Incremental printing of symbolic information – Ink jet – Ejector mechanism
Reexamination Certificate
1998-09-01
2001-08-21
Barlow, John (Department: 2853)
Incremental printing of symbolic information
Ink jet
Ejector mechanism
C347S068000
Reexamination Certificate
active
06276781
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention concerns a liquid jet recording head for use in a liquid jet recording apparatus, together with a manufacturing method therefor, and a liquid jet recording head drive circuit and drive method.
A liquid jet recording apparatus comprises one or more nozzles, a liquid jet recording head having a liquid chamber in contact with those nozzles, and a liquid supply system. By imparting energy to the liquid with which the liquid chamber is filled, that liquid is jetted from the nozzles, by which means text characters or graphical data are recorded. Means for imparting the energy to the liquid in general use include means for pressurizing the liquid inside the liquid chamber using a piezoelectric device, and means for heating the liquid inside the liquid chamber using a heater. The present invention concerns a liquid jet recording head, and manufacturing method therefor, that comprises means for pressurizing the liquid inside the liquid chamber using a piezoelectric device.
A liquid jet recording apparatus that uses a liquid jet recording head that uses a piezoelectric device comprises a drive circuit for generating a piezoelectric pulsing waveform for driving the piezoelectric device. The present invention concerns a liquid jet recording head drive circuit and drive method wherein a thin film transistor (hereinafter “TFT”), but more particularly a thin film transistor wherein polycrystalline silicon is used in the channels thereof (hereinafter “poly-Si TFT”), is employed.
2. Description of the Related Art
In terms of the prior art for the configuring elements pertaining to the present invention, there is Unexamined Patent Application H5-822140 [1993]. In the patent cited in this example of prior art, a liquid jet recording head and manufacturing method therefor are disclosed wherewith a liquid chamber, liquid flow path, and liquid storage chamber are formed in a monocrystalline silicon substrate, above the liquid chamber in which are formed a vibration plate and piezoelectric device that uses a piezoelectric film. With the liquid jet recording head in the prior art example cited above, however, there are problems, as described below. In the example cited, the configuration is one wherein the liquid chamber and liquid storage chamber, positioned horizontally, are connected via a liquid flow path. That being so, the liquid jet recording head in the prior art cited becomes large in its planar extent. Also, in the prior art cited, the configuration of the part that inputs drive signals to the piezoelectric device is not disclosed, but the configuration is ordinarily one wherein mounting tape having wiring patterns made thereon is connected to connecting terminals provided as electrode leads in the ends or edges of the liquid jet recording head, and a semiconductor integrated circuit wherein is formed a drive circuit made with MOS transistors is connected to the mounting tape. Accordingly, a conventional liquid jet recording head takes up a large space not only in its planar extent but also three-dimensionally. Furthermore, because the drive circuit used is based on semiconductor integrated circuitry, when the number of nozzles is increased, and particularly when a line liquid jet recording head is formed having
100
or more nozzles, the amount of space required is exceedingly large. In order to keep the price of such a drive circuit low, one may configure the drive circuit using a TFT, particularly a poly-Si TFT. However, the drive voltage cannot be raised very high due to concerns about TFT reliability, and the ON resistance of the TFT is larger than in a MOS transistor, wherefore the time required for the voltage waveform to rise in order to drive the piezoelectric device becomes long, leading to a deterioration in the liquid jetting characteristics of the liquid jet recording head.
SUMMARY OF THE INVENTION
The present invention was devised in view of the problems associated with the prior art, as noted above.
(1) One object of the present invention is to implement a line liquid jet recording head having 100 or more nozzles in a structure that is compact both in its planar extent and three-dimensionally.
(2) Another object of the present invention is to manufacture liquid jet recording heads having the compact structure noted above using an efficient method.
(3) Another object of the present invention is to provide a drive circuit and drive method for liquid jet heads wherein TFTs are used, wherewith the piezoelectric device drive voltage can be raised, and wherewith the rise time for the drive voltage waveform shortened.
In order to resolve the problems noted above, the liquid jet recording head according to the present invention is characterized by the following particulars.
(1) The liquid jet recording head comprises: nozzles; a liquid chamber for holding the liquid to be jetted; a vibration plate formed above the liquid chamber; a liquid supply hole passing through the vibration plate; and a piezoelectric device formed above the vibration plate and comprising: a lower electrode; a piezoelectric film; and an upper electrode; wherein: each are formed as a plurality lined up; the piezoelectric device is driven by a drive circuit that uses a thin film transistor provided above a dielectric substrate; the liquid supplied to the liquid chamber is made to jet out from the nozzles by bending the vibration plate and altering the volume capacity of the liquid chamber; the electrodes on the head substrate on which the nozzles, liquid chamber, vibration plate, liquid supply hole, and piezoelectric device are formed and the output terminals of the drive circuit using the thin film transistor on the dielectric substrate are connected facing each other; the space enclosed by the head substrate, the dielectric substrate end surfaces, and the mounting substrate is sealed; and a liquid storage chamber for storing the liquid supplied to the liquid chamber is formed.
(2) The alignment pitch for the piezoelectric devices and the alignment pitch for the drive circuit output terminals is made the same.
(3) A protective layer is provided at places where the upper electrodes come into contact with the drive circuit output terminals.
(4) The connecting terminals at the upper electrodes on the head substrate are positioned at both edges of the head substrate; the connecting terminals of the upper electrodes that are adjacent are positioned, respectively, on other edges of the head substrate; two circuits using thin film transistors are provided on the dielectric substrate; the connecting terminals on both sides of the head substrate and the output terminals of the circuit using thin film transistors on the two dielectric substrates are connected facing each other; a mounting substrate is provided at the surface where there is no thin film transistor in the two dielectric substrates; and a liquid storage chamber for storing the liquid supplied to the liquid chamber is formed in the space enclosed by the head substrate, the two dielectric substrate edge surfaces, and the mounting substrate.
(5) The upper electrodes on the head substrate are configured in a staggered pattern; the connecting terminals in the upper electrode pattern are positioned outside the adjacent upper electrode pattern edges; and the liquid supply hole passing through the vibration plate is positioned outside the upper electrode pattern edges and inside from the connecting terminals of adjacent upper electrodes.
(6) The nozzles, liquid chambers, vibration plates, and piezoelectric devices are arranged in two rows; the connecting terminals at the upper electrodes of the piezoelectric devices are positioned on both side edges of the head substrate; two circuits using thin film transistors are provided on the dielectric substrates; the connecting terminals on both side edges of the head substrate and the output terminals of the circuits using thin film transistors on the two dielectric substrates are connected facing each other; mounting substrates are provided on t
Barlow John
Brooke Michael S.
Hogan & Hartson LLP
Seiko Epson Corporation
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