JP2010052316A - Image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an image forming apparatus capable of preventing clogging of nozzles and the like, suppressing the occurrence of printing defects and expanding the ink selection range.
A fluid lens is used as an acoustic lens 13 for ultrasonic focusing in an acoustic ink jet type image forming apparatus using a piezoelectric body 16 and causing ink to fly by ultrasonic waves generated by resonance of the piezoelectric body. . Further, the flying ink size is made variable by changing the focal position of the acoustic lens.
[Selection] Figure 2

Description

  The present invention relates to an acoustic ink jet type image forming apparatus in which ink is ejected by ultrasonic waves generated by resonance of a piezoelectric body.

  Conventionally, as this type of image forming apparatus, many apparatuses having various structures have been proposed. For example, an apparatus using a piezo method or a thermal ink jet method is known.

  For example, in this type of conventional apparatus, for example, a sound wave is generated from a sound wave generator, and the sound wave is focused by an acoustic lens made of an inorganic material such as glass or an epoxy resin, thereby causing ink droplets to fly. An apparatus having such a configuration is known (see, for example, Patent Document 1).

JP 2007-245632 A

  By the way, the above-described piezo method and thermal method have a problem that nozzle clogging is likely to occur and the frequency of occurrence of defective printing is high.

  Further, in the piezo method, it is necessary to form a complicated orifice structure, which increases the cost. On the other hand, in the thermal method, since heating with a heater in the head portion is necessary, it is necessary to take measures against the heat of the ink, resulting in a problem that the range of ink selection becomes narrow.

  Furthermore, in the above-described conventional apparatus, it is impossible to change the ink droplet size.

  The present invention has been made in view of such circumstances, and obtains an image forming apparatus capable of preventing clogging of nozzles and the like, suppressing the occurrence of defective printing, and expanding the ink selection range. With the goal.

  In order to meet such an object, the image forming apparatus according to the present invention (the invention according to claim 1) uses a piezoelectric body, and an acoustic ink jet type image in which ink is ejected by ultrasonic waves generated by resonance of the piezoelectric body. In the forming apparatus, a fluid lens is used as an acoustic lens for ultrasonic focusing.

  The image forming apparatus according to the present invention (the invention described in claim 2) is characterized in that, in claim 1, the flying ink size is made variable by changing the focal position of the acoustic lens.

  As described above, according to the image forming apparatus according to the present invention, in the acoustic ink jet system using ultrasonic waves, a fluid lens is used as an acoustic lens for focusing ultrasonic waves, so that a nozzle diameter larger than that in the past is used. This has an excellent effect that nozzle clogging does not occur.

  Further, according to the present invention, since the ink is not heated, the selection range of the ink is wide and the required printing performance can be obtained.

  Further, according to the present invention, the flying ink size can be changed by changing the focal position of the acoustic lens, and the print quality can be improved.

  1 to 5 show a first embodiment of an image forming apparatus according to the present invention. In these drawings, the image forming apparatus according to the present invention is based on an acoustic ink jet recording method, and ink is selected for recording paper. The recording pattern is created on the recording paper by flying it.

A schematic cross-sectional view thereof is shown in FIG.
This will be briefly described. This image forming apparatus is roughly composed of a paper feeding unit A, a recording unit B, and a paper discharge unit C.
The paper feeding unit A includes a paper feeding cassette 1 and a paper feeding roller 2, and supplies paper P to the recording unit B according to paper feeding data sent from a central processing unit (not shown).

  The recording unit B includes a conveyance roller A3, a conveyance roller B7, a platen roller 4, and a recording head 5. The recording head 5 employs a line type. Ink I flies from the recording head 5 toward the paper P in accordance with the print data, and recording is performed.

  The paper P that has been recorded by the recording unit B is directed to the paper discharge unit C by the rotation of the transport roller B7. In the paper discharge unit C, the paper P for which recording has been completed is stacked.

The configuration of the recording head 5 is shown in FIGS.
As shown in FIG. 2, the recording head 5 includes an oscillator 14 formed on the glass substrate 9 and an acoustic lens 13 and an upper plate disposed on the ink layer 10 side through the glass substrate 9 corresponding to the oscillator 14. 12 is comprised.

  This image forming apparatus is an acoustic ink jet system, and the ultrasonic wave generated by the vibrator 14 propagates through the glass substrate 9 and is focused by the acoustic lens 13, and the ink in the ink layer 10 is discharged from the opening 11 of the upper plate 12. Selectively fly.

  The opening 11 is sufficiently wider than the flying ink droplet size and does not have a function of controlling the ink droplet size. In the conventional thermal method and piezo-type ink jet, the nozzle diameter is very small as Φ20 μm and easily clogged. However, in the present invention, the opening 11 is about Φ50 μm, which is considerably larger than the conventional one, and the ink clogging occurs. There is no problem.

The configuration of the vibrator 14 and the acoustic lens 13 will be described with reference to FIGS.
The vibrator 14 includes a common electrode 17, a piezoelectric body 16, and a segment electrode 15. The piezoelectric body 16 is made of ZnO, PZT, or the like.

  The piezoelectric body 16 vibrates and generates ultrasonic waves by the electric field applied to the common electrode 17 and the segment electrode 15 according to the print data. For example, when a PZT film having a thickness of 6 μm is used for the piezoelectric body 16, the piezoelectric body 16 is driven by an AC electric field of 250 MHz Vpp20V. The generated ultrasonic wave is focused by the acoustic lens 13 through the glass substrate 9.

  The acoustic lens 13 is a liquid lens using electrowetting. The acoustic lens 13 has a cylindrical shape, and contains two kinds of solvents, a conductive aqueous solvent and a non-conductive oil, and the interface between the two solvents functions as a lens. Have

FIG. 5 shows a layout diagram of the acoustic lens 14.
FIG. 5 is a view from the vibrator 16 side, and is arranged at the intersection of the segment electrode 15 and the common electrode 17 so as to be the center of the acoustic lens 14.

  The acoustic lens 13 includes an electrode A18, an electrode B21, insulators 19 and 20, and a glass plate 22, and is sealed so that ink does not enter the inside. The inside of the acoustic lens 13 is subjected to water repellent treatment except on the glass substrate 9. A power supply device 23 is connected to the electrodes A18 and B21.

When no voltage is applied from the power supply device 23, the liquid state inside the acoustic lens 13 is water-repellent, so when the oil-based solvent 24 wets the wall surface, it is shown in FIG. It becomes a state like this. When a voltage is applied from the power supply device 23, the wettability inside the acoustic lens 13 changes, so that the water-soluble solvent 25 gets wet, and the interface forms a concave lens shape as shown in FIG. 4B.
By adjusting the voltage applied from the power supply device 23, the focal length of the acoustic lens changes.

  At the time of a normal print pattern, as shown in FIG. 6, adjustment is made so that ultrasonic waves are focused on the ink surface of the opening 11. A meniscus is formed by focused ultrasonic waves, and ink can be ejected to complete printing.

  When the focal position of the acoustic lens is shifted from the ink layer surface, the meniscus becomes larger than that in FIG. 7A when the focal point is aligned with the ink layer surface as shown in FIG. Also grows.

  In this manner, the flying ink droplet size can be varied by changing the focal position of the acoustic lens 13. This makes it possible to change the ink droplet size, which was not possible with the conventional piezo method or thermal ink jet method.

  In addition, if the viscosity and surface tension of the ink used change, the focal position can be adjusted and adjusted so that an appropriate flying ink droplet size can be obtained. Becomes wider and can be used for various media.

  Note that the present invention is not limited to the structure described in the above-described embodiment, and it goes without saying that the shape, structure, and the like of each part constituting the image forming apparatus can be appropriately modified and changed.

1 is a schematic cross-sectional view showing an embodiment of an image forming apparatus according to the present invention. FIG. 3 is a cross-sectional view of a main part showing a configuration of a recording head in the image forming apparatus according to the present invention. It is an expanded sectional view for demonstrating the structure of a vibrator | oscillator and an acoustic lens. (A), (B) is a figure for demonstrating the motion of the structure of FIG. FIG. 3 is a schematic plan view of FIG. 2. It is operation | movement explanatory drawing in the normal state by an acoustic lens. (A), (B) is a figure for demonstrating the variable state of a flying ink droplet size.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 5 ... Recording head, 6 ... Ink tank, 9 ... Glass substrate, 10 ... Ink layer, 11 ... Opening part, 12 ... Top plate, 13 ... Acoustic lens, 14 ... Vibrator, 15 ... Segment electrode, 16 ... Piezoelectric body, DESCRIPTION OF SYMBOLS 17 ... Common electrode, 18 ... Electrode A, 19 ... Insulator, 20 ... Insulator, 21 ... Electrode B, 22 ... Glass plate, 23 ... Power supply device, 24 ... Oil-type solvent, 25 ... Aqueous solvent.

Claims (2)

In an acoustic ink jet type image forming apparatus that uses a piezoelectric body and causes ink to fly by ultrasonic waves generated by resonance of the piezoelectric body,
An image forming apparatus using a fluid lens as an acoustic lens for ultrasonic focusing. The image forming apparatus according to claim 1.
An image forming apparatus, wherein a flying ink size is made variable by changing a focal position of the acoustic lens.

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