Thin film pegless permanent orifice plate mandrel

Abstract: A mandrel is used in the manufacture of an ink jet orifice plate. The mandrel comprises a glass substrate (14) and an etched Titanium-Tungsten layer (16) having a thickness of approximately 2000Å to 5000Å residing on the substrate. The mandrel is manufactured by depositing a 2000Å to 5000Å thick layer of Titanium-Tungsten (16) on a substrate, and then depositing a photoresist layer (18) on the Titanium-Tungsten layer in a spin coater. The photoresist layer is cured, and a patterned photomask is positioned on the photoresist layer. The photoresist layer is exposed to actinic radiation and then developed to produce a photomask pattern on the photoresist layer. The next step is to plasma etch the Titanium-Tungsten layer with a Halogen containing gas to form an etched conducting film mold. Finally, the remaining photoresist layer is stripped to complete construction of the mandrel, so the mandrel is reusable without any additional preparation.

Description: Technical Field The present invention relates to the field of electroplating and, more particularly, to the field of manufacturing orifice plate mandrels using thin film processes. Background Art In continuous ink jet printing, electrically conductive ink is supplied under pressure to a manifold region that distributes the ink to a plurality of orifices, typically arranged in a linear array(s). The ink discharges from the orifices in filaments which break into droplet streams. Individual droplet streams are selectively charged in the region of the break off from the filaments and charge drops are deflected from their normal trajectories. The deflected drops may be caught and recirculated, and the undeflected drops allowed to proceed to a print receiving medium. Drops are charged by a charge plate having a plurality of charging electrodes along one edge, and a corresponding plurality of connecting leads along one surface. The edge of the charge plate having the charging electrodes is placed in close proximity to the break off point of the ink jet filaments, and charges applied to the leads to induce charges in the drops as they break off from the filaments. The prior art method for producing orifice plates utilizes a conductive brass mandrel in which photoresist orifice pegs are applied. Metal mandrels are comparatively poor in quality due to surface scratches and defects inherent in metal substrates. Photoresist thickness variation is another degrading factor in this technique which, combined with the low quality brass substrate, produces an inferior orifice plate. Another disadvantage to this method is the hazardous waste generated from etchants, strippers and dissolved metals into waste streams. Furthermore, the non-reusability of this mandrel makes this process extremely expensive. U.S. Pat. No. 3,703,450 describes a method for making a precision conductive mesh screen. First, this method constructs a mandrel. The prior art mandrel is constructed by placing a master plate with the screen pattern on the glass substrate and by vapor depositing a thin film through the interstices of the master plate to form the screen's pattern on the glass. After removing the master plate from the glass substrate, the method deposits photoresist over the entire glass plate. Next, the method exposes and develops the photoresist to produce a layer of thin film in a screen pattern covered with a layer of photoresist in the same screen pattern. Next, the method deposits silicon monoxide on the entire glass substrate and removes the silicon monoxide and photoresist from the thin film pattern. This nonreusable mandrel is now ready for manufacturing the screen. This prior art mandrel has several disadvantages. It cannot manufacture small geometry devices as pointed out in U.S. Pat. No. 4,549,939 discussed below. Also, the complicated prior art process for making this mandrel has low yields. U.S. Pat. No. 4,549,939 describes another prior art thin film mandrel and the method of making it. This prior art process constructs the prior art mandrel by forming a stained pattern shield on a glass substrate and depositing a conductive and transparent thin film onto the substrate. Next, the prior art method coats the thin film with resist and shines a light through the glass substrate and the transparent thin film to expose the unshielded photoresist. Finally, the photoresist is developed and forms the mold for electroforming. The prior art mandrel formed by this process has several disadvantages. It is non-reusable and of poor quality due to resist broken after the use of a conductive thin film that is transparent; a costly and exotic material. U.S. Pat. No. 4,528,577 describes another prior art mandrel and the method of making it. This prior art method of manufacturing orifice plates for thermal ink jet printheads electroforms nickel onto a stainless steel mandrel plate that contains either a re-etched orifice pattern or a photoresist orifice pattern. Unfortunately, stainless steel mandrel plates always contain a large number of scratches and defects. These scratches and defects arise from characteristics of the stainless steel material and from the manufacturing process. The scratches and defects, which can not be eliminated, degrade the quality of the orifice plates manufactured from stainless steel mandrels. These inferior orifice plates produce inferior print quality. The method and apparatus in accordance with the present invention obviate these problems with mandrels in the prior art. In the electroplating process, as in U.S. Patent No. 4,773,971, the orifices are formed by overplating the voids within the conductive film and onto the underlying smooth glass substrate. Other methods of orifice plate manufacturing processes rely on overplating a photoresist peg that is prone to defects and pinholes, and is dimensionally unstable. It is seen then that there is a need for an improved mandrel for use in the manufacture of ink jet orifice plates. Summary of the Invention This need is met by the improved method of manufacturing ink jet orifice plates using a pegless thin film reusable mandrel. In accordance with one aspect of the present invention, there is provided a mandrel for an ink jet orifice plate, the mandrel comprising: a substrate; and an etched Titanium-Tungsten layer on said substrate. The substrate is preferably of glass. The etched Titanium-Tungsten layer preferably has a thickness of approximately 2000A to 5000A. In accordance with another aspect of the present invention, there is provided a method of making a mandrel for an ink jet orifice plate, the method comprising the steps of: providing a substrate; depositing a layer of Titanium-Tungsten on said substrate; depositing a photoresist layer on the Titanium-Tungsten layer; curing said photoresist layer; positioning a photomask having a pattern on the photoresist layer; exposing the photoresist layer to actinic radiation; developing the photoresist layer to produce a photomask pattern on the photoresist layer; plasma etching the Titanium-Tungsten layer with a Halogen containing gas to form an etched conducting film mold; and stripping the remaining photoresist layer to complete construction of said mandrel. The present invention allows the manufacture orifice plates using a thin film pegless mandrel. Embodiments of this invention will now be described with reference to the accompanying drawings. Brief Description of the Drawings Fig. 1A is a top view of a plasma etched thin film permanent mandrel with the orifice patterned, in accordance with the present invention; Fig. 1B is a side view of the plasma etched thin film permanent mandrel, in accordance with one embodiment of the present invention; Fig. 1C is a top view of a nickel plated thin film permanent mandrel, in accordance with another embodiment of the present invention; Figs. 2A-2H show the steps used to manufacture the thin film pegless orifice plate mandrel of the present invention. Detailed Description of the Preferred Embodiments The manufacturing of high quality precision orifice plates is highly desirable for ink-jet printheads. One method to accomplish this is by using a thin film pegless (void in the conductive layer) reusable mandrel. The mandrel is manufactured by sputtering, or sputter etching, or reactive ion etching a conductive thin film metal Titanium/Tungsten onto a smooth substrate such as glass. Next, a standard photolithographic process is used to define an appropriate orifice plate pattern in the photoresist. The unprotected thin film Titanium/Tungsten within the photoresist pattern is removed by a plasma etching process. The photoresist is then removed from the conductive thin film and the mandrel can be electroplated to produce orifice plates. This method produces a pegless thin film mandrel that can be manufactured using standard photolithographic and plasma etching techniques that yield a high resolution mandrel in which orifice plates can be produced. The electroformed orifice plates can be reproduced and have the identical high resolution characteristics of the pegless thin film mandrel taking advantage of the dimensional stability. In the electroplating process, the orifices are formed by overplating the voids within the conductive film and onto the underlying smooth glass substrate. Other methods of orifice plate manufacturing processes rely on overplating a photoresist peg that is prone to defects, pinholes and dimensionally unstable. The pegless mandrel exposes the defect free glass substrate that is not compromised by previous manufacturing processes. The mandrel of the present embodiment is unique because of the use of Titanium-Tungsten as the conductive layer, and also because the mandrel can be plasma etched to define the conductive film mold. Plasma etching allows for the voids in the conductive layer to be of high resolution. Referring now to the drawings, Fig. 1A is a top view of a plasma etched thin film permanent mandrel 10 with a patterned orifice 12. Fig. 1B illustrates a side view of the plasma etched thin film permanent mandrel 10. Fig. 1C is a top view of a nickel plated thin film permanent mandrel 10', with a patterned orifice 12'. The process for manufacturing the thin film pegless orifice plate mandrel 10 or 10' of the present invention is best illustrated in Figs. 2A-2H. The process starts with a glass substrate or silicon wafer, or a polished silicon wafer, or a plastic, or any smooth, nonconducting surface 14, as shown in Fig. 2A. As shown in Fig. 2B, a conductive thin film metal 16 is deposited on the glass substrate 14 by a suitable process such as a sputter etching process or reactive ion etching process. The thin film is constructed from a Titanium/Tungsten material. Next, as illustrated in Fig. 2C, a photoresist layer 18 is applied atop the Titanium/ Tungsten layer. The photoresist layer 18 is then exposed to actinic radiation and developed to produce the orifice pattern. In Fig. 2E, the Titanium-Tungsten layer is plasma etched to define the orifice mold. In Fig. 2F, the photoresist layer 18 is removed, allowing the thin film permanent mandrel to be nickel plated, with nickel plating layer 20, as shown in Fig. 2G. finally, as illustrated in Fig. 2H, the nickel orifice plate 20 is removed from the thin film permanent mandrel, allowing the mandrel to be reused, with no additional preparation. Continuing with Figs. 1A-1C and 2A-2H, the mandrel comprises a glass substrate 14 with an etched Titanium-Tungsten layer 16 residing on the substrate. The Titanium-Tungsten layer 16 typically has a thickness of approximately 2000Å to 5000Å. The mandrel is manufactured by sputter depositing the 2000Å to 5000Å thick layer 16 of Titanium-Tungsten on the substrate 14, and then depositing a photoresist layer 18 on the Titanium-Tungsten layer 16, using a spin coating process. The photoresist layer 18 is cured, and a patterned photomask is positioned on the photoresist layer. The photoresist layer is exposed to actinic radiation and then developed to produce a photomask pattern on the photoresist layer 18. The next step is to plasma etch the Titanium-Tungsten layer 16, with a Halogen containing gas, to form an etched conducting film mold. Finally, the remaining photoresist layer is stripped to complete construction of the mandrel. Industrial Applicability and Advantages The present invention is useful in the field of ink jet printing, and has the advantage of providing an improved mandrel. The present invention provides the further advantage of providing a reusable thin film pegless permanent orifice plate mandrel. The advantage of providing a reusable thin film pegless permanent orifice plate mandrel is that from a single mandrel numerous orifice plates can be produced. This has the further advantage of reducing the cost of fabricating orifice plates compared to conventional methods such as metal mandrels with photoresist pegs that are limited to producing a single orifice plate. Having described the invention in detail and by reference to the preferred embodiment thereof, it will be apparent that other modifications and variations are possible without departing from the scope of the invention defined in the appended claims.

Claims: A mandrel for an ink jet orifice plate, the mandrel comprising: a substrate (14); and an etched Titanium-Tungsten layer (16) on said substrate (14). A mandrel as claimed in claim 1 wherein the substrate (14) is of glass. A mandrel as claimed in claim 1 wherein said etched Titanium-Tungsten layer (16) has a thickness of approximately 2000Å to 5000Å. A mandrel as claimed in claim 1 wherein the mandrel is reusable. A method of making a mandrel for an ink jet orifice plate, the method comprising the steps of: providing a substrate (14); depositing a layer (16) of Titanium-Tungsten on said substrate; depositing a photoresist layer on the Titanium-Tungsten layer; curing said photoresist layer (18); positioning a photomask having a pattern on the photoresist layer; exposing the photoresist layer (18) to actinic radiation; developing the photoresist layer (18) to produce a photomask pattern on the photoresist layer (18); plasma etching the Titanium-Tungsten layer (16) with a Halogen containing gas to form an etched conducting film mold; and stripping the remaining photoresist layer to complete construction of said mandrel (20). A method of making a mandrel as claimed in claim 5 wherein the step of depositing a layer (16) of Titanium-Tungsten on said substrate (14) uses a sputter etching process. A method of making a mandrel as claimed in claim 5 wherein the step of depositing a photoresist layer (18) on the Titanium-Tungsten layer uses a spin coating process. A method of making a mandrel as claimed in claim 5 wherein the mandrel is reusable.

Inventors: WOLFF JOHN W, WOLFF, JOHN W.
Applicants: SCITEX DIGITAL PRINTING INC, SCITEX DIGITAL PRINTING, INC.
Application year: 1995
Main classification: C25D1
IPC codes: B41J2, C25D1