Ink delivery system for an inkjet printhead

Information

  • Patent Grant
  • 6499835
  • Patent Number
    6,499,835
  • Date Filed
    Wednesday, January 23, 2002
    22 years ago
  • Date Issued
    Tuesday, December 31, 2002
    21 years ago
Abstract
An ink-firing element is provided. The ink-firing element has a resistor for generating ink droplets, a substrate atop which the resistor rests and a barrier layer atop the substrate. The barrier layer in a closed-loop design and at least partially defines an ink-firing chamber, which surrounds the resistor and temporarily contains ink. The ink-firing element also includes an orifice plate supported by the barrier layer for providing an orifice through which the ink droplets are ejected onto a medium and a trench in the substrate for replenishment of ink. The trench terminates at an outlet in the ink-firing chamber and is in fluid communication with an ink refill channel, which supplies ink from a reservoir to the ink-firing element.
Description




BACKGROUND OF THE INVENTION




This invention relates to inkjet printhead structures.




The basic concept of inkjet printing is an ink-firing element having an ink-firing chamber with an orifice for ejecting ink and an ink heating mechanism, generally a resistor, in close proximity to the orifice. In operation, the resistor is quickly heated. The heating transfers a significant amount of energy to the ink, thereby vaporizes a small portion of the ink and produces a bubble in the ink-firing chamber. This in turn creates a pressure wave which propels an ink droplet or droplets from the orifice onto a nearby recording medium such as paper.




Normally, the ink-firing chamber is formed by a semiconductor substrate atop which the resistor rests, an orifice plate which defines the orifice, and a barrier layer sandwiched between the substrate and the orifice plate for supporting the orifice plate. Ink flows from an ink reservoir through an ink refill channel to each ink-firing element. An ink conduit in fluid communication with the ink refill channel is provided in the barrier layer for refilling the ink-firing chamber subsequent to the vaporization process which ejects an ink droplet. The ink conduit is usually formed by creating an open portion in the barrier layer.




The orifice plate, especially if it is a flexible polymer orifice membrane, may sag at the place where the ink conduit exists, since the ink conduit, i.e., an open portion in the barrier layer, provides insufficient support to the part of the orifice plate thereabove. The sag consequently affects the flatness of the orifice plate. Such an effect on the flatness of the orifice plate may cause the orifice to be uncontrollably deformed or tilted thus resulting in inaccurate trajectory of the ink droplets and less than an optimum quality of printing.




Therefore, there is a need for a printhead in which sag of the orifice plate is reduced.




SUMMARY




In an embodiment according to the invention, an ink-firing element includes a resistor for generating ink droplets, a substrate atop which the resistor rests and a barrier layer atop the substrate. The barrier layer is in a closed-loop design and at least partially defines an ink-firing chamber, which surrounds the resistor and temporarily contains ink. The ink-firing element also includes an orifice plate supported by the barrier layer for providing an orifice through which the ink droplets are ejected onto a medium and a trench in the substrate for replenishment of ink. The trench terminates at an outlet in the ink-firing chamber and is in fluid communication with an ink refill channel, which supplies ink from a reservoir to the ink-firing element.




According to an aspect of the invention, a supporter is provided above the trench for supporting a portion of the barrier layer thereabove.




In another embodiment according to the invention, an ink-firing element includes a resistor for generating ink droplets, a substrate atop which the resistor rests, a barrier layer atop the substrate and an orifice plate supported by the barrier layer for providing an orifice through which the ink droplets are ejected onto a medium. The barrier layer partially surrounds the resistor and defines an ink-firing chamber. The ink-firing element also includes an ink conduit provided in the barrier layer for supplying ink from an ink refill channel to the ink-firing chamber. The ink refill channel supplies ink from a reservoir to the ink-firing element. Furthermore, the ink-firing element includes a trench provided in the substrate for supplementary replenishment of ink. The trench is in fluid communication with the ink refill channel and terminates at an outlet in the ink-firing chamber.




In an embodiment of a process for producing an ink-firing element, a supporting layer of a pre-defined pattern is first applied above a substrate atop which a resistor rests for generating ink droplets. The substrate is then etched to form a trench therein, and the trench is in fluid communication with an ink refill channel, which supplies ink from an ink reservoir to the ink-firing element. Subsequently, a barrier layer is attached atop the substrate. The barrier layer at least partially defines an ink-firing chamber and is positioned such that the trench in the substrate terminates at an outlet in the ink-firing chamber. After that, an orifice plate is placed above the barrier layer for providing an orifice through which the ink droplets are ejected onto a medium.




Other aspects and advantages of the invention will become apparent from the following detailed description taken in conjunction with the accompanying drawings, which illustrates by way of example the principles of the invention.











BRIEF DESCRIPTION OF THE DRAWINGS





FIG. 1

partially illustrates an ink-firing element according to a first embodiment of the invention;





FIG. 2

partially illustrates an ink-firing element according to a second embodiment of the invention;





FIG. 3

illustrates different types of supporter used in the preferred embodiments;





FIGS. 4A-4G

are top plan views illustrating a process for fabricating an ink-firing element according to the invention; and





FIGS. 5A-5G

are cross section views illustrating the process of FIGS.


4


A-


4


G.











DETAILED DESCRIPTION





FIG. 1

illustrates an isometric view of an ink-firing element


200


, that is, a portion of a printhead of a printer cartridge, in accordance with the invention. The ink-firing element


200


has a resistor


205


resting atop a semiconductor substrate


217


for generating ink droplets. An orifice plate


201


, such as a flexible polymer orifice membrane, is arranged such that an orifice


203


, which extends from the inner surface of the orifice plate


201


to the outer surface, is centered essentially over the resistor


205


for ejecting the ink droplets onto a print medium. A polymeric barrier layer


209


sandwiched between the substrate


217


and the orifice plate


201


is provided for supporting the above orifice plate


201


and for at least partially defining an ink-firing chamber


207


which surrounds the resistor


205


. In addition, as shown in

FIG. 1

, the barrier layer


209


is offset from an ink refill channel


215


, which supplies ink from an ink reservoir (not shown) of the cartridge. In a center feed construction, the ink refill channel


215


is etched through a portion of the substrate


217


. In an edge feed construction, the ink refill channel


215


can be formed from facing edges of two adjacent substrates.




The ink-firing chamber


207


, which is also defined by the orifice plate


201


and the substrate


217


, temporarily stores ink before an ink droplet is fired. In the embodiment of

FIG. 1

, the barrier layer


209


has a closed-loop structure, that is, a structure having a contiguous inner wall without any openings in the wall. The inner wall of the barrier layer defines the four sides of the ink-firing chamber


207


, and preferably, the barrier layer


209


has a uniform thickness. Such a closed-loop structured barrier layer provides additional support to the orifice plate


201


above for reducing sag of the orifice plate


201


.




In the embodiment, a trench


211


is provided in the substrate


217


for replenishing ink from the ink refill channel


215


to the ink-firing chamber


207


. The trench has an open end


213


to the ink refill channel


215


and terminates at an outlet


221


in the floor of the ink-firing chamber


207


so as to provide an ink flow path between the ink refill channel


215


and the ink-firing chamber


207


. The trench


211


can be formed by using etch technology to remove unwanted areas of the substrate. Preferably, the trench


211


is in a V-shape as shown in

FIG. 1

due to the nature of wet etch on silicon crystal. Preferably the width of such a trench is approximately the same as the width of the resistor


205


.




Furthermore, an additional supporting layer such as a silicon carbide or silicon nitride (hereinafter SiC/SiN) layer


311


can be provided between the substrate


217


and the barrier layer


209


. A supporter


219


can be created in such a layer between a portion of the trench


211


and a portion of the barrier layer


209


. Such a supporter


219


provides additional support to the portion of the barrier layer


209


thereabove and prevents the above barrier layer


209


from sagging into the trench


211


. Consequently, the supporter


209


reinforces the support to the orifice plate


201


provided by the barrier layer


209


.





FIG. 3

illustrates two different types of the supporter


219


. As shown, the supporter


219


, is a portion of the SiC/SiN layer


311


connected to other parts of the SiC/SiN layer, preferably with holes


411


therein.




A second embodiment of the invention is shown in FIG.


2


. An ink conduit


301


is provided in the barrier layer


209


for replenishment of ink from the ink refill channel


215


to the ink-firing chamber


207


. In this embodiment, the maximum distance between two sides of the opening


301


is designed to be substantially narrower than the width of the resistor


205


so as to provide additional support to the above orifice plate


201


and to reduce sag of the orifice plate


201


into the ink conduit


301


. In the preferred embodiment, the maximum distance is not more than two-fifths of the width of the resistor


205


.




In the second embodiment shown in

FIG. 2

, a trench


211


is also provided in the substrate


217


for supplementary replenishment of ink from the ink refill channel


215


to the ink-firing chamber


207


. The trench


211


has an open end


213


to the ink refill channel


215


and terminates at an outlet


221


in the floor of the ink-firing chamber


207


so as to provide an ink flow path between the ink refill channel


215


and the ink-firing chamber


207


. The trench


211


provides an additional ink flow path between the ink refill channel


215


and the ink-firing chamber


207


, and it further enables rapid refill of ink to the ink-firing chamber


207


.




A supporter


219


is also provided in a SiC/SiN layer


311


above a portion of the trench


211


to prevent the barrier layer


209


from sagging into the trench


211


and consequently to reinforce the support to the orifice plate


201


provided by the barrier layer


209


.




With reference to

FIGS. 4A-4G

and


5


A-


5


G, described is a sequence of illustrations of fabricating an ink-firing element having a trench and a supporter in an edge feed construction.

FIGS. 4A-4G

are top plan views, while

FIGS. 5A-5G

are cross section views along line A-A′ which is shown in FIG.


4


A.




As shown in

FIGS. 4A and 5A

, a SiC/SiN layer


311


is first deposited onto an upper surface of the substrate


217


, as well as atop the resistor


205


. Normally, the SiC/SiN layer


311


is to prevent the resistor


205


and the substrate


217


from corrosion. In the preferred embodiment of the invention, such a layer is also to form the supporter


219


for supporting a portion of the barrier layer


209


thereabove.




In

FIGS. 4B and 5B

, a patterned photoresist layer


313


is placed above the SiC/SiN layer


311


. With reference to

FIG. 1

, the photoresist layer


313


has a first blank area


315


adjacent to the resistor


205


for etching a part of the SiC/SiN layer


311


. The first blank area is positioned such that the part of the SiC/SiN layer etched and consequently the outlet of the trench formed thereafter would fall within the ink-firing chamber


207


. Next to the first blank area


315


, a plurality of blank strips which are substantially parallel to each other is provided in the photoresist layer


313


for forming a second part of the trench. The blank strips divides a part of the photoresist layer


313


into a plurality of photoresist strips


319


under which the supporter


219


in the SiC/SiN layer


313


is to be formed. Furthermore, the photoresist strips


319


are positioned at a place where a portion of the barrier layer


207


would be placed. Thereby, the supporter


219


thus formed can provide support to the barrier layer


207


thereabove and prevent the portion of the barrier layer from sagging into the trench. Next to the photoresist strips


319


, a second blank area


317


is provided in the photoresist layer


313


for etching another part of the SiC/SiN layer. The open end


213


of the trench


211


will be formed in this area.




Subsequently, in

FIGS. 4C and 5C

, sulphur hexafluoride (SF


6


) is used to dry etch away unwanted areas of the SiC/SiN layer


311


. After such a dry etch step, the SiC/SiN layer


311


has the same pattern as the photoresist layer


313


. Next, the photoresist layer


313


is removed by using for example oxygen plasma. As shown in

FIGS. 4D and 5D

, the supporter


219


is now formed in the SiC/SiN layer


311


. Note that the supporter


219


is formed by etching away part of the SiC/SiN layer


311


. As part of the remaining SiC/SiN layer


311


, the supporter


219


is connected to other parts of the SiC/SiN layer


311


as shown in FIG.


4


D. Such a connection enables the supporter


219


to provide support to the barrier layer


209


thereabove when the barrier layer is paced atop the SiC/SiN layer


311


.




Then in

FIGS. 4E and 5E

, for a substrate made of silicon, tetra-methyl ammonia hydroxide (TMAH) is used to etch the trench


211


in the substrate


217


right below the SiC/SiN layer


311


. The trench is preferably in a V-shape due to the nature of wet etch on Silicon crystal. This process is generally understood by those with ordinary skill in this field.




Further, in

FIGS. 4F and 5F

, the substrate


217


with the SiC/SiN layer above is sawed to remove part of the substrate


217


as well as part of the SiC/SiN layer


311


. The trench


211


; which terminates at an outlet


221


in the floor of the ink-firing chamber


207


and has an open end


213


to the ink refill channel


215


, is thus formed in the substrate


217


with a supporter


219


in the SiC/SiN layer


311


thereabove.




Having such a substrate with the trench, as shown in

FIGS. 4G and 5G

, the ink-firing element


200


can be formed by sequentially attaching a barrier layer


209


and an orifice plate


201


. The barrier layer


209


can have an ink conduit


301


therein. Alternatively, the barrier layer


209


can be in a closed-loop design. The process of attaching the barrier layer


209


and the orifice plate


201


is generally understood by those with ordinary skill in this field.




Although it is only described herein a process of forming an ink-firing element in an edge feed construction, it is understood that the invention can be applied to form an ink-firing element in other constructions, for example, the center feed construction.




Alternatives can be made to the embodiments described above. For example, a metal layer, such as a tantalum (TA) layer, can be used to provide the supporter. In that case, after the tantalum layer is covered by the photoresist layer


313


, wet etching technology is used to remove unwanted tantalum using, for example, acetic acid. Further, the supporter


219


may not be necessary. In that case, in the process described together with

FIGS. 4A-4F

and


5


A-


5


F, the SiC/SiN layer would not be deposited onto the substrate


217


.



Claims
  • 1. An ink-firing element in a printer cartridge, comprising:a resistor for generating ink droplets; a substrate atop which the resistor rests; a barrier layer atop the substrate, wherein the barrier layer is in a closed-loop design and at least partially defines an ink-firing chamber which surrounds the resistor and temporarily contains ink; an orifice plate supported by the barrier layer for providing an orifice through which the ink droplets are ejected onto a medium; and a trench in the substrate for replenishment of ink, wherein the trench terminates at an outlet in the ink-firing chamber and is in fluid communication with an ink refill channel which supplies ink from a reservoir to the resistor.
  • 2. The ink-firing element of claim 1, further comprising a supporter above the trench for supporting a portion of the barrier layer thereabove.
  • 3. The ink-firing element of claim 1, further comprising a supporting layer above the substrate, wherein the supporting layer includes a supporter above the trench for supporting a portion of the barrier layer thereabove.
  • 4. The ink-firing element of claim 3, wherein the supporting layer is a silicon carbide layer.
  • 5. The ink-firing element of claim 3, wherein the supporting layer is a silicon nitride layer.
  • 6. The ink-firing element of claim 1, wherein the closed-loop structured barrier layer provides sufficient support to the orifice plate thereabove for reducing sag of the orifice plate.
  • 7. An ink-firing element in a printer, comprising:a resistor for generating ink droplets; a substrate atop which the resistor rests; a barrier layer atop the substrate, wherein the barrier layer partially surrounds the resistor and defines an ink-firing chamber; an orifice plate supported by the barrier layer for providing an orifice through which the ink droplets are ejected onto a medium; an ink conduit provided in the barrier layer for supplying ink from an ink refill channel to the ink-firing chamber, wherein the ink refill channel supplies ink from a reservoir to the resistor, and a trench provided in the substrate for supplementary replenishment of ink, wherein the trench is in fluid communication with the ink refill channel and terminates at an outlet in the ink-firing chamber.
  • 8. The ink-firing element of claim 7, further comprising a supporter for supporting a portion of the barrier layer above the trench.
  • 9. The ink-firing element of claim 7, further comprising a supporting layer above the substrate, wherein the supporting layer includes a supporter above the trench for supporting a portion of the barrier layer thereabove.
  • 10. The ink-firing element of claim 7, wherein the maximum distance between two sides of the ink conduit is substantially reduced for preventing sag of the orifice plate.
Priority Claims (1)
Number Date Country Kind
200106654 Oct 2001 SG
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Number Date Country
0177932 Apr 1989 EP
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