Print head and fabrication method thereof

Abstract

A printer head is provided that enhances energy efficiency of a heater layer and substantially prevents heat from being excessively transmitted to ink in an ink chamber, thereby improving ink-ejecting performance and/or printing performance. A method of fabricating such a printer head is also provided. The print head includes a substrate having an ink chamber and a nozzle disposed in the top thereof, an insulating layer layered on the substrate, and a heater layer layered on the insulating layer. A heat transmitting part transmits heat to the ink chamber. The insulating layer is formed so that a portion thereof that faces the heat transmitting part of the heater layer has a thickness larger than that of the rest of the insulating layer.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other objects, features, and advantages of certain exemplary embodiments of the present invention will be more apparent from the following description taken in conjunction with the accompanying drawings, in which:

FIG. 1 is an elevational view in cross section of a conventional print head;

FIG. 2 is an elevational view in cross section view of a lower structure of a print head in accordance with an exemplary embodiment of the present invention;

FIG. 3 is an elevational view in cross section of a lower structure of a print head in accordance with another exemplary embodiment of the present invention; and

FIG. 4 is a graph exemplifying a comparison result between a mean temperature of bulk ink in the print head according to an exemplary embodiment of the present invention and that in the conventional print head.

Throughout the drawings, the same drawing reference numerals will be understood to refer to the same elements, features, and structures.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

The matters defined in the description, such as a detailed construction and elements thereof, are provided to assist in a comprehensive understanding of the exemplary embodiments of the invention. Accordingly, those of ordinary skill in the art will recognize that various changes and modifications of the exemplary embodiments described herein may be made without departing from the scope and spirit of the invention. Also, descriptions of well-known functions and constructions are omitted for clarity and conciseness.

Referring to FIG. 2 and/or FIG. 3 exemplifying print heads in accordance with exemplary embodiments of the present invention, a print head 200 includes a substrate 210, an insulating layer 220, a heater layer 230, a wire layer 240, and a protecting layer 250.

The substrate 210 may be formed by machining a silicon wafer, which is mainly used as a semiconductor element, to a thickness of approximately 400˜650 μm.

As illustrated in FIGS. 2 and 3, the insulating layer 220 is formed so that it has an uneven (or non-uniform) thickness. A portion of the insulating layer 220 that faces a heat transmitting part 232 of the heater layer 230, which is described later, has a thickness different from that of the other portion of the insulating layer 220.

Preferably, but not necessarily, the insulating layer 220 is formed so that the portion of the insulating layer 220 that faces the heat transmitting part 232 of the heater layer 230 has a thickness larger than that of the other portion of the insulating layer 220, thereby allowing heat generated from the heater layer 230 to be more efficiently transmitted into an ink chamber 270 and substantially blocking heat generated from the heater layer 230 from being transmitted to the substrate 210 from the heat transmitting part 232.

Additionally, the insulating layer 220 is formed so that a portion of the insulating layer 220 that faces a current applying part 231 of the heater layer 230, which is described later, has a thickness smaller than that of the portion of the insulating layer 220 that faces the heat transmitting part 232, thereby allowing a portion of the heat generated from the heater layer 230 to be radiated into the substrate 210 through the current applying part 231 of the heater layer 230.

That is, with the insulating layer 220 having the uneven thickness, the print head according to exemplary embodiments of the present invention substantially prevents heat from being excessively transmitted into the ink in the ink chamber 270, so that ink in the ink chamber 270 is not overheated. Accordingly, ink in the ink chamber 270 may maintain a viscosity adapted for ejection, thereby substantially preventing ink ejecting performance and printing performance from being deteriorated.

Such an insulating layer 220 may be formed in a shape illustrated in FIG. 2 by depositing an oxide, such as SiO₂, on an upper surface the substrate 210 or by oxidizing a portion of the upper surface of the substrate 210, and then patterning the deposited oxide or the oxidized portion with an etching method, such as a dry etching or a wet etching.

Additionally, the insulating layer 220 may be formed in a shape illustrated in FIG. 3 by oxidizing a portion of the upper surface of the substrate 210 with a sacrificing layer oxidization method.

The heater layer 230 is disposed on an upper surface of the insulating layer 220. The heater layer 230 has a current applying part 231 and a heat transmitting part 232. The current applying part 231 has a wire layer 240 (described below) layered on an upper surface thereof, so that it receives electric current through the wire layer 240. The heat transmitting part 232 does not have the wire layer 240 thereon, so that it transmits generated heat directly to the ink chamber 270.

The heater layer 230 may be configured so that, as illustrated in FIG. 2, the insulating layer 220 has uneven thickness, and the heat transmitting part 232 is positioned at a height above the current applying part 231. Alternatively, as illustrated in FIG. 3, the heat transmitting part 232 is positioned at a height identical to or similar to that of the current applying part 231.

Such a heater layer 230 may be formed by depositing a heat resistant material, such as TaN, TaAl, TiN or tungsten silicide, on an upper surface of the insulating layer 220, and then pattering the deposited heating resistant material.

The wire layer 240 is disposed on an upper surface of the current applying part 231 of the heater layer 230, and is made of a metal to apply the electric current to the heater layer 230.

Such a wire layer 240 is formed by depositing a metallic material having good conductivity, such as Al and the like, on a portion of an upper surface of the heater layer 230. A portion of the deposited metallic material that faces the heat transmitting part 232 of the heater layer 230 is then patterned with an etching method and the like.

The protecting layer 250 is disposed on upper surfaces of the wire layer 240 and the heater layer 230, and substantially prevents the wire layer 240 and the heat transmitting part 232 of the heater layer 230 from being oxidized or coming in contact with ink in the ink chamber 270.

Such a protecting layer 250 may be formed by depositing a silicon nitride SiN₄ and the like with a Plasma-enhanced chemical vapor deposition (PECVD) method.

Additionally, a cavitation prevention layer (not illustrated) may be formed on the protecting layer.

The following table 1 illustrates a plurality of characteristic values for forming bubbles, each of which is divided into that of the print head according to exemplary embodiments of the present invention and that of the conventional print head. The insulating layer 220 according to exemplary embodiments of the present invention was formed so that a portion thereof that faces the heat transmitting part 232 of the heater layer 230 has a thickness of 1.8 μm and the remaining portion thereof has a thickness of 0.3 μm.

TABLE 1
	Exemplary embodiments	The conventional
Item	of the present invention	example
Pulse width (μs)	0.6	0.6
Amount of electric power	2.0	2.0
(W/m)
Time for till bubble comes	0.78	0.78
to maximum size (μs)
Inputted electric energy (μJ)	1.2	1.2
Tb (° C.)	287.3	287.3
Critical bubble forming	7989	7990
energy (μJ)
Temperature increasing rate	2.1E+8	2.1E+8
of heater for forming
bubbles (° C./sec)

The inputted electric energy means an electric energy value inputted into the heater layer to form bubbles in ink. Tb means a surface temperature of the heater layer at a point of time when bubbles begin to form in the ink. The critical bubble forming energy means a minimum energy that is transmitted to the ink from the heater layer to form bubbles.

As illustrated in the above Table 1, it may be appreciated that in the print head according to exemplary embodiments of the present invention, the entire characteristic values including the inputted electric energy, and so forth, maintain almost unchanged as compared with those of the conventional print head, even though the insulating layer 220 was formed having an uneven thickness.

FIG. 4 is a graph exemplifying a comparison of the results between a mean temperature of bulk ink embodied by the print head according to exemplary embodiments of the present invention and that embodied by the conventional print head. The bulk ink means ink contained in the ink chamber.

As illustrated in FIG. 4, it may be appreciated that with the passage of time, an overheating temperature stands at approximately 97° C. in the bulk ink of the conventional print head, but approximately 80° C. in the bulk ink of the print head according to exemplary embodiments of the present invention, so that the print head according to exemplary embodiments of the present invention obtains a temperature decreasing effect of approximately 18° C.

Thus, it may be appreciated that with the insulating layer 220 having uneven thickness, the print head according to exemplary embodiments of the present invention maximally restrains the heat generated from the heat transmitting part 232 of the heater layer 230 from being excessively transmitted to the ink chamber 270.

As apparent from the foregoing description, according to the exemplary embodiments of the present invention, the print head and the fabrication method thereof enhance the energy efficiency of the heater layer and substantially prevent the heat from being excessively transmitted to the ink chamber, thereby improving the ink-ejecting performance and/or the printing performance.

While the invention has been shown and described with reference to certain exemplary embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims.

Claims

1. A print head, comprising: a substrate having an ink chamber and a nozzle disposed in the top thereof;an insulating layer layered on the substrate; anda heater layer layered on the insulating layer, and having a heat transmitting part to transmit heat to the ink chamber,wherein the insulating layer has a non-uniform thickness.

2. The print head of claim 1, wherein the insulating layer is formed so that a portion thereof that faces the heat transmitting part has a thickness larger than that of a remaining portion of the insulating layer.

3. The print head of claim 1, wherein the heater layer is formed so that the heat transmitting part has a height different than that of another portion of the heater layer.

4. The print head of claim 1, wherein the heater layer is formed so that the heat transmitting part has substantially the same height as that of another portion of the heater layer.

5. The print head of claim 1, wherein the insulating layer has a raised floor formed on a portion thereof that faces the heat transmitting part.

6. A print head, comprising: a substrate;a chamber layer disposed at the upper side of the substrate, and having an ink chamber;an insulating layer layered on the substrate;a heater layer layered on the insulating layer, and having a heat transmitting part;a wire layer layered on the heater layer to apply current to the heater layer; anda protecting layer layered on the wire layer and the heater layer,wherein the insulating layer has a non-uniform thickness.

7. The print head of claim 6, wherein the insulating layer is formed so that a portion thereof that faces the heat transmitting part has a thickness larger than that of a remaining portion of the insulating layer.

8. The print head of claim 6, wherein the heater layer is formed so that the heat transmitting part has a height different than that of another portion of the heater layer.

9. The print head of claim 6, wherein the heater layer is formed so that the heat transmitting part has substantially the same height as that of another portion of the heater layer.

10. The print head of claim 6, wherein the insulating layer has a raised floor formed on a portion thereof that faces the heat transmitting part.

11. A method of fabricating a print head, comprising the steps of forming an insulating layer having a non-uniform thickness on a substrate; andforming a heater layer on the insulating layer after the insulating layer is formed on the substrate.

12. The fabrication method of claim 11, wherein the insulating layer is formed so that a portion thereof that faces a heat transmitting part of the heater layer has a thickness larger than that of a remaining portion of the insulating layer.

13. The fabrication method of claim 11, wherein the heater layer is formed so that the heat transmitting part has a height different than that of another portion of the heater layer.

14. The fabrication method of claim 11, wherein the heater layer is formed so that the heat transmitting part has the same height as that of another portion of the heater layer.

15. A print head, comprising: a substrate;an ink chamber to store ink;a nozzle to eject ink from the ink chamber;an insulating layer having a non-uniform thickness layered on the substrate;a heater layer layered on the insulating layer and having a heat transmitting part to transmit heat to the ink chamber and a current applying part to apply current to the heat transmitting part; anda wire layer layered on the heater layer to apply current to the current applying part of the heater layer.

16. The print head of claim 15, wherein the insulating layer is formed so that a portion thereof that faces the heat transmitting part has a thickness larger than a portion of the insulating layer that faces the current applying part.

17. The print head of claim 15, wherein the heater layer is formed so that the heat transmitting part has a height different than that of the current applying part of the heater layer.

18. The print head of claim 15, wherein the heater layer is formed so that the heat transmitting part has substantially the same height as that of the current applying part of the heater layer.

19. The print head of claim 15, wherein the insulating layer has a raised floor formed on a portion thereof that faces the heat transmitting part.

20. The print head of claim 15, wherein a protecting layer is layered on the wire layer and the heater layer.