Incremental printing of symbolic information – Ink jet – Ejector mechanism
Reexamination Certificate
1999-08-18
2001-12-18
Barlow, Jr., John E. (Department: 2853)
Incremental printing of symbolic information
Ink jet
Ejector mechanism
C347S059000
Reexamination Certificate
active
06331048
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a printhead for printing data on a printing medium by discharging ink in accordance with an inkjet printing method and, more particularly, to an inkjet printhead characterized by the layout of circuit blocks on the semiconductor substrate of the printhead having a plurality of electrothermal converters.
2. Description of the Related Art
A printhead mounted on a printing apparatus according to a conventional inkjet method has a circuit arrangement like the one shown in FIG.
4
. The electrothermal converter (heater) of this printhead and its driving circuit are formed on a single substrate
400
by a semiconductor process technique, as disclosed in, e.g., Japanese Patent Laid-Open No. 5-185594. In
FIG. 4
, reference numerals
401
denote electrothermal converters (heaters) for generating heat energy;
402
, power transistors each for supplying a desired current to a corresponding heater
401
;
404
, a shift register for supplying a current to each heater
401
and temporarily storing image data representing whether ink is to be discharged from the nozzle of the printhead;
405
, a transfer clock (CLK) input terminal formed in the shift register
404
;
406
, an image data input terminal for inputting serial image data for turning on/off the heaters
401
;
403
, a latch circuit for latching image data for each heater in units of blocks;
407
, a latch signal input terminal for inputting a latch timing signal (LT) to the latch circuit
403
;
408
, a block selection circuit (3-input 8-output decoder) for selecting a block;
409
,
410
, and
411
, block selection circuit input logic signals, among which the signals
409
and
411
respectively correspond to the most and least significant bits;
419
, a circuit for receiving a block selection output signal
416
and latch output signal
417
and outputting an AND;
413
, a switch for determining a timing for flowing a current through the heater
401
;
415
, a heat signal input terminal (HEAT) for inputting a timing for controlling the switch
413
;
414
, a power supply line for applying a predetermined voltage and supplying a current to the heater;
412
, a GND line which receives a current via the heater
401
and power transistor
402
;
420
, a circuit unit around the heater that includes the components
401
,
402
,
412
,
414
,
413
, and
419
; and
430
, a unit which includes all the circuits
403
,
404
,
408
, and
420
necessary for controlling discharge of one type of ink.
FIG. 7
shows an example of input and output waveforms to and from the block selection circuit
408
that is shown in FIG.
4
. Reference numerals
409
,
410
, and
411
denote block selection input signals;
700
to
707
, block selection output signals; and
710
, a virtual timing signal which explains the timing, and takes values up to 7 such that it takes 0 for a period during which the block selection output signal
700
is at “Hi” level, and 1 for a period during which the block selection output signal
701
is at “Hi” level.
Operation of the shift register circuit
404
and latch circuit
403
that are shown in
FIG. 4
will be described with reference to FIG.
8
.
FIG. 8
shows timings when the timing signal
710
has a value of 0. Also when the timing signal
710
has one of values of 1 to 7, signals are input at similar timings. Reference numeral
405
denotes a shift register transfer clock (CLK) signal; and
406
, an image data input signal. The transfer clock input terminal
405
receives transfer clocks (CLK) by the number of bits of one block of image data stored in the shift register
404
. Data is transferred to the shift register
404
in synchronism with the rise timing of the transfer clock (CLK). Image data (DATA) for turning on/off each heater
401
is input from the image data input terminal
406
.
Image data stored in the shift register
404
will be called one image block. In this case, the number of heaters for one image block is eight, but can be arbitrarily set in practice. Transfer clock (CLK) pulses equal in number to the heaters
401
for one image block are input to transfer image data (DATA) to the shift register
404
. Then, a latch signal (LT) is input to the latch signal input terminal
407
to latch image data corresponding to each heater in the latch circuit
403
.
Referring back to
FIG. 4
, operation will be described again. Anyone of eight outputs
417
of the latch circuit
403
and anyone of eight outputs
416
of the decoder
408
are input to the AND circuit
419
. When both the two inputs to the AND circuit
419
are at “Hi” level, a “Hi” signal is input to the switch
413
. While the heat signal (HEAT)
415
for controlling the switch
413
is at “Hi” level, the switch
413
is kept on. By keeping the switch
413
on for a proper length of time by supplying the heat signal (HEAT)
415
, a current flows into the power transistor
402
and heater
401
via the power supply line
414
during the ON period of the switch
413
, and flows into the GND line
412
. At this time, the heater
401
generates heat necessary for discharging ink, and ink corresponding to image data is discharged from the nozzle of the printhead.
The number of heaters which can be independently controlled by the latch circuit and decoder is determined by the product of the numbers of outputs
416
and
417
, and in this case, 8×8=64 at maximum.
Reference numeral
502
denotes an ink supply hole formed at almost the center of the chip by anisotropy etching or sandblasting in order to supply ink from the rear surface of the semiconductor substrate. Inks that are supplied from the ink supply holes are supplied separately to the heaters
401
that are formed on the substrate
400
through ink passages(not shown). In accordance with the drive of the heaters, inks are supplied from orifices which are formed in the position corresponding to each heaters.
The unit
430
includes circuits necessary for discharging one type of ink that is supplied from the one ink supply hole. In
FIG. 4
, the circuit blocks
420
are laid out on the two sides of the ink supply hole
502
. In this case, a total of
64
heaters are laid out on the two sides of the ink supply hole
502
. The block selection circuit (decoder)
408
, and the latch circuit
403
and shift register
404
are laid out on opposite sides via the transistor section
420
. If they are laid out on the same side of the transistor section
420
, the latch circuit
403
, shift register
404
, and decoder
408
have many elements, and the large area is required for arranging the units. Further, the latch circuit output line and decoder output line cross each other, which reduces the area and degrades reliability. Still further, the input terminals
405
,
406
,
407
,
409
,
410
, and
411
must be arranged in a region on the same side of the substrate, which requires a large substrate size. For these reasons, the decoder
408
, latch circuit
403
, and shift register
404
are generally laid out as shown in FIG.
4
.
FIG. 3
is a perspective view of the inkjet printhead which has circuit arrangement explained in
FIG. 4
taken along the plane ABCD for descriptive convenience. The flow of ink will be explained with reference to FIG.
3
.
An orifice plate
300
is mounted on the surface of the substrate
400
, and a space for flowing ink, i.e., an ink passage
301
on the heater is defined in the orifice plate
300
. An ink tank (not shown) is mounted on the lower surface of the semiconductor substrate
400
, and from the lower surface side, the ink is supplied to the ink passage through the ink supply hole. Ink is guided onto each heater
401
via the ink passage
301
. A current is flowed through the heater to apply heat to the ink, and ink droplets are discharged from an orifice
302
, which is formed in the position corresponding to each heaters, in a direction perpendicular to the substrate plane by bubbles produced by boiling ink. Ink droplets
303
attach to a printing medium (not
Barlow Jr. John E.
Canon Kabushiki Kaisha
Fitzpatrick ,Cella, Harper & Scinto
Stephens Juanita
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