Flexographic printing and engraving roller for photogravure printing

Abstract

To provide a roller to be used together with a printing device.SOLUTION: A roller includes a cylinder comprising an engraving surface having a channel engraving pattern including a linear cell. The channel engraving pattern including the linear cell has: a linear channel having a channel wall; and a plurality of cells arranged inside the linear channel and comprising pockets having different cell wall depths. The total channel depth of the linear channel is equal to a depth obtained by adding a free flow liquid channel depth to the cell wall depth. The free flow liquid channel is a portion of a channel existing in an upper part of the cell wall and inside the channel.SELECTED DRAWING: Figure 1A

Description

[Technical Field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This application claims priority in the United States Patent and Trademark Office to U.S. Provisional Patent Application No. 62 / 896264, filed September 5, 2019, and U.S. Utility Patent Application No. 17 / 011104, filed September 3, 2020, the disclosures of which are incorporated herein by reference in their entireties.

[0002] The present invention relates to rollers having engraved patterns for flexographic and gravure printing. [Background technology]

[0003] Many open-cell engravings exist in the flexographic printing industry, but none offer the combination of "full ink carry," moiré resistance, and UV spitting resistance. Moiré is an interference pattern caused by the collision of an imaged printing plate screen with an engraved screen on the anilox (liquid transfer) roller. "Full carry" refers to the ability to completely fill the cells without impairing transfer efficiency. UV spitting is due to the buildup of heavy solids that collect from the blade / anilox contact area and cause problems. Other channel engravings can meet one or two of the above criteria, but none offer the remedy for all three.

[0004] UV spitting is a particularly troublesome aspect of flexographic and gravure printing. The process of flooding an anilox roll with ink and using a doctor blade to scrape off excess ink and transfer a consistent ink film is fundamental to flexographic printing. However, a recurring challenge for flexographic presses is UV ink spitting. Spitting can generally be described as ink leaking from the area of the blade / anilox contact point. As it passes through the blade, the ink pools on the other side of the blade. As the ink accumulates, it drips, causing print defects, typically in the form of randomly placed teardrops on the printed image.

[0005] Therefore, there is a need for a roller having a sculptured surface that overcomes the above-mentioned drawbacks and problems. Summary of the Invention

[0006] The present invention relates to laser engraved rollers for use in flexographic and gravure printing, channel engraved patterns containing linear cells, and methods for using them to reduce spits during printing.

[0007] In one embodiment of the present invention, a roller having an engraved surface for use with an apparatus for transferring a liquid to a printing plate or substrate is provided, the roller comprising a cylinder having an engraved surface with a channel engraved pattern including linear cells, the channel engraved pattern including linear channels at a channel engraved angle and a plurality of cells arranged within the linear channels with pockets at a cell pocket arrangement angle.

[0008] In one embodiment of the present invention, an engraved pattern on the surface of a roller is provided for use with an apparatus for transferring a liquid to a printing plate or substrate having an engraved channel pattern with linear cells, the engraved channel pattern having linear channels at a channel engraving angle and a plurality of cells with pockets at a cell pocket arrangement angle.

[0009] In one embodiment of the present invention, a method for using a roller to reduce spitting during printing is provided, the method comprising providing a printing apparatus having a roller, also referred to as a cylinder having an engraved surface, the engraved surface having a channel engraved pattern including linear cells, the linear cells having linear channels at a channel engraving angle and a plurality of cells with pockets at a cell pocket placement angle, for transferring liquid from the engraved surface of the roller to a printing plate or substrate.

[0010] Further areas of applicability of the present invention will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are intended for purposes of illustration only and are not intended to limit the scope of the invention.

[0011] The present invention will become more fully understood from the detailed description and accompanying drawings, which are not necessarily to scale. [Brief explanation of the drawings]

[0012] [Figure 1A] 1 shows a roller for use in flexographic and gravure printing applications according to the present invention; [Figure 1B] 1B shows another view of the roller of FIG. 1A. [Figure 2] 1 illustrates another type of roller called a sleeve for use in flexographic and gravure printing applications according to the present invention. [Figure 3] The cells with cell walls and the cell wall depth are shown. [Figure 4] FIG. 10 shows an image of the geometric angle of engraving according to the present invention with a channel engraving angle of 120 degrees and a cell pocket placement angle of 60 degrees. [Figure 5A] 10 is a cross-channel slice image of a 60° channel depicted by a white light image. [Figure 5B]5B is a histogram showing the relationship of total channel depth to cross-channel cell (pocket) wall depth from the channel bottom for the channel of FIG. 5A. [Figure 6A] 1 shows an image of a slice line through the middle of the channel in a white light image, and a histogram showing cell (pocket) wall depth and number of cells per linear inch relative to total channel depth. [Figure 6B] 6B is a histogram showing cell (pocket) wall depth and number of cells per linear inch relative to total channel depth for the channels of FIG. 6A. [Figure 7A] 3D image with histogram created from data obtained by measuring the volumetric and geometric features of a ceramic engraved anilox roller. [Figure 7B] The histogram of FIG. 7A. [Figure 8A] 7B is the 3D image of FIG. 7A, with the image inverted to view the cell from the bottom up. [Figure 8B] The histogram of FIG. 8A. [Figure 9] FIG. 7B is another view of the 3D image of FIG. 7A. [Figure 10] This is a white light image with a 60 degree channel. [Figure 11A] This is a white light image. [Figure 11B] The histogram of FIG. 11A. [Figure 12A] In order to provide a close-up, the image has lines drawn over fewer cells in the white light image. [Figure 12B] The histogram of FIG. 12A. [Figure 13A] In the white light image, the channel itself has a line drawn through it. [Figure 13B] The histogram of FIG. 13A. [Figure 14A] Images of three cell lines in a 120 degree channel in white light images. [Figure 14B] The histogram of FIG. 14A. [Figure 15A] 10 is an image of a second position of a line drawn across the channel in the white light image. [Figure 15B] The histogram of FIG. 15A. DETAILED DESCRIPTION OF THE INVENTION

[0013] The following description of embodiments of the present invention is merely exemplary in nature and is in no way intended to limit the invention, its application, or uses. The following description is provided herein by way of example only for the purpose of providing an enabling disclosure of the invention, but is not intended to limit the scope or substance of the invention.

[0014] Referring to the figures, Figure 1A shows an engraved roller 100 for use in flexographic and gravure printing applications according to the present invention. Figure 1B is another view of the engraved roller of Figure 1A. The engraved roller 100 is used with a printing apparatus to transfer liquid to a printing plate or substrate. Preferably, the roller is an anilox roller used in flexographic printing. The roller can have one or more bands of various engravings.

[0015] FIG. 2 shows another type of engraved roller 200, called a sleeve, for use in flexographic and gravure printing applications according to the present invention. Engraved rollers 100 and 200 have engraved surfaces 20. However, engraved rollers 100 and 200 are mounted differently in the printing apparatus. Engraved roller 100 has a journal, while engraved roller 200 is hollow and has multiple designs that allow the hollow roller to be mounted in a self-centering manner. Both types of rollers can be used in flexographic and gravure printing applications according to the present invention.

[0016] Engraved rollers 100 and 200 are each coated with ceramic and other coatings or materials. The engraved surfaces are preferably laser engraved. Coating materials include, but are not limited to, ceramic, metal, and any other laser-engravable material.

[0017] The engraved surface 20 has a plurality of linear channels and a plurality of cells within each linear channel. The engraved surface slows the flow of liquid. A liquid is any material with a viscosity that allows it to flow through linear channels. Examples of liquids include, but are not limited to, ink, adhesives, varnishes, including special effect varnishes, and primers. The cells are preferably evenly spaced within a given linear channel. As shown in Figure 3, the cells have cell pockets that function as liquid-retaining wells. The number of evenly spaced cells can vary depending on the application and can range from 10 to 5,000 cells (pockets) per linear inch. Each cell is defined by two cross-channel walls that are lower than and perpendicular to the channel walls. Channel structures containing linear cells can be configured and engraved in patterns ranging from 30° to 150° relative to the axial direction of the coated cylinder. Channel structures containing linear cells can also be configured and engraved in patterns ranging from 30° to 89° and / or 91° to 150° relative to the axial direction of the coated cylinder. The linear channels at a fixed measurement angle for a given roller utilize a hexagonal base cell profile. The pockets at the bottom of the cells are formed by partitions with cell wall depths ranging from 20% to 80% of the total channel depth, with approximately 40% to 60% of the total channel depth being preferred. The total channel depth is equal to the cell wall depth plus the free-flow liquid channel depth. The free-flow liquid channel refers to the portion of the channel above the cell walls but within the channel where liquid flows freely. The free-flow liquid channel depth and the total channel depth are shown in the histograms shown in the figures herein.

[0018] The achievable volume of liquid available for transfer to the printing plate or substrate is measured in Billion Cubic Microns per Square Inch (BCM), the amount of BCM relating to the number of engravable cells (pockets) per linear inch that can be formed in the engraved surface and maintain cell cross-channel walls in the range of 20% to 80% of the total channel depth.

[0019] In the present invention, there is a relationship between the channel engraving angle and the cell (pocket) placement angle. The channel engraving angle can be in the range of 30° to 150°, with the cells having walls that move across the channel to capture and retain liquid. Alternatively, the channel engraving angle can be in the range of 30° to 89° and / or 91° to 150° (degrees). Since the cell (pocket) placement angle is in the range of 20% to 80%, preferably 40% to 60%, of the channel engraving angle, the cell (pocket) placement angle is essentially determined by the channel engraving angle (30° to 150°) or (30° to 89° and / or 91° to 150°).

[0020] Figure 4 shows the geometric angles of the engraving with a channel engraving angle of 120 degrees and a cell pocket placement angle of 60 degrees. In the example shown in Figure 4, the channel angle is shown at 120° measured as the difference between the angle vector and the axis of the anilox. As shown in Figure 4, the cross point is located within the cell pocket (well).

[0021] The pockets allow for controlled liquid flow as the cells fill. The linear cell-containing channel engraving pattern of the present invention provides hydraulic relief for the liquid by keeping the liquid flowing as the cells fill and transferring the liquid to the printing plate or substrate. Without pressure relief, collected solids would adhere to the doctor blade, which is metering the liquid from the roller surface. As more liquid accumulates at the blade edge and its surface energy is able to maintain, "spitting" (a process that repels ink from the blade / roller contact area) can be randomly released onto the plate or substrate surface, resulting in printing defects. Another advantage of the linear cell-containing channel engraving pattern of the present invention is that it provides a slim profile against the formation of moiré patterns (printing interference between the printing plate or substrate and the roller cell angle).

[0022] Thus, the present invention provides laser or other engraving of ceramic or other engravable materials, while providing hydraulic relief for UV inks and other liquids without sacrificing transfer properties or increasing the likelihood of moiré. The functionality of the cell profile allows for increased run speeds without increasing the likelihood of UV ink spitting. Channel engraving patterns containing linear cells also reduce foaming in adhesives and varnishes, which are prone to generating microbubbles from agitation. Other printing applications, such as particle inks, can also benefit from cell channel flow technology.

[0023] The engraved rollers and engraved patterns of the present invention provide a consistent low cross-channel wall height and a consistent cell bottom profile without interfering with the substrate image angle required for liquid-carrying plates or printing, while maintaining "carry" and volume targets (both characteristics of closed-cell engraving). Unlike current technology, the engraved rollers of the present invention provide straight channels at the engraving angle, resulting in consistent transfer of ink and other liquids to conventional angled imaged printing plates or substrates. Other benefits of the engraved rollers and engraved patterns of the present invention include flexographic and gravure printing without pinholes and increased opacity. Depending on the plate or substrate and surface, the engraved rollers and engraved patterns of the present invention can also aid in liquid laydown.

[0024] In one embodiment of the present invention, a method for using a roller to reduce spitting during printing is provided, comprising providing a printing apparatus having a roller with a cylinder having an engraved surface, the engraved surface having a channel engraving pattern including linear cells with linear channels at a channel engraving angle and a plurality of cells with pockets at a cell pocket placement angle, and transferring ink or other liquid from the engraved surface of the roller to a printing plate or substrate. [Example]

[0025] A 3D QC microdynamics interferometer measurement system was used to measure the volumetric and geometric characteristics of a ceramic engraved anilox roller according to the present invention. The resulting data and images and histograms prepared from the scans are shown in Figures 5A-15B.

[0026] Figure 5A is an image of a cross-channel slice of a 60° channel depicted by a white light image. Figure 5B is a histogram showing the relationship between total channel depth and cross-channel cell (pocket) wall depth from the channel bottom for the channel of Figure 5A. Referring to Figures 5A and 5B, which depict a slice perpendicular to the channel across the channel, the difference between the "channel top" and the "cross-channel cell wall top" is the free liquid flow channel, and the difference between the "cross-channel cell wall top" and the "cell (pocket) bottom" is the pocket that blocks flow.

[0027] FIG. 6A is an image of a slice line through the middle of a channel in a white light image, as well as a histogram showing the cell (pocket) wall depth and the number of cells per linear inch relative to the total channel depth. FIG. 6B is a histogram showing the cell (pocket) wall depth and the number of cells per linear inch relative to the total channel depth for the channel of FIG. 6A. Referring to FIGS. 6A and 6B, by drawing a slice parallel to the channel through the middle of the channel, the relationship between the liquid trapping cells (pockets) and the top of the channel wiped by the doctor blade is shown. The cell pockets within the channel are unique.

[0028] Figure 7A is a 3D image with a histogram created from data obtained by measuring the volumetric and geometric features of a ceramic engraved anilox roller. Figure 7B is the histogram of Figure 7A. Referring to Figures 7A and 7B, which depict axial slices, 3D QC constructs an approximate composite profile.

[0029] Figure 8A is the 3D image of Figure 7A, with the image inverted to view the cells from the bottom up. Figure 8B is a histogram of Figure 8A. Referring to Figures 8A and 8B, which depict axial slices of the roller, 3DQC constructs an approximate composite profile. In this figure, the composite is the same as the previous figure, even though the view is from the bottom up.

[0030] Figure 9 is another view of the 3D image of Figure 7A, showing the channel walls, cross-channel cell walls, and cell pockets.

[0031] Figure 10 is a white light image with a 60 degree channel, showing the channel walls, cross-channel cell walls, and cell pockets.

[0032] Figure 11A is a white light image. Figure 11B is a histogram of Figure 11A. Referring to Figures 11A and 11B, a slice line is drawn through the cell pocket to show the total depth of the cell compared to other cells in the channel as the channel itself weaves across and around the roller.

[0033] Figure 12A is a white light image with lines drawn over fewer cells to provide a close-up. Figure 12B is a histogram of Figure 12A. Referring to Figures 12A and 12B, a slice line is drawn through only three cell pockets to show the total depth and proportion of the cells relative to other cells in the channel as the channel itself weaves across and around the roller.

[0034] Figure 13A is a white light image with lines drawn through the channel itself. Figure 13B is a histogram of Figure 13A. Referring to Figures 13A and 13B, Figure 13 is similar to Figure 6B, except that a slice is taken through the center of the channel parallel to the channel, through seven cell pockets instead of the nine cell pockets of Figure 6B, and shows the liquid trapping cells (pockets) at different proportions.

[0035] Figure 14A shows an image of three cell lines in the 120-degree channel in a white light image. Figure 14B shows a histogram of Figure 14A. Figures 14A and 14B show the same view as Figure 6B, except that only three cells are shown so that they can be profiled in more detail.

[0036] Figure 15A is an image of a second position of a line drawn across the channels in a white light image. Figure 15B is a histogram of Figure 15A. Referring to Figures 15A and 15B, Figure 15B is similar to Figure 5B, except that a slice was taken perpendicular to the channels through seven channels to show the depth difference between the cross-channel wall and the cell pockets.

[0037] Other experiments have been conducted to determine laser engraving parameters for consistent and controlled linear engraving. Actual print tests using banded and single-band anilox rollers have been conducted and successfully compared to standard 60-hexagon closed cell engraving. Comparisons of printed products have been made for 30-degree and non-linear channel engraving.

[0038] Thus, it will be readily apparent to those skilled in the art that the present invention is susceptible of broad utility and application. Many embodiments and adaptations of the present invention other than those described herein, as well as numerous variations, modifications, and equivalent arrangements, will be apparent from, or will be reasonably suggested by, the present invention and the foregoing description thereof, without departing from the spirit or scope of the present invention. Accordingly, while the present invention has been described in detail herein with reference to preferred embodiments thereof, it should be understood that this disclosure is merely illustrative and exemplary of the invention and is made solely for the purpose of providing a complete and enabling disclosure of the invention. The foregoing disclosure is not intended or construed to limit the invention or otherwise exclude such other embodiments, adaptations, variations, modifications, and equivalent arrangements.

Claims

1. 1. A roller for use with a printing device, comprising: a cylinder having an engraved surface with a channel engraved pattern including linear cells; The channel carving pattern including the linear cells includes a linear channel having a channel wall, and a plurality of cells arranged in the linear channel, the cells including pockets with different cell wall depths, a total channel depth of the linear channel equals the cell wall depth plus a free-flow liquid channel depth, the free-flow liquid channel being the portion of the channel above the cell walls and within the channel.

2. A cylinder, A channel carving pattern including linear cells having linear channels with channel walls and a plurality of cells with pockets having different cell wall depths, a total channel depth of the straight channel equal to the cell wall depth plus a free-flow liquid channel depth, the free-flow liquid channel being the portion of the channel above the cell walls and within the channel;

3. 1. A method of using a roller to reduce spitting in printing, comprising: A printing device having a roller, the roller comprises a cylinder having an engraved surface; the engraved surface has a channel engraved pattern including linear cells, the linear channels having channel walls, and a plurality of cells arranged in the linear channels and including pockets with varying cell wall depths; providing a printing device wherein a total channel depth of the linear channel is equal to the cell wall depth plus a free-flow liquid channel depth, the free-flow liquid channel being the portion of the channel above the cell wall and within the channel; transferring a liquid from the engraved surface of the roller to a printing plate or substrate; A method comprising:

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