JP4689034B2 - Printing device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to printing apparatus that can be suitably used in the relief printing such as flexographic printing.
[0002]
[Prior art]
FIG. 7 is a diagram showing a relief printing plate used for relief printing.
2. Description of the Related Art Conventionally, relief printing using a relief printing plate 10 that adheres ink T to a convex image portion 11 and presses and transfers it to a printing substrate has been widely used.
A representative example of such relief printing is flexographic printing. The material of the printing plate used for flexographic printing is currently generally a photosensitive resin.
[0003]
FIG. 8 is a diagram showing a general form of a flexographic printing apparatus, and FIG. 9 is an enlarged view of an image line portion of a flexographic printing plate when ink is attached.
The flexographic printing apparatus 50 includes an ink tank 51, a fountain roller 52, an anilox roller 53, a plate cylinder 54, and an impression cylinder 55, and the plate cylinder 54 mounts the flexographic printing plate 10.
The ink T stored in the ink tank 51 is pulled up by the fountain roller 52 immersed in the ink tank 51 and supplied to the flexographic printing plate 10 mounted on the plate cylinder 54 via the anilox roller 53. The plate cylinder 54 is pressed against the impression cylinder 55 with a predetermined pressure, and printing is performed with a printing substrate P such as a film sandwiched between the impression cylinder 55.
On the entire surface of the anilox roller 53, grids of fine depressions such as a lattice type (cube) and a pyramid type (square pyramid) called anilox eyes 53a are formed. The anilox roller 53 receives the ink T from the fountain roller 52 to the anilox eye 53 a and supplies the ink T to the flexographic printing plate 10.
At this time, the ink T collected in the anilox eye 53a becomes a constant amount determined by the number of anilox eyes (number of lines), the depth, and the like (FIG. 9A). Then, after contacting the image line portion 11 of the flexographic printing plate (FIG. 9B), when separated, the amount of ink T adhering to the image line portion 11 becomes a certain amount (FIG. 9C).
By adopting such a structure, the supplied ink T can be quantified and made uniform with a simple mechanism.
[0004]
[Problems to be solved by the invention]
FIG. 10 is an enlarged view of an image line portion of a flexographic printing plate at the time of printing, and FIG. 11 is a diagram illustrating a problem of a conventional flexographic printing plate.
In the conventional flexographic printing, the ink T of the image line portion 11 is pressed and transferred to the printing substrate P. Therefore, the printing substrate P is pressed against the image line portion 11 to which the ink T is adhered (FIG. 10A). When printing is performed, the ink T is crushed by the press and spreads around the image area (FIG. 10B). As described above, the fact that the area of the printing halftone dot becomes larger than the area of the halftone dot of the printing plate due to the printing pressure is referred to as dot gain. However, if the dot gain increases, good print reproduction cannot be obtained.
For example, as shown in FIG. 11A, even when printing is performed with a halftone dot area ratio of 50%, the ink T may spread as shown in FIG. 11B and the adjacent halftone dots may be connected. The gradation reproducibility may be deteriorated, for example, the image may appear to fly.
[0005]
An object of the present invention reduces the dot gain is to provide a printing apparatus that to prevent tone reproduction deterioration.
[0006]
[Means for Solving the Problems]
The present invention solves the above problems by the following means. In addition, in order to make an understanding easy, although the code | symbol corresponding to embodiment of this invention is attached | subjected and demonstrated, it is not limited to this .
[0012]
In order to solve the above-mentioned problems, the invention of claim 1 is characterized in that a relief printing plate (10) for printing by attaching ink to a convex image portion (11 ) and the relief printing plate (10) on the outer periphery. A plate cylinder to be mounted; and a supply means (53) having an ink holding portion (53a) for supplying ink to the image line portion (11) of the relief printing plate (10), the relief printing plate (10) Is a substantially hemisphere in which the shape of the opening formed in a part of the image line portion is a substantially circular shape as a surplus ink reduction portion that reduces the excess ink spreading around the image line portion (11) during printing. And the supply means has a substantially square or substantially square pyramid-shaped depression in the shape of the opening as the ink holding portion on the entire outer peripheral surface thereof. An anilox roller (53) having (53a), the relief printing plate Diameter of the opening of the recess (12) of 10) is a printing apparatus, wherein the maximum dimension larger than the opening of the grid (53a).
A second aspect of the present invention is the printing apparatus according to the first aspect, wherein the concave portion (12) is formed in the vicinity of the center of the image line portion.
Invention of Claim 3 is a printing apparatus of Claim 1 or Claim 2 , Comprising: The said anilox roller (53) and the said relief printing plate (10) contact, The said relief printing plate (10) When supplying ink to the cross section perpendicular to the contact surface between the anilox roller (53) and the relief printing plate (10), the open end of the recess (12) is the inner side of the grid (53a). It is formed so that it may not be located in a printing apparatus.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in more detail with reference to the drawings.
FIG. 1 is an enlarged perspective view of one image line portion of a flexographic printing plate according to the present invention.
In addition, the same code | symbol is attached | subjected to the part which fulfill | performs the function similar to the prior art example mentioned above, and the overlapping description is abbreviate | omitted suitably.
The flexographic printing plate 10 according to the present invention forms minute depressions 12 on the surface of the image area 11 to which ink is attached.
[0014]
The flexographic printing plate 10 can be made, for example, by the following method.
(1) Plate making method in ordinary photosensitive resin plate Masking is carried out with a film reproduced by a halftone dot having a normal non-image-line forming portion at the center portion using a normal photosensitive resin material as a plate material (masking step).
Even if this film exposes the image area and shields the non-image area in the central portion to form the halftone dots of the relief printing plate, it shields the image area and blocks the image in the central area. The non-image portion may be exposed to form a halftone dot of the relief printing plate, and may be properly used depending on the subsequent plate making process.
And plate-making is performed through a normal exposure process, a development process, and a drying process, and the resin-made flexographic printing plate 10 which has the hollow 12 in the center of the image part 11 is made.
[0015]
(2) The first plate making method CTP (Computer To Plate) in the CTP flexographic printing plate is a method for making a plate by directly drawing a mask layer on a plate material with a laser without using a film. In this case, the CTP flexographic printing plate material is irradiated with a laser to draw a mask layer having a minute non-image forming portion in the central portion (masking step).
This mask layer also exposes the image area, shields the non-image area in the central portion, and forms the halftone dots of the relief printing plate. The non-image portion may be exposed to form a halftone dot of the relief printing plate, and may be properly used depending on the subsequent plate making process.
And plate-making is performed through a normal exposure process, a development process, and a drying process, and the flexographic printing plate 10 which has the hollow 12 in the center of the image part 11 is made.
[0016]
(3) The second plate-making method in the CTP flexographic printing plate, the mask output of the CTP flexographic printing plate is changed, the laser output is changed to adjust the mask layer removal amount in the center of the image area, and the light in the subsequent exposure process Reduce the amount of permeation. And plate-making is performed through a normal exposure process, a development process, and a drying process, and the flexographic printing plate which has a hollow in the center of an image part is made.
By doing in this way, since the thickness of a mask layer can be adjusted, the depth of the hollow 12 in the center of an image part can be adjusted.
[0017]
FIG. 2 is an enlarged view of an image line portion of a flexographic printing plate when ink is attached, and FIG. 3 is an enlarged view of an image line portion of the flexographic printing plate at the time of printing.
The flexographic printing plate is printed as follows using a general printing apparatus.
That is, a certain amount of ink T is accumulated in the anilox 53a (FIG. 2A), but after contacting the image line portion 11 of the flexographic printing plate (FIG. 2B), separating the image line The ink T adheres to the portion 11 other than the recess of the portion, and the ink T does not adhere to the recess 12 (FIG. 2C).
In this way, when the printing substrate P is pressed and printed with the ink T attached (FIG. 3A), the ink T spreads due to the pressing, and the excess ink enters the depression 12 in the image area. The spread around the image line portion is reduced (FIG. 3B).
[0018]
Note that if the size of the depression 12 formed in the image line portion is smaller than the size of the anilox eye 53a, the ink T supplied from the anilox eye 53a may be blocked across the depression 12; The size of 12 is preferably larger than the size of the anilox 53a.
[0019]
According to the present embodiment, by providing the depression 12 in the image line portion 11, it is possible to reduce the dot gain at the time of transfer, and thereby the following effects can be obtained. In addition, if the depression 12 is provided in the vicinity of the center of the image line portion 11 as in the present embodiment, the spread of the ink T can be uniformly reduced as a whole, and thus the effect is particularly great.
[0020]
(1) Improvement of gradation property FIG. 4 is a diagram for comparing the gradation properties of the prior art and the present embodiment. The horizontal axis represents the dot area ratio and the vertical axis represents the print density.
As shown in FIG. 4, in the present embodiment, the change in the print density when the halftone dot area ratio is changed is small. For this reason, it is possible to reproduce gradation smoothly compared to conventional flexographic printing.
In this way, by reducing the dot gain, the ink can be transferred to a halftone dot size that is faithful to the size of the print line portion, and the gradation can be reproduced smoothly.
[0021]
(2) Improved highlight reproducibility (enlargement of reproducible concentration range)
FIG. 5 is a diagram for comparing the highlight reproducibility of the prior art and the present embodiment, and is an enlarged view of the printed matter highlight.
As shown in FIG. 5, the halftone dots are conventionally thick due to the dot gain (FIG. 5A), but in this embodiment, an accurate halftone dot with a small dot gain can be reproduced (FIG. 5B )). For this reason, the minimum reproducible density can be kept low as compared with the conventional flexographic printing.
Thus, by reducing the dot gain, a finer halftone dot can be reproduced, the minimum density can be lowered, and the reproducible density range can be expanded.
[0022]
(3) Resolution Improvement FIG. 6 is a diagram for comparing the resolution of the conventional printing and the present embodiment, and is an enlarged view of a printed thin line.
As shown in FIG. 6, conventionally, thin line wobbling has occurred due to dot gain (FIG. 6A), but in this embodiment, such wobbling can be prevented (FIG. 6B). ).
Thus, by reducing the dot gain, it is possible to improve (removal) fine line reproducibility, and to prevent, for example, characters such as “hawk” and “rose” that are densely lined. it can.
[0023]
(Deformation)
The present invention is not limited to the embodiment described above, and various modifications and changes are possible, and these are also within the equivalent scope of the present invention.
For example, the relief printing plate 10 according to the present invention is characterized in that the depression 12 is formed in the image line portion 11 to which the ink T is adhered, and is not limited to the shape and number of the depressions 12 and the plate making method. .
In the above-described embodiment, the depression 12 is provided in the center of the image line unit 11. However, the present invention is not limited to this, and if provided in any part of the image line unit 11, the dot gain can be similarly reduced. It is.
Furthermore, in the above embodiment, flexographic printing has been described as an example of letterpress printing. However, other letterpress printing can be implemented in the same manner.
[0024]
【The invention's effect】
As described above in detail, according to the present invention, the dot gain can be reduced because the surplus ink reducing unit that reduces the surplus ink spreading around the image line portion is provided during printing.
[0025]
According to the present invention, the surplus ink reducing portion is a concave portion formed in a part of the image line portion, and therefore can be easily formed.
[0026]
According to the present invention, the concave portion can reduce the spread of the surplus ink formed near the center of the image portion evenly.
[0027]
According to the present invention, since the opening diameter of the concave portion is larger than the opening diameter of the ink holding portion included in the ink supply means for supplying ink to the image line portion, it is possible to reliably reduce excess ink.
[0028]
According to the present invention, the image forming area of the photosensitive resin plate material is masked with the mask film, so that the plate can be easily made.
[0029]
According to the present invention, since the mask layer is formed by irradiating a laser, the plate can be made in a short time.
[0030]
According to the present invention, since the thickness of the mask layer is adjusted by changing the laser output to be irradiated, the depth of the concave portion of the image line portion can be adjusted.
[Brief description of the drawings]
FIG. 1 is an enlarged perspective view of one of image line portions of a flexographic printing plate according to the present invention.
FIG. 2 is an enlarged view of an image line portion of a flexographic printing plate when ink is attached.
FIG. 3 is an enlarged view of an image line portion of a flexographic printing plate during printing.
FIG. 4 is a diagram for comparing the gradation of the prior art and the present embodiment.
FIG. 5 is a diagram comparing highlight reproducibility between the prior art and the present embodiment.
FIG. 6 is a diagram comparing the resolution of conventional printing and this embodiment.
FIG. 7 is a diagram showing a relief printing plate used for relief printing.
FIG. 8 is a diagram showing a general form of a flexographic printing apparatus.
FIG. 9 is an enlarged view of an image line portion of a flexographic printing plate when ink is attached.
FIG. 10 is an enlarged view of an image line portion of a flexographic printing plate during printing.
FIG. 11 is a diagram showing a problem of a conventional flexographic printing plate.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 Flexographic printing plate 11 Image line part 12 Indentation 50 Flexographic printing apparatus 51 Ink tank 52 Fountain roller 53 Anilox roller 53a Anilox eye 54 Plate cylinder 55 Impression cylinder P Printing base material T Ink

Claims (3)

A relief printing plate for printing by attaching ink to the convex image area ;
A plate cylinder for mounting the relief printing plate on the outer periphery;
A supply means having an ink holding part for supplying ink to the image line part of the relief printing plate,
The relief printing plate has an approximately circular shape in the shape of an opening formed in a part of the image line portion as a surplus ink reduction portion that reduces the excess ink spreading around the image line portion during printing. Having a hemispherical recess,
The supply means is an anilox roller having a substantially square or substantially quadrangular pyramid shaped square as the ink holding portion on the entire outer peripheral surface of the opening ,
The printing apparatus , wherein a diameter of the opening of the concave portion of the relief printing plate is larger than a maximum dimension of the opening of the grid. The printing apparatus according to claim 1,
The printing apparatus is characterized in that the concave portion is formed in the vicinity of the center of the image line portion . The printing apparatus according to claim 1 or 2 , wherein
When the ink is supplied to the relief printing plate when the anilox roller is in contact with the relief printing plate,
The printing apparatus is characterized in that, in a cross section perpendicular to the contact surface between the anilox roller and the relief printing plate, the open end of the recess is formed so as not to be located inside the grid.

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