KR20070018532A - Inkjet printhead having heat transfer layer - Google Patents

Abstract

A thermal drive inkjet printhead is disclosed. Disclosed is an inkjet printhead comprising: a substrate having a trench having a predetermined depth formed on an upper surface thereof; A plurality of heaters formed on the substrate; A plurality of conductors formed on the substrate to be electrically connected to the heaters; A chamber layer stacked on a substrate on which a heater and conductors are formed, the chamber layer having a plurality of ink chambers filled with ink to be discharged on top of the heaters; A nozzle layer laminated on the chamber layer and having a plurality of nozzles through which ink is ejected; And a heat transfer layer for dispersing heat generated from the heaters, the heat transfer layer being formed to cover the heater and the conductor between the substrate and the chamber layer and to fill the trench.

Description

Inkjet printhead with heat transfer layer

1 is a cross-sectional view schematically showing a conventional thermal inkjet printhead.

2 is a plan view schematically illustrating a thermally driven inkjet printhead according to an exemplary embodiment of the present invention.

FIG. 3 is an enlarged view of portion A of FIG. 2.

4 is a cross-sectional view taken along line IV-IV ′ of FIG. 3.

FIG. 5 is a cross-sectional view taken along the line VV ′ of FIG. 2.

<Description of the symbols for the main parts of the drawings>

100 ... Inkjet Printhead 101 ... Pad

110 ... substrate 111 ... ink feed hole

112. Insulation layer 114 ... Heater

116 ... conductor 118 ... protective layer

120 ... chamber layer 122 ... ink chamber

130 ... Nozzle Layer 132 ... Nozzle

132a, 132b, 132c, 132d ... nozzle heat 140 ... heat transfer layer

150 ... trench

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an inkjet printhead, and more particularly, to a thermally driven inkjet printhead capable of improving the ejection characteristics of ink by effectively dissipating excess heat generated from a heater.

In general, an inkjet printer is an apparatus for ejecting a small droplet of ink from an inkjet printhead to a desired position on a print medium to form an image of a predetermined color. Such inkjet printers include a shuttle-type inkjet printer which performs a printing operation while the inkjet printhead reciprocates in a direction perpendicular to the transport direction of the print media, and recently developed for high speed printing, which corresponds to the width of the print media. There is a line-printing inkjet printer with an array printhead of size. A plurality of inkjet printheads are arranged in a predetermined form in the array printhead. In such a line-printing inkjet printer, the print job is performed while only the print medium is transferred while the array printhead is fixed, thereby enabling high-speed printing.

On the other hand, inkjet printheads can be largely classified into two types according to the ejection mechanism of the ink droplets. One is a heat-driven inkjet printhead which generates bubbles in the ink by using a heat source and ejects the ink droplets by the expansion force of the bubbles, and the other is due to the deformation of the piezoelectric body using the piezoelectric body. A piezoelectric inkjet printhead which discharges ink droplets by a pressure applied to the ink.

The ink droplet ejection mechanism in the thermally driven inkjet printhead will be described in more detail as follows. When a pulse current flows through a heater made of a resistive heating element, heat is generated in the heater and the ink adjacent to the heater is instantaneously heated to approximately 300 ° C. Accordingly, as the ink boils, bubbles are generated, and the generated bubbles expand and apply pressure to the ink filled in the ink chamber. As a result, the ink near the nozzle is discharged out of the ink chamber in the form of droplets through the nozzle.

1 is a schematic cross-sectional view of a conventional thermally driven inkjet printhead. Referring to FIG. 1, a conventional inkjet printhead is a substrate 11 having a plurality of material layers stacked thereon, and is stacked on the substrate 11, the chamber layer 20 having an ink chamber 22 formed thereon, and the chamber. It consists of a nozzle layer 30 stacked on the layer 20. Ink is filled in the ink chamber 22, and a heater 13 is provided below the ink chamber 22 to generate bubbles by heating the ink. The nozzle layer 30 is provided with a nozzle 32 through which ink is ejected.

An insulating layer 12 is formed on the substrate 11 to insulate and insulate between the heater 13 and the substrate 11. On the insulating layer 12, ink in the ink chamber 22 is heated to form bubbles. A heater 13 for generating is formed. In addition, a conductor 14 for applying a current to the heater 13 is formed on the heater 13. A passivation layer 15 is formed on the surfaces of the heater 13 and the conductor 14 to protect them.

However, in the conventional inkjet printhead having the above structure, the excess heat other than the heat contributing to the ink ejection among the heat generated by the heater 13 is mainly emitted to the outside through the ink, thereby deteriorating the heat dissipation effect. Therefore, in the conventional inkjet printhead, a large amount of surplus heat generated from the heater 13 remains around the ink chamber 22, and the surplus heat remaining increases the temperature of the ink in the ink chamber 22 to increase the ink. It will change the viscosity of. In addition, such a change in viscosity of the ink lowers the discharge characteristics of the ink.

On the other hand, in recent years, development of line printing type inkjet printers has been actively developed according to the demand for high integration and high speed of the printhead. The inkjet printer of the line printing method is mainly an array printhead in which a plurality of inkjet printheads are arranged in a predetermined form. Since the array printhead has a larger number of heaters than the inkjet printhead used in a shuttle inkjet printer, There is a considerable amount of excess heat generated from the heater and remaining inside each inkjet printhead. Therefore, when the above-described conventional inkjet printhead is used for the array printhead, the discharge characteristics of the ink are further deteriorated. In order to solve this problem, it is necessary to disperse the excess heat other than the heat contributing to the ink discharge from the heater to the entire interior of the inkjet printhead or to quickly remove it through a heat sink.

The present invention has been made to solve the above problems, and an object of the present invention is to provide an inkjet printhead of a thermal drive type that can improve the ejection characteristics of ink by effectively dissipating excess heat generated from a heater.

In order to achieve the above object,

Thermal drive inkjet printhead according to an embodiment of the present invention,

A substrate having a trench of a predetermined depth formed on an upper surface thereof along an outer edge thereof;

A plurality of heaters formed on the substrate;

A plurality of conductors formed on the substrate to be electrically connected to the heaters to apply current to the heaters;

A chamber layer stacked on the substrate on which the heater and the conductors are formed, the chamber layer having a plurality of ink chambers filled with ink to be discharged on the heaters;

A nozzle layer stacked on the chamber layer and having a plurality of nozzles through which ink is ejected; And

And a heat transfer layer formed between the substrate and the chamber layer to cover the heater and the conductor and to fill the trench at the same time to dissipate heat generated from the heaters.

An insulating layer for insulating between the heater and the substrate is formed on the upper surface of the substrate, and a protective layer may be formed on the surfaces of the heater and the conductor.

The substrate is preferably attached to a heat sink for dissipating heat transferred to the substrate through the heat transfer layer to the outside.

The heat transfer layer may be formed to a thickness of 3㎛ or more, the heat transfer layer may be made of Ag.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. Like reference numerals in the drawings refer to like elements, and the size or thickness of each element may be exaggerated for clarity.

FIG. 2 is a plan view schematically showing a thermal inkjet printhead according to an exemplary embodiment of the present invention, and FIG. 3 is an enlarged view of portion A of FIG. 4 is a cross-sectional view taken along line IV-IV ′ of FIG. 3, and FIG. 5 is a cross-sectional view taken along line VV ′ of FIG. 2.

The thermally driven inkjet printhead according to an embodiment of the present invention described below may be applied to not only an inkjet printhead used in a shuttle type inkjet printer but also an array printhead used in a line printing type inkjet printer. In the array printhead, the inkjet printhead according to the present embodiment is more useful for the array printhead because a large amount of excess heat is generated from the heaters because the inkjet printhead is arranged in plural.

2 to 5, the inkjet printhead according to the embodiment of the present invention, for example, when forming a color image of cyan (C), magenta (M), yellow (Y) and black (K) Four nozzle rows 132a, 132b, 132c, and 132d for discharging ink are formed. Here, the number of nozzle rows 132a, 132b, 132c, and 132d may be variously modified. A plurality of pads 101 are provided at both edges of the inkjet printhead to be electrically connected to the conductors 116. The inkjet printhead is driven by receiving an electrical signal from a main body (not shown) of the printer through the pads 101.

Looking at the vertical structure of the inkjet printhead according to an embodiment of the present invention, a chamber layer having a plurality of ink chambers 122 filled with ink of a predetermined color to be discharged onto the substrate 110 on which the insulating layer 112 is formed ( 120 is stacked, and a nozzle layer 130 having a plurality of nozzles 132 through which ink is discharged is formed on the chamber layer 120. The nozzles 132 are arranged in a predetermined form to form the aforementioned nozzle rows 132a, 132b, 132c, and 132d.

In general, a silicon substrate is used as the substrate 110. An insulating layer 112 for insulating between the substrate 110 and the heater 114 is formed on the upper surface of the substrate 110. The insulating layer 112 may be made of silicon oxide (SiO _x ). Here, a plurality of ink feed holes 111 for supplying ink to the ink chambers 122 are formed in the substrate 110 on which the insulating layer 112 is formed. In addition, as illustrated in FIG. 2, a predetermined depth trench 150 is formed along the outer surface of the substrate 110.

A plurality of heaters 114 for generating bubbles by heating ink in the ink chamber 122 are formed on a top surface of the insulating layer 112 in a predetermined shape. In addition, a conductor 116 for applying a current to the heater 114 is formed on the upper surface of the heater 114 to be electrically connected to the heater 114. Here, the heat generating portion of the heater 114, that is, the heater 114 exposed through the conductor 116 is located under each ink chamber 122. The passivation layer 118 is formed on the surfaces of the heaters 114 and the conductors 116. The protective layer 118 may be formed of silicon nitride (SiN _x ) or silicon oxide (SiO _x ). In the present exemplary embodiment, the protective layer 118 may not be formed on the surfaces of the heater 114 and the conductor 116.

Meanwhile, on the insulating layer 112 of the substrate 110 on which the heater 114, the conductor 116, and the protective layer 118 are formed, the heat transfer layer 140 dispersing the remaining heat around the heater 114 after ink discharge. It is formed in this predetermined thickness. Here, the heat transfer layer 140 is formed to surround the periphery of the ink chambers 122 formed in the chamber layer 120. The heat transfer layer 140 extends to the outside to fill the trench 150 formed at a predetermined depth on the upper surface of the substrate 110 as shown in FIG. 5. Accordingly, heat generated from the heater 114 after the ink is discharged while being transferred toward the substrate 110 through the heat transfer layer 140. Here, the heat transfer layer 140 is preferably made of a material having excellent thermal conductivity. For example, the heat transfer layer 140 may be made of Ag. In this case, the heat transfer layer 140 may be formed by patterning an Ag paste. In this case, when the Ag paste is a photosensitive material, the Ag paste is patterned by a lithography process. If the paste is a non-photosensitive material, the Ag paste may be patterned using screen printing or a TSI (Top Surface Imaging) process. In addition, the heat transfer layer 140 is preferably formed to a thickness of about 3㎛ or more so as to exhibit a sufficient heat transfer effect.

The chamber layer 120 is stacked on the insulating layer 112 of the substrate 110 to cover the heat transfer layer 112. Here, the ink chambers 122 are formed in the chamber layer 120 so as to be positioned above the heat generating portion of the heater 114, and in the ink chambers 122, ink supplied from the ink feed hole 111 may be used. Will be filled. The nozzle layer 130 formed by penetrating the nozzles 132 is stacked on the chamber layer 120. Here, the nozzles 132 may be formed at positions corresponding to the centers of the ink chambers 122.

In the thermally driven inkjet printhead as described above, the remaining heat remaining around the heater 114 in addition to the heat contributing to the ink discharge among the heat generated by the heater 114 is transferred to the substrate 110 through the heat transfer layer 140. Are quickly distributed towards In addition, in order to more effectively discharge the heat remaining around the heater 114 to the outside, the lower surface of the substrate 110 of the inkjet printhead may be attached to a heat sink. Accordingly, heat dispersed toward the substrate 110 through the heat transfer layer 140 may be quickly released to the outside through the heat sink. Here, the heat sink may be a ceramic plate, a metal plate, or the like. On the other hand, in the array printhead, a plurality of inkjet printheads are attached on the heat sink.

As described above, in the heat-driven inkjet printhead according to the present invention, in addition to the heat contributing to the ink ejection among the heat generated from the heater 114, surplus heat remaining around the heater 114 is transferred through the heat transfer layer 140. By dispersing toward the substrate 110 or being discharged to the outside through a heat sink, heat remaining around the heater 114 after ink discharge may be quickly removed. Accordingly, it is possible to prevent the lowering of the discharge characteristic of the ink due to thermal accumulation in the inkjet printhead.

Although the preferred embodiment according to the present invention has been described above, this is merely illustrative, and those skilled in the art will understand that various modifications and equivalent other embodiments are possible. Therefore, the true technical protection scope of the present invention will be defined by the appended claims.

As described above, according to the present invention, by forming a heat transfer layer made of a material having good thermal conductivity around the heater and the ink chamber, the excess heat remaining around the heater after ink discharge is effectively dispersed to the substrate or externally through a heat sink. Can be released. As a result, it is possible to prevent heat from accumulating around the heater, thereby improving ink ejection characteristics. In addition, the inkjet printhead according to the present invention having the heat transfer layer as described above may be more usefully applied to an array printhead having a large number of heaters and generating a great amount of heat.

Claims (5)

A substrate having a trench of a predetermined depth formed on an upper surface thereof along an outer edge thereof; A plurality of heaters formed on the substrate; A plurality of conductors formed on the substrate to be electrically connected to the heaters to apply current to the heaters; A chamber layer stacked on the substrate on which the heater and the conductors are formed, the chamber layer having a plurality of ink chambers filled with ink to be discharged on the heaters; A nozzle layer stacked on the chamber layer and having a plurality of nozzles through which ink is ejected; And A heat transfer layer for dissipating heat generated from the heaters, the heat transfer layer formed between the substrate and the chamber layer to cover the heaters and the conductors and at the same time filling the trenches; Inkjet printheads. The method of claim 1, An insulating layer for insulation between the heater and the substrate is formed on the upper surface of the substrate, and a protective layer is formed on the surface of the heater and the conductor. The method according to claim 1 or 2, And the substrate is attached to a heat sink for dissipating heat transferred to the substrate to the outside through the heat transfer layer. The method according to claim 1 or 2, The heat transfer layer is a thermal inkjet printhead, characterized in that formed in a thickness of 3㎛ or more. The method according to claim 1 or 2, The heat transfer layer is a thermal inkjet printhead, characterized in that made of Ag.

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