Residue removal from nozzle guard for ink jet printhead

Field of invention

The present invention relates to digital printers, and more particularly to inkjet printers.

Background of the invention

Inkjet printers are a well-known and widely used form of print medium manufacturing. Colorants, usually ink, are fed to a microprocessor-controlled nozzle array on the printhead. As the printhead passes over the medium, the colorant is ejected from the nozzle array to produce a print on the medium substrate.

Printer performance depends on factors such as operating costs, print quality, operating speed, and ease of use. The mass, frequency, and velocity of individual ink droplets ejected from the nozzle will affect these performance parameters.

Recently, nozzle arrays have been formed using microelectromechanical system (MEMS) technology with a submicron-thick mechanical structure. This allows picolitres (x10)^-12It is possible to manufacture a print head capable of rapidly ejecting ink droplets having a size in the range of liters).

The microscopic construction of these printheads allows for high speed and good print quality at a relatively low cost, but at these sizes the nozzles become extremely fragile, with fingers, dust, etc. Alternatively, even the slightest contact with the medium base material makes it susceptible to damage. This makes these printheads impractical for many applications that require a certain level of toughness. In addition, the damaged nozzle may not be able to eject the colorant supplied to it. When the colorant accumulates outside the nozzle and becomes ball-like, the colorant ejection from the surrounding nozzles can be affected, and / or the damaged nozzle simply becomes a printing substrate. The colorant will leak out. Both situations are unfavorable for print quality.

To eliminate this, perforated guards may be provided across the nozzles to shield them from damaging contacts. The ink ejected from the nozzle passes through the holes toward the paper or other substrate to be printed. However, in order to effectively protect the nozzles, the holes need to be as small as possible, leaving the ink droplets through while maximizing restrictions to prevent the inflow of remnants. Ideally, each nozzle ejects ink through its own individual hole in the guard.

The holes in the guard are generally very small and can easily become clogged. Therefore, it is often desired to keep the outside of the nozzle guard clean, especially in environments with relatively high levels of dust and other airborne particles. It would be convenient if this was achieved with a wiper blade that periodically sweeps the outer surface of the guard to remove dust and ink residues. However, the residue on the wiper often stays on the outer rim, especially on the portion of the rim that faces the direction of travel of the wiper. Accumulation of such residues tends not to be removed by the wiper and quickly clogs the holes.

Outline of the invention

Accordingly, according to the present invention, there is a perforated nozzle guard of an inkjet printhead having a nozzle array that ejects a colorant onto a substrate to be printed, such that the nozzle guard prevents damaging contact with the nozzle. The colorant extending from the outside of the nozzle and ejected from the nozzle is adapted to be placed on the printhead so that it can pass through the holes to the substrate to be printed, and the nozzle guard. Has an outer surface that faces the medium during use, the outer surface is configured to engage a wiper blade that periodically sweeps the surface to remove residues, and the outer surface is such that the wiper blade is in the hole. Nozzle guards are provided that have recesses that are individually associated with each of the holes so that they do not engage with the outer surface directly adjacent to.

As used herein, the term "nozzle" should be understood as a defining element of the aperture, not the aperture itself.

The outer surface further comprises a deflector ridge on each of the recesses, which are preferably arranged to engage the wiper blades before the blades pass through the holes associated with the recesses. In one preferred embodiment, the deflector ridge is arcuate and is arranged relative to the sweep direction so as to deflect the residue from the hole towards the edge of the recess.

The nozzle guard may further include a fluid inlet for directing the fluid through the passages across the nozzle array to prevent the accumulation of foreign particles on the nozzle array.

The nozzle guard may further include a pair of integrally formed spaced support elements, one of which is disposed at each end of the nozzle guard.

In this embodiment, the fluid inlet opening may be disposed on one of the support elements.

It should be understood that when air is directed through the openings, over the nozzle array, and through the passages, the accumulation of foreign particles on the nozzle array is blocked.

The fluid inlet opening may be located on a support element away from the bond pad of the nozzle array.

To optimize the effect of the wiper blade, the outer surface is flat except for recesses and deflector ridges. By forming the guard from silicon, the coefficient of thermal expansion is substantially consistent with the nozzle array. This makes it possible to prevent misalignment between the hole array on the guard and the register having the nozzle array. In addition, the use of silicon makes it possible to accurately machine shields using MEMES technology. In addition, silicon is very strong and virtually non-deformable.

Hereinafter, preferred embodiments of the present invention will be described only for exemplary purposes with reference to the accompanying drawings.

Detailed explanation along the drawing

First, referring to FIG. 1, the nozzle assembly according to the invention is generally shown by reference number 10. The inkjet printhead has a plurality of nozzle assemblies 10 arranged in an array 14 (FIGS. 5 and 6) on a silicon substrate 16. The array 14 will be described in more detail below.

Assembly 10 comprises a silicon substrate 16 on which a dielectric layer 18 is deposited. A CMOS protective layer 20 is deposited on the dielectric layer 18.

Each nozzle assembly 10 comprises a nozzle 22 defining a nozzle opening 24, a connecting member in the form of a lever arm 26, and an actuator 28. The lever arm 26 connects the actuator 28 to the nozzle 22.

As shown in more detail in FIGS. 2 to 4, the nozzle 22 includes a crown portion 30 and a skirt portion 32 hanging from the crown portion 30. The skirt portion 32 forms a part of the peripheral wall of the nozzle chamber 34. The nozzle opening 24 is in circulation with the nozzle chamber 34. Note that the nozzle opening 24 is surrounded by a raised rim 36 that "holds" the meniscus 38 (FIG. 2) of the ink body 40 of the nozzle chamber 34.

Ink inlet holes 42 (most clearly illustrated in FIG. 6) are defined on the floor 46 of the nozzle chamber 34. The holes 42 are in circulation with the ink inlet channels 48 defined to pass through the substrate 16.

The wall portion 50 defines the boundary of the hole 42 and extends upward from the floor portion 46. As described above, the skirt portion 32 of the nozzle 22 defines the first portion of the peripheral wall of the nozzle chamber 34, and the wall portion 50 defines the second portion of the peripheral wall of the nozzle chamber 34.

As described in more detail below, when the nozzle 22 is displaced, the wall 50 has an inward lip 52 at the free end that acts as a fluid seal that prevents ink from escaping. Due to the viscosity of the ink 40 and the small spacing between the lip 52 and the skirt portion 32, the inward lip 52 and surface tension serve as an effective seal to prevent ink from escaping from the nozzle chamber 34.

The actuator 28 is a thermal bending actuator and is connected to an anchor 54 extending upward from the substrate 16 or, in particular, from the CMOS protective layer 20. The anchor 54 is provided on a conduction pad 56 that forms an electrical connection with the actuator 28.

The actuator 28 includes a first active beam 58 disposed above the second passive beam 60. In a preferred embodiment, the beams 58 and 60 are both composed of or include a conductive ceramic material such as titanium nitride (TiN).

Both beams 58 and 60 have a first end fixed to the anchor 54 and an opposing end connected to the arm 26. When a current flows through the active beam 58, thermal expansion of the beam 58 occurs. Since the passive beam 60 has no current flow and does not expand at the same speed, a bending moment is generated, and as shown in FIG. 3, the arm 26 and thus the nozzle 22 are displaced downward toward the substrate 16. As a result, as shown in Reference No. 62, the ink is ejected through the nozzle opening 24. When the heat source is removed from the active beam 58, that is, when the current flow is stopped, the nozzle 22 returns to the resting position shown in FIG. When the nozzle 22 returns to the resting position, the ink droplet 64 is formed by bursting the neck portion of the ink droplet as shown by reference numeral 66 in FIG. After that, the ink droplet 64 advances on a printing medium such as paper. As a result of forming the ink droplet 64, a "concave" meniscus as shown by reference numeral 68 in FIG. 4 is formed. Such a "concave" meniscus 68 causes the ink 40 to flow into the nozzle chamber 34 to form a new meniscus 38 (FIG. 2), ready to eject the next ink droplet from the nozzle assembly 10.

Hereinafter, the nozzle array 14 will be described in more detail with reference to FIGS. 5 and 6. Array 14 is for a 4-color printhead. Therefore, the array 14 comprises four groups 70 of nozzle assemblies, each corresponding to each color. Each group 70 has nozzle assemblies 10 arranged in two rows 72 and 74. Figure 6 shows one of the groups 70 in more detail.

The nozzle assembly 10 in row 74 is offset or staggered with respect to the nozzle assembly 10 in row 72 so that the nozzle assemblies 10 in rows 72 and 74 can be easily integrated. Also, the nozzle assembly 10 in row 72 is spaced apart from each other so that the lever arms 26 of the nozzle assembly 10 in row 74 can pass between adjacent nozzles 22 of the assembly 10 in row 72. Note that each nozzle assembly 10 has a substantially dumbbell-like shape such that the nozzle 22 in row 72 fits between the nozzle 22 in the adjacent nozzle assembly 10 in row 74 and the actuator 28.

Further, each nozzle 22 has a substantially hexagonal shape so that the nozzles 22 in rows 72 and 74 can be easily integrated.

During use, when the nozzle 22 is displaced toward the substrate 16, the nozzle opening 24 is at a slight angle with respect to the nozzle chamber 34, so that the ink is ejected slightly out of the vertical direction. Will be understood by those skilled in the art. It is an advantage of the configuration shown in FIGS. 5 and 6 that the actuator 28 of the nozzle assembly 10 in rows 72 and 74 extends in the same direction as one side of rows 72 and 74. Therefore, the ink ejected from the nozzles 22 in the row 72 and the ink ejected from the nozzles 22 in the row 74 are shifted from each other by the same angle, so that high print quality can be obtained.

Further, as shown in FIG. 5, the substrate 16 has a bond pad 76 disposed on the upper side, which provides an electrical connection to the actuator 28 of the nozzle assembly 10 via the pad 56. These electrical connections are formed via a CMOS layer (not shown).

With reference to FIG. 7, the nozzle array and nozzle guard are shown. With reference to the drawings described above, similar reference numbers refer to similar parts unless otherwise noted.

A nozzle guard 80 is provided on the silicon substrate 16 of the array 14. The nozzle guard 80 includes a shield 82 through which a plurality of holes 84 are defined. When the holes 84 are aligned with the nozzle openings 24 of the nozzle assembly 10 of the array 14 so that the ink is ejected from any one of the nozzle openings 24, the ink passes through the relevant passages and then the print medium. It hits.

In an environment with relatively high levels of dust and other airborne particles, pore 84 can become clogged. Further, the outer surface of the nozzle guard 80 can accumulate ink leaked from the damaged nozzle. As shown in FIG. 7a, it is convenient to provide the wiper blade 143 that periodically sweeps the residual material 144 from the outer surface 142. Unfortunately, the residue 144 on the wiper 143 often remains on the outer rim of the hole 84, especially in the portion of the rim facing the wiper's direction of travel 145. The residue 144 thus accumulated tends not to be removed by the wiper 143, which quickly clogs the hole 84.

As shown in FIG. 7b, according to the present invention, recesses are provided on the outer surface 142 around each of the holes 84. Since the wiper blade 143 passes through the hole 84, the collected residue 144 does not stay on the rim. As a further defense, each recess 146 will be equipped with a deflector ridge 147. As best shown in FIG. 7c, the deflector ridge 147 engages the wiper blade 143 just before passing through the hole 84. The deflector ridge 147 removes some of the residue 144 on the blade 143, further reducing the likelihood of the residue 144 falling into the holes 84. The deflector ridge 147 is an arc with an inclined surface in the direction 145 of the wiper blade 143, directing the accumulated residue 144 from the hole 84 toward the edge of the recess 146.

The guard 80 is silicon such that it has the strength and rigidity necessary to protect the nozzle array 14 from paper, dust, or damaged contact with the user's fingers. By forming the guard from silicon, the coefficient of thermal expansion is substantially consistent with that of the nozzle array. The purpose is to prevent misalignment between the holes 84 of the shield 82 and the nozzle array 14 when the printhead is heated to normal operating temperature. Further, regarding the manufacture of the nozzle assembly 10, silicon is suitable for high-precision ultra-micro machining using the MEMS technology described in more detail below.

Shields 82 are spaced apart from nozzle assembly 10 by branching protrusions or stanchions 86. One of the stanchions 86 has an air inlet opening 88 defined therein.

During use, when the array 14 is in operation, air is filled through the inlet opening 88 and pushed into the hole 84 with the ink traveling through the hole 84.

Since the air is filled through the holes 84 at a different speed than the ink droplet 64, the ink is not drawn into the air. For example, the ink droplet 64 is ejected from the nozzle 22 at a speed of about 3 m / s. Air is filled through the holes 84 at a speed of about 1 m / s.

The purpose of the air is to keep the pores 84 free of foreign particles. As mentioned above, if these foreign particles, such as dust particles, fall into the nozzle assembly 10, there is a risk of adversely affecting their operation. Providing the nozzle guard 80 with an air inlet opening 88 alleviates this problem. Hereinafter, the manufacturing process of the nozzle assembly 10 will be described with reference to FIGS. 8 to 10.

Starting with the silicon substrate or wafer 16, the dielectric layer 18 is deposited on the surface of the substrate or wafer 16. The dielectric layer 18 is in the form of a CVD oxide of about 1.5 microns. A resist is spun onto the layer 18, and the layer 18 is exposed to the mask 100 and then developed.

After development, the layer 18 is plasma-etched downward to the silicon layer 16. The resist is then stripped and layer 18 is cleaned. This step defines the ink inlet hole 42.

In FIG. 8b, about 0.8 micron aluminum 102 is deposited on layer 18. The resist is spun and the aluminum 102 is exposed and developed against the mask 104. The aluminum 102 is plasma etched down to the oxide layer 18, the resist is stripped and the device is cleaned. This step provides wiring to the bond pad and the inkjet actuator 28. This wiring is for the power plane between the NMOS drive transistor and the connection formed in the CMOS layer (not shown).

About 0.5 micron PECVD nitride is deposited as the CMOS protective layer 20. The resist is spun and the layer 20 is exposed to the mask 106 and then developed. After development, the nitride is plasma etched down to the silicon layer 16 in the area of the aluminum layer 102 and the inlet hole 42. The resist is stripped and the device is cleaned.

Layer 108 of sacrificial material is spun into layer 20. Layer 108 is a 6 micron photosensitive polyimide or a high temperature resist of about 4 μm. Layer 108 is soft-baked, exposed to mask 110, and then developed. If layer 108 is composed of polyimide, layer 108 is hard baked at 400 ° C for 1 hour, or if layer 108 is a high temperature resist, it is hard baked at a temperature higher than 300 ° C. It should be noted in the drawings that the pattern-dependent distortion of the polyimide layer 108 caused by shrinkage is taken into account when designing the mask 110.

In the next step, a second sacrificial layer 112 is applied, as shown in FIG. 8e. Layer 112 is either a 2 μm photosensitive polyimide that is spun or a high temperature resist of about 1.3 μm. Layer 112 is soft baked and exposed to mask 114. After exposure to mask 114, layer 112 is developed. If the layer 112 is polyimide, the layer 112 is hard baked at 400 ° C. for about 1 hour. If layer 112 is a resist, it is hard baked at temperatures above 300 ° C for about 1 hour.

After that, a 0.2 micron multilayer metal layer 116 is deposited. Part of this layer 116 forms the passive beam 60 of the actuator 28.

Layer 116 is formed by sputtering 1,000 Å of titanium nitride (TiN) at about 300 ° C and then sputtering 50 Å of tantalum nitride (TaN). Further, after 1,000 Å of TiN is sputtered, 50 Å of TaN and another 1,000 Å of TiN are sputtered. Another material that can be used in place of TiN is TiB₂, MoSi₂Or (Ti, Al) N.

The layer 116 was then exposed to the mask 118, developed, plasma etched down to the layer 112, and then applied to the layer 116, being careful not to remove the cured layer 108 or 112. The resist is wet stripped.

The third sacrificial layer 120 is applied by spinning 4 μm photosensitive polyimide or approximately 2.6 μm high temperature resist. The layer 120 is soft-baked and then exposed to the mask 122. The exposed layer is then developed and then hard baked. Layer 120 is hard-baked at 400 ° C. for about 1 hour in the case of polyimide, or hard-baked at temperatures above 300 ° C. if layer 120 is composed of resist.

A second multilayer metal layer 124 is applied to the layer 120. The composition of layer 124 is the same as layer 116 and is applied in the same way. It should be understood that both layers 116 and 124 are conductive layers.

Layer 124 is developed after being exposed to mask 126. After the layer 124 is plasma etched down to the polyimide or resist layer 120, the resist applied to the layer 124 is wet stripped, being careful not to remove the cured layers 108, 112, or 120. Note that the rest of layer 124 defines the active beam 58 of actuator 28.

A fourth sacrificial layer 128 is applied by spinning 4 μm photosensitive polyimide or approximately 2.6 μm high temperature resist. Layer 128 is soft-baked, exposed to mask 130 and then developed to leave an island portion as shown in FIG. 9k. The rest of layer 128 is hard-baked at 400 ° C for about 1 hour for polyimide or at temperatures above 300 ° C for resist.

As shown in FIG. 8l, a dielectric layer 132 with a high Young's modulus is deposited. Layer 132 is composed of approximately 1 μm silicon nitride or aluminum oxide. Layer 132 is deposited at temperatures below the hard bake temperatures of sacrificial layers 108, 112, 120 and 128. The main features required for this dielectric layer 132 are high modulus of elasticity, chemical inertness, and good adhesion to TiN.

The fifth sacrificial layer 134 is applied by spinning 2 μm photosensitive polyimide or approximately 1.3 μm high temperature resist. Layer 134 is soft-baked, exposed to mask 136, and developed. The rest of layer 134 is then hard-baked at 400 ° C. for 1 hour for polyimide and hard-baked at temperatures above 300 ° C. for resist.

The dielectric layer 132 is plasma etched downward to the sacrificial layer 128, being careful not to remove the sacrificial layer 134.

This step defines the nozzle opening 24, the lever arm 26 and the anchor 54 of the nozzle assembly 10.

A dielectric layer 138 with a high Young's modulus is deposited. This layer 138 is formed by depositing 0.2 μm silicon nitride or aluminum nitride at temperatures below the hard bake temperatures of the sacrificial layers 108, 112, 120, and 128.

Layer 138 is then anisotropically plasma etched to a depth of 0.35 microns, as shown in FIG. 8p. This etching is for removing the dielectric layer from the entire surface of the dielectric layer 132 and the sacrificial layer 134 except for the side walls. This step forms a nozzle rim 36 near the nozzle opening 24 that "holds" the ink meniscus, as described above.

Ultraviolet (UV) release tape 140 is applied. A 4 μm resist is spun on the back surface of the silicon wafer substrate 16. The wafer 16 is exposed to the mask 142 to etch back the wafer 16 and defines the ink inlet channel 48. The resist is then stripped from the wafer 16.

An additional UV release tape (not shown) is applied to the back surface of the wafer 16 to remove the tape 140. Oxygen plasma strips the sacrificial layers 108, 112, 120, 128, and 134 to give the final nozzle assembly 10, as shown in FIGS. 8r and 9r. For ease of reference, the reference numbers shown in these two drawings are the same as those in FIG. 1 to indicate the relevant parts of nozzle assembly 10. 11 and 12 show the operation of the nozzle assembly 10 manufactured according to the process described above with reference to FIGS. 8 and 9, which correspond to FIGS. 2-4.

It will be appreciated by those skilled in the art that various modifications and / or modifications may be made to the invention without departing from the broadly stated gist or scope of the invention as set forth in the particular embodiment. Will be done. Therefore, the present invention should be considered in all respects, exemplary and non-limiting.

<figref num="1">A schematic three-dimensional view of the nozzle assembly of an inkjet printhead is shown.</figref><figref num="2">A schematic three-dimensional diagram of the operation of the nozzle array of FIG. 1 is shown.</figref><figref num="3">A schematic three-dimensional diagram of the operation of the nozzle array of FIG. 1 is shown.</figref><figref num="4">A schematic three-dimensional diagram of the operation of the nozzle array of FIG. 1 is shown.</figref><figref num="5">A three-dimensional view of the nozzle array is shown.</figref><figref num="6">An enlarged view of a part of the array of FIG. 5 is shown.</figref><figref num="7">A three-dimensional view of an inkjet printhead equipped with a nozzle guard is shown.</figref><figref num="7a">A partial cross-sectional side view of the inkjet printhead and nozzle guard of FIG. 7 cleaned by the wiper blade is shown.</figref><figref num="7b">The partial cross-sectional side view of the nozzle guard by this invention is shown.</figref><figref num="7c">The plan view of the outer surface of the nozzle guard of FIG. 7b is shown.</figref><figref num="8">8a-8r show three-dimensional views of the manufacturing steps of the nozzle array of the inkjet printhead.</figref><figref num="9">9a-9r show cross-sectional side views of the manufacturing step.</figref><figref num="10">Figures 10a-10k show the layout of masks used at various steps in the manufacturing process.</figref><figref num="11">11a to 11c show a three-dimensional view of the operation of the nozzle assembly manufactured by the methods of FIGS. 8 and 9.</figref><figref num="12">12a-12c show cross-sectional side views of the operation of the nozzle assembly manufactured by the methods of FIGS. 8 and 9.</figref>