RU2051043C1 - Thermojet printing head - Google Patents

Abstract

FIELD: information output. SUBSTANCE: to reduce amount of labor in manufacturing thermojet printing head, raise its working frequency, improve the standard of fastening of the plate with nozzles to the resistive board and to control the volume of the ink drop, there are partitions provided between the ink and nozzle chambers, said partitions determining the length of the channel therebetween. The design makes it possible to vary the length, width and height of the channel. The closed thin-walled partition and the stiffener ribs form the preset dimensions of the nozzle and ink chambers and provide for their tightness over the parameter. EFFECT: improved design. 2 cl, 5 dwg

Description

 The invention relates to paper output devices.

 Known thermostatic print head with thin-film resistors, a dielectric coating of resistors with a polymeric material forming the nozzle and ink chambers, a plate with nozzles (Ronald A. Askeland, Winthrop D. Childers, and William R. Sperry. The Second Generation Thermal Inkjet Structure. Hewlett-Packard Journal. August 1988, p. 28-31).

 Such a constructive version of the head allows obtaining a resolution of up to 300 dpi with high print quality, but is laborious in manufacturing a board with resistors, namely, it is necessary to introduce a number of operations in the technology related to the deposition and processing of polymer material with a thickness of 25-50 μm depending on the design of the thermal inkjet print head. In this case, the plate with nozzles does not have an additional relief, except for nozzle holes. The increase in frequency is achieved through the use of a substrate with high thermal conductivity, such as silicon.

 In the proposed head design, a thick polymer coating on the resistive board and the associated technological operations are eliminated, and the nozzle and ink chambers are formed by electroforming in a plate with nozzles without increasing its complexity in comparison with the analogue. The relief created on the periphery of the plate with nozzles can improve the quality of gluing by increasing the thickness of the adhesive film.

 The closest in design is the thermal inkjet head, which has thin-film resistors with a dielectric coating, a relief plate with nozzles. The nozzle plate has relief on the inner and outer surfaces (Ronald A. Askeland, Winthrop D. Childers, and William R. Sperry. The Second Generation Thermal Inkjet. Structure. Hewlett Packard Journal, August 1988, p. 28-31).

 The main disadvantage of this head design is the low resolution (not more than 180 dpi) due to imperfect design of nozzle and ink chambers made on a relief plate with nozzles. For the manufacture of a plate with nozzles, a matrix of metal with a relief height of up to 50 μm is required, which determines the high complexity of manufacturing.

 The aim of the invention is to eliminate these drawbacks, obtaining high resolution and reducing the complexity of manufacturing, increasing the operating frequency and improving the quality of connecting the plate with nozzles to the resistive board.

 In FIG. 1 shows a portion of a matrix with resistors and a chamber-forming plate with nozzles; in FIG. 2, section AA in FIG. 1; in FIG. 3 plate with nozzles from the inner surface; in FIG. 4 a section BB in FIG. 3; in FIG. 5 a section CC of FIG. 3.

 The head contains a plate with nozzles 1, on which there is a closed thin-walled partition 2, a partition 3 between the nozzle and ink chambers, an ink supply channel 4 to the nozzle chamber 5, an ink chamber 6, an adhesive chamber 7, a resistive layer 8, a protective coating 9, conductive tires 10, dielectric substrate 11, ink supply channel 12 from the ink tank into the ink chamber, stiffeners 13.

 As shown in FIG. 2-5, the inner surface of the plate with nozzles has a closed thin-walled partition 2, which forms an ink and nozzle chamber when gluing the plate to the board with resistors. This partition separates the nozzle chambers 5 from each other, and each of them has a channel into the ink chamber 6. The chambers for glue 7 are separated from each other by stiffeners 13, which can be made as a continuation of the thin-walled partition 2 with the same or lower relief height, may have a gap with a partition 2. In addition, they can be closed along the perimeter of the plate with additional ribs or be open, as shown in FIG. 3. The partition 2 limits the flow of glue to the nozzle and ink chambers.

 The proposed plate designs with nozzles are selected depending on the adhesive used and the gluing method.

 The configuration of the ribs may be different depending on the size of the plate with nozzles and the number of nozzles.

 Thermostatic print head operates as follows.

 To the resistive substrate 8 through the supply bus 10, a pulse voltage with an amplitude of 18-22 V, with a duration of 2-7 μs and a frequency of 1.3-1.8 kHz (i.e., the standard power mode of the thermojet heads) is supplied. In each of these time periods, thermal energy is released in the ink nozzle chamber 5. Due to this, ink boils in the chamber. The process of boiling ink is accompanied by the formation of gas bubbles that are ejected together with the dye (ink) through the nozzle of the chamber 5. In the intervals (in the pauses) between the pulses, the dye is fed from the ink chamber 6 connected by the ink supply channel 12 to the ink reservoir (not shown).

 The droplet volume of the generated ink, which affects the resolution, depends on the size of the nozzle chambers 5 and the holes in it, on the size of the partition 3 between the nozzle and ink chambers, on the quality of gluing the plate to the resistive board. In the proposed design, the dimensions of the partition between the nozzle and ink chambers 3 determine the length and cross section of the channel 4 connecting them. The dimensions of the partition 3 are set by the template. Control of the dimensions of the partition in three coordinates allows you to choose the most suitable option to ensure the required characteristics of the head.

 Obtaining a relief in a plate with nozzles allows one to increase the frequency characteristics by reducing the constant cooling time of the ink in the nozzle chamber after the passage of a heat pulse.

 A distinctive feature of the plate is that it has a relief only on the inside and a microrelief on the outside, which can reach no more than five microns and is determined by the thickness of the dielectric and matrix conductors used in electroplating. In the prototype, the relief is formed on both sides, and in the analogue it is absent.

 The plate with nozzles is made by electroforming. An oxide layer with a thickness of up to 1 μm is grown on a silicon substrate with a resistivity of less than 0.003 Ω cm.

 Windows are opened in the oxide layer for the formation of a thin-walled partition 2 and stiffeners 13. The current supply through the silicon substrate allows the formation of sections of any configuration with equal height. Next, a metal with a thickness of 0.5 μm, for example nickel with a sublayer of adhesive material, is sprayed onto the substrate. Another photomask is photolithography on metal so that between the first pattern and the second there are gaps formed by silicon oxide, which acts as a dielectric. The width of this gap determines the thickness of the step, which is obtained during the galvanic growth of the plate. The electrolyte is chosen such that the growth rate along the plate is equal to the growth rate perpendicular to the plate. Due to these gaps, an ink chamber 6, a partition 3 between the nozzle and ink chambers, glue chambers 7, the configuration of the nozzle chambers 5 are formed.

 Thus, a matrix is formed for the manufacture of plates with nozzles. After special processing of the matrix, it is placed in a plating bath to build up a nickel layer of the required thickness. Next, a block of plates that are connected by jumpers is removed from the matrix. This technology allows you to get plates without jumpers, because current is supplied through the substrate.

 The wafer with nozzles obtained by the above technology has a microrelief (up to 1.5 μm) on the side of the build-up on a silicon wafer with oxide and metal. The height of the microrelief is equal to the thickness of the oxide and metal. The height of the relief on the inside of the plate is determined by the design of the formed gaps on the dielectric.

 The use of the design of a thermal inkjet print head with a nozzle plate, discussed above, allows obtaining heads with a resolution of 300 dpi with a reduction in the cost of its manufacture with dosing of the droplet and an increase in the frequency characteristics. Improving the basic characteristics of the head allows you to perform resistive substrates on a material such as glass instead of silicon, which, in turn, reduces the cost.

 All this makes it possible to increase the percentage of yield of suitable products and reduce the time of development of heads in mass production.

Claims (2)

 1. THERMOJET PRINTING HEAD, containing a plastic case, an ink tank, a plate with nozzles, a board with resistors, conductive tires and a protective coating, characterized in that, in order to obtain high resolution and reduce the complexity of manufacturing, increase the operating frequency and quality of plate attachment with nozzles to the resistive board, a closed thin-walled partition is formed on the inner surface of the plate, separating the nozzle and ink chambers from the peripheral areas of the plate, peripheral domain divided into sectors stiffeners in the form of beams extending from a thin-walled partitions to the perimeter of the nozzle plate.  2. The head according to claim 1, characterized in that, in order to limit the volume of the generated droplets of ink, between the ink and each of the nozzle chambers there is a partition forming the height, width and length of the channel between them.

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