THERMAL INK JET PRINTER

Abstract: An ink jet printer utilizing a film (1) having a plurality of ink filled holes (2) passing in front of a thermal head (5) having thermal heating elements (4) which may be ener­ gized to spout or eject ink (8) onto a record medium (11). By appropriate film and record medium motion coupled with selective energization of the thermal elements (4) in a vari­ ety of configurations, both line and serial printing may be achieved. Coloured inks may be combined to provide full colour reproduction. The film may be an endless sheet carried on rollers (9, 15) and inked in an ink tank (7), or a reciprocating sheet passing in front of the thermal head. The use of sponge rollers (16) for inking the film may also be employed.

Description: "THERMAL INK JET PRINTER" The present invention relates to a thermal ink jet printer. Many kinds of printers have been developed, both impact type and non-impact type. Non-impact printers include electronic photographic systems, electro static systems, thermal systems and ink jet systems. Ink jet systems are very silent, have low power consumption and are small and compact. However, ink jet systems have not become widely used. The main reason is due to plugging or stopping of the ink jet nozzle. Much research and development effort has been put into inks and nozzle shapes but trouble free operation of ink jet systems has not been achieved The present invention aims to eliminate the above noted difficulty and insufficiency, and to provide a new ink jet printing machine using a thermal head member. According to the present invention, there is provided a thermal ink jet printer characterised by an apertured member having at least one hole or recess therein; means for introducing ink into the or each hole or recess; at least one thermal head element disposed in contact with one surface of said apertured member, the or each said thermal head element being aligned or alignable with at least one said hole or recess; means for mounting paper or other recording medium adjacent to the opposite surface of the apertured member; and means for energising the or a thermal head element when so aligned so as to cause the ink to be ejected from the respective said at least one hole or recess and onto the recording medium as a result of bubble pressure caused by heat from said thermal head element. Preferably, the apertured member is an endless belt having a plurality of holes or recesses therein, the endless belt being arranged to receive ink from an ink tank. Thus the endless belt may be constituted by a film having holes or recesses therein each of which has a diameter of 10 to 200us. The or each thermal head element may be arranged, when so energised, to cause ink ejection from one hole or recess only or, alternatively, from a plurality of holes or recesses simultaneously. There may be a plurality of thermal head elements which are arranged transversely of the recording medium, the energising means being arranged to energise selected thermal head elements. There may be a plurality of endless belts and respective ink tanks, the ink tanks being adapted to receive inks of different colours. Thus each endless belt may have a portion disposed adjacent the recording medium, the said portions being arranged successively in a length direction or direction of travel of the recording medium, each said portion being provided with respective thermal head elements. The or each endless belt may be mounted on rollers one of which is disposed within the respective ink tank. In another arrangement, each endless belt has a portion disposed adjacent the recording medium, the said portions being arranged successively in the breadth direction of the recording medium, each said portion being provided with a respective thermal head element. In this case, each endless belt may be entrained around a respective sponge roller, which extends into a respective ink tank. By appropriate movement of the apertured member and the recording medium, coupled with selective energisation of the thermal elements in a variety of configurations, both line and serial printing may be achieved. Use may if desired be made of a reciprocating sheet passing in front of a thermal head. The invention is illustrated, merely by way of example, in the accompanying drawings, in which: Figures l(a) and l(b) respectively show a cross-sectional view and a front view of a film which may be used in a printing machine in accordance with the present invention; Figures 2(a), 2(b) and 2(c) show the principle of operation of the printing machine according to the present invention; Figure 3(a) shows a cross-sectional view of a thermal head member forming part of the printing machine in association with hole or recess ss portions of the said film, and Figure 3(b) shows a front view thereof; Figures 4(a) and 4(b) are similar to Figures 3(a) and 3(b) respectively but show an alternative embodiment of thermal head; ; Figure 5 shows a perspective view of a monochrome line printer according to the present invention; Figure 6 shows a perspective view of a colour line printer according to the present invention; Figure 7 shows a perspective view of a colour serial printer according to the present invention; and Figure 8 shows a cross-sectional view of hole or recess portions of a film which may be used in a printing machine according to the present invention. Referring to Figures l(a) and l(b),numeral 1 indicates a film of thin metal or heat resistant organic material such as polyimide, and numeral 2 indicates a plurality of hole or recess portions which may be shaped in or on said film 1, the diameter of each said hole or recess portion 2 typically being about 10 to 200pom. The diameter of the holes 2 is determined according to the thickness of the film 1 or the manner in which it is used. Figures 2(a), 2(b), and 2 (c) illustrate a basic principle of the present invention. Recording ink 3 fills a plurality of hole or recess portions 2. By moving the film 1, the hole or recess portions 2 are moved across the surface of a thermal head member 5 which has a plurality of thermal head elements 4. At the same time, the thermal head element 4 which is aligned with a hole or recess portion 2 is quickly heated by an applied electric current, whereby a bubble 6 is formed between the recording ink 3 in the respective hole or recess portion 2 and the thermal head element 4 of the thermal head member 5. As a result, part or all of the recording ink in the said respective hole or recess portion 2 is spouted from the hole 2 by pressure from the bubble 6. Each thermal head element 4 may be formed on the thermal head member 5. The film 1 is completely in contact with the thermal head element 4, causing the bubble 6 to be enlarged toward the opened hole direction of said hole or recess portion 2r whereby the direction of ink ejection is precisely controlled. In the embodiments of Figures 1 to 3, one thermal head eie-t 4 oorresponds to one hole or recess portion 2 of the film respectively. Figures 4(a) and 4(b) show another embodiment of the present invention, in which one thermal head element 4 energizes a plurality of hole or recess portions 2. The construction of Figures 4(a) and 4(b) has a higher reliability than the construction of Figures 1 to 3 from the standpoint of supplying an ink jet to a nozzle, whereby a mechanical construction for aligning a hole or recess portion 2 and the thermal head element 4 is not necessary and the construction is greatly simplified. Several of the hole or recess portions 2 are definitely located on the thermal head element 4 at a given time and skips in recording are completely eliminated. Figure 5 shows a monochrome type line printer. The film 1 is an endless belt whose width is the full width of a page, for example A4 or A3 width. A plurality of hole or recess portions 2 are shaped in or on the film 1. The diameter of the hole or recess portions 2 depends on said film thickness. For example, the maximum diameter might be 50Um in the case of a film thickness of 50pom. Numeral 8 indicates a recording ink, and numeral 7 indicates an ink tank. The film 1 is rotatably supported by a pair of rollers 9 and 15. Recording ink 8 is transferred into the hole or recess portions 2 when the film 1 passes through the ink tank 8 and is moved past the thermal head element 4 by rotation of the rollers 9 and 15. At this time, a bubble (corresponding to the bubble 6 of Figure 2 (b) and 2(c)) may be caused between said thermal head element 4 and recording ink 8 by quickly heating the thermal head element 4 by electric voltage application thereto by means not shown, the thermal head element 4 being disposed in contact with one surface la of the film 1. The recording ink 8 is therefore spouted or ejected from the holes 2 onto a recording paper 11 by the bubble pressure, whereby a character or image may be recorded on the paper 11, the latter being disposed adjacent to the opposite surface lb of the film 1. The thermal head member 5 of Figure 5 has a plurality of thermal head elements 4 extending in the breadth direction of the thermal head member 5 (i.e. transversely of the paper 11) and has a driving circuit (not shown) which drives or energises selected thermal head elements 4, whereby the driving circuit construction is simplified. The recording paper 11 may be located on a platen 13 adjacent the hole or recess portions 2. The recording paper 11 is supported by a pair of rollers 12 and 14 which are attached to the platen 13. Numeral 10 indicates a blade to scrape off excess ink which adheres to the film 1 after passing through an ink tank 8. Printing on the recording paper 11 is performed by selectively applying an electric voltage to the thermal head elements 4 from the driving circuit which may, for example, be constructed using an integrated circuit (not shown). Figure 6 shows a construction for colour line printing function, a basic construction composed of a plurality of mechanisms for each colour source which may be basically similar to the monochrome mechanism of Figure 5. A film ly and a recording ink 8y are used for Yellow, a film lm and a recording ink 8m are used for Magenta, a film lc and a recording ink Sc for Cyan and a film lblk and recording ink 8blk for Black. The thermal head member 5 has a plurality of thermal head elements 4 (not shown in Figure 6) located behind each of the films ly, lm, lc and Ibis. The recording inks 8y, 8m, 8c and 8blk are selectively spouted or ejected from the films ly, lm, lc and lblk onto the recording paper 11 by driving the thermal head elements 4 according to a timing signal from a driving circuit (not shown) while feeding the recording paper 11 in a coordinated manner. That is to say, the films ly, lm, lc, lblk have portions ld, le, lf, 1g respectively which are arranged successively in a length direction or direction of travel of the paper 11, each portion ld, le, If, lg being provided with respective thermal head elements 4 (not shown in Figure 6). Figure 7 shows a construction of a colour serial printing machine having films ly, lm, lc and lblk for Yellow, Magenta, Cyan and Black respectively; the films have a plurality of hole or recess portions 2 respectively. The films ly, lm, lc, lblk respectively have portions lh, li, lk, ln disposed adjacent the paper 11 and arranged successively in the breadth direction of the latter. The thermal head members 4y, 4m, 4c and 4blk for Yellow, Magenta, Cyan and Black, have their thermal head elements aligned across the width of the films ly, lm, ic and lblk respectively. Ink supply sponge rollers 16y, 16m, 16c and 16blk supply the recording ink from the ink tanks 7y, 7m, 7c and 7blk to the films ly, lm, ic and Ibis. Sponge rollers 16y, 16m, 16c and 16blk suck up the recording ink from said ink tanks 7y, 7m, 7c and 7blk and fill the recording ink in the hole or recess portions 2 which contact and pass the surfaces of the sponge rollers l6, 16m, 16c and 16blk. The films l:L to Talk, the thermal head members ty to 4blk, the sponge rollers 16y to 16blk and the ink tanks 7y to 7blk are compactly housed as a unitary colour reproducing head body, whereby it is possible to obtain a colour serial print system by reciprocating the colour recording head body across the width of the recording paper 11. Figure 8 shows a cross-sectional view of typical hole or recess portions 2 of the film 1. a and c are tapered portions, b is a parallel portion and d is a recess portion. The density of said hole or recess portions 2 in the film 1 is determined by both the recording density and thermal head element density. It is possible to make both monochrome and colour line and serial printers according to the present invention. It is also possible to completely eliminate ink jet stoppages by employing the hole or recess portions as the ink jet nozzles. Further, it is possible to obtain a higher recording density than conventional ink jet printers because many holes and recesses are shaped in the film and are shaped in one thermal head element of the thermal head member. The bubble pressure employed to spout the recording ink from the hole or recess portions to the recording paper is much higher than a conventional piezo electric element type ink jet nozzle. In the above embodiments of the present invention, the film employed is endless; however, the present invention is not limited in this construction. For example, it is possible to use another type of reciprocating film. Further, it is possible to make the ink tank and film as a cassette type unit, which may be readily replaced as required.

Claims: CL A I M S 1. A thermal ink jet printer characterised by an apertured member (1) having at least one hole or recess (2) therein; means (7,9,15) for introducing ink (8) into the or each hole or recess (2); at least one thermal head element (4) disposed in contact with one surface (la) of said apertured member (1), the or each said thermal head element (4) being aligned or alignable with at least one said hole or recess (2); means (12,13,14) for mounting paper or other recording medium (11) adjacent to the opposite surface of the apertured member (1); and means for energising the or a thermal head element (4) when so aligned so as to cause the ink (8) to be ejected from the respective said at least one hole or recess (2) and onto the recording medium (11) as a result of bubble pressure caused by heat from said thermal head element (4). 2. A printer as claimed in claim 1 characterised in that the apertured member is an endless belt (1) having a plurality of holes or recesses (2) therein, the endless belt (1) being arranged to receive ink from an ink tank (7). 3. A printer as claimed in claim 2 characterised in that the endless belt is constituted by a film (1) having holes or recesses (2) therein each of which has a diameter of 10 to 200us. 4. A printer as claimed in any preceding claim characterised in that the or each thermal head element (4), when so arranged, causes ink ejection from one hole or recess (2) only. 5. A printer as claimed in any of claims 1-3 characterised in that the or each thermal head element (4), when so energised, causes ink ejection from a plurality of holes or recesses (2) simultaneously. 6. A printer as claimed in any preceding claim characterised in that there are a plurality of thermal head elements (4) which are arranged transversely of the recording medium (11), the energising means being arranged to energise selected thermal head elements (4). 7. A printer as claimed in claim 2 or 3, or in any of claims 4-6 when dependent on claim 2 or 3, characterised in that there are a plurality of endless belts (ly, lm, Ic, Iblk) and respective ink tanks (B , 8m, 8c, 8blk), the ink tanks (8y, Sm, 8c, 8blk) being adapted to receive inks of different colours. 8. A printer as claimed in claim 7 characterised in that each endless belt (ly, Im, lc, lblk) has a portion (ld, le, lf, 1g) disposed adjacent the recording medium (11), the said portions being arranged successively in a length direction or direction of travel of the recording medium (11), each said portion being provided with respective thermal head elements (4). 9. A printer as claimed in any preceding claim characterised in that the or each endless belt is mounted on rollers (9,15) one of which (9) is disposed within the respective ink tank (7). 10. A printer as claimed in claim 7 characterised in that each endless belt (ly, Im, lc, lblk) has a portion (lh, li, lk, ln) disposed adjacent the recording mediun (11), the said portions being arranged successively in the breadth direction of the recording medium (11), each said portion being provided with a respective thermal head element (4y, 4m, 4c, 4blk). 11. A printer as claimed in claim 10 characterised in that each endless belt (ly, lm, lc, Iblk) is entrained around a respective sponge roller (16y, 16m, 16c, 16blk) which extends into a respective ink tank (7y, 7m, 7c, 7blk).

Inventors: HORI, KEIICHI
Applicants: ELM CORPORATION, FUJITSU LIMITED, HITACHI KOKI CO., LTD., MITSUBISHI ELECTRIC CORPORATION, TOSHIBA CORPORATION
Application year: 1985
Main classification: B41J3
IPC codes: B41J2