Incremental printing of symbolic information – Ink jet – Ejector mechanism
Patent
1993-01-21
1998-06-02
Fuller, Benjamin R.
Incremental printing of symbolic information
Ink jet
Ejector mechanism
347 57, 347 61, B41J 205
Patent
active
057608040
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention is directed to an ink print head for a liquid-jet printing device working on the heat converter principle as well as to a process for its manufacture.
2. Description of the Related Art
The lines to be printed (e.g. characters or graphic patterns) are produced by a plurality of ink drops; the patterns for each character are fixed in a so-called matrix.
In an advantageous manner, a full column of such a matrix is printed simultaneously so as to fulfil the requirements for high printing speed and uniform type face.
An ink print head suitable for the aforementioned printing process must thus combine a plurality of (identical) elements capable of shooting out ink drops at desired time intervals ("drop-on-demand" principle). A characteristic feature of this technology consists in that an electric resistor constructed as a heating element is located in a capillary filled with printing liquid, e.g. ink, specifically in the vicinity of its opening. When a determined heat energy is supplied to this heating element on demand by means of a current pulse, a rapidly expanding ink steam bubble is first produced by means of an extremely fast transfer of heat to the ink liquid (film boiling), which bubble bursts relatively quickly when the ink liquid cools after the supply of energy is cut off. The pressure wave formed by the steam bubble in the interior of the capillary allows an ink jet of limited mass to exit from the outlet opening onto the surface of a printing medium in proximity to it.
An advantage of this bubble-jet principle consists in that the relatively large and rapid change in volume necessary for shooting out the ink is obtained from a very small active converter surface (typically 0.01 mm.sup.2) by utilizing the alternating liquid-gaseous-liquid phases of the ink liquid. The small converter surfaces in turn allow a relatively simple and inexpensive construction of ink print heads characterized by high printing track density and small dimensions with the use of modern production methods such as high-precision photolithography processes in film technology.
A basic configuration for a device working on the bubble-jet principle is described in DE 32 28 887 A1. In the known arrangement, also known as an "edge shooter", the heating surfaces, electric lines and contacts are likewise combined on a chip. The conduit structure can also be advantageously arranged as a photoresist structure. The outlet openings are first achieved by covering the conduit structure with a cover sheet which must be individually subjected to a mechanical high-precision processing along with the substrate and the conduit structure in every chip so as to achieve the necessary surface quality and edge sharpness at the outlet opening. Only after this processing can the outlet surface be coated with a surface film which can be heavily wetted. The magnitude of the drops may be varied only to a limited degree by varying the structure pulses to a heating element.
In accordance with the present invention, the ink print head has a plurality of outlet openings each of which is associated with at least one individually controllable electrothermal element. During printing operation, the converter elements locally heat an ink liquid, and ink liquid is shot out of the outlet openings by means of an ink steam bubble formed by the heat produced by the converter element. A supply vessel for storing ink liquid is mounted in flow connection with the outlet openings through supply lines. The converter elements are heating elements which are arranged so as to be laterally offset relative to the outlet openings in the shooting direction of the ink drops, so that the spreading direction of the ink steam bubble is directed opposite to the ink shooting direction.
The process according to the present invention provides that electric lines for the converter elements and their contacts, as well as the outlet openings, are produced in the same chip on a substrate by means of planar processing steps. T
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Heinzl Joachim
Hochwind Bernhard
Potzlberger Hans W.
Schlaak Helmut
Steckenborn Arno
Eastman Kodak Company
Fuller Benjamin R.
Hallacher Craig A.
Pontani Thomas C.
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