Fluid ejection head

Description of equivalent WO 2004067280 A2

FLUID EJECTION HEAD

BACKGROUND Fluid ejection devices may find uses in a variety of different technologies. For example, some printing devices, such as printers, copiers and fax machines, print by ejecting tiny droplets of a printing fluid from an array of fluid ejection orifices onto the printing medium. The fluid ejection mechanisms are typically formed on a fluid ejection head that is movably coupled to the body of the printing device. Careful control of such factors as the individual fluid ejection mechanisms, the movement of the fluid ejection head across the printing medium, and the movement of the medium through the device allows a desired image to be formed on the medium.

Some fluid ejection devices may be configured to eject a plurality of different fluids, such as different ink colors and/or compositions, from a single fluid ejection head. In such a fluid ejection head, each individual fluid is typically ejected from a group of closely spaced fluid ejection orifices, and the different groups of orifices for the different fluids are spaced a greater distance apart. The use of such a fluid ejection head may offer several advantages over the use of separate fluid ejection heads for each different fluid. For example, a single fluid ejection head is typically less expensive than multiple fluid ejection heads, and also may use less space than multiple fluid ejection heads for a fluid ejection device of a comparable size.

While the use of a single fluid ejection head to eject a plurality of different fluids may offer advantages over the use of multiple fluid ejection heads, such a fluid ejection head may also present various problems. For example, when printing with (or otherwise using) any fluid ejection device, small droplets of fluids may end up on the surface of the fluid ejection head surrounding the orifice from which it was ejected, instead of onto the intended medium. Where the fluid ejection head is configured to eject multiple fluids, these stray droplets may contaminate an adjacent fluid ejection orifice for a different fluid, and thus cause undesirable mixing of fluids. Also, many fluid ejection devices include a wiper structure to clean the fluid ejection head of stray fluid droplets. Typically, the wiper structure wipes across the fluid ejection head surface, pushing a wave of fluid or fluids in front of it. Depending upon the separation of the different fluid ejection orifices, the size of the fluid ejection head, and the configuration and direction of movement of the wiper structure, the wiper structure may mix the different fluids, and thus may cause the contamination of fluid ejection orifices of one type of fluid with other fluids.

The mixing of fluids may cause problems with color reproduction, and may cause other problems as well. For example, some fluids commonly used with fluid ejection devices are configured to react with other fluids ejected from the same device. Inks with this property are referred to generally as "reactive inks." If one of the reacting fluids is not an ink, it may be referred to as a "fixer fluid." Where two reactive fluids are ejected from the same fluid ejection device, the fluids may be configured to immediately harden at the boundary where the drop of one fluid meets a drop of the other fluid to prevent color mixing and/or bleeding on a fluid-receiving medium. Thus, where one reactive fluid contaminates the ejection orifices of a different reactive fluid, the fluids may harden and clog the ejection orifice. The hardened fluids may then be difficult to remove by "spitting", or firing fluids through the orifice at a cleaning station. These problems may be somewhat reduced by increasing the size of the fluid ejection head, and spreading the fluid ejection orifices for each fluid farther away from orifices of other fluids. However, this may increase the cost and size of the fluid ejection device, and thus may negate some of the advantages of the use of a single fluid ejection head to eject multiple fluids. SUMMARY

Some embodiments of the present invention provide a fluid ejection head, wherein the fluid ejection head includes an orifice layer disposed on top of a substrate layer. The fluid ejection head also includes a first group of fluid ejection orifices and a second group of fluid ejection orifices formed in the fluid ejection head, wherein the first group of fluid ejection orifices and the second group of fluid ejection orifices are configured to eject two different fluids, and an elongate channel formed in the fluid ejection head, wherein the channel is positioned between the first group of fluid ejection orifices and the second group of fluid ejection orifices in such a location as to inhibit cross-contamination of fluids ejected from the first group of fluid ejection orifices and second group of fluid ejection orifices.

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is an isometric view of a fluid ejection device according to one embodiment of the present invention.

Fig. 2 is a magnified, broken-away plan view of a first alternative fluid ejection head of the embodiment of Fig. 1.

Fig. 3 is a sectional view of the fluid ejection head of Fig. 2, taken along line 3-3 of Fig. 2.

Fig. 4 is a magnified, broken-away plan view of a second alternative fluid ejection head of the embodiment of Fig. 1.

Fig. 5 is a magnified, broken-away plan view of a third alternative fluid ejection head of the embodiment of Fig. 1. Fig. 6 is a magnified, broken-away plan view of a fourth alternative fluid ejection head of the embodiment of Fig. 1.

Fig. 7 is a magnified, broken-away plan view of a fifth alternative fluid ejection head of the embodiment of Fig. 1 , and an exemplary wiper structure suitable for use with the fluid ejection head. Fig. 8 is a sectional view of the fluid ejection head of Fig. 7, taken along line 8-8 of Fig. 7. Fig. 9 is a sectional view of an alternate embodiment of the fluid ejection head of Fig. 7.

Fig. 10 is a magnified, broken-away plan view of a sixth alternative fluid ejection head of the embodiment of Fig. 1. Fig. 11 is a sectional view of the fluid ejection head of Fig. 10, taken along line 11-11 of Fig. 10.

DETAILED DESCRIPTION Fig. 1 shows, generally at 10, one exemplary embodiment of a fluid ejection device according to the present invention. Fluid ejection device 10 takes the form of a desktop printer, and includes a body 12, and a fluid ejection cartridge 14 operatively coupled to the body. Fluid ejection cartridge 14 is configured to deposit a fluid onto a medium 16 positioned adjacent to the cartridge via a fluid ejection head 18. Control circuitry in fluid ejection device 10 controls the movement of fluid ejection cartridge 14 across medium 16, the movement of the medium under the fluid ejection cartridge, and the firing of fluid from the individual fluid ejection orifices on the fluid ejection cartridge.

Although shown herein in the context of a printing device, a fluid ejection device according to the present invention may be used in any number of different applications. Furthermore, while the depicted printing device takes the form of a desktop printer, a fluid ejection device according to the present invention may take the form of any other suitable type of printing device, such as a copier or a facsimile machine, and may have any other desired size, large- or small-format.

Fig. 2 shows a magnified plan view of a portion of the surface of fluid ejection head 18. Fluid ejection head 18 includes a first fluid feed slot 20a for delivering a first fluid to the fluid ejection head, and a second fluid feed slot 20b for delivering a second fluid to the fluid ejection head. Only two fluid feed slots are shown for clarity. However, it will be appreciated that a fluid ejection head according to the present invention may have any desired number of fluid feed slots, and generally at least one for each type of fluid ejected. For example, a six-color fluid ejection head may have six or more fluid feed slots. Fluid ejection head 18 also includes at least one fluid ejection orifice for each fluid feed slot 20a, b. In the depicted embodiment, fluid ejection head 18 includes two separate columns of orifices, indicated at 21 and 21', for each fluid feed slot. The orifices corresponding to fluid feed slot 20a are shown at 22a, and the orifices corresponding to fluid feed slot 20b are shown at 22b. The use of columns of orifices 22a and 22b to eject fluids helps to decrease the width of the fluid ejection head or carriage as fluid ejection head 18 is passed across medium 16, and thus helps to decrease the time to print a desired image. While each fluid feed slot 20a and 20b of the depicted embodiment has two associated columns of fluid ejection orifices, it will be appreciated that each fluid feed slot may also have only a single column of associated fluid ejection orifices, or more than two columns of orifices.

With recent advances in fluid ejection technology, it has become possible to place fluid feed slots 20a and 20b very close together, for example, on the order of 1.2-1.4 millimeters apart. This is advantageous, as it helps to decrease the size of fluid ejection head 18, and thus the manufacturing cost of the fluid ejection head. However, this also places the orifices 22a that are most closely adjacent to the orifices 22b a distance of approximately one millimeter from orifices 22b. To help prevent cross-contamination of fluids ejected from fluid ejection orifices 22a and fluids ejected from fluid ejection orifices 22b, fluid ejection head 18 also includes a cross-contamination barrier disposed between fluid ejection orifices 22a and 22b. Fig. 2 shows, generally at 30, a first exemplary embodiment of a suitable cross-contamination barrier, and Fig. 3 shows a cross- sectional view of the barrier. Barrier 30 includes a pair of trenches or channels 32a, 32b configured to form a sufficient break in the surface of fluid ejection head 18 to prevent puddles of fluid from fluid ejection orifices 22a from spreading far enough to contaminate fluid ejection orifices 22b, and vice versa. In some embodiments, channels 32a and 32b are also configured to prevent the wave of fluid pushed in front of a wiper in a wiping station from spreading to adjacent fluid ejection orifices. This helps to prevent different fluids from being mixed by the wiper, and thus helps to prevent cross-contamination of orifices 22a and 22b by the wiper. While the embodiment of Figs. 2-3 has two generally parallel channels 32a and 32b, other embodiments of the cross-contamination barrier may have three, four, or more parallel channels.

Channels 32a and 32b may have any suitable structure. Referring to Fig. 3, the depicted fluid ejection head 18 includes a substrate layer 34, an intermediate protective layer 36, and an orifice layer 38. The surface of the substrate layer 34 typically includes circuit structures (not shown) configured to cause the ejection of fluid from a fluid ejection orifice when triggered by off- substrate circuitry, while orifice layer includes the structures that form the fluid ejection orifices and corresponding firing chambers. Fluid feed slots 20a and 20b are formed in substrate layer, while fluid ejection orifices 22a and 22b extend through protective layer 36 and orifice layer 38. Channels 32a and 32b of the depicted embodiment are formed in orifice layer 38, and extend completely through the orifice layer to protective layer 36. While channels 32a and 32b of the depicted embodiment extend through the entire thickness of orifice layer 38, it will be appreciated that the channels may also extend only partially through the orifice layer.

In some embodiments, protective layer 36 is configured to protect the surface of substrate layer 34 and the circuit structures thereon from any reactive and/or corrosive fluids that may enter channels 32a and 32b. Protective layer 36 may be made from any suitable material, including, but not limited to, epoxy- based photoresists such as an SU-8 resist, available from MicroChem, Inc. or Sotec Microsystems. Similarly, protective layer 36 may have any suitable thickness. Where protective layer 36 is formed from SU-8, a relatively thin layer, on the order of approximately two to four microns, may be used to form protective layer 36. This may be advantageous, as a relatively thin layer of protective material may be less expensive to fabricate than a thicker protective layer. It will be appreciated that protective layer 36 may be omitted entirely if desired. In embodiments where protective layer 36 is omitted, the circuit structures on the surface of substrate layer 34 may include other protective means as known to those of skill in the art. Channels 32a and 32b may be formed at any suitable location between fluid ejection orifices 22a and 22b. In the depicted embodiment, the halfway point between channels 32a and 32b is positioned approximately halfway between fluid feed slot 20a and fluid feed slot 20b, although the two channels may be centered at another location if desired. In some embodiments, channels 32a and 32b are centered substantially intermediate fluid ejection orifices 22a and 22b, as placing the center channels closer to the midway point between orifices 22a and 22b allows a larger puddle to form on either side of the channels before the puddle encounters the channels. This may make the puddle less likely to fill, and thus bridge, the channel.

Channels 32a and 32b may be separated by any suitable distance. For example, where fluid feed slots 20a and 20b are separated by a distance of approximately 1.4 millimeters, channels 32a and 32b may be separated by a distance in the range of 25-100 microns, and more typically by a distance of approximately 50 microns. Likewise, channels 32a and 32b may have any suitable widths. Suitable widths include, but are not limited to, those in the range of approximately 20-80 microns. More typically, channels 32a and 32b have widths of approximately 50 microns.

Channels 32a and 32b may also have any suitable length. Typically, channels 32a and 32b are configured to extend at least as far as the length of columns 21 and 21' of fluid ejection orifices so that no straight path exists between any of fluid ejection orifices 22a and any of fluid ejection orifices 22b. In some embodiments, channels 32a and 32b may be configured to extend beyond the ends of columns 21 and 21' of fluid ejection orifices to add additional protection against cross-contamination. In these embodiments, channels 32a and 32b may extend any desired distance beyond the ends of columns 21 and 21' of fluid ejection orifices. Suitable distances include, but are not limited to, approximately 300-500 microns beyond each end of columns 21 and 21' of fluid ejection orifices. In some embodiments, due to the manufacturing processes used to make fluid ejection head 18, columns 21 and 21' of fluid ejection orifices may include some orifices that are not fluidically connected to fluid feed slots 20a or 20b. In these embodiments, channels 32a and 32b may have a length that extends as far as (or beyond) the last fluidically connected fluid ejection orifice.

Likewise channels 32a and 32b may have any suitable depth. For example, as described above, channels 32a and 32b may extend only partway through orifice layer 38, or all the way through orifice layer 38. Typical depths of channels 32a and 32b include, but are not limited to, depths ranging from approximately 10 microns to the entire depth of the orifice layer, which is typically 20-100 microns thick.

Channels 32a and 32b may be formed in any suitable manner. In some embodiments, channels 32a and 32b are formed as fluid ejection orifices 22a and 22b are formed. In these embodiments, the formation of channels 32a and 32b may not significantly increase the cost and/or difficulty of the overall fluid ejection head manufacturing process. The method or methods used to form channels 32a and 32b typically depend upon the material and/or materials from which orifice layer 38 is formed. In some embodiments, a photoresist, such as an SU-8 resist, may be used to form orifice layer 38.

Fig. 4 shows, generally at 130, a second alternative embodiment of a cross-contamination barrier according to the present invention. In this embodiment, barrier 130 includes a single continuous channel 132. Channel 130 may have any suitable dimensions, including, but not limited to, those described above for each of channels 32a and 32b of the embodiment of Figs. 2- 3. The depicted channel 132 runs beyond the length of columns 121 and 121' of fluid ejection orifices, and is situated approximately halfway between fluid feed slots 120a and 120b. Likewise, channel 132 may have any suitable width. Suitable widths include, but are not limited to, widths between approximately fifty to five hundred microns (or approximately 5-50% of the spacing between fluid feed slots 120a and 120b).

Fig. 5 shows, generally at 230, a third alternative embodiment of a cross- contamination barrier according to the present invention. Barrier 230 includes a first channel 232a surrounding fluid feed slot 220a and fluid ejection orifices 222a in a closed loop, and a second channel 232b surrounding fluid feed slot 220b and fluid ejection orifices 222b in a closed loop. The details of barrier 230 are described herein in terms of first channel 232a. However, it will be appreciated that the description is equally applicable to second channel 232b.

In some embodiments, channel 232a is configured to surround fluid ejection orifices 222a substantially completely to help to prevent fluid puddles from spreading in any direction from the fluid ejection orifices. Channel 232a may have any suitable dimensions, and may be formed in any suitable location on fluid ejection head 18. Typically, channel 232a is positioned 200-500 microns from the nearest fluid ejection orifices 222a along the long side or dimension 234 of the channel, and 100-500 microns from the nearest fluidically-connected fluid ejection orifice along the short side or dimension 236 of the channel, although channel 232a may also be separated from fluid ejection orifices 222a by distances outside of these ranges. Channel 232a may also have any suitable width. Channel 232 may have a width between approximately 20 and 200 microns, or between approximately 50-100 microns. While the depicted channels 232a and 232b completely surround the respective fluid ejection orifices, the channels may also only partially surround the fluid ejection orifices if desired.

Fig. 6 shows, generally at 330, another embodiment of a suitable cross- contamination barrier according to the present invention formed between fluid feed slots 320a and 320b. Instead of having a channel that extends in a continuous manner the entire length of the columns of fluid ejection orifices, barrier 330 includes a plurality of shorter channels 332 arranged in a grate-like arrangement. In the depicted embodiment, the individual shorter channels are arranged into two columns of channels, indicated at 334a and 334b. The individual channels of channel column 334a are offset along the direction of the length of the channel columns with respect to the individual channels of channel column 334b. The offset configuration helps to ensure that no direct path exists between fluid ejection orifices 322a and 322b of slots 320a and 320b, respectively.

The individual channels 332 of channel columns 334a and 334b may have any suitable dimensions. Suitable lengths for channels 332 include, but are not limited to, lengths of 700-1100 microns. Furthermore, each of channel columns 334a and 334b may have any suitable number of individual channels. For example, where the fluid ejection head has a height (along the long dimension of the fluid feed slots and fluid ejection orifice channels) of 8500 microns, and the individual channels 332 each have a length of 900 microns, one channel column may have seven individual channels, and the other channel column may have six individual channels.

Figs. 7 and 8 show, generally at 430, another embodiment of a cross- contamination barrier according to the present invention. In this embodiment, barrier 430 elevates the fluid ejection orifices above a surrounding waste- receiving portion 432 of the fluid ejection head on plateau-like structures, indicated at 436a and 436b. For example, where fluid ejection orifices 422a and 422b are positioned approximately 1.2 millimeters apart, waste-receiving portion 432 may be as wide as approximately one millimeter, or even wider.

The fluid ejection heads of Figs. 5 and 7 are formed in a substantially similar manner. In some embodiments, the barriers 230, 430 are formed by masking the resist layer and exposing the resist layer to form the desired shapes. In these embodiments, the difference in formation is the use of different resist masks. One type of resist mask may be used to form the closed loop configuration of Fig. 5 and its orifices, while a second type of resist mask may be used to form the waste receiving portion of Fig. 7 and its orifices. The masked used in Fig. 7 allows the removal of more resist than the mask of Fig. 5. Furthermore, as shown in Fig. 8, waste-receiving portion 432 may extend the full thickness of orifice layer 438 (to the intermediate protective layer 435), or may extend only partially through the thickness of the orifice layer.

The various embodiments of the channel and barrier structures described above may be used in conjunction with complementary wiper structures to further help reduce the risk of cross-contamination of fluids on the fluid ejection head. One example of a suitable wiper structure is shown generally at 440 in Fig. 7. Wiper structure includes orifice wipers 442a and 442b configured to wipe over fluid ejection orifices 422a and 422b, respectively, and waste-receiving portion wipers 444 configured to clean waste-receiving portion 432.

Orifice wipers 442a and 442b are configured to push fluids off of plateaus 436a and 436b and into adjacent waste-receiving portion 432. Orifice wipers 442a and 442b may have any suitable structure. For example, each orifice wiper 442a and 442b may have a wiping structure with a diagonal orientation relative to the direction of wiper movement across plateaus 436a and 436b. This structure may push fluids into the waste-receiving portion 432 adjacent the lagging edge of the wiper. Alternatively, as in the depicted embodiment, orifice wipers 442a and 442b may have a chevron-shaped wiping structure. Thus, orifice wipers 442a and 442b push fluids toward channels 432 on either side of plateaus 436a and 436b.

Waste-receiving portion wiper 444 is positioned between (and on either

I side of) plateaus 436a and 436b, and is configured to extend into waste-receiving portion 432 to wipe fluids from the waste-receiving portion. Waste-receiving portion wiper 444 may have any suitable configuration. For example, waste- receiving portion wiper 444 may have a concave structure to move fluids away from the sides of plateaus 436a and 436b as the orifice wiper is moved across the fluid ejection head. Alternatively, as shown in the depicted embodiment, waste-receiving portion wiper _.444 may have a generally straight shape, and may be oriented generally perpendicular to the direction in which wiper 440 is moved across the surface of the fluid ejection head.

In some embodiments, orifice wipers 442a and 442b may be configured to wipe across the surface independently of waste-receiving portion wiper 444. In these embodiments, orifice wipers 442a and 442b may be configured to wipe across plateaus 436a and 436b at a different period and/or frequency as waste- receiving portion wiper 444 across waste-receiving portion 432. For example, orifice wipers 442a and 442b may be configured to wipe across plateaus 436a and 436b after two minutes of fluid ejection head use, while waste-receiving portion wiper 444 may be configured to clean waste-receiving portion 432 less frequently, for example, every twenty minutes. Likewise, in some embodiments, orifice wipers 442a and 442b may be pressed against a fluid ejection head at different pressures during a wiping process (or processes), and may be made from different materials.

As mentioned above, the intermediate protective layer 435 between orifice layer 438 and substrate layer 434 may be omitted if desired. Fig. 9 shows a sectional view of an alternative embodiment of the fluid ejection head of Fig. 7, with the protective layer 435 omitted. In this embodiment, waste-receiving portion 432 extends to substrate layer 434. Where the fluids ejected by the fluid ejection device may be corrosive to and/or reactive with the surface of substrate layer 434, the surface of the substrate layer may be converted to, coated with, or otherwise treated with a substance that is less reactive chemically with the fluids.

Figs. 10 and 11 show a fluid ejection head having another embodiment of a cross-contamination barrier 530 according to the present invention. Like the embodiment of Figs. 7-8, barrier 530 elevates fluid ejection orifices 522a and 522b above a surrounding waste-receiving portion 532 of the fluid ejection head on plateau-like structures, indicated at 536a and 536b. However, barrier 530 also includes a wall 540 running the length of waste-receiving portion 532, dividing waste-receiving portion 532 into a first waste-receiving portion 532a and a second waste-receiving portion 532b. The embodiment of Figs. 10 and 11 is similar to the embodiment of Fig. 5, but with wider channels. Wall 540 may help to serve as a further barrier against cross-contamination, and also may allow fabrication of barrier 530 with less etching of orifice layer 538. It will be appreciated that a suitable wiper structure (not shown) with a waste-receiving portion wiper for each of first and second waste-receiving portions 538a and 538b may be employed to clean the barrier structure of the embodiment of Figs. 10 and 11.

The channel structures disclosed herein may offer additional benefits besides helping to prevent cross-contamination of fluids. For example, in conventional fluid ejection heads with no contamination barrier channels, the wiping force from the fluid ejection head wiping structures is distributed across the entire fluid ejection head. However, in the disclosed embodiments, due to the presence of the contamination barrier channels, the wiping force may be more concentrated on the fluid ejection orifices, which may lead to a more efficient and complete wipe. Additionally the channels may provide some amount of stress relief in the orifice layer of the fluid ejection head, and thus may help to prevent damage caused by thermal expansion differences between the substrate layer, the intermediate protective layer, and the orifice layer. Although the present disclosure includes specific embodiments, specific embodiments are not to be considered in a limiting sense, because numerous variations are possible. The subject matter of the present disclosure includes all novel and nonobvious combinations and subcombinations of the various elements, features, functions, and/or properties disclosed herein. The following claims particularly point out certain combinations and subcombinations regarded as novel and nonobvious. These claims may refer to "an" element or "a first" element or the equivalent thereof. Such claims should be understood to include incorporation of one or more such elements, neither requiring nor excluding two or more such elements. Other combinations and subcombinations of features, functions, elements, and/or properties may be claimed through amendment of the present claims or through presentation of new claims in this or a related application. Such claims, whether broader, narrower, equal, or different in scope to the original claims, also are regarded as included within the subject matter of the present disclosure.