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METHOD FOR ELIMINATION OF MISDIRECTED SATELLITE DROPS IN THERMAL INK JET PRINTHEADS

IP.com Disclosure Number: IPCOM000027126D
Original Publication Date: 1995-Jun-30
Included in the Prior Art Database: 2004-Apr-07
Document File: 2 page(s) / 173K

Publishing Venue

Xerox Disclosure Journal

Abstract

[Reprinted because of changes to the text of this disclosure. Originally printed in the JanuarylFebruary 1995 Xerox Disclosure Journal] Misdirected satellite drops in thermal ink jet devices may cause observable print quality defects in a thermal ink jet printer. This is especially true when the thermal ink jet printing device is used in bi-directional carriage printing applications and the satellite drops are misdirected along the process direction. In such cases, satellite drops can fall within the main spot when printing in one direction and outside the main spot in the other direction. When misdirected drops fall outside the main spot, the resultant drop is no longer round, but rather elongated in shape. The effectively larger and mis-shaped spot may result in optical density shifts in fine toned print patterns as well as ragged edges on printed text and lines. Whether or not the satellite related print quality defects are observed depends on the direction of relative motion between the printhead and the print medium, the process speed, and the throw distance from the nozzles to the print medium. If the elongation occurs along the process direction, the physical origin of the misdirected satellite has been observed to be caused by a "tail bending" of the ink drop ligament prior to break-off from the nozzle face. For Xerox thermal ink jet devices, this tail bending has typically been directed toward the top or apex of the channel structures.

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XEROX DISCLOSURE JOURNAL

METHOD FOR ELIMINATION OF MISDIRECTED SATELLITE DROPS U.S. C1.3461140 IN THERMAL INK JET
PRINTHEADS
Robert V. Lorenze, Jr.

Daniel E. Kuhman

Proposed Classification

Int. C1. Gold 15/18

[Reprinted because of changes to the text of this disclosure. Originally printed in the JanuarylFebruary 1995 Xerox Disclosure Journal]

Misdirected satellite drops in thermal ink jet devices may cause observable print quality defects in a thermal ink jet printer. This is especially true when the thermal ink jet printing device is used in bi-directional carriage printing applications and the satellite drops are misdirected along the process direction. In such cases, satellite drops can fall within the main spot when printing in one direction and outside the main spot in the other direction. When misdirected drops fall outside the main spot, the resultant drop is no longer round, but rather elongated in shape. The effectively larger and mis- shaped spot may result in optical density shifts in fine toned print patterns as well as ragged edges on printed text and lines. Whether or not the satellite related print quality defects are observed depends on the direction of relative motion between the printhead and the print medium, the process speed, and the throw distance from the nozzles to the print medium. If the elongation occurs along the process direction, the physical origin of the misdirected satellite has been observed to be caused by a "tail bending" of the ink drop ligament prior to break-off from the nozzle face. For Xerox thermal ink jet devices, this tail bending has typically been directed toward the top or apex of the channel structures.

In order to characterize the magnitude of satellite related print quality defects as a function of changes in front face geometries, a metric referred to as the spot aspect ratio (SAR) is used. This metric is simply the ratio of the length of a spot, in the process direction, divided by the width of the spot, in the channel- to-channel direction. For thermal ink jet devices operating under typical printer conditions, satellite related print quality defects have been found to be objectionable when SAR values of printed spots exceed levels of approximately
1.1.

A series of experiments in which detailed measurements of SAR were made as a function of changes in front face geometries has shown that the magnitude and direction of the misdirected satellites correlate extremely well with a parameter referred to as the effective meniscus tilt angle (@TILT) or EMTA. Although the meniscus of a column of ink in a channel is a relatively complex 3-dimensional surface that changes dramatically during drop firing and channel refill, a greatly simplified model of this surface at static equilibrium would have the meniscus pinned at the edges of the channel as it terminates at the front face of the device. This model is a reasonable representation of the

XEROX DISCLOSURE JOURNAL - Vol. 20, No. 3 May/Ju...