Method of forming an inkjet printhead nozzle structure

Details Method of forming an inkjet printhead nozzle structure Method of forming an inkjet printhead nozzle structure

1999-11-19

2002-06-25

Le, N. (Department: 2861)

Incremental printing of symbolic information

Ink jet

Ejector mechanism

C264S400000, C216S027000

Reexamination Certificate

active

06409308

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Technical Field of the Invention
The present invention relates to methods of forming one or more nozzles in a substrate used, for example, as a nozzle plate in a printhead of a thermal inkjet printer. More particularly, the present invention relates to a method of forming one or more nozzles in a substrate, wherein the nozzles are formed by laser ablation.
2. Description of the Related Art
Thermal inkjet printers operate by ejecting ink from a printhead onto a printable medium, such as paper. The printhead includes a plurality of nozzles formed in a substrate and arranged as a matrix such that, by ejecting ink only from preselected nozzles defining a predetermined pattern, the ejected ink will form an image, such as a letter, on the printable medium. The printhead further includes a heater chip provided with a plurality of resistive heating elements, one heating element positioned below each nozzle. Each nozzle is in fluid communication with an ink chamber formed in the printhead and sized to receive a small volume of ink therein. Upon heating the ink contained within the chamber to a temperature sufficient to vaporize the ink, an ink droplet is ejected from the chamber, through the nozzle, and onto the printable medium. Selectively heating only preselected heating elements, then, controls the pattern of ink being ejected from the printhead, and consequently, defines the image being formed on the printable medium.
As can be appreciated by one of reasonable skill in the art, text and other images are printed onto the printable medium by ejecting ink through predetermined combinations of preselected nozzles, which form the image onto the printable medium as a series of closely-spaced ink dots. It follows, then, that the closer the spacing between adjacent nozzles (and, hence, the closer the spacing between adjacent printed ink dots), the clearer and more continuous the appearance of the printed image. It is therefore desirable to provide a method of forming one or more nozzles in a substrate used, for example, as a nozzle plate in an inkjet printhead, wherein adjacent nozzles are spaced sufficiently close to one another to provide a clear and substantially continuous appearance to an image printed thereby.
However, it has been observed that, if the nozzles are spaced closely together and only a limited amount of material remains surrounding the nozzles, the remaining material may become damaged, for example, during a wash process typically used in thermal inkjet printers between print cycles. It is therefore desirable to provide a method of forming one or more closely-spaced nozzles in a substrate used, for example, as a nozzle plate in an inkjet printhead, wherein adjacent nozzles are formed such that sufficient material remains to support the nozzles.
One such method of forming a nozzle in a substrate used, for example, as a nozzle plate for an inkjet printhead, is known to those of reasonable skill in the art as laser ablation, whereby the substrate is positioned in the path of a laser beam emitted from a laser source. The laser beam penetrates the substrate and ablates material therefrom to form the nozzle thereby. It is to impart a predefined shape in the beam by interposing an opaque mask between the laser source and the substrate, wherein the opaque mask includes a transparent orifice having the predefined shape, through which the laser beam passes. The opaque portions of the mask block the remaining, peripheral, portions of the laser beam surrounding the orifice from penetrating the substrate and from ablating additional material therefrom. Accordingly, a nozzle is ablated in the substrate having a shape substantially similar to the shape of the orifice. It is therefore desirable to provide a method of forming one or more nozzles in a substrate used, for example, as a nozzle plate in an inkjet printhead, using laser ablation, wherein the cross-section of a laser used to ablate material from the substrate is defined by a mask interposed between a source of the laser and the substrate.
It is known in the art to use an opaque mask to simultaneously form more than one nozzle in a substrate useful, for example, as a nozzle plate of an inkjet printhead. For example, one or more orifices may be provided in the mask arranged in a preselected pattern, such as in the form of a matrix, and interposed between the source of the beam and the substrate. Projecting a beam onto the mask, then, separates the beam into a plurality of parallel, spaced-apart beam portions, each of which penetrates the substrate to form one nozzle. A matrix of nozzles are thus formed in the substrate. It is therefore desirable to provide a method of forming a plurality of nozzles in a substrate used, for example, as a nozzle plate in an inkjet printhead, using laser ablation, wherein an opaque mask is interposed between a source of the laser and the substrate, and wherein the mask includes a plurality of orifices arranged in a predetermined pattern to separate the laser into a plurality of beam portions.
It is also known in the art to impart a predefined tapered shape in the nozzle. For example, U.S. Pat. No. 5,417,897 to Asakawa, et al., teaches a method of forming tapered inkjet nozzles in a printhead layer, wherein a laser is passed through an orifice in an opaque mask, and wherein the periphery of the orifice includes partially opaque portions to reduce the intensity of the laser passing through the orifice near its periphery. The center of the laser penetrates the substrate at full intensity, completely ablating material from the substrate. The periphery of the laser, however, strikes the substrate at a reduced intensity insufficient to fully penetrate the substrate. Because the opacity of the orifice increases towards its periphery, the intensity of the laser passing therethrough decreases towards Its periphery and the depth to which the laser penetrates the substrate is reduced, thereby forming a nozzle with an inward taper such that the diameter of the nozzle where the laser enters the substrate is larger than the diameter of the nozzle where the laser exits the substrate. However, spacing of one or more nozzles arranged, for example, as a matrix on the substrate, is limited by the greater diameter of the nozzle formed on the surface of the substrate where the laser entered it, thereby limiting the minimum distance between which adjacent ink dots may be printed on the printable medium. It is therefore desirable to provide a method of forming one or more nozzles in a substrate used, for example, as a nozzle plate in an inkjet printhead, wherein spacing of adjacent nozzles Is optimized.
SUMMARY OF THE INVENTION
The present invention is for a method of forming one or more nozzles in a substrate used, for example, as a nozzle plate in an inkjet printhead of a thermal inkjet printer, using laser ablation. A partially-opaque mask is interposed between a source of a laser beam and the substrate and includes one or more ring-shaped orifices in an opaque coating layer thereof arranged in a closely-spaced matrix. The beam is emitted from the laser source towards the mask such that opaque portions of the opaque layer block the beam from passing through the mask except for through the ring-shaped orifices. The beam is thereby separated into one or more ring-shaped beam portions, each of which penetrates the substrate at approximately the same and substantially constant intensity to ablate one or more ring-shaped openings in the substrate arranged on the substrate as a closely-spaced matrix. Ring-spaced openings each defines a center plug portion, which is removed from the substrate, for example, by vacuum or adhesive.
According to one aspect of the present invention, a method of forming one or more nozzles in a polymeric material substrate is provided, comprising the steps of: providing a laser source adapted to emit a beam of laser energy along a path directed substantially towards the substrate; providing a mask having one or more openings surrounding one or more opaque mask port

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