Incremental printing of symbolic information – Ink jet – Ejector mechanism
Reexamination Certificate
2000-07-26
2003-06-17
Nguyen, Thinh (Department: 2853)
Incremental printing of symbolic information
Ink jet
Ejector mechanism
C347S063000, C347S065000
Reexamination Certificate
active
06578952
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a liquid discharging method, a liquid discharge head and a recording apparatus using such a liquid discharge head, in which desired liquid is discharged by generating a bubble by thermal energy, and more particularly, it relates to a liquid discharge head using a movable separation diaphragm displaced by utilizing generation of a bubble.
Incidentally, a term “recording” in this specification means not only to form a desired image such as character or figure on a recording medium, but also to form a meaningless image such as pattern on a recording medium.
2. Related Background Art
Conventionally, in recording apparatuses such as printers, an ink jet recording method, i.e., a so-called bubble jet recording method in which a bubble is generated by applying energy such as thermal energy to liquid ink in a flow path and the ink is discharged from a discharge port by an acting force generated by abrupt change in volume due to generation of the bubble thereby to adhere the discharged ink to a recording medium to form an image is well known.
As disclosed in U.S. Pat. No. 4,723,129, generally, the recording apparatus using such a bubble jet recording method comprises discharge ports for discharging ink, flow paths communicated with the discharge ports, and electrical/thermal converters as energy generating means for discharging the ink in the flow path(s).
According to such a recording method, since a high quality image can be recorded at a high speed with low noise and the discharge ports can be arranged with high density in a head performing this method, there can be provided many excellent advantages that a recorded image having high resolving power can be obtained by a compact apparatus, a color image can easily be obtained and the like. Thus, the bubble jet recording method has recently been used in many office equipments such as printers, copying machines, facsimiles and the like and has also been applied to industrial systems such as a print device.
As the bubble jet technique is used in wide technical fields, the following requests have recently been made.
A driving condition for providing a liquid discharging method capable of effecting good ink discharge on the basis of high speed ink discharge and stable generation of the bubble in order to obtain the high quality image has been proposed or an improved flow path configuration for obtaining a liquid discharge head having a high speed filling ability for re-filling or replenishing the liquid into the flow path for compensating the discharged liquid in consideration of high speed recording has been proposed.
Other than such heads, as disclosed in Japanese Patent Application Laid-open No. 6-31918, in consideration of a back wave (pressure directing a direction opposite to a direction toward the discharge port) generated by the generation of the bubble, a structure for preventing the back wave leading to loss energy at the discharge port has been proposed. In this proposed technique, a triangular portion of a triangular plate member is opposed to a heater for generating the bubble. In this technique, the back wave is temporarily and slightly suppressed by the plate member. However, since a relationship between the growth of the bubble and the triangular portion is not described at all and there is no such idea, this technique causes the following problems.
That is to say, in this technique, since the heater is located on a bottom of a recess not to be communicated with the discharge port straightly, a shape of a liquid droplet is not stabilized, and, since the growth of the bubble is permitted around an apex of the triangle, the bubble is grown from one side of the triangular plate member to the entire opposite side, with the result that the normal growth of the bubble is completed in the liquid as if there is no plate member. Accordingly, the grown bubble has no relationship to the plate member at all. Conversely, since the entire plate member is enclosed by the bubble, upon contraction of the bubble, the re-fill of the liquid to the heater located in the recess generates turbulent flow, with the result that small bubbles are trapped in the recess, thereby worsening the principle itself for effecting the liquid discharge on the basis of the growth of the bubble.
European Patent Appliction No. 0 436 047 A1 discloses a technique in which a first valve disposed between a discharge port and a bubble generation portion to block communication therebetween and a second valve disposed in the bubble generating portion and an ink supplying portion to completely block communication therebetween are opened and closed alternately (
FIGS. 4
to
9
in EP 436047A1). However, in this technique, since these three chambers are partitioned to two chambers, upon discharging, the ink droplet creates a long ink tail to thereby generate many satellite dots in comparison with the normal technique for effecting bubble growth, bubble contraction and bubble extinction (it is guessed that the effect of retarding the meniscus due to bubble extinction cannot be utilized). Further, upon refilling, although the liquid is supplied to the bubble generating portion as a result of the bubble extinction, since the liquid cannot be supplied to the vicinity of the discharge port until the next bubble is generated, not only dispersion in discharged liquid droplets becomes great but also discharge response frequency becomes very small, and, thus, this technique cannot be put to a practical use.
On the other hand, unlike the above technique, the applicant has proposed many techniques in which a movable member (plate-shaped member having a free end disposed near a discharge port and at a downstream side of a fulcrum) contributing to effective discharge of a liquid droplet is used. Among them, Japanese Patent Application Laid-open No. 9-48127 discloses a technique in which an upper limit of displacement of the movable member is regulated to prevent the disturbance of performance of the movable member. Further, Japanese Patent Application Laid-open No. 9-323420 discloses a technique in which a position of a common liquid chamber located at an upstream side of the movable member is shifted toward the free end of the movable member, i.e., toward the downstream direction to enhance the re-filling ability by utilizing the advantage of the movable member. Since these techniques adopt a construction in which the grown bubble is released at once toward the discharge port from a condition that the bubble is temporarily constrained by the movable member, a relationship between the entire bubble and elements associated with the formation of the liquid droplet was not noticed.
In the next step, Japanese Patent Application Laid-open No. 10-24588 discloses a technique in which a part of a bubble generating area is released from the movable member in consideration of growth of the bubble due to pressure wave (acoustic wave) propagation as a factor associated with the liquid discharging. However, also in this technique, since only the growth of the bubble in the liquid discharging is noticed, a relationship between the entire bubble and elements associated with the formation of the liquid droplet was not noticed.
In the past, although the fact that a forward part (edge shooter type) of a bubble generated by film boiling affects a great influence upon the discharging was well known, the fact that such a part is caused to contribute to the formation of the discharge liquid droplet more effectively was not noticed, and the inventors have investigated to analyze such facts.
Further, the inventors noticed a relationship between the displacement of the movable member and the generated bubble and found the following effective technique.
Such a technique regulates the displacement of the free end of the movable member with respect to the growing bubble by a stopper. By regulating the displacement of the movable member by means of the stopper, the growth of the bubble toward the upstream direction is regulated
Ishinaga Hiroyuki
Sugama Sadayuki
Sugiyama Hiroyuki
Canon Kabushiki Kaisha
Fitzpatrick ,Cella, Harper & Scinto
Nguyen Thinh
Tran Ly T
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