Incremental printing of symbolic information – Ink jet – Ejector mechanism
Reexamination Certificate
1992-10-29
2001-03-20
Barlow, John (Department: 2853)
Incremental printing of symbolic information
Ink jet
Ejector mechanism
C347S061000
Reexamination Certificate
active
06203142
ABSTRACT:
FIELD OF THE INVENTION AND RELATED ART
The present invention relates to an ink jet recording method and apparatus and a recording head therefor in which liquid droplets are ejected using thermal energy onto a sheet of paper, resin sheet or cloth or another recording material.
In an ink jet recording method, the recording medium (ink) which is in the form of a liquid material or a heat-soluble solid material is deposited on the recording material using thermal energy. The recording method allows high speed recording (and provides relatively high record quality and the low noise). In addition, the method is relatively easily applicable to color image recording on a plain sheet of paper or cloth or the like. A further advantage is that the size of the apparatus is small.
The ink jet recording apparatus using this method comprises a recording head which has ejection outlets for ejecting the ink in the form of droplets, ink passages communicating with the ejection outlets and energy generating means for applying ejection energy to the ink in the liquid passage. U.S. Pat. No. 4,723,129 discloses a method in which the energy generating means is in the form of an electrothermal transducer, and the thermal energy produced by the electric pulse application is applied to the ink so as to eject the ink.
In the recording methods disclosed in the above U.S. patent, the ink, having absorbed the thermal energy, is subjected to a state change which causes a quick volume change by film boiling of the liquid. By the development and contraction of the bubble, the ink is ejected through the ejection outlet at an end of the recording head. The ejected droplets of the ink are deposited on the recording medium to form an image. According to this recording method, the ejection outlets may be arranged with high density in a recording head, and therefore, high speed, high resolution and high quality image can be recorded. The recording apparatuses using this method can be used as copying machines, printers, facsimile machines and other information outputting means.
Japanese Laid-Open Patent Application No. 161935/1979 discloses that ink in an ink chamber is turned to gas by a cylindrical heat generating element, and the gas is ejected through an ink ejection outlet together with ink droplets. According to this method, the gas and fine droplets are splashed with the result of low quality image. In addition, the ink is further gasified by the splash with the result of production of mist of the ink, which further contaminates the background of the record or the inside of the recording apparatus.
Japanese Laid-Open Patent Application No. 197246/1986 discloses a modified ink jet recording method or thermal transfer recording method, in which a single ink ejection is effected. Since it is difficult to completely contact the heat generating element to the recording material, the thermal efficiency tends to decrease as compared with the ink jet recording method using the recording head having the conventional ejection outlets. Therefore, it is not suitable for high speed recording.
On the other hand, U.S. Pat. No. 4,638,337 discloses as prior art, in which a bubble communicates with the ambient air. However, the communication between the bubble and the ambience occurs adjacent to the heat generating element, not adjacent to the ejection outlet. For this reason, it easily introduces the air into the neighborhood of the heat generating element with the result of unstable ink ejection, as properly described in the U.S. Patent.
In order to solve the above problems of the ink jet recording system, U.S. Ser. No. 692,935 has proposed that the bubble produced by the film boiling is caused to communicate with the ambience adjacent to the ejection outlet (communication ejection system).
With this communication ejection system, the gas constituting the bubble does not eject with the ink droplet so that the production of the splash or mist is reduced, and therefore, the contamination of the recording material and inside the apparatus can be prevented.
As a fundamental of the communication ejection system, the ink downstream of the bubble formation position is all ejected out in principle. Therefore, the amount of ejected ink can be determined on the basis of the structure of the recording head such as a distance from the ejection outlet to the bubble formation position. As a result, in the communication ejection system, the ejection amount can be stabilized without against influence of the ink temperature or the like.
Although the communication of the bubble to the ambience is improved to provide stabilized ink ejection, the detailed investigations have revealed that the communicating action varies slightly. The cause may include some unstable factor in the relative relations among the created bubble from the heat generating resistor ruling the development of the bubble, movement of the ink adjacent the ejection outlet, ejection of the ink through the ejection outlet and the communication between the ambience and the bubble.
In usual recording heads in which the thermal energy is instantaneously applied to a small area to produce film boiling, the size of the heat generating resistor is not more than 30,000 &mgr;m
2
at the maximum, and usually it is less than 5000 &mgr;m
2
. In the communication ejection system, the liquid between the heat generating resistor to the ejection outlet is all ejected with substantial certainty. For this reason, the practical size of the heat generating resistor is not more than 3000 &mgr;m
2
. The inventors have particularly noted the area of the heat generating resistor in the communication ejection system.
SUMMARY OF THE INVENTION
Accordingly, it is a principal object of the present invention to provide an ink jet recording method and apparatus and a recording head therefor in which the ink droplet formation is further stabilized, and further improved images can be formed with improved overall efficiency, in the communication ejection system in which the bubble created communicates with the ambience at the time of droplet ejection.
According to an aspect of the present invention, there is provided a liquid jet recording method using thermal energy to eject liquid from a liquid passage through an ejection outlet, said liquid passage being provided with a heat generating resistor, wherein the following conditions are satisfied:
S1≧S2/3, and
S2≧S3/3
where S1 is an area of the heat generating resistor, and S2 is a projected area, onto a surface having the heat generating resistor, of the liquid passage between the ejection outlet and the heat generating resistor; wherein a bubble created by the heat generating resistor communicates with ambience when the liquid is ejected.
According to another aspect of the present invention, there is provided a recording apparatus comprising: a liquid ejection outlet; a liquid passage in communication with the ejection outlet; a electrothermal transducer having a heat generating resistor for supplying thermal energy to the liquid in the passage to eject the ink through the ejection outlet by creation of the bubble in the liquid in the liquid passage; signal supplying means for supplying electric signals to the resistor; wherein the following conditions are satisfied:
S1≧S2/3, and
S2≧S3/3
where S1 is an area of the heat generating resistor, and S2 is a projected area, onto a surface having the heat generating resistor, of the liquid passage between the ejection outlet and the heat generating resistor; wherein a bubble created by the heat generating resistor communicates with ambience when the liquid is ejected.
According to a further aspect of the present invention, there is provided a recording head comprising: a liquid ejection outlet; a liquid passage in communication with the ejection outlet; an electrothermal transducer having a heat generating resistor for supplying thermal energy to the liquid in the passage to eject the ink through the ejection outlet by creation of the bubble in the liquid in the liquid passage; wherein the following condi
Inui Toshiharu
Nakajima Kazuhiro
Barlow John
Canon Kabushiki Kaisha
Fitzpatrick ,Cella, Harper & Scinto
Hallacher Craig A.
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