Incremental printing of symbolic information – Ink jet – Ejector mechanism
Reexamination Certificate
1997-03-17
2002-04-23
Barlow, John (Department: 2853)
Incremental printing of symbolic information
Ink jet
Ejector mechanism
Reexamination Certificate
active
06375312
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the invention
The present invention relates to an improved heat generating resistor comprising a specific tantalum nitride containing TaN
0.8
which excels not only in terms of heat generation performance but also in terms of durability upon repeated use and which can be produced at a reduced production cost. The heat generating resistor is applicable to various outputting mechanism-bearing devices or systems such as printers, facsimiles, copying machines, and composite mechanized retrieval systems, and also to their terminal printers of printing an object outputted on a printing medium. Particularly, the heat generating resistor is suitable for use particularly in a liquid jet system of discharging and flying printing liquid utilizing a thermal energy to thereby print an image on a medium such as ordinary paper, synthetic paper, fabric, or the like. The present invention includes an improved substrate provided with said heat generating resistor for a liquid jet head, a liquid jet head provided with said substrate, and a liquid jet apparatus provided with said liquid jet head. The present invention enables to produce any of said substrate, liquid jet head, and liquid jet apparatus respectively at an improved precision and at a reduced production cost.
2. Related Background Art
U.S. Pat. No. 3,242,006 (hereinafter referred to as Literature 1) discloses a tantalum nitride (TaN) film resistor (hereinafter referred to as TaN film resistor) formed by impressing a DC voltage of 5000 V between a cathode composed of Ta and an anode in a gaseous atmosphere comprising N
2
gas and Ar gas under conditions of 400° C. for the atmospheric temperature, 400° C. for the substrate temperature, and 1×10
−4
mmHg for the partial pressure of the N
2
gas to sputter the Ta cathode. Literature 1 describes that the TaN film is of a sodium chloride type structure rather than the anticipated hexagonal type structure. Further, Literature 1 describes production of Ta
2
N of hexagonal structure (hereinafter referred to as Ta
2
N
hex
) and mixtures of the Ta
2
N
hex
and TaN of a cubic structure. Hence, it is understood that Literature 1 discloses a resistor comprising a film composed of a tantalum nitride substantially comprised of TaN only (seemingly contaminated with foreign matters) (this tantalum nitride material will be occasionally called TaN single body in the following), a tantalum nitride material substantially comprised of Ta
2
N only (seemingly contaminated with foreign matters) (this tantalum nitride material will be occasionally called Ta
2
N single body in the following), or a tantalum nitride material comprised of a mixture of these.
Now, there are known a variety of printing systems of discharging and flying ink utilizing a thermal energy to form an ink droplet whereby printing an image on a printing medium. Of those printing systems, the so-called on-demand type ink jet printing system has been evaluated as being the most appropriate because the noise cased upon conducting printing can be reduced to a negligible order.
U.S. Pat. No. 4,849,774 (or German Patent No. 2843064) (hereinafter referred to as Literature 2) discloses a on-demand type bubble jet printing system which attains on-demand printing by causing film boiling for ink to discharge ink in the form of an ink droplet whereby printing an image on a printing medium. Literature 2 describes the use of a heat generating resistor composed of a metal boride (specifically, HfB
2
) or tantalum nitride. The tantalum nitride described in Literature 2 is apparent to include the TaN single body, Ta
2
N
hex
single body, and mixtures of these described in Literature 1 in view of the priority dated of Literature 2 in relation to the publication date of Literature 1.
Now, it is understood that the heat generating resistor comprising HfB
2
or tantalum nitride is compatible with the film-boiling phenomenon and satisfies the requirements relating to ink discharging characteristics, printing speed, and printing condition as far as the bubble jet printing system described in Literature 2 is concerned.
However, in on-demand type bubble jet printing systems provided with an markedly increased number of discharging outlets which have been developed in recent years after (specifically, after 1983) or will be developed in the future, it is commonly recognized that not the heat generating resistor composed of tantalum nitride but only a heat generating resistor composed of HfB
2
or TaAl satisfies the conditions required for such markedly increased discharging outlets in terms of stability and durability.
Incidentally, there are a number of reports on thermal heads having a heat generating resistor composed of tantalum nitride in which the heat generating resistor is directly contacted with a heat-sensitive paper or an ink ribbon. The heat generating resistor herein is understood to be similar to that described in Literature 1.
Other than this, U.S. Pat. No. 4,737,709 (hereinafter referred to as Literature 3) discloses a thermal head having a heat generating resistor comprising a film of tantalum nitride (Ta
2
N) having a hexagonal close-packed lattice oriented in (101) direction which is formed by the reactive sputtering process. It is understood that Literature 3 is directed to an improvement in the thermal head in terms of the durability by using said specific tantalum nitride film as the heat generating resistor.
It should be noted to the fact that any of the tantalum nitrides films described in these documents has never been actually used as a heat generating resistor of an ink jet head, although they have been used in a thermal head.
Description will be made of the reason for this. That is, in the case of a thermal head, the electric power applied to the heat generating resistor is about 1 W for a period of 1 &mgr;sec. On the other hand, in the case of an ink jet head, in order to conduct film-boiling of ink for a very short period of time, an electric power of a wattage in the range of from 3 W to 4 W is applied to the heat generating resistor, for instance, for a period of 7 &mgr;sec. It is understood that the electric power applied to the heat generating resistor for such a short period of time in the case of the ink jet head is greater as much as several times the electric power applied to the heat generating resistor for a relatively longer period of time in the case of the thermal head.
In order to examine whether or not the foregoing conventional tantalum film resistors are practically usable as the heat generating resistor for an ink jet head, the present inventors prepared a plurality of ink jet heads each having a heat generating resistor composed of any of the foregoing conventional tantalum nitride films, and subjecting each of the ink jet heads to printing. As a result, there was obtained a finding in that there is a tendency for any of the heat generating resistors to be greatly varied in terms of the resistance value within a short period of time upon the application of a large quantity of an electric power thereto. Such variation in terms of the resistance value for the heat generation resistor is not serious in the case of a thermal head since it is not instantly influenced to an image obtained. However, in the case of an ink jet head, a serious problem entails in that generation of a bubble at ink is not stably occurred as desired to cause a decrease in the quantity of an ink droplet discharged, resulting in making an image printed to be inferior in terms in the quality.
Hence, the reason why any of the conventional tantalum nitride heat generating resistors described in the above documents has never been practically used in an ink jet head can be understood. In fact, there cannot be found any report in which the use of a tantalum nitride heat generating resistor in an ink jet head has been studied. And, in the ink jet heads in recent years, a heat generating resistor composed of HfB
2
has been actually often used as their heat generating resistor.
Other than the above-describe
Ikeda Masami
Izumida Masaaki
Makino Kenji
Matsumoto Shigeyuki
Naruse Yasuhiro
Brooke Michael S
Fitzpatrick, Cella Harper & Scinto.
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