JPH01190458A - Ink-jet head - Google Patents

Abstract

PURPOSE:To make it possible to jet ink drops in an effective manner and at a higher frequency, by determining the height of a projecting part formed on a substrate not less than the distance from the peripheral part of said projecting part to the lowest end of a slit nozzle plate, thereby to concentrate the pressure of vapor bubbles in the jetting direction of said ink drops. CONSTITUTION:A glaze layer 127 is formed in a protruding shape on a glass layer 126. A substrate 130 comprises a heat generating array 114 aligned on the surface of the glaze layer and a protective layer 110 which protects the heat generating array 114 and an electrode 112. A slit nozzle plate 106 has a slit nozzle aperture 120 formed at the confronting position to the heat generating array 114. Thus, the ink-jet head is constituted by the heat generating array 114, substrate 130 and slit nozzle plate 106. The gap h3 from the peripheral part of the protruding part on the substrate 130 to the lowest end of the slit nozzle plate 106 is set larger than the thickness h1 of the glaze layer 127, if desired. When the gap h3 is made larger, the fluid resistance of a recording ink 108 towards the slit nozzle aperture is reduced, and accordingly the recording ink 108 can be fed at higher speeds onto the surface of the heat generating array 114 after the ink drops are jetted out. Therefore, the ink-jet head can be driven with a high repeating cycle, thus improving the printing speed.

Description

[Detailed description of the invention] (Industrial application field) The present invention relates to an inkjet head.

(Prior Art) As one of the conventional inkjet recording methods, there is an inkjet recording apparatus (Japanese Patent Application Laid-Open No. 62-50150) that uses an ejection port substrate in which slit-shaped ejection ports are formed. A top view and a cross-sectional view of this inkjet head are shown in Figure 2 (
Shown in a) and (b).

In the inkjet head shown in FIGS. 2(a) and 2(b), by selectively energizing the heating element 307, the recording liquid 311 in the vicinity of the heating element is heated and vaporized into vapor 316, and the pressure generated by this state change is reduced. Due to the rise, the recording liquid starts to extend from the ejection port into a columnar shape. The vapor 316 is cooled, contracts, and disappears due to volumetric expansion and thermal conduction, and the recording liquid is separated from the ejection port and ejected as recording liquid droplets.

(Problem to be Solved by the Invention) However, in the conventional inkjet head equipped with a slit-shaped ejection port, the pressure generated by steam is transmitted in almost the same direction, so the flow of recording liquid is dispersed in the direction of the ejection port. don't concentrate on SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems and provide an inkjet head that concentrates pressure energy for ejecting ink droplets in the direction of the ejection port and ejects ink efficiently.

(Means for Solving the Problems) The inkjet head of the present invention includes a substrate having an elongated convex portion on its surface, a heating element array provided on the upper surface of the convex portion, and a slit at a position facing the heating element array. In an inkjet head comprising a slit nozzle plate provided with nozzle holes and provided to hold recording ink between the substrate and the substrate, the height hl of the convex portion is greater than the height hl of the slit nozzle plate from the upper surface other than the convex portion of the substrate. The inkjet head is characterized in that the distance to the lower end is h3 or more.

(Function) In the present invention, a convex portion is provided on the substrate, and
A heating element array is formed on the upper surface of the convex portion. The height of the convex portion is greater than or equal to the gap from the periphery of the convex portion to the lower end of the slit nozzle plate. The heating element array is then positioned inside the slit nozzle hole.

In this state, when vapor bubbles are generated on the resistor array, most of the pressure waves are directed toward the ink ejection direction either directly or by reflection on the side surface of the slit nozzle hole, so that the flow of recording ink is directed toward the ink jetting direction. It can be concentrated in the direction of the nozzle hole. Therefore, the pressure energy caused by the volume change of the vapor bubble can be efficiently used for ejecting ink.

(Example) Next, an example of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a sectional view showing the structure and operation of an embodiment of the present invention. In this embodiment, a glaze layer 1 is placed on the glass layer 126.
a substrate 130 comprising a heating element array 114 arranged in a convex manner on the surface of the glaze layer; a protective layer 110 for protecting the heating element array and the electrodes 112; It consists of a slit nozzle plate 106 with slit nozzle holes 120 formed at opposing positions. The recording ink 108 is held between the slit nozzle plate 106 and the substrate 130, and the recording ink 108 is held between the slit nozzle plate 106 and the substrate 130.
A meniscus is formed at 0. It is desirable that the cutting angle θ of the slit nozzle hole and the base angle θ2 of the glaze layer 127 be approximately equal. Then, the substrate 130
A part of the convex part can be made to fit into the slit nozzle plate with an approximately constant width of the ink flow path, so that the liquid resistance of the ink flow path does not increase locally, so that the ink droplet is Ink can be supplied quickly and smoothly.

In addition, the periphery of the convex portion on the substrate 130 and the slit nozzle plate 1
The gap h3 with the lower end of the glaze layer 127 can be set arbitrarily large depending on the thickness hl of the glaze layer 127.

When h3 is increased, the fluid resistance of the recording ink 108 toward the slit nozzle hole becomes smaller, and the speed at which the recording ink 108 is supplied onto the surface of the heating element array 114 after ejecting the ink droplets can be increased, and the repetition rate can be increased. It becomes possible to drive the head, improving printing speed. In this example, h3 was set to about several tens of pm to about 1100 p.

The distance from the heating element array 114 to the tip of the slit nozzle plate is set to a value h4 suitable for ejecting ink (for example, 50 pm to 1
It is desirable to set it to 0100p, and in this example, it is set to several tens of pm. The thickness h2 of the slit nozzle plate is h4
It can be any value above. As h2 increases, the slit nozzle plate becomes more resistant to external forces and pressure caused by steam bubbles, but the glaze layer 127
If the overlap h2-h4 between the ink droplet and the slit nozzle plate is not too large, the ink supply speed after ejecting ink droplets will increase, and the repetition cycle can be improved. Therefore, in this embodiment, - is set to h4+several tens of pm.

Further, the width W□ of the upper end of the slit nozzle hole 120 is several tens of
It was set as pm. As described above, as a result of setting h2, h3, h4, Wl, etc., it was possible to eject good ink droplets at a high repetition rate of ~10 kHz.

In this example, a silicon substrate or the like was used for the slit nozzle plate, and slit nozzle holes were formed by anisotropic etching with an etching solution such as KOH. The heating element array 114 is formed on the surface of the glaze layer 127 on the substrate 130 by a vapor deposition method, a sputtering method, or the like. As heating element materials, Ti, Mo, W
, Ta, and other silicides, carbides, borides, nitrides, etc. were used. Ceramics, glass, etc. were used for the glass layer 126 and the glaze layer. Further, the glaze layer 127 was formed by a generally known thick film technique, a photolithography technique using a photosensitive resin, or a photosensitive glass. The base angle θ2 of the glaze layer 127 was set to an angle at which a sputtered film and a vapor deposited film without disconnection of the electrode 112 could be formed.

(Effects of the Invention) As described in detail above, the inkjet head according to the present invention provides a convex portion on the substrate and makes the height of the convex portion equal to or greater than the distance from the periphery of the convex portion to the bottom end of the slit nozzle plate. The pressure energy generated by the bubbles can be concentrated in the direction of ink droplet ejection, allowing for efficient ink droplet ejection, as well as speeding up the supply of ink to the slit nozzle after ink ejection, making it possible to eject ink droplets at a higher repetition rate. did. Furthermore, it has become possible to create an inkjet head equipped with a slit nozzle plate that is thick enough to resist external forces and pressure caused by steam bubbles.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing the structure and operation of a first embodiment of the present invention, and FIG. 2 is a sectional view of a conventional example. In the figure, 130...Substrate 126...Glass layer 127...Glaze layer 112...Electrode 11
4... Heating element array 110... Protective layer 108
... Recording ink 104 ... Steam bubble 10
6...Slit nozzle plate

Claims (1)

[Claims] A substrate having an elongated convex portion on its surface, a heating element array provided on the upper surface of the convex portion, and a slit nozzle hole at a position facing the heating element array, and in order to hold recording ink between the substrate and the substrate. An inkjet head comprising a slit nozzle plate provided therein, wherein the height h_1 of the convex portion is greater than or equal to the distance h_3 from the upper surface of the substrate other than the convex portion to the lower end of the slit nozzle plate.