Patent Application
20130333582
The disclosure relates to a method and apparatus for leveling a printed image to prevent image defects in a finished print product while preventing offset of the printed image to any leveling or fuser member.
Conventional drop ejector printing processes that apply ultraviolet (UV) curable gel inks often result in various image related defects such as, but not limited to, lines that resemble a corduroy or vinyl record-like appearance, streaking, pin-hole defects, line deletion, dot deletion, patch deletion, gloss non-uniformity, etc.
UV curable gel inks are desirable for ink jet printers because they remain in a solid phase at room temperature during shipping and have long term storage capabilities, among other reasons. In addition, problems associated with nozzle clogging as a result of ink evaporation with liquid ink jet inks are largely eliminated with UV curable gel inks, thereby improving the reliability of the ink jet printing. Furthermore, in phase change ink jet printers wherein the ink droplets are applied directly onto the final recording substrate (such as, for example, paper, transparency material, and the like), the droplets solidify immediately upon contact with the substrate, so that migration of ink along the printing medium is prevented and dot quality is improved.
Nevertheless, gel inks require some type of transformation such as curing to prevent them from running or smearing when printed onto a substrate and subjected to general handling. In addition, uncured gel inks stick to roller surfaces in print paths, making them unsuitable for many printing applications without some sort of transformation or curing.
The aforementioned image defects are often caused by an uneven distribution of ink in an image area in which the image should be smooth and uniform. Because the ink temperature drops after ejection, the ink freezes on contact with the substrate and an uneven distribution of ink on the image substrate may occur. The human eye can sometimes observe the uneven distribution as bands or lines in the direction of the substrate travel past the print head, missing portions of the image, or gloss-related defects, for example. This uneven distribution might be addressed by leveling the ink on the image substrate with a contact member, such as a roller, belt, or wiper, in an effort to normalize the ink distribution. Leveling also enables uniform gloss appearance for better image quality, and facilitates line growth to compensate for missing or weak jetting.
Gel inks have very little cohesive strength prior to curing. In addition, gel inks are typically designed to have good affinity to many different types of materials. What this means is that that conventional methods for flattening a layer of ink tend to fail with respect to gel inks, because the gel ink splits. As the splitting occurs, the gel ink leaves a significant portion of the image behind on the device that is trying to flatten it, such as a traditional fuser roll typically used in xerography processes.
Therefore, there is a need to level a printed image to reduce or eliminate image defects caused by the use of UV gel inks while preventing offset to a leveling member.
According to one embodiment, an apparatus useful in printing comprises a contact leveling member configured to level an image applied to a media substrate. The contact leveling member comprises at least one textured surface configured to repel one or more inks.
According to another embodiment, a method for leveling an image applied to a media substrate comprises causing, at least in part, a contact leveling member that comprises at least one textured surface configured to repel one or more inks to level the image applied to the media substrate.
According to another embodiment, a method for manufacturing a contact leveling member useful in printing having at least one superoleophobic surface comprises causing, at least in part, one or more surfaces of the contact leveling member to be textured by way of one or more of sputtering and photolithography. According to the method, the at least one textured surface is configured to cause, at least in part, the at least one textured surface to have a contact angle greater than 100° and a sliding angle less than 30° when the at least one textured surface contacts the one or more inks.
Exemplary embodiments are described herein. It is envisioned, however, that any system that incorporates features of any apparatus, method and/or system described herein are encompassed by the scope and spirit of the exemplary embodiments.
The embodiments of the invention are illustrated by way of example, and not by way of limitation, in the figures of the accompanying drawings:
Examples of a method and apparatus for leveling a printed image are disclosed. In the following description, for the purposes of explanation, numerous specific details are set forth in order to provide a thorough understanding of the embodiments of the invention. It is apparent, however, to one skilled in the art that the embodiments may be practiced without these specific details or with an equivalent arrangement. In other instances, well-known structures and devices are shown in block diagram form in order to avoid unnecessarily obscuring the embodiments.
As used herein, the term “micro/nano structure” refers to a structure formed on a surface by any means or material having dimensions of any type on the order of 100 nm to 20 μm, for example.
As used herein, the term “textured surface” refers to a surface populated with any number of types of micro/nano structures, or sputtered with a coating to give the surface a particular roughness other than an inherent roughness of the surface without the coating.
As used herein, the term “pillar” refers to a type of micro/nano structure that looks like a column, for example. A pillar may be three-dimensional rising from a surface and be of any shape in cross-section.
As used herein, the term “groove” refers to a type of micro/nano structure or series of micro/nano structures that comprise a spacing between portions of the micro/nano structure or series of at least two micro/nano structures such that the spacing has a length less than or equal to a length of the surface.
As used herein, the term “re-entrant structure” refers to an overhanging structure that extends from a surface of a micro/nano structure over any spacing between one micro/nano structure and another micro/nano structure.
As used herein, the term “contact angle” refers to an angle at which a liquid meets a surface. For example, consider a liquid droplet at rest on a flat surface. In a cross-sectional view, an angle formed by the surface and a tangent line to a surface of the liquid droplet is the contact angle.
As used herein, the term “sliding angle” refers to the tilting angle of a surface when a liquid droplet starts sliding downward.
One proposed solution to address the above-mentioned defects that may be noticeable because of the use of UV curable gel inks, regardless of how they are caused, includes contact leveling the image to smooth the image and mask the image defects. Contact leveling may be conducted, for example, by mechanically applying a pressure by way of a roller, belt, or press pad, for example, to the substrate having the image. However, physically contacting the printed image often results in other image defects that are alternatively caused, or are in addition to, the image defects discussed above. For example, some of the image may offset to the contact leveling member, thereby affecting the image and/or finish of the image. For example, gloss non-uniformities, potential re-transfer of an image may occur causing a ghost image, color density may be affected by not having enough pigment, etc.
Another proposed solution for mitigating image defects suggests reflowing any inks that are used to form the printed image to allow the image to level after the image has been applied to the substrate. But, such reflowing often results in causing pin-hole-like defects to occur on the image. Applying a flood coat after the printing of the image is complete is another option. However, while the flood coat fills the valleys in the corduroy-like image defects and provides a more uniform appearance, the flood coating technique often causes an undesirable higher gloss. Additionally, a print system that is configured to apply a flood coat is more complex than alternative systems, and consequently, costs more to build and to operate. Further, a flood coat does not mask missing inkjets in addition to the above discussed potential gloss non-uniformities.
To address these problems, a system 100 of
UV curable gel inks are typically made of organic acrylic materials, an as such, behave like oil. Accordingly, to be ink phobic, a surface of the contact leveling member should be superoleophobic. A superoleophobic surface repel oil and grease.
As shown in
According to various embodiments, though illustrated in
According to various embodiments, the superoleophobic surface 107 features one or more surface textures and may be treated with a surface coating such as a self-assembled fluorosilane layer synthesized from, but not limited to, tridecafluoro-1,1,2,2-tetrahydrooctyltrichlorosilane, tridecafluoro-1,1,2,2-tetrahydrooctyltrimethoxysilane, tridecafluoro-1,1,2,2-tetrahydrooctyltriethoxysilane, heptadecafluoro-1,2,2,2-tetrahydrooctyltrichlorosilane, heptadecafluoro-1,1,2,2-tetrahydrooctyltrimethoxysilane, heptadecafluoro-1,1,2,2-tetrahydrooctyltriethoxysilane, or a combination thereof, and the like, using the molecular vapor deposition technique or the solution coating technique. In one or more embodiments, the one or more surface textures may be formed from one or more micro/nano structures such as pillars, grooves, etc., or any combination thereof.
According to various embodiments, the superoleophobic surface 107 comprises one or more surface textures and may be solution coated with an oleophobic fluoropolymers such as AF1600 and AF2400 manufactured by DuPont, for example, or a perfluoropolyether polymer such Fluorolink-D, Fluorolink-E10H or the like manufactured by Solvay Solexis, for example. In one or more embodiments, the one or more surface textures may be formed from one or more micro/nano structures such as pillars, grooves, etc., or any combination thereof.
According to various embodiments, the one or more micro/nano structures may be formed by way of photolithography and etching techniques, for example, such as an overhanging re-entrant structure formed onto the body 108 of the contact leveling member 105 or onto a substrate is applied to the body 108 to form the superoleophobic surface 107. According to various embodiments, the substrate and/or the body 108 upon which the superoleophobic surface 107 is formed may be flexible and comprise polyimide, polyethylene naphthalate, polyethylene terephthalate, stainless steel, silicon, etc., or any combination thereof, for example. According to various embodiments, because the substrate upon which the superoleophobic surface 107 may be formed is flexible, a substrate having the superoleophobic surface 107 may be processed using a roll-to-roll process to impose any texturing to form the superoleophobic surface 107.
As discussed above, the contact leveling member 105 is configured to level an image applied to a substrate 103. For example, the print station 101 applies ink droplets 109 onto the substrate 103 to form an image. As discussed above, the image formed from ink droplets 109 should be leveled to the substrate 103 to mitigate any image defects such as the various defects discussed above or defects caused by a missing inkjet. The contact leveling member 105, is caused to contact the image applied to the substrate 103, when it levels the image formed from ink droplets 109 to the substrate 103. The contact leveling member 105, when it contacts the image applied to the substrate 103, experiences very little, if any, offset of the image to the superoleophobic surface 107. Once the image formed by ink droplets 109 are leveled, a leveled image 111 is caused to be finally cured by ultraviolet (UV) light, for example, shined onto the leveled image 111 by a UV light source 113 configured to shine ultraviolet light 115 onto the leveled image 111.
The superoleophobic surface 107 has superoleophobic properties because the superoleophobic surface 107 has at least one textured surface, as discussed above. The at least one textured surface causes the superoleophobic surface 107 to have properties such as contact angle greater than 100° with water, oil (hexadecane) and UV ink, for example, and a sliding angle less than 30° for water, oil and UV ink when the superoleophobic surface 107 contacts any of water, oil or UV ink. In one or more embodiments, the superoleophobic surface 107, may have differing geometries that affect contact angle and sliding angle performance, as well as different coatings. For example, consider Table 1-1 which shows sample performances of a superoleophobic surface 107 having one or more pillars and a superoleophobic surface 107 having a grooved surface finish upon which ˜10 μl of testing liquids used for tilting angle measurements. The example illustrated in Table 1-1 also shows results for superoleophobic surfaces coated with a self-assembled fluorosilane layer from tridecafluoro-1,1,2,2-tetrahydrooctyltrichlorosilane (FOTS).
Contact angle and sliding angle are key indicators for the oleophobicity of surface 107. A high contact angle indicates high repellency and low wettability by a test droplet of liquid (water, hexadecane, UV ink), whereas a low sliding angle indicates low surface adhesion between the test droplet of liquid and the surface 107.
Comparatively, conventional low surface energy contact levelling surfaces comprising Teflon®, Perfluoroalkoxy (PFA) film, and/or Cytop, for example, are actually oleophilic. The oleophilicity of these materials are indicated by moderate wettability and high adhesion for UV ink. The wettability and high adhesion of UV ink leads to substantial ink offset to a contact leveling surface having any conventional surface. For example, Teflon® has performance characteristics such as those illustrated in Table 2-1 below.
Not surprisingly, Teflon-like coated contact leveling surfaces show high UV ink offset and fail to provide sufficient contact leveling (most likely because some of the image is transposed from the substrate to a conventional contact leveling surface via offset). Because the superoleophobic surface 107 is better suited for preventing ink offset than a conventional contact leveling surface, as illustrated above, the use of the superoleophobic surface 107 enables robust and reliable image conditioning, leveling.
To facilitate the superoleophobicity, the superoleophobic surface 107, as discussed above, may be fabricated by first sputtering an amorphous silicon layer on a substrate, followed by texturing the surface by photolithography and etching to create the one or more micro/nano structures, and then coating the textured surface with a conformal surface treatment.
According to various embodiments, the one or more micro/nano structures may take many forms such as, but not limited to, pillars, grooves, or any combination thereof. The one or more micro/nano structures, if formed as pillars, for example, may have any shape in cross-section such as, but not limited to, a circle, ellipse, triangle, rectangle, square, octagon, hexagon, any other polygon, or freeform, for example, and may be the same, or any combination of shapes as imposed onto the body 108 of the contact leveling member 105, or the substrate upon which the superoleophobic surface 107 is imposed. Additionally any of the pillars, grooves, etc., may have, for example, one or more lips that are re-entrance structures having a greater dimension in cross-section than other portions of the microstructure. For example, a pillar may from a side view, look like a nail having a head and a shaft.
According to various embodiments, one or more side surfaces of the one or more micro/nano structures may be any of smooth, wavy, ribbed, and the like. For example, if the side surface is wavy, the wavy structure may be on the order of about 200 nm. The superoleophobic surface 107 may have micro/nano structures such as, for example, pillars of 100 nm to 10 μm in diameter and 100 nm to 10 μm in height with center-to-center spacing of 100 nm to 10 μm, grooves of 100 nm to 10 μm in width and 100 nm to 10 μm in height with center-to-center spacing of 100 nm to 12 μm, as well as any variable length, or any combination thereof. The magnitude of the micro/nano structures and any spacing therebetween may be based, at least in part, on the ink that may be applied to the substrate 103.
It should be noted that, while
The process continues to step S420 in which the developed substrate 403 is etched using any etching process such as, for example, a Bosch etching process, or any other etching technique, stripped and cleaned resulting in textured substrate 405. This example, the textured substrate 405 has pillars and/or grooves such as pillars 201 and grooves 301, discussed above imposed to the surface 404. Next, in step S430, the textured substrate 405 is coated with POTS by, for example, a molecular vapor deposition process to result in superoleophobic substrate 407 having the superoleophobic surface 107 discussed above. The resulting micro/nano structures 201/301, for example, formed in this embodiment have wavy side walls, as discussed above. According to various embodiments, the blank substrate 401 may be provided and processed in sheeted or roll to roll form, for example.
The process continues to step S530 in which the photo resist coated substrate 505 is etched using fluorine based reactive ion etching (CH3F/O2), stripped and cleaned resulting in a patterned silicon oxide layer 503 on substrate 507. Next, in step S540 the substrate 507 is further etched by a second fluorine based (SF6/O2) reactive ion etching process, followed by hot stripping, and piranha cleaning to create the textured micro/nano structures 201/301 having overhang re-entrant structures 508 to result in the textured substrate 509. Optionally, a Xenon difluoride isotropic etching process can be applied to enhance the degree of overhang on textured micro/nano structures 201/301 (not shown in
Then, in step 703, a contact leveling member comprising at least one textured surface configured to repel one or more inks is caused to level the image applied to the media substrate. As discussed above, the at least one textured surface may have one or more micro/nano structures configured to cause, at least in part, the at least one textured surface to have a contact angle greater than 100° and a sliding angle less than 30° when the at least one textured surface contacts the one or more inks. Additionally, the one or more micro/nano structures may be any of one or more pillars, one or more grooves, one or more pyramids, or any combination thereof. In one or more embodiments, the contact leveling member comprises a body and the at least one textured surface is formed on a substrate applied to the body. Alternatively, the at least one textured surface may be imposed on the body itself. The process continues to step 705 in which the leveled image is cured.
The processes described herein for leveling a printed image to reduce or eliminate image defects may be advantageously implemented via software, hardware, firmware or a combination of software and/or firmware and/or hardware. For example, the processes described herein, may be advantageously implemented via processor(s). Digital Signal Processing (DSP) chip, an Application Specific Integrated Circuit (ASIC), Field Programmable Gate Arrays (FPGAs), etc.
While a number of embodiments and implementations have been described, the invention is not so limited but covers various obvious modifications and equivalent arrangements, which fall within the purview of the appended claims. Although features of various embodiments are expressed in certain combinations among the claims, it is contemplated that these features can be arranged in any combination and order.
