Incremental printing of symbolic information – Ink jet – Ejector mechanism
Reexamination Certificate
2003-03-21
2004-05-18
Brooke, Michael S (Department: 2853)
Incremental printing of symbolic information
Ink jet
Ejector mechanism
C347S061000
Reexamination Certificate
active
06736490
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an ink jet printer. More particularly, the invention relates to an ink jet recording head used for the bubble jet printer that utilizes bubbling phenomenon, and the like, and to a non-linear electrical element as well.
2. Related Background Art
As regards the technology of non-linear current voltage element, there has been proposed since a long time ago the PTC thermistor having the non-linear characteristic in which the resistance value rises enormously at a certain temperature (curie temperature), and this thermistor has been utilized for various products. For example, there has been proposed in the specification of Japanese Patent Laid-Open Application No. 05-47457 an organic face heat-generating element having the positive temperature coefficient (PTC) characteristic. Also, in the specification of Japanese Patent Laid-Open Application No. 05-258840, there has been proposed a PTC heat-generating device provided with plural PTC elements connected in parallel. Also, in the specification of Japanese Patent Laid-Open Application No. 04-97927, there has been disclosed an ink discharge apparatus that holds the temperature of ink within a desired range of temperature using PTC thermistor heat generating element.
Also, regarding the technology of the non-linear current voltage element, there have been proposed in the specifications of Japanese Patent Laid-Open Application Nos. 2001-71499, 2002-046274, 2002-046275, 2002-067325, and 2002-067326 the applications of MIM element to the bubble jet recording head having the current voltage characteristic (the so-called MIM type current voltage characteristics) in which almost no current runs at a certain voltage or less, and current is allowed to run at a certain voltage or more.
FIG. 7
is a conceptual view that shows the MIM type electrical characteristic. Here, it is desirable to make the current voltage characteristic of the non-linear element the one in which only a sufficiently small current is allowed to run by the application of voltage of a small absolute value on either sides of the positive voltage and negative voltage so that the non-linear element does not generate heat even by the application of non-selective voltage having unsettled polarity. Therefore, as shown in
FIG. 7
, it is particularly desirable for the current voltage characteristic of non-linear element to set the ratio (V
1
/V
2
) at a value of 0.5 to 2.0 for the absolute values between the +V
1
and −V
2
of the applied voltage that gives current of the absolute value I
0
, which is equivalent to the current running at the time of voltage application that enables a desired bubbling to be generated. Then, it is also desirable to make the absolute value I
0
/10 or less for the current that runs when the voltage of +V
1
/2 and −V
2
/2 is applied.
On the other hand, regarding the technology of the ink jet recording head, it is generally practiced to provide a recording head, which is applicable to a bubble jet recording method, with fine discharge ports for discharging liquid, flow path to conduct liquid to each discharge port, and heat generating means arranged for a part of each flow path. The bubble jet recording method is a recording method, in which liquid is heated locally in the flow path to a high temperature by use of heat generating means so as to bubble it to generate bubble, and then, by the utilization of such high pressure exerted at the time of bubbling, liquid is pushed out from each of the fine discharge ports so as to enable it to adhere to a recording sheet or the like for recording.
In order to make images highly precise, which are recorded by the recording technology of the kind, it is necessary to discharge extremely fine liquid droplets from the discharge ports arranged in high density. Fundamentally, therefore, it is important to form minute flow paths and minute heat generating means as well. Then, for the bubble jet recording method, a method has been proposed for forming a recording head by using photolithographic process freely, while taking advantage of the simplicity of the structure thereof, so as to arrange discharge ports, flow paths, and heat generating elements in high density for the head (see the specification of Japanese Patent Laid-Open Application No. 08-15629, for example). Also, the discharge amount of liquid droplets should be adjusted in order to discharge fine liquid droplets. To this end, a proposal has been made to use the heat-generating element the amount of heat generation of which is larger in the central portion than the edge portions thereof (see the specification of Japanese Patent Laid-Open Application No. 62-201254).
As heat generating means, it is usually practiced to use the resistive heat-generating element, which is formed by a thin film of tantalum nitride formed in a thickness of approximately 0.05 &mgr;m. When this element is energized, joule heat is generated to bubble liquid. On such resistive heat-generating element, there is arranged a cavitation-proof layer formed by metal, such as Ta, in a thickness of approximately 0.2 &mgr;m usually though an insulator, such as Sin, formed in a thickness of approximately 0.8 &mgr;m in order to prevent the surface of the resistive heat-generating element from being damaged by cavitation.
For the aforesaid recording head that adopts the bubble jet recording method, the resistive heat-generating element for use of ink bubbling usually presents variations to a certain extent due to the resistance of its own finish and the resistance generated by the connected wiring. As a result, even if voltage is applied under constant condition, there occur variations in the voltage drop due to resistance, and the heating amount of the heater formed by such resistive heat-generating element tends to vary accordingly. Therefore, for the reasons that any influences that may be given to the inferior image quality due to such variation of heating amount should be avoided, among some others, the driving voltage, which is required for driving the heater array formed by plural heaters, is provided with a higher voltage value than the voltage value needed usually for the stabilized bubbling on the entire surface of each individual resistive heat-generating element, which faces liquid. Such voltage value is particularly set at as much as approximately 1.2 times the required voltage value.
However, when the driving voltage is set at a higher value as described above, an excessive voltage is applied to the average heater beyond the voltage needed for the bubbling on the entire surface. As a result, there encountered a problem, in principle, that unwanted heating continues even after bubbling.
More specifically, if a heater is driven with 1 &mgr;s-pulse, for example, it is typical that bubbling takes place at approximately 6 &mgr;s, and than, unwanted heating (excessive heating) by the heater continues after bubbling, thus causing the heater surface to reach typically at a temperature of as high as 600 to 700° C. approximately against the bubbling temperature of 300° C. approximately. Then, depending on conditions, there is a problem that such temperature is made higher still.
To described this problem further in detail, due to the principle of the continuation of excessive heating described above, there is a fire that the following problems are encountered:
(1) In terms of effective utilization of energy, it is not preferable to supply energy wastefully after bubbling.
(2) It is necessary to design the heat resistance of the heater material at a value higher than needed in consideration of the principle cause to make the heater temperature excessively high.
Also, depending on cases, this may bring about thermal destruction, and the deterioration of durability by the repeated abrupt change of temperatures.
Under the circumstances, if it is possible to materialize the heater for bubble jet use, which is capable of suppressing the excessive heating after bubbling, there is a possibility
Brooke Michael S
Canon Kabushiki Kaisha
Fitzpatrick ,Cella, Harper & Scinto
LandOfFree
Ink jet recording head and non-linear electrical element does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Ink jet recording head and non-linear electrical element, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Ink jet recording head and non-linear electrical element will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3259964