PRINTING AND METHOD

TECHNICAL FIELD AND BACKGROUND OF THE INVENTION

[0001] The present invention relates generally to the field of engravable sleeves for gravure printing cylinders, and more particularly, to an engravable nickel sleeve including a nickel base layer and a nickel phosphorous outer layer, and a method of manufacturing the same.

[0002] Gravure printing is a well-known printing process whereby blank cylinders are engraved with an image, applied with ink and rolled onto paper or other medium to thereby transfer the engraved image to the paper. In this process, the engraved cylinder sits partially in a fountain of ink and rotates. As the cylinder rotates, paper is fed between the cylinder and an impression roll that applies a constant amount of pressure to the paper against the cylinder. A doctor blade scrapes excess ink from the cylinder and back into the fountain for reuse.

[0003] Conventional cylinders are typically made from steel and plated or sleeved with copper. The cylinder is then polished to prepare the surface for engraving. An image is then engraved onto the cylinder. Engraving may be carried out by either electro-mechanically engraving with a diamond stylus or by etching using a chemical etching agent, among other techniques. More recently, the engraving process has utilized lasers to engrave the cylinders. After the image has been engraved, the cylinder is then typically plated with chrome to increase the resistance of the printing surface against wear from the doctor blade.

[0004] The engraving process is important as cells are created to hold the ink that is transferred to the paper. The amount of ink in a cell can alter the intensity of the color transferred to the paper, and thus the dimensions and definition of the cells are critical to generating desired images: the better the definition of the cells, the more accurate the image reproduction.

[0005] The traditional process of gravure printing described in brief above contains some drawbacks. First, consumed cylinders must be disposed of. Unfortunately, because conventional cylinders include copper and chrome, they are not 100% recyclable, and chrome disposal presents environmental concerns. Second, gravure cylinders are heavy and expensive to transport. Third, the copper can tarnish and must therefore be polished before being engraved. Thus, there is a need in the art for a cylinder for use in gravure printing that is 100% recyclable, lightweight, does not require polishing, offers improved definition of engraved cells, and facilitates improved application of ink release and transfer to the paper.

BRIEF SUMMARY OF THE INVENTION

[0006] Therefore, it is an object of the present invention to provide an engravable printing sleeve that is lightweight, 100% recyclable, ready to engrave without the need for polishing, provides improved definition of engraved cells, and has improved ink transfer and ink release characteristics.

[0007] It is a further object of the invention to provide an engravable printing sleeve that can be engraved using conventional methods such as electro mechanical means or etching, as well as engraving with a laser.

[0008] It is a further object of the invention to provide an engravable printing sleeve that is free of nickel and copper.

[0009] To achieve the foregoing and other objects and advantages, provided herein is an engravable nickel sleeve including a regular base nickel layer and a nickel phosphorous outer layer. The phosphorous content of the outer layer may be from 5-10wt%. The thickness of the outer layer may be at least 50μιη, more preferably from 70-80μιη. The total thickness of the sleeve may be 305μιη.

[0010] According to another embodiment of the invention, provided herein is a method for manufacturing an engravable nickel printing sleeve. The method includes the steps of: (a) placing a mandrel in a nickel bath and plating with nickel to a predetermined thickness; (b) removing the mandrel from the nickel bath immediately upon achieving the predetermined thickness; (c) removing excess nickel from tape on the mandrel and removing nickel bands; (d) rinsing the mandrel; (e) sanding the mandrel; (f) taping a sleeve onto the mandrel; (g) cleaning and rinsing the mandrel; (h) placing the mandrel in a nickel activation bath; (i) programming the nickel activation bath for nickel adhesion; (j) starting the engravable nickel activation bath and setting for 80μιη of engravable nickel; (k) placing the activated mandrel in the engravable nickel bath; (1) removing the mandrel from the engravable nickel bath when plating is complete; (m) rinsing the sleeve; (n) checking the engravable nickel bath for nickel debris; and (o) checking the surface roughness (Rz) of nickel surface for a value less than 0.4 μηι.

[0011] Additional features, aspects and advantages of the invention will be set forth in the detailed description which follows, and in part will be readily apparent to those skilled in the art from that description or recognized by practicing the invention as described herein. It is to be understood that both the foregoing general description and the following detailed description present various embodiments of the invention, and are intended to provide an overview or framework for understanding the nature and character of the invention as it is claimed. The accompanying drawings are included to provide a further understanding of the invention, and are incorporated in and constitute a part of this specification.

BRIEF DESCRIPTION OF THE DRAWINGS

[0012] These and other features, aspects and advantages of the present invention are better understood when the following detailed description of the invention is read with reference to the accompanying drawings, in which:

[0013] FIG. 1 is a perspective view of a gravure printing process using an engravable nickel sleeve according to an embodiment of the invention;

[0014] FIG. 2 is an end view of the nickel sleeve wherein the thickness of the layers are exaggerated to illustrate the inner and outer layers; and

[0015] FIG. 3 is another perspective view of the engravable nickel sleeve.

DETAILED DESCRIPTION OF THE INVENTION

[0016] The present invention will now be described more fully hereinafter with reference to the accompanying drawings in which exemplary embodiments of the invention are shown. However, the invention may be embodied in many different forms and should not be construed as limited to the representative embodiments set forth herein. The exemplary embodiments are provided so that this disclosure will be both thorough and complete, and will fully convey the scope of the invention and enable one of ordinary skill in the art to make, use and practice the invention. Like reference numbers refer to like elements throughout the various drawings.

[0017] Referring now to the drawings, FIG. 1 shows a cylinder arrangement for gravure printing according to an embodiment of the invention. The engravable nickel sleeve according to the preferred emnbodiment of the invention is shown generally at reference numeral 10 and is shown wrapped around a base cylinder 16. The engravable nickel sleeve 10, also referred to herein as the "nickel sleeve" or "sleeve," is the printing sleeve applied to the base cylinder 16 and includes a nickel base or "inner" layer 14 and a nickel phosphorus outer or "surface" layer 12 as described below. The thickness of the nickel sleeve 10 is shown exaggerated to highlight the inner and outer layers 14, 12.

Although not shown, axle journals are typically provided in the ends of the base cylinder 16 for rotating support of the cylinder in the printing press.

[0018] The nickel sleeve 10 is rotatably supported in the printing press partially submerged in an ink fountain 32 such that the outer surface of the sleeve is loaded with ink as the sleeve rotates in the ink fountain. As the sleeve rotates, excess ink is scraped from the surface using a doctor blade 33 and returned to the ink fountain 32 for reuse. An impression roll 31 is arranged axially parallel to the sleeve 10 and in close proximity thereto such that the impression roll applies pressure to the paper 30 as the paper passes between the sleeve 10 and the roll 31 to uniformly transfers the ink to the paper. The sleeve 10 and impression roll 31 rotate in opposite directions to feed the paper through the printing press.

[0019] Referring to FIG. 2, the nickel sleeve 10 is shown applied to the base cylinder 16. The nickel sleeve 10 is firmly attached to the base cylinder 16 to prevent relative movement and angular displacement therebetween during use. The sleeve 10 includes an inner layer 14, such as a regular base nickel layer, and a nickel phosphorus outer layer 12. FIG. 3 shows a perspective view of the nickel sleeve 10, wherein the nickel phosphorous outer layer 12 has been engraved.

[0020] The phosphorus content of the outer layer 12 is preferably between 5- 14wt%. The thickness of the outer layer 12 is typically at least 50μιη, more preferably from 70-80μιη. The total thickness of the sleeve 10 may be 305μηι.

[0021] The preferred method for manufacturing the engravable nickel printing sleeve includes placing a cylinder or "mandrel" in a nickel bath and plating with nickel to a predetermined thickness, for example 228μηι. The mandrel is removed from the nickel bath as soon as possible such that the mandrel is not left sitting in the nickel bath. The mandrel is then placed in a sander. Excess nickel is then scraped from tape on the mandrel. Nickel bands are then removed. The mandrel is then rotated and rinsed, for example with water.

The sleeve is then sanded, for example using 600grit sandpaper with a 5kg weight on the handle. The sandpaper may be changed once after 10 passes, and sanded for a total of 20 passes. The sleeve is then taped onto the mandrel at both ends, for example using three layers of tape. The machine is then stopped and the sander head is removed.

[0022] The mandrel is then cleaned, for example with an industrial wipe, and the rinsed. Next, the mandrel is placed in a nickel activation bath, which is programmed for optimum nickel adhesion. The engravable nickel bath, for example SLVl, is started and setup for 80 μιη of engravable nickel. When activation is finished, the newly activated nickel is placed in the enengravable nickel bath (e.g., SLVl). Plating starts automatically, When plating in the engravable nickel bath is finished, the sleeve is rinsed, for example with water, and checked. The engravable nickel bath is checked for nickel debris. The surface roughness (Rz) of the nickel surface is checked. An exemplary acceptable reading may be less than 0.4μιη.

[0023] Preferred operating parameters are as follows:

Nickel content: 100-120g/l, preferably 114g/l pH value: 2.0-2.4, preferably 2.2

Temperature: 60-70°C, preferably 65°C

Agitation: moderate 10-40 cm/sec, preferably 20cm/sec

Current density: 5 -20 Amp/dm ² , preferably lOAmp/dm ²

Deposition rate: 50-80μπι/ηΓ, preferably 65μηι/ηΓ

Anodes: (inert) iridium oxide/platinized titanium

Phosphorus addition: proprietary additive IPT

Nickel addition: purified nickel carbonate (dry) Chloride: chloride free

Filtration: continuous multi state

Anode-cathode distance: as small as possible

[0024] The foregoing description provides embodiments of the invention by way of example only. It is envisioned that other embodiments may perform similar functions and/or achieve similar results. Any and all such equivalent embodiments and examples are within the spirit and scope of the present invention and are intended to be covered by the appended claims.