Plastic and nonmetallic article shaping or treating: processes – Laser ablative shaping or piercing
Reexamination Certificate
1998-06-11
2001-05-08
Silbaugh, Jan H. (Department: 1732)
Plastic and nonmetallic article shaping or treating: processes
Laser ablative shaping or piercing
C219S121710, C219S121730
Reexamination Certificate
active
06228311
ABSTRACT:
The present invention relates to methods and apparatus for forming a nozzle in a nozzle plate for an ink jet printhead, the nozzle having a nozzle inlet and a nozzle outlet in respective opposite faces of said nozzle plate.
W093/15911 concerns methods of forming nozzles in a nozzle plate for an inkjet printhead utilising a high energy beam, in particular the ablation of nozzles in a polymer nozzle plate using an excimer laser. By means of a mask having a single aperture, a high energy beam is shaped prior to being directed by a converging lens onto the surface of a nozzle plate where a nozzle is formed.
W093/15911 recommends increasing the divergence of the beam incident into the aperture of the mask by passing the beam through a layer such as a ground or etched surface or a thin film containing a medium having suitable light-scattering properties such as a colloid or opalescent material. Such a layer may be placed against a convergent lens which is itself located upstream of the mask for the purpose of focusing the beam into the aperture.
The divergence of the beam will determine the angle of taper of the nozzle. Furthermore, a second mask can be used to reduce the angle of divergence in one plane of the beam relative to another (both planes containing the beam axis), thereby to obtain a nozzle having a greater nozzle taper in one plane than in another. This will result in a nozzle inlet that is larger in one direction than in another direction perpendicular thereto —W093/15911 points out that this advantageously allows the nozzle ink inlet to match the (generally rectangular) shape of an ink channel in the printhead with which the nozzle will communicate, whilst allowing the nozzle outlet to remain preferably circular.
The present invention has as its objective improvements to the processes described in the aforementioned W093/15911, in particular to the manner in which the nozzle taper and the shape of the nozzle inlet and outlet are controlled.
According to a first aspect, the present invention comprises the method of forming a nozzle in a nozzle plate for an ink jet printhead, the nozzle having a nozzle inlet and a nozzle outlet in respective opposite faces of said nozzle plate, the method comprising the steps of:
directing a high energy beam towards said nozzle plate; introducing divergence into said beam; thereafter directing said beam at a single aperture of a mask, thereby to shape said beam; and thereafter passing said beam through beam converging means prior to impingement on the face of said nozzle plate in which said nozzle outlet is formed, thereby to form a nozzle, the nozzle outlet being conjugate through said beam converging means with said single aperture; wherein
the step of introducing divergence into said beam comprises splitting said beam into a number of sub-beams, each sub-beam having divergence, the origin of divergence of each sub-beam lying apart from the point at which the respective sub-beam is created by splitting; the sub-beams thereafter being passed through further beam converging means prior to being recombined and directed through said single aperture of a mask, wherein the dimensions of the section of said recombined beam directly prior to impinging the plane of said mask are substantially equal to the dimensions of the aperture in said mask.
The present invention includes the step of introducing divergence into said beam by splitting said beam into a number of sub-beams, each sub-beam having divergence, the origin of divergence of each sub-beam lying apart from the point at which the respective sub-beam is created by splitting, the sub-beams thereafter being passed through further beam converging means prior to being recombined. This arrangement allows substantially more accurate control of the angle of divergence of the beam than has been possible in prior art arrangements: as mentioned, W093/15911 proposes increasing the divergence of the high energy beam by scattering the light using a ground or etched surface or a thin film containing a medium having suitable light-scattering properties. It has been recognised in the present invention that divergence can be obtained in a much more controlled manner by splitting the high energy beam into a number of sub-beams which are subsequently recombined. Furthermore, the beam is split such that each sub-beam has divergence having an origin at a point lying apart from the point at which the respective sub-beam is created by splitting. It will be appreciated that the divergence obtained in this manner—which may be achieved using a lens to create each sub-beam —will be subject to substantially less variation than is achieved using prior art methods based on scattering. It follows that less variation in the angle of divergence of the combined beam will result in less variation in the angle of taper of the manufactured nozzles—resulting in better ink ejection performance of the final inkjet printhead.
Furthermore, by directing the recombined beam through a single aperture of a mask, with the dimensions of the section of the recombined beam directly prior to impinging the plane of said mask being substantially equal to the dimensions of the aperture in said mask, the high energy beam that finally impinges on the nozzle plate to form a nozzle does not have its divergence reduced by any significant amount by the mask. Consequently, the full range of beam divergence is available to form nozzle bores having a correspondingly high taper angle from outlet to inlet.
According to a second aspect, the invention comprises the method of forming a nozzle in a nozzle plate for an ink jet printhead, the nozzle having a nozzle inlet and a nozzle outlet in respective opposite faces of said nozzle plate, the method comprising the steps of:
directing a high energy beam towards said nozzle plate; introducing divergence into said beam; and thereafter passing said beam through beam converging means prior to impingement on said nozzle plate, thereby to form a nozzle; wherein
the step of introducing divergence into said beam comprises passing said beam through an array of optical elements to create an array of sub-beams, each sub-beam having divergence, the origin of the divergence of each sub-beam lying apart from the respective optical element; said array of sub-beams being thereafter directed towards first reflecting means for reflecting towards second reflecting means, said second reflecting means reflecting towards said nozzle plate; the positional relationship of said first and second reflecting means being such that a parallel beam impinging on said first reflecting means is reflected from said second reflecting means as a converging beam; the arrangement of said optical elements being such that all incoming sub-beams are directed by said first reflecting means towards said second reflecting means, thereafter to impinge on said nozzle plate.
This second aspect of the invention also utilises the concept of splitting (by means of an array of optical elements) a high energy beam into sub-beams having an origin of divergence lying apart from the plane of beam splitting and thereafter recombining the sub-beams through beam converging means. It therefore shares with the first aspect of the invention the advantage that the resulting angle of the beam can be accurately controlled.
In addition, the high energy beam is directed at the nozzle plate by means of first and second reflecting means and the optical elements in said array—e.g. lenses—are arranged such that all sub-beams impinging on the first reflecting means are directed towards the second reflecting means and not elsewhere e.g. back towards the array of lenses. This measure results in less wastage of the beam and furthermore avoids damage to other elements in the system by stray laser light. Such system elements may include lenses, turning mirrors and even the laser itself—located “upstream” of the first and second reflecting means.
A third aspect of the present invention comprises the method of forming a nozzle in a nozzle plate for an ink jet printhead, the nozzle h
Rumsby Philip Thomas
Temple Stephen
Marshall O'Toole Gerstein Murray & Borun
Silbaugh Jan H.
Staicovici Stefan
Xaar Technology Limited
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