MXPA99000388A - Composite plates of printing of image of relieve and methods to prepare the mis - Google Patents

Abstract

High-quality composite printing elements are prepared without the need for precise registration of constituent photocurable elements by arranging at least one photocurable element, and preferably a plurality of photocurable elements, on a surface of a substantially flat carrier sheet in approximate registration and then transfer a computer-generated negative on a surface of the elements

Description

COMPU PLATES ARE PRINTED OF RELIEF IMAGE AND • _ • METHODS TO PREPARE THE SAME FIELD OF THE INVENTION The present invention is directed to the preparation of composite printing plates and, more particularly, to the direct transfer of digital images to such compounds without the use of photo-tools or photo-masks.

BACKGROUND OF THE INVENTION Emboss image printing plates are used in both flexographic and typographic processes to print on a variety of substrates, including paper, corrugated cardboard, film, sheets, and laminates. The photocurable elements that are used to make plates of Embossing typically includes a backing layer and one or more layers of photocurable polymer in the form of solid sheets. The printer typically removes a cover sheet from the element to expose the photocurable polymer and places a photographic negative of silver halide or some other masking device on the photo polymer. The photocurable element that carries the negative is then exposed to ultraviolet (UV) light through the negative, thereby causing the exposed areas of the element to harden, or cure. After the uncured areas of the element are removed, the cured polymer remains as the embossing surface. 25 Corrugated boxes and other relatively large objects that are They print using embossed image printing plates often hold real print on only a small portion of their total surface area. One way of printing such an object is to prepare a simple relief image plate having a surface area corresponding to the total surface area of the object. Since only a portion of the surface of the object needs to be printed, however, only a portion of the relief image plate will actually be used for ink transfer. The rest of the plate will not be used and, essentially, wasted. To minimize such waste, those skilled in the art often print relatively large objects with composite printing plates that are prepared by mounting a plurality of relief image printing plates on a common carrier sheet. The individual plates, however, are mounted only on those portions of the carrier that correspond to the portions of the object that really need to be printed. Although such composite plates minimize waste, the current system for assembling their constituent image relief plates is laborious and requires careful adhesion of the plates to the carrier at the same time as ensures registration within 0.0.0127 cm in the press for high quality printing and multicolor reproduction. For multicolored reproduction, where a single plate is used to print each of the individual colors, the precise registration of the plates with respect to each other is crucial. 25 Consequently, there remains a need in the art of Alternate processes to prepare composite printing plates. In particular, there remains a need for alternate processes for accurate registration of the constituent plates of relief image printing or for processes where precise registration is not necessary. OBJECTIVES OF THE INVENTION It is an object of the present invention to provide methods for preparing composite printing plates. It is another object of the invention to provide methods for recording at least one relief image printing plate on a common carrier sheet. It is a further objective to provide methods for printing registration information directly on the surface of the carrier sheet using a computer. It is still another objective to provide methods for transferring an electronically stored negative image directly onto a composite printing plate.

BRIEF DESCRIPTION OF THE INVENTION These and other objects are satisfied by the present invention, which provides methods for preparing composite printing plates of high quality without the need for individual registration of constituent plates of relief image. These methods comprise the steps of having a photocurable element on a surface of a substantially flat carrier sheet in an approximate register and then transferring a negative generated by computer over element. In Preferred embodiments, the methods of the invention comprise the steps of providing at least two substantially flat photocurable elements having first and second opposed main faces of defined surface area, arranging a first face of the photocurable elements on a first face of a carrier sheet substantially flat having first and second opposed major faces of defined surface area, and ejecting the negative forming ink from an ink jet print head onto the second faces of said photocurable elements. The approximate recording of the photocurable elements can be achieved by transferring computer generated record information to a surface of the carrier sheet through ejection of ink from an ink jet print head onto the sheet. The registration information may comprise, for example, a series of images whose respective shapes correspond to the contours of the individual photocurable plates. Following the transfer of registration information, the photocurable elements are placed on the carrier sheet according to the positions dictated by the registration information. The transfer of the computer generated negative to the composite plates of the invention is preferably achieved by ejecting a negative forming ink from an ink jet print head. The ink is preferably substantially opaque to actinic radiation in at least one wavelength region effective to cure photo-curable material within the element and substantially resistant to polymerization by exposure to actinic radiation in the wavelength region. Following the negative transfer step, the ink carrier plate can be exposed to actinic radiation in the wavelength region for a time and under effective conditions to cure exposed areas of the photocurable material, 5 and then the non-exposed areas (ie say, uncured) are removed to provide the relief printing surface. The present invention further provides negative carrier composite printing plates produced according to the above methods. In certain embodiments, the plates comprise a plurality of photocurable elements arranged in a substantially planar carrier sheet, at least two of the photocurable elements including a support layer, photocurable material disposed on the support layer, and negative forming ink disposed on at least a portion of the surface of the photocurable material. BRIEF DESCRIPTION OF THE DRAWINGS The numerous objects and advantages of the present invention can be better understood by those skilled in the art by reference to the accompanying non-scale figures, in which: Figure 1 is a top view of a carrier sheet that will read registration information. Figure 2 is a top view of a printing composite plate according to the invention. Figure 3 is a cross-sectional view of a composite printing plate according to the invention.

Figure 4 is a plan view of a printing apparatus for composite printing plates.

DETAILED DESCRIPTION OF THE INVENTION The present invention provides methods that eliminate the tedious requirement of having to register by hand individual emboss printing plates when preparing composite printing plates of high quality. Although the methods of the invention can be used to prepare printing plates of any size, they are particularly useful for preparing relatively large printing plates (i.e., those having length and / or width greater than about 76.2 centimeters). In the methods of the invention, the photocurable elements of the appropriate sizes required (or of slightly larger sizes than the required sizes) are mounted on a carrier sheet in approximate register with the areas to be printed ultimately. The precise "registration" of the elements is then achieved by applying a negative image generated by computer to the composite plate via an ink jet printer. Composite printing plates according to the invention are preferably prepared by first printing computer generated record information on one side of a suitable carrier sheet. The carrier sheet will be substantially flat (ie, its length and width will be substantially greater, preferably at least ten times greater, than its thickness and will have two, substantially planar opposed main faces) and can be formed from a transparent or opaque material such as paper, cellulose film, plastic, or metal. In preferred embodiments, the carrier sheet is a polyethylene terephthalate film having a thickness in the order of about 0.01 to 0.127 centimeters. As shown in Figure 1, the registration information printed on the carrier sheet 10 may include complete contours (eg, 12, 13) of the photocurable elements to be assembled, incomplete contours corresponding, for example, to the corners, sides , or arcs of the photocurable elements (see, 16, 17, and 18 respectively), or any other suitable signal that is used to direct the placement of the elements during the assembly process. As shown in Figure 2, a composite printing plate 1 1 according to the invention can be formed by mounting light-curing elements 20 on one side of the carrier sheet 10 in accordance with the registration information, ie in the indicated positions by the contours and / or printed marks. The photocurable elements can be assembled using any of the many means known to those skilled in the art. Preferred mounting means involve caulking with silicone, double-sided tape, or some other suitable adhesive to the carrier sheet, or both. The elements do not need to be mounted with any particular degree of precision. All that is required is for the photocurable elements to be mounted on those portions of the composite plate that will ultimately support relief images. According to the invention, the photocurable elements cover less than the entire surface area of the face of the carrier sheet on the which are mounted. Stated differently, the photocurable assembled elements preferably have a cumulative surface area of less than 100% of the surface area of the face of the carrier sheet. There is a wide variety of photocurable elements that can be used according to the invention. In preferred embodiments, the elements are solid and vary in thickness from about 0.0635 to about 0.635 centimeters and have dimensions of up to about 132 centimeters to about 203.2 centimeters. As shown in Figure 3, a preferred photocurable element 20 comprises a support layer 22, one or more photocurable layers 24, 26 and a removable cover sheet 28. Such photocurable elements optionally comprise a transparent protective layer 27 disposed between the cover sheet and the photocurable layer (s). Also shown in Figure 3 is the adhesive 23 for mounting the element 20 on the carrier sheet 10. The support, or backing, layer of the photocurable element may be formed of a transparent or opaque material such as paper, cellulose film, plastic or metal. In preferred embodiments, it is a polyethylene terephthalate film having a thickness in the order of 0.0127 centimeters. The support optionally carries an adhesive for more secure attachment to the photocurable layer. The photocurable layer, which generally has a thickness of approximately 0.0508 to 0.889 centimeters, may include a variety of photopolymers, initiators, reactive thinners, fillers, and colorants known. Preferred photocurable materials include an elastomeric compound, an ethylenically unsaturated compound having at least one terminal ethylenic group, and a photoinitiator. Exemplary photocurable materials are described in European Patent Applications 0 456 336 A2 (Goss et al.) And 0 640 878 A1 (Goss et al.), British Patent No. 1, 366,769, and US Patent Nos. 5,223,375 (Berrier et al.), 3,867, 153 (MacLahan), 4,264,705 (Alien), 4,265,986 (Alien), 4,323,636 (Chen, et al.), 4,323,637 (Chen, et al.), 4,369,246 (Chen, et al.) , 4,423, 135 (Chen, et al.), And 3,256,765 (Holden, et al.), 4,320, 188 (Heinz, et al.), 4,427,759 (Gruetzmacher, et al.), 4,460,675 (Gruetzmacher, et al.), 4,622,088 (Min), and 5, 135,827 (Bohm, et al.), Which are incorporated herein by reference. If a second photocurable layer is used, it is typically disposed on the first and is similar in composition but considerably thinner, usually less than 0.0254 centimeters. The photocurable materials of the invention should intertwine (cure) and, therefore, harden in at least some region of actinic wavelength. As used herein, actinic radiation is radiation capable of effecting a chemical change in an exposed portion. Actinic radiation includes, for example, amplified (e.g., laser) and non-amplified light, particularly in the regions of UV and infrared wavelengths. Preferred actinic wavelength regions are from about 250 nm to about 450 nm, more preferably from about 300 nm to about 400 nm, even more preferably from about 320 nm to about 380 nm. The protective layer of the photocurable element, sometimes referred to as the sliding film, is disposed on the photocurable layer (s) and is typically from about 0.00254 to about 0.0254 centimeters thick. The protective layer protects the photocurable element from contamination, increases ease of handling, and acts as an ink-accepting layer. The final layer, the cover sheet, can be formed of plastic or any other removable material that can protect the plate from damage until it is ready for use. Representative photocurable elements according to the invention include flexographic printing plates of EPIC® and SPLASH® brands (commercially available from Polyfibron Technologies, Inc., Atlanta, GA). The registration is preferably achieved for composite plates by the computer controlled transfer of a negative image directly to the outward facing surfaces of at least two photocurable elements that have been mounted on the carrier sheet. Such negative images are preferably transferred by depositing a blocking material to the radiation on the respective surfaces of the photocurable elements. Following exposure to actinic radiation and subsequent processing, those portions of the plate that are not below the radiation blocking material form the relief image.

In preferred embodiments, the negative-forming ink is propelled from a printer, such as an inkjet printer, onto the composite plate. A wide variety of printers may be used in accordance with the present invention. Suitable printers are those that can print (or be adapted to print) well-defined images in various sizes and shapes of composite plates used in the printing industry. The level of definition (resolution) - typically measured in points per centimeter (dpi) - should be as large as possible. The amount of ink delivered by the printers of the invention should be sufficient to absorb at least about 85% of any incident actinic radiation, preferably about 90% of such radiation, more preferably about 95%, and even more preferably 99.9% of such radiation. Preferred printers are those that are capable of delivering a quantity of radiation absorbing ink completely in a simple print, although with some printers (and with some inks) multiple prints may be necessary to deliver an absorbing amount of radiation. Particularly preferred are ink jet printers. Ink jet printing is performed by discharging droplets of ink from a printer head to a substrate. The droplets are typically ejected through holes or nozzles in the print head and are directed to the substrate to form an image thereon. In contrast to many other types of printers, there is usually no contact between the printer and the substrate with the jet printer. ink. Virtually any ink jet printer can be used in accordance with the present invention, as long as it has a print head and some means to control and / or direct ejection of the ink therefrom. Similarly, virtually any printhead known in the art can be employed, provided that it comprises at least one nozzle which ejects droplets of ink in response to control signals. Referring to Figure 4, a representative printing apparatus according to the present invention is shown comprising a print head 30 having a plurality of nozzles 32 and control means 34 and 36 electrically coupled to the print head. The control means may be any of those known in the art to be able to control the placement of the print head relative to the printing substrate and to act (i.e., eject ink 38 from) the printhead. Control means convenient to the practice of this invention include computing devices such as microprocessors, microcontrollers, capacitors, switches, circuits, logic switches, or equivalent logic devices. Representative control means include a personal computer coupled to a head printhead board. Representative software packages include Adobe Photoshop and Corel Draw products. Representative ink jet printers include those manufactured by Dataproducts Corporation (Woodland Hills, CA), Jarfalla (Sweden), Encad (San Diego, CA), AlphaMerics (Simi Valley, CA), Videojet, (Wood Dale, IL), particularly Epson Stylus ink jet printers (Epson Corporation, Torrance, CA), HP 600c, HP 650c, HP 855c, and HP 750c (Hewlett-Packard Corp., Palo Alto, CA) and the Raster Imaging Processor (Alan Graphics, Peekskill, NY). An ink according to the present invention is any liquid or solid portion that is substantially opaque to actinic radiation in at least one wavelength region effective to cure the photocurable elements described above and substantially resistant to polymerization by exposure to radiation actinic in that region of wavelength. Substantially opaque inks are those that can absorb at least about 85% of any incident actinic radiation, preferably about 90% of such radiation, more preferably about 95%, and even more preferably 99.9% of such radiation. It will be recognized that a substantially opaque ink does not need to be substantially opaque in all quantities and at all possible concentrations, as long as it can be deposited on a substrate in sufficient quantity to be substantially opaque. The inks are resistant to polymerization substantially according to the invention as long as they can be removed from the surface of the plates to which they are applied (preferably using conventional plate washing techniques) without damaging the relief surface, and always and when they do not react with or otherwise alter the chemical and / or physical properties of the plate to such an extent that its removal damages the relief surface. Preferred inks include one or more radiation absorbing molecules dissolved in solvent, preferably at concentrations of about 3 to about percent by weight. Particularly preferred inks are U-26, Black 4D, and Jolt (Dataproducts Corporation) and those formed by mixing Crown Super Marking Stamping Ink (Fulton Marking Equipment Company, Warminster, PA) and UVINUL brand 3050 2, 2 ', 4, 4 '-tetrahydroxybenzophenone (BASF, Ludwigshaven, Germany) in a solvent selected from methanol, isopropanol, n-butanol, chloroform, methyl ethyl ketone, propylene glycol monomethyl ether, dipropylene glycol monomethyl ether, diethylene glycol ethyl ether, and mixtures thereof . Other useful ink ingredients include the Tinopal SPF and Joncryl 68 products, which are commercially available from Ciba-Geigy Corp., Hawthorn, NY, and S.C. Johnson Company, Milwaukee, Wl, respectively. The methods of the invention involve the transfer of a negative image to the surface of photocurable elements without the use of photo-tools or photo-masks. This is typically achieved by removing the cover film from the commercially available mounted photocurable elements and then printing the negative image onto the exposed surfaces by removing the cover sheets.

After the negative image has been transferred, it is exposed (and, therefore, at least a portion of the composite plate) to actinic radiation, preferably UV light, in a region of suitable wavelength. There are many devices that can be used to perform this so-called "front" exposure of photocurable elements, including FLEXLIGHT® brand UV modules (Polyfibron Technologies, Inc.), as well as those manufactured by Anderson & Vreeland (Bryan, OH). For certain applications, it may be desirable to combine the Printing and exposure functions in a single device. It may also be desirable to expose the "photocurable" backing elements by exposing the support layers thereof to actinic radiation for a time and under effective conditions to cure a portion of the photocurable material in the region adjacent to the support. This back exposure can be carried out after the assembly step (as long as the carrier sheet and the mounting means are sufficiently transparent to the actinic radiation), but more preferably it is carried out before the photocurable elements have been assembled. Following the frontal exposure of the negative image to actinic radiation, the uncured polymer is removed from the mounted photocurable elements, typically by washing the elements with (and / or in) an organic and / or aqueous solvent in which the photocurable material is at least somewhat soluble. This step of washing with solvent is accompanied or typically preceded by brushing, cleaning, or some other soft, non-destructive abrasion of the elements. Useful washing devices include those commercially available from Polyfibron Technologies and Anderson &; Vreeland. Objectives, advantages, and novel aspects of this invention will become apparent to those skilled in the art upon examination of the following examples thereof, which are not intended to be limiting.

EXAMPLE 1 A carrier sheet of 91.44 cm x 96.52 cm polyethylene terephthalate having a thickness of 0.01778 cm was cut from a roll and placed in an AlphaMerics brand inkjet plotter. The dimensional contours of the photocurable elements to be mounted on the carrier sheet were generated from an electronic image stored on a computer using Photoshop software. The contours were drawn on the carrier sheet in approximate register using the plotter of conventional graphics and inks. EPIC® brand 067 photocurable elements of the respective dimensions were cut and exposed from the back for 19 seconds on a FLEXLIGHT® model 5280 exposure unit (Polyfibron Technologies, Inc.). These elements were then mounted on the carrier sheet in the respective dimensional contours. The assembly of the elements on the carrier sheet was carried out using a double-sided adhesive tape. The cover sheets were removed from the assembled elements and the composite plate was placed on the plotter. A stored negative image was sent to the plotter from a computer and printed on the board at 600 DPI using Jolt brand ink. The thickness of the extended ink layer (approximately 0.00254 cm) from a 50 μm function head was sufficient to block 99.9% of the UV light used during subsequent curing. The software allowed the printing of the negative image only in those areas that had the assembled elements. A very accurate record was achieved by the computer handling the ink-jet plotter. The carrier carrying the assembled elements, with image were then exposed to a UV torrent in the FLEXLIGHT® brand exposure unit for 15 minutes. The composite plate was then processed by applying a continuous supply of SOLVIT ™ brand solvent (Polyfibron Technologies, Inc.) while the uncured polymer was brushed from the plate in a FLEXLIGHT® 5280 Processor, online processor Serial No. 017 for 6 minutes. The double-sided adhesive tape withstood the solvent during processing. The carrier was dried and post-exposed in a drying and finishing unit No. 017, Dryer 5280 of the brand FLEXLIGHT®. The carriers carrying elements with negative image are then mounted on a drum of 91.44 cm in circumference, the elements already in register. Conventional printing ink is applied to the negative surface in relief, and the surface is contracted with a sheet of paper to produce a high quality positive image. Those skilled in the art will appreciate that numerous changes and modifications can be made to the preferred embodiments of the invention and that such changes and modifications can be made without departing from the spirit of the invention. It is therefore intended that the appended claims cover all such equivalent variations as they fall within the true spirit and scope of the invention.

Claims (10)

1. CLAIMS 1. A method for preparing a composite printing plate, comprising the steps of: transferring registration information to a first face of a substantially planar carrier sheet having first and second opposed major faces of defined surface area by ejecting ink from a head of ink jet printer on said first face; providing at least one substantially flat photocurable element having first and second opposed major faces of defined surface area; arranging a first face of said photocurable element on said first face of said carrier sheet; and ejecting a negative-forming ink from an ink-jet printer head onto said second face of said photocurable element, said ink being substantially opaque to the actinic radiation in at least one region of effective wavelength to cure photocurable material within of said element and substantially resistant to polymerization by exposure to actinic radiation in said wavelength region. The method of claim 1 wherein said second face of said photocurable element is a layer of photocurable material. The method of claim 1 wherein said second face of said photocurable element is a protective transparent layer disposed on a layer of photocurable material. 4. The method of claim 1 wherein said photocurable material is disposed on a support layer. The method of claim 1 wherein said photocurable material comprises an elastomeric compound, an ethylenically unsaturated compound having at least one terminal ethylenic group, and a photo-initiator. The method of claim 1 wherein said element is disposed on said carrier sheet through the use of an adhesive. The method of claim 1 wherein said actinic radiation is ultraviolet light. The method of claim 1 wherein said wavelength region is from about 300 to about 400 nm. The method of claim 1 wherein said ink is ejected from said printer head by activator control means electrically coupled to said printer head. 10. Canceled. eleven . The method of claim 1 wherein said photocurable element is disposed on said first face of said carrier sheet in accordance with said registration information. The method of claim 1 wherein said registration information comprises an image that corresponds to an outline of at least one photocurable element. The method of claim 12 wherein said registration information comprises a rectilinear image having a shape that corresponds to said contour. The method of claim 12 wherein said registration information comprises an elliptical image having a shape corresponding to said contour. The method of claim 1 wherein said registration information comprises an image that corresponds to a portion of a contour of at least one photocurable element. The method of claim 15 wherein said registration information comprises perpendicular lines having a shape corresponding to a portion of said contour. The method of claim 15 wherein said registration information comprises an arc having a shape corresponding to a portion of said contour. 18. The method of claim 1 further comprising exposing said first face of said photocurable element to actinic radiation for a time and under effective conditions to cure said photocurable material. The method of claim 1 further comprising exposing said second face of said photocurable element to actinic radiation in said wavelength region for a time and effective conditions for curing exposed areas of said photocurable material. The method of claim 19 further comprising removing uncured photocurable material from said photocurable element. 21. A composite printing plate comprising at least one photocurable element disposed on a first surface of a substantially flat carrier sheet carrying registration information, including said photocurable element: a support layer; photocurable material disposed on said support layer; and negative forming ink disposed on said photocurable material, said ink being substantially opaque to the actinic radiation in at least one wavelength region effective to cure said photocurable material and substantially resistant to polymerization by exposure to actinic radiation in said region. of wavelength. 22. The composite plate of claim 21 wherein said carrier sheet is a polyester film. 23. The composite plate of claim 21 further comprising an adhesive disposed between said photocurable element and said carrier sheet. 24. The composite plate of claim 21 wherein said photocurable material comprises a plurality of layers. 25. The composite plate of claim 21 wherein said photocurable material comprises an elastomeric compound, an ethylenically unsaturated compound having at least one terminal ethylenic group, and a photo-initiator. 26. The composite plate of claim 21 wherein said ink comprises 2, 2 ', 4, 4'-tetrahydroxybenzophenone. 27. The composite plate of claim 21 further comprising a transparent protective layer disposed on said material photocurable between said ink and said photocurable material. 28. The composite plate of claim 21 further comprising a layer of adhesive disposed between said support layer and said carrier sheet.