JPS62134268A - Thermal ink jet printing head - Google Patents

Abstract

PURPOSE:To perform high-quality printing by uniformizing ink inflow pressure and to enhance the mounting density of orifices and an ink sump, by supplying ink to a heater resistor by an elongated groove. CONSTITUTION:A membrane resistor substrate 10 is mounted on the I-shaped upper surface of a header manifold 20. The header manifold 2 has an ink sump communicated with an ink feed hole 22 mounted therein and the hole 22 is matched with the elongated groove 16 in the membrane resistor substrate 10. A nickel orifice plate 44 is arranged on a silicon carbide layer 42 and has ink sump areas 46, 48, which are positioned on heater resistors 36, 38, to receive ink through the elongated groove 16. These ink sump areas 46, 48 extend to the upper part of the substrate 10 and are connected to an outlet ink discharge orifice demarcated by converging contour walls 50, 52. These contour walls 50, 52 are planned so as to reduce cavitation abrasion during ink jet printing operation and to prevent gulping.

Description

TECHNICAL FIELD OF THE INVENTION This invention relates generally to thermal inkjet printing, and more particularly to a new and improved thermal inkjet printhead.

[Prior art and its problems]

Thermal inkjet printing is described in many technical publications, one such publication that is relevant to the present invention is the Hewlett Packard Journal.
l, V□fume 36, Number 5, May1
It is 985.

It is known in the art of thermal inkjet printing to include a plurality of electrically resistive elements on a common thin film substrate for the purpose of heating a plurality of corresponding adjacent ink reservoirs during the ink ejection printing process. With this structure, adjacent ink reservoirs are typically provided as cavities in the barrier layer on the substrate in order to properly concentrate the thermal energy emanating from the resistive elements into a predetermined amount of ink. A plurality of ink evacuation orifices are also provided on these cavities to provide an exit path for the ink during the printing process.

One method in manufacturing printhead assemblies of the type described above has been to drill vertical holes in the common substrate to provide ink flow paths from the common reservoir to the individual reservoir cavities in the barrier layer. However, creating multiple holes (vertical cylindrical channels) in a single substrate is associated with various drawbacks. One of these drawbacks is that the cutting edges used to drill the holes in the substrate can exert considerable pressure on the substrate material, causing it to fracture. On the other hand, when laser drilling is used, it leaves channels with destroyed sidewalls as a result of laser beam heating, weakening the substrate structure.

Additionally, forming multiple vertical channels in the silicon substrate itself weakens the printhead structure. In some types of conventional printhead constructions, these channels are used to provide ink flow to multiple resistive heater elements located at different distances therefrom. In such a structure, these different ink flow distances result in different pressure drops in the ink flow path. That is, the pressure drop along the liquid ink flow path is proportional to the cube of the distance of the flow path. This resulted in large pressure drops over long ink flow path distances, often preventing proper vaporization when inkjet propulsion from an inkjet orifice.

Another disadvantage of using small diameter vertical channels to supply ink to the ink reservoir is that they cannot adequately respond to the required ink volume demands at increasingly higher required operating frequencies.

Yet another disadvantage of using multiple ink flow channels on a common substrate is that they require special running of conductive leads over the substrate surface.

This requirement, in addition to the increased cost associated with this special routing, reduces packaging density due to the required surface area to accommodate this special routing.

[Purpose of the invention]

The purpose is to supply a heater resistor and eliminate the above-mentioned drawbacks.

[Summary of the invention]

A general object of the present invention is to provide a new and improved thermal inkjet printhead assembly that eliminates the problems described above by using through holes in a common printhead substrate member. be. In this new assembly, a single slot is cut into the substrate to provide ink flow to a plurality of ink reservoirs coupled with resistive heater elements formed on the top surface of the substrate. These heaters are arranged along the periphery of the groove and at a predetermined distance therefrom. Conductive leads are provided on the substrate between each resistive heater element and external electrical connections. The barrier layer and Oriswiss plate member cover all of the resistive heater elements and define a respective reservoir on top of each resistive heater element.

The grooved geometry greatly increases the packaging density of heater resistors on a common printhead substrate. The increased packing density is due to the fact that in traditional multi-hole printhead structures, conductive traces for individual resistive elements must be placed around the holes, thereby increasing the required board area. This is partly due to the facts. Thus, by using the elongated groove structure of the present invention in place of the 8U vertical hole in the conventional structure, 8:
Packaging density increases of 1 to 10:1 can be achieved.

After the orifice plate and its associated barrier layer member are secured onto the thin film substrate, the substrate is die bonded to the Helada manifold member. The manifold member has slots therein for passing ink from the wells of the header manifold, through the substrate holes, and into individual reservoirs of the barrier layer and orifice plate member.

A novel feature of the present invention provides control of the pressure of ink flow simultaneously from a common ink supply source, through a single hole in a thin film resistor structure, and through a common ink flow path to multiple ink reservoirs in a printhead assembly. There are also areas for improvement.

[Embodiments of the invention]

FIG. 2 shows a thin film resistive substrate 10 for a thermal inkjet printer with a metal orifice plate 12 thereon. The orifice plate 12 is usually made of nickel and has ink feed holes (elongated grooves) 1 indicated by dotted lines in FIG.
It has a plurality of ink discharge holes (nozzles) 14 evenly scattered around the end portion of 6.

FIG. 1 will be explained. First, the thin film resistive substrate 10 is mounted on the top-shaped surface of the Helada manifold 20. The header manifold 20 includes an ink reservoir (not shown) communicating with the ink feed hole 22 therein. Hole 22 aligns with slot 16 in thin film resistor substrate 10 . The header manifold 20 further includes a contour wall 24 that, when fully assembled, has a first
It is shaped to match a corresponding contoured wall of an inkjet printer cartridge assembly (not shown) to receive the illustrated printhead.

After this printhead structure is completed and all the parts shown in FIG. A circuit 26 is electrically connected to the top surface of the thin film resistive substrate 10 by conductive traces. A plurality of thin film conductive leads 28 are placed over the contoured walls 24 of the Helada manifold 20. The internal leads 30 of the TAI3 circuit 26 are thermocompressed to conductive traces on the thin film resistive substrate 10 by the method disclosed in US Application No. 801,034 by Gray E. Hanson. Additionally, orifice plate 12 is aligned with thin film resistive substrate 10 by the orifice plate and barrier layer manufacturing method disclosed in US Pat. No. 8,011,69 by Chanetal.

FIG. 3A and FIG. 3B will be explained. Thin film resistive substrate 10 typically includes a silicon substrate 32 on which a thin film 34 of silicon dioxide is deposited to passivate and insulate its surface. A plurality of heater resistors 36, 38 are formed on the top surface of the silicon dioxide (Sin2) layer 34 and are typically made of tantalum aluminum or tantalum pentoxide and are fabricated by well known photolithography mask etching techniques. Aluminum conductor 40 makes electrical contact with heater resistor 36, 38 and applies electrical pulses thereto during inkjet printing operations.

These conductors may also include aluminum conductors 4 previously deposited on top of the silicon layer 34 using conventional metal deposition techniques.
Formed from 0.

After the aluminum conductor 40 is formed, a surface barrier layer (hereinafter referred to as the silicon carbide layer) 42, typically made of silicon carbide or silicon nitride, is applied to the top surface of the conductor 40 and the heater resistor 36.3.
8 to protect these components from cavitation wear and ink corrosion (without a surface barrier layer, ink corrosion would be caused by the highly corrosive ink in the ink reservoir directly above these heater resistors). ). The silicon carbide layer 42, as well as the previously described 5iOz layer 34, resistor 36, 38 and aluminum conductor 40, are formed using semiconductor processing methods well known to those skilled in the art of thermal inkjet semiconductor processing.

Therefore, it will not be explained in detail here. Further details of this semiconductor processing step can be found in the above-mentioned document, Hewlett
tPackard Journal, Volume
36°Number 5. See May 1985.

The nickel orifice plate 44 has a silicon carbide layer 4 as shown.
2 and has an ink reservoir region 46.48 located directly above the heater resistor 36.38 for receiving ink via the horizontal groove 16. These reservoirs 46,48 extend above the substrate 10 as shown and connect to exit ink discharge orifices defined by converging profile walls 50,52. These contour walls 50.52
No. 80, Chan et al.
1169, designed to reduce cavitation wear and prevent gulping during inkjet printing operations.

During an inkjet printing operation, the ink is
4 and laterally along path 56, the ink flow bow) 58.60.62.64.6
6 and 68 (see left side of the structure in Figures 3A and 3B). Similarly, ink flows through the ink flow port doors 0.72.74.76. on the right side of the structure of FIG. 3B.
Enters 78 and 80K. By flowing ink into the plurality of ink flow ports from a common ink reservoir, the pressure drop of the ink from the ink feed holes 16 to the individual heater resistors, such as 36, 38, is equal, thereby improving inkjet printing. Proper ink bubble evaporation and ejection during operation is ensured. The advantages of this feature of the invention over the prior art have been discussed above.

〔Effect of the invention〕

As is clear from the embodiment of the present invention detailed above, by implementing the present invention, the ink inflow pressure to the ink discharge orifice is made uniform. Moreover, the mounting density of orifices and ink reservoirs is increased, allowing for high-quality printing. Furthermore, since the distance between the common ink reservoir and the orifice can be shortened, high-speed printing is also possible, which is useful in practical use.

[Brief explanation of drawings]

FIG. 1 is an exploded view of a complete thermal inkjet printhead in one embodiment of the invention. FIG. 2 is an isothorax of a perforated resistor die (substrate) used in one embodiment of the present invention. FIG. 3 is a partially enlarged plan view and a sectional view. 10: Thin film resistance board; 12.44 Niorifice plate; 14
: Ink discharge hole; 16: Elongated groove; 18: Top surface of header 20; 20: Header manifold; 22: Ink feed hole;
24: Contour wall; 26: TAB circuit; 28: Thin film conductive lead; 3o: Internal lead; 32: Silicon substrate; 34:
Silicon dioxide layer, 36.38: heater resistance; 4o aluminum conductor; 42: silicon carbide layer; 46.48: ink reservoir area; 50.52: convergent contour wall; 54.56:
Ink flow; 58.60, 62.64.66.68.70
．． 72.74.76.78.80: Iryu boat. Applicant Yokotsutsu Healet Butted Co., Ltd. Agent
Patent Attorney Tsuguo Hasegawa IG 1

Claims (1)

[Scope of Claims] A thermal inkjet printhead having the following (a) to (c). (b) A substrate mounted on a header having an ink feed hole and a common ink reservoir and receiving ink from the common ink reservoir by a slot aligned with the ink feed hole. (b) A plurality of resistive heater elements connected to each of the plurality of corresponding conductors on the upper part of the substrate and arranged around the elongated groove. (c) A barrier layer on the conductor and an orifice plate on the barrier layer having an inkjet ink reservoir disposed at a predetermined ink flow path distance from the elongated groove at a position aligned with the heater element.