Patent Grant
6935734
1. Field of the Invention
The present invention relates to a system and method for printing an image onto a medium using a coating solid to interact with the printed image. More particularly, the present invention relates to an inkjet printer system including inkjet printing and coating a solid onto a medium to improve print quality and image release when the coating solid interacts with the jetted ink.
2. Description of the Related Art
Although the example illustrated in
The coating material is only applied and resident on the media or ITM in a liquid form, which thereby introduces extra water into the media. In addition, a liquid coating composition may increase paper cockle, and a coat thickness can easily vary by more than 100%.
Depending on the viscosity of the fluid coating material, the application of a uniform layer of a particular thickness of fluid can be very difficult to accomplish. If the coating fluids are very thin, then foam rolls or felt wicks can be used to apply coatings. Very thin fluids can also be jetted via inkjet-like print heads. If fluids are thicker or of a higher viscosity (to allow the use of chemicals which provide bigger print quality improvements or more rapid ink absorption effects), then more complicated application methods such as blade coating or roll coating become necessary. These methods are challenged to obtain uniform coatings at reasonable power consumptions, especially at process speeds desirable for ITM printing applications. It is especially difficult to distribute fluid uniformly across the width of a page-wide blade coater in order to produce a uniform coating. On the other hand, traveling blade coaters (those that are not page-wide) reduce throughput and increase machine width for drum printers, and are quite complicated to make operate bidirectionally. Blade coating methods also produce coating thicknesses which are highly speed dependent, which is a major limitation for printers which operate at more than one process speed (i.e. to produce outputs at different print resolutions).
In addition, the liquid coating material for ITM printers can have undesirable interactions with jetted liquid ink droplets, allowing the droplets to move or grow in size on the ITM rather than remaining fixed in place. However, the requirement to maintain flowability of the liquid coating material can limit the availability of the active chemical components, or concentration of the same, that can be included in the liquid coating material.
Examples of ITM printing systems using liquid coatings are described in U.S. Pat. Nos. 5,389,958, 5,805,191, and 5,677,719, all of which describe liquid coating material on an ITM, jetting ink onto the liquid coated surface of the ITM, and thereafter transferring the ink image to media through a nip generated by the ITM and a roller. Liquid coating systems require fluid handling hardware, including subsystems to store fluids, to move them from the storage vessel to the coating system, to apply them to an ITM, and to clean off residue after image transfer. These subsystems also have issues with fluid containment, which may restrict the orientation of printers during use or shipping. Liquid coating systems have been used to improve print quality for inkjet printers. As noted above, the liquid coatings usually interact with components of the ink, flocculating pigment particles, fixing dyes, or affecting absorption of ink components into the media, for example. Examples of such liquid coating techniques have also been illustrated in U.S. Pat. Nos. 6,183,079 and 6,196,674.
The present inventors have concluded that rather than applying liquid coatings, it would be more advantageous to apply coatings in a solid form. In addition, it is difficult to control the application of the liquid coating layers for thin even coating layers, while the application of a coating solid layer does not suffer from this limitation. Thus, a previously unknown method and apparatus for application of a coating solid layer, performing destabilization of a colorant in an ink, would appear to be necessary.
U.S. Pat. No. 6,059,407 describes a process where efficient transfer of an ink image from an ITM is accomplished with a particular applied transfer drum material and a solid surfactant. In U.S. Pat. No. 6,059,407, several different low surface energy rubber materials were used, each providing for highly efficient release of the ink image from the ITM. However, print quality defects resulted from the low surface energy of these particular rubber materials, with the ink image moving and flowing significantly on the surface of the low surface energy rubber materials. To counter this effect, this U.S. Pat. No. 6,059,407 describes applying a surfactant, in a solid form, to the surface of the drum, with the surfactant having an HLB (hydrophilic-lipophilic balance) value between 2 and 16. HLB is a reference value to compare different surfactants in a relative sense. The actual value needed would be dependent on drum surface and ink formulation. U.S. Pat. No. 6,059,407 also describes most of the classes of surfactants available.
However, the sole purpose of applying the solid surfactant in this U.S. Pat. No. 6,059,407 is to control the spread of the ink image on the surface of the ITM, caused by the unique low surface energy rubber materials. Thus, the surfactant does not aid in the transfer efficiency of the ink image to the media, e.g., performing destabilization of a colorant in an ink, but rather, merely compensates for a low surface energy aspect of the unique transfer drum materials. In addition, after application of the solid surfactant material, it would appear that the surfactant material is liquefied into a liquid layer while on the surface of the transfer drum.
Conversely, the purpose of the liquid coatings, and the inventors' coating solids, is to effect efficient transfer of ink colorant to the media. Typically, surface energy modifications are not necessary to maintain print quality. Rather, if image spread is observed, it can be modified within the ink formulation. Embodiments of the present invention may not even include any surfactant in their solid material formulations, while also noting that surfactants may not diffuse with an ink on a time scale required in printing systems to perform this destabilizing operation.
One aspect of the present invention is to provide a method and apparatus for inkjet printing and coating a solid onto a medium to improve print quality and image release when the coating solid interacts with the jetted ink.
A further aspect of the present invention is to provide a method and apparatus for printing using an inkjet print system and coating a solid onto a medium to improve print quality and image release where the coating solid interacts with the jetted ink to destabilize colorant in the ink.
Aspects and advantages of the present invention are achieved with embodiments of a ink jet printer apparatus. The apparatus includes an ink-jet print head to jet ink, a coating solid to interact with ink to destabilize colorant in the ink, and a coating holder to support the coating solid, wherein the coating holder transfers a portion of the coating solid onto a medium to form a coating solid layer.
In addition, the medium can be an intermediate transfer drum or belt, a media support medium, a transfer medium, or a medium, including paper.
The coating solid can be transferred to the medium before the medium is on a media support medium, where ink is jetted onto the medium, or the coating solid can be applied to the medium while the medium is on a media support medium.
Further, the transfer of the coating solid portion to the medium may include first applying the coating solid portion to a transfer medium, e.g., a roller or belt, with the applied coating solid then being transferred from the transfer medium to the medium. Alternatively, the jetting of ink to the medium can be performed after a corresponding portion of the medium has withdrawn from contact with the transfer medium where the coating solid is transferred to the medium.
The coating holder may also be contained in a removable cartridge, along with a cleaning blade and a waste bin.
A processor may be included in the inkjet printer to control a speed of the medium and/or a contact pressure of the coating solid to the medium to control an application thickness of the coating solid on the medium. A contact pressure of the coating solid to the medium may also be controlled to be less than 5 psi, or even less than 2 psi.
In addition, the coating holder may also contain a seal to enable sealing of the coating solid when coating is not required.
An additional coating solid may be included in the inkjet printer to form an additional coating solid layer, with a width of the coating solid layer and a width of the additional coating solid layer cooperating to generate an overall predetermined layer width on the medium. Further, the separate coating solid layers partially overlap widthwise.
Similarly, the coating solid may be one of a plurality of coating solids in the ink-jet printer, wherein one or more coating solids are used to apply the coating solid layer with a variable and/or adjustable width. In addition, the coating holder may be rotatable to change a width of the coating solid layer.
A proximity sensor may be included in the inkjet printer to determine a proximity of an end of the coating solid to the medium. Further, a detector may similarly be included to determine an amount of coating solid present in the coating holder.
The coating solid may be a gel. In addition, the coating solid layer may have a thickness of 0.1 to 10 microns, or even 0.5 to 2 microns. The coating solid may also be in a roller form or a stick form, as well as not containing a surfactant. The coating solid may also contact the medium across an area having a working face height of less than 12 mm.
The coating holder may or may not traverse across a width of the medium, as well as potentially traversing in a helical pattern.
Further aspects and advantages are achieved in accordance with embodiments of the present invention by a removable cartridge for use in a printer applying a coating solid to a medium and an ink release process, by a print head in the printer, with the cartridge including a coating holder supporting the coating solid to generate a solid layer of the coating solid on the medium, when applied to the medium, with the coating solid destabilizing colorant in ink used in the ink release process. The cartridge may also include a cleaner blade and a waste bin. Further, the working face of the coating solid may be less than 12 mm.
Other aspects and advantages are achieved in accordance with embodiments of the present invention by a method of printing within a printer, including applying a coating solid to a medium to form a layer of the coating solid, in a solid form, having predetermined thickness, applying ink toward the medium, wherein the layer of coating solid interacts with the applied ink to destabilize colorant in the ink.
The medium may be an intermediate transfer medium, a media support medium, a transfer medium, or media, such as paper. In addition, the intermediate transfer medium may have a roughness of 0.05 microns to 1.5 microns Ra.
The coating solid may be applied to the medium prior to placing the medium on a media support medium, where the ink application is performed, or while media is present on the media support medium
The ink may be applied to the medium without an intermediate transfer medium or media support medium. Alternatively, the coating solid and ink may both be applied to the medium, which is an intermediate transfer medium, with another medium being made to come into contact with the intermediate transfer medium to transfer the coating solid and ink to the other medium.
A speed of the medium and/or contact pressure of the coating solid to the medium may be controlled to control the thickness of the coating solid layer. Further, the contact pressure of the coating solid to the medium may be controlled to be less than 5 psi, or even less than 2 psi.
The coating solid may be angled, such that the coating solid is arranged to be non-perpendicular to a surface of the medium at a point of contact with the medium, to control vibration and/or chatter.
Further, at least one additional coating solid layer may be applied to the medium, with a width of the coating solid layer and an overall width of the at least one additional coating solid layer cooperating to generate an overall predetermined layer width on the medium. The separate coating solid layers may also partially overlap widthwise. Similarly, the width of the coating solid layer may be changed by applying one or more coating solids, wherein the coating solid is one of the one or more coating solids. Further, a coating holder holding the coating solid may be rotated to control a width of the coating solid layer.
In addition, a friction force between the coating solid and the medium may not change a contact pressure between the coating solid and the medium when generating the coating solid layer.
The coating solid layer may similarly be controlled to have a thickness of 0.1 to 10 microns, or even 0.5 to 2 microns. In addition, the coating solid may traverse across a width of the medium to apply the coating solid layer, and potentially in a helical pattern.
Additional aspects and advantages are achieved in accordance with embodiments of the present invention by an ink jet printer including a media support medium, an ink-jet print head, and a coating holder supporting a coating solid, wherein the coating holder is operable to transfer the coating solid onto at least a portion of a medium to form a coating solid layer before movement of the medium to the media support medium, with the ink-jet print head jetting ink onto the medium while on the media support medium.
Still additional aspects and advantages are achieved in accordance with embodiments of the present invention by an ink-jet printer including a media support medium, an ink-jet print head, and a coating holder supporting a coating solid, wherein the coating holder is operable to transfer the coating solid onto a medium mounted on the media support medium to form a coating solid layer on the medium, with the ink-jet print head jetting ink for transfer of an image to the medium while mounted on the media support medium.
Further aspects and advantages are achieved in accordance with embodiments of the present invention by an ink-jet printer including an ink-jet print head, and a coating holder supporting a coating solid, wherein the coating holder is operable to transfer a layer of the coating solid onto a medium at an upstream location, to form a coating solid layer on the medium, before the ink-jet print head jets ink to the medium at a downstream location.
The inkjet printer may further include a roller to pull the medium past the upstream location, with the roller being before the downstream location.
Transfer of the layer of the coating solid onto the medium may also be performed by generating a coating solid layer on a transfer medium and transferring the coating solid layer on the transfer medium to the medium, with the transfer medium potentially being a roller with a surface roughness of 0.3 microns to 2.0 microns Ra.
In accordance with preferred embodiments of the present invention as noted above, a method and apparatus can be achieved for inkjet printing and coating a solid onto a medium that improves print quality and image release where the coating solid interacts with the jetted ink. As further noted above, conventional printing systems require the use of liquid coating solids, which are both burdensome to implement and present several quality related inadequacies. The embodiments of the present invention, as described herein, provide methods and apparatuses for implementing the use of solid coating materials to overcome these drawbacks.
These and other aspects and advantages of the invention will become apparent and more readily appreciated for the following description of the preferred embodiments, taken in conjunction with the accompanying drawings of which:
Reference will now be made in detail to the preferred embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to like elements throughout.
As noted above, embodiments of the present invention are directed toward a printing system using a solid coating material, capable of containing a destabilizing material, which applied ink can freely and rapidly diffuse into, or a destabilizing material that can freely and rapidly diffuse into previously applied ink. This may include networked liquid structures (gels), waxes (potentially including surfactant materials), low shear crystalline solids (graphitic type materials) or low melting polymers. The solid material may also include a flocculent that enables the destabilizing of colorant in ink, thereby improving print quality and image release to media.
According to at least one embodiment of the present invention, the coating solid is a freestanding organic based gel with lamellar crystal structure. A gel is a highly cross-linked network of relatively weak secondary bonds that act together to form a solid like structure. There is an ordering of this network to form crystal structures in the solid. Certain crystal structures have beneficial effects to the coating process such as a self limiting property that may prevent over or under coating of the material on the drum. They also may help in reducing the amount of energy necessary to coat the material and ensure uniformity of the coating. Under shear, rigid crystals of a lamellar crystal structure slide on the non-crystalline regions allowing flow of the rigid crystals. Alternative solid coating materials may also include waxes that contain destabilizing materials. Essentially, the term “solids,” in regards to the present invention, is a term that may encompass many materials in many different states, except a liquid state. For example, applied gel solids may have the appearance of a liquid, but still have states characteristics of a solid, e.g., an ordered internal structure.
In accordance with the preferred embodiments of the present invention, there is provided an ink-jet printing method and apparatus applying a coating solid onto a medium, such as media (e.g., paper), an ITM, or a transfer medium, for example, and printing onto the medium, or in the case of the transfer medium, printing onto another medium or media after transfer of the coating solid from the transfer medium. Combinations of methods and apparatuses of coating and printing can be interchanged with alternate methods and apparatuses for the ultimate ink jetting process.
As defined herein, an intermediate transfer medium (ITM) can be a medium onto which either ink alone or both a coating solid and ink is applied, with another medium (e.g., paper) thereafter being applied to the ITM to transfer, respectively, the ink alone or the coating solid and ink to the other medium.
A media support medium can be defined as a medium which supports another medium (e.g., paper), with the coating solid and/or ink being applied to the medium while on the media support medium. In another example, paper can be mounted on a media support medium and coating solid and ink can then be applied to the paper, with ink being applied to the medium after release from the media support medium. Similarly,
Further, a transfer medium can be defined as a medium which applies a coating solid to either an ITM, media on a media support medium, or media (e.g., paper) directly. For example,
The following embodiment of the present invention, relating to
As illustrated in
The coating system produces coating solid layer 50 on ITM 40 during one or more revolutions of ITM 40, after which coating stick 60 withdraws from contact with ITM 40, and a printing operation onto ITM 40 is performed, using print cartridge(s) 17 to generate an ink image 55, as illustrated in FIG. 3C. After completion of the printing operation, media 30 can be made to come into contact with ITM 40 through a nip generated between ITM 40 and roller 45. As media 30 advances through this nip, ink image 55 on ITM 40 is transferred to media 30, along with all or some of coating solid layer 50.
Although the coating solid is illustrated as being a coating stick, the solid coating material for embodiments of the present invention could easily be encapsulated as a coating solid roller, for example, such that contact with ITM 40 would result in a similar application of the coating solid to ITM 40. The above mentioned processes of
Coating stick 60 could be designed to cover the entire width of an imaging area of ITM 40, or it could be a fraction of that width. If the width of coating stick 60 is the full width of ITM 40, then coating stick 60 could remain stationary as ITM 40 rotates against it, which will be designated as a page-wide “stationary” coater. If the width of coating stick 60 is a fraction of the width of the imaging area of ITM 40, then coating stick 60 must travel axially across ITM 40, as ITM 40 rotates, coating in a helical (spiral) pattern, for example, which will be called a “traveling” coater. Each helical pass of coating stick 60 around ITM 40 could overlap somewhat with previous passes to improve coating uniformity on the surface of ITM 40. In addition to a helical application, coating stick 60 could be axially moved in a step-wise manner, such that a number of swaths are generated across the width of ITM 40, with the number of swaths depending on the width of coating stick 60 and ITM 40.
For machine width and throughput reasons, a coating system implementing a page-wide stationary coating stick is the preferred embodiment of this type of coating system. If a traveling coating system were used, throughput issues may require that the coating operation be performed simultaneously with a helical printing process, placing heavy demands on ITM velocity control during high-torque operations. A traveling coating system may also add extra length of ITM 40, for a lead-in distance ahead of a print head, and may require additional rotation of ITM 40 for the coating system to travel the lead-in distance. A traveling coating system may also require either a large heavy coating supply item (e.g., a coating stick) to move continuously during printing, or else the coating solid material must be liquefied in a fixed reservoir and then pumped to a coating head, where it can resolidify, and then be applied to ITM 40. Page-wide stationary coating systems would appear to avoid the potential drawbacks of traveling coating systems, though embodiments of the present invention are drawn to both page-wide stationary coating systems and traveling coating systems.
It is important to control both coating thickness and coating uniformity, both within a single coating and during potential successive coatings. Multiple coatings may merely include applying coating stick 60 to an area of ITM 40 for more than one rotation of ITM 40, in a stationary coating system, or perhaps through an application of coating stick 60 to ITM 40 for multiple travels across the width of ITM 40, in a traveling coating system. For each coating, sufficient active chemical substances to accomplish the required effects for printing and transfer or release must be delivered. However, supply yields have shown to be improved if only a minimum required coating thickness is produced each coating. To balance these needs, accurate control of the coating process is preferred.
The coating solid thickness can be controlled by controlling contact pressure exerted by coating stick 60 onto ITM 40, by the rotational speed of ITM 40, by a roughness and surface energy of the surface of ITM 40, by the number of revolutions of ITM 40 is in contact with coating stick 60, and by the chemical and physical properties of the coating solid.
An experimental 2 inch-wide solid coating system was developed as an example for a page-wide solid coating system, and is embodied in the coating systems illustrated in
Embodiments of the present invention are also directed toward allowing coating sticks to be easily installed and removed from solid coating systems.
Stick holder 81 could also include a stick advance mechanism to assure that the end of coating stick 60 maintains the correct relationship with the surface of ITM 40. In an initial embodiment, this stick advance function can be performed manually via a threaded rod, or automated (as will be described below in the discussion of FIG. 17). Although the coating system example discussed herein uses only a 2 inch wide coating stick, the coating systems illustrated in
Regarding the aforementioned coating systems illustrated in
In one embodiment, ITM 40 is a cast polyurethane coating applied over an aluminum drum core. A cast layer of Adiprene L42 polyurethane from Uniroyal Chemical was ground to improve the surface finish and then spray-coated with Chemglaze A074, a clear polyurethane coating from Lord Corporation. This composition is characterized below in Table I as “Urethane Drum A.” In this embodiment, ITM 40 was 9.5 inches in circumference, and significantly wider than coating stick 60. An average working face height of coating stick 60 was about 17.3 mm (in an “around-the-ITM” direction).
The coating solid layers produced by solid coating systems of
The power requirements to make these coating solids using these two different urethane ITMs, are also plotted in FIG. 11. Each data set in
The high power requirements illustrated in
To reduce power requirements while still maintaining ITM choice and full-speed coatings, it was determined that different coating sticks of different working face heights around ITM 40 could be used. By reducing the working face height, drum drag and torque are thereby reduced, while similar coating solid thicknesses on ITM 40 can still be achieved. Table II (below) details experimental data collected at an ITM surface speed of 53.3 ips. This experimental data is also plotted in
Table II illustrates coating solid thickness and power required for different coating stick working face heights (“Stick Thickness”). These coatings were generated on “Urethane Drum A”; the power requirements were for a 2 inch coater width.
Additional embodiments are directed toward an inkjet ITM printer that operates in a landscape mode, with a long edge of media 30 aligned along a length of ITM 40. To operate with letter-size and legal-size media, different image areas may be jetted onto ITM 40. That is, the legal-size image area may be a superset of the letter-size image area. Thus, page-wide coating sticks or rollers should be segmented to enable variable-size coatings of coating solid on ITM 40. To accomplish this segmentation, there may be several “sub-sticks” or “sub-rollers,” which contact ITM 40 along different axial areas across the width of ITM 40. For example, a single sub-stick could contact the surface of ITM 40 to generate a letter-size coating of coating solid, while two or more sub-sticks could be made to come into contact with ITM 40 to generate a legal-size coating of coating solid. Ideally, the sub-sticks or sub-rollers should be actuated separately to accomplish this task. To avoid coating defects at the interface between sub-sticks, for example, the sub-sticks may include overlapping joints, as shown FIG. 14A. The relative positions of the sub-sticks could be changed depending on whether a letter-size image is centered over the legal-size image or not.
Thus, if the ink transfer and release process is compatible, it is preferable to coat only particular regions of ITM 40, for a variety of media widths, since any excess coating probably needs to be cleaned off ITM 40 and disposed of. Coating solid can be transferred to a limited width of ITM 40, corresponding to the width of the narrow media.
Alternatively, if coating solid is applied to a greater width then a media width, coating solid that remains on ITM 40, along the portion of ITM 40 that did not contact the media, can be thereafter removed by a cleaning blade and transferred to a waste bin. An example of such cleaner blade/waste bin mechanism is disclosed in
However, in normal operation with full-width media, such a cleaner blade operation would result in a waste of coating solid, thereby reducing the potential coating yield. Therefore, it is desirable to operate the system without using a cleaner blade. Unfortunately, coating narrow media without using a cleaning blade can lead to differential wear of the coating stick. The portion of the coating stick aligned with the narrow media will progressively wear as additional media are coated, resulting in this differential wear, and resulting in coating defects.
An alternate solution to this problem uses a belt ITM, rather than a drum, together with a mechanism for rotating coating stick 60.
In an additional embodiment, a doctor blade may be included in the coating system, to assure coating uniformity or to modify the coating thickness. A doctor blade could be added right at the edge of coating stick 60 or it could be placed farther around ITM 40. The doctor blade serves to level the applied coating solid, both setting the thickness and smoothing the coating solid to improve coating uniformity. Some coating defects that could be improved by the addition of a doctor blade include both across-the-ITM coating defects, which might be caused by improper alignment of coating stick 60, or the aforementioned differential wear of coating stick 60. Around-the-ITM coating defects include marks made by coating sticks when they land on an ITM, or when they are lifted away from an ITM. Both types of coating defects could be reduced or eliminated by the inclusion of a doctor blade. The doctor blade would also prevent any coating debris from contacting inkjet print heads, which depending on the coating chemistry, could injure or destroy the print heads.
An additional embodiment of the present invention includes a capping station to seal coating stick 60 from the external environment. The sealing of coating stick 60 from the environment is desirable since a coating stick's properties may be modified by exposure to different humidities or extreme temperatures. The sealing of coating stick 60 can be accomplished with a separate capping station that would seal the open ends of coating stick 60 and stick holder 81. Alternately, coating stick 60 could be capped by pressing it against ITM 40 when the printer is not being operated. Flexible seals around the perimeter of the working face of coating stick 60 could complete a seal. This would avoid the need for a separate capping station, and avoid the space and mechanisms needed to move coating stick 60 to such a station.
In a further embodiment of the present invention, an alternate mechanism for moving coating stick 60 into contact with ITM 40 could be used. The aforementioned mechanisms, as shown in
In yet another embodiment of the present invention, a transfer medium, e.g., a roller or belt, could be arranged between coating stick 60 and ITM 40. Coating stick 60 would first apply coating solid to the transfer medium, which would then in turn apply coating solid to ITM 40. The use of a transfer medium could provide several benefits. First, it allows for different surface speeds of the stick coating process on the transfer medium and the transfer process to ITM 40. In this manner, the coating process to the transfer medium could be maintained at a constant speed even while an ITM 40 was operated at different speeds (e.g. to support different printing resolutions). Second, the use of a transfer medium permits a film-split between the transfer medium and ITM 40, leaving some coating solid on the transfer medium after a transfer of coating solid to ITM 40.
If it were necessary to use a certain set of coating stick coating parameters that created an undesirably thick coating solid layer, then a film-split between the transfer medium and ITM 40 could reduce the thickness of the eventual coating on ITM 40 to a desired thickness. For some applications, the transfer medium may be required to have an equal diameter (roller) or length (belt) as ITM 40 to transfer a complete coating of the coating solid in a single rotation. For other applications, the diameter or length of the transfer medium could be reduced, thereby accepting a coating solid at one angular position while continuously transferring it to ITM 40 at another angular position. Depending upon the relative sizes of ITM 40, the film-split ratio desired, and the application of coating solid, the transfer medium might rotate or advance the same speed, faster, or slower than ITM 40. The coating application of coating solid to the transfer medium may also occur simultaneously with the transfer of the coating solid to ITM 40, or it might precede it in time. The below discussed embodiments relating to
It is also desirable to have a coating system that can operate at a variety of ITM speeds to match a range of inkjet printing process speeds. For this to happen, either the coating parameters (thickness and uniformity) must be insensitive to ITM speed over the range of interest, or else another coating setting must be changed to restore the desired coating parameters at a given speed. This can most easily be accomplished by changing contact pressures as speed changes.
Another possible embodiment of the present invention includes changing the contact angle of coating stick 60 on ITM 40. The aforementioned embodiments discussed pushing the coating stick onto ITM 40 along a radial line of ITM 40, essentially with a zero angle along the radial line of ITM 40. However, if this angle is changed, either steeper or shallower, vibration modes of coating stick 60 against ITM 40 will change. This can be important during either a static portion of the coating process, while coating stick 60 is sliding along the surface of ITM 40, or a dynamic portion of the coating process, while coating stick 60 and ITM 40 are engaging or disengaging. In addition to minimizing and controlling vibration, the angling of coating stick 60 can also affect and reduce chatter. Chatter can be considered an oscillatory or repetitive bouncing, of a coating stick, on and off of a drum or belt, which results in an uneven or irregular coating application.
Additional embodiments of the present invention could include the coating process for an ITM inkjet printer including the addition of heat from stick holder 81 or the surface of ITM 40.
An additional embodiment of this invention, as illustrated in
As illustrated in
An advantage of this embodiment is that it was conventionally necessary, in some high-end graphics implementations, to use pre-coated media in inkjet printers that would then print onto the pre-coated media either using a media support medium or by printing onto the media directly. However, according to embodiments of the present invention, media can be coated within a printer, thereby negating the need of using specialty pre-coated media, which can be expensive.
In a further embodiment of the present invention, and as briefly mentioned previously, coating stick 60 can be applied first to transfer medium 130, e.g., a roller or belt, and thereafter transferred directly to media 30, as illustrated in
Although the following discussion of
As illustrated in
Similarly, in additional embodiments, the replaceable cartridge could include multiple coating sticks and/or holders, at least as discussed above. Alternatively, each element could be replaced individually. Waste bin 160 can be sized to hold all the waste material, as well as media dust and other contaminants that may accumulate during the useful life of each coating stick. In addition, a doctor blade (not shown) could be placed in contact with transfer medium 130 between the contact point of coating stick 60 and transfer medium 130 and the nip between transfer medium 130 and backup roller 135 to smooth out the coating solid before transfer to media 30. The amount of coating solid transferred to media 30 is controlled primarily by coating stick 60 contact pressure, transfer medium 130 surface roughness, transfer medium 130 surface energy, and coating stick 60 properties.
The removable cartridge could be mounted in housing 150, which can rotate about pivot 180. Spring 210 would exert a force on housing 150, thereby causing housing 150 to rotate about pivot 180, causing coating stick 60 to make contact with the surface of transfer medium 130. Spring 210 can thus control at least the initial contact pressure between coating stick 60 and transfer medium 130. As coating solid is transferred from coating stick 60 to transfer medium 130, housing 150 is further caused to rotate under the action of the spring, moving the replaceable cartridge closer to transfer medium 130. To control the proximity of coating stick 60 to the surface of transfer medium 130, proximity sensor 220 has been mounted on housing 150 to detect the distance between coating stick 60 (or the replaceable cartridge containing coating stick 60) and transfer medium 130. Based on the detected proximity, a control unit (e.g., processor 20 illustrated in
In an additional embodiment of the present invention, a coating solid is applied directly onto media, i.e., without requiring an ITM or media support medium, as illustrated in
As illustrated in
Since coating cannot begin until media 30 is controlled by feed rollers 30, there may be a small region at least at the leading portion of media 30 which cannot be coated. To minimize this uncoated leading portion, feed rollers 115 and 120 should be placed close to each other, and feed rollers 120 should be placed as soon after coating stick 60 as possible. To prevent paper skew caused by drag forces on media 30 from the coating stick 60, feed rollers 115 and 120 should also be page-wide.
After the coating solid is applied to media 30 a jetting of ink can be performed by ink cartridge(s) 17 either while the coating process is commencing or after the same. FIGS. 18A-18E illustrate print cartridge(s) 17 being directly after the coating area and above media 30. However, alternative printing processes could be instituted. For example,
Above embodiments have shown coating solid applicators in a “stick” or “roller” supply configuration. The coating solid applicator can be moved into engagement with a medium to be coated (e.g., an ITM, media on a media support medium, transfer medium, or media directly). After moving into engagement, the coating solid applicator may then be held stationary against the medium (for page-wide coaters), or travel at a velocity perpendicular to the medium surface motion (for traveling coaters). However, it is conceivable that additional relative motion between the coating solid applicator and the medium could benefit the coating process. For example, forcing the coating solid applicator to vibrate in a controlled fashion (either during page-wide or traveling mode) could result in improved area coverage and/or improved coating uniformity.
Thus, embodiments of the present invention are directed toward applying coating solids for use in printing processes. Contrary to conventional systems, coatings are made using coating solid materials rather than liquid coating materials, providing a number of advantages. The teaching of these embodiments could be applied to any solid material which forms a coating solid, whether by shear thinning and liquefication or by abrasion or other mechanisms.
In addition, although only a limited number of solid materials have been disclosed herein, the present invention is not limited thereto. Thus, a coating solid could encompass any non-liquid material performing destabilization of a colorant in an ink. Further, although embodiments of the present invention may have been directed toward inkjet printers, the present invention is not limited thereto.
Therefore, although a few preferred embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that changes may be made in these embodiments without departing from the principles and spirit of the invention, the scope of which is defined in the claims and their equivalents.
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