JP2008230195A - Letterpress, manufacturing process of letterpress, and printing apparatus of can - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a letterpress, a manufacturing process of the letterpress and the printing apparatus of the can using this letterpress that can control the dot gain of the points printed by the projection of the letterpress to be smaller and can attain the high resolution printing. <P>SOLUTION: The invention refers to the letterpress 30 mounted on the periphery of the plate cylinder to be used in the printing apparatus of the can having a round columnar plate cylinder and the blanket to which an ink applied on this plate cylinder is to be transferred, and is characterized in that, with this letterpress 30 being mounted on the periphery of the plate cylinder, a solid section 31 located at the most radially outward part, the bottom foundation section 33 recessed radially inward from this solid section 31 and the dot section 32 containing the projection 34 having an approximate figure of the frustum of cone projecting radially outward from this bottom foundation section 33 are formed, and in that the radial distance H1 between the solid section 31 and the top section 34A of the projection 34 is set within the range of 0 μm<H1≤80 μm. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention provides a relief printing plate used in a printing apparatus for a can having a cylindrical plate cylinder and a blanket to which ink applied to the printing drum is transferred, a method for producing the relief printing plate, and the relief printing plate. The present invention relates to a can printing apparatus.

  A two-piece can used as a container for soft drinks, etc. consists of a can lid and a cylindrical can body, and the can body is printed on the outer surface after DI (deep drawing, ironing) processing and washing. Is given. In printing the can body, a printing apparatus having an offset printing mechanism as shown in Patent Document 1 or Patent Document 2 is used.

Such a printing apparatus includes a plate cylinder having a cylindrical outer shape and a relief plate disposed on the outer peripheral surface thereof, and a rubber blanket that is in sliding contact with the outer peripheral surface of the plate cylinder. Is applied, the ink is transferred to a blanket, and the blanket is slidably contacted with the outer peripheral surface of the can body, thereby printing on the outer peripheral surface of the can body.
JP 2001-129966 A JP 2006-272682 A

  By the way, in the conventional can printing apparatus described in Patent Document 1 and Patent Document 2, the relief plate disposed on the outer peripheral surface of the plate cylinder is formed by exposure and development processing (etching processing). In the relief plate formed in this manner, in a state where it is disposed on the outer peripheral surface of the plate cylinder, a solid portion located radially outward of the plate cylinder, a base portion recessed radially inward by etching, and A halftone dot portion having a plurality of protruding portions protruding from the base portion is formed, and the radial position of the top portion of the protruding portion is the same as the solid portion.

  When such a relief plate is pressed against the blanket, the top of the protrusion is crushed by the pressure and simultaneously sunk into the blanket, so that the phenomenon that dots (dots) to be printed become thick, so-called dot gain increases. Therefore, there is a problem that dots (dots) cannot be printed with high accuracy. In addition, when the halftone dot (projection) is formed by exposure and development processing, if the area of the top of the projection is reduced, the cured state of the projection after etching will vary and the point of less than 50 μm cannot be reproduced sufficiently. There is a problem that the protrusions cannot be formed close to each other, and only printing with a low resolution of about 120 lines / inch can be performed.

  The present invention has been made in view of the above-described circumstances, and is a relief plate capable of printing with high resolution while suppressing dot gain at a point printed by the projection portion of the relief plate, a method for producing the relief plate, and the relief plate. An object of the present invention is to provide a printing apparatus for cans using the above.

  In order to solve the above-mentioned problems, a relief printing plate according to the present invention is used in a printing apparatus for a can provided with a cylindrical plate cylinder and a blanket to which ink applied to the plate cylinder is transferred. A relief printing plate disposed on the outer peripheral surface of the cylinder, and in a state of being disposed on the outer peripheral surface of the plate cylinder, a solid portion positioned most radially outward, and from the solid portion toward the radially inner side And a halftone dot portion having a substantially frustum-shaped projection protruding outward in the radial direction from the base, and a radial direction between the solid portion and the top of the projection The distance H1 is set in the range of 0 μm <H1 ≦ 80 μm.

  According to the relief plate of this configuration, in the state of being disposed on the outer peripheral surface of the plate cylinder, the solid portion located on the outermost radial direction of the plate cylinder and the protruding portion projecting radially outward from the base portion Since the radial distance H1 from the top of the plate is H1> 0 μm and the top of the projection is retracted radially inward from the solid portion, the projection is greatly crushed when the relief plate is pressed against the blanket. No deformation occurs and the dot gain can be kept small. Therefore, printing with high resolution can be performed. On the other hand, since the radial distance H1 between the solid portion and the top portion of the projection portion is set to H1 ≦ 80 μm, it is possible to prevent the top portion of the projection portion from reliably contacting the blanket.

Here, in the state of being disposed on the outer peripheral surface of the plate cylinder, the protrusion height H2 of the protrusion from the base portion may be set within a range of 90 μm ≦ H2 ≦ 700 μm.
In this case, since the protrusion height H2 of the protrusion from the base is H2 ≧ 90 μm, the occurrence of clogging due to ink can be suppressed, and the printing operation can be performed continuously for a long time. In particular, ink for printing metal cans is effective because of its high viscosity and easy clogging. Further, since the protrusion height H2 of the protrusion from the base is H2 ≦ 700 μm, it becomes possible to ensure the rigidity of the protrusion and perform printing well.
Furthermore, since clogging can be prevented even if the interval between the protrusions is reduced, the interval between printed points can be reduced to 0.145 mm (175 lines) and 0.163 mm (156 lines). In that case, it becomes possible to express a valley portion between dots at a dot density of 175 line-87%.

The method for producing a relief plate according to the present invention is the method for producing a relief plate described above, wherein the halftone dot portion is formed by irradiating the plate material with a laser to burn the surface of the plate material. .
According to the method of manufacturing a relief plate having this configuration, the halftone dot portions (base portion and projection portion) are formed by burning the plate material with a laser, so that the projection portion can be formed with high accuracy. As a result, the lower limit of the size of dots (dots) printed by the protrusions can be greatly improved from the conventional 50 μm to 10 μm. That is, a point of 10 μm to 50 μm that could not be expressed conventionally can be reproduced. Here, the size of a point (dot) is the diameter of a circle or polygonal inscribed circle formed by the outline of the point.

Further, a printing apparatus for a can according to the present invention comprises a plate cylinder having a cylindrical shape and a blanket to which ink applied to the plate cylinder is transferred, and the above-described relief printing plate is disposed on the outer peripheral surface of the plate cylinder. It is characterized by having.
According to the printing apparatus for a can having this configuration, it is possible to perform printing with high resolution on the outer peripheral surface of the can, for example, photographic printing, and the design of the can can be greatly improved.

  According to the present invention, it is possible to provide a relief printing plate capable of reducing the dot gain of the dots printed by the projections of the relief printing and printing with high resolution, a method for producing the relief printing plate, and a can printing apparatus using the relief printing plate. Can do.

Embodiments of the present invention will be described below with reference to the accompanying drawings. An outline of a printing apparatus for cans using a relief printing plate according to the present embodiment is shown in FIG.
The printing apparatus A for cans is schematically configured by a plurality of ink adhering mechanisms B and can moving mechanisms C.

The ink adhering mechanism B includes an inker unit 1 that supplies ink, and a blanket 9 that contacts the outer surface of the can body 20 and prints (adheres) the ink after contacting the inker unit 1 and copying the ink. And a blanket wheel 8 having a plurality of sheets.
The inker unit 1 includes an ink source 2, a ducting roll 3 that contacts the ink source 2 and receives ink, an intermediate roller 4 that is connected to the ducting roll 3 and includes a plurality of rollers, and the intermediate roller 4 A rubber plate 5 to be connected and a plate cylinder 6 to be connected to the rubber roller 5 are provided. On the outer peripheral surface of the plate cylinder 6, a relief plate 30 formed in the same shape as the pattern to be transferred to the can cylinder 20 is disposed. The plate cylinder 6 is rotatably supported on the shaft portion of the printing apparatus A.
A plurality of blankets 9 are provided on the outer peripheral surface of the blanket wheel 8, and the blanket 9 is in contact with the relief plate 30 disposed on the outer peripheral surface of the plate cylinder 6 and in contact with the can cylinder 20. Has been.

  The can moving mechanism C sequentially includes a can shooter 10 for taking in the can body 20, a mandrel 11 for rotatably holding the can body 20 supplied from the can shooter 10, and a can body 20 attached to the mandrel 11. The mandrel turret 12 is configured to rotate and move in the direction of the ink adhesion mechanism B.

  As shown in FIG. 2, the plate cylinder 6 includes a cylindrical sleeve 36 and a cylinder body 37 fitted on the inner peripheral side of the sleeve 36. The sleeve 36 is made of plastic resin, and the inner diameter and outer diameter thereof are substantially constant in the axial direction of the cylinder formed by the sleeve 36. A relief plate 30 having a predetermined pattern is disposed on the outer peripheral surface of the sleeve 36.

FIG. 4 shows a schematic sectional view of the relief plate 30. The relief plate 30 is formed by irradiating the surface of a plate material 38 attached to the outer peripheral side of the sleeve 36 with a laser, and a solid portion 31 that is not subjected to laser processing, a base portion 33 that is greatly recessed, and this And a halftone dot portion 32 having a protrusion 34 erected from the base portion 33.
The laser processing conditions are preferably, for example, a CO2 laser with a wavelength of 2.5 to 11 μm and an output of 100 to 500 W. In this embodiment, the wavelength is 10.6 μm and the output is 200 W, and the rotational speed of the plate material 38 is 520 rpm. It was.

In such a relief plate 30, the solid portion 31 is positioned on the outermost radial direction of the sleeve 36 and the base portion 33 is positioned on the innermost radial direction of the sleeve 36 in a state of being disposed on the outer peripheral surface of the sleeve 36. Will do. Here, the radial distance H1 between the solid portion 31 and the apex 34A of the projection 34 is set in a range of 0 μm <H1 ≦ 80 μm. That is, the top portion 34 </ b> A of the protruding portion 34 is retracted radially inward from the solid portion 31.
The protrusion height H2 of the protrusion 34 from the base portion 33 is set in the range of 90 μm ≦ H2 ≦ 700 μm.

  In the can printing apparatus A provided with the relief plate 30 having such a configuration, inks of different colors from the ink source 2 of each inker unit 1 cause the ducting roll 3, the intermediate roller 4, and the rubber roller 5 to pass through. The ink of each color is put on the blanket 9 on the rotating blanket wheel 8 as a pattern, and this pattern is held on the mandrel 11. Printing is performed while contacting the can body 20.

  According to the relief plate 30 according to the present embodiment, the radial distance H1 between the solid portion 31 located on the outermost surface in the radial direction and the top portion 34A of the projection 34 in the state of being disposed on the outer peripheral surface of the plate cylinder 6 is. Since H1> 0 μm, the top 34A of the projection 34 is retracted radially inward from the solid portion 31, so that the projection 34 is largely crushed even if the relief plate 30 is pressed against the blanket 9. The dot gain at the point printed by the protrusion 34 can be kept small without being deformed. Further, in normal manufacturing, the amount of pressing (pressing) of the relief plate 30 into the blanket 9 is manufactured at a maximum of about 90 μm. Here, in this embodiment, since the radial distance H1 between the solid portion 31 and the top portion 34A of the projection portion 34 is H1 ≦ 80 μm, the projection portion 34 can be reliably brought into contact with the blanket 9. Can be printed reliably.

  Further, in the state of being arranged on the outer peripheral surface of the plate cylinder 6, since the protrusion height H2 of the protrusion 34 from the base portion 33 is H2 ≧ 90 μm, the occurrence of clogging due to ink can be suppressed. , Printing work can be performed continuously for a long time. Further, since the protrusion height H2 is set to H2 ≦ 700 μm, the rigidity of the protrusion 34 can be ensured and printing can be performed satisfactorily.

  Further, since the halftone dot portion 32 (the base portion 33 and the protruding portion 34) is formed by irradiating the plate material 38 with a laser and burning the surface of the plate material 38, the protruding portion 34 is formed with high accuracy. be able to. Thereby, the size of the dot printed by the projection part 34 can be made small, and the dot of 10 micrometers-50 micrometers which could not be expressed conventionally can be printed.

Further, since the relief plate 30 can be formed with the plate material 38 attached to the outer peripheral surface of the plate cylinder 6 (sleeve 36), the operation of pasting the relief plate 30 becomes unnecessary, and operations such as registration are omitted. Can do.
In addition, since the relief plate 30 is disposed on the plastic resin sleeve 36, when changing the pattern printed on the can body 20, only the very light sleeve 36 needs to be replaced. The time and labor required can be greatly reduced.

As mentioned above, although embodiment of this invention was described, this invention is not limited to this, It can change suitably in the range which does not deviate from the technical idea of the invention.
For example, the plate material attached to the outer peripheral surface of the cylindrical sleeve constituting the plate cylinder has been described as forming a relief plate directly by laser processing, but the present invention is not limited to this, and a plate-like plate material is used. A relief plate may be formed by laser processing, and this may be attached to the outer peripheral surface of the plate cylinder.

In addition, the plate cylinder composed of the sleeve and the cylinder main body has been described, but the present invention is not limited to this, and a structure may be used in which the sleeve is not provided and a relief plate is attached to the outer peripheral surface of the cylinder main body.
Furthermore, the laser processing conditions are not limited to the present embodiment, and are preferably set as appropriate in consideration of the material of the plate material, the shape of the halftone dots to be formed, and the like.

Below, the confirmation test result performed in order to confirm the effect of this invention is demonstrated.
Comparative Example 1 is a relief printing plate formed by a conventional exposure and development method. Comparative Example 2 is a relief printing plate formed by laser exposure + development processing. Comparative Example 3 and Examples 1 to 11 are relief plates having a halftone dot formed by laser processing. Here, in Comparative Example 3, the radial distance H1 between the solid portion and the top portion of the protruding portion is outside the scope of claim 1 of the present invention.
The evaluated relief data was 0 to 100% flat halftone dot data of 175 lines, 156 lines, and 133 lines.

Using these letterpress plates, metal cans were printed, and dot gain, dot reproducibility (including whether dots were printed), and ink clogging after printing 10,000 cans were evaluated.
The dot gain was measured using a halftone dot meter (CC5) manufactured by Centurfax. The dot gain G is calculated by G = B−A where the halftone dot density A% of the relief printing and the halftone dot density B% of the printed matter (can).
The printing conditions were a blanket hardness of 80 (Shore A), a letterpress hardness of 50 to 90 (Shore A), an ink viscosity of 15 to 75 Pa · s, and an ink deposit of 0.125 cc. In addition, the ink accumulation amount equivalent to 0.125 cc means that the color density of the color developing panel produced by injecting 0.125 cc of ink into the roll of the RI tester and printing on the aluminum plate cut out from the can body. It is the ink amount adjusted so as to be.
The evaluation results are shown in Table 1.

In Comparative Example 1 formed by the exposure development method and Comparative Example 2 formed by the laser exposure + development process, the radial distance H1 between the solid portion of the relief plate and the top of the projection is set to 0. It was confirmed that the dot gain was as large as 20% and 10%, respectively, and the printed points were thickened. In Comparative Example 2, the protrusion height H2 of the protrusion was as small as 30 μm, and ink clogging was confirmed.
On the other hand, in Comparative Example 3 in which the radial distance H1 between the solid portion and the top of the projection is 100 μm, and the top of the projection is retracted larger in the radial direction than the solid portion, the top of the projection is used as a blanket. The contact could not be made and the dots could not be printed.

On the other hand, in Examples 1 to 11, the radial distance H1 between the solid portion and the top of the protrusion is set to 5 to 80 μm, and the dot gain is reduced to 1 to 8%. In Example 2 in which the dot diameter was 10 μm, it was confirmed that halftone dots can be printed and reproduced.
In Examples 9 to 11, the protrusion height H2 of the protrusion was changed. However, in Example 11 in which H2 was 80 μm, clogging was observed. In order to prevent ink clogging, it was confirmed that the height H2 of the protrusions is preferably 90 μm or more.

It is a schematic diagram of the printing apparatus of the can in which the relief printing plate which is embodiment of this invention is used. FIG. 2 is a perspective view of a plate cylinder provided in the can printing apparatus shown in FIG. 1. FIG. 3 is an enlarged cross-sectional view of a relief plate provided in the plate cylinder shown in FIG. 2.

Explanation of symbols

6 plate cylinder 9 blanket 30 letterpress 31 solid part 32 halftone dot part 33 base part 34 protrusion 34A top part 38 plate material A printing apparatus for can

Claims (4)

A printing plate for a can having a cylindrical plate cylinder and a blanket to which ink applied to the plate cylinder is transferred, a relief plate disposed on the outer peripheral surface of the plate cylinder,
In the state of being arranged on the outer peripheral surface of the plate cylinder, a solid portion that is located most radially outward, a base portion that is recessed radially inward from the solid portion, and a radially outward direction from the base portion And a halftone dot portion having a roughly frustum-shaped protrusion protruding toward the
A relief printing plate, wherein a radial distance H1 between the solid portion and the top of the projection is set in a range of 0 μm <H1 ≦ 80 μm.   The protrusion height H2 of the protrusion from the base portion is set in a range of 90 μm ≦ H2 ≦ 700 μm in a state of being disposed on the outer peripheral surface of the plate cylinder. The letterpress described in 1. It is a manufacturing method of the letterpress of Claim 1 or Claim 2,
A method for producing a relief printing plate, wherein the halftone dot portion is formed by irradiating a plate material with a laser to burn off the surface of the plate material.   A plate cylinder having a cylindrical shape and a blanket to which ink applied to the plate cylinder is transferred, and the relief plate according to claim 1 or 2 is disposed on an outer peripheral surface of the plate cylinder. Characteristic can printing device.

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