EP0289115A1 - Elektrothermisches Transfer-Druckgerät - Google Patents

Elektrothermisches Transfer-Druckgerät Download PDF

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Publication number
EP0289115A1
EP0289115A1 EP19880301800 EP88301800A EP0289115A1 EP 0289115 A1 EP0289115 A1 EP 0289115A1 EP 19880301800 EP19880301800 EP 19880301800 EP 88301800 A EP88301800 A EP 88301800A EP 0289115 A1 EP0289115 A1 EP 0289115A1
Authority
EP
European Patent Office
Prior art keywords
ribbon
ink
current
terized
charac
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP19880301800
Other languages
English (en)
French (fr)
Inventor
Hitoshi Nagato
Tadayoshi Ohno
Tsutomu Kanai
Akito Iwamoto
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Toshiba Corp
Original Assignee
Toshiba Corp
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Priority claimed from JP4515087A external-priority patent/JPS63212565A/ja
Priority claimed from JP13767587A external-priority patent/JPS63302075A/ja
Priority claimed from JP18698187A external-priority patent/JP2538932B2/ja
Priority claimed from JP18763087A external-priority patent/JPS6431657A/ja
Priority claimed from JP19140987A external-priority patent/JPS6434759A/ja
Application filed by Toshiba Corp filed Critical Toshiba Corp
Publication of EP0289115A1 publication Critical patent/EP0289115A1/de
Withdrawn legal-status Critical Current

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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
    • B41J—TYPEWRITERS; SELECTIVE PRINTING MECHANISMS, i.e. MECHANISMS PRINTING OTHERWISE THAN FROM A FORME; CORRECTION OF TYPOGRAPHICAL ERRORS
    • B41J2/00—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed
    • B41J2/315—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed characterised by selective application of heat to a heat sensitive printing or impression-transfer material
    • B41J2/32—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed characterised by selective application of heat to a heat sensitive printing or impression-transfer material using thermal heads
    • B41J2/325—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed characterised by selective application of heat to a heat sensitive printing or impression-transfer material using thermal heads by selective transfer of ink from ink carrier, e.g. from ink ribbon or sheet

Definitions

  • This invention relates to an apparatus for trans­ferring ink from an ink ribbon to a recording medium, by applying heat to the medium, thereby recording data on the recording medium, and more particularly, to a so-called "thermal recording printer.”
  • An apparatus generally known as a "thermal recording printer” transfers ink from an ink ribbon to a recording medium, by heating the ink ribbon and thereby melting the ink.
  • the printer can print data on sheets of ordinary paper, without making much noise, and can operate very reliably.
  • the thermal recording printer is used as hard copy printers for use in various OA (Office Automation) apparatuses such as personal computers, word possessors, and color printers.
  • the thermal recording printer is disadvantageous in two respects. First, the ink ribbon is liable to be cut during use. Secondly, the printer cannot print data in sufficient quality, on sheets of coarsely textured paper such as PPC paper or bond paper.
  • Fig. 1 is a schematic view showing an electro­thermal printer of the known type.
  • ink ribbon 1 comprised of electrically resistive base film 2, electrically conductive layer 3 made of aluminum, and solid ink layer 4 coated on conductive layer 3.
  • Ink layer 4 will melt, soften, or sublime when heated.
  • Ink ribbon 1 is fed in the direc­tion of arrow A by means of a ribbon-feeding mechanism (not shown).
  • the electrothermal printer comprises data-recording electrodes 5, signal-generating circuit 6, and return electrode 7. Electrodes 5 are pin-shaped and arranged parallel to one another. They can be moved in the direction of arrow C, and are electrically coupled with signal-generating circuit 6. Return electrode 7, which is moved along with electrode 5, is connected to the ground and located downstream of the ribbon-feeding direction (arrow A). Return elec­trode 7 is coupled to follow roller 8 by the ribbon-­feeding mechanism.
  • follow roller 8 contacts ink ribbon 1; it is rotated as the mechanism feeds ink ribbon 1 in the direction of arrow A.
  • signal-generating circuit 6 supplies data signals to data-recording electrodes 5.
  • Electrodes 5 supply ink ribbon 1 with the currents corresponding to the data signals. These currents (hereinafter referred to as “data currents”) flows through resistive base film 2 into conductive layer 3, and flow from layer 3 to return electrode 7 through resistive base film 2, as is shown by arrow B.
  • data currents flows through resistive base film 2 into conductive layer 3, and flow from layer 3 to return electrode 7 through resistive base film 2, as is shown by arrow B.
  • Joule heat is generated in the limited portions of ink ribbon 1 which are located below electrodes 5.
  • These portions of ribbon 1 are heated to 200°C or more, whereby those portions of ink layer 4 which are on these portions of ribbon 1 are softened or melted. As a result, the ink is transferred from ribbon 1 onto recording paper 9.
  • the data currents also flow to return electrode 7 through resistive base film 2, and change into Joule heat.
  • This heat is not suf­ficient to melt or soften solid ink layer 4, since that surface of return electrode 7 which contacts the ribbon 1 is much larger than that surface of each data-­recording electrode 5 which contacts ribbon 1.
  • return electrode 7 does not operate to transfer ink onto recording paper 9.
  • Data-recording electrodes 5 are moved, along with return electrode 7, in the direction of arrow C. While electrodes 5 are thus moved, they supply data currents to ink ribbon 1, in response to the data signals output from signal-generating circuit 6. Therefore, the ink is continuously transferred from ribbon 1 onto recording paper 9, whereby data, such as images and characters, are reproduced on recording paper 9.
  • ink ribbon 1 As has been described, it is within ink ribbon 1 that heat is generated within ink ribbon 1 during the use of the thermal recording printer. Thus, the heat is fast transmitted to solid ink layer 4, and the printer can record data on paper at a speed higher than ordinary thermal printers having a thermal head which applies heat to an ink ribbon. Since heat is generated within ink ribbon 1, it is applied in its entirety to solid ink layer 6, thus heating layer 6 to a high tem­perature.
  • solid ink layer 4 can be made of material having a high melting point or a high sublima­tion point.
  • Resistive ink ribbon 1 is made of three layers, and is more difficult to manufacture and, hence, more expen­sive than the ink ribbon for use in the ordinary thermal printers, which is comprised of two layers, i.e., an electrically resistive base film and a solid ink layer.
  • Another drawback inherent in the resistive thermal printer is that each portion of ink ribbon 1 required for printing one line of characters cannot be shorter than the line of characters, and the running cost of the printer is, thus, relatively high.
  • the data currents applied to ink ribbon 1 change into Joule heat in those portions of solid ink layer 4 which are located below electrode 5. Since ribbon 1 is fed slowly, a great amount of heat is gener­ated in these portions of ink layer 4. Those portions of conductive layer 3 and base film 2 which receive this heat are heated to 200°C or more. As a result, the heated portions of layer 3 may be oxidized or cracked, and the heated portions of base film 2 may shrink. If this happens, all conductive layer 3 rendered almost non-­conductive, except for both lateral edges which are not located under electrodes 5. The data currents flow con­centratedly through the thin lateral edges of conductive layer 3 into that portion of base film 2 which contacts return electrode 7.
  • ink ribbon 1 is cut at such a soften­ed portion of base film 2, overcome by the tension which is applied on that portion of ribbon 1 which extends between data-recording electrodes 5, on the one hand, and return electrode 7, on the other. Moreover, ribbon 1 may be adhered to follow roller 8 by the remaining ink layer 4, now softened and thus viscous, and it may eventually taken up around roller 8. In the worst case, it may be cut at a shrinked portion of base film 2, which is positioned between roller 8 and electrodes 5.
  • the first cause is the electrical resistance of conductive layer 3 of ink ribbon 1 (See Fig. 1) Since the resistance of conductive layer 3 is far lower than that of resistive base film 1, the currents applied from data-recording electrodes 5 to ribbon 1 flow through layer 3 to return electrode 7, as is represented by arrow B in Fig. 1.
  • the second cause of the cutting of the ink ribbon is the heat generated in those portions of solid ink layer 4 which are located below data-recording electrodes 5, in order to record data on recording paper 9.
  • the heat generated in solid ink layer 4 destroys conductive layer 3 or renders layer 3 more electrically resistant.
  • the currents applied from data-­recording electrodes 5 flows from ribbon 1 to return electrode 7, concentratedly through narrow undestroyed or low-resistant portions of conductive layer 3. Consequently, a great amount of heat is generated in these narrow portions of layer 3, inevitably softening that portion of base film 2 which lies above the undestroyed or low-resistant portions of layer 3.
  • the softened portion of base film 2 cannot withstand the tension applied on that portion of ribbon 1 which extends between electrodes 5 and return electrode 7. As a result, ink ribbon 1 is cut in the vicinity of return electrode 7.
  • a resistance thermal recording apparatus comprising: an ink ribbon including a base film being elec­trically resistive and having two opposing surfaces, a conductive layer formed on the first surface of the base film, and an ink layer formed on the conduc­tive layer, having a surface to face and contact the recording medium, and being able to be transferred onto the recording medium when heated; ribbon-feeding means for feeding said ink ribbon in a first direction; current-supplying means contacting the second sur­face of the base film for supplying a signal current to the conductive layer through the base film, thereby to generate heat in the base film, said heat being trans­ferred to the ink layer through the conductive layer, thereby to transfer ink to the recording medium; and current-collecting means located upstream of said first direction with respect to said current-supplying means, and being movable to contact the second surface of the base film, for collecting the signal current supplied from said current-supplying means to the con­ductive layer.
  • the return electrode Since the return electrode is located on the ribbon-feeding side, no heat is generated in any portion of the ink ribbon which has passed the data-recording electrodes and reaches the ribbon take-up side. There­fore, the used portion of the ink ribbon is gradually cooled as it is fed to the follow roller. The solid ink layer remaining on the used portion of the ribbon is no longer viscous when it reaches the follow roller, and there is not risk that the ribbon is wrapped around the roller. Thus, the cutting of the ink ribbon is pre­vented.
  • Fig. 2 is a perspective view showing a serial thermal, or an electrothermal recording apparatus according to an embodiment of the present invention.
  • This serial printer has recording head 11 which is illustrated in detail in Fig. 3.
  • Recording head 11 is opposed to platen 14. It has 50 data-recording elec­trodes 30, as is shown in Fig. 3.
  • These data-recording electrodes 30 are arranged parallel to one another such that their tips are aligned in a vertical line extending at right angels to the direction in which ink ribbon 16 is fed, in the density of 12 electrodes per millimeter.
  • These recording electrodes 30 are provided within housing 32 made of plastics. Their tips are connected to silicone rubber layer 11A attached to head-supporting section of housing 32.
  • the proximal ends of electrodes 30 are electrically connected to conductive pads 11D formed on polyimide film 11B by means of conductive patterns 11C formed also on polyimide film 11B which in turn is formed on side of housing 32.
  • recording head 11 is detachably supported by head holders 12 and 13.
  • the conductive pads 11D are automatically connected to the conductive pads (not shown) of head holder 12. Since the conductive pads of head holder 12 are coupled to signal-generating circuit 31 shown in Fig. 4, conductive pads 11D are electrically connected to signal-generating circuit 31.
  • Recording head 11 and head holders 12 and 13 con­stitute head assembly 10.
  • head assembly 10 is pressed onto paper 27 by head-urging means (not shown). Head assembly 10 is released from paper 27 upon recording data on paper 27.
  • the force for pressing head assembly 10 onto paper 27 is appropriately controlled. This is because ink traces will be formed on paper 27, extending from each printed character, when this force is greater than necessary.
  • Return electrode 15 is located upstream of the ribbon-feeding direction, with respect to head assembly 10. In other words, return electrode 15 is located to contact the unused portion of ink ribbon 16.
  • Ink ribbon 16 is contained in ribbon cassette 20, in the form of a roll.
  • ink ribbon 16 is comprised of electrically resistive base film 32, electrically conductive layer 33 formed on resistive layer 32, and solid ink layer 34 coated on conductive layer 33.
  • Resistive base film 32 has a thickness of about 16 ⁇ m and is made of polycarbonate containing carbon particles dispersed therein.
  • Conductive layer 33 is an aluminum film vapor-deposited on base film 32 and has a thickness of about 0.1 ⁇ m. Solid ink layer 34 will be melted when heated to a certain temperature, its thickness is about 6 ⁇ m.
  • a pair of pinch rollers 21 and 22 are located downstream of the ribbon-freeing direction, with respect to head assembly 10. These pinch rollers 21 and 22 constitute a ribbon-feeding mechanism.
  • Head assembly 10, return electrode 15, ribbon cassette 20, and the ribbon-feeding mechanism (21, 22) are mounted on carriage 23.
  • Carriage 23 is slidably mounted on guide bar 24 which horizontally extends and is parallel to platen 14.
  • Carriage 23 is connected to timing belt 26.
  • Timing belt 26 is stretched between a pulley (not shown) provided in the left end section of the serial thermal printer, and the pulley fastened to the shaft of carriage-driving motor 25 provided in the right-end section of the printer. Since timing belt 26 is wrapped around both pulleys, carriage 23 is moved to the left or right, along platen 14, when the shaft of motor 25 rotates in one direction or the other.
  • Platen-driving motor 28 is provided in the right-­end section of the serial thermal printer. A pulley is fastened to the shaft of this motor 28. Timing belt 29 is stretched between, and wrapped around, this pulley and the pulley connected to the right end of platen 14. When motor 28 rotates in one direction or the other, platen 14 is rotated to feed paper 27 forward or back­ward. Paper 27 is, for example PPC paper having.
  • carriage 23 When the power-supply switch (not shown) of the printer is turned on, carriage 23 is automatically moved to its home position, i.e., to the left end of guide bar 24. Carriage 23 is moved from the home position to the print-start position when motor 25 drives timing belt 26 in response to a print-start signal supplied from a drive signal-generating circuit (not shown). In the meantime, the head-urging mechanism presses recording head 11 and paper 27, with ink ribbon 16 interposed between head 11 and paper 27. Hence, paper 27 is pressed onto platen 14. In this condition, head 11 can print data on paper 27. After carriage 23 has moved to the print-start position, signal-generating circuit 31 (Fig.
  • recording head 11 faces paper 27.
  • Ink ribbon 16 is interposed between paper 27 and data-recording electrodes 30.
  • Electrodes 30 are moved in the direction of arrow C as carriage 23 is driven in the same direction.
  • Data-recording electrodes 30 remain in contact with resistive base film 32 of ribbon 16 while being thus moved.
  • data signals are supplied to elec­trodes 30 from signal-generating circuit 31 via conduc­tive pads 11D and conductive patterns 11c, data currents corresponding to these signals flow from electrodes 30 to base film 32. These currents flow through those portions of base film 32 which contact electrodes 30, whereby Joule heat is generated in these portions of film 32.
  • the heat is transferred via conductive layer 33 to those portions of solid ink layer 34 which opposes the heat-­generating portions of base film 32. These portions of ink layer 34, therefore, melt into ink drops. The ink drops stick onto paper 27, whereby data is printed thereon.
  • return electrode 15 is located upstream of the ribbon-feeding direction (arrow A in Fig. 4), with respect to head assembly 10. In other words, return electrode 15 contacts the unused portion of ink ribbon 16. Thus, it is through the con­ductive layer 33 of the unused portion of ribbon 16 that the data currents flow from the heat-generating portions of base film 32 to return electrode 15.
  • the conductive layer 33 of the unused portion of ribbon 16 is neither oxidized nor cracked, it conducts the data currents very well and generates no heat great enough to soften base film 32 or ink layer 34.
  • ink ribbon 16 is not cut even if it is fed more slowly than data-recording electrodes 30 are moved, in order to accomplish a high-­speed recording of data.
  • the serial electrothermal printer shown in Fig. 2 can, thus, record data at high speed.
  • Fig. 5A illustrates how data currents flow to the return electrode, while the thermal printer of this invention (Fig. 2) is printing characters
  • Fig. 5B shows how data current flow to the return electrode, while the conventional thermal printer (Fig. 1) is printing characters.
  • numeral 35 designates a recording head having a plurality of data-­recording electrodes
  • numeral 36 denotes a return electrode
  • numeral 37 represents a resistive ink ribbon
  • arrows 38 denote data currents.
  • recording head 35 and return electrode 36 are fixed, and ink ribbon 37 is fed in the direction of arrow A, whereby head 35 prints letters "H" one after another.
  • the conductive layer of the used portion of ribbon 37 is oxidized or cracked due to the heat generated in those portions of the resistive base film which contacts the data-recording electrodes of head 35, except for the lateral edges.
  • the oxidized or cracked portion of the conductive layer is far less electrically conductive than the undestroyed lateral edges of the conductive layer. Further, the resistive base film has become mechanically weak, except for its lateral edges.
  • the data currents supplied from the data-recording electrodes to ink ribbon 37 cannot flow to return electrode 36 through the conduc­tive layer of the used portion of ribbon 37, under the same condition.
  • the ink dots printed on the paper by softening or melting those portions of the solid ink layer which face the data-recording electrodes, respec­tively, have different densities, resulting in an insuf­ficient printing quality.
  • the ink dots transferred from the center portion of ink ribbon 37 are not as dense as required.
  • data currents 38 flows to return electrode 36 through the conductive layer of the unused portion of ink ribbon 37, as is shown in Fig. 5A.
  • return electrode 36 is located upstream of the ribbon-feeding direction A, with respect to recording head 35.
  • the conductive layer of the unused por­tion of ribbon 37 is neither oxidized nor cracked, data currents 38 flow through the entire section of the con­ductive layer.
  • heat, if generated in the conduc­tive layer is not great enough to noticeably reduce the mechanical strength of the base film of ribbon 37.
  • the data currents supplied from the data-­recording electrodes to ink ribbon 37 flow to electrode 36 through the conductive layer under the same condition, the ink dots printed on the paper have the same density, which ensures a satisfactory printing quality.
  • the ink dots printed on the paper by applying data currents to the ribbon from the data-recording electrodes had different densities when the ribbon was fed at the speed 1/1.1 times the speed of moving the data-recording electrodes, and the ink ribbon was cut when it was fed at half the speed of moving the data-recording electrodes.
  • data could be printed in a sufficiently quality even when the ink ribbon was fed at one-tenth of the speed of moving the data-recording electrodes, and the ribbon was not cut when the ribbon-feeding speed was reduced to 0.05 or less of the speed of moving the data-recording electrodes. Furthermore, in the printer of this invention, neither the printing quality was insufficient, not the ink ribbon was cut, when the data-­recording speed was raised to 15 in/sec, as when this speed was 6 in/sec. In addition, this increase of the data-recording speed did not result in a decrease of the use efficiency of the resistive ink ribbon.
  • Fig. 6 shows the data-recording section of the first example of the serial thermal printer.
  • ribbon guide 42 is used in place of the return electrode 15 (Figs. 2 and 4).
  • Ribbon guide 42 which is made of electrically conductive material such as a metal, is mounted on one side of head assembly 10.
  • Guide 42 is electrically insulated from recording head 11 and elec­trically connected by means of wire 46 to carriage 23 (Fig. 2) which is set at ground potential. Therefore, ribbon guide 42 functions as a return electrode.
  • a pair of pinch rollers 21 and 22, which are located downstream of the ribbon-feeding direction (arrow A), are not con­nected to carriage 23. Hence, no electric currents can flow into roller 21 or 22 even if these rollers are made of electrically conductive material.
  • roller 21 nor roller 22 functions an electrode; they do nothing but feed the ink ribbon in the direction of arrow A.
  • Fig. 7 shows the data-recording section of the second example of the serial thermal printer according to the present invention.
  • This example is identical to the first example (Fig. 6), except that head holder 13 is coupled to carriage 23 (Fig. 2) which is set at the ground potential.
  • Both ribbon guide 42 and head holder 13 are made of electrically conductive material, and are connected to each other, thus forming a return electrode.
  • ribbon guide 42 need not be coupled to carriage 23 by means of wire 46 as in the first example.
  • Head holder 13 and ribbon guide 42 can be integrally formed of the same electrically conductive material.
  • Fig. 8 illustrates the data-recording section of the third example of the serial thermal printer.
  • the third example is characterized by ribbon-guiding roller 40 which is located upstream of the ribbon-feeding direction (arrow A), with respect to head assembly 10, and contacts the resistive base film of ink ribbon 16.
  • This roller 40 is made of electrically conductive material and is set at the ground potential, and there­fore functions as a return electrode.
  • Fig. 9 shows the data-recording section of the fourth example of the serial thermal printer according to the invention.
  • the contact resistance between ribbon-guiding roller 40 (or the return electrode) and the resistive base film of ink ribbon 16 greatly changes as ribbon 16, which is being fed toward head assembly 10, inevitably vibrates.
  • this contact resistance increases too much, the data currents flowing from those portions of the base film which contact the data-recording electrodes of head 11 to that portion of the base film which contacts roller 40 through the conductive layer of ribbon 16 fail to effectively flow into roller 40.
  • the ink dots printed on the paper 27 may have different densities, resulting in an unsatisfactory printing quality, or excessive heat may be generated in that portion of the base film which contacts roller 40, thereby softening this portion of the film, and thus causing the cutting of ink ribbon 16.
  • the fourth example has two return electrodes. More specifically, as is shown in Fig. 9, ribbon-guiding roller 40 identical to the one used in the third example (Fig. 8) is used as the first return electrode, and ribbon guide 42 identical to the one used in the first example (Fig. 6) is used as the second return electrode.
  • ribbon-guiding roller 40 identical to the one used in the third example (Fig. 8) is used as the first return electrode
  • ribbon guide 42 identical to the one used in the first example (Fig. 6) is used as the second return electrode.
  • Fig. 10A shows ribbon guide 42 used in the first, second, third and fourth examples -- all described with reference to Fig. 6 through Fig. 9.
  • ribbon guide 42 has sloping surface 42A and two lateral edges 42B.
  • Ink ribbon 16 is guided, sliding on sloping surface 42A and being prevented by lateral edges 42B from slipping off sloping surface 42A.
  • it is necessary to reduce the changes in the contact resistance between surface 42A and the base film of ribbon 16, as much as possible, thereby to accomplish a high-quality printing and to prevent the cutting of ribbon 16.
  • Figs. 10B and 10C show two modifications of ribbon guide 42, which are designed to minimize the contact resistance between sloping surface 42A and the base film of ink ribbon 16.
  • the modified guide 42 shown in Fig. 10B includes electrically conductive fabric 44 ad­hered to sloping surface 42A. Since it is this fabric 44 that the base film contacts as ribbon 16 is guided by ribbon guide 42, the changes in the contact resistance can be reduced.
  • the modified guide 42 shown in Fig. 10C includes electrically conductive leaf spring 43 attached to sloping surface 42A. Spring 43 also reduces the changes in the contact resistance be­tween ribbon guide 42 and the base film of ink ribbon 16.
  • ribbon guide 42 shown in Fig. 10A When ribbon guide 42 shown in Fig. 10A is used as a return electrode, the entire sloping surface 42A must be made of electrically conductive material. When the ribbon guide shown in Fig. 10B or 10C is used as a return electrode, it suffices if only that portion of sloping surface 42A to which leaf spring 43 or fabric 44 is attached.
  • Fig. 11A shows ribbon-guiding roller 40 used in the first, second, third and fourth examples which are shown in Figs. 6 to 9.
  • roller 40 has a smooth circumference. As has been discussed, it is required to minimize the changes in the contact resistance between roller 40 and the base film of ink ribbon 16.
  • Figs. 11B and 11C show two modifications of ribbon-guiding roller 40, which are designed to reduce the changes in this contact resistance.
  • the modified roller shown in Fig. 11B has fabric filaments 45 protruding from the circumference of the roller.
  • the modified roller shown in Fig. 11C has protrusions 46 formed on the circumference of the roller. Filaments 45 and protrusions 46 are electrically conductive. There­fore, they serve to reduce the changes in the contact resistance between the roller and the base film of ribbon 16.
  • the serial thermal printer shown in Figs. 2 and 4 is characterized in that the return electrode is located upstream of the ribbon-­feeding direction, with respect to the data-recording electrodes, and thus contacts the unused ink ribbon. Therefore, it is through the undestroyed portion of the conductive layer that the data currents flow from the data-recording electrodes to the return electrode. Hence, the data currents can be sufficiently large, and they can flow from the data-recording electrodes under the same condition. Further, no currents flow through the used portion of the ribbon, which is mechanically weak, to heat this portion so as to reduce the mechani­cal strength thereof.
  • the printer can record data at high speed, while efficiently using the ink ribbon.
  • the present invention can be applied to a line thermal printer, in which case the data currents flow from the numerous data-recording electrodes of the line print head to a return electrode through the unused por­tion of a resistive ink ribbon under the same condition. Therefore, the line thermal printer can print data in high quality, and can also use the ink ribbon with high efficiency.
  • Fig. 12 is a diagram schematically showing a line thermal printer according to the invention.
  • This printer has line print head 11, platen 14, return electrode 15, follow roller 40, and ribbon-feeding mechanism 41.
  • Head 11 has a number of data-recording electrodes (not shown) arranged in a line extending parallel to platen 14.
  • a head-urging means presses head 11 onto platen 14 such that resistive ink ribbon 16 is interposed between head 11 and paper 27 wrapped around platen 14, not staining paper 27 with ink, and being able to be fed.
  • Return electrode 15 is a rotatable roll bar made of a metal and connected to the ground. Electrode 15 and follow roller 40 pinches ink ribbon 16.
  • Ribbon-feeding mechanism 41 comprises a pair of pinch rollers and a stepper motor (not shown).
  • the stepper motor rotates one of the pinch rollers, thereby to feed ink ribbon 16.
  • Ink ribbon 16 can be fed by ribbon-feeding mechanism 41, and is controlled by brake mechanism 48 which controls the rotation of ribbon-feeding reel 47. Ribbon 16 is, thus, moved independently of recording paper 27.
  • Sheets of rec­ording paper 27 are stored in cassette 49.
  • Paper-­feeding roller 50 contacts the upper most sheet stored in cassette 49, and hence feeds sheets 27 from cassette 49 toward platen 14, as it is rotated by a drive means (not shown).
  • Each sheet 27 fed from cassette 49 is wound around platen 14 and fed further as platen 14 is rotated. The sheet 27 is thus eventually come into contact with ink ribbon 16, which in turn contact the tips of data-recording electrodes of line print head 11.
  • return electrode 15 of this line thermal printer is located also upstream of the ribbon-feeding direction, with respect to the data-recording electrodes of head 11, and thus contacts the unused portion of ink ribbon 16. Therefore, the line thermal printer achieves the same advantages as the serial thermal printer shown in Figs. 2 and 4.
  • the serial thermal printer shown in Fig. 13 com­prises a first pair of follow rollers 21, 22 and a second pair of follow rollers 15 and 51, both pairs being arranged in the path of ink ribbon 16.
  • follow rollers 21, 22, 15, and 51, and motors (not shown) con­stitute ribbon-feeding mechanism which can feed ribbon 16 forward and backward, so that ink ribbon 16 can be repeatedly used to print data.
  • the solid ink layer 34 of ribbon 16 is rather thick, for example 10 ⁇ m, so that image data can be recorded in the density of 1.2.
  • follow rollers 21 and 15 are connected to the ground, and thus function as return electrodes.
  • follow roller 21 is moved out of contact with ink ribbon 16 as is shown in Fig. 13, whereas follow rollers 15 and 51 contact ribbon 16. Conversely, to feed ribbon 16 backward, in the direction of arrow A-2, follow roller 15 is moved out of contact with ribbon 16, whereas follow rollers 21 and 22 contact ink ribbon 16.
  • follow rollers 21 and 15, both functioning as return electrodes, are engaged with, or disengaged from, ink ribbon 16 by means of a cam-clutch mechanism of the known type (not shown).
  • ink ribbon 16 is fed in the direction of arrow A-1, while recording head 11 is moved in the direction of arrow A-2, whereby a first one line of data is printed on recording paper (not shown).
  • carriage 23 reaches the rightmost printing position, recording head 11 is moved away from platen 14 by means of the head-urging means.
  • platen-driving motor 28 (Fig. 2) rotates platen 14, thereby feeding paper 27 forward by one line-­space distance.
  • recording head 11 is pressed onto platen 14 by the head-urging means.
  • follow roller 21 i.e., the return electrode
  • follow roller 22 i.e., the other return electrode
  • carriage 23 is moved in the direction of arrow A-1, while data signals are being supplied from signal-­generating circuit 31 to head 11 in the order reverse to the order in which the data signals have been supplied to head 11 during the printing of the first line.
  • reel 23A is rotated by the reel-­driving motor (not shown) now coupled to reel 23A by means of a one-way clutch (not shown, either).
  • ink ribbon 16 is taken up around reel 23A at the same speed carriage 23 moves to the leftmost printing position.
  • carriage 23 reaches the leftmost printing position, the printing of the second line is completed.
  • recording head 11 is moved away from platen 14. Platen 14 is rotated, thus feeding recording paper 27 forward by one line-space distance. While paper 27 is being fed forward, ribbon reel 23B is rotated, taking up 18 mm of ink ribbon 16.
  • the serial thermal printer shown in Fig. 13 can print data even on coarsely textured paper such as PPC paper, at the speed of 60 cps (character per second) in the high density of 12 dots/mm. Since this printer can print data in either direction, that is, from the left to right, and from the right to the left, the time required to print the same amount of data is half the time required by the conventional serial thermal printer which cannot print data in either direction.
  • This printer comprises ribbon-feeding reel 56, a pair of ribbon-guiding rollers 57A and 57B, and ribbon take-up reel 58. Back tension is applied on ribbon-feeding reel 56, so that resistive ink ribbon 16 does not slacken between recording head 11 and ribbon take-up reel 58. Ribbon take-up reel 58 is controlled by a reel control mechanism (not shown).
  • carriage 23 is moved in the direction of arrow A-1, thus printing data.
  • resistive ink ribbon 16 is not moved, in which respect this printer is different from the printer shown in Fig. 15.
  • carriage 23 reaches the rightmost printing position, recording head 11 is moved away from platen 14, and platen 14 is rotated, thus feeding paper 27 forward by one line-space distance. Then, head 11 is pressed toward platen 14, whereby ink ribbon 16 and recording paper 27 are pinched between head 11 and platen 14.
  • return electrode 21 is moved away from ink ribbon 16, and return electrode 15, which is located downstream of head-moving direction A-2, with respect to head 11, is put into contact with ink ribbon 16. In this condition, carriage 23 is moved in the direction of arrow A-2, thereby printing the second line of data on recording paper 27.
  • carriage 23 is moved repeated between the leftmost and rightmost printing positions, until recording head 11 prints ten lines of data.
  • the reel control mechanism drives ribbon take-up reel 58, whereby the next unused portion of ribbon 16, which is as long as one line of data, is fed from ribbon-feeding reel 26, while the used portion of the same length is taken up around reel 28. Namely, whenever the same portion of ink ribbon 16 has been used a predetermined number of time, this portion is taken up around ribbon take-up reel 28, while the used portion of the ribbon, which has the same length, is fed from ribbon-feeding reel 56.
  • FIG. 13 and 15 each have two return electrodes which are set far apart from each other.
  • the return electrodes can be located close to each other, in accordance with the present invention.
  • FIG. 16 schematically show another serial thermal printer, wherein two return electrodes 61A and 61B are mounted on recording head 59, as thus located very near data-recording electrodes 60.
  • data-recording electrodes 60 are arranged parallel and one above another, such that their tips are aligned in a vertical line.
  • Return electrodes 61A and 61B are placed on recording head 59, vertically extend parallel to each other, with the array of electrodes 60 between them.
  • Return electrode 61A is grounded by switch 62A, whereas return electrode 61B is grounded by switch 62B.
  • switch 62A coupled to return electrode 61A is closed, whereas switch 62B coupled to return electrode 61B is opened.
  • the data currents supplied from data-recording electrodes 60 to the resistive ink ribbon flow to return electrode 61A located down­stream of head-moving direction A-1, with respect to the array of data-recording electrodes 60.
  • switch 62B is closed, whereas switch 62A is opened.
  • the data currents flows from data-recording electrodes 60 to return electrode 61B located downstream of head-moving direction A-2, through the unused portion of the ink ribbon (not shown).
  • the return electrode which is located downstream of the head-moving direction, with respect to the array of data-recording electrodes 60 is used so as to lead the data currents the ground.
  • the embodiment shown in Fig. 16 can attain the same advantages as the serial thermal printers shown in Figs. 13 and 15.
  • Resistive ink ribbon 16 which is used in all embodiments described above, is comprised of, as is shown in Figs. 4 and 13, resistive base film 32, elec­trically conductive layer 33, and solid ink layer 34.
  • This ink ribbon can be replaced by another three-layer ribbon 16 which is shown in Fig. 17.
  • this resistive ink ribbon 16 consists of resistive base film 32, electrically conductive layer 33 formed on base film 32, and porous ink-impregnated layer 65.
  • Ink-impregnated layer 65 contains solid particles 66 of ink which can be softened, melted, or sublimed when heated to a predetermined temperature.
  • the three-layer ink ribbon 16 shown in Figs. 4 and 13, or the three-layer ink ribbon 16 shown in Fig. 17 can be replaced by the two-layer ink ribbons 70 and 71, both shown in Fig. 18.
  • Ribbon 70 is designed to generate heat
  • ribbon 71 is designed to print data.
  • heat-generating ribbon 70 is in con­tact with recording head 5, and data-printing ribbon 71 is interposed between ribbon 70 and paper 27.
  • return electrode 15 need not be located upstream of ribbon-feeding direction, with respect to recording head 5, in order to efficiently supply data currents from the data-recording electrodes of head 5 to return electrode 15.
  • heat-generating ribbon 70 can be quickly cooled as it is fed from head 5, thereby reducing the possibility that ribbon 70 is cut.
  • heat-generating ribbon 70 is comprised of resistive base film 70A and electrically conductive layer 70B formed on base film 70A. Ribbon 70 is pinched between cylindrical return electrode 15 and pinch roller 72 which are located downstream of the ribbon-feeding direction, with respect to recording head 5. Return electrode 15 is rotated, thereby feeding heat-generating ribbon 70 in the direc­tion of arrow E. Return electrode 15 is set at the ground potential.
  • data-printing ribbon 71 consists of base film 71A and solid ink layer 71B formed on base film 71A. Ribbon 71 is pinched between pinch rollers 73 and 74, both made of rubber and located downstream of the ribbon-feeding direction with respect to head 5. Either or both pinch rollers 73 and 74 are rotated, thus feeding data-printing ribbon 71 in the direction of arrow F.
  • Recording head 5 has 40 data-recording electrodes (not shown). Data currents are supplied to these data-recording electrodes from a constant-current source circuit (not shown, either) via a connecting cable 75.
  • Heat-generating ribbon 70 and data-printing ribbon 71 are fed from two ribbon-feeding reels (not shown) respectively, are laid one upon the other, while moving from roller 77 to roller 76, and are taken up around two ribbon take-up reels (not shown).
  • the data-recording electrodes of head 5 supply the data currents to that portion of ribbon 70 which extends between rollers 76 and 77, whereby heat is generated in those portions of base film 70A which contact the data-recording elec­trodes.
  • the heat is transferred to solid ink layer 71B of ribbon 71 via conductive layer 70B and base film 71A, whereby data is recorded on paper 27.
  • the printer shown in Fig. 18 has the advantages inherent in resistance thermal printers. More specifically, the printer can record data at high speed, can quickly cool the ribbon after the use thereof, and can apply great energy to the ribbon.
  • the printer can record data at high speed even when use is made of solid ink having a high melting point and being suitable for printing data on coarsely textured paper, or of solid ink which sublimes when heated and is thus suitable for printing images in different tones.
  • Fig. 19 shows a modification of the printer shown in Fig. 18, wherein heat-generating ribbon 70 is repeatedly used, too.
  • heat-generating ribbon 70 is fed from ribbon-feeding reel 78 and taken up around ribbon take-up reel 79, in the direction of arrow E. After ribbon 70 is used, it is fed in the direction of arrow B back to reel 78 from reel 79, so that it can be used again.
  • the operation of the printer shown in Fig. 19 will be briefly explained. While recording head 11 is moving in the direction of arrow C and supplying data currents to ribbon 70, both ribbons 70 and 71 are fed together in the direction of arrow A, with ribbon 70 held in contact with the data-­recording electrodes of head 5.
  • Fig. 20 shows another modification of the printer shown in Fig. 18, wherein the heat-generating ribbon is an endless one and repeatedly used.
  • endless ribbon 70 is wrapped around four rollers 72, 76, 77, and 91, and is driven in the direc­tion of arrow E, as roller 15, which cooperates with roller 72 to pinch ribbon 70, is rotated.
  • This roller 15 functions as a return electrode.
  • Roller 91 is urged by spring 90, thus applying an appropriate tension on heat-generating ribbon 70. Since heat-generating ribbon 70 is used again and again, the running cost of this printer is also low.
  • return electrode 15 may be located upstream of the ribbon-feeding direction E, with respect of recording head 11. If electrode 15 is so located, the heat-­generating ribbon can be more efficiently used and more effectively prevented from being cut.
  • Figs. 21 to 23 illustrate three printers, each using heat-generating ribbon 70 and data-printing ribbon 71 and having a return electrode located upstream of the ribbon-feeding direction. These printers will now be described.
  • heat-generating ribbon 70 is guided by roller 15 to recording head 11, whereas data-printing ribbon 71 is guided by roller 100 to head 11. Ribbons 70 and 71 are laid one upon the other, at recording head 11. They remain in contact with each other until they reach roller 76, and are then separated from each other. Heat-generating ribbon 70 is pinched between drive roller 21 and pinch roller 22, and is fed forward as drive roller 21 is rotated. Similarly, data-printing ribbon 71 is pinched between drive roller 73 and pinch roller 74, and is fed forward as drive roller 73 rotates. More precisely, ribbons 70 and 71 are fed in the directions of arrows E and F as drive rollers 21 and 73 rotate in the directions of arrows G and H.
  • Ribbons 70 and 71 are fed from two ribbon-feeding reels (not shown), respectively, and are taken up around two ribbon take-up reels (not shown, either) after passing drive rollers 21 and 73.
  • Back tension is applied to both ribbons 70 and 71 by two back tension-­applying mechanisms (not shown), and do not slacken while being fed from the ribbon-feeding reels to the ribbon take-up reels.
  • Rollers 15, 21, 22, 73, 74, 76 and 100, the ribbon-feeding reels, the ribbon take-up reels, and the back tension-applying mechanisms are mounted on carriage 23 (Fig. 2).
  • Carriage 23 is moved in the direction of arrow C at the average speed of Va, thereby to print data on recording paper 27.
  • Recording head 11 is fastened to carriage 23 by head holder 13 and can rotate the axis of holder 13. Head 11 is pressed onto recording paper 27 in order to record data on paper 27. Roller 15 not only guides heat-generating ribbon 70 to head 11, but also functions as a return electrode. It is made of electrically con­ductive material such as a metal, and is set at the ground potential.
  • Speed Vb of feeding heat-generating ribbon 70 is determined by the circumference of drive roller 21 and the rotational speed thereof.
  • speed Ve of feeding data-printing ribbon is determined by the circumference of drive roller 73 and the rotational speed thereof. If Vb and Ve are equal to Va as in the conventional serial thermal printer, neither ribbon moves at all relative to recording paper 27 since either ribbon is fed in the direction opposite to the head-­moving direction C. In this case, the same length of either ribbon as the length of one line of data is con­sumed to record this line of data on paper 27. In the embodiment shown in Fig. 21, Vb is less than Va; that is, heat-generating ribbon 70 is fed more slowly in the direction of arrow E than recording head 11 is moved in the direction of arrow C.
  • ribbon 70 moves relative to paper 27 at the speed of Va-Vb (greater than 0) in the direction of arrow C.
  • Speed Vb is made less than Va by either rotating drive roller 21 at low speed, or reduc­ing the diameter of drive roller 21. In the present instance, the diameter of roller 21 is reduced.
  • the diameter of roller 21 is decreased to one half, the consumption of heat-generating ribbon 70 will be reduced to one half.
  • the consumption of data-printing ribbon 71 can be reduced, too, by reducing the diameter of drive roller 73 or by decreasing the rotational speed of roller 73.
  • heat-generating ribbon 70 Since no currents flow through any used portion of heat-generating ribbon 70, ink dots can be formed on paper 27 in the same density, and data-printing ribbon 71 is prevented from being cut. Furthermore, heat-­generating ribbon 70 is saved.
  • the resistance thermal printer shown in Fig. 21 can, therefore, records high-­quality image data at a low running cost.
  • the serial thermal printer shown in Fig. 22 is, so to speak, a modification of the printer illustrated in Fig. 21.
  • ribbon guide 42 is connected to the ground and, thus, functions as a return electrode.
  • Heat-generating ribbon 70 is fed to record­ing head 11, while being guided by, and in contact with, ribbon guide 42.
  • the contact resistance between ribbon 70 and guide 42 is likely to change very much.
  • ribbon guide 42 fails to function as a return electrode. If this happens, ink dots cannot be formed on paper 27 in the desired density, or heat-­generating ribbon 70 may be cut.
  • the serial thermal printer illustrated in Fig. 23 is designed to solve the problems of the printer shown in Fig. 22.
  • a pair of rollers 92 and 93 are located upstream of the ribbon-feeding direction of A, with respect to ribbon guide 42, and pinch heat-generating ribbon 70.
  • Both rollers 92 and 93 can be made of electrically conductive material. Alternatively, one of them has a rubber coating on its circumference, and the other of them is made of electrically conductive material. In the latter case, ribbon 70 must contact the roller made of electrically conductive material.
  • ribbon guide 42 can have the structure shown in Fig. 10A, Fig. 10B, or Fig. 10C.
  • ribbon guide 42 can be used in combination with roller 94, as is shown in Fig. 24A, leaf spring 95 having conductive fabric filaments 96, as is shown in Fig. 24B, or leaf spring 95 made of electrically conduc­tive material. It is preferable that roller 94 is made of electrically conductive material. Roller 94, leaf spring 95 with filaments 96, and leaf spring 95 keep ribbon 70 in contact with the sloping surface of ribbon guide 42.
  • Roller 15 shown in Figs. 21 and 22, and rollers 92 and 93 shown in Fig. 23 can have the structure shown in Figs. 11A, 11B.
  • Fig. 25 illustrates another embodiment of the present invention, i.e., a serial thermal printer, in which use is made of data-printing ribbon 71 slightly broader than recording paper 27 wrapped around a platen (not shown).
  • heat-generating ribbon 70 is fed in the same way as in the embodiment shown in Fig. 21. Every time the recording head 11 records one line of data on paper 27, recording paper 27 and data-­printing ribbon 71 are fed by predetermined distances in the direction of arrow I. Ribbon 71 can either be taken up around a reel, or fed together with paper 27 as the platen is rotated. When ribbon 71 is taken up around the reel, it can be fed less than recording paper 27, thereby to reduce its consumption. Further, as in the embodiments of Figs.
  • the diameter of drive roller 21 or the rotational speed thereof can be reduced, thereby to decrease the consumption of heat-­generating ribbon 70.
  • the printer shown in Fig. 25 is advantageous in that fewer parts are mounted on carriage 23 (Fig. 2), and carriage 23 can, therefore, be moved faster. Hence, this printer is suitable as a high-speed printer.
  • Figs. 26 to 31 show further embodiments of this invention, each having a mechanism for cooling the ink ribbon, thereby to print data in high quality.
  • the serial thermal printer shown in Fig. 26 has a pair of cooling rollers 102 and 103 arranged in the passage of ink ribbon 16 and located between recording head 11 and return electrode 15. These rollers 102 and 103 pinch ink ribbon 16 during the data-recording operation, and are rotated as ribbon 16 is fed toward recording head 11. When the data-recording operation ends or is stopped, rollers 102 and 103 are moved away from ink ribbon 16.
  • Cooling rollers 102 and 103 are made of a metal having a high thermal conductivity, such as copper, aluminum or molybdenum. Alternatively, they can be made of ceramics such as Al2O3. They should be as large as possible, so as to absorb much heat. It is required that their length be greater than the width of ink ribbon 16.
  • the used portion of ribbon 16 is pinched between rollers 21 and 22.
  • Roller 21 is rotated by a drive means (not shown) in the direction of the arrow shown in Fig. 26, thereby feeding ribbon 16 in the direction of arrow A.
  • head 11 transfers ink dots from ribbon 16 onto recording paper 27.
  • the data currents supplied from head 11 to base film 32 of ribbon 16 during the data-recording operation flow into return electrode 15 through conductive layer 33 of ribbon 16. These currents flows to electrode 15 via the substan­tially entire portion of base film 32, which contacts return electrode 15. Therefore, the current density is this portion of base film 32 is low. However, this current density increases in proportion to the number of the data-recording electrodes of head 11, which are energized simultaneously.
  • the inventors hereof operated the printer iden­tical with the printer shown in Fig. 26, except that cooling rollers 102 were removed, changing the distance between head 11 and return electrode 15 to various values, and also changing the data-recording speed to various values.
  • the results of this experiment were: the longer the distance between head 11 and electrode 15, and the higher the data-recording speed, the greater the possibility of degrading the printing quality.
  • Either cooling roller 102 or 103 can be used as a return electrode. If this is the case, it is desirable that the roller be made of material exhibiting great thermal conductivity and great electrical conductivity, and be as large as possible to have a sufficient heat capacity.
  • ribbon guide 42 can be used as a return electrode, in which case cooling roller 94 and ribbon guide 42 pinch ink ribbon 16 as is illustrated in Fig. 24, so that roller 94 absorbs heat from ribbon 16.
  • the serial thermal printer shown in Fig. 27 has reaf spring 104 for cooling ink ribbon 16.
  • Spring 104 is fixed at one end. The other end of this spring 104 is curved, and is held in contact with the base film of ink ribbon 16 by means of an urging mechanism (not shown) during the data-recording operation.
  • the heat generated in ribbon at return electrode 15 is trans­mitted to leaf spring 104, whereby ink ribbon 16 is cooled.
  • Spring 104 is made of material exhibiting high thermal conductivity, such as copper. To dissipate the heat effectively, leaf spring 104 can have fins.
  • the serial thermal printer shown in Fig. 28 has liquid-applying roller 105 for cooling ink ribbon 16.
  • Roller 105 is made of sintered porous metal.
  • Roller 105 has an inlet port (not shown), and cooling liquid is introduced into roller 105 through this inlet port.
  • the liquid is supplied to the circumference of roller 105 through capillaries of roller 105.
  • the liquid is, preferably, a very volatile one, such as water or ethyl alcohol.
  • the cooling liquid is coated on the base film of ribbon 16. As soon as the liquid is coated the base film, it evaporates, thus cooling ink ribbon 16 efficiently.
  • the cooling liquid serves to stabilize the mutual contact of ink ribbon 16 and roller 105.
  • a layer of foamed rubber can be bonded to the free end of leaf spring 104 used in the printer illustrated in Fig. 27.
  • cooling liquid is applied to the foamed rubber layer, all the time the printer is operated. The liquid not only cools ink ribbon 16, but also stabilize the mutual contact of ink ribbon 16 and leaf spring 104.
  • the serial thermal printer shown in Fig. 29 is provided with Peltier element 106 which is used as a cooling means.
  • element 106 comprises heat-absorbing plate 107, thin film 108 coated on plate 107, n-type semiconductor 109 connected to plate 107, p-type semiconductor 110 coupled to plate 107, heat-radiating plate 111 connected to p-type semi­conductor 110, and heat-radiating plate 112 connected to n-type semiconductor 109.
  • Heat-absorbing plate 107 contacts ink ribbon 16, but is electrically insulated from ribbon 16 since thin film 108 is electrically insu­lative, though it is thermally conductive.
  • An operating current is supplied to element 106.
  • This current flows from plate 112 to plate 111 via n-type semiconductor 109, plate 107, and p-type semiconductor 110.
  • n-type semiconductor 109 As the current flows from n-type semiconductor 109 to p-type semiconductor 110 through heat-absorbing plate 107, endothermic energy is generated at the interface between plate 107 and semiconductor 109 and also at the inter­face between plate 107 and semiconductor 110. As a result, plate 107 is cooled, and in turn cools ink ribbon 16.
  • plates 111 and 112 can be provided with fins.
  • the serial thermal printer shown in Fig. 30A has a ribbon-cooling means which is located between recording head 11 and return electrode 15 and does not contact ink ribbon 16.
  • this cooling means comprises fan 116 connected to a shaft.
  • the shaft vertically extends through a hole cut in carriage 23.
  • Wire 118 is wound one time around that portion of the shaft which protrudes downwardly from carriage 23, and is horizontally stretched, with both ends fastened to the frames of the printer.
  • fan 116 is rotated, thereby applying air in the direction of arrow J.
  • a pair of curved thin plates 119 are located parallel to that unused portion of ribbon 16 which extends between return electrode 15 and head 11.
  • the upper end of the first thin plate face the base film of ribbon 16, whereas the upper end of the second thin plate faces solid ink layer of ribbon 16.
  • the air supplied by fan 116 flows through the gap between the first thin plate and ribbon 16 and the gap between the second thin plate and ribbon 16, thus cooling ink ribbon 16.
  • the serial thermal printer shown in Fig. 31 is pro­vided a cooling means which does not contact ink ribbon 16, but can cool the ink ribbon.
  • This cooling means comprises fan box 120 arranged within the housing of the printer, flexible tube 121 connected at one end to fan box 120, and forked air outlet port 122 coupled to the other end of flexible tube 121.
  • the two sections of air outlet port 122 protrude upward from carriage 23 and oppose each other, with an unused portion of ribbon 16 located between them.
  • air outlet port 122 is small, this cooling means is suitable in the case where the distance between head 11 and return electrode 15 is so short that no cooling rollers can be provided between head 11 and electrode 15.
  • the ribbon-cooling means which have been described with reference to Figs. 26 to 31, can be used in any possible combination. They can be provided within ribbon cassette 20 (Fig. 2), not on carriage 23.
  • Figs. 32A and 32B are equivalent circuit diagrams showing how data currents flow from data-recording electrodes 30 to return electrode 15.
  • Rf is the resistance between each electrode 30 and con­ductive layer 33 of ink ribbon 16
  • Rc is the resistance of conductive layer 33
  • Rr is the resistance between conductive layer 33 and return electrode 15.
  • Resistance Rf is 100 to 400, whereas Rr is as low as a few ohms.
  • Resistance Rc depends on the material of conductive layer 33 and the thickness thereof; it is several ohms to tens of ohms when layer 33 is made of aluminum and has a thickness of 0.05 to 0.1 ⁇ m.
  • Recording head 11 has tens of data-recording elec­trodes 30 arranged parallel in a line parallel to the paper-feeding direction if head 11 is a serial print head. If head 11 is a line print head, it has hundreds of data-recording electrodes 30 arranged parallel in a line extending at right angles to the paper-feeding direction. In either case, a plurality of data-­recording electrodes contact ink ribbon 16 at their tips. When only one of these electrodes supplies data current I to conductive layer 33 of ribbon 16 as is shown in Fig.
  • voltage drop Vd occurring in resis­tive ink ribbon 16, i.e., the difference between the potential of electrodes 30 and the potential of return electrode 15, is (Rf + Rc + Rr) ⁇ I.
  • the power-supply voltage for the constant current circuit must be equal to or higher than 45 V.
  • data current I is greater than 50 MA, and head 11 has more than 40 data-recording electrodes, much more power-supply voltage is required.
  • data current I is supplied from all electrodes 30 to ink ribbon 16, heat is generated in those portions of ribbon 16 which are aligned in a line, and ribbon 16 may be cut even if return electrode 15 contacts an unused portion of ribbon 16.
  • Electrodes 30 are divided into a plurality of groups. When most of electrodes 30 need to be driven, those of one group are driven at a time, and those of another group are driven at a different time. Examples of this method will be described.
  • Figs. 33A and 33B are diagrams explaining a first example of the method for driving data-recording elec­trodes 30.
  • electrodes 30 are divided into two groups, the first group consisting of the odd-numbered electrodes, and the second group consisting of the even-numbered electrodes.
  • data current I is supplied to odd-numbered electrodes 30 during the first half of every data-­recording period T.
  • Fig. 33B data current I is supplied to even-numbered electrode 30 during the second half of every data-recording period T.
  • data-­recording electrodes 30 are divided into two groups. In­stead, electrodes 30 can be divided three or more groups, and data current I can be applied to the electrodes of one group at a time, and to those of another group at a different time. Then, the power-supply voltage required for the constant current circuit can be more reduced.
  • odd-numbered electrodes 30 are driven in the first half of each data-recording period T, and even-numbered electrodes 30 are driven in the second half of this period T.
  • heat is generated in those portions of base film 32 which are staggered as is shown in Fig. 34B. Since the heated portions are separated form one another, unlike in the case where all electrodes 30 are simultaneously driven, the possibility that ribbon 16 is cut by tension 135 decreases.
  • Figs. 35A and 35B, 36A and 36B, and Figs. 37A and 37B These methods are identical to the method shown in Figs. 33A and 33B in that electrodes 30 are divided into two groups, but is different in that the electrodes of the first group and those of the second group are alternately driven, each for a period shorter than T/2. These methods can print data, consuming the same power as is used in the method shown in Fig. 33A and 33B.
  • Figs. 36A and 36B have a drawback.
  • this method When this method is used, the voltage drop occurring in ink ribbon 16 temporarily increases during the pre-heating period Ts and during the heat-retaining period Te. In case the voltage drop exceeds the power-­supply voltage to head 11, head 11 can no longer perform its function.
  • the method shown in Figs. 37A and 37B can be employed in which the current pulse supplied to all electrodes 30 during the preheating period Ts and the head-retaining period Te is less than data current I. This method serves to prevent an excessive drop voltage. and can yet help to maintain ribbon 16 at a sufficiently high temperature.
  • Figs. 38A and 38B illustrate another method of driving data-recording electrodes 30.
  • This method is similar to that one shown in Figs. 33A and 33B, but the current pulse supplied to the odd-numbered electrodes and the current pulse supplied to the even-numbered electrodes are longer than T/2, and thus overlap each other in phase.
  • recording head 11 When recording head 11 is driven by this method, it can print a all-mark pattern in a suf­ficient density, whereas it cannot do so when it is driven by the method shown in Figs. 33A and 33B unless the pulses supplied to the two groups of electrodes 30 have a current value greater than that shown in Figs. 33A and 33B.
  • Figs. 39A and 39B illustrate another method of driving data-recording electrodes 30, which is identical to the method shown in Figs. 38A and 38B, except that the overlapping portions of the two current pulses supplied to the two groups of electrodes 30 have less current value than those of the two current pulses used in the method of Figs. 38A and 38B.
  • the method shown in Figs. 39A and 39B can print a all-mark pattern in a sufficient density by adjusting the period during which the two current pulses overlap.
  • micro-­control of heat which comprises the step of controlling the width and phase of the current pulse supplied to each electrode 30.
  • a micro-control which comprises the step of changing the current supplied to all electrodes 30 in order to compensate the variation of the ambient temperature and/or the temperature of head 11.
  • the width and phase of the current pulse corresponding to specified pixel 141 are determined from the position of this pixel 141 with respect to eight neighboring pixels 142, which are arranged, together with specified pixel 141, in 3 ⁇ 3 matrix pattern, as is shown in Fig. 40. Then, the width and phase of the current pulse corresponding to the pixel next to specified pixel 141 with respect to the main scanning direction, are determined from the position of this pixel with respect to the other eight neighboring pixels. The width and phase of the current pulse corresponding to any other pixel shown in Fig. 40 are determined in the same way. In other words, the micro-control of head is achieved by selecting one of various predetermined 3 ⁇ 3 pixel-matrix patterns.
  • a current pulse having a width of T/2, as is shown in Fig. 42A is supplied to data-recording electrode 30 corresponding to specified pixel 141.
  • the phase of this current pulse is selected in accordance with whether this data-recording electrode is odd-numbered or even-numbered.
  • current pulses having such a short width as is shown in Fig. 42B is supplied to data-recording electrode 30 which corresponds to specified pixel 141.
  • a current pulse is supplied to electrode 30 corresponding to specified pixel 141 as is shown in Fig. 42C, thereby to preheating this data-­recording electrode 30.
  • a current pulse is supplied to electrode corresponding to specified pixel 141 as is shown in Fig. 42D, thereby to maintain ink ribbon 16 at a sufficiently high tem­perature.
  • the width of a current pulse must be inversely proportional to the number of black dots included in the 3 ⁇ 3 matrix pattern, and the phase of the current pulse must be determined in accordance with whether or not the three pixels aligned in the sub-­scanning direction (Fig. 40) are black dots or white dots. More specifically, when specified pixel 141 and the pixel preceding specified pixel 141 and aligned therewith in the sub-scanning direction are black dots as is shown in Fig.
  • a current pulse having a width determined by the fact that two pixels including the specified one 141 are aligned in the sub-scanning direction is supplied to electrode 30 corresponding to specified pixel 141, such that the leading edge of this pulse coincides with the starting point of data-­recording period T, as is illustrated in Fig. 44A.
  • pixel 141 and the pixel following pixel 141 and aligned therewith in the sub-scanning direction are black dots as is shown in Fig. 43B
  • a current pulse having the same width as is shown in Fig. 44A is supplied to electrode 30 corresponding to specified pixel 141, such that the trailing edge of this pulse coincides with the ending point of data-recording period T.
  • a current pulse having a width determined by this fact is supplied to electrode 30 corresponding to specified pixel 141, such that the center of this pulse coincides with the center point of data-recording period T, as is illustrated in Fig. 44C.
  • the pixels identified by mark "X" correspond either to mark signals or to space signals. These pixels do not influence the phase of the current pulse supplied to data-recording electrode 30 corresponding to specified pixel 141 at all.
  • the temperature of ink ribbon 16 is maintained at an appropriate value by supplying a current pulse having appropriate width and phase to the data-recording electrode 30 correspond­ing to specified pixel 141, as has been described above. Therefore, ink ribbon 16 is not heated excessively, the constant current circuit does not require a high power-supply voltage, and the possibility that ribbon 16 is cut is reduced.
  • the electrodes 30 of recording head 11 are divided into two groups, the first group consisting of the odd-numbered electrodes, and the second group consisting of the even-numbered electrodes.
  • the first group can consists of the first N/2 electrodes
  • the second group can consists of the remaining N/2 electrodes.
  • the first group can be comprised of odd-numbered sub-groups each consisting of several electrodes 30, and the second group can be formed of even-numbered sub-groups each consisting of several electrodes 30.
  • data-recording electrodes 30 can be divided into three or more groups.
  • Figs. 45A and 45B are diagrams showing an example of a circuit for generating current pluses for driving data-recording electrodes 30 by one of the methods described above.
  • Figs. 46 shows the waveforms of the current pulse codes stored in a ROM shown in Fig. 45A. With reference to these figures, the method of driving electrodes 30 will be explained in greater detail.
  • image data to be recorded on paper 27 is supplied, in the form of serial binary data, from a data processor (not shown) to 3-bit shift register 150.
  • This image data is supplied, as address data, from shift register 150 to ROM 151 which stores the code data representing various ways of applying a current pulse to the electrode 30 corresponding to specified pixel 141 (Fig. 40). (These ways of applying the current pulse will be hereinafter referred to as "pulse-supplying patterns".)
  • the second bit of the 3-bit image data stored in shift register 150 is supplied to one-line (1 bit ⁇ 40) buffer 152.
  • the second bit of each 3-bit image data item is supplied to one-line buffer 152.
  • the second-bit data (40 bits) is supplied from buffer 152 to 3-bit shift register 153.
  • the second-bit data is then supplied from shift register 152 to ROM 151, in the form of parallel 3-bit data items and as address data.
  • the second bit of each 3-bit address data output by shift register 153 is supplied to one-line (1 bit ⁇ 40) buffer 154. This bit is the address of specified pixel 141 shown in Fig. 40.
  • the second-bit data (40 bits) is supplied from buffer 154 to 3-bit shift register 155.
  • the second-bit data is supplied from shift register 155 to ROM 151, in the form of parallel 3-bit data items and as address data.
  • Fig. 46 schematically represents the various pulse-supplying pattern codes which are stored in ROM 151, in the form of code data.
  • the address signal designating specified pixel 141 is input to terminal A0 of ROM 151
  • the address signals designating the eight reference pixels 142 are input to terminals A1 to A8 of ROM 151.
  • These nine address signals designate one of the pattern codes stored in ROM 151.
  • the 6-bit code data representing the selected pattern code is output from ROM 151 and supplied to first 6 bit ⁇ 40 line-buffer 174.
  • Other 6-bit code data items are supplied from ROM 151 to first line-buffer 174 as other pattern codes are selected in accordance is 9-bit addresses are input to ROM 151.
  • the next 40 code data items supplied from ROM 151 are input into second 6 bit ⁇ 40 line-buffer 175.
  • the 40 code data items, which corre­spond to a first line of data, are supplied from first line-buffer 174 to image data conversion ROM 176.
  • further 40 code data items supplied from ROM 151 which correspond to a third line of data, are input into first line-buffer 174.
  • timing controller 177 generates timing signals which are used to divide data-recording period T into 32 segment periods. These timing signals are supplied to counter 156 and counted by this counter 156. The count value of counter 156 is supplied, as address data, to image data conversion ROM 176. Then, 40 bit image data items corresponding to the 40 code data items, which has been input from first line-buffer 174 into ROM 176 and correspond to the first line of data, are sequentially supplied from ROM 176 to 40-bit shift register 157 shown in Fig. 45B, in synchronism with clock signals output by timing controller 177.
  • bit image data item "1" is supplied to 40-bit shift register 157 in synchronism with the clock signals out­put by timing controller 177, during 0th to 4th segment periods, that is, while counter 156 is counting first four timing signals. Then, bit image data item "0" is supplied to 40-bit shift register 157 in synchronism with the clock signals output by timing controller 177, during 5th to 32nd segment periods, that is, while counter 156 is counting 5th to 32nd timing signals.
  • bit image data item "1" is supplied to 40-bit shift register 157 in synchronism with the clock signals output by controller 177, while counter 156 is counting 1st to 4th timing signals, 9th to 12th timing signals, 17th to 20th timing signals, and 25th to 28th timing signals. Then, bit image data item "0" is supplied to 40-bit shift register 157 in synchronism with the clock signals output by timing controller 177, while counter 156 is counting 5th to 8th timing signals, 13th to 16th timing signals, 21st to 24th timing signals, and 29th to 32nd timing signals.
  • timing controller 177 supplies a latch signal to latch 158.
  • latch 158 latches the 40 bit image data items from shift register 157.
  • the data processor (not shown) supplies data to D/A converter 164.
  • This data which represents data currents to be supplied to data-recording electrodes 30-1 to 30-40, is converted by D/A converter 164 to analog signals. These analog signals are supplied to current-to-voltage converter 166 and thus converted into voltage signals.
  • the voltage signals are supplied, as reference voltages, to switching elements 168-1 to 168-40 of constant current switching circuits 162-1 to 162-40.
  • 40 bit image data items are supplied from latch 158 to two-input AND gates 160-1 to 160-40, at the first input terminal.
  • the bit image data items "1" supplied to some or all AND gates are supplied to the switching elements of the switching circuits which are coupled by these AND gates to latch 158. These switching elements are turned on, and the switching circuits having these elements are electri­cally connected to current-to-voltage converter 166.
  • the reference voltage is applied from converter 166 to those of constant current circuits 170-1 to 170-40 which are included in the constant current switching circuits whose switching elements have been turned on.
  • the constant current circuits applied with the reference voltage supply a current pulse from power-supply voltage source +V to those of data-recording electrodes 30-1 to 30-40 which are connected to the constant current circuits.
  • the data-recording electrodes, to which the current pulses are supplied supply data currents to ink ribbon 16, thereby recording the image data on paper 27.

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EP19880301800 1987-03-02 1988-03-02 Elektrothermisches Transfer-Druckgerät Withdrawn EP0289115A1 (de)

Applications Claiming Priority (10)

Application Number Priority Date Filing Date Title
JP4515087A JPS63212565A (ja) 1987-03-02 1987-03-02 通電転写記録装置
JP45150/87 1987-03-02
JP137675/87 1987-06-02
JP13767587A JPS63302075A (ja) 1987-06-02 1987-06-02 通電転写記録装置
JP18698187A JP2538932B2 (ja) 1987-07-27 1987-07-27 通電転写記録装置
JP186981/87 1987-07-27
JP187630/87 1987-07-29
JP18763087A JPS6431657A (en) 1987-07-29 1987-07-29 Electrotransfer recorder
JP19140987A JPS6434759A (en) 1987-07-30 1987-07-30 Conduction transfer recorder
JP191409/87 1987-07-30

Publications (1)

Publication Number Publication Date
EP0289115A1 true EP0289115A1 (de) 1988-11-02

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EP19880301800 Withdrawn EP0289115A1 (de) 1987-03-02 1988-03-02 Elektrothermisches Transfer-Druckgerät

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EP (1) EP0289115A1 (de)

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0329478A2 (de) * 1988-02-18 1989-08-23 Kabushiki Kaisha Toshiba Thermischer Aufzeichnungsdrucker
EP0978386A3 (de) * 1998-08-06 2001-03-07 Francotyp-Postalia AG & Co. Thermotransfer-Druckvorrichtung

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE3219781A1 (de) * 1981-05-26 1982-12-16 Ricoh Co., Ltd., Tokyo Aufzeichnungsverfahren und -vorrichtung
EP0146069A2 (de) * 1983-12-12 1985-06-26 International Business Machines Corporation Verfahren und Anordnung zum thermischen Drucken durch Übertragung
US4558963A (en) * 1982-08-30 1985-12-17 International Business Machines Corporation Feed rates and two-mode embodiments for thermal transfer medium conservation
EP0218551A1 (de) * 1985-09-25 1987-04-15 Hermes Precisa International S.A. Elektrothermischer Drucker

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE3219781A1 (de) * 1981-05-26 1982-12-16 Ricoh Co., Ltd., Tokyo Aufzeichnungsverfahren und -vorrichtung
US4558963A (en) * 1982-08-30 1985-12-17 International Business Machines Corporation Feed rates and two-mode embodiments for thermal transfer medium conservation
EP0146069A2 (de) * 1983-12-12 1985-06-26 International Business Machines Corporation Verfahren und Anordnung zum thermischen Drucken durch Übertragung
EP0218551A1 (de) * 1985-09-25 1987-04-15 Hermes Precisa International S.A. Elektrothermischer Drucker

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0329478A2 (de) * 1988-02-18 1989-08-23 Kabushiki Kaisha Toshiba Thermischer Aufzeichnungsdrucker
EP0329478A3 (de) * 1988-02-18 1991-10-16 Kabushiki Kaisha Toshiba Thermischer Aufzeichnungsdrucker
US5157413A (en) * 1988-02-18 1992-10-20 Kabushiki Kaisha Toshiba Thermal inked ribbon printer mechanism
EP0978386A3 (de) * 1998-08-06 2001-03-07 Francotyp-Postalia AG & Co. Thermotransfer-Druckvorrichtung

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