PRINTING PROCESS

CROSS-REFERENCE TO RELATED APPLICATION

[0001] The present application claims priority to U.S. Provisional Patent Application No. 61/551 ,039, filed on October 25, 201 1 (Attorney Docket No. 291 1-02000); which is hereby incorporated herein by reference.

BACKGROUND

[0002] The light reflected from a display such as an LCD, plasma, LED, touch-screen, or other glass display on a computing or portable electronic device may cause problems with the functionality and the usability of the device coupled to the display. Glare may cause eye fatigue and headaches in users, and can reduce the contrast, colors, and sharpness of the display. An anti-glare computer screen is designed to cut down on the amount of light that reflects off the display by making the display more easily viewable and reducing eyestrain.

SUMMARY

[0003] An embodiment of a method of roll-to-roll flexoplate printing comprising applying a particle-based ink to an anilox roller; transferring the particle-based ink from an anilox roller to a flexographic plate. The embodiment further comprising transferring the particle- based ink from the flexographic plate to a substrate in a roll-to-roll printing system, wherein the particle-based ink is drawn into a plurality of recesses on the flexographic plate and transferred in a homogenous sheet on to the substrate.

[0004] In an alternate embodiment, an anti-glare coating comprising: a first layer; a second layer disposed on the first layer; wherein the first layer comprises a corona- treated film, and wherein the second layer comprises inorganic particles, a polymer binder, and a dispersant; and wherein the coating has a haze less than 15%.

[0005] In another embodiment, a method of using ink to print a substrate comprising: removing, using an adhesive roll, impurities from a substrate; treating a surface of the substrate; using an ink, printing the surface of the substrate by: supplying the ink to an anilox roll, wherein the anilox roll comprises a body and a coating, wherein the anilox roll is in proximity to an at least one flexographic plate; and wherein the ink is UV-curable and comprises at least one of inorganic oxide and organic particles. BRIEF DESCRIPTION OF THE DRAWINGS

[0006] For a detailed description of exemplary embodiments of the invention, reference will now be made to the accompanying drawings in which:

[0007] Fig. 1 shows an example of a flexo-plate with a honeycomb cells structure.

[0008] Fig. 2 shows an embodiment of a flexographic printing process used to achieve anti-glare effects on a plastic film.

[0009] Fig. 3 is a side view in partial section of an anti-glare coating in accordance with various embodiments on a substrate.

[0010] Fig. 4 is an embodiment of a method how special ink is prepared and used in a flexo-graphic printing process.

DETAILED DESCRIPTION

[0011] The following discussion is directed to various embodiments of the invention. Although one or more of these embodiments may be preferred, the embodiments disclosed should not be interpreted, or otherwise used, as limiting the scope of the disclosure, including the claims. In addition, one skilled in the art will understand that the following description has broad application, and the discussion of any embodiment is meant only to be exemplary of that embodiment, and not intended to intimate that the scope of the disclosure, including the claims, is limited to that embodiment.

[0012] Various embodiments are described herein related to a flexo-graphic printing process for applying anti-glare coating to a substrate. The substrate may then be affixed or applied, for example, to a display or another type of glare-inducing device.

[0013] In accordance with various embodiments, a method comprises preparing a special ink with an anti-glare property, forming a flexographic master, forming an anti-glare coating on a substrate using the master plate and ink, and curing the coated substrate using a curing process.

[0014] Flexography is a form of a rotary web letterpress where relief plates are mounted on to a printing cylinder, for example, with double-sided adhesive. These relief plates, which may also be referred to as a master plate or a flexoplate, may be used in conjunction with fast drying, low viscosity solvent, and ink fed from anilox or other two roller inking system. The anilox roll may be a cylinder used to provide a measured amount of ink to a printing plate. The ink may be, for example, water-based or ultraviolet (UV)-curable inks. In one example, a first roller transfers ink from an ink pan or a metering system to a meter roller or anilox roll. The ink is metered to a uniform thickness when it is transferred from the anilox roller to a plate cylinder. When the substrate moves through the roll-to-roll handling system from the plate cylinder to the impression cylinder, the impression cylinder applies pressure to the plate cylinder which transfers the image on to the relief plate to the substrate. In some embodiments, there may be a fountain roller instead of the plate cylinder and a doctor blade may be used to improve the distribution of ink across the roller.

[0015] Flexographic plates may be made from, for example, plastic, rubber, or a photopolymer which may also be referred to as a UV-sensitive polymer. The plates may be made by laser engraving, photomechanical, or photochemical methods. The plates may be purchased or made in accordance with any known method. The preferred flexographic process may be set up as a stack type where one or more stacks of printing stations are arranged vertically on each side of the press frame and each stack has its own plate cylinder which prints using one type of ink and the setup may allow for printing on one or both sides of a substrate. In another embodiment, a central impression cylinder may be used which uses a single impression cylinder mounted in the press frame. As the substrate enters the press, it is in contact with the impression cylinder and the appropriate pattern is printed. Alternatively, an inline flexographic printing process may be utilized in which the printing stations are arranged in a horizontal line and are driven by a common line shaft. In this example, the printing stations may be coupled to curing stations, cutters, folders, or other post-printing processing equipment. Other configurations of the flexo-graphic process may be utilized as well.

[0016] In an embodiment, flexo plate sleeves may be used, for example, in an in-the- round (ITR) imaging process. In an ITR process, the photopolymer plate material is processed on a sleeve that will be loaded on to the press, in contrast with the method discussed above where a flat plate may be mounted to a printing cylinder, which may also be referred to as a conventional plate cylinder. The flexo-sleeve may be a continuous sleeve of a photopolymer with a laser ablation mask coating disposed on a surface. In another example, individual pieces of photopolymer may be mounted on a base sleeve with tape and then imaged and processed in the same manner as the sleeve with the laser ablation mask discussed above. Flexo-sleeves may be used in several ways, for example, as carrier rolls for imaged, flat, plates mounted on the surface of the carrier rolls, or as sleeve surfaces that have been directly engraved (in-the-round) with an image. In the example where a sleeve acts solely as a carrier role, printing plates with engraved images may be mounted to the sleeves, which are then installed into the print stations on cylinders. These pre-mounted plates may reduce changeover time since the sleeves can be stored with the plates already mounted to the sleeves. Sleeves are made from various materials, including thermoplastic composites, thermoset composites, and nickel, and may or may not be reinforced with fiber to resist cracking and splitting. Long-run, reusable sleeves that incorporate a foam or cushion base are used for very high-quality printing. In some embodiments, disposable "thin" sleeves, without foam or cushioning, may be used.

Ink Preparation

[0017] The ink used in the flexographic process may be water-based, solvent-based, or UV-curable. The type of ink utilized in a flexographic process may depend, for example, on the type of substrate to be printed, the complexity of the print pattern, or a combination of multiple factors. Printing ink is the material that is used to provide the physical and optical properties required by an anti-glare coating on the surface of a substrate. Antiglare coating may be desirable, for example, on television screens including LCD, LED, plasma, 3D, touch screen, or on other displays such as those on portable electronic devices, including devices with touch screens. Preferably, the ink is prepared in a way that it can be transferred accurately from either an ink pan or an ink metering system to a flexo-plate, and then to a target substrate, with consistent volume from the flexoplate. The ink should be prepared so that it has good adhesion to the substrate, and can cure instantaneously at a high printing speed, for example, 750 feet per minute (fpm). The substrate may be comprised of polyethylene terephthalate (PET), polymethyl methacrylate (PMMA), paper, or other suitable material. Preferably, the printed structure will have good adhesion to the substrate and be robust for daily handling such as scratch resistance. The printed structure may be a plurality of lines, wherein the term lines is used to describe geometric features created by a line or lines of the plurality of lines.

[0018] In order to realize high printing speed and curable features simultaneously, UV- curable inks are formulated to achieve those properties. In order to have a high scattering property, UV-curable ink doped with ink inorganic oxide or organic particles is also selected. For example, commercially available UV Flexo Matte LG OP2001 and OP2009 from Nazdar may be selected for starting materials. The irregular shape of a particle, for example, silica, inside the ink causes the scattering centers to redirect the incidental light, thereby reducing glare on the completed product. The particle size may vary from 1 to 30 microns (5 to 10 microns in some embodiments) and the particle content may vary from 10% to 70% by weight (20-30% in some embodiments). The ink is further modified to achieve the satisfied printing property and still possess the optical properties that are pursued such as antiglare, scratch resistance, and low surface energy. The ink may be modified by a silica dispersed in UV-curable resins, as well as, for example, pentaerythritoltetraacrylate, propoxylated trimethylolpropane triacrylate, 1- Hydroxycyclohexyl phenyl ketone, and 2,2-Dimethoxy-2-phenylacetophenone. In an embodiment, the weight ratio of the silica dispersed in UV-curable resins to the total of pentaerythritoltetraacrylate+ propoxylated trimethylolpropane triacrylate is from 1 :3 to 3:1 . It should be appreciated that components of pentaerythritoltetraacrylate+ propoxylated trimethylolpropane triacrylate may improve the mechanical strength and scratch resistance of the coating.

[0019] These property modifiers may all be commercially available, for example: SR295, and CD501 are from Sartomer. Doublecure 184 and Doublecure BDK are from Double Bond Chemical. In this case, there is no need to have surface micro-structure to scatter in-coming light. The scattering centers are built into the composite. Thus, the uneven surface topography is not essential to have low gloss property. Alternatively, the ink may contain inorganic particles which may be dispersed in shapes and concentrations as described above.

[0020] In an embodiment, a printing ink prepared for an anti-glare application. There may be a number of chemical components used in the ink preparation in order to have the optical and physical properties required by anti-glare property. For example, the following combination may achieve those properties: OP2009 = 200 ml_, Doublecure 184 = 10.0 grams, SR295 = 150 ml_, Doublecure BDK = 5.0 grams, and CD501 = 50 mL. The ink preparation process is performed in order to generate an ink that is appropriate for not only the substrate on which the pattern is printed, but also for the geometry and complexity of the geometry of that pattern. In some embodiments, multiple inks may be used in a plurality of printing stations in order to form the desired geometries.

[0021] Fig. 1 is a perspective view of an embodiment of a flexo-plate 200. In Fig. 1 , there is a flexo-plate 200 that has been recorded in a laminated photoresist. In Fig. 1 , the pattern shown has honeycomb cells structure 202. Honeycomb structure 202 comprises walls 204 spaced to create wells 206. In one example, the wells 206 of a particular pattern design may carry, within its cells, ink (not pictured) up to a thickness of about 14 microns on the flexo-plate, which may eventually end up with a coating thickness of 4-7 microns. The ink may have anti-glare properties and be disposed on a polyethylene terephthalate (PET) or other substrate. Honeycomb cells structure 202 may function to pick up ink in the wells 206 and retain the ink in the wells 206 that is going to be transferred to the substrate. During the printing process, ink from the walls 204 of the honeycomb features of the flexoplate 200 is not imprinted on the substrate in the honeycomb pattern. Instead, ink flows on to the substrate from the wells 206, forming a homogeneous coating on the substrate. In other embodiments (not pictured) structures other than the honeycomb structure may be used instead of or in addition to the honeycomb geometry wherein other surface geometries are those such as diamond, circles, zig-zags, or other geometries as appropriate to transfer the ink homogenously. However, a flat, unpatterned flexoplate may not be able to carry as much ink as the flexo with the honeycomb cells structure, so in embodiments where a thicker coating is preferred for the desired anti-glare and anti-scratch properties, a flexo with the honeycomb structure 202 may be used.

[0022] Fig. 2 shows an embodiment of flexographic printing process 300. In figure 2, once the ink 312 and the master plate 318, for example, as described above with respect to Fig. 1 , are ready, a roll-to-roll flexographic printing process may be performed. Such a printing process may involve some or all of the following steps. Substrate 302 may be a PET film placed on unwind roll 304 and then transferred to sticky roll 306 via any known roll to roll handling method. Thermoplastic polymer resins, such as polytehlyene terephthalate, and other resins in the the polyester family may be used in the manufacture of products such as synthetic fibers; beverage, food and other liquid containers; thermoforming applications. In some instances, engineering resins may be used in combination with glass fiber. Sticky roll 306, which may also be referred to as an adhesive roll, may then be used to remove impurities such as dust particles or other impurities from the substrate 302. Once the substrate 302 has been cleaned of impurities, it may then go through corona surface treatment device 308. A corona surface treatment may be a surface modification technique that uses a low temperature corona discharge plasma to impart changes in the properties of a surface. The corona plasma is generated by the application of high voltage to sharp electrode tips which forms plasma at the ends of the sharp tips. A linear array of electrodes is often used to create a curtain of corona plasma. Materials such as plastics, cloth, or paper may be passed through the corona plasma curtain in order to change the surface energy of the material. In some embodiments, substrate materials such as polyethlene and polypropylene have chemically inert and nonporous surfaces with low surface tensions which may cause them to be non-receptive to bonding with printing inks, coatings, and adhesives. A surface treatment, for example, a corona surface treatment device 308, may be used to modify the surface energy on substrate 302 in order to improve the adhesion for further printing process. The sticky roll 306 maybe used to remove impurities or contamination but may not remove particulate matter, so the corona surface treatment device 308 may be utilized. In an alternative embodiment, the corona surface treatment device 308 may not be utilized.

[0023] Substrate 302 may then be printed at printing device 310, wherein the printing 310 uses a special ink 312, an embodiment of which was previously described in the ink preparation section, may be applied on one side of substrate 302. The printing device 310 may supply a portion of the ink contained in the ink pan 312a to anilox roll 314. Anilox roll 314 may be constructed of a steel or aluminum core which may be coated by an industrial ceramic whose surface contains millions of very small cells. Anilox roll 314 material coated with ceramics may be used because of excellent resistance to wear and the ease with which the number of engraved lines is increased. In this disclosure, the embodiment of the anilox roll 314 that may be required for this particular ink may range from large to extra-large size, possibly having a cell volume of about 9.0 BCM (billion cubic microns per square inch). In an embodiment, the anilox roll 314 has a cell volume of 5-30 BCM. Preferably, the anilox roll 314 has a cell volume between 9-20 BCM.

[0024] Depending on the particular embodiment of printing process 310, anilox roll 314 may be either semi-submersed in ink pan 312 or come into contact with a metering roll, not shown. In this embodiment, anilox roll 314 is semi-submersed in ink pan 312a, and as anilox roll 314 rotates, doctor blade 316 may be used to scrape excess ink from the surface leaving just the measured amount of ink in the cells. The anilox roll 314 then rotates to contact with the flexographic printing plate (master plate 318) which carries the ink (anti-glare coating 320) using the honeycomb cells structure of Fig. 1 or other structure, from anilox roll 314 and transfers it to substrate 302. In some applications, the amount of ink on the flexo-plate may have an average thickness of 14 microns that in many cases results in a final coating of 4 to 7 microns on the surface of substrate 302. The rotational speed of master plate 318 should preferably match the speed of the web, which may vary between 20 fpm and 750 fpm. In an alternate embodiment, the coating thickness on the substrate is from 0.5 microns - 15 microns.

[0025] Printing device 310 may be followed by one or more curing methods. In the embodiment shown in figure 3, UV light is employed as a curing device 322. After antiglare coating 320 is successfully applied on substrate 302, curing device 322 may immediately be applied in order to cure the ink (anti-glare coating 320). Note that curing method 322 may be located at a distance preferably no more than 4 inches from printing device 310. The time anti-glare coating 320 is exposed to UV light may vary from 1 to 3 seconds, depending on the web speed. The UV lamp for curing device 322 that may be used in this process may be a mercury arc lamp, broadly speaking, that may be constructed of a long sealed quartz tube which is filled with a starting gas and a small amount of mercury and has an electrode at each end. When a voltage is applied between the electrodes, the starting gas ionizes and starts to heat up. The hot gas evaporates the mercury which then emits radiation, a proportion of which is in the UV range. As UV inks and coatings do not solidify until they are cured, there is no need to wash-down machines at the end of shifts or between runs. Wash-downs tend to be quicker and easier too as there will be no dried on contaminants and no cell plugging of Anilox rollers. As a result, machine utilization may be improved and, with no evaporative losses, ink consumption will be reduced. The reduced curing times enable high production speeds and immediate post processing, for example, stacking, folding, or polishing.

[0026] In an embodiment, the anti-glare coating may be cured with curing device device 322 which may comprisea UV lamp, wherein the intensity of illumination of the ultraviolet ray may be 5-30W/cm ² with a dose of 0.5-5 J/cm ² . In one example, the gloss at 20° is <10 gloss units (GU) and the haze is <15%. Preferably, at 20°, the gloss is <5 GU and the haze is <10%. In another example, the gloss at 60° is <30 gloss units (GU) and the haze is <15%. Preferably, at 60°, the gloss is <20 GU and the haze is <10%. In an alternate example, the gloss at 80° is <70 gloss units (GU) and the haze is <1 %. Preferably, at 80°, the gloss is <40 GU and the haze is <10%.

[0027] The anti-glare effect achieved by this disclosure compared to other competitors has lower gloss at 20°, 60°, and 85°, maintaining a low haze of 5.5%. In addition, using the antiglare ink of this disclosure, a 90% transmission of light can be achieved, which may be considered a good transparency level of the film.

[0028] After the ink is cured, the process may be finished and the substrate with anti-glare coating 320 is ready to be either possibly cut or rolled back again in winding roll 324 located at the rear end of the web. Figure 3 is a side view in partial section of an antiglare coating in accordance with the disclosure, on top of a substrate. In fig. 3, an embodiment of end product 400 is shown, which may be the result of the process previously described in Fig. 2. Fig. 3 includes two sections or layers, a first section 402, formed of any film (plastic, etc.) that has been previously treated with corona to provide adhesive properties sufficient to bind to a second section 404. Second section 404 as shown in Figure 3, has a surface that may appear flat with certain roughness resulting from the special ink, an embodiment of which was previously described. Within second section 404, there are inorganic particles that may comprise a silicon-containing compound, silicon dioxide, aluminum oxide, zirconium oxide, calcium carbonate, talc, clay, baked kaolin, baked calcium silicate, hyd rated calcium silicate, aluminum silicate, magnesium silicate, calcium phosphate, or other compounds. Preferably, the compounds may include a silicon-containing inorganic compound and zirconium oxide. In an embodiment, silicon dioxide 406 (S1O2) is preferable. The particles may be globular, tabular or amorphous. Second section 404 also contains photo sensitive polymer binder, for example, acrylic resin 408 and a dispersant that may be mixed in the resin to impart the compatibility between the polymer binder and the particles, thereby allowing the particle to remain stable without aggregating due to steric stabilization or electrostatic stabilization.

[0029] Figure 4 shows an embodiment of a method of a flexographic printing process. The ink is prepared at 502-506. A UV-curable ink is selected 502. In an embodiment, this ink may be doped with ink inorganic oxide or organic particles. The ink may be, for example, UV Flexo Matte LG OP2001 or OP2009 obtained from Nazdar. The ink may comprise particles that are, for example, globular, tabular or amorphous. The ink may be modified 504 to achieve the desired printing properties while maintaining the optical properties that are pursued such as antiglare, scratch resistance, and low surface energy. These property modifiers may all be commercially available, for example: SR295, and CD501 are from Sartomer. Doublecure 184 and Doublecure BDK are from Double Bond Chemical. Once the ink is prepared, it may be disposed in, for example, an ink pan or an ink metering system 506. At least one master plate may be manufactured, for at 508 prior to, subsequent to, or simultaneously with the ink preparation. Once the ink is prepared and the master plate is manufactured, the substrate is processed 510. The substrate may be disposed on an unwind roll 512 and transferred to a sticky roll where the impurities are removed 514. Once impurities have been removed from the surface by the sticky roll 514, the substrate may undergo a surface treatment 516. Preferably, the surface treatment 516 may be a corona treatment. The ink may be supplied to an anilox roll 518 that prints the substrate 520. The substrate may be cured 522, for example, by an ultraviolet (UV) lamp. The curing process may produce an anti-glare effect that reduces haze. In an embodiment, a haze below 5.5% is achieved through this process which may result in a 90% transmission of light. In some embodiments, the curing process 522 may comprise a plurality of curing steps. Subsequent to curing 522, the substrate may be loaded on to the wind roll 524.