Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
  • B41J—TYPEWRITERS; SELECTIVE PRINTING MECHANISMS, i.e. MECHANISMS PRINTING OTHERWISE THAN FROM A FORME; CORRECTION OF TYPOGRAPHICAL ERRORS
  • B41J2/00—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed
  • B41J2/005—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed characterised by bringing liquid or particles selectively into contact with a printing material
  • B41J2/01—Ink jet
  • B41J2/135—Nozzles
  • B41J2/16—Production of nozzles
  • B41J2/1621—Manufacturing processes
  • B41J2/1632—Manufacturing processes machining
  • B41J2/1634—Manufacturing processes machining laser machining
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
  • B41J—TYPEWRITERS; SELECTIVE PRINTING MECHANISMS, i.e. MECHANISMS PRINTING OTHERWISE THAN FROM A FORME; CORRECTION OF TYPOGRAPHICAL ERRORS
  • B41J2/00—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed
  • B41J2/005—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed characterised by bringing liquid or particles selectively into contact with a printing material
  • B41J2/01—Ink jet
  • B41J2/135—Nozzles
  • B41J2/16—Production of nozzles
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
  • B41J—TYPEWRITERS; SELECTIVE PRINTING MECHANISMS, i.e. MECHANISMS PRINTING OTHERWISE THAN FROM A FORME; CORRECTION OF TYPOGRAPHICAL ERRORS
  • B41J2/00—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed
  • B41J2/005—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed characterised by bringing liquid or particles selectively into contact with a printing material
  • B41J2/01—Ink jet
  • B41J2/135—Nozzles
  • B41J2/16—Production of nozzles
  • B41J2/162—Manufacturing of the nozzle plates

Definitions

• the present invention relates to inkjet printheads, and in particular to the production of inkjet nozzles and other instances where removal of material from elements of inkjet printheads is required. Such material can usefully be removed, at least in part, by ablation.
• ablation also known as photoablative decomposition
• both the adhesive layer and backing tape are removed from those areas where the nozzles are formed.
• a similar adhesive layer and backing tape arrangement is known from W093/22141.
• EP-A-0 367 541 further discloses an alternative arrangement in which no adhesive layer is employed.
• the nozzle plate is carried on a backing layer and the face of the nozzle plate which is to be bonded to the print head body is covered by a protective layer. Ablation takes place through this protective layer which is removed prior to the bonding process.
• the document proposes using a thicker non- wetting coating, ablating it with the aid of a covering layer so as to achieve a satisfactory nozzle shape.
• EP-A-0 309 146, W092/16822 and W093/15911 - belonging to the same applicant as the present invention - also relate to ablation in the context of inkjet printheads.
• All three documents disclose methods of removing material from an element of an inkjet printhead - in this case a nozzle plate - using a laser beam which impinges on a surface forming or intended to form part of the external surface of the printhead - in this case a surface having a non-wetting coating. Since, in these examples, the laser beam does not ablate the non-wetting coating from the rear, the above- mentioned problem with the non-wetting coating being blown away does not occur.
• the originators of the present invention have encountered problems with damage to that surface which is intended to form part of the external surface of the printhead.
• the damage has impaired the performance of the nozzle.
• the originators of the present invention believe that the damage is caused by high energy free radicals and other highly reactive chemical species, liberated during the ablation process, diffusing back onto that surface intended to form part of the external surface of the printhead.
• the present invention allows the damage referred to above to be avoided.
• a method of removing material from an element of an inkjet printhead said element including an ablatable material and having a surface intended to form part of the external surface of the printhead, the method being characterised by the steps of: a) applying a protective layer to be in sealing engagement with said surface; b) directing a high energy beam at said protective layer from that side of said element to which said protective layer is applied, thereby removing material from said protective layer and said element having said surface, at least part of the material removed from said element being removed by ablation; c) removing said protective layer from said surface.
• Applying a protective layer to be in sealing engagement with that surface intended to form part of the external surface of the printhead effectively protects the surface, in particular at the periphery of the zone in which material removal takes place.from the high energy free radical ablation products discussed above.
• the protective layer may be releasably bonded to said surface, advantageously by the use of an adhesive layer.
• an adhesive layer may be transparent to the high energy beam. Removal of the adhesive layer can then take place by the action of the high-energy radicals generated during the ablation of material lying beneath the adhesive layer, for example the material of the nozzle plate.
• the adhesive layer is itself ablatable.
• the UV absorbing characteristic may be an intrinsic property of the adhesive or may be achieved by the use of a UV absorbing additive.
• the protective layer this also may be transparent to the high-energy beam but will advantageously comprise ablatable material. This will allow the protective layer to be removed by the high energy beam during the material removal process and yet be of sufficient thickness that it will effectively protect the surface from the effects of high energy radicals as described above. Where the protective layer is not ablatable, removal will be by the action of the high-energy radicals generated during the ablation of material lying beneath the protective layer e.g. material of the nozzle plate.
• a protective layer and/or adhesive that absorbs UV radiation has the further advantage of slowing the ablation of the nozzle plate following the initial impingement of the high energy beam, thereby avoiding damage at the periphery of the nozzle outlet.
• the element of the inkjet printhead may be an integral part of the printhead or a separate entity which is attached to the printhead. In the latter case, material removal from the element may take place before or after attachment of the element to the printhead.
• the element of an inkjet printhead in question may be of homogeneous construction or may comprise at least two layers. In the former case, the whole element will necessarily be of ablatable material. Although in the latter case only one of the inner layers need be ablatable, if the outer layer is not ablatable it should be sufficiently thin that it will be removed by the high energy beam. Another possibility is for material to be removed from the outer layer only.
• Removal of the protective layer following ablation may be effected mechanically e.g. by peeling, or chemically e.g. by dissolving the layer using a solvent such as acetone, or by a combination of both.
• the present invention is also directed to a protective layer for use in the method of removing material discussed above, the protective layer comprising an ablatable material having an adhesive coating, the adhesive coating being ablatable.
• a protective layer for use in the method of removing material discussed above, the protective layer comprising an ablatable material having an adhesive coating, the adhesive coating being ablatable.
• the ablatable property may be an intrinsic property of the adhesive or may be achieved by the addition of a UV absorbing additive.
• the layer of ablatable material may comprise polyester or polyimide.
• Figure 1 shows the nozzle plate having a non-wetting coating
• Figure 2 shows the nozzle plate having a non-wetting coating and protective layer according to a first embodiment of the present invention
• Figure 3 shows the nozzle plate/ non-wetting coating/ protective layer arrangement of Figure 2 after material removal
• Figure 4 shows the nozzle plate and non-wetting coating of Figure 3 after removal of the protective layer
• Figure 5 shows the nozzle plate and non-wetting coating of Figure 1 having a protective layer according to a second embodiment of the present invention
• Figure 6 shows a variation of a plate for use in the arrangement of Figure 5.
• a nozzle plate (4) having a non-wetting coating (6) which forms part of the external surface of the printhead.
• the nozzle plate and non-wetting coating may be of the types disclosed, for example, in EP-A-367 438 belonging to the present applicant and incorporated in the present application by reference.
• the nozzle plate is attached to a body (2) of an inkjet printhead having ink ejection channels
• the nozzle plate may comprise any ablatable material - for example plastics material such as polyimide, polycarbonate, polyester, polyetheretherketone, acrylics or non-vitreous inorganic material such as metal, in particular aluminium, or ceramics. Where a plastics material is used, this may include additives of the kind normally employed with plastics, including organic and/or inorganic fillers.
• plastics material such as polyimide, polycarbonate, polyester, polyetheretherketone, acrylics or non-vitreous inorganic material such as metal, in particular aluminium, or ceramics.
• plastics material such as polyimide, polycarbonate, polyester, polyetheretherketone, acrylics or non-vitreous inorganic material such as metal, in particular aluminium, or ceramics.
• this may include additives of the kind normally employed with plastics, including organic and/or inorganic fillers.
• the non-wetting coating may be of the kind comprising fluorocarbon functional silane and may be formed by the method described in the above- mentioned EP-A-0 367 438, whereby an adherent first layer comprising cured siloxane is formed on the surface of the nozzle plate, followed by a second layer derived from at least one fluorosilane having a silicon atom to which is attached at least one hydrolysable group and at least one fluorine- containing organic group which donates non-wetting properties to the layer.
• Figure 2 shows the nozzle plate and non-wetting coating of Figure 1 when provided with a protective layer (10) as per a first embodiment of the present invention.
• This layer is preferably polyester film, for example the polyethylene terephthlate (PET) film sold by ICI under the trade name Melinex (trade mark), or polyimide (PI) film, for example that sold by UBE under the name Upiiex (trade mark). Both these materials are ablatable and have a high absorbance of ultra-violet radiation in the region of 248 nm wavelength.
• PET polyethylene terephthlate
• PI polyimide
• the protective layer is attached to the non-wetting coating by a layer (8) of pressure sensitive adhesive.
• the adhesive is preferably applied first to the protective layer (rather than the non-wetting surface) by any suitable means e.g. a wire-wound meter bar, the adhesive-coated protective layer then being applied to the non-wetting coating using pressure.
• the adhesive is preferably ablatable - this property being either intrinsic or obtained by means of an ultra-violet radiation absorbing additive. It is noted that application of the protective layer need not take place immediately prior to the material removal process. In the case of a nozzle plate, for example, a protective layer may be applied to a sheet of nozzle plate material to which a non-wetting coating has been applied. Such a sheet is subsequently cut up to form individual nozzle plates, each of which is attached to a printhead. Only then would the step of material removal - in this case nozzle formation - take place.
• Material removal is effected by directing a high energy beam - such as an excimer laser beam - at that side of the nozzle plate (4) on which the non-wetting coating (6) is located such that material is removed from the nozzle plate by ablation.
• a high energy beam - such as an excimer laser beam -
• the wavelengths of laser light chosen are typically 193, 248 or 308 nm, corresponding to photon emission at the excimer line of argon fluoride (ArF), krypton fluoride (KrF) or xenon fluoride (XeCI) respectively.
• the material of the protective layer (10) is also ablated away ( Figure 3).
• the non-wetting coating is sufficiently thin - no greater than 1 micron for example - that it may be removed without necessarily being made of an ablatable material.
• Material may be removed from the nozzle plate to create not only nozzles of the types mentioned in the aforementioned documents but also solvent wettable areas of the type disclosed in EP-A-0 389 217 or nozzles having a formation provided within the bore serving to control the nozzle ink meniscus as per W093/15911 - both of these documents belonging to the present applicant and being incorporated herein by reference. Material removal may take place with the nozzle plate remote from the rest of the printhead or attached to the printhead. The latter method avoids problems with both registration of the nozzles in the nozzle plate with the channels of the inkjet printhead and alignment of the nozzle axes in the plane of the channels.
• the protective layer is removed from the surface of the non-wetting coating (6) to leave the arrangement shown in Figure 4. Any ablation products that might otherwise have diffused back towards the printhead and have been deposited upon the protection layer, are also removed in this step. There is left a nozzle plate having well- formed nozzle bores (14) and outlets (16) having sharp edges (18) and surrounded by an undamaged non-wetting coating (6).
• the protective layer may be of such a constitution - for example a liquid or a gel - that it establishes by itself a sealing engagement with the surface to be protected.
• the liquid/gel layer according to the second embodiment may simply be applied to the surface to be protected by any conventional means e.g. roll coating.
• Figure 5 shows an arrangement of this second embodiment where the liquid/gel layer (20) is held between the surface (6) of the printhead and a plate (26) having an aperture (28) through which can pass the hight energy beam. That part of the liquid/gel lying in the path (22) of the beam is removed whilst the liquid/gel lying outside the path of the beam remains and protects the surface of the nozzle plate and in particular that surface lying at the periphery of the nozzle outlet (24).
• the viscosity of the liquid/gel layer is selected so that the layer remains in place around the periphery of the nozzle aperture, during the ablation process.
• the non-wetting action of a coated nozzle plate will be taken into consideration, in selecting this viscosity, together with the period of time required for the ablation process.
• the liquid/gel is preferably ablatable, thereby avoiding the problems with non-ablatable layers discussed earlier.
• the liquid/gel is of sufficiently high viscosity that it remains in location once applied - either to the surface of the printhead or between the surface of the printhead and the plate.
• a suitable liquid is a high molecular weight liquid such as polypropylene glycol.
• the plate may hold the liquid/gel in position or may itself be held in position by the liquid/gel layer. In both of cases, the plate offers an additional degree of protection to the surface of the printhead from ablation products.
• the plate may be of such construction as to be reusable many times or to be discarded after ablation of the nozzle along with the liquid/gel. It may advantageously comprise polyester film, for example the polyethylene terephthlate (PET) film sold by ICI under the trade name Melinex (trade mark).
• PET polyethylene terephthlate
• the aperture in the plate can be formed prior to ablation of the nozzle using the same high energy beam as used for nozzle formation, an aperture larger than the outlet aperture of the nozzle being obtained by displacing the plate along the axis of the tapered beam such that a larger section of this tapered beam ablates a larger aperture.
• the plate can either be in-situ on the surface of the printhead or remote from the printhead during this process.
• the liquid/gel may be inserted between the plate and the printhead surface in any suitable fashion, for example roll coating of the plate or the printhead surface prior to assembly, or by pumping the liquid between the plate and the printhead surface.
• An design of plate (26) particularly suited to this latter process is shown in Figure 6: in addition to an aperture (28), the plate has a chamber (30) formed beneath the aperture in which the liquid layer can form in the particularly critical area around the nozzle. Liquid may be fed to the chamber (as indicated by arrows 34) via channels (32) formed in the plate.
• the present invention is also applicable to the case where the element to be ablated is an integral part of the printhead e.g. where nozzles are created directly in the printhead as per EP-A-0 595 654.
• both the method of removing material and the protective layer arrangement described in the present document are not restricted to the manufacture of nozzles or nozzle plates but are applicable to any element of an inkjet printhead which includes an ablatable material and which has a surface intended to form part of the external surface of the printhead.

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• Engineering & Computer Science (AREA)
• Manufacturing & Machinery (AREA)
• Physics & Mathematics (AREA)
• Optics & Photonics (AREA)
• Particle Formation And Scattering Control In Inkjet Printers (AREA)

Applications Claiming Priority (3)

Publications (2)

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Family Applications (1)

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• 1994
  • 1994-09-13 GB GB9418412A patent/GB9418412D0/en active Pending
• 1995
  • 1995-09-12 WO PCT/GB1995/002157 patent/WO1996008375A1/en not_active Application Discontinuation
  • 1995-09-12 EP EP95931308A patent/EP0781203B1/de not_active Expired - Lifetime
  • 1995-09-12 KR KR1019970701632A patent/KR970706128A/ko not_active Application Discontinuation
  • 1995-09-12 JP JP8509993A patent/JPH10505557A/ja active Pending
  • 1995-09-12 CA CA002199033A patent/CA2199033A1/en not_active Abandoned
  • 1995-09-12 DE DE69507622T patent/DE69507622T2/de not_active Expired - Fee Related

Non-Patent Citations (1)

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