Patent Application
20140285576
In some inkjet printers, a media wide arrangement of stationary printheads is used to print on paper or other print media moving past the array. In one type of print bar for media wide inkjet printers, individual printheads are mounted across the width of the media path.
The same part numbers designate the same or similar parts throughout the figures. The figures are not necessarily to scale. The relative size of some parts is exaggerated for clarity.
A print bar assembly has been developed for media wide inkjet printers in which individual printheads are mounted lengthwise end-to-end in a staggered configuration across the width of the media path. A flex circuit with signal traces is connected to bond pads on each printhead along the upstream side of the printhead, where the print media first arrives for printing. A protective covering is applied to the electrical connections to protect them from the corrosive effects of ink and other environmental degradation. In the past, for other printer designs, signal traces were usually connected to bond pads located at the end of the printhead. In the conventional “end-connect” configuration, the protective covering on the electrical connections on the narrow, end of the printhead also covers the corners of the printhead, protecting them against damage from paper striking the printhead. One unforeseen effect of a “side-connect” configuration in the new print bar, in which the printheads are oriented long-side across the media path, is leaving the corners of the printhead exposed—the protective covering applied to the electrical connections does not extend to the corners of the printhead as it does with the end-connect configuration. Consequently, the corners of the printhead are susceptible to damage from print media striking the printhead during printing.
A new printhead structure has been developed to reduce the risk of damage to printheads with exposed corners. In one example of the new printhead structure, a generally rectangular nozzle plate has rounded corners and a stepped perimeter edge profile. The stepped edge profile maintains the desired overall thickness of the nozzle plate but reduces the thickness (height) of the side wall that can obstruct the print media, allowing the media to pass more easily over the printhead and minimizing any impact forces on the edge of the nozzle plate. In addition, rounding the corners of the nozzle plate eliminates the abrupt edge at each corner where testing shows the greatest impact damage was occurring in the conventional design.
Implementations of the new printhead structure are not limited to a nozzle plate or to printheads with a flex circuit side-connect. For example, the new structure may be implemented in other printhead components exposed to media impact during printing or that might otherwise benefit from the new edge configuration. Accordingly, the examples shown in the figures and described in this Description illustrate but do not limit the invention, which is defined in the Claims following the Description.
As used in this document, a “printhead” means that part of an inkjet printer or other inkjet type dispenser that dispenses fluid from one or more openings. A “printhead” is not limited to printing with ink and other printing fluids but also includes inkjet type dispensing of other fluids and/or for uses other than printing.
Referring now specifically to
Resistors 26 are formed in a resistive layer 32 over dielectric 18. A typical resistive layer 32 is, for example, made of tungsten silicide nitride (WSiN), tantalum silicide nitride (TaSiN), tantalum aluminum (TaAl), tantalum nitride (Ta2N), or combinations of these materials. A conductive metal layer 34 formed on (or under) resistive layer 32 can be used to supply current to resistors 26 and/or to couple resistors 26 to a control circuit or other electronic circuits in printhead 10. A typical conductive layer 34 is, for example, made of platinum (Pt), aluminum (Al), tungsten (W), titanium (Ti), molybdenum (Mo), palladium (Pd), tantalum (Ta), nickel (Ni), copper (Cu) with an inserted diffusion barrier, and combinations of these materials. A passivation layer 36 is formed over conductive metal layer 34 as a dielectric and as a barrier against cavitation (in chamber 24), oxidation, corrosion, and other environmental conditions. A typical passivation layer 36 is, for example, made of silicon carbide (SiC), silicide nitride (SiN), TEOS, and combinations these materials.
Referring again to both
In the example shown, nozzle plate 38 is formed in three layers—a first, thinner layer 42 formed on passivation layer 36 and two thicker layers 44 and 46 formed over first layer 42. While all three layers 42, 44, 46 help define dispensing chamber 24 in this example, nozzles 22 are formed in the outermost, third layer 46. Each nozzle plate layer 42, 44, 46 is made of an SU8 epoxy polymer or other suitable material. The thinner, first nozzle plate layer 42 is sometimes referred to as the “primer” layer because it is a thin bottom layer that acts as a buffer to help prevent the highly stressed upper layers 44 and 46 from peeling the underlying thin films. Second layer 44 is sometimes referred to as the “chamber” layer because it forms much of the sidewall of dispensing chamber 24. Third layer 46 is sometimes referred to as the “nozzle” layer because nozzles 22 are formed in this layer.
Third layer 46 terminates inboard of second layer 44 along the perimeter of printhead 10 to form a step 43, as best seen in
The edge profile of the nozzle plate has been made more robust, less susceptible to media damage, by (1) adding a step 43 between the edges of nozzle plate chamber (second) layer 44 and nozzle (third) layer 46 and (2) rounding the corners 52 of each layer 44 and 46. Although a three layer nozzle plate 38 is shown in which the stepped edge profile is formed between layers, more or fewer layers may be used to form a stepped edge nozzle plate 38 including, for example, a single layer nozzle plate 38 in which one or more steps are formed along the perimeter of the single layer. With multiple layers, however, the thickness of each layer may be tailored to a specific function. Usually, the primer layer is thinner for buffering and chamber and nozzle layers are thicker for fluid routing. Multiple layers also help isolate the internal stresses in the individual chamber and nozzle layers from other structures.
The stepped edge configuration maintains the desired overall thickness of nozzle plate 38 but reduces the thickness (height) of the side wall that can obstruct the print media, allowing the media to pass more easily over the printhead and minimizing impact forces on the nozzle plate. Rounding the corners of nozzle plate 38 eliminates the abrupt edge at each corner where testing showed the greatest impact damage was occurring. In addition to substantially reducing impact damage, this stepped, rounded configuration has the dual advantages of not adding steps (or cost) to the fabrication process and allowing a flat outer surface that will not impede the cleaning wiper.
As noted at the beginning of this Description, the examples shown in the figures and described above illustrate but do not limit the invention. Other examples are possible. Therefore, the foregoing description should not be construed to limit the scope of the invention, which is defined in the following claims.
