the time when the printing paper 10 is peeled off from the upper and lower body blankets. The difference can be kept small, and the printing paper 10 on the upper body blanket 12 side is normally wound like the winding amount X on the upper body blanket, so that there is no occurrence of blank-shaped printing failure. This is a very efficient method of preventing delamination.

[0034]

As described above, by setting the halftone dot angle according to the present invention within 30 °, printing defects due to delamination in an offset rotary printing press can be prevented, and the halftone dot angle can be reduced. With a combination of 0 ° and a linear halftone dot shape, it is possible to extremely efficiently prevent a printing defect caused by delamination in an offset rotary printing press.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram showing a method for preventing printing defects in an offset rotary printing press according to the present invention.

FIG. 2 is an explanatory diagram showing print positions of a solid band image and a gradation image.

FIG. 3 is an explanatory diagram illustrating the traveling properties of printing paper when delamination occurs.

FIG. 4 is an explanatory diagram showing the running property of printing paper in a normal state.

FIG. 5 is a perspective view illustrating the traveling properties of a printing paper when a discontinuous upper body image is printed.

FIG. 6 is a perspective view illustrating the traveling properties of printing paper during continuous printing of an upper body image.

FIG. 7 is an explanatory diagram showing the traveling properties of printing paper in a normal state and when delamination occurs.

FIG. 8 is a plan view showing an upper torso image in which a blank printing failure has occurred.

FIG. 9 is an explanatory diagram showing ink transferability to printing paper when delamination occurs.

FIG. 10 is an explanatory view showing an aspect in which an ink film portion is formed on an upper barrel blanket.

[Explanation of symbols]

 1, 3, 5 print image 2 halftone dot angle of print image 1 4 halftone dot angle of print image 6 6 halftone dot angle of print image 5 7 solid band image 8 gradation image 9 print position 10 print paper 11 lower body blanket 12 upper Drum blanket 13 Lower drum ink 14 Upper drum ink 15 Non-continuous upper drum image 16 Continuous upper drum image 17 Print image with blank printout failure 18 Ink residue 19 Ink film part X Wrap amount around blanket Running state of printing paper when Y, Z delamination occurs

Claims (4)

[Claims] 1. A method for preventing printing defects due to delamination in an offset rotary printing press, comprising:
A method for preventing defective printing in an offset rotary printing press, wherein a halftone angle output to a printing plate is set to 30 ° or less. 2. A halftone dot shape selected from a circle, an ellipse, an inverted circle or an inverted ellipse, a square, a rhombus, a diamond, a line, and a mixed shape. Item 4. A method for preventing printing defects in an offset rotary printing press according to Item 1. 3. The method for preventing printing defects in an offset rotary printing press according to claim 1, wherein the halftone dot shape is linear. 4. A method for preventing printing defects due to delamination in an offset rotary printing press, comprising:
A method for preventing printing defects in an offset rotary printing press, wherein a halftone dot angle output to a printing plate is 0 ° and a halftone dot shape is linear.