METHOD OF INK-JET PRINTING AND AN INK-JET PRINTING HEAD FOR CARRYING OUT THE METHOD

Abstract: A method of ink-jet printing is carried out by focusing a light beam from a quantum generator onto an expendable liquid printing material in a jet from the direction of the open end of the jet, with an information carrier placed in front of the open end, in order to generate a pressure pulse ensuring the expulsion of a droplet of the liquid onto the carrier. The method is carried out by directing the light beam onto the material in a jet either at an angle to its surface between the jet and the carrier, or through a carrier which is transparent to the wavelength of the beam. An ink-jet printing head has rows of jets, each with one blind end formed in the body of a driving drum. The head is provided with means for feeding the expendable liquid printing material into the jets through their open ends and with means for generating a pressure pulse in the jets, the latter means comprising a quantum generator of a light beam with a device for focusing the beam onto the liquid material from the direction of the jets' open end in front of which the carrier is located, and with a means for deflecting the light beam over the ends.

Description: The invention concerns a method for ink-jet printing according to the preamble of claim 1 and an ink-jet printing head according to the preamble of claim 4. A method of ink-jet printing is known which comprises placing an information carrier opposite jets filled with an expendable liquid printing material, and generating pressure pulses in those jets for feeding the printing material by portions onto the information carrier (US-A-4 580 148). In the known method a pressure pulse is created in the jets due to pulse heating of the liquid printing material which results in the formation of steam in the heating zone, rapid expansion of the liquid and the expulsion of droplets of the liquid from the jet. A disadvantage of this method is that a source of thermal action on the liquid printing material is placed directly in each jet and is controlled from outside, which makes realization of this method difficult when there are a large number of jets. Furthermore, this method does not make it possible to obtain a high frequency of expulsion of droplets, since before the generation of a subsequent pressure pulse it is necessary to reduce the temperature in a jet for the flow therein of the next portion of liquid printing material. An ink-jet printing head realized according to the patent cited above comprises the same number of resistors for heating the liquid material as there are jets therein. Each resistor has a lead for connecting it to a voltage source. In order to expel droplets from one or another jet, the power supply circuit of a corresponding resistor is closed. When a current pulse flows through that resistor, it is heated, the liquid substance in the zone in which the resistor is positioned is heated to a steam state, as a result of which the liquid, expanding, creates an impact pulse expelling a droplet through the jet. Then, after the liquid has cooled, the described process can be repeated. A disadvantage of such heads is their structural complexity, since the number of resistors should correspond to the number of jets mounted with a small spacing therebetween and provided with a system of current leads; low resolution since the aforesaid jets with resistors cannot be positioned with a small spacing; low reliability, since the mode of multiple pulse heating of resistors to a sufficiently high temperature predetermines their limited service life; low productivity since the next expulsion of droplets from a jet is only possible after the temperature therein has been reduced and there is a flow therein of the next portion of expendable liquid printing material. From JP-A-02-147 346 a method and an apparatus for ink-jet printing are known wherein an information carrier is positioned opposite to jet nozzles filled with a liquid printing material and a laser beam is focussed on this material. The laser beam is focussed by an objective lense to an absorbing layer. The absorbing layer is separated from the printing material in a liquid chamber by a protection layer. The objective lense is moved by an actuator drive circuit whereby the focal position in the absorbing layer is varied. Known from JP 61 118 273A are a method and an apparatus for ink-jet printing wherein an information carrier is positioned opposite to jets filled with an expendable liquid printing material and a laser beam is focussed on this liquid material, using jets which have one blind end at the side opposite to the location of the information carrier. The object at the base of the invention is to create such a method and such a head for ink-jet printing which would eliminate the arrangement directly in the head of a source of impact pulses for expelling a droplet of color liquid from its jets, simplify the construction of the head, enhance the reliability and service life, increase the resolution and speed. Thus the invention concerns a method for ink-jet printing as defined in claim 1. With such a method, the source of impact action on the expendable liquid printing material is outside the jet, which simplifies the possibility of its realization where there are a large number of jets. It is advisable that the beam of the quantum generator be directed at an angle to the surface of the liquid printing material which is in the jet, between the end of the jet and the information carrier. With such a method, expulsion of droplets of the material from the jet is ensured along its axis independent of the angle of incidence of the light beam from the quantum generator onto the surface of the liquid material in the jet, which makes it possible for the carrier and jet to converge and to direct the light beam from the quantum generator between them to the jet. It is advisable that a carrier be used which is transparent for the predetermined wavelength radiated by the quantum generator and that the light beam from the quantum generator be directed through it to the liquid printing material in the jet. With such a method maximum convergence between the carrier and jets with liquid printing material is ensured and its realization is simplified. Additionally, the invention concerns an ink-jet printing head as defined in claim 4. With such a realization of the ink-jet printing head, its construction is simplified, since elements for impact action on the liquid material are not present in the jets of the head; reliability of its operation is enhanced due to simplification of the construction and the removal therefrom of parts operating in a mode of abrupt temperature differences; resolution of the head is enhanced since the diameter of the jets may be reduced to the diameter of the light beam of the quantum generator, and the spacing between the jets may also be reduced in practice to a magnitude somewhat exceeding the diameter of the jets, i.e. the resolution of the head approaches the theoretically possible value; the speed is increased since due to rotation of the drum with the jets, rows of jets already filled with expendable liquid printing material will be successively delivered to be affected by the light beam of the quantum generator. It is advisable that the blind bases of the jets be made in the form of spheres. Such a realization of the head will promote a more effective expulsion of droplets of material onto the carrier after the light beam of the quantum generator has entered the jet. It is advisable that the means for feeding the expendable liquid printing material into the jets contain a bath with this material, a driving roller transferring the material from the bath onto the surface of the drum when it rotates in order to fill the jets, and a knife removing surplus ink from the surface of the drum. Such a realization of the drum makes it possible to rapidly and easily fill the jets, excluding the dependence of the supply of liquid material therein on the temperature in the jets after the expulsion of droplets. It is advisable that the light beam of the quantum generator be directed at an angle to the surface of the liquid printing material in a jet between the end of the jet and the information carrier. Such a realization of the head makes it possible to ensure the expulsion of droplets of material from the jet along its axis independent of the angle of incidence of the light beam of the quantum generator onto the surface of the liquid material in a jet and to simplify its construction. It is advisable that the information carrier be made transparent for a predetermined wavelength radiated by the quantum generator and be placed in the path of its light beam to the surface of the expendable liquid printing material in a jet. Such a realization of the head makes it possible to converge the carrier and jet to a maximum degree and to create a compact construction thereof. The invention will further be explained by a description of concrete, non-restrictive, embodiments of the instant invention and by the appended drawings, wherein: Fig. 1 shows the proposed method of ink-jet printing with the light beam of a quantum generator directed at an angle to the surface of liquid material in a jet. Fig. 2 shows the proposed method of ink-jet printing where the light beam of a quantum generator passes to the surface of the liquid material in a jet through a carrier which is transparent in respect of the wavelength of the beam. Fig. 3 shows a general view of the proposed ink-jet printing head. The dotted line shows one of the possible variants of passage of the light beam of the quantum generator to the jets with liquid material. Fig. 4 shows a view along the section II-II in Fig. 3. The proposed method of ink-jet printing is carried out in the following manner. An information carrier C (Fig. 1) is placed opposite jet B which is filled with expendable liquid printing material. Then a light beam of a quantum generator E is focused on the liquid printing material. In accordance with the discovery of the "Light-hydraulic effect" (Diploma No. 65 of the BI No. 19, 1969), an impact pulse is produced when a light beam of a quantum generator is absorbed inside a liquid. Using this effect, an impact pulse is created directly in jet B filled with a liquid printing material, as a result of which droplets of the liquid fly out of the jet and impinge on the information carrier. In a similar manner droplets of the liquid impinge on the information carrier when the light beam passes to the surface of the liquid material in the jet B through a carrier which is transparent in respect of the wavelength of the beam (Fig. 2). It is obvious from the description of the proposed method provided above that the source of impact action on the liquid material is outside the jet, which makes it possible to enhance the quality of printing by reducing the diameter of the droplets and increasing the density at which they are disposed on the information carrier. In order to carry out the proposed method of ink-jet printing it is necessary to ensure that the jets are filled with expendable liquid printing material and that the light beam of the quantum generator be deflected over the open end faces of the jets. This is carried out by means of the ink-jet printing head shown in Fig. 3. The proposed ink-jet printing head comprises rows of jets, each with one blind end, which are formed in the body of a drum 2 provided with a rotation drive (not shown in the drawings). The open ends of the jets 1 are positioned on the surface of the drum 2 in rows. The axis of each jet at the point of outlet on the surface of the drum 2 is positioned on a line tangent to it. The blind bases of the jets 1 are made in the form of spheres. Means 3 for feeding expendable liquid printing material to the jets 1 is made with the possibility of filling them through the open end and comprises a bath 4 with that material, a drive roller 5 bathing in the material in the bath 4 and pressing against the surface of the drum 2, and a knife 6. Means 7 for creating a pressure pulse in the jets 1 comprises a quantum generator 8 of a light beam 9 with a device 10 for focusing that beam onto the expendable liquid printing material from the side of the open ends of the jets 1, in front of which a carrier 11 is disposed, and a device 12 for deflecting the light beam 9 over those ends. The proposed ink-jet printing head operates in the following manner. When the drum 2 and the roller 5 rotate, the expendable liquid printing material fills the jets 1 through their open ends. The rows of jets 1 filled with liquid material enter the zone in which the carrier 11 is positioned. In accordance with a predetermined program the beam 9 of the quantum generator 8 is focused by means of device 10 onto the liquid material from the direction of the open ends of corresponding jets of a concrete row. When the light beam 9 is absorbed inside the liquid of corresponding jets 1, a light-hydraulic effect is created, as a result of which an impact pulse is created, which is intensified by the sphere of the blind ends of those jets, and droplets of liquid are transferred from those jets onto the carrier 11. Then the rotating drum 2 brings the next row of jets 1 under the scanning of the beam 9 and the described process is repeated until a combination of spots comprising a text or image appears on the carrier during the joint movement of the carrier 11 and rotation of the drum 2. The principle of operation of the proposed head does not depend on whether the beam 9 of the quantum generator 8 impinges on the liquid in the jet 1 at an angle between the carrier 11 and the surface of that liquid in the jet or through a carrier 11 which is transparent in respect of the wavelength of the beam.

Claims: A method for ink-jet printing wherein an information carrier (11) is positioned opposite to jets (1) filled with a liquid expendable printing material and a laser beam (9) is focussed on this liquid material wherein jets (1) are used having one blind end at the side opposite to the location of the information carrier (11), characterized in that the laser beam (9) is focussed onto the liquid material from the direction of open ends of the jets (1), the laser beam (9) producing a lighthydraulic effect in the liquid material and causing shock pulses to eject drops of liquid onto the information carrier (11). The method according to claim 1, characterized in that the laser beam (9) is directed at an angle to the surface of the liquid material in the jet (1) between the end of the jet (1) and the information carrier (11). The method according to claim 1, characterized in that an information carrier (11) is used which is transparent for the laser beam (9) and the laser beam (9) is directed through the information carrier (11) onto the liquid material in the jet (1). An ink-jet printing head comprising a row of jets (1) being formed in a rotatable drum body (2) and being open to the surface of the drum body (2), the axis of each jet (1) passing perpendicularly through the axis of the drum body (2), means (3) for filling the jets (1) with an expendable liquid printing material by filling the jets through the open ends, means (7) for generating a pressure pulse in the jets (1) for feeding the material in portions onto an information carrier (C), said generating means (7) including a quantum generator (8) generating a laser beam (9) and having a device (10) for focussing the laser beam (9) onto a jet (1), and a device (12) for deflecting the laser beam (9) over the row of jets (1), wherein the jets (1) are provided with one blind end within the drum body (2), characterized in that the quantum generator (8) is configured to produce a light-hydraulic effect in the printing material within the jets (1), and the device (10) for focussing is directed to the printing material through the open ends of the jets (1). The ink-jet printing head according to claim 4, characterized in that the laser beam (9) is directed at an angle to the surface of the liquid material in the jet (1) between the end of the jet (1) and the information carrier (11). The ink-jet printing head according to claim 4, characterized in that the information carrier (11) is transparent for the wavelength radiated by the quantum generator (8) and placed in the path of the laser beam (9) to the surface of the liquid material in the jet (1).

Inventors: MAXIMOVSKY SERGEI NICOLAEVICH, RADUTSKY GRIGORY AVRAMOVICH, MAXIMOVSKY, SERGEI NICOLAEVICH, RADUTSKY, GRIGORY AVRAMOVICH
Applicants: MAXIMOVSKY SERGEI NICOLAEVICH, RADUTSKY GRIGORY A, MAXIMOVSKY, SERGEI NICOLAEVICH, RADUTSKY, GRIGORY AVRAMOVICH
Application year: 1995
Main classification: B41J2
IPC codes: B41J2