JP3159232B2 - Ink jet recording device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for receiving an ink ejected from a nozzle opening on a recording sheet, or receiving the ink once on an intermediate medium to form an image, and transferring the ink to the recording sheet when the ink has dried to some extent. The present invention relates to an ink jet recording apparatus such as a transfer type, and more particularly to a cleaning technique for preventing clogging of a recording head.

[0002]

2. Description of the Related Art A pressure generating chamber, a nozzle communicating with the pressure generating chamber, and a pressure generating element for inducing a pressure change in the pressure generating chamber are assembled. Ink-jet printers, which supply print data to generate ink droplets and fly them on recording paper to perform printing, have less moving parts than wire-impact printers, so they have lower noise and are smaller. Although it has the feature of being lightweight, it has an inconvenience that, since an image is formed on recording paper using ink that is a liquid, bleeding occurs depending on the paper quality of the recording paper, leading to a decrease in print quality. In order to solve such a problem, for example, as shown in U.S. Pat. No. 4,538,156, ink droplets from an ink jet type recording head are once received by an intermediate medium formed in a drum shape or a band shape, and to a certain extent here. There has also been proposed a transfer-type inkjet printer configured to transfer an ink solvent to recording paper after volatilizing the ink solvent. The use of such a transfer method is characterized in that the occurrence of bleeding can be prevented irrespective of the quality of ink or recording paper, and a high-quality printed matter can be obtained.

[0003] In such an apparatus that reliably transfers an ink image formed on such an intermediate medium to recording paper, it is necessary to print one page of print data in a short time, and it is necessary to print the data in a lengthwise direction in the recording paper. Since the configured recording head is used, the capping means for preventing drying of the nozzle openings also becomes longer. However, there is a problem that a drive mechanism becomes complicated to securely attach a large-sized capping means to the recording head.

[0004]

SUMMARY OF THE INVENTION The present invention has been made in view of such a problem, and an object of the present invention is to prevent ink from drying in nozzles without the need for capping means. It is to provide a new ink jet recording apparatus capable of performing the above.

[0005]

According to the present invention, there is provided a pressure generating chamber which communicates with a nozzle opening and contains ink capable of forming a film, and an ink droplet is supplied to the pressure generating chamber. An ink jet recording head having pressure generating means for giving a change in pressure to fly, a head driving means for driving the pressure generating means so as to generate ink droplets at a speed suitable for printing, and the nozzle for discharging non-ink droplets In the vicinity of the nozzle opening of the plate at room temperature or higher,
And it was so and a heating means for heating to a temperature sufficient to form a film on the ink.

[0006]

The meniscus of the nozzle opening is rapidly heated by the heating means because the nozzle plate is extremely thin and the area of the nozzle opening is small. As a result, the ink near the nozzle opening forms an extremely thin film, and the evaporation of the ink solvent on the pressure generating chamber side is prevented. When the pressure generating means is operated in a state where the film is formed, the film is blown off together with the ink droplets under the pressure from the pressure generating chamber, the nozzle opening is fully opened, and the meniscus for discharging the ink droplets necessary for printing is formed. To form

[0007]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. FIG. 1 shows an embodiment of the present invention. In FIG. 1, reference numeral 1 denotes a recording head for ejecting ink droplets toward an intermediate medium to be described later, and a plurality of nozzle openings are arranged in the width direction of the recording paper. The recording paper is formed in a long shape so that a plurality of dots can be formed in the width direction of the recording paper by one ink droplet ejection operation.

That is, FIG. 2 shows an embodiment of the recording head 1 described above. Reference numeral 11 in the figure denotes a nozzle plate, which is a nozzle plate having a width sufficient to cover the area of the maximum width of the recording paper. Approximately 2,000 openings 12 are arranged in a zigzag shape while being shifted in a straight line or vertically. A plurality of nozzles, for example, 400 nozzles are arranged in a row direction at a pitch of a plurality of dots, for example, at an interval of 5 dots, and the recording head is moved by one dot for each rotation of the transfer drum 3, which will be described later. For example, a recording head capable of forming an image for one page by five rotations can be used.

Numeral 13 is a spacer which has through holes so as to form pressure generating chambers 14, 14, 14 # arranged at equal intervals in the horizontal direction when set in the printer so as to separate adjacent nozzle openings. It is constructed by drilling. Reference numeral 15 denotes a vibration plate, a portion facing the pressure generating chamber 14 being formed as a thin portion, and supported by an ink supply member 16. 17
Is a piezoelectric vibrator formed by forming electrodes and a piezoelectric vibration material in a sandwich shape so as to generate vibration in a longitudinal vibration mode at a drive voltage as low as possible.
The same number as that of 2, 12 mm is fixed to the base 18,
The tip is arranged so as to contact the diaphragm 15. When the piezoelectric vibrator 17 receives a driving signal, the piezoelectric vibrator 17 can supply an energy enough to cause the ink droplet to collide with the surface of the transfer drum 3 at a speed of about 6 m / s or more. A mode is provided in which energy can be supplied to the extent that droplets can be ejected. This mode may be the same as the above mode.

In order to smoothly supply ink to the entirety of the long recording head 1, the recording head 1 is connected to an ink tank 6 by ink passages 4 and 5 such as tubes, and is controlled by an on-off valve 7 and a pump 8. The ink is supplied from the ink tank 6 in a circulating manner, and the ink is supplied to the pressure generating chamber 14 via the ink supply paths 19, 19. In addition, since the recording head 1 is configured to be long, the recording head 1 is mounted on the holding member 9 and provided at the other end by rotating the driving means 20 in the direction C in the drawing. It is configured to reciprocate in a small amount in the directions indicated by reference symbols G and F in the drawing, that is, in the paper width direction in cooperation with the spring 21 to change the ejection position of the ink droplet.

Reference numeral 3 denotes an intermediate medium for receiving the ink droplets from the above-described recording head 1. In this embodiment, the intermediate medium is formed as a drum having a length enough to receive the ink droplets from the recording head. A silicone rubber layer is provided so that the formed ink image can be easily transferred to recording paper. Further, it is connected to a motor 24 via transmission mechanisms 22 and 23, and is configured to rotate at a constant speed in the direction of arrow H in FIG. Reference numeral 25 denotes a pressing roller, which is supported by a bearing above the intermediate medium 3 and is disposed so as to be capable of coming into contact with and separating from the transfer medium 3. When an ink image is formed on the intermediate medium 3, the recording paper 26 is moved by springs 27, 27. It is configured to press in the direction indicated by the symbol I in the drawing by the repulsive force.

By the way, as shown in FIG. 3, a heating device 30 is arranged near the recording head 1 so as to be able to move up and down to a position facing the nozzle opening. The heating device 30 has a capability of raising the temperature of the nozzle openings 12 of the recording head 1 to a temperature at which ink forms a film, in this embodiment, approximately 40 to 80 ° C. Reference numeral 60 in the figure denotes a cleaning device that is driven by the pulse motor 61 and cleans the nozzle openings of the recording head 1 along the guide member 62.

FIG. 3 mainly shows the above-mentioned heating device. In the drawing, reference numeral 30 denotes the above-mentioned heating device, which accommodates a heating wire therein and radiates heat to the vicinity of the nozzle opening of the nozzle plate. It is configured for rapid heating. The lower end of the recording head 1 is attached to the lifting mechanism 32,
And a position that does not hinder the ink droplets from reaching the intermediate medium.

Numeral 34 denotes a halt determining means for determining a point in time when the printing operation is brought into a halt state by a signal from the control device 35 and outputting a signal to a temperature control means 36 and a raising / lowering means 37 which will be described later. . The temperature control means 36 adjusts the temperature of the heater so that the temperature in the vicinity of the nozzle opening becomes a temperature suitable for ink film formation, and the elevation control means 37 controls heating by a signal from the pause determination means 34. The device 30 is moved up and down to a position facing the nozzle opening, and when the film is formed, the heating device 30 is retracted from the nozzle opening. Reference numeral 38 in the drawing denotes a head driving unit that outputs a signal for causing the recording head 1 to generate ink droplets.

In this embodiment, when a print command is input from an external device, the transfer drum 3 is rotationally driven by the motor 24 in the direction indicated by the symbol H in the drawing. When the transfer drum 3 reaches the steady speed, a drive signal sufficient to generate ink droplets for printing on the corresponding piezoelectric vibrator 17 in accordance with the print data is supplied from the head drive means 38. As a result, ink droplets are ejected from the recording head 1, and an ink image having a mirror image relationship with an image to be printed is formed on the transfer drum 3. When the transfer drum 3 makes one rotation in this way, a signal is output to the driving means 20 and the recording head 1 is moved in the paper width direction.
For example, an ink image is formed at a position corresponding to the print data by moving a predetermined distance in the direction F in FIG.

At the stage when the ink image corresponding to the print data is formed on the transfer drum 3, the recording paper 26 is supplied from a paper cassette (not shown) to a transfer area, that is, below the pressing roller 25. The recording paper 26 is pressed against the transfer drum 3 by 27 and 27. As a result, the recording paper 26 is sent out at the moving speed of the ink image that has become semi-dry on the surface of the transfer drum 3, and the ink image is transferred onto the recording paper 26 by its adhesive force.

When the printing of the predetermined print data is completed, a signal is output from the pause determination means 34, and the elevation control means 37 causes the heating device 30 to face the nozzle opening of the recording head 1 (FIG. 3). At the position indicated by the dotted line in FIG.
Supplies power. When the heating device 30 that has generated heat to a predetermined temperature in this way faces the nozzle opening, the nozzle plate 11 receives the radiant heat from the heating device 30. Needless to say, the nozzle plate 11 has a thickness of 50 to 100 μm.
4, the temperature rises rapidly to almost the same temperature as the heating device 30 (FIG. 4).
I). The diameter of the nozzle opening 12 is 30 to 60 μm.
Since the temperature is extremely small, such as about m, the temperature of the meniscus formed here rises rapidly due to the conduction heat from the nozzle plate and the radiant heat from the front heating device. For this reason, for example, when the ink is composed of a pigment 1.5 wt%, a sugar content 20 wt%, a resin emulsion 15 wt%, a surfactant 3 wt%, a diethylene glycol 6 wt% water and the remainder, the ink solvent on the surface of the meniscus evaporates rapidly. The emulsion is first formed into a film, and a film is formed by incorporating sugar into the emulsion. As a result, an extremely dense film is formed (II in FIG. 4).

That is, as shown in FIG. 5, for example, when the temperature of the heating device 30 is set to 80 ° C., the temperature of the surface of the nozzle plate 11 becomes almost the same as this temperature instantaneously. Is maintained at the same low temperature as during the printing operation. In the initial stage of the heating, the temperature gradient with respect to the distance to the pressure generating chamber side is extremely large, and the temperature gradient becomes gentle with time. When the temperature of the heating device 30 is set so that the surface temperature of the nozzle plate 11 becomes 40 ° C., the temperature gradient with respect to the distance becomes small. Then, the higher the surface temperature of the nozzle plate 11, the greater the temperature gradient with respect to the distance.

For this reason, the temperature of the nozzle plate 11 is raised to a certain degree, preferably about 10 to 15 ° C. higher than the ambient temperature, that is, to such an extent that a temperature gradient is generated between the front and back surfaces of the nozzle plate 11. When the temperature is set, only the vicinity of the nozzle opening is heated to an extremely high temperature in a short time, so that a thin film is formed. When the film grows to a certain thickness (several tens of μm), the film prevents evaporation of the ink solvent. Then, it was confirmed that the film thickness hardly changed even when the temperature rise region proceeded to the pressure generating chamber side.

After the predetermined time has elapsed, the elevation control means 37 lowers the heating device 30 to evacuate the heating device 30 from a position facing the recording head 1, and the temperature control means 36 cuts off the electric power. Since the film 41 is a film in which the emulsion and the sugar constituting the ink are formed into a film, the film 41 is highly airtight and prevents evaporation of the solvent of the ink present on the pressure generating chamber side from the film 41 (FIG. 4 III). ).
If left in this state, the film 41 prevents the evaporation of the ink, and even if a very small amount of the ink solvent evaporates and the ink concentration near the film 41 increases, the solvent is supplied by diffusion. The density of the ink inside is kept constant. Therefore, it is possible to prevent the ink from evaporating from the nozzle openings even when the ink cartridge is left without any particular cap.

Next, when a signal to the extent that ink can be ejected is applied to the piezoelectric vibrator 17 for printing, a pressure sufficient to eject ink to the pressure generating chamber 14 is generated as in the printing operation. As described above, since the film 41 formed in the nozzle opening 12 is extremely thin, the adhesive force with the nozzle plate 11 is extremely small, and the tensile strength and hardness of the film 41 are large. Ink droplets 42 that cannot withstand pressure and are ejected
At the same time, the entire film 41 is blown off (FIG. 4IV). As a result, the nozzle opening 12 is fully opened, and the meniscus 40 can be formed after the ejection of the ink droplets, so that subsequent printing can be performed as before the film formation.

On the other hand, when the heating device is not used as described above, the above-mentioned temperature gradient is not formed, and the ink solvent gradually evaporates, so that the formed film becomes thicker. Since the solvent content is high, it has a large adhesive force to the nozzle opening. For this reason, it was not possible to discharge the film together with the ink from the nozzle openings with the energy supplied to the piezoelectric vibrator for printing. In order to eliminate this state, it has been necessary to remove by applying mechanical means such as so-called cleaning means.

From this, it can be seen that heating the nozzle plate to a temperature higher than room temperature to actively form an ink film is not only a substitute for the capping means but also an extremely effective means for preventing clogging. It could be confirmed.

In the above embodiment, a heating means for forming a film is provided separately. However, in order to promote drying of an ink image formed on the transfer drum 3 as in a transfer type ink jet printer, for example, FIG. In the case where the transfer drum 3 has a built-in heater 50 as shown in FIG. 3 or a heater is provided in the vicinity of the transfer drum, these existing heaters are used as heating means for forming a film. It is apparent that the same operation is obtained even if the temperature is controlled so as to be a temperature necessary for film formation.

In this embodiment, the transfer type ink jet recording apparatus has been described as an example. However, it is apparent that the present invention can be applied to a recording apparatus of a type in which ink is directly ejected onto recording paper. Obviously, the same effect can be obtained even when applied to a recording head of a serial printer that performs printing while scanning in the width direction of the recording paper. Further, in this embodiment, the pressure for forming the ink droplets is generated by the piezoelectric vibrator. However, the present invention is applied to a so-called bubble jet type ink jet recording apparatus which instantaneously vaporizes the ink and generates ink droplets at the time of impact pressure. Obviously, the same effect is obtained even when the above-mentioned operation is performed.

[0026]

As described above, according to the present invention, a pressure generating chamber which communicates with a nozzle opening and stores ink capable of forming a film, and a pressure generating chamber which applies a pressure change which causes an ink droplet to fly into the pressure generating chamber. Means, an ink jet recording head having means, a head driving means for driving a pressure generating means so as to generate ink droplets at a speed suitable for printing, and the vicinity of the nozzle opening of the nozzle plate at the time of non-ink droplet ejection at room temperature or higher, And heating means for heating the ink to a temperature sufficient to form a film on the ink, so that when the nozzle opening is heated by the heating means at rest, the ink near the nozzle opening solidifies extremely thinly to form a film and generate pressure. Constituting cap means for preventing evaporation of the ink solvent on the chamber side,
Further, when the pressure generating means is operated in a state where the film is formed, the pressure is applied from the pressure generating chamber, the film is blown off together with the ink droplets and the cap is removed, so that the cap means and the attaching / detaching means for the cap means are unnecessary. It can be.
Then, the film forcibly formed in this manner can be removed from the nozzle opening with the same energy as that at the time of printing.
It can also be used as a means for preventing clogging.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of an apparatus showing one embodiment of the present invention.

FIG. 2 is a view showing one embodiment of an ink jet recording head used in the above apparatus.

FIG. 3 is a configuration diagram showing one embodiment of the present invention.

FIGS. 4A to 4C are explanatory diagrams showing the operation of the above device.

FIG. 5 is a diagram showing a temperature distribution near a nozzle opening;

FIG. 6 is a configuration diagram showing another embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Ink jet recording head 3 Transfer drum 11 Nozzle plate 12 Nozzle opening 14 Pressure generating chamber 25 Press roller 30 Heating device 40 Meniscus 41 Ink film

Claims (8)

(57) [Claims] An ink jet recording head having a pressure generating chamber communicating with a nozzle opening and containing ink capable of forming a film, and a pressure generating means for applying a pressure change for causing an ink droplet to fly into the pressure generating chamber; a head drive means for driving the pressure generating means to generate ink droplets at a speed suitable for printing, the nozzle opening near the nozzle plate to an ink non-ejection at normal temperature or higher, and to form a film on the ink an ink jet recording device including a heating means for heating to a temperature, a sufficient to. 2. An ink jet recording apparatus according to claim 1, wherein said heating means is provided so as to be able to advance and retreat in an ink droplet ejection path. 3. A plurality of pressure generating chambers communicating with the nozzle openings and containing ink capable of forming a film, and pressure generating means for applying a pressure change for causing ink droplets to fly in the pressure generating chambers are provided in the width direction of the recording paper. An ink-jet recording head disposed , a transfer medium for receiving ink droplets from the ink-jet recording head, pressing means for pressing recording paper against the transfer medium, and generating ink droplets at a speed suitable for printing a head drive means for driving the pressure generating means as a heating means for heating to a temperature sufficient to the nozzle opening near the nozzle plate to an ink non-ejection at normal temperature or higher, and to form a film on the ink, the An ink jet recording apparatus provided. 4. An ink jet recording apparatus according to claim 3, wherein said heating means is provided so as to advance and retreat in an ink droplet ejection path. 5. The ink jet recording apparatus according to claim 3, wherein said heating means is contained in said transfer medium. 6. The ink jet recording apparatus according to claim 1, wherein the ink capable of forming a film contains a resin emulsion and a sugar. 7. The ink jet recording apparatus according to claim 1, wherein the film is formed of a resin emulsion and a sugar. 8. The apparatus according to claim 1, wherein the rubber can be removed from the nozzle opening by driving the pressure generating means.
Or the ink jet recording apparatus according to claim 3.