Incremental printing of symbolic information – Ink jet – Controller
Reexamination Certificate
2000-08-03
2003-04-01
Barlow, John (Department: 2853)
Incremental printing of symbolic information
Ink jet
Controller
C347S021000, C347S043000, C347S085000
Reexamination Certificate
active
06540317
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a printer head, an ink jet printer and a method for driving the printer head.
2. Description of the Related Art
It has recently become widespread to draw up documents on computers that are used as desktop publishers, especially in offices. And lately demands for outputting not only characters and graphics but also colored natural pictures like photographs together with them has become increased. Therefore, it has been required to print high quality natural pictures, and gradation expression with the expression of halftones has consequently becomes important.
Furthermore, the so-called on demand type printers have been coming into wide use in recent years because they are suitable for miniaturization and reduction in cost. The on demand type printers perform recording by discharging ink droplets from nozzles only when it is required to print according to control signals that are in compliance with recording signals to make the ink droplets adhere on a material to be recorded, such as a sheet of paper or a film.
As aforesaid, although various methods as a method for discharging ink droplets from nozzles have been proposed, a method using a piezoelectric element or a heating element is generally used. The former is a method for discharging ink by applying pressure to it by means of the deformation of the piezoelectric element. The latter is a method for discharging ink by the pressure of bubbles produced by vaporizing the ink in nozzles by the heat generated by the heating element.
In addition, various methods have been proposed as a method for mimetically realizing the aforementioned gradation expression with the expression of halftones on the aforementioned on demand type printer that discharges ink droplets. That is, as a first method, there is a method that expresses the halftone gradation by controlling the sizes of the ink droplets to be discharged by varying the voltage value or the pulse width of a pulse voltage to be supplied to the piezoelectric element or the heating element to make diameters of dots to be printed variable.
However, the above first method has a defect that expressible gradation steps are not many, in particular, the expression of low density is very difficult, because there is a limit to the minimum diameter of the droplets owing to the fact that, if the voltage or the pulse width supplied to the piezoelectric element or the heating element is decreased too much, the ink is not discharged. Consequently, the first method is not satisfactory for a printout of a natural picture.
Besides, as a second method, there is a method that realizes a gradation expression by constituting one pixel with a matrix composed of e.g. 4×4 dots without varying the diameters of the dots, and by performing the picture processing such as the so-called dither method or the error diffusion method of each matrix.
However, although seventeen gradation steps of the density can be expressed by the second method if one pixel is composed of the 4×4 matrix, the resolution of a printed picture deteriorates to one fourth if the picture is printed, for example, at the dot density same as that of the first method. Consequently, the printed picture becomes conspicuous in roughness, and thus the second method is also not satisfactory for a printout of a natural picture.
Accordingly, for principally resolving the problems of the conventional on demand type printers, the inventors of the present invention have proposed such a printer as was described in, for example, JP-A 201024/93 and JP-A 195682/95, which printer mixes ink and diluent, i.e. a transparent solvent, together at a predetermined mixing ratio just before discharging to be diluent ink, and immediately discharges the diluent ink from nozzles to make it adhere on a material to be recorded for recording.
Although, in the following description, the system in which ink is used as a quantification medium and diluent is used as a discharge medium, and in which the ink as the quantification medium is mixed with the diluent as the discharge medium to be the diluent ink, and further in which recording is done by discharging the discharge medium, is called as a carrier jet system among the aforementioned systems, there is no problem in a printer even if the diluent is used as the quantification medium and the ink is used as the discharge medium.
A printer in accordance with such a carrier jet system can control the density of the mixed solution to be discharged by varying the mixing ration of the ink and the diluent by varying the amount of the quantification medium that is either the ink or the diluent, and then the printer can separately vary the density of every dot to be printed. Consequently, the printer can print out a natural picture rich in the halftone gradation thereof without producing the deterioration of its resolution.
As a two liquids mixing type printer as stated above, there is the so-called external mixing type printer as will be shown in the following, for example.
The printer includes a quantification medium pressuring chamber where a quantification medium is introduced and a discharge medium pressuring chamber where a discharge medium is introduced. An opening of a quantification medium nozzle communicating with the quantification medium pressuring chamber and an opening of a discharge medium nozzle communicating with the discharge medium pressuring chamber adjoin to each other. The printer oozes the quantification medium from the quantification medium nozzle through the opening surface of the nozzle to the discharge medium nozzle, and makes the oozed quantification medium contact with the discharge medium plugged in the vicinity of the tip of the discharge medium nozzle to form the mixed solution. And then, the printer discharges the discharge medium from the discharge nozzle to discharge the quantification medium and the discharge medium as the mixed solution.
In such a structure, because the qualification nozzle and the discharge nozzle are separately formed, the quantification medium and the discharge medium do not diffuse while they are waiting for being discharged, and mutual affluxes at the time of mixing and discharging can be prevented.
When printing is done by the printer head shown in
FIG. 21
, it is done along the following description. The description is now done by making use of a timing chart for the imposition of driving voltages shown in FIG.
22
. The so-called laminated type piezoelectric elements are used as a first laminated type piezoelectric element
43
and a second laminated type piezoelectric element
44
. There are two types of laminated type piezoelectric elements, one of them utilizes the displacement thereof in the shrinking direction (the so-called d-
31
direction), and the other utilizes the displacement thereof in the elongating direction (the so-called d-
33
direction). The latter is used as both of the first laminated type piezoelectric element
43
and the second laminated type piezoelectric element
44
.
As shown in the timing chart of the imposition of the driving voltages of
FIG. 22
, at first, at a point of time indicated by reference character (a) in
FIG. 22
, positive voltages, 10 V for the first laminated type piezoelectric element
43
and 15 V for the second laminated type piezoelectric element
44
, are being imposed on them as driving voltages. The horizontal axis of
FIG. 22
indicates time, and the vertical axis of
FIG. 22
indicates driving voltages for the first laminated type piezoelectric element
43
and the second laminated type piezoelectric element
44
. At this time, a quantification medium
45
and a discharge medium
49
are in their waiting state shown in FIG.
23
(A).
Next, at a point of time indicated by reference character (b) in
FIG. 22
, the driving voltage for the first laminated type piezoelectric element
43
starts to be lowered until a point of time indicated by reference character (d) in
FIG. 22
to be 0 V over a period of 50 &mgr;s. Then, the f
Ando Makoto
Okamoto Kenji
Yamada Emi
Barlow John
Liang Leonard
Sonnenschein Nath & Rosenthal
Sony Corporation
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