Patent Publication Number: US-6336711-B1

Title: Spraying device of an ink jet printer

Description:
CLAIM OF PRIORITY 
     This application makes reference to, incorporates the same herein, and claims all benefits accruing under 35 U.S.C. § 119 from my application entitled Jetting Apparatus in Inkjet Printer filed with the Korean Industrial Property Office on Dec. 19, 1997 and there duly assigned Ser. No. P97-70917 by that Office. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to the field of incremental printing, in particular to ink jet printing devices, and more particularly to an ink jet spraying device using a liquid actuator to drive a membrane. 
     2. Discussion of Related Art 
     There are several methods used in spraying devices of ink jet printers. First of all, there is a method spraying bubbles formed in an ink chamber using the heat incurred when electric energy is delivered to a resistant element. In this method, however, the ingredients of ink undergo thermal changes as the bubbles formed by high heat. Also, the internal life expectancy of the device is reduced due to an impact wave by the bubbles. These factors can noticeably reduce the quality of the printing to an undesirable level. 
     Another method is to use a membrane between the heating unit and the ink. In an earlier example of such a device, a heating unit performing heating is formed on a surface of a substrate layer by electric energy. Electrodes of different polarity which input power offered from a power unit and offer the electric energy to the heating unit are formed on the surfaces of the substrate and the heating unit. A protection layer is formed on surfaces of the electrodes and the heating unit. The insulation layer is formed with a regular interval on some locations pertinent to the surface of electrodes on protection layer. And a membrane layer is formed on a surface of the insulation layer. The spaces formed by the protection layer, the electrodes, the insulation layer and the membrane layer are called the heating chamber. Ink is stored in an ink chamber formed by an ink chamber barrier on a surface of the membrane layer. And a nozzle plate having an opening is formed on a surface of ink chamber barrier. And a liquid actuator which is a liquid with a low boiling point is stored in the heating chamber. 
     Thus, in this device, the heating chamber configuration has a protection layer formed on the heating unit. The energy transmitted to a liquid actuator within heating chamber is transmitted in inverse proportion to the thickness of protection layer. Accordingly, it is necessary to drive the device with high energy and low frequency, with a result of high power consumption and low printing speed. 
     A membrane-containing spraying unit generally uses a liquid actuator which is different from ink. Examples from the contemporary art of inkjet inks for the first mentioned method of inkjet printing are seen, for example, in the following U.S. Patents. U.S. Pat. No. 5,772,741, to Spinelli, entitled Aqueous Ink Jet Ink Compositions, discusses an inkjet ink containing a non-aqueous carrier, which can be one of many organic solvents, among which heptane is mentioned. U.S. Pat. No. 5,594,044, to Yang, entitled Ink Jet Ink Which Is Rub Resistant To Alcohol, and U.S. Pat. No. 5,825,391, also to Yang, entitled Method For Forming Images Using A Jet Ink Which Is Rub Resistant To Alcohol, discuss an inkjet ink containing one of many organic solvents, among which heptane is mentioned. In these three patents, however, the compositions are designed to be used as the ink in an inkjet printer, and not as a liquid actuator in a membrane-containing spraying device. 
     U.S. Pat. No. 5,821,962, to Kudo et al., entitled Liquid Ejection Apparatus And Method, discusses a bubble jet device having a movable member driven by the formation of a bubble in a fluid, with the movable member ejecting the ink. The movable member does not, however, form a membrane completely enclosing the heating chamber, as in the membrane-containing device described above. The patent discusses omitting a protection layer on the resistance layer when certain materials are used for the resistance layer and the liquid; specifically, iridium-tantalumaluminum alloy is mentioned for the resistance layer but no example is given for the liquid. The patent discusses various liquids which may be used as bubble generation liquids, including n-heptane. As noted, this patent discusses a device of a design which is different from the membrane-containing device discussed above in that the movable member does not enclose the heating chamber. 
     Based on my observation of the art, then, I have found that what is needed is an ink-jet print head which does not suffer from the ink and device deterioration problems of the ink jet spraying device not containing a membrane, and which does not suffer from the high power consumption and slower print speed of the earlier spraying device which does contain a membrane. 
     SUMMARY OF THE INVENTION 
     It is therefore an object of the present invention to provide an improved spraying device for an inkjet printer. 
     It is a further object of the present invention to provide a spraying device for an inkjet printer having a high internal life expectancy. 
     It is a yet further object of the present invention to provide a spraying device for an inkjet printer having high print quality. 
     Is a still further object of the present invention to provide a spraying device with low power consumption. 
     It is a still yet further object of the present invention to provide a spraying device which allows high-speed printing. 
     It is another object of the present invention to provide a spraying device which is less expensive to produce. 
     The present invention provides a spraying device which does not show any chemical reaction even though the liquid actuator within the heating chamber is adhered closely to the heating device. The present invention also provides a spraying device which brings about vapor pressure in a short time. To achieve these objects, one aspect of the present invention is to use an isomer of heptane (C 7 H 16 ), or perfluoroheptane (C 7 F 16 ), in particular n-heptane or n-perfluoroheptane, as a liquid actuator or working fluid filling the heating chamber. The other feature of the present invention is that a protection layer is not required on the surface of the heating unit. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     A more complete appreciation of the invention, and many of the attendant advantages thereof, will be readily apparent as the same becomes better understood by reference to the following detailed description when considered in conjunction with the accompanying drawings in which like reference symbols indicate the same or similar components, wherein: 
     FIG. 1 is a vertical cross-sectional view of an earlier spraying device of an ink jet printer. 
     FIG. 2 is a vertical cross-sectional view of spraying device of an ink jet printer according to the present invention. 
    
    
     DETAILED DESCRIPTION OF THE DRAWINGS 
     Turning now to the drawings, the earlier ink jet spraying device containing a membrane is shown in FIG.  1 . Heating unit  102  performing heating is formed on a surface of substrate layer  101  by electric energy. Electrodes of different polarity  103   a,    103   b  which input power offered from power unit  112  and offer the electric energy to heating unit  102  are formed on the surfaces of substrate  101  and heating unit  102 . Protection layer  104  is formed on surfaces of electrodes  103   a,    103   b  and heating unit  102 . Insulation layer  105  is formed with a regular interval on some locations pertinent to the surface of electrodes  103   a,    103   b  on protection layer  104 . And membrane layer  106  is formed on a surface of insulation layer  105 . The spaces formed by protection layer  104 , electrodes  103   a,    103   b,  insulation layer  105  and membrane layer  106  are called heating chamber  108 . Ink is stored in an ink chamber  109  formed by ink chamber barrier  107  on a surface of membrane layer  106 . And a nozzle plate having an opening is formed on a surface of ink chamber barrier  107 . And a liquid actuator or working fluid which is a liquid with a low boiling point is stored in the heating chamber. 
     Thus, in this device, heating chamber  108  is configured by forming protection layer  104  on heating unit  102 . The energy transmitted to a liquid actuator within heating chamber  108  is transmitted in inverse proportion to the thickness of protection layer  104 . Accordingly, it is necessary to drive the device with high energy and low frequency, with a result of high power consumption and low speed printing. 
     Hereinafter, a preferred embodiment of the present invention will be described with reference to the attached drawings as follows. FIG. 2 illustrates the configuration of the spraying device of ink jet printer according to the present invention. The device of FIG. 2 comprises heating unit  202  formed on a surface of substrate  201 ; plural electrodes  203   a,    203   b  formed on the surfaces of substrate  201  and heating unit  202  with a regular distance and offering electric energy to heating unit  202 ; a power source for supplying electric energy with different polarity to electrodes  203   a,    203   b;  insulation layer  205  formed on a surface of the plural electrodes  203   a,    203   b  with a regular distance; membrane layer  206  formed on a surface of insulation layer  205  and causing a volume change by thermal expansion; ink chamber barrier  207  located on a surface of membrane layer  206  and forming a insertion path for ink; and nozzle plate  210  located on a surface of ink chamber barrier  207  and having plural openings  211 . 
     An important point about the present invention is that no protection layer is formed between electrodes  203   a,    203   b  and insulation layer  205  and between heating unit  202  and the working fluid, unlike the described earlier inkjet device. Thus a liquid actuator within heating chamber  208  is in contact with the heating unit  202  and electrodes  203   a  and  203   b.    
     Heating unit  202  consists of TaAl or TiB 2 . An isomer of heptane (C 7 H 16 ) or perfluoroheptane (C 7 F 16 ) is used as a working fluid located inside heating chamber  208 . In particular, n-heptane or n-perfluoroheptane may be used. Both of these substances share the property of being noncorrosive and non-reactive to alloys consisting of Cu, Al, Ni, Zn, Ti, N, etc. used as electrodes  203   a  and  203   b  and being noncorrosive to TaAl or TiB 2  that make up heating unit  202 . Also, these substances share the features that they are not inflammable, explosive or poisonous. 
     A liquid actuator is in direct contact with heating unit  202  which consists of TaAl or TiB 2  as well as electrodes  203   a  and  203   b  which may be made of Cu, Al, Ni, Zn, Ti and N. Ink in the ink chamber is sprayed by changing the volume of the membrane through the expansion due to heating. And very rapid production of vapor pressure is produced since a liquid actuator contacts directly with the heating unit and readily transmits the heat. Thus high speed printing becomes possible by using low energy. 
     As described above, the present invention requires a protection layer to protect the heating unit. And vapor pressure is produced in a short time by means that liquid actuator contacts directly with the heating unit and transmits the heat. And high speed printing becomes possible by using low energy. Also, a production process in order to produce the protection layer is not required, so the production costs are saved.