Incremental printing of symbolic information – Ink jet – Ejector mechanism
Reexamination Certificate
1999-12-17
2003-01-28
Hilten, John S. (Department: 2861)
Incremental printing of symbolic information
Ink jet
Ejector mechanism
Reexamination Certificate
active
06511156
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a recording device of the ink-jet type and, particularly, to a nozzle plate for an ink-jet head used for an ink-jet printer, to a method of producing the same and to an ink-jet head using the same. In the ink-jet head of the present invention, a particular ink-repelling layer is formed on the ink blow-out surface of the nozzle plate. Therefore, no ink remains at the ends of the nozzles even after repetitive use, and the ink droplets are permitted to stably fly straight to maintain high printing quality over extended periods of time.
BACKGROUND ART
As is well known, an ink-jet printer records characters, figures, patterns and the like on the surface of paper, a film or any other medium by injecting an ink (aqueous ink or nonaqueous ink) through fine nozzles attached to the ends of an ink-jet head, so that the ink droplets fly toward the surface thereof. An aqueous ink is usually used. There can be employed various recording methods depending on the method of forming ink droplets, the method of producing injection energy, etc. For example, the electric charge-controlled recording method uses a piezoelectric element; i.e., a pressure wave is produced in the ink chamber of the head in which the ink is filled by utilizing vibration of the element, thereby to eject the ink by the pressure wave. There have further been known such methods as an electromechanical conversion method, an electro-thermal conversion method, an electrostatic suction method and a discharge method. The ink-jet printer has many merits as indicated by, for example, the facts that (1) printing is accomplished in a non-contacting manner, (2) printing can be effected onto a variety kinds of media, (3) a plain paper can be used to lower the running cost, (4) color printing can be easily accomplished, (5) colors can be vividly reproduced, (6) less noise is produced during the printing, (7) printing can be executed at high speed, etc.
In the ink-jet printer, as will be described later in detail, fine nozzles (usually called “nozzles for blowing out ink” or “ink blow-out nozzles”) for blowing out the ink have a structure of being formed in a plural number in a nozzle plate, and may be arranged in a single row or in a plurality of rows. The nozzle plate is usually made of a metal material such as a stainless steel or nickel, or a plastic material or ceramic material, and has a thickness of about 0.1 mm, the diameter of the nozzles for blowing out the ink being, generally, from about 30 to about 60 &mgr;m.
In order for the ink droplets to be stably blown out straight, in general, the ink must not stay adhered on the nozzle plate near the ink blow-out nozzles and, besides, stability must be improved, in these portions, for the ink. This is because the adhesion of the ink (so-called “ink droplet pool”) near the ends of the nozzles, grows as the ink oozes out, or the residue of the ink droplets that have flown builds up. Adhesion of the residual ink disturbs the direction in which the ink droplets fly and causes a change in the flying speed, too.
In order to accomplish this object according to the prior art, it has been proposed to form a liquid-repellent or ink-repellent film on the ink blow-out surface of the nozzle plate. As materials that exhibit ink-repelling property, furthermore, there has been known a silicone resin and other fluorine-contained resins. These fluorine-contained resins have a small surface energy and, hence, exhibit excellent resistance against solvents and are hardly wetted by the solutions. The resin of this kind, as a surface-treating agent for the nozzle plate, it can be expected to form a film having an intense ink-repelling property.
According to a prior art for forming a fluorine-contained resin film, a fluorine-contained resin dispersed in a solution is applied by some method onto a substrate and the solvent is vaporized, so that the film of the fluorine-contained resin is melt-formed. In this case, the fluorine-contained resin can be applied by the transfer method, dip-coating method, spin-coating method, roll-coating method, brush-coating method or spray-coating method. Japanese Unexamined Patent Publication (Kokai) No. 2-55140 discloses another method of forming a film of a fluorine-contained resin by relying on the deposition by heat of the fluorine-contained resin.
When the ink-repellent film is to be formed according to the conventional method, long-lasting reliability of the film is important and, particularly, it is important to avoid the deterioration in the ink-repelling property caused by polishing. This is because, the nozzle surfaces are wiped to remove the ink adhered on the nozzle surfaces. However, the ink-repelling property on the nozzle surfaces is deteriorated by the wear resulting from the wiping operation. To avoid deterioration in the ink-repelling property, there can be applied a fluorine-contained resin-containing composite plated film that contains the fluorine-contained resin not only on the surface of the film but also inside the film. The fluorine-contained resin-containing composite plated film is usually formed by depositing a fluorine-contained resin on a substrate by the composite plating that contains the fluorine-contained resin, and by forming the fluorine-contained resin by the heat-treatment. According to this method, the fluorine-contained resin particles are adhered onto the substrate and are then bonded by the heat-treatment. Therefore, a strong film having excellent ink-repelling property is formed compared with only being heat-treated.
Here, a problem arises in that the lower limit in the density of the fluorine-contained resin, distributed on the surface of the fluorine-contained resin-containing composite plated film, varies depending upon the property of the ink that is used. Depending upon the ink, therefore, the distribution of the fluorine-contained resin becomes very dense in the composite plated film. In order to blow out the ink droplets from the nozzles stably and straight, therefore, it becomes necessary to control the density in the distribution of the fluorine-contained resin depending on the ink in the nozzle plate of the ink-jet head.
In the case of the fluorine-contained resin-containing composite plated film, it becomes necessary to adhere the fluorine-contained resin of a predetermined amount onto the surface of the film in order to develop the ink-repelling property on the nozzle surfaces. According to the conventional method, however, the fluorine-contained resin is not adhered in a uniform amount onto the nozzle surfaces, and the ink-repelling property lacks stability from the start.
The ink-repelling property lacks stability from the start on the nozzle surfaces due to the fact that the fluorine-contained resin is adhered in varying amounts onto the nozzle surfaces and, particularly, onto the peripheries of the nozzles. The ink-repelling property on the peripheries of the nozzles is measured as a resistance against the positive pressure. When excellent ink-repelling property is exhibited at the start on the peripheries of the nozzles, the resistance against the positive pressure, which is larger than a predetermined value, is measured. To maintain the ink-repelling property over an extended period of time on the nozzle surfaces, the fluorine-contained resin must be intimately adhered onto the substrate of the nozzle plate on the peripheries of the nozzles and on the nozzle surfaces.
A representative example of the fluorine-contained resin-containing composite plated film will be a fluorine-contained resin-containing nickel composite plating. The fluorine-contained resin-containing nickel composite plating is the one containing, as a matrix, nickel or a nickel alloy that contains fine fluorine-contained resin particles as represented by a polytetrafluoroethylene having a particle diameter of from 0.01 to 100 &mgr;m, which has been widely known as plating technology capable of imparting a lubricating property and a releasing property in addition to a water-repelling property.
In form
Kazama Ayako
Mizuma Isao
Yamada Yorinobu
Yoshino Nobuyuki
Citizen Watch Co. Ltd.
Feggins K.
Hilten John S.
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