System and method for preserving inkjet operational status during long periods of printer inactivity

Abstract

To enable stabilizing ink properties during long periods of printer inactivity without changing ink compositions.SOLUTION: A printhead maintenance station includes: a printhead cap having an opening; a printhead vent blocking member configured to block manifold vents in the printhead when the printhead engages the printhead vent blocking member; and a valve. The valve is positioned within the printhead cap to enable the printhead cap to hold a volume of high pH fluid entering the printhead cap through the opening in the printhead cap when the valve is closed and to enable egress of the high pH fluid when the valve is open. The printhead is lowered onto the printhead cap and a vacuum is applied to an ink supply line to the printhead to inject the high pH liquid into the printhead.SELECTED DRAWING: None

Description

[Technical field]

[0001] FIELD OF THE DISCLOSURE This disclosure relates generally to devices for producing ink images on media, and more particularly to maintaining inkjet operability during extended periods of printer inactivity. [Background technology]

[0002] Inkjet imaging devices, also known as inkjet printers, eject liquid ink from a printhead to form an image on an image receiving surface. The printhead includes a plurality of inkjets arranged in an array. Each inkjet has a thermal or piezoelectric actuator coupled to a printhead controller. The printhead controller generates firing signals corresponding to digital data content that defines the image. The actuators in the printhead respond to the firing signals by expanding into ink chambers fluidly connected to the nozzles to eject ink droplets from the nozzles and onto the image receiving surface to form an ink image that corresponds to the digital image content used to generate the firing signals. The image receiving surface is typically a continuous web of media material or a series of media sheets.

[0003] Inkjet printers used to generate color images typically include multiple printhead modules. Each printhead module typically includes one or more printheads that eject a single color of ink. In a typical inkjet color printer, four printhead modules are positioned in the process direction, with each printhead module ejecting a different color of ink. The four most frequently used ink colors are cyan, magenta, yellow, and black. The common name for such printers is a CMYK color printer. Some CMYK color printers have two printhead modules that print each color of ink. The printhead modules that print the same color of ink are offset from each other in the cross-process direction by half the distance between adjacent inkjets, doubling the number of pixels per inch and increasing the density of the lines of ink color ejected by the printheads in the two modules. As used in this document, the term "process direction" refers to the direction of movement of the image receiving surface as it passes the printheads in the printer, and the term "cross-process direction" refers to the direction perpendicular to the process direction in the plane of the image receiving surface.

[0004] Inkjets, particularly those in printheads that jet aqueous inks, need to be fired periodically to help prevent the ink in the nozzles from drying out. As the inkjets eject a significant amount of ink to create high area coverage in the ink image, the nozzles in the printhead can dry out. Operation of a high percentage of inkjets in a portion of a faceplate on the printhead to print high area coverage can generate a large number of satellite drops that tend to adhere to the faceplate. Satellite drops are small ink drops that separate from larger drops that travel from the nozzles to the image receiving substrate. The accumulation of these satellite drops on the faceplate can clog the nozzles in the faceplate. Additionally, if the inkjets in the printhead are not operated frequently enough, for example when low ink area coverage image portions are printed, the ink in the inkjets can dry out, rendering the inkjets inoperable. To maintain the inkjets in operation, the printhead modules are moved from a position opposite the path of the image receiving substrate to a printhead maintenance station where the printheads are purged. Purging a printhead means that pressurized gas or liquid is applied to ink supply chambers in the printhead to force ink from the chambers into the nozzles where it is ejected from the nozzles onto the faceplate. One or more wipers are then moved across the faceplate to remove the purged ink from the faceplate to a waste ink container.

[0005] During extended periods of printer inactivity, such as an overnight or weekend shutdown, some ink degrades in the nozzles and fouls the printhead by creating buildup on the lock screen, manifold, piezo tiles, and nozzles in the printhead. This fouling results in streaks in the ink images produced when the printer is back in service, reduced ink drop mass, vent line failures, intermittent firing, missing or misdirected ink drops from the inkjets, and ultimately inkjets that cannot be recovered even after purging.

[0006] The smearing appears to occur due to chemical and physical stresses within the inkjet stack of the printhead that increase the pigment particle size and the viscosity of the ink. This smearing can lead to irreversible printhead damage. Reformulating the ink can remedy the smearing problem, but the process is a costly and time-consuming endeavor. Additionally, changes in the ink composition can adversely affect image quality. Thus, inkjet printers would benefit from being able to stabilize ink properties during long periods of printer inactivity without changing the ink composition. Summary of the Invention

[0007] A printhead maintenance station for a color inkjet printer is configured to stabilize ink properties during extended periods of printer inactivity without altering the ink composition. The printhead maintenance station includes a printhead cap configured to cover a face of the printhead, an opening in the printhead cap, a printhead vent blocking member configured to block a manifold vent in the printhead when the printhead is moved into engagement with the printhead vent blocking member, and a valve configured to open and close, the valve positioned in the printhead cap such that when the valve is closed, the printhead cap allows a volume of high pH fluid to enter the printhead cap through the opening in the printhead cap and when the valve is open, allows the high pH fluid to exit the printhead cap.

[0008] A method of operating a printhead maintenance station stabilizes ink properties during extended periods of printer inactivity without altering the ink composition, the method includes filling a printhead cap having a manifold vent blocking member with a high pH liquid, lowering a printhead onto the printhead cap to block manifold vents in the printhead and contact the nozzle plate of the printhead with the high pH fluid, and applying a vacuum to the ink supply lines of the printhead to draw the high pH fluid into the printhead.

[0009] The inkjet printer includes a printhead maintenance station configured to stabilize ink properties during extended periods of printer inactivity without altering the ink composition. The inkjet printer includes at least one printhead module configured with at least one printhead, a printhead cap having a manifold vent blocking member, an opening in the printhead cap, a printhead vent blocking member configured to block a manifold vent in the printhead when the at least one printhead is moved into engagement with the printhead vent blocking member, and a valve configured to open and close, the valve positioned in the printhead cap to allow the printhead cap to retain an amount of high pH fluid entering the printhead cap through the opening in the printhead cap when the valve is closed and to allow the high pH fluid to exit the printhead cap when the valve is open, and a controller operably connected to the at least one printhead module and the printhead maintenance station. The controller is configured to fill a printhead cap with the high pH liquid, lower at least one printhead onto the printhead cap to block manifold vents in the printhead and contact a nozzle plate of the printhead with the high pH fluid, and apply a vacuum to ink supply lines of the printhead to draw the high pH fluid into the printhead.

[0010] A high pH fluid has been developed that is useful for maintaining a print head during periods of inactivity of at least two hours. The high pH fluid includes a fluid and a base added to the fluid that raises the pH level of the fluid to at least 8. [Brief description of the drawings]

[0011] The foregoing aspects and other features of a print head maintenance station and a print head maintenance station method of operating such that a printer stabilizes ink properties during extended periods of printer inactivity without altering the ink composition are described in the following description in conjunction with the accompanying drawings. [Figure 1] FIG. 1 shows a schematic diagram of a color inkjet printer that stabilizes ink properties during extended periods of printer inactivity without changing the ink composition. [Diagram 2] 2 illustrates the print zone of the printer shown in FIG. 1 and a printhead maintenance station positioned adjacent the print zone. [Diagram 3] FIG. 2 shows a diagram of the ink flow paths in a printhead into which a high pH liquid is injected to maintain operational inkjets in the printhead during extended periods of printer inactivity. [Figure 4A] FIG. 4 shows a side view of a printhead operating in a printhead maintenance station configured to inject a high pH liquid into the ink flow path shown in FIG. [Figure 4B] FIG. 4B shows a bottom view of the print head shown in FIG. 4A. [Diagram 5] FIG. 4B shows a flow diagram for operating the print head maintenance station of FIG. 4A. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] For a general understanding of the environment for the printhead maintenance station and method of operation of the printhead maintenance station disclosed herein, and the details of the printhead maintenance station and method of operation of the printhead maintenance station, reference is made to the drawings, in which like reference numbers are used throughout to designate like elements. As used herein, the word "printer" encompasses any device that ejects ink droplets onto different types of media to form ink images.

[0013] FIG. 1 illustrates a high-speed color inkjet printer 10 that stabilizes ink properties during extended periods of printer inactivity without changing the ink composition. As used herein, the term "extended periods of printer inactivity" means that no printing is performed by the printer for at least X hours. As illustrated, the printer 10 is a printer that forms ink images directly on the surface of a media sheet taken from one of media sheet supplies S1 or S2, the sheet S being moved through the printer 10 by a controller 80 that operates one or more actuators 40 that are operatively connected to rollers or at least one drive roller of a conveyor 52 that comprises a portion of a media transport 42 that passes through a print zone PZ (shown in FIG. 2) of the printer. In one embodiment, each printhead module has only one printhead having a width corresponding to the width of the widest media in the cross-process direction that can be printed by the printer. In another embodiment, the printhead module has multiple printheads, each printhead having a width less than the width of the widest media in the cross-process direction that the printer can print. In these modules, the printheads are arranged in a staggered printhead array that allows a wider media to be printed than a single printhead in the module. Additionally, printheads within a module or between printheads in different modules can also be combined such that the density of drops ejected in the cross-process direction by a printhead can be greater in the cross-process direction than the minimum spacing between inkjets in a printhead. Although printer 10 is depicted with only two media sheet supplies, the printer can be configured with three or more sheet supplies, each containing a different type or size of media.

[0014] The print zone PZ in the printer 10 of FIG. 1 is shown in FIG. 2. The print zone PZ has a length in the process direction equal to the distance from the first inkjet that the sheet passes in the process direction to the last inkjet that the sheet passes in the process direction, and a width that is the maximum distance between the outermost inkjet on either side of the print zone that are directly opposite each other in the cross-process direction. Each printhead module 34A, 34B, 34C, and 34D shown in FIG. 2 has three printheads 204 mounted on one of the printhead carrier plates 316A, 316B, 316C, and 316D, respectively. Adjacent to the print zone PZ are four printhead maintenance stations (PHMs) 32. When the printer has been inactive for at least two hours, printing operations are stopped and the printhead modules are moved from the print zone PZ to a position opposite the adjacent printhead maintenance station 32. The printhead maintenance stations operate as described in more detail below to inject a high pH fluid into ink flow paths in the printheads that are susceptible to ink contamination. As used in this document, the term "print zone" refers to the area of ​​the media transport opposite the printhead of an inkjet printer.

[0015] With further reference to FIG. 1, after the ink image is printed on the sheet S, the printed image exits the print zone PZ and passes under the image dryer 30. The image dryer 30 may include an infrared heater, a heated air blower, an air return, or a combination of these components to heat the ink image and at least partially fix the image to the sheet S. The infrared heater applies infrared heat to the printed image on the surface of the sheet S to evaporate water or solvent in the ink. The heated air blower uses a fan, or other pressurized air source, to direct heated air over the ink to supplement the evaporation of water or solvent from the ink. Air is then collected and exhausted by the air return to reduce interference of the dryer airflow with other components in the printer.

[0016] The controller 80 operates at least one of the actuators 40 to rotate the pivot member at position 88 to direct the sheet to either the bin 56 or the return path 72. The rollers rotate the sheet S along the return path 72 in a direction opposite to the process direction movement past the print head. The pivot member 82 is operated by the controller 80 to direct the sheet along a curved portion of the return path 72 into the inverter 76 so that the sheet is flipped over for duplex printing, or along a straight portion of the return path 72. When the sheet follows the straight portion, the inverter 76 is bypassed and the previously printed side of the sheet can be printed again. The controller operates one of the actuators 40 to move the pivot member 82 clockwise to direct the sheet to the inverter 76 or counterclockwise to bypass the inverter. Regardless of whether the substrate has been inverted or not, the substrate merges into the job stream being carried by the media transport section 42 when the controller 80 operates another actuator 40 to rotate the pivot member 86 to provide for the sheet S to enter the job stream entering the print zone PZ from the return path 72.

[0017] As further shown in FIG. 1, the printed media sheets S that are not diverted to the dual path 72 are conveyed by the media transport to the sheet bin 56 where they are collected. Before the printed sheets reach the bin 56, they pass by an optical sensor 84B. The optical sensor 84B generates image data of the printed sheets, which is analyzed by the controller 80 to detect streaks in the printed images on the media sheets of the print job. Additionally, sheets printed with test pattern images are inserted at intervals during the print job. The image data of these test pattern images generated by the optical sensor 84B is analyzed by the controller 80 to determine which inkjets, if any, that were operated to eject ink in the test pattern actually ejected ink, and, if an inkjet ejected ink droplets, whether the ink droplets landed with the proper mass and in their intended locations. Any inkjet that does not eject the ink droplets that it is supposed to eject, or that ejects droplets that do not have the correct mass, or that land in the wrong location, is referred to herein as an inoperable inkjet. The controller can store data identifying the inoperable inkjets in a database 92 operatively connected to the controller 80. These sheets with the test pattern printed on them are sometimes referred to as run-time missing inkjet (RTMJ) sheets, and these sheets are discarded from the output of the print job. The user can operate the user interface 50 to obtain a report displayed on the interface identifying the number of inoperable inkjets and the printhead in which they are located. For sheets that are not inverted and are merged into the job stream by the operation of the pivot member 86, the optical sensor 84A generates image data of the printed side, which the controller 80 uses to align the sheet and operate the ejectors in the printheads to print additional images on the previously printed side of the sheet.Optical sensors 84A and 84B may be digital cameras, arrays of LEDs and photodetectors, or other devices configured to generate image data of a passing surface. Although Fig. 1 shows printed sheets being collected in sheet bin 56, the sheets may be directed to other processing stations (not shown) that perform tasks such as folding, collating, stitching, and stapling the media sheets.

[0018] The operation and control of the various subsystems, components and functions of the machine or printer 10 is performed with the aid of a controller or electronic subsystem (ESS) 80. The ESS or controller 80 is operatively connected to the printhead modules 34A-34D (and thus the printheads), the actuators 40 and the components of the dryer 30. The ESS or controller 80 is a self-contained computer having, for example, a central processor unit (CPU) with electronic data storage, and a display or user interface (UI) 50. The ESS or controller 80 includes, for example, sensor input and control circuits, as well as pixel arrangement and control circuits. Additionally, the CPU reads, captures, prepares and manages the flow of image data between an image input source, such as a scanning system or an on-line or workstation connection (not shown), and the printhead modules 34A-34D. The ESS or controller 80 is thus the main multitasking processor for operating and controlling all other machine subsystems and functions, including the printing process.

[0019] The controller 80 can be implemented with a general-purpose or dedicated programmable processor that executes program instructions. Instructions and data required to perform the programmed functions can be stored in a non-transitory computer-readable medium associated with the processor or the controller. The processors, their memory, and interface circuits configure the controller to perform the operations described below. These components can be provided on a printed circuit card or as circuits in an application specific integrated circuit (ASIC). Each of the circuits can be implemented in a separate processor, or multiple circuits can be implemented on the same processor. Alternatively, the circuits can be implemented with individual components or circuits provided in a very large scale integrated (VLSI) circuit. The circuits described herein can also be implemented with a combination of processors, ASICs, individual components, or VLSI circuits.

[0020] During operation, image content data for the images to be generated is sent to the controller 80 from either the scanning system or an on-line or workstation connection for processing and generation of printhead control signals that are output to the printhead modules 34A-34D. Along with the image content data, the controller receives print job parameters that identify the weight of the media, the dimensions of the media, the print speed, the type of media, the ink area coverage to be generated on each side of each sheet, the location of the image to be generated on each side of each sheet, the media color, the media fiber orientation for fibrous media, the print zone temperature and humidity, the moisture content of the media, and the media manufacturer. As used in this document, the term "print job parameters" refers to non-image content data for a print job and the term "image content data" refers to digital data that specifies the ink images to be printed on the media sheets.

[0021] 3 shows the ink flow paths to the nozzles that are susceptible to ink contamination. These paths include the ink nozzles 304, the piezoelectric actuators 308, the manifolds 312 that lead to the nozzles, and the volumes immediately adjacent on either side of the lock screen 316. To prevent ink contamination in these paths, a high pH fluid is injected into these paths, as described in more detail below.

[0022] A side view of the printhead maintenance station 32 and its interaction with the printhead 204 to inject high pH liquid is shown in FIG. 4A. A printhead cap 404, which covers the printhead nozzle plate during periods of printer inactivity, includes a port 408 for supplying high pH fluid to the cap while a drain valve 412 is closed, so that the level of high pH fluid approaches the top of the cap 404. A vent blocking member 416 is positioned within the printhead cap 404 when the printhead is lowered, covering the nozzle plate with high pH liquid held within the printhead cap 404, the portion of the member blocking the manifold vent 420. The manifold blocking member 416 is made of a flexible material such as polyurethane or rubber. Once the cap covers the nozzle plate and the vent blocking member blocks the manifold vents, a vacuum is applied to the ink supply line 428 to pull the ink meniscus at the nozzle opening in the printhead, causing the high pH fluid to rise up the ink flow path of the printhead to the side of the lock screen 432 opposite the passage to the nozzles. As the high pH fluid is drawn through the lock screen 432, the printhead is raised sufficiently to separate the vent blocking member 416 from the manifold vents, causing the high pH fluid to also be drawn into the manifold vents and into the manifold fluidly connected to the vents. During the transfer of the high pH fluid to the printhead, the port 408 remains open, causing the high pH fluid to flow into the cap and remain in contact with the nozzle plate. The vacuum is then terminated, causing ink to flow into the printhead and the nozzle meniscus to return to the nozzle opening. At the end of a period of printer inactivity, the drain valve 412 is opened, causing the high pH fluid to drain from the cap 204. The PHM 32 is then operated in a known manner to purge ink from the nozzles of the printhead and the nozzle plate is wiped so that the high pH fluid is washed and removed from the printhead and its nozzle plate.

[0023] The high pH fluid can be made from ink used in the printer buffered to a pH of 8 or greater by adding a base such as triethanolamine, triethylamine, diethylamine, dimethylethanolamine, KOH, or NaOH. Alternatively, known printhead cleaning / flushing solutions such as KF200 or CL67 available from Nippon Kayaku are buffered to a pH of 8 or greater by adding one of the bases identified above. In another embodiment, the high pH fluid is a solution of water, propylene glycol, hexanediol, butanediol, glycol ether, glycerol, a surfactant, and a base such as triethylamine, hydrazine, dimethylethanolamine, KOH, NaOH, etc. As used herein, the term "high pH fluid" refers to a liquid having a pH of at least 8 and no more than 12.

[0024] A process 500 for operating a printhead maintenance station that injects a high pH fluid into a printhead of an inkjet printer is shown in FIG. 5. In the description of a process, a statement that the process performs certain tasks or functions refers to a controller or general-purpose processor executing program instructions stored on a non-transitory computer-readable medium operatively connected to the controller or processor to manipulate data or operate one or more components in the printer to perform the task or function. The controller 80 described above can be such a controller or processor. Alternatively, a controller can be implemented with two or more processors and associated circuits and components, each configured to perform one or more tasks or functions described herein. Additionally, the steps of the method can be performed in any feasible chronological order, regardless of the order shown in the figures or the order in which the process is described.

[0025] The process 500 of FIG. 5 begins by detecting a signal that the printer is entering an extended period of printer inactivity (block 504). The printhead module is moved into position opposite the PHM 32 (block 508). A flushing port to the printhead cap is opened so that the high pH fluid fills the cap (block 512). The printhead is lowered so that the vent blocking members in the printhead cap block the manifold vents on the printhead and the high pH fluid contacts the nozzle plate of the printhead (block 516). A vacuum is applied to the ink supply lines and the high pH fluid is pumped into the printhead past the lock screen in the printhead (block 520). The printhead is raised sufficiently to interrupt the blocking action of the vent blocking members on the manifold so that the vacuum draws the high pH fluid through the vents and into the manifold (block 524). The vacuum to the ink supply lines is then released to move the meniscus of the high pH fluid back to the nozzle opening (block 528). Once the printer inactivity period has ended (block 532), the cap drain valve is opened to drain the high pH fluid from the printhead cap, and a known purge cycle is performed to flush and remove the high pH fluid from the printhead and the printhead nozzle plate (block 536). The printhead module can then be returned to the printzone for a printing operation.

[0026] It will be appreciated that variations of the above-disclosed and other features and functions, or alternatives thereof, may be desirably combined into many other different systems or applications. Various presently unforeseen substitutions, modifications, variations, or improvements may subsequently be made by those skilled in the art which are also intended to be encompassed by the following claims.

Claims

1. a printhead cap configured to cover a face of the printhead; an opening in the printhead cap; a printhead vent blocking member configured to block manifold vents in the printhead when the printhead is moved into engagement with the printhead vent blocking member; a valve configured to open and close, the valve positioned within the printhead cap such that when the valve is closed, the printhead cap allows the printhead cap to retain a volume of high pH fluid entering the printhead cap through the opening in the printhead cap and when the valve is open, the valve allows the high pH fluid to exit the printhead cap; Printhead maintenance station including:

2. The printhead maintenance station of claim 1 , wherein the printhead vent blocking member is made of a flexible material.

3. The printhead maintenance station of claim 2 , wherein the compliant material is either polyurethane or rubber.

4. 2. The printhead maintenance station of claim 1, wherein the opening in the printhead cap is configured to open to allow the high pH liquid to enter the printhead cap and to close to prevent the high pH liquid from flowing into the printhead cap.

5. 1. A method of operating a printhead maintenance station to inject a high pH liquid into a printhead for maintaining ink during extended periods of printer inactivity, comprising: filling a printhead cap having a manifold vent blocker with the high pH liquid; lowering a printhead onto the printhead cap to block manifold vents in the printhead and contact a nozzle plate of the printhead with the high pH fluid; applying a vacuum to an ink supply line of the printhead to draw the high pH fluid into the printhead; The method includes:

6. opening a port in the print head cap and filling the print head cap with the high pH liquid; The method of claim 5 further comprising:

7. The lowering of the print head comprises: lowering the print head until the manifold vent in the print head contacts the manifold vent blocking member; The method of claim 6 further comprising:

8. 8. The method of claim 7, further comprising continuing to apply the vacuum to the ink supply line until the high pH fluid has passed through a screen in the printhead.

9. moving the printhead away from the printhead cap to open the manifold vent in the printhead; continuing to apply the vacuum to the ink supply lines to draw the high pH liquid into the manifold in the printhead that is fluidly connected to the manifold vent; The method of claim 8 further comprising:

10. terminating application of the vacuum to the ink supply line to allow a meniscus of the high pH fluid to reside in a nozzle opening in the printhead; The method of claim 9 further comprising:

11. opening a print head cap drain valve to allow the high pH fluid to exit the print head cap; The method of claim 10 further comprising:

12. performing a purge cycle on the print head to flush the high pH fluid from the print head; The method of claim 11 further comprising:

13. 1. An inkjet printer, comprising: at least one printhead module configured with at least one printhead; a printhead maintenance module having a printhead cap having a manifold vent blocking member, an opening in the printhead cap, the printhead vent blocking member configured to block a manifold vent in the printhead when the at least one printhead is moved into engagement with the printhead vent blocking member, and a valve configured to open and close, the valve positioned in the printhead cap such that when the valve is closed, the printhead cap allows a volume of high pH fluid entering the printhead cap through the opening in the printhead cap and when the valve is open, allows the high pH fluid to exit the printhead cap; a controller operatively connected to the at least one printhead module and to the printhead maintenance station, the controller comprising: Filling the print head cap with the high pH liquid; lowering said at least one print head onto said print head cap to block manifold vents in said print head and contact a nozzle plate of said print head with said high pH fluid; applying a vacuum to an ink supply line of the printhead to draw the high pH fluid into the printhead; An inkjet printer configured as such.

14. The controller: Directing a high pH liquid through the opening in the print head cap to fill the print head cap with the high pH liquid. The inkjet printer of claim 13 further configured to:

15. The controller: lowering the at least one printhead until the manifold vent in the at least one printhead contacts the manifold vent blocking member in the printhead cap.

15. The inkjet printer of claim 14, further configured to:

16. The controller: Continue applying the vacuum to the ink supply lines until the high pH fluid has passed through a screen in the printhead.

16. The inkjet printer of claim 15, further configured to:

17. The controller: moving the print head away from the print head cap to open the manifold vent in the print head; continuing to apply the vacuum to the ink supply lines to draw the high pH liquid into the manifold in the printhead that is fluidly connected to the manifold vent.

20. The inkjet printer of claim 16, further configured as follows:

18. The controller: terminating application of the vacuum to the ink supply line to allow a meniscus of the high pH fluid to reside in a nozzle opening in the at least one printhead.

20. The inkjet printer of claim 17, further configured to:

19. The controller: Open the printhead cap drain valve to allow the high pH fluid to exit the printhead cap.

20. The inkjet printer of claim 18, further configured to:

20. The controller: performing a purge cycle on the print head to flush the high pH fluid from the print head; 20. The inkjet printer of claim 19, further configured to:

21. A high pH fluid used to maintain the print head during periods of inactivity of at least two hours, A fluid; a base added to the fluid to raise the pH level of the fluid to at least 8; 2. A high pH fluid comprising:

22. 22. The high pH fluid of claim 21, wherein the pH level of the fluid and base is 12 or less.

23. 23. The high pH fluid of claim 22, wherein the fluid is ink ejected by the print head to form an ink image.

24. 24. The high pH fluid of claim 23, wherein the base is selected from the group consisting of triethanolamine, triethylamine, diethylamine, dimethylethanolamine, KOH, or NaOH.

25. 22. The high pH fluid of claim 21, wherein the fluid is a print head cleaning solution.

26. 26. The high pH fluid of claim 25, wherein the base is selected from the group consisting of triethanolamine, triethylamine, diethylamine, dimethylethanolamine, KOH, or NaOH.

27. 22. The high pH fluid of claim 21, wherein the fluid is selected from the group consisting of water, propylene glycol, hexanediol, butanediol, glycol ethers, glycerol, and surfactants.

28. 28. The high pH fluid of claim 27, wherein the base is selected from the group consisting of triethylamine, hydrazine, dimethylethanolamine, KOH, and NaOH.

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