JP2009226807A - Inkjet print head - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an inkjet print head which attains the high density of a head section, stable flying of ink, and improvement in recorded print and recording quality. <P>SOLUTION: By utilizing a thermal capillary action, an ink liquid surface is moved to the propagation surface of an SAW 3, and the SAW is caused to enter there, thereby causing a minute ink to fly. At that time, by providing an ink supply part with a heating means (heater 9) and an ink passage 7 for each pixel, an ink drop is caused to fly selectively according to image information, thus recording on a recording medium. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an ink jet print head that ejects ink using surface acoustic waves (SAW).

  2. Description of the Related Art Conventionally, ink jet printer heads using surface acoustic waves as a driving source for ink droplet flight have been proposed. This uses the phenomenon that liquid is added to the surface of propagation of surface acoustic waves, the surface acoustic waves are radiated into the liquid, and the excitation output is increased to cause the liquid to fly as fine particles. It is.

  In such a conventional inkjet print head, the nozzleless method is roughly divided into a case where one comb-like electrode (IDT) is provided for each pixel (see, for example, Patent Document 1), and a large IDT as a drive source. This is classified as a case where a small IDT for pixel control is provided (for example, see Patent Document 2).

Japanese Patent Laid-Open No. 10-193592 JP-A-4-189145

  However, in the above-described ink jet print head of Patent Document 1, it is said that the IDT crossing width is required to be three or more wavelengths, and when one IDT is provided for each pixel, this becomes a bottleneck, and there is a limit to high density. .

  In addition, when a large IDT and a small IDT for pixel control are provided as drive sources, as in the ink jet print head of Patent Document 2, there is a limit to the minimum value of the intersection width of the IDT for pixel control. Along with this, there is a limit to densification.

  In general, LiNb03 having a large electromechanical coupling coefficient is used as the piezoelectric material, but the sound speed thereof is about 4000 m / second, and the wavelength is 80 μm even when operated at a high speed of 50 MHz. Therefore, considering an IDT having a crossing width of 3 wavelengths, the pitch is 240 μm or more, and only a print head corresponding to 100 dpi can be realized.

  The present invention has been made in view of such circumstances, so that the density of the head portion can be increased with the simplest possible configuration, and the ink can be stably ejected to perform the required recording and printing. In addition, an object is to obtain an ink jet print head capable of improving the recording quality.

  In order to meet such an object, the present invention (the ink jet print head according to the first aspect of the present invention uses the thermal capillary phenomenon to move the ink liquid surface to the SAW propagation surface and make the SAW incident thereon. As a result, the minute ink is ejected, and the ink supply section is formed with the ink flow path and the heating means for each pixel so that the ink droplets are selectively ejected according to the image information and recorded on the recording medium. It is characterized by comprising.

  An ink jet print head according to the present invention (the invention according to claim 2) is the ink jet print head according to claim 1, wherein the member constituting the ink supply section is formed by using a hydrophilic material or is provided with a hydrophilic coating. In addition, the inner wall of the ink channel and the inner surface of the top plate are made hydrophilic, and the surface that comes into contact with the piezoelectric substrate is provided with a water-repellent coating so that the ink that has propagated through the channel does not ooze into the adjacent channel. It is characterized by.

  The ink jet print head according to the present invention (invention of claim 3) is the ink print head according to claim 1 or claim 2, wherein when the heater is turned off during non-printing, the ink liquid surface in each ink flow path is rectangular by the pressure regulator. The pressure of the ink chamber is adjusted so as to be positioned in the vicinity of the tip of the tubular flow path portion.

  The ink jet print head according to the present invention (the invention according to claim 4) is the ink jet print head according to claim 1, 2 or 3, wherein the length of the ink flow path portion without the top plate in the ink flow path is set to the SAW wavelength. It is characterized by being 8 times or more.

  As described above, according to the ink jet print head according to the present invention, in the ink jet system using SAW as a driving force for ink droplet flight, the ink is selectively selected according to image information using the thermal capillary phenomenon (Marangoni effect). Since the printing is performed by supplying it to the SAW propagation surface, despite the simple structure, the density of the head portion is increased and the ink is stably ejected to perform the required recording printing. It is possible to improve the recording quality.

  In particular, according to the present invention, it is possible to control ink supply at a low voltage of about 20 V, to enable required recording printing, and to improve recording quality.

  In addition, according to the present invention, a fine flow path can be easily formed by etching or MEMS technology, and further, an individual heater can also be formed by a printing method process, so that the density can be easily increased. Has an excellent effect.

1 and 2 show an embodiment of an ink jet print head according to the present invention.
In these figures, reference numeral 1 denotes a piezoelectric substrate (generally LiNb03) is used as a propagating body, and a wide comb-shaped interdigitated electrode (IDT) 2 is formed on the piezoelectric substrate 1 (propagation surface). One or a plurality are formed, and are configured by adhering the end surfaces to the base material. Note that an AC generator is connected to the IDT 2.
Reference numeral 3 denotes a surface acoustic wave (SAW) that propagates on the propagation surface of the piezoelectric substrate 1.

  Reference numeral 5 denotes an ink supply unit disposed in contact with the end of the piezoelectric substrate 1, and includes an ink chamber 6, and an individual ink flow path 7 corresponding to the pixel from the ink chamber 6 is formed in a rectangular tubular shape. . Then, the pressure adjusted by a pressure regulator (not shown) is transmitted to the ink chamber 6 through a tube or the like, and adjusted so that the ink liquid level in each individual ink flow path 7 is positioned near the tip of the rectangular tubular portion. It is like that.

  Reference numeral 8 denotes a flow path top plate provided so as to cover a part of the individual ink flow path 7 on the ink chamber 6 side in the ink supply unit 5, and a portion corresponding to each flow path 7 of the flow path top plate 8. The heater 9 is provided individually. Reference numeral 10 denotes an individual control SW for individually turning on / off these heaters 9. In addition, 7a is a rectangular tubular flow path part, 7b is a top plate-less flow path part.

  Here, a hydrophilic material is used for the members constituting the ink supply unit 5, and the inner wall of the flow path 7 and the inner surface of the top plate are made hydrophilic. A hydrophilic coating may be applied to provide a similar configuration. However, the end surface in contact with the piezoelectric substrate 1 is provided with a water-repellent coating so that the ink propagating through the flow path 7 does not ooze into the adjacent flow path 7.

When the ink droplets are caused to fly according to the image information, the individual control Sw10 is short-circuited and the rectangular tubular flow path portion 7a is heated by the heater 9. Then, the surface tension of the heated portion is reduced (also referred to as thermocapillary phenomenon or Marangoni effect), ink flows out to the flow path portion (7b) without the top plate 8, and reaches the SAW propagation surface.
The heater 9 can be heated with a low voltage power source of about 20 V using a general thin film heater.

  Then, for example, when SAW 3 excited at 50 MHz and 30 to 50 Vpp is incident on the SAW 3, the SAW 3 is converted into a longitudinal wave inside the ink liquid, and the longitudinal wave flies in the Rayleigh angle direction as a minute droplet of ink, and beyond. Is recorded on the recording medium placed in

  Further, when the heater 9 is turned off and the temperature of the rectangular tubular channel portion 7a decreases, the surface tension returns to the original state, and the ink that has flowed out is pulled back.

  In order to control the flying of the ink droplets by moving the ink through the top plate-less channel portion 7b, this distance should be short, but this portion is also a region where the SAW 3 performs mode conversion into a longitudinal wave. In addition, the SAW 3 needs to sufficiently penetrate into the ink liquid, and it is necessary to ensure 8 wavelengths or more.

  Therefore, when the SAW generating part is constituted by the LiNb03 substrate 1 and excited at 50 MHz as described above, the wavelength of the SAW 3 is 80 μm, and therefore the length of the top plate-less channel part 7b is 640 μm or more.

  According to the ink jet print head having such a configuration, ink supply control can be performed at a low voltage of about 20V. Furthermore, fine channels can be easily formed by etching or MEMS technology, and individual heaters can also be formed by a printing method process, so that the density can be easily increased.

  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 inkjet print head can be appropriately modified and changed.

For example, in the above-described embodiment, the cross-sectional shape of the flow path 7 is rectangular, but is not limited thereto, and may be a semicircular shape, a semi-elliptical shape, or the like.
In addition, in the ink flow path 7, a modification in which the flow path width of the flow path 7 corresponding to the heater 9 provided on the flow path top plate 8 is formed to be narrow is also conceivable.

1 is a schematic exploded perspective view showing an embodiment of an ink jet print head according to the present invention. FIG. 2 is a plan view, a front view, a left side view, and a right side view showing an assembled state of the ink jet print head of FIG. 1.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Piezoelectric substrate (propagating body), 2 ... Interstitial electrode (IDT), 3 ... Surface acoustic wave (SAW), 5 ... Ink supply part, 6 ... Ink chamber, 7 ... Individual ink flow path, 8 ... Flow path ceiling Plate, 9 ... heater, 10 ... individual control SW.

Claims (4)

Using the thermal capillary phenomenon, the ink liquid surface is moved to the SAW propagation surface, and the SAW is incident on the ink liquid surface to fly the micro ink,
An ink jet comprising: an ink flow path and a heating unit for each pixel formed in an ink supply unit, whereby ink droplets are selectively ejected according to image information and recorded on a recording medium. Print head. The inkjet printhead of claim 1.
By forming a member constituting the ink supply unit using a hydrophilic material or applying a hydrophilic coating, the inner wall of the ink flow path and the inner surface of the top plate are made hydrophilic,
An ink jet print head characterized in that a water repellent coating is applied to a surface in contact with a piezoelectric substrate so that ink that has propagated through a flow path does not ooze into an adjacent flow path. The inkjet printhead according to claim 1 or 2,
Inkjet printing characterized in that when the heater is turned off during non-printing, the pressure in the ink chamber is adjusted by a pressure regulator so that the ink liquid level in each ink flow path is located near the tip of the rectangular tubular flow path portion head. The ink jet print head according to claim 1, 2 or 3,
An ink jet print head characterized in that the length of the ink flow path portion without the top plate in the ink flow path is at least 8 times the wavelength of SAW.

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