BRPI0806532B1 - ANILOX ROLLER, PRINTING APPARATUS, METHOD FOR FORMING AN ANILOX ROLLER, AND, APPARATUS FOR FORMING AN ANILOX ROLLER TO BE USED IN A PRINTING PROCESS - Google Patents

Abstract

ANILOX ROLLER, PRINTING APPARATUS, METHOD FOR FORMING AN ANILOX ROLLER, AND, APPARATUS FOR FORMING AN ANJLOX ROLLER TO BE USED IN A PRINTING PROCESS. The invention concerns an anilox roll for a printing apparatus. The anilox roll comprises a cylinder with a surface. The surface comprises a fluid distribution structure for receiving, distributing and transferring a fluid such as paint. The fluid distribution structure comprises a channel formed on the surface with channel walls. This channel is arranged to distribute the fluid entirely into the fluid distribution structure. The channel comprises channel parts, wherein the courses of the connected channel parts are at an angle with respect to each other to prevent a linear distribution of the fluids to be received in one direction of course of the channel, allowing a sinuous distribution of the fluid to be received on the channel. Channel side walls are arranged to permit a meandering flow of fluid across the entire fluid distribution surface.

Description

[001] The invention concerns an anilox roll. The invention also concerns the printing of substrates using an anilox roller. The invention further relates to a printing apparatus comprising an anilox roll. The invention also relates to the use and formation of an anilox roll.

[002] Anilox rolls have been used in flexographic methods in the printing industry. This printing method was generally used to print different substrates such as papers, labels, ribbon, (plastic) bags and boxes. Anilox rolls can be used in printing methods other than flexographic methods. Also offset and intaglio printing. An anilox roller is used in these other methods to transfer ink in precise, constant amounts.

[003] An anilox roll comprises a generally hard cylinder, with a steel or aluminum core. A thin layer of ceramic is provided on top of the core. In the thin layer, normally small ink cells, hereinafter cells, are etched. In a known embodiment, cells are formed with a hexagonal or honeycomb pattern on the surface of the anilox roll. Cells have a volume to receive ink depending on cell size and cell depth. The size of the cells on the surface of the anilox roll will determine the density of the cells. Cell density is expressed in lines per linear centimeter. The cell volume will determine the operating mode of the anilox roll. Patterns and cells on the surface of the anilox roll can be formed using a laser by performing a laser engraving method. The method may comprise a continuous or pulsed laser. The laser is directed to the surface of the anilox roll, forming a laser focus, and the laser focus will engrave a pattern on the surface. The laser intensity is sufficient to locally evaporate material from the outer layer of the anilox roll, e.g. chromium oxide. This will form a cell. A cell comprises a recess located on the surface of the roll enclosed by the cell walls. A single cell wall can be a wall for two adjacent cells, separating the cells.

[004] The anilox roll is supported by bearings in a printing device such as a flexographic device. The anilox roll comprises longitudinal cylinder ends that can be mounted on a frame of the printing apparatus. The anilox roll is releasably mounted to allow for quick cleaning and changing. The anilox roll can rotate around its longitudinal axis in a circumferential direction.

[005] The rotating anilox roller may be partially immersed in an ink source or a source roller is partially immersed in an ink source, said source roller being in contact with the anilox roller to transfer the ink to the ink roller. anilox and for cells. In operation, the printing apparatus comprising the anilox roller will operate to transfer ink to the surface of the anilox roller and the surface structure is arranged to retain the ink on and within the surface. A blade is used to scrape off excess ink from the anilox roller or ink roller. The ink will remain in the cells formed on the surface of the anilox roll.

[006] In operation, the anilox roller will rotate and the surface of the anilox roller will contact the rotating printing cylinder. The printing cylinder will receive, in an operational mode from the anilox roll, a portion of the ink collected from above or inside the surface of the anilox roll. The amount of ink transferred will depend on the image to be printed. The printing cylinder will transfer the ink in the next step to the substrate. A problem in transferring ink from the anilox roller to the printing roller is that the ink can remain in these cells formed on the surface of the anilox roller. The viscosity of the ink, as well as the speed of the printing process, can cause ink to remain on the anilox roll. This will affect the printing of the substrate. Additionally, ink residue will remain in the cells.

[007] After a partial transfer of the ink from the surface of the anilox roller, this part of the surface will rotate further and again hit the ink roller or ink source. The cells can function as a pneumatic pump, drawing air into the ink, resulting in foaming of the ink, and said air in the cells will limit the transfer of ink into the cell. The air in the cells must be replaced by ink and a certain amount of time is required to make this replacement, limiting the speed of rotation and ultimately the speed of printing.

[008] The desired color intensity of the substrate to be printed will directly affect the volume of the cells. If the cell volume is increased, more ink will be printed onto the substrate, intensifying the resulting color. Heavy layers of ink are formed on the substrate using cells with a relatively large volume, transferring relatively large droplets of ink, although print details are obtained using cells with a relatively small volume.

[009] Cell density is expressed in lines per centimeter. Known line screens for prior art cell-like surface structures are, for example, 100 - 180 lines per centimeter. The different line screens have specific purposes. An anilox roll with 100 lines per centimeter is well suited for printing heavy layers of ink onto a substrate. A relatively large volume of ink will be transferred in an anilox roller operating mode. Anilox rolls with 180 lines per centimeter will have a high resolution, making them best suited for printing details onto a substrate. Rollers with a screen with more lines will transfer ink droplets with a relatively smaller volume which will result in transferring less ink in total in this operating mode of the anilox roller. An anilox roller with a high-line screen is less suitable for printing heavy layers of ink.

[0010] In prior art printing methods, a balance is observed between high resolution and color intensity. A screen with more lines can be provided, with cells with more depth. This would increase the volume of the cell. However, in practice, the use of deeper cells will result in an increased risk of debris remaining in the cell. Not all of the ink in the cell will be transferred to the platen roller. Therefore, the printed substrate will still not present the desired color intensity.

[0011] One of the problems with prior art anilox rolls is the fact that an anilox roll can only have a screen of a single line pattern. Known anilox rolls do not allow printing of an image on a substrate where the image comprises both heavy layers of ink and details. Replacing an anilox roll is a time-consuming and expensive process, as printing will be temporarily disabled and different anilox rolls with different line screens must be provided.

[0012] Another problem in relation to known anilox rolls is the need to repeatedly clean the anilox rolls due to the ink that remains in the cells of the anilox rolls. This is due to the cellular nature of the anilox roll. This will also result in ink loss. Ink from subsequent printing processes will collect in the cells. The properties of the anilox roll will deteriorate. The anilox roll will need to be cleaned regularly. This is a time-consuming and difficult process.

[0013] Therefore, a goal of the invention is to alleviate or reduce at least one of the known problems of anilox rolls. Another goal may be to provide improved methods for forming an anilox roll.

[0014] An improved anilox roll is provided by the invention. The anilox roller comprises a cylinder with a roller surface. On the surface, a fluid distribution structure is arranged to receive, distribute and transfer a fluid such as paint. The fluid can be a liquid or pasty mass. The fluid distribution structure comprises a channel formed in the cylinder to distribute fluid entirely into the fluid distribution structure. A channel improves fluid transfer properties towards cells. Fluid is received more easily into a channel, and the channel is cleaned more easily. A channel comprises a recess formed in the surface of the anilox roll that is enclosed by the walls of the channel. The channel has a course, which is generally parallel to the direction of the channel walls on both sides of the channel part. Channel walls may converge or diverge locally.

[0015] In one embodiment, the fluid distribution structure is arranged to transfer, in a first operating mode for printing heavy ink layers, a suitable relatively large fluid droplet and, in a second operating mode for printing details, a droplet of adequate relatively small fluid. This is made possible according to the invention by a suitable combination of restrictions provided in the fluid distribution structure, wherein a restriction is formed by a local change of at least one of channel depth and/or channel width and/or shape. of the canal and/or canal wall. In exactly the same distribution structure, both functionalities, details and heavy layers are arranged on the same surface, depending on the operating mode.

[0016] An operational mode of the anilox roll is a functional behavior during the transfer of fluid to print the substrate. When printing details, relatively small amounts of ink are desired, and for printing heavy layers of ink, relatively large amounts of ink are desired. An anilox roll according to this embodiment combines the two properties, providing restrictions formed on the surface of the anilox roll.

[0017] In one embodiment, relatively small droplets suitable for printing details are provided by open cells formed in the fluid distribution structure surrounded only partially by the channel walls. The open cells are at least partially interconnected, allowing the formation of a droplet size in the first operating mode that is suitable for printing heavy layers of ink by combining the ink volume of different cells.

[0018] A restriction according to an embodiment comprises a change in the course of a channel or, in particular, a channel part. This allows the formation of a sinuous channel. Ink can be distributed entirely on the surface of the anilox roller in the channel. But distribution is hampered by the channel's sinuosity.

[0019] The anilox roll comprises in one embodiment for the first operational mode a fluid distribution structure comprising a sinuous channel on the surface of the roll. The meandering channel forms a restriction. In the channel, a relatively large volume of ink is received. The winding channel forms a device for printing a heavy ink layer. The device for printing the heavy ink layer is part of the fluid distribution structure. The constraints cooperate to form a structure of relatively small volumes in the channel, however, these volumes can be combined to form a relatively large droplet of ink depending on the operating mode. The operating mode is determined by the transfer of fluid from the anilox roller to the printing roller. The printing roller comprises the image to be printed. The image may comprise details or a heavy layer of ink or another image of the ink volume and determines the amount of ink to be transferred.

[0020] In one embodiment, the anilox roll comprises, for the second operating mode, channel parts formed in the channel, preferably in a sinuous shape, said channel parts having a droplet volume that is suitable for printing details. The channel parts form a device for printing details that is formed in the fluid distribution structure. Each channel part is arranged to transfer a fluid droplet of relatively small size to enable printing of details. The channel portion, on at least two opposing sides enclosed by the channel walls, forms a restriction that allows a particular operating mode.

[0021] In an advantageous embodiment, the device for printing a heavy layer of ink and the device for printing details overlap, allowing exactly the same channel part to function according to the operating mode determined by the ink transfer properties of the roller Printing.

[0022] In one embodiment, adjacent channel parts are positioned at an angle relative to each other to prevent a linear distribution of fluid received in that channel in a direction of travel of that channel. As channel parts are connected and the courses of the channel parts are positioned at an angle, the channel formed will allow a sinuous distribution of the fluid received in the channel.

[0023] In one embodiment, the connection formed is relatively large relative to the size of the droplet, and allows a droplet to move between adjacent channel parts, although the angle and sinuous shape of the channel prevents linear distribution of the ink.

[0024] In one embodiment of an anilox roll, different channel parts can be indicated/recognized by one skilled in the art. Still a channel may be a combination of relatively continuous, preferably also sinuous, channel parts that collectively form the fluid structure. Channel side walls allow for sinuous distribution of fluid received into the channel. The side walls of the channel are arranged to meander a flow of paint throughout the fluid distribution structure, but also to restrict linear flow. The ink can be received in the channels, but can also be transferred to the substrate for printing.

[0025] It is noted that U.S. 4,819,558 in the name of van C. J. Counard discloses an anilox roll. The disclosed anilox roll comprises a cellular structure of diamond-shaped cells with a pyramid-shaped depth. On the surface of the anilox roll, two cells are connected by a straight channel of limited depth. In U.S. 4,819,558, the channel is not arranged to allow two operating modes to be combined and superimposed on a single surface and, in particular, U.S. 4,819,558 does not disclose a channel with channel portions that combine to form a channel in that the course of the channel is angled. The revealed structure will only allow one operating mode, depending on the size of the cells. Sidewalls of the channels are not arranged to permit a meandering flow of fluid entirely into the fluid distribution structure. The surface structure of the anilox roll according to U.S. 4,819,559 is just a cellular structure.

[0026] It is noted that U.S. 4,301,583 discloses an anilox roll. The known anilox roll comprises a honeycomb cell structure. Two adjacent cells are connected via a straight channel. The cells and channels form in a circumferential direction of the anilox roll in a single row. The direction of travel of the channels in a row is located on a single line. The center points of connected cells are positioned in a single row. Linear distribution of the fluid is permitted in a circumferential direction of the anilox roll in the known embodiment. The side walls of the channel are not arranged to permit sinuosity of a fluid through a fluid distribution structure. The disclosed structure does not combine a device for printing heavy layers of ink and a device for printing details, but can only function according to one operating mode.

[0027] From WO 96/40443, an engraved roller is known, with a structure for distributing a fluid on the surface of the roller. The known structure comprises diamond-shaped cells, the cells being positioned in a circumferential direction of the roll in a single line. Cells are interconnected through small channels. The course of the channels extends in the circumferential direction of the roller. Side walls of the structure disclosed in WO 96/40443 are symmetrically positioned around the longitudinal geometric axis of the channel, i.e. the course of the channel. The known channel allows linear distribution of the fluid in a circumferential direction of the roller. According to the invention, restrictions will prevent a linear distribution like this.

[0028] A constraint to be used in combination with the fluid distribution structure may be the depth of the channel. By reducing the depth of the channel, a local change of the fluid distribution structure is obtained, which will allow reducing the droplet size of the ink to be received in the part of the channel that has the reduced channel depth. A local change like this can form a weakening line between cells formed at both ends of the channel with reduced depth. The depth of the channel can, for example, be reduced by a maximum of 50%, but preferably by a maximum of 30%. Because varying the depth of the channel locally affects the size of the ink droplet to be received in the channel portion, a restriction such as this is not preferred. In the applicant's experiments, it is shown that a local change of constraints that cooperate to allow a constant local droplet size in the structure results in the best printing properties.

[0029] The channel preferably has a generally flat or single-level base. This will allow the channel to receive relatively large amounts of ink along its entire length, or at least a large portion of its total length. A flat bed improves printing capabilities in the first operating mode for printing heavy layers of ink.

[0030] A channel comprises channel parts that are connected together. The channel parts are arranged to receive ink droplets of relatively small size that are suitable for printing details. The connection between the channel parts preferably comprises a connection of the same channel depth as the channel parts. This will allow physical interaction between volumes of fluid received in adjacent channel parts.

[0031] In one embodiment, the channel portions have a generally constant width. This will allow fluid transport between the channel parts in a relatively simple manner. Fluid flow between channel parts is slowed by changing the course of the channel. In an embodiment like this, the channel has no localized points of congestion and/or upward pressure. Rising pressure points have a negative impact on printing properties as the ink will be pushed out of the channel. This will prevent complete filling of the fluid distribution structure, which will decrease the function of the device to print heavy layers of ink. In particular, upward pressure may be the result of a blade scraping the roller. U.S. 4,819,588 discloses such an upward pressure point formed by converging walls, which converge in a direction parallel to the circumferential/rotational direction.

[0032] In one embodiment, the restrictions are formed by the side walls of the channel. The restrictions preferably comprise at least 90%, in one embodiment at least 95%, and in one embodiment at least 98% of the restrictions in the form of wall parts. A wall portion will extend above the fluid level when fluid is received into the structure between the wall portions.

[0033] It is possible for the parts of the wall that form the side walls of a channel to extend perpendicularly from a base of the channel. By applying perpendicular side walls restricting the base of the channel, a channel can receive a relatively large amount of ink. The channel preferably has a U-shaped cross-section. The channels may have a limited depth with respect to pyramid-shaped cells, which will reduce the chance that ink residue will remain in the channel after transferring ink to the printing roller. A generally flat base will prevent the formation of stagnation or upward pressure points/regions.

[0034] The anilox roller with a surface according to the invention will allow combining the properties of an anilox roller with a cellular structure of 100 lines per centimeter (first operating mode) and an anilox roller with a cellular structure of 180 lines per centimeters (second operating mode). The invention allows for a resolution of up to 300-500 lines per centimeter, and an anilox roller like this according to the invention will still be able to print heavy layers of ink with desired color intensity properties. An anilox roller will have a surface that will allow incoming ink to be distributed more evenly. Tension is reduced in the ink. The ink is laid out smoothly on the surface of the anilox roller, which will allow subsequent transfer.

[0035] Ink is received in the channel parts more easily, compared to a cellular structure. Ink can be transferred from the anilox roller surface more easily. Stresses in the ink will be reduced during transfer. Rotating the anilox roller during the printing process will result in less ink scraping off the anilox roller compared to a cellular structure. The ink is pressed onto the front of the blade and is received into the open structure of the channels. The internal tension in the paint is reduced. An advantage is that it is possible to print a heavy layer ink, while at the same time having a grid of fine lines that allows you to print details on a substrate.

[0036] Distribution of the fluid is possible according to one aspect of the invention in a limited manner. By limiting the distribution of fluid in the fluid distribution structure, a known problem for prior art anilox rolls is prevented. Known anilox rollers with straight parallel channels will allow much more distribution of the fluid, which makes it not possible to dose the ink in a suitable amount, in particular, for printing details. The restrictions according to the invention will allow such dosing in relatively small amounts of paint.

[0037] In one embodiment, wall portions of a channel portion are positioned in a radial direction from a position in the fluid distribution structure at a distance of less than 120 µm, in an embodiment less than 100 µm, preferably less than 80 µm. Each location in the fluid distribution structure is surrounded by a restriction at a relatively short distance.

[0038] This will prevent linear distribution of the fluid in an efficient manner. It is advantageous to restrict fluid distribution in the radial direction using wall parts. Only limited distribution is possible. The channel comprising channel parts does not extend linearly, but is suitably curved.

[0039] The curvature in one embodiment is at least such that straight connecting lines between locations in different channel parts are prevented. A suitable curvature may be an angle of at least 30 degrees, in one embodiment at least 45 degrees, and in one embodiment at least 90 degrees.

[0040] In one embodiment, foaming is prevented by channel parts that extend, and preferably a channel that has channel parts that extend generally in a circumferential direction of the anilox roll. Such channels may be formed in a suitable manner, as will be explained in more detail below, or using known techniques for forming such channels, wherein such channels extend adjacent to each other in a circumferential direction of the anilox roll.

[0041] Preferably, in a longitudinal direction adjacent to a first channel, a second channel is formed. The second channel is parallel to the first channel. A fluid distribution structure may comprise parallel oscillating or wavy channels. Such oscillating channels can be formed parallel to each other. Channels can be separated from each other by means of a separating wall or side wall. In a channel, a sinuous flow of fluid is possible, preferably in a circumferential direction of the anilox roll. The ink can be distributed entirely on the anilox roller. The free path in the channel structure is limited by restrictions according to the invention that will allow printing of details on a substrate because of the relatively small volumes of ink formed in the ink distribution structure.

[0042] A wall between the first channel and the second channel may have a width of less than 4 µm, preferably in the range of 1-3 µm. Relatively small wall arrangements result in a relatively large amount of anilox roll surface that can be used to receive ink. The amount of ink received and transferred in combination with the high resolution of detail is substantially improved over prior art arrangements, and allows operation in both operating modes. In combination with perpendicular side walls extending from a base of the channel, the channel will have a relatively large volume to receive ink, said volume of ink being easily transferable, leaving a small amount of ink residue, for printing details. The channels comprise restrictions that allow the printing of details in the image printed on the substrate. Restrictions are formed by the wall parts of the channel. The amount of ink that can be transferred is, when ink is combined from different channel parts, sufficient to permit printing of heavy layers of ink onto the substrate.

[0043] To allow a sinuous flow of fluid in the channel, the side walls of the channel can be formed antisymmetric with respect to the course of the channel. This will allow a wavy or oscillating pattern of channels to be formed. The channels have a course that follows a sinusoid. The course of the channel changes with each position and this change forms a restriction according to the invention, which allows the anilox roll to function according to both operating modes. The wall parts of the channel, in this embodiment, oscillating wall parts, allow a connection between the ink volumes received in the channel entirely along the length of the channel, but also do not allow interruption of the connection between the ink volumes due to curvatures in the course of the channel, allowing relatively small volumes of ink to be obtained for printing details.

[0044] Oscillating channels can have an amplitude that is generally equal to or preferably greater than the width of the channel. This will prevent linear distribution of fluid in the oscillating channel. A fluid flow in the channel will force paint to follow the winding channel, already curving at a distance from the channel side walls.

[0045] In one embodiment, the channels have a width in the range of 10 - 200 µm, in an embodiment 10 - 100 µm, preferably 15 - 80 µm.

[0046] In one embodiment, a channel portion is cell-shaped. Cell shape should be interpreted in a manner that does not include a closed cell. It is possible for the fluid distribution structure to comprise numerous separate wall portions surrounding the cell-shaped channel portions. The separate wall parts are fluid-conducting walls that allow directing a moving fluid in a desired direction. Sinuous distribution of fluid in the channel formed between cell-shaped channel parts is possible. A linear distribution of the fluid is prevented. The fluid can be distributed over a large area of the fluid distribution structure, but the distribution is biased by restrictions that allow only sinuous distribution.

[0047] The cell-shaped channel parts have at least three open connections with adjacent cell-shaped channel parts. This allows distribution of the incoming fluid into the channel parts and allows for a sinuous distribution. The cell-shaped channel parts are, unlike cells according to the prior art, part of a channel that receives ink droplet suitable for printing details. The connection between channel parts is arranged to allow a relatively substantial amount of the droplet volume to move freely between adjacent channel parts, but does not allow for linear distribution. The surface structure of the anilox roll according to the invention formed by restrictions is not a cellular structure that allows receiving fluid in the respective cells and the structure according to the invention does not allow unlimited linear distribution of the fluid entirely on the surface.

[0048] The cell channel-shaped channel part is, in one embodiment, characterized by channel wall parts that converge towards a connecting part that forms the connection between the first cell-shaped channel part and another cell-shaped channel part. In one embodiment, a channel part according to the invention is provided only if the connecting part is at least 10% of the channel width, 10% of the width guarantees sufficient distribution.

[0049] In one embodiment, a cell-shaped channel portion has at least two connections within adjacent cell-shaped channel portions. This will allow the combination of the volume of fluid received in the channel parts in a first operational mode, by virtue of the connections allowing to combine the two volumes of ink and, in the second mode of operation, with the connection between the connected cells can be separated into a second operating mode, allowing transfer of small volumes of ink. If multiple connecting parts are present between two adjacent cell-shaped parts, the connecting parts may be smaller. In one embodiment, such connecting parts may be less than 5% of the channel width. The smaller connecting parts preferably do not have a reduced channel depth.

[0050] Additionally, a width of an open connection between channel parts is preferably at least 40%, and more preferably at least 60% of the width of a cell-shaped channel part.

[0051] In one embodiment, a cell-shaped channel portion has at least three adjacent cell-shaped channel portions. This will allow you to obtain volumes of ink to print heavy layers of ink in a straightforward manner. In a preferred embodiment, the cell-shaped channel portion has at least two connections with each adjacent cell-shaped channel portion. This will allow for easy ink transfer and combination of ink volumes during transfer in the first operating mode.

[0052] In one embodiment, the base of the connection between channel parts is at the same level as the bases of the channel parts. Restriction on flow between channels is reduced and only limited by the position of the channel walls. The depth of the channel is not a congestion point for the ink, which would result in a non-optimal application of the properties of the fluid distribution structure.

[0053] The open channel structure allows for a multi-line screen preferably above 120 lines per centimeter and, in one embodiment, at least 150 lines per centimeter. This allows for high resolution printing. The open structure allows the transfer of high ink volumes higher than in the prior art arrangement would be possible only if cellular structures with relatively low line screens were used. The invention allows for a screen of many lines and printing of heavy layers of ink with a desired intensity.

[0054] The channel formed on the surface of the anilox roll extends entirely over a relatively large surface area through connections. This relatively large surface area allows a large amount of ink to be collected during transfer. The connected channel parts may have a surface area of at least four or six or even more times greater than the cell surface of the anilox rolls according to the prior art.

[0055] According to one embodiment, the fluid distribution structure has a grid. The grid is repeated on the surface of the roll. The grid is formed by channel wall parts and channel parts formed between the wall parts. The grid forms the fluid distribution structure that allows limited fluid distribution preferably at most four times the size of the grid. In one embodiment, a linear connection between two points on the fluid distribution structure is limited to a length of at most four times the size of the grid. Those skilled in the art can determine a grid size. A grid size can be determined in a manner similar to the prior art arrangement, for example, lines per centimeter.

[0056] In one embodiment, the free path, which is the length in a straight line from a point on the fluid distribution structure that is positioned between two walls in a first direction, is at most four times the free path in the second direction perpendicular to the first direction. The second direction is preferably a connecting line between two generally parallel walls or the direction of travel of the channel part. The distribution due to a free floating path in this modality is in the form of an ellipse. The limited distribution is preferably correlated with the size of the grid and therefore with the length of the connecting line between two at least parallel walls of two different open cells. The limited distribution according to an embodiment is further limited to a maximum of three times the grid size.

[0057] Preferably, an anilox roll is provided with a channel portion that is cell-shaped with a combined surface area of at least 20,000 and more particularly at least 40,000 µm2. In one embodiment, the combined surface area is spread throughout the cylinder. The combined surface area is the sum of each open cell connected in that channel. Such surface area may be substantially greater than the surface of the cellular structure of comparable anilox rolls according to the prior art. Such surface areas are similar to at least four connected cells of known grid pattern (100 lines per centimeter) for celled anilox rolls.

[0058] In one embodiment, channel portions extend generally in a circumferential direction from the anilox roll. This will allow an open connection between channel parts in a circumferential direction. This is advantageous for filling the channel parts with fluid. Because the channels are connected with other channel parts in a circumferential direction, ink is received more easily in the channel relative to anilox rolls with cells according to prior art arrangements, while the channel part, preferably with a reduction in a width of maximum 40% in a connection between channel parts, it allows the escape of air trapped in the channel receiving the fluid. This reduces the amount of ink foaming during the printing process.

[0059] In an advantageous embodiment, a restraint structure formed by walls is provided with a pattern of wall parts, and the wall parts positioned perpendicular to the first wall part, wherein said wall parts are at least twice as large the size of the channel width of the channel formed between the wall parts. This is a particularly simple embodiment of an open structure with a limited free path. In an advantageous embodiment, the free path is at most four times the width of the channel.

[0060] The invention additionally concerns a printing apparatus. The printing apparatus comprises a printing device with a supply for a substrate to be printed and a supply for ink, wherein the printing device comprises an anilox roller mounted in a bearing, said anilox roller comprising at least one of the aforementioned resources.

[0061] The invention also relates to a method for forming an anilox roll. The method comprises supplying a cylinder for an anilox roll having an outer surface to be worked. The method preferably comprises providing at least one laser source and laser engraving the outer surface of the anilox roll. It is clear that those skilled in the art will be able to use future techniques that function in a similar manner to the laser to carry out the method according to the invention.

[0062] The method according to the invention comprises laser engraving the outer surface of the anilox roll with a laser focus that is formed with the laser source. The laser and its laser focus can focus the beam intensity into a small position on the anilox roll. This allows you to work the anilox roll. Anilox roller can be used in printing industry.

[0063] The method according to an embodiment of the invention comprises applying an optical guide to the laser light path to enable the laser focus to perform an alternating movement on the external surface to be worked. The reciprocating movement leads to repetitive movement in the laser focus position. The reciprocating movement preferably causes a displacement of the laser focus on the anilox roll in a direction that is basically parallel to the longitudinal axis of the anilox roll. This creates the ability to perform repetitive movement of the laser focus on the surface to be worked on in a surprisingly simple way.

[0064] In one embodiment, the laser focus will basically move with a constant speed entirely on the surface of the roller. A generally uniform evaporation of the surface material on the surface of the anilox roll is obtained. This allows the formation of a generally uniform channel. The channel depth will be at a generally similar level throughout the formed channel. Additionally, the channel will have a general U-shaped cross section.

[0065] In one embodiment, the optical guide is a crystal. Alternating motion is caused by supplying a varying current to the crystal. This can cause a deflection in the trajectory of the laser beam, resulting in movement of the laser focus. The variable current may be a sinusoidal current, such as a well-known alternating current (AC). This creates an alternating sinusoidal movement.

[0066] Preferably, the method comprises a change in the reciprocating movement of the laser focus that is at least greater than the width of the laser focus in the same direction. In this way, it is possible to laser engrave an external surface with a width of two or more times the width of the laser focus. The surface can be engraved in a simple operation of the method to form an anilox roll. The result is that laser engraving is carried out more quickly.

[0067] It is further advantageous to laser engrave the anilox roll at the same time as the anilox roll rotates around a longitudinal geometric axis of the anilox roll. Furthermore, the laser can move in a direction basically parallel to the longitudinal geometric axis of the anilox roll. In this way, the entire surface of the anilox roll can be worked. This technique is known in existing state-of-the-art technology. By applying the alternately movable guide, prior art methods can be accelerated.

[0068] It is exceptionally advantageous to apply the method using a continuous laser. This allows the possibility of continuously and at the same time reciprocally moving the laser focus entirely on the surface. In combination with the rotating anilox roller, which can be rotated around its longitudinal geometric axis, an oscillating track can be burned. This track is comparable to a CD or DVD track. The method of forming an outer surface comprising such an oscillating groove, surrounded by walls which are left unburned, can advantageously be applied in the printing industry. Laser engraving is used here to form a channel that extends in a rotational direction from the anilox roll.

[0069] A further aim of the invention is obtained by an apparatus for forming an anilox roll for use in a printing process, comprising a support unit for supporting the cylinder-shaped anilox roll and for rotating the anilox roll in around a longitudinal geometric axis. According to one aspect of the invention, the apparatus comprises an engraving unit which is arranged for parallel movement with respect to the geometric axis of the cylinder of the anilox roll to engrave a structure on the outer surface of the anilox roll, especially in combination with a roller. of rotating anilox. The apparatus also comprises a drive unit for actuating recording adjustments of the recording unit. Recording settings are the recording trigger parameters with which the recording can be affected. Those versed in the technique understand how to adjust the recording.

[0070] Advantageously, the engraving unit comprises at least one laser for laser engraving the outer surface of the anilox roll with a laser focus. At least one goal is achieved when the recording unit further comprises an optical guide for adjusting the light path of the laser and, more specifically, for moving the laser focus in a repetitive or alternating manner. With this, a further change of laser focus is possible. The position to be worked on can also be chosen in this way. Using an optical guide, it is possible to make an additional change of focus, allowing quick and small changes. More specifically, these changes can be repetitive.

[0071] In an additional advantageous embodiment, the optical guide is a deflector. A deflector, such as a crystal, can be used, with which the laser trajectory and thus the position of the laser focus can be adjusted, more specifically changed. The deflector can be controlled quickly and precisely. Those skilled in the art will be familiar with different deflectors to create a repetitive transition of laser focus. In an advantageous embodiment, the crystal can be connected to a power source, more specifically an actuable or controllable source, wherein the voltage supplied is proportional to a certain deflection and, more specifically, a change in laser focus.

[0072] In one embodiment, the crystal can be arranged to deflect the incoming laser beam as a function of voltage.

[0073] In another advantageous embodiment, the recording unit comprises an optical guide that is positioned in the path of the laser light, where the guide is movably connected to the recording unit. This allows the movement of the laser focus on the surface of the anilox roll, in addition to the movement of the recording unit as a whole. The extra movement is superimposed.

[0074] It is especially advantageous to connect the optical guide to the recording unit by means of a movement unit, wherein the movement unit is arranged to allow the laser focus to perform an alternating movement. In this way, the alternating and repetitive movement of the laser focus can be used to form a regular structure on the anilox roll. This regular structure can be obtained by engraving a rotating anilox roll and additionally moving the laser in a longitudinal direction along the roll. The structure thus formed is different from the aligned structure formed in a natural way.

[0075] The reciprocating movement preferably causes the laser focus to move in a direction basically parallel to the geometric axis of the cylinder. This means a larger surface can be worked in a single labor step. Preferably, the change is at least greater than the width of the laser focus in the same direction. This allows you to work on an area with a width of at least twice the size of the spot. Also, with this, a wave-like movement can be obtained when the reciprocating movement is combined with a rotation of the anilox roll around its longitudinal geometric axis.

[0076] According to the invention, the laser can be a continuous laser. Especially in combination with a rotating anilox roller and an alternately moving guide, a track or channel is formed in the anilox roller. The track has a balance. The drive unit is preferably connected to the support unit and the movement unit. The drive unit may be arranged to rotate the anilox roll during laser engraving with an alternating movable laser focus. This allows the manufacture of an unprecedented anilox roll, with advantageous properties for transferring ink. Ink can be easily temporarily absorbed into the oscillating channels.

[0077] It is advantageous to provide the recording with an objective lens. The lens is capable of focusing the laser. The lens can be the optical guide that performs a reciprocating movement.

[0078] It is possible to provide the recording unit with two lasers, or more lasers, and/or with one or more beam splitters. In this way, multiple channels can be provided on the anilox roll simultaneously.

[0079] In a preferred embodiment, the reciprocating movement leads to a change in laser focus of at least 20 µm. This small change may be enough to create a wobble in the channel on the worked surface of the anilox roll.

[0080] Although the invention is described and will be described with respect to preferred embodiments, it is clear that, according to the scope of the invention, multiple and different embodiments are possible. It is a goal of this application to protect the described embodiments, the embodiments indicated by the claims, as well as their equivalents. Those versed in the technique - now that the advantages of the invention are experimentally known - will be able to construct different modalities. It is the inventor's intention to also protect these embodiments with this application.

[0081] More specifically, those skilled in the art can form restrictions on the surface of the anilox roll in accordance with the disclosure in this application that allows one or more of the advantages to be obtained. Functional protection must therefore be possible.

[0082] In view of the above, as well as in the following description, aspects of the invention are described, and advantages of the measures are described. The inventor intends to protect all mentioned and unmentioned advantages that the invention has over the available state-of-the-art technology using this application and/or divisional applications.

[0083] The invention will be described with reference to the following description considered in conjunction with the attached drawings, in which: - Figure 1 is a schematic side view of a printing apparatus for a flexographic process; - Figures 2a and b are detailed views of a surface of an anilox roll engraved according to the latest technology available; - Figures 3a-h are detailed views of embodiments of an external surface of an anilox roll according to the present invention; - Figure 4 is a detail of a part of the channel section of an anilox roll according to the embodiment of Figure 3b; - Figure 5 is a schematic view of an embodiment of a recording device according to the invention.

[0084] Figure 1 shows a schematic side view of a part of a printing apparatus 1 used, for example, in a flexographic process. The printing apparatus 1 may be part of a series of printing apparatus for printing with different inks, or printing with various techniques. Those skilled in the art are familiar with different embodiments of a printing apparatus 1. The printing apparatus 1 is adapted and arranged to apply ink to a substrate in a desired pattern.

[0085] In the embodiment shown, the printing apparatus 1 comprises a source roller 2 which is partially immersed in an ink source 4 comprising a certain amount of ink 3. The source roller is rotatable, and the outer surface of the source roller can be a rubber coating.

[0086] After the source roll 2, a rotating dosing roll 5, or anilox roll, is positioned, in which the longitudinal geometric axis of the anilox roll 5 is positioned parallel to the longitudinal geometric axis of the source roll. This makes it possible to form a point of contact, or contact line 6. Rollers 2 and 5 are in contact, or practically in contact, with each other. Adjacent to a circumferential side of the metering roll, a blade 7 is positioned over at least a portion of the length of the metering roll. In line with the longitudinal geometric axis of the metering roller 5, a rotating printing cylinder 9 is positioned. The printing cylinder comprises elevations and recesses, the elevations forming a negative of the image to be printed.

[0087] The elevations and recesses determine an operating mode for the anilox roll 5. When the image contains details, ink in the form of relatively small-sized droplets must be transferred from the anilox roll to the substrate, whereas, to print layers heavy ink, droplets of relatively large sizes must be transferred.

[0088] The substrate 13 or the product to be printed can be positioned close to a circumferential side of the printing cylinder. The substrate is movable in the longitudinal direction. A rotating printing roller 11 is positioned next to one side of the printing roller 9, wherein the printing roller 9 and printing roller 11 are positioned on both sides of the substrate.

[0089] In the figure, an example of a substrate 13 is shown. It is obvious that different types of substrates 13 can be printed. Those versed in the technique can adapt the printing device to the substrate to be printed.

[0090] An operating method of the apparatus shown will be described below. When the apparatus is operated, the source roller 2 is driven, resulting in a rotation of the source roller 2 in such a way that the outer surface of the roller moves through the ink 3 of the ink source 4. The outer surface of the source roller may comprising a layer of rubber, the ink will be absorbed and will be transported in the direction of the anilox roller 5, which is rotating in an opposite direction compared to the source roller. Near the contact point 6, ink will be transferred from the source roller 2 to the anilox roller 5. The surface of the anilox roller is provided with an ink-absorbing structure. The structure is described in more detail in figure 2.

[0091] The anilox roller 5 will absorb a certain amount of ink from the source roller 2. The blade 7 ensures that excess ink is scraped off in such a way that the anilox roller 5 absorbs and retains an adequate amount of ink. Then the ink will be transferred to the printing roller 9. A thin layer of ink is transferred to the elevations of the printing roller 9. Compared with the anilox roller 5, the printing roller 9 is rotating in the opposite direction. The print roller 5 will continue to rotate and apply the image to the substrate 13. The print roller 11 supports the substrate during the printing process.

[0092] Other configurations are also possible. The apparatus may be provided with a closed ink source 4 comprising an ink supply and an ink drain. It is also possible for multiple blades 7 to be provided. The configuration description is for example only. It may be obvious that multiple configurations of the anilox roll 5 are possible without departing from the invention.

[0093] Figure 2a shows a detailed view of a surface of an anilox roll 5. The surface structure shown is known from the prior art. The anilox roll 5 is provided with a frame 14, which may be formed from a plurality of regularly positioned cells 15. The cells 15 are formed by recesses in the anilox roll 5. The cells 15 are separated from each other by means of walls sides 17 with a width w1. According to the latest technology available, the width w1 can be 10-80 µm. The side walls ensure that the ink cannot move from one cell to another. If ink is provided on the surface of the anilox roll with the surface structure 14, the side walls 17 will extend above the ink level. Ink will be inserted into cells 15. Excess ink will be removed by blade 7.

[0094] The cells have an overall size h of the order of 10-80 µm. Each cell has a depth (not shown). Each cell has a certain volume. The ink volume corresponds to the ink droplet to be transferred to the printing roller and substrate.

[0095] In the embodiment shown, the cells are shaped hexagonally, and the cells are positioned in a honeycomb-like structure. The distance c between the center point of two neighboring cells, where the distance is measured perpendicular to the direction of roll rotation, determines the line screen of the anilox roll. Known line screens for prior art cell-like surface structures are 100, 120, 140, 180 lines per centimeter.

[0096] Figure 2b shows another embodiment of an external surface of an anilox roll according to the latest technology available. In this embodiment, channels 18 are applied along an outer surface of the metering roll. The channels have a width h (15-80 µm) and are separated from each other by means of a wall 19 with a thickness t. The longitudinal direction of the channels is positioned at an angle a in relation to the rotation direction R of the metering roller. An embodiment like this is suitable for applying paint to the substrate in a smooth manner. It is clear that the channels are straight lines and that there are therefore no restrictions on the spread of paint in the channel.

[0097] Currently known anilox rolls do not individually meet the criteria that are currently established in the printing industry. Therefore, in many applications it is necessary to use different anilox rolls, which is something that slows down the printing process and makes the printing process labor-intensive and expensive.

[0098] Figure 3a shows a first embodiment of an anilox roll according to the present invention. Figure 3a shows a view of the bearing surface 100 of an anilox roll on which a fluid distribution structure is applied. The fluid distribution structure is shown more specifically by means of wall portions of channels that are formed in the structure. Wall parts are indicated repeatedly by lines. The "empty" parts in figure 3a are recesses in the bearing surface, which can be, for example, formed by means of laser and laser engraving and/or evaporation.

[0099] The part of the bearing surface 100 that is shown in figure 3a is provided with a pattern, which is formed by two wall parts 21, 22 that are positioned at an angle with respect to each other. The wall parts form dams or restrictions and have a thickness t. The wall parts 21, 22 are surrounded by a channel 20 which extends entirely onto the outer surface of the anilox roll. The channel is arranged to absorb mass, more specifically paint. The paint can be collected in the formed channel 20 and can be spread entirely on the outer surface, where restrictions ensure that the flow capacity is limited.

[00100] In one embodiment, the first restraints 22 are placed at an angle of about 90 degrees relative to the second restraints 21. The first restraints 21 are further positioned at an angle Y relative to the direction of rotation R of the roller. anilox. Preferably, y is equal to 0 degrees. The second constraints are positioned longitudinally relative to the first constraint, and the constraints are positioned at a 90 degree angle relative to each other. Other angles are certainly conceivable. In this way, a regular pattern is obtained. In one embodiment, the pattern may form a zigzag pattern.

[00101] Preferably, the anilox roll pattern is formed in such a way that a volume of ink has only one free path or limited path distance, measured from an arbitrary point on the absorption surface 20. The path distance is defined as the distance a piece of paint can move in a random radial direction from a random point in a channel until it hits a wall. Preferably, the free path is less than 150 µm and, in the embodiment shown, less than 100 µm. Preferably, the free path is less than 50 µm. The free path ensures that the ink can flow freely over a certain but restricted length. Because the free path is limited, a resistive force is applied to the ink in such a way that the ink cannot flow freely over too large a portion of the roller. Because the restraints are positioned at a relatively small distance from each other, a large distribution of ink is impossible. Surprisingly, in this way an anilox roll is obtained which, on the one hand, has an open structure, but in which, on the other hand, cells, in this case open cells, can be recognized. Printing tests with such an anilox roll have shown that a structure like this allows printing of heavy layers with sufficient color intensity, as well as printing of detailed structures. According to the latest technology available, this result could only be obtained by printing in two stages, more specifically first using an anilox roll with a small line screen and then using an anilox roll with a larger line screen, or vice versa.

[00102] In one embodiment, the constraints have a width t that is less than 8 µm. Preferably, the restrictions have a width that is less than 5 µm. Even more preferably the restrictions have a width t that is between 2 and 3 µm. In this way, the walls form only a very small part of the total circumferential surface of the anilox roll. It will be clear to those skilled in the art that the wall parts according to the present invention function basically as restrictions against the free distribution of paint, when the paint is present between the walls.

[00103] The location of the restrictions allows open connections to be formed in the structure on the outer surface of the anilox rolls. The ink can be well distributed entirely on the anilox roller, especially when the ink is collected in the channel. The restrictions are placed in a way to ensure that the paint cannot flow freely, especially when the paint is being released. The wall parts form restrictions on the anilox roll and ensure that the ink is held in place on the anilox roll. The presence of the large absorption surface 20 ensures that the anilox roller according to the present invention can collect a large volume of ink. Furthermore, the restrictions allow the ink to be collected well from the source roller. The positioning of the restrictions is such that ink received in the fluid distribution structure can be freely but limitedly distributed entirely on the anilox roll, such that generally a small layer of ink film is provided on the anilox roll.

[00104] Additionally, the unlimited distribution of paint is prevented by the restrictions, since the restrictions form natural barriers against the flow of paint. Additionally, the anilox roller structure ensures that ink transfer to the printing roller is possible in multiple operating modes. Negative parts of the printing roller are provided with a dosed amount of ink, and the detailed parts of the negative are also provided with a suitable amount of ink.

[00105] Therefore, it is possible with an anilox roller according to the present invention to obtain good color intensity and heavy layers, as well as fine structures in the line technique. Therefore, it is no longer necessary to specify cases where both the total color intensity as well as the details are important, to change the anilox roll. Only one anilox roll is needed to print both heavy layers and fine details.

[00106] Another advantage of the anilox roll according to the present invention is that it needs to be cleaned less frequently. Anilox rolls according to the latest available technology have large quantities of walls 17, 19. Furthermore, the walls 17, 19 occupy a large amount of space in relation to the total available dyeing surface. According to the present invention, the wall parts occupy less than 10%, in one embodiment less than 5% or 3%, preferably less than 2% of the total surface of the anilox roll.

[00107] To transfer an adequate amount of ink, the cells 15 and channels 18 according to the latest technology available have a relatively large depth. Generally, the depth of the cell or channel is greater than its width. This results in the fact that it is difficult for the ink to exit the cell or channel and eventually ink residue will accumulate and block the cell or channel. The anilox rolls then need to be cleaned. This is a difficult and tedious task, which is also attributed to the fact that the cells and channels have a relatively large depth. What's more, anilox rollers can easily get damaged during cleaning.

[00108] In anilox rolls according to the present invention, this problem is less relevant. Because a greater absorption surface for ink is present, a shallower depth will be required to transfer the right amount of ink. Furthermore, the constraints are positioned at a relatively large distance from each other. This ensures that ink transfer is relatively easy, so that ink build-up on the anilox roller according to the present invention is less likely to occur. An additional advantage of the relatively large distance between the restraints, and the relatively shallower depth of the anilox roll, is that the surface structure can be reached more easily for cleaning.

[00109] In one embodiment of the present invention, shown in figure 3b, winding channels 24 with uniform walls 25 are provided. It is relatively easy to form this embodiment. Sinuous channels can have the shape of a wave, more specifically a sine wave, see figure 4, in which in succession a turn in one direction is alternated by a turn in the other direction. Referring to Figure 4, the walls have a top 32 and a base 31, wherein the walls have an amplitude and wherein the walls oscillate about a baseline 30.

[00110] Preferably, the baseline 30 of the sinusoid is positioned parallel to the direction of rotation R of the anilox roll. The course of the sinuous channel 24 follows a sinusoid.

[00111] Due to the fact that, in a preferred embodiment, the wave amplitude is greater than the channel width, a channel is obtained with limited possibilities for spreading or distributing the fluid received in the structure. In this application, the term free path is used. Free path refers to a radial expansion from any arbitrary point in the formed channel. In the sinusoidal channel shown, the free path is limited to a maximum of one wavelength. Due to the limitation of free or radial distribution, it is possible for ink to be absorbed into the channels on the outside of the anilox roll. The limited distributions result in less stress on the ink that is absorbed and supplied from the anilox roll when in use. The volume of the channel parts on the outer surface of the anilox roll is relatively large, compared to the available state-of-the-art volumes that are obtained using closed cell grid patterns with a large line screen. With the anilox roller according to the present invention it is therefore possible to approach and/or improve the properties of large line screen anilox rollers.

[00112] However, the anilox roll pattern according to the present invention also has a direct spreading limitation. With this, it is also possible to apply details to the substrate during printing. According to the latest technology available, this was only possible using anilox rolls with a screen of relatively small lines. The anilox roller according to the present invention combines these two properties (heavy layer printing and details) and thus leads to a reduction in the number of printing steps required in the printing process.

[00113] The limitation in spreading is achieved by the fact that wall parts 25 always create somewhat limited channel parts which are otherwise connected to each other by (indirect) connections. The channel parts according to the invention are limited by the fact that the distribution in a straight line between the wall parts 25 is less than the indirect or curved distribution.

[00114] In the example of figure 3b, the wavelength is comparable to the grid size of the pattern. The grid size and channel width are comparable. Preferably, the wavelength is less than four times the grid size, preferably less than two times the grid size. Due to the fact that the grid size and wavelength are comparable, in fact each time a cell-like pattern is obtained that is comparable to a honeycomb pattern according to the state-of-the-art technology available. According to the invention, however, these cells are connected in a limited way to each other and separate connections are formed by removing closed wall parts.

[00115] The fluid can be distributed entirely over a large part of the surface of the anilox roll if the path followed is winding on the surface.

[00116] The wavelength can be 80 µm, for example, while the grid size is approximately 30 µm. The anilox roller according to the present invention, having these dimensions, combines the properties of anilox rollers with a screen of large and small lines, i.e. heavy ink layers (first operating mode) and detail printing possibilities ( second operating mode.

[00117] Figure 3b shows an embodiment, in which two walls that are located close to each other are positioned at a distance from each other. The walls 26, 27 which are positioned close to each other have a distance d which is equal to twice the amplitude of the sinusoid. Depressions 26 of one wall penetrate protrusions 27 of the neighboring wall. This mode guarantees that the paint parts have a maximum free path. The structure/pattern prevents the mass to be collected between parts from being easily spread and, more specifically, that, during the supply of ink by the anilox roller, a large mass of ink can be gathered for supply. Curved connections between channel parts are possible. With this, the aforementioned grouping becomes possible, but only in a certain small quantity. With this, relatively large volumes of dough can be transferred. Additionally, it is possible, as shown in figure 3c, to position the channels and walls at an angle ß with respect to the rotational direction (or circumferential direction) R. Specifically for printing heavy layers of ink, this is a beneficial embodiment.

[00118] Figure 3d shows another embodiment, in which different constraints 51, 52, 53, 55 are placed in such a way that a regular pattern is formed. The line-shaped restraints 51, 52, 55 are positioned in a triangular manner, where the corner portions of the triangle are formed by cross-shaped restraints 53. Between the cross-shaped restraints 53 and the ends of the cross-shaped restraints 53. shape of lines 51, 52, 55, undercuts are present. A particle of paint can flow freely between different parts of triangular channels 54. Free flow in a straight line is limited. The walls form dams to restrict mass spreading in the channel parts. Furthermore, the walls form dams against the accumulation or concentration of paint, for example, when the paint has been supplied.

[00119] The restriction in the shape of the cross-shaped wall part 53 preferably has a size that blocks the flow of fluid along the wall part 51, but allows its deviation. By increasing the wall part 53, a larger barrier is formed. However, the distance between an end of the wall part 51 or 52 and the cross-shaped wall part does not change thereby. Therefore, the size of the connecting part remains the same.

[00120] The size of the connecting part 49 is preferably equal to at least 10% of the length of the wall part 52. Hereby, the cell-shaped channel parts 47, 48 which are positioned on opposite sides of the wall 52 have an open connection with each other. What's more, two connections are formed between these cell-shaped parts. In the first operating mode, it is relatively easy to obtain a relatively large ink droplet size due to the fact that both cell-shaped channel parts 47, 48 supply the ink.

[00121] The capacity of the cell-shaped channel portions 48, 48 is approximately equal to the relatively small droplet size that is desired for printing details and corresponds to the droplet size that is desired for printing details in available state-of-the-art technology, such such as, for example, anilox rolls with 180 lines per centimeter.

[00122] This pattern ensures that the ink can be well absorbed into the anilox roller, and that the ink can be supplied well to the printing roller. Additionally, this modality ensures that the ink has sufficient freedom to flow and, however, that the film layer is present on the anilox roll.

[00123] Likewise, figure 3b is an example of a sinuous channel, since fluid flow along a large part of the anilox roll surface is possible, due to the channel-shaped parts cells are connected to each other. By flowing along the wall parts 51, 52, fluid can reach other cell-shaped channel parts. Exactly this property guarantees that the anilox roll can combine the printing properties of both the first and second operating modes.

[00124] Embodiments of figures 3a to 3d have a fluid distribution structure that is formed on the surface of the anilox roll, in which the channels formed basically have a similar depth. With this, the size of the fluid volume in the channels will not be disturbed locally and thus the fluid will remain more easily distributed entirely on the external surface than with the state-of-the-art technology available.

[00125] Figure 3e shows an additional embodiment according to an aspect of the invention. The embodiment shown comprises a channel 301, which has wall portions 302, 302'. Channel 301 has a width w2. The wall parts are positioned close to each other in a relatively parallel oscillating manner. In this way, a sinusoidal-type oscillating channel is obtained. The wall parts are placed at such a distance from each other that the top 351 and depression 352 which are closest to the center of the channel 301 are spaced with an interval t. The range suggests that a straight-line distribution of the fluid is possible. However, it is apparent that when the t interval is relatively small, this aligned distribution is impeded. The wall parts form restrictions that determine a course of the formed channel. The channel formed snakes entirely on the surface of the anilox roll.

[00126] The flow profile in the channel will basically be the same in different parts of the channel, which means that the flow profile will be the same in those parts of the channel that run in different directions. However, the direction of the flow profile, and consequently the flow, will be different in neighboring channel parts. The flow cannot develop in a straight line, in the direction of rotation R. The walls guide the flow in such a way that the flow can only meander over the channel.

[00127] Preferably, the interval t is small, compared to the width w2 of the channel. Preferably, the interval t is less than 10% of the channel width w2, and even more preferably less than 5% of the channel width.

[00128] Figure 3f shows an embodiment of a channel 401. The channel comprises serrated-shaped walls 403, 403'. In channel 401, different channel parts 405, 407, 409 are visible, each having its respective course 406, 408, 410. A course 408 of the channel part 407 is positioned at an angle with respect to the course 406 of a channel part 407. neighboring channel 405. In the embodiment shown, the angle is approximately equal to 90 cranes, but it is also possible to use other angles. By positioning the channel parts at an angle to each other, straight distribution of the fluid in the channel is prevented. On the other hand, meandering flow on channel 401 is possible. The walls 403, 403' are placed in such a way that these walls guide the flow in a sinuous manner. Straight-line distribution of the fluid is impeded by the walls.

[00129] Figure 3g shows a cross section of a channel 501 according to an embodiment of the invention. The 503 base of the channel is basically flat. The walls 502, 502' are basically positioned perpendicular to the base 503. In this way, a relatively large amount of fluid can be absorbed into the channel. Preferably, the width of the channel is large relative to the height of the channel. In this way, a large volume of fluid can be absorbed into the channel and, in this way, it is also possible to supply the amount of fluid relatively easily. There is only a relatively small amount of fluid that will remain in the channel during substrate printing.

[00130] Additionally, it is possible that the embodiment shown in figure 3g is related to a cell-shaped channel and a channel according to an aspect of the invention. The cell base and the channel base are basically positioned at the same level. This improves the flow of fluid between cells through the channels. In this way, the channels prevent congestion or upward pressure on the fluid. Upward pressure in the fluid can cause the channel base (connection) to be positioned higher than the cell base.

[00131] Figure 3h shows a channel 600 with channel parts 601-605. The channel 600 is part of the fluid distribution structure to receive, distribute entirely on the anilox roll, as well as transfer the fluid to a subsequent print roll. Channel 600 is arranged to distribute and guide fluid entirely in the fluid distribution structure. The winding channel 600 which is shown here forms a heavy layer impression unit in the fluid distribution structure. The channel 600 comprises a detail printing unit which is formed in the winding channel 600 by means of channel parts 601-605. Channel parts 601-605 each have a droplet volume that is suitable for detailed printing. Neighboring channel portions are positioned at an angle relative to each other to prevent straight-line distribution of the fluid in a course of the channel, as well as to allow for sinuous distribution of the fluid in the channel 600.

[00132] Figure 4 shows in detail a restriction 33 according to an embodiment of the invention. In the embodiment shown in figure 3b, the wave amplitude is greater than the width between two walls. The wall itself is approximately 1-4 micrometers in size. The channel according to figure 3b has a width between 10 and 150 micrometers, more preferably between 20 and 100 micrometers, and even more preferably between 30 and 80 micrometers. The wave may have an amplitude of at least approximately 50 micrometers. According to the invention, an open structure is used to considerably reduce the size of the wall parts compared to available state-of-the-art technology. This leads to a further increase in the surface area that is available to receive ink and to transfer ink across the outer surface of the anilox roll.

[00133] An open structure according to the invention can be characterized by larger surfaces of channel parts between wall parts that are formed on the outer surface of the anilox roll. The channel parts are connected with other large surfaces by means of connections that are provided between the wall parts. Although a straight connection is preferably prevented, a limited sinuous connection is possible.

[00134] The pattern according to the invention and, more specifically, the pattern according to figure 3b, reduces the amount of foaming that occurs on the anilox roll. Related to this is the fact that channel parts and, more specifically, channels are able to absorb mass and, more specifically, paint more easily. The rotation of the anilox roller according to Figure 3b is basically parallel to the base of the sinusoid, and therefore the air in the open channel parts can be removed from this channel part by virtue of the relatively open structure according to the invention.

[00135] Of course, the invention is not limited to sine wave channels. The channel and/or walls may also have a serrated shape or any other repetitive pattern.

[00136] In one embodiment of the invention, the oscillating wall parts may present a phase difference with respect to each other. In this way, a lagged pattern of wall parts is obtained each time. With this, it is also possible to obtain the advantage according to the present invention.

[00137] Figure 5 shows a schematic view of an apparatus for forming the structure on an anilox roll according to an embodiment of the invention. Here, a laser is used 60. The laser is part of an engraving unit 61. The engraving unit is positioned along the longitudinal axis 62 of the anilox roll 63. The anilox roll 63 is shown schematically only. The figure is not drawn to scale. The recording unit is positioned in a frame (not shown), and the frame allows movement of the recording unit along the anilox roll 63 in accordance with arrow 62. Suitable guide device such as a guide track can be applied.

[00138] The anilox roll 63 is positioned in a container that is supported on bearings and connected to the frame. In this way, the anilox roll can rotate around the longitudinal geometric axis 62 in accordance with the arrow 64. The combination of both rotation around the geometric axis 62 and movement along the geometric axis 62 allows work by engraving the outer surface complete with laser. The constructions to manufacture, more specifically engraving the anilox roll according to the cutting-edge technology available using these movements, allow work with accuracies of less than 1 micrometer. This among others allows wall parts according to embodiments of the invention to be formed with a size of less than 5 micrometers. The method allows channels to be formed on the surface of the anilox roll. Material in the channels is evaporated, while parts of the wall remain.

[00139] The laser beam can be concentrated at a focus 69 on the external surface 70 of the anilox roll 63 by means of known optical guides 65-68, which, in this embodiment, are formed by four corner mirrors. In the position where the focus is formed, a certain amount of heat is concentrated, in such a way that a piece of material on the outer surface of the anilox roll evaporates. This material may be a ceramic composition, such as chromium oxide. Those skilled in the art will be familiar with the different compositions and/or compounds.

[00140] By focusing the focus, it is possible to evaporate a part of the outer surface of the anilox roll. In a preferred embodiment of the invention, a continuous laser 60 is used. The synchronization of the laser pulses with rotational and longitudinal movements is more continuous. More specifically, it is possible to form a continuous track of evaporated material on the anilox roll 63 using a continuous laser together with continuous movements of the roll and/or engraving unit, thereby forming a channel. It is possible to form a continuous track at a high speed. The speed is limited only by the laser power.

[00141] In a further embodiment of the invention, the beam 71 of the laser 60 is influenced by an optical guide in the path between the laser 60 and the focus 69. The optical guide 72 can cause an alternating movement 73 of the focus entirely on the surface to be be recorded. As a result, the focus will repeatedly execute an identical movement, preferably at a continuous speed. This movement, together with the rotation of the anilox roll, can lead to continually changing the focus location. Preferably, the reciprocating movement results in a shift 73 of focus in a direction that is parallel to the longitudinal geometric axis of the anilox roll. A change like this in combination with a continuous laser can be, for example, used to form a pattern of channels according to figure 3b.

[00142] Preferably, the reciprocating movement is a sinusoidal or wave-like movement. The movement can be governed mechanically or electronically. In a preferred embodiment shown in Figure 5, a combination of a crystal 74, on the one hand, and a voltage supplied by a power supply 75, on the other hand, is used. Voltage is supplied to crystal 74 to cause a change in the beam trajectory, more specifically an eventual change in focus. The tension supplied, for example, is repetitive, making the focus also repetitive. A control unit 76, for example, is provided in the electrical connection between the crystal 72 and the source 75. The control unit is capable of adjusting the supplied voltage. The control unit may be connected to an external controller to synchronize the crystal tension with the rotation 64 of the anilox roller 63 and the movement 62 along the anilox roller 63 of the recording unit as a whole.

[00143] The change in tension can be synchronized with the rotation of the anilox roll. The change in voltage is, for example, characterized by parameters such as amplitude and frequency. These two parameters may be related to the amount of change and repetition of the alternating movement, respectively.

[00144] In the embodiment shown, a tellurium dioxide crystal 74 can be used, for example. The crystal works as a deflector. By changing the voltage between 0 V and 10 V, the transmission properties of the crystal change. The aforementioned crystal works among others at 1,064 nm.

[00145] Other modalities of generating devices and optical guides are also possible. It is also possible to make use of a mobile mirror. In another embodiment, an interference effect can be used to generate alternating focus movement.

[00146] Another technique that is known to make use of such oscillation of a channel formed on an external surface is a technique for forming DVDs. The inventor is aware that a technique known in this technical field can be used to form a pattern such as this on an external surface.

[00147] Variations in the modalities of the different profiles are conceivable, without departing from the main notion of the invention. It may be clear that the invention is described using preferred embodiments. The invention should not be limited to these embodiments.

[00148] According to a further aspect, the following clauses are provided. Clause 1, a method for forming an anilox roll, comprising providing an anilox roll cylinder having an outer surface to be worked, providing at least one laser source and laser engraving the outer surface of the anilox roll with a focus laser which is formed by a laser source to obtain a worked anilox roll, wherein the method further comprises applying an optical guide to the laser light path to allow the laser focus to move alternately on the outer surface to be worked on.

[00149] Clause 2: a method according to clause 1, in which the laser focus generally moves with a constant speed entirely on the outer surface of the anilox roll. Clause 3, a method according to clause 1 or 2, wherein the reciprocating movement causes a change of laser focus on the anilox roll in a direction that is basically parallel to a longitudinal geometric axis of the anilox roll. Clause 4: method according to any of clauses 1, 2 or 3, wherein the change is at least greater than the width of the laser focus in the same direction. Clause 5: method according to any of the preceding clauses, wherein the laser engraving step further comprises rotating the anilox roll around a longitudinal geometric axis of the anilox roll, as well as moving the laser in a basically parallel direction to the longitudinal geometric axis of the anilox roll.

[00150] Clause 6: method according to any of the previous clauses, wherein the laser source is a continuous laser source, wherein a channel is formed on the outer surface of the anilox roll because of laser engraving, wherein the channel extends in a rotational direction of the anilox roll.

[00151] Clause 7: apparatus for forming an anilox roll to be used in a printing process, comprising a support unit for supporting the cylinder-shaped anilox roll and for rotating the anilox roll around a geometric axis longitudinal; an engraving unit that is arranged for parallel movement with respect to an axis of the cylinder of the anilox roll to engrave a structure on the outer surface of the anilox roll, and a drive unit for actuating engraving adjustments of the engraving unit, wherein the engraving unit comprises at least one laser source for laser engraving the outer surface of the anilox roll with a laser focus, wherein the engraving unit further comprises an optical guide for moving the laser focus in a repetitive manner . Clause 8: apparatus according to clause 7, wherein the optical guide is arranged to move the laser focus entirely on the outer surface of the anilox roll with a generally constant speed. Clause 9: apparatus according to clause 7 or 8, in which the optical guide is a deflector. Clause 10 apparatus according to any one of clauses 7, 8 or 9, wherein the optical guide comprises a crystal, which is connectable to a power supply, wherein the crystal is arranged to deflect the incoming light beam depending on the applied voltage. Clause 11: apparatus according to any of clauses 7-10, wherein the optical guide is movably connected to the recording unit. Clause 12: apparatus according to clause 11, wherein the optical guide is connected to the recording unit by means of a movement unit, and wherein the movement unit is arranged to allow the laser focus to move in a manner alternated. Clause 13: apparatus according to any one of clauses 7-12, wherein the repetitive change comprises a movement of the laser focus in a direction basically parallel to the geometric axis of the cylinder. Clause 14: apparatus according to any of clauses 7-13, wherein the change is at least greater than the width of the laser focus in the same direction. Clause 15: apparatus according to any of clauses 7-14, wherein the reciprocating movement of the laser focus is at least 20 µm. Clause 16: apparatus according to any one of clauses 7-15, wherein the laser source is a continuous laser source, wherein the drive unit is connected to the support unit and the motion unit, and wherein the drive unit is drive is arranged to rotate the anilox roll during laser engraving with an alternating movable focus. Clause 17: apparatus according to any of clauses 7-16, wherein the recording unit comprises an objective lens.

Claims (17)

1. Anilox roller (5) for a printing apparatus for transferring a fluid, such as an ink, comprising a cylinder having a surface (100), wherein the surface comprises a fluid distribution structure for receiving the fluid, distributing the fluid entirely in the cylinder and transferring the fluid, wherein the fluid distribution structure is arranged to transfer, in a first operating mode for printing heavy layers of ink, a relatively large droplet of fluid and, in a second operating mode for print details, a relatively small fluid droplet through a combination of constraints on the fluid distribution structure, the fluid distribution structure having a channel (24) formed on the surface to distribute the fluid entirely into the fluid distribution structure, the channel (24) having a waveform with a sinuous repetitive pattern over the surface, characterized by the fact that: the channel (24) has a constant channel width; and both the channel and the channel walls have a sinusoidal waveform. 2. Anilox roll according to claim 1, characterized in that the winding channel (24) has an amplitude that is generally equal to, preferably greater, than the width of the channel. 3. Anilox roller according to any one of claims 1 or 2, characterized in that the fluid distribution structure for the second operating mode comprises channel parts (601-605) that are formed in the channel (24), wherein the channel portions have a droplet volume suitable for printing details. 4. Anilox roller according to any one of claims 2 or 3, characterized in that channel parts (601605) connected with a course direction are positioned in such a way that the courses are at an angle with respect to each other to prevent linear distribution of the fluid to be received in the channel parts, and to allow a sinuous distribution of the fluid to be received in the channel (24, 600). 5. Anilox roll according to any one of claims 3 or 4, characterized in that the channel parts have a generally constant width. 6. Anilox roll according to any one of claims 1 to 5, characterized in that the channel has a generally flat base with a generally equal channel depth, wherein preferably the base has a substantially constant height level difference with respect to the surface of the anilox roll. 7. Anilox roll according to any one of claims 1 to 6, characterized in that the channel walls (25, 26, 27) are positioned relative to a location in the fluid distribution structure at a radial distance of maximum 100 µm, preferably less than 80 µm. 8. Anilox roll according to any one of claims 1 to 7, characterized in that a second channel is provided adjacent to the first channel, the second channel having a course generally parallel to the first channel. 9. Anilox roll according to claim 8, characterized by the fact that the walls (25, 26, 27) between the first and second channels have a width of less than 4 µm, preferably in the range of 1-3 µm. 10. Anilox roll according to any one of claims 1 to 9, characterized in that the channel walls of the winding channel are positioned generally antisymmetrically with respect to a direction of travel of the channel. 11. Anilox roll according to any one of claims 1 to 10, characterized in that the channel extends completely on the outer surface of the anilox roll. 12. Anilox roll according to any one of claims 1 to 11, characterized in that the channel wall cells have the shape of a sine wave or a serrated shape. 13. Anilox roll according to any one of claims 1 to 12, characterized in that a baseline of the channel is at an angle ß with respect to the circumferential direction of the anilox roll. 14. Anilox roll according to any one of claims 1 to 13, characterized in that the channel has a U-shaped cross section. 15. Printing apparatus comprising a printing device with a supply for a substrate to be printed and a supply for ink, characterized in that the printing device comprises the anilox roll defined in any one of claims 1 to 14 assembled in a bearing. 16. Method for forming an anilox roll (5, 63) comprising providing an anilox roll cylinder having an outer surface (70, 100) to be worked, providing at least one laser source (60) and laser that engraves the outer surface of the anilox roll with a laser focus (69) that is formed by the laser source (60) to obtain a worked anilox roll, characterized by the fact that: the laser source (60) is a source continuous laser; and the method further comprises applying an optical guide (72) to the laser light path to allow the laser focus to move reciprocally (73) on the outer surface to be worked, so as to form a channel (24) on the surface outside of the anilox roll, the channel (24) winds entirely on the surface. 17. Apparatus for forming an anilox roll (5, 63) for use in a printing process comprising a support unit for supporting the cylinder-shaped anilox roll and for rotating the anilox roll about an axis longitudinal geometric; an engraving unit (61) that is arranged for parallel movement with respect to a geometric axis of the cylinder (62) of the anilox roll to engrave a structure on the outer surface (70, 100) of the anilox roll, and a drive unit to actuate the engraving settings of the engraving unit (61), wherein the engraving unit comprises at least one laser source (60) for laser engraving the outer surface of the anilox roll (5, 63) with a focus of laser (69), characterized by the fact that: laser source (60) is a continuous laser source; and wherein the recording unit further comprises an optical guide (72) for moving the focus of the continuous laser reciprocally so that it forms a channel (24) on the outer surface of the anilox roll (5, 63), the channel (24) winding entirely on the surface.