Browse Prior Art Database

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

IP.com Disclosure Number: IPCOM000027050D
Original Publication Date: 1995-Feb-28
Included in the Prior Art Database: 2004-Apr-07
Document File: 2 page(s) / 162K

Publishing Venue

Xerox Disclosure Journal

Abstract

Misdirected satellite drops in thermal ink jet devices may cause observable print quality defects of a thermal ink jet printer. This is especially true when the thermal ink jet printing device is used in bi-directional carriage printing applications, where satellite drops can fall within the main spot when printing in one 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 misshaped may result in 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 a nozzle to a copy sheet. The elongation always occurs along the process direction, and 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 thermal ink jet devices, this tail bending has typically been directed toward the top or apex of the channel structures.

This text was extracted from a PDF file.
At least one non-text object (such as an image or picture) has been suppressed.
This is the abbreviated version, containing approximately 53% of the total text.

Page 1 of 2

XEROX DISCLOSURE JOURNAL

METHOD FOR ELIMINATION OF MISDIRECTED SATELLITE DROPS U.S. C1.436/140 IN THERMAL INK JET
PRINTHEADS
Robert V. Lorenze, Jr.

Daniel E. Kuhman

Proposed Classification

Int. C1. Gold 15/18

Misdirected satellite drops in thermal ink jet devices may cause observable print quality defects of a thermal ink jet printer. This is especially true when the thermal ink jet printing device is used in bi-directional carriage printing applications, where satellite drops can fall within the main spot when printing in one 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 misshaped may result in 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 a nozzle to a copy sheet. The elongation always occurs along the process direction, and 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 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 (SARI is used . This metric is simply the ration 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, 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 in a filled channel would be 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 actual situation as long as it is assumed that front face surfaces have a hydrophobic coating which is effective in minimizing front face wetting. If the channel is symmetric at the front...