JPH1148628A - Gravure printing block and printing sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a gravure printing block for increasing the density of shadow sections even by using the same amount of ink and also provide a printing sheet with increased density of shadow sections. SOLUTION: In a direct gravure block on which cells are formed by corroding non-resist sections on a resist pattern face on the surface of a block, non resist sections 2 of the resist pattern are disposed in the square shape, and central positions 5 of the squares are so disposed as to conform to the central positions 5 of circles in minutely filling patterns in which one circle and six circles of same diameter encircling said one circle are so disposed as to adjoin one another, and two sides of the squares are set in parallel with a straight line (a) in one direction out of straight lines a-c in three directions connecting central points of circles one another, while being set crossing straight lines (b) and (c) in the other directions. Also a printing sheet is constituted of an assembly of circular printing dot patterns 4 forming the minutely filling disposition.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gravure printing plate and a printing sheet capable of increasing the density by using the same amount of ink.

[0002]

FIG. 3 is a correlation diagram of a resist pattern R ', a cell pattern C', and a print dot pattern D 'in a conventional direct etching plate making gravure (hereinafter, referred to as direct gravure). FIG. 3A shows an example of a conventional resist pattern R ′ including a resist portion 1 and a square non-resist portion 2 in a shadow portion on a direct gravure printing plate surface. In this state, the opening of the resist pattern R ′, that is, the plate surface immediately below the non-resist portion 2 is corroded, and due to the effect of side etching, the bank 3 forming a non-image portion as shown in FIG. A cell pattern C ′ including the cells 4 forming the circular image portion is formed. This cell 4 is located at the intersection of orthogonal square lattices. This is because a gravure orthogonal screen has been used for forming the resist pattern R ′. In the gravure printing, the ink filled in the cells 4 is transferred to the sheet to be printed to form a print dot pattern D ′, and the print dot pattern D ′ becomes substantially the same as the cell pattern C ′. 3 (b). A bank 3 must be formed between the cells 4, and it is necessary to minimize the width of the bank in the shadow portion to maximize the cell area. Therefore, if the square in the resist pattern R ′ becomes even larger than that of FIG. 3A, the cell 4 cannot be a perfect circle as shown in FIG. Various changes. However, in any case, FIG.
The part where the corners of the squares gather in is slow to enter corrosion,
The side etch is also small, and the tendency of the area of the intersection of the banks 3 to increase as shown in FIG. FIG. 4 shows another example of a known resist pattern and a known cell. Further, a resist pattern R ″ formed by using a honeycomb screen as shown in FIG. 4A is known, while a cell seen in an engraved gravure printing plate as shown in FIG. A pattern C "and a print dot pattern D" based on the pattern C "are practically used.

[0003]

In order to increase the print density from the halftone to the shadow in a conventional direct gravure printing plate having a cell pattern C 'as shown in FIG. As long as is maintained between adjacent cells 4, the maximum expansion and depth have been performed,
Since a considerably large non-image area remains at the intersection of the banks 3, there is a problem that the expansion of the cell area ratio is limited. On the other hand, even if the cells are deepened, all of the ink does not always transfer to the sheet to be printed, and there is a problem that the residual ink is partially solidified to cause printing defects such as printing unevenness and doctor streaks. Also, even if all the ink is transferred from the deep cells and a thick image part with an ink film is formed on the sheet to be printed, there is a fundamental problem that the thickness of the ink layer on the print aggregate density has a marginal efficiency. is there. Therefore, it is desirable to maximize the cell area ratio in the shadow portion. As a means for this, a screen having a honeycomb pattern is used as shown in FIG.
There is known a honeycomb cell pattern in which a resist pattern R "as shown in (a) is provided, and the periphery of the hexagon is uniformly side-etched to make the bank as thin as possible. There is a problem that it is difficult to prevent moiré in the case, because the angle must be adjusted only in the range of a rotation angle of 60 °, and in the case of an engraved gravure as shown in FIG. In order to prevent moiré, there is only a method of changing the cell shape for each multicolor plate, and even if the cell shape in the shadow portion is changed, the area ratio of the cell 4 cannot exceed a certain limit. There is a defect that the printing density of the shadow area is naturally limited and a strong printing cannot be performed. The shadow portion of the conventional gravure printing plate has almost the same problem as the direct gravure printing described above, and also has the greatest defect that introduces an unstable element called a carbon tissue in the plate making process. With the direct gravure method, it is possible to increase the print density of the shadow area from halftone without increasing the conventional ink amount, and if the conventional shadow area density is satisfactory, the amount of ink used will be It is an object of the present invention to provide a gravure printing plate and a printing sheet that can be reduced and that can adjust the moiré angle in a wide range.

[0004]

According to the present invention, there is provided a gravure printing plate and printing sheet according to the present invention, in which a non-resist portion of a resist pattern surface of a plate is corroded to form a cell. In the printing plate, the non-resist part of the resist pattern was arranged in a square, and the center position of the square was arranged such that one circle and six circles of the same diameter surrounding the circumference were adjacent to each other. Two sides of the square are parallel to a straight line in one direction among straight lines in three directions connecting the center points of the circle, and the direction of the square is made to coincide with the center position of the circle in the densely packed pattern. Cross printing with respect to the straight line in the two directions. Then, a gravure print sheet is formed from an aggregate of circular print dot patterns forming a close-packed arrangement.

[0005]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in more detail with reference to the drawings. FIG. 1 is a diagram for explaining the principle of forming a cell pattern C in a gravure printing plate and a printing dot pattern D in a gravure printing sheet according to the present invention. FIG.
(A) is an explanatory view of an arrangement of a resist pattern R formed on a plate surface. As shown in FIG. 1A, the resist pattern R of the gravure printing plate according to the present invention is such that the non-resist part 2 defined by the resist part 1 has a square arrangement, and the center position is One circle indicated by a dotted line and six circles of the same diameter surrounding the circle are arranged so as to coincide with the center position of the circle in the close-packed pattern E of the circles arranged adjacently or at equal intervals. I have. This close-packing pattern of a circle corresponds to a plan view in a case where the sphere is closest-packed by one step on a plane. And
The squares are straight lines a to 3 connecting the center points of this circle.
The two sides of the square are parallel to the straight line a in one direction of c, and the other two straight lines b and c are arranged so as to intersect. FIG. 1B is an explanatory diagram of an arrangement of a cell pattern C formed on a plate surface and a print dot pattern D formed on a printing sheet. When the plate surface on which the resist pattern R is formed as shown in FIG. 1A is corroded, the portion immediately below the non-resist portion 2 is corroded to form a concave portion, and the side etching phenomenon particularly proceeds near the center of the square. , A cell pattern C as shown in FIG. The center point 6 of the cell pattern C coincides with the center point 5 of the circle and the center point 5 of the square. Further, the printing dot pattern D on the gravure printing sheet printed with the gravure printing plate having such a cell pattern C has substantially the same shape although there is some deformation, and can be shown in the same drawing. FIG.
In (a), the square of the resist pattern R is drawn so as to be inscribed in the circle that regulates the position described above.
Actually, it may be larger than the circle. In that case,
The four sides of the square, which is the non-resist part 2, are eroded by the side etching at the time of corrosion and spread outward. However, since it is necessary to leave the minimum bank part 3 between adjacent cells 4, the square of the cell 4 The actual shape often does not have a circular shape as shown in FIG. 1B, but has a shape in which four sides bulge outward. This shape is the same for the actual shape of the print dot pattern D. Thus, FIG.
In the case of a cell pattern in which a square shape is still left unlike the perfect circle in (b), as is clear from the square arrangement in FIG. Often, moire can be effectively prevented in multicolor printing.

Here, when comparing the cell pattern C shown in FIG. 1B of the gravure printing plate according to the present invention with the conventional cell pattern C ′ shown in FIG. 3B, the area ratio occupied by the cells 4 is as follows. 78.5% of the conventional cell pattern C ′ (however,
The cell pattern C of the present invention is up to 90.7% (however, the theoretical value when the bank width is asymptotically approaching 0), which is 12.2% higher than the theoretical value when the bank width is asymptotically approaching 0. It becomes clear that there is. Further, when the plate depth of the cell 4 of the gravure printing plate according to the present invention is slightly reduced as compared with the conventional case and the volume of the cell 4 is adjusted to be the same, the density of the individual print dots in the shadow portion is reduced. The gravure printing sheet according to the invention drops, but the aggregate reflection density (the overall reflection density of a plurality of printing dots entering the aperture of the densitometer, which is close to the visual density) increases in reverse. This indicates that increasing the concealed area ratio of the printing sheet with ink is more effective in increasing the overall reflection density than increasing the ink density. This is clear from the next test.

FIG. 2 is an explanatory diagram of a test on the concealed area ratio of the ink on the gravure printing sheet on the aggregate density. The test was performed using a gravure printing plate in which cells of an offset halftone array of 175 lines / inch as shown in FIG. 2 were formed on the plate surface. First, as shown in Case A, printed dots d1 (Munsell 2.7YR / 3. 4 / 2.0) on the printing paper twice so as to overlap, and as shown in Case B, the printing portion where the density of the overlapping printing dots is Munsell 2.3YR / 2.1 / 1.8. , Printing dots d2 (Munsell 2.7YR / 3.4 / 2.0) and d3 (same as left) were printed twice on printing paper so that they did not overlap, and the printed area with an increased concealed area ratio was compared. In the case B, the collective concentration was 0.55 in contrast to the collective concentration of 0.38 in A. The densitometer used was a Color Reflectometer 408, manufactured by Nihon Planographic Equipment Co., Ltd.

Therefore, by using the gravure printing plate according to the present invention, it is possible to increase the printing density from the halftone to the shadow portion without increasing the conventional ink amount, and if the conventional density is sufficient, the ink density can be improved. The amount used can be reduced, and the manufacturing cost can be reduced.

In the plate making of a gravure printing plate according to the present invention, an original image is photoelectrically converted and input by an input scanner in advance, and digitized image data is displayed on a display screen of a layout scanner of a computer image processing system. Once the image is corrected and endlessly corrected (in the case of wood pattern), it is modulated by a laser beam from an output scanner or a dot generator of an imagesetter according to a program incorporated in advance, directly on the resist photosensitive layer, or on a plate making film. And a resist pattern R as shown in FIG. 1A is formed on the shadow portion of the plate surface. The resist pattern R in which the squares are arranged is ON.
This is a mosaic digital pattern formed by a laser beam that is controlled to be / OFF, and the diameter of the laser beam of several μm constitutes the minimum unit of the mosaic pattern. From the halftone to the highlight portion, the square of the resist pattern becomes smaller in accordance with the gradation density of the original image. For this purpose, it is necessary that a conversion program from the gradation density% of the original image to the number of mosaic blocks be prepared in advance. When these resist pattern surfaces are corroded in the same manner as a conventional direct gravure printing plate, a cell 4 as shown in FIG. 1B is formed.
In this case, the cell shape can be changed in a certain range by changing the corrosion conditions. Generally, in plate making of gravure printing plates, a copper ballad plating layer is formed by a second chloride process.
Corrosion is performed using a corrosive solution such as an aqueous solution of iron or cupric chloride to contact the copper plating layer. The corrosive solution having a higher specific gravity has a higher corrosive ability and intensifies side etching. Further, when the etchant is perpendicularly sprayed on the plate surface, side etching can be reduced. Therefore, the shape and cross-sectional shape of the cell 4 can be changed by selecting such corrosion conditions. The cell pattern according to the present invention can be applied to a gravure printing plate having various patterns such as a wood pattern, a stone pattern, a cloth pattern, an abstract pattern, and a solid front face.

[0010]

EXAMPLE A gravure printing plate and a printing sheet according to the present invention were applied to a cedar wood grain pattern having a heavy shadow portion. First, a film original image of the wood pattern of the cedar pattern is input to a computer using an input scanner, digitized, and partially corrected and endlessly corrected using application software. Using a plate making device (manufactured by Synch Laboratories), the dot / generator directly scans the positive photosensitive resist film applied to the plate cylinder surface with a laser beam whose ON / OFF has been modulated by a computer, and the density / A square resist pattern was formed according to a mosaic block number conversion program. Number of screen lines in that case (number of dots per unit length)
Was 143 pieces / inch. The diameter of the laser beam used for output was 5 μm. Next, corrosion was performed by a shower method using an aqueous ferric chloride solution having a specific gravity of 170 Baume. As a result, a printing plate according to the present invention was obtained in which substantially circular cells as shown in FIG. 1B were arranged in a close-packed state in the shadow portion, and the shadow portion plate depth was 30 μm. Next, using the gravure printing plate of the present invention prepared as described above, gravure printing was performed under the following conditions. Printing lot: 10,000 m Printing speed: 60 m / min Printing ink color: light brown Ink viscosity: 12 to 15 seconds [Zahn cup # 4] Printing sheet: vinyl chloride sheet Shadow area density: 1.7 The obtained gravure printing sheet according to the present invention has the same number of screen lines and a plate depth of the shadow portion of 3
As a result of comparison with a conventional direct gravure printing plate of 0 μm, the shadow portion was strong and a printed pattern with a sense of volume was obtained. Nevertheless, the amount of printing ink used does not increase, but rather can be reduced, and the drying time during printing can be reduced, enabling higher-speed printing than before, and increasing printing efficiency. It was confirmed that it was possible.

[0011]

According to the present invention, in the shadow portion,
It has a close-packed cell pattern C as shown in FIG. 1B obtained by corrosion from a resist pattern in which squares as shown in FIG. 1A are arranged, and has a conventional cell depth. By performing gravure printing using a gravure printing plate that is slightly shallower than that of the gravure printing plate and has approximately the same cell volume, it is possible to use darker shadows Can be printed. If the printing density is adjusted to the same as the printing density of the conventional shadow portion, more printing lots can be printed with the same amount of ink, and the printing speed can be increased.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating the principle of forming a cell pattern C in a gravure printing plate and a printing dot pattern D in a gravure printing sheet according to the present invention.

FIG. 2 is an explanatory diagram of a test that affects an concealed area ratio of an ink on an aggregate density in a gravure printing sheet.

FIG. 3 is a correlation diagram of a resist pattern R, a cell pattern C, and a printed dot pattern D in a conventional direct gravure.

FIG. 4 is an explanatory diagram of a known resist pattern R ″, cell pattern C ″, and print dot pattern D ″

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Resist part 2 Non-resist part 3 Bank (non-image part) 4 Cell (image part) 5 Center point of square and circle 6 Center point of cell R Resist pattern in gravure printing plate according to the present invention C Gravure printing according to the present invention Cell pattern D on plate D Print dot pattern on gravure printing sheet according to the present invention E Fine filling pattern R ', R "Resist pattern C', C" on conventional gravure printing plate Cell pattern D ', D "on conventional gravure printing plate Print dot pattern d1 to d3 print dot on conventional gravure print sheet

Claims (2)

[Claims] 1. In a direct gravure printing plate wherein cells are formed by corroding non-resist portions of a resist pattern surface on a plate surface, the non-resist portions of the resist pattern are arranged in a square array, and the center position of the square is ,
One circle and six circles of the same diameter surrounding the circumference are arranged so as to coincide with the center positions of the circles in the densely packed pattern arranged so as to be adjacent to each other, and connect the center points of the circles. A gravure printing plate, characterized in that two sides of the square are parallel to a straight line in one direction among straight lines in three directions, and intersect with straight lines in the other two directions. 2. A gravure printing sheet comprising a collection of circular printing dot patterns in a densely packed arrangement.