Incremental printing of symbolic information – Ink jet – Ejector mechanism
Patent
1994-07-28
2000-07-18
Barlow, Jr., John E.
Incremental printing of symbolic information
Ink jet
Ejector mechanism
2191217, 298901, B41J 214, B41J 216, B41J 2045
Patent
active
060896981
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to methods and apparatus for forming the nozzles of ink jet printheads, particularly drop-on-demand ink jet printheads.
In particular the method involves forming nozzles after the nozzle plates are attached to the printhead into a generally conical shape tapered in the nozzle flow direction. The method employs a high energy beam, suitably, an UV ablating pulsed excimer laser incident on the exit face of the nozzle.
Since the initial proposals for drop-on-demand ink jet printers, as for example, in U.S. Pat. No. 3,946,398 (Kyser & Sears), it has been known to employ nozzles of a generally frusto-conical shape tapering towards the nozzle outlet. The geometry of the nozzles should be accurately made with regard to their location, exit area and direction of core axis in the nozzle plate in order to ensure uniform quality of printing by ink drops ejected from them. A single nozzle plate typically incorporates between 50-5000 nozzles which apply monochrome ink or a number of independent ink colours. Accurate placement of the nozzles in a uniform pattern within and between colourways on the nozzle plate also controls printing quality. The geometrical shape of the cone is further chosen with particular regard to the dynamic acoustic impedances of the ink in the nozzle in the ejection cycle, to minimise the energy of drop ejection and at the same time damp the residual acoustic energy in the channel in preparation for a further operating cycle.
The inlet section of the nozzle is also matched as far as possible to the ink channel section of the actuator behind it in order to prevent entrapment of air bubbles behind the nozzle plate which may disrupt operation of the printer. It is further generally accepted that it is necessary for the ink to wet the nozzle bore but to be non-wetting to the material of the nozzle plate exit face.
Accordingly, it is required to develop methods of nozzle manufacture whereby nozzles are formed with a well defined and precisely reproduced geometric shape and are arranged in defined locations within the nozzle plate with optical accuracy. A further requirement of the methods is that manufacture be continuous and rapid, capable of making several thousand printheads per day at extremely low cost.
In patent application EP-A-0 309 146 it is proposed, inter alia, to form the nozzles in the nozzle plate of an ink jet printhead following attachment of the nozzle plate, by exposing the exit face of the nozzle plate via an apertured mask to generally parallel beams of UV or high energy radiation and at the same time rocking the nozzle plate about axes normal to the radiation direction to form nozzles tapered towards the nozzle exit.
One disadvantage of the rocking method is that only a small fraction of the radiation which is exposed to the mask is usually applied to the nozzle plate for ablation, the greater part being reflected from or absorbed in the mask. Accordingly, the power of the high energy beam used for manufacture is not efficiently employed and production rates are accordingly reduced in the production process as a whole.
A further disadvantage is that the incoming parallel radiation when ablating the internal work face of the nozzle with the beam entering the exit aperture, is exposed to only a fraction of the work area owing to the rocking motion. Accordingly, a greater number of energy pulses, typically by an order of magnitude or more, is required to effect ablation of a nozzle than when ablation is applied uniformly in excess of the threshold ablation energy to the entire work area.
It is an object of the present invention to provide an improved method of and apparatus for forming a nozzle or nozzles in a nozzle plate of an ink jet printer. Another object is to form a novel kind of nozzle.
The present invention consists in one aspect in the method of forming a nozzle in a nozzle plate of an ink jet printer which has an inlet and an outlet in respective opposite faces of said plate and a bore which extends through said plate and tapers in the directi
REFERENCES:
patent: 3946398 (1976-03-01), Kyser et al.
patent: 4379304 (1983-04-01), Heinzl et al.
patent: 5189437 (1993-02-01), Michaelis et al.
patent: 5208604 (1993-05-01), Watanabe et al.
patent: 5208980 (1993-05-01), Hayes
patent: 5237148 (1993-08-01), Aoki et al.
patent: 5389954 (1995-02-01), Inaba et al.
Shepherd Mark
Temple Stephen
Barlow Jr. John E.
Gordon Raquel Yvette
Xaar Technology Limited
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