1. Technical Field
The invention relates to ink jet printers. More particularly, the invention relates to an ink jet printer having low ink volume deposition per print pass.
2. Description of the Background Art
Digital UV inkjet printers have been in commercial production since 2000. The early printers used relatively low resolution print heads (90-100 dpi) with low numbers of nozzles per color (256-512) and printed at rates of approximately 250 square feet per hour (sf/h). Over time, the native resolutions of print heads have increased and the number of nozzles per color has increased in an attempt to build faster and faster printers. To achieve the higher print speeds, printer designers have arrayed multiple print heads in efficient arrangements where high resolution can be achieved as multiples of the native resolutions of the individual print heads. For instance, as in the EFI Vutek QS3200r, three Seiko print heads, native 180 dpi of 510 nozzles each can be arranged as three print heads per color in an array of 540 dpi of 1530 nozzles per color. Where a single print head per color results in a printer of 300 sf/h, the multi-head array printer has a top throughput of 900 sf/h.
As moving carriage printers have been designed to increase throughput (speed), the number of nozzles and step size have increased leading to substantial issues with an artifact variously referred to as tire tracking, gloss banding, or differential gloss banding. The artifact manifests in a differential gloss between passes, e.g. left to right versus right to left, of the last pass printed by the print heads over the substrate.
The period of banding is the step size of the media under the traversing print heads. The result is similar to viewing a mowed lawn or baseball field and seeing the directional passes of the lawn mower. In UV inkjet printing this differential gloss is a highly objectionable artifact that limits the speed of the printer and usefulness of the printed image in high image quality applications, such as point-of-purchase (POP) signage.
A substantial amount of work has been done to minimize this highly objectionable artifact. Countermeasures that are used to minimize gloss banding, require more interlacing, and thus lead to reduced throughput of the printer, i.e. more passes at lower resolutions and smaller step sizes to reduce gloss banding and other print artifacts reduce throughput to one-half or less of the maximum speed capability of the printer. State of the art corrective methods that attempt to address this problem may be understood by resort to, for example, U.S. Pat. No. 6,789,867 and European patent nos. EP06651, EP471488A, and EP0518670.
It would be advantageous to provide a technique for UV curable ink jet printing that improves the output quality of a printer by minimizing or eliminating gloss banding or tire tracking.