Browse Prior Art Database

THERMAL INK JET PRINTHEAD PROTECTIVE LAYERS

IP.com Disclosure Number: IPCOM000026856D
Original Publication Date: 1994-Feb-28
Included in the Prior Art Database: 2004-Apr-06
Document File: 8 page(s) / 647K

Publishing Venue

Xerox Disclosure Journal

Abstract

A thermal ink jet printhead having a protective layer that extends printhead life is disclosed. The protective layer is made of a thin film material having a melting point not less than about 1000°C. A deposition process for preparing the thin film material produces a thin film material having, at an operating temperature for the thermal ink jet printer, a thermal conductivity coefficient not less than about 10 W/m.K, a compressive yield strength not less than about 1400 MPa and a compressive residual stress of not greater than about 1200 MPa. The protective layer is smooth, substantially free of pores and impervious to stress corrosion or hydrogen stress cracking at a hydrogen uptake rate of less than about 5 ppm. The protective layer may also contain an adhesion enhancing region between the protective layer and an underlying layer or an anodic region contiguous with an underlying thin film material of the protective layer. The adhesion enhancing region is a reaction product between an ambient gas and the thin film material of the protective layer and extends only to the grain boundaries of the protective layer. The contiguous anodic region is substantially free of pores, has a homogeneous composition, protects an underlying thin film material against corrosive species and hydrogen and is formed by anodization of the underlying thin film in an aqueous electrolytic process.

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Page 1 of 8

XEROX DISCLOSURE JOURNAL

THERMAL INK JET PRINTHEAD PROTECTIVE LAYERS U.S. C1.346/140 Igal E. Klein
Cathie J. Burke
Roberto
E. Proano
Renato P. Apollonio
Robert
V. Lorenze
Daniel
0. Roll

Proposed Classification

Int. C1. Gold 15/18

Deposited FIG. IA Film

FIG. 16

2 FIG. rn 1, 4'

2

FIG. 3

/ 4 '\ /3

FIG. 4 I

XEROX DISCLOSURE JOURNAL - Vol. 19, No. 1 Januarymebruary 1994 17

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THERMAL INK JET PRINTHEAD PROTECTIVE LAYERS(Cont'd)

A thermal ink jet printhead having a protective layer that extends printhead life is disclosed. The protective layer is made of a thin film material having a melting point not less than about 1000°C. A deposition process for preparing the thin film material produces a thin film material having, at an operating temperature for the thermal ink jet printer, a thermal conductivity coefficient not less than about 10 W/m.K, a compressive yield strength not less than about 1400 MPa and a compressive residual stress of not greater than about 1200 MPa. The protective layer is smooth, substantially free of pores and impervious to stress corrosion or hydrogen stress cracking at a hydrogen uptake rate of less than about 5 ppm. The protective layer may also contain an adhesion enhancing region between the protective layer and an underlying layer or an anodic region contiguous with an underlying thin film material of the protective layer. The adhesion enhancing region is a reaction product between an ambient gas and the thin film material of the protective layer and extends only to the grain boundaries of the protective layer. The contiguous anodic region is substantially free of pores, has a homogeneous composition, protects an underlying thin film material against corrosive species and hydrogen and is formed by anodization of the underlying thin film in an aqueous electrolytic process.

Investigations of protective layers in ink jet printhead devices suggests that residual stress components of thin film material protective layers may be significantly enhanced by reducing residual compressive or tensile stresses which exist in protective thin film materials applied to a substrate or underlying layer. A residual stress may be compressive (namely the film would like to expand parallel to the surface), or tensile (the film would like to contract). A film covering just one side of a substrate, exhibiting compressive stress would lead to a convex shape, while a film under tensile stress would lead to a concave shape, as represented in Figures la and lb. In thermal ink jet printheads, mechanical residual stresses in thin films contribute to premature failure of the printhead device, namely metal cracking in delamination which substantially reduces the anti-cavitation properties of the protective layer and permits permeation of corrosive species from ink compositions. Such conventional printheads fail to withstand the high frequency, cavitational forces exerted on the s...