High-durability ink containment unit for use in an ink delivery system

BACKGROUND OF THE INVENTION

The present invention generally relates to ink printing technology, and more particularly to a specialized ink containment vessel for use in an ink delivery system which is resistant to the corrosive effects of ink, prevents air entry into the ink, avoids the evaporation of volatile ink components therefrom, and is dimensionally stable during production and thereafter. As a result, the overall longevity and operational efficiency of the entire ink delivery system is improved.

Substantial developments have been made in the field of electronic printing technology. A wide variety of highly-efficient printing systems currently exist which are capable of dispensing ink in a rapid and accurate manner. Thermal inkjet systems are especially important in this regard. Printing units using thermal inkjet technology basically involve an apparatus which includes at least one ink reservoir chamber in fluid communication with a substrate (preferably made of silicon) having a plurality of thin-film heating resistors thereon. The substrate and resistors are maintained within a structure which is conventionally characterized as a “printhead”. Selective activation of the resistors causes thermal excitation of the ink materials stored inside the reservoir chamber and expulsion thereof from the printhead. Representative thermal inkjet systems are discussed in U.S. Pat. No. 4,500,895 to Buck et al.; U.S. Pat. No. 4,794,409 to Cowger et al.; U.S. Pat. No. 4,509,062 to Low et al.; U.S. Pat. No. 4,929,969 to Morris; U.S. Pat. No. 4,771,295 to Baker et al.; U.S. Pat. No. 5,278,584 to Keefe et al.; and the

Hewlett

-

Packard Journal

, Vol. 39, No. 4 (August 1988), all of which are incorporated herein by reference.

The ink delivery systems described above (and other printing units using different ink ejection devices) typically include an ink containment unit (e.g. a housing, vessel, or tank) having a self-contained supply of ink therein in order to form an ink cartridge. In a standard ink cartridge, the ink containment unit is directly attached to the remaining components of the cartridge to produce an integral and unitary structure wherein the ink supply is considered to be “on-board”. However, in other cases, the ink containment unit will be provided at a remote location within the printer, with the containment unit being operatively connected to and in fluid communication with the printhead using one or more ink transfer conduits. These particular systems are conventionally known as “off-axis” printing units. Representative, non-limiting “off-axis” ink delivery systems are discussed in co-owned U.S. patent application Ser. No. 08/869,446 (filed on Jun. 5, 1997 and now U.S. Pat. No. 6,158,953) entitled “AN INK CONTAINMENT SYSTEM INCLUDING A PLURAL-WALLED BAG FORMED OF INNER AND OUTER FILM LAYERS” (Olsen et al.) and co-owned U.S. patent application Ser. No. 08/873,612 (filed Jun. 11, 1997and now U.S. Pat. No. 5,975,686) entitled “REGULATOR FOR A FREE-INK INKJET PEN” (Hauck et al.) which are all incorporated herein by reference. The present invention shall be applicable to both of these designs, and may likewise be used in connection with ink printing devices that employ non-thermal-inkjet technology. Accordingly, while the claimed invention shall be described herein with primary reference to thermal inkjet printing systems, it is likewise applicable to any ink delivery apparatus which employs a housing, vessel, or tank containing a supply of ink therein which has corrosive capabilities and volatile ink components.

An important consideration in the development of an ink containment unit for use with a thermal inkjet (or other type) of printing system is the ability of the containment unit to avoid substantial air introduction into the ink supply and printhead. Excessive air introduction (when reaching a critical volume) can cause a loss of system back-pressure which will typically result in operational failure of the ink ejection components and reduce overall printhead life. It is also important to prevent the evaporation of volatile components from the ink supply, with these components including water and organic solvents such as 2-pyrrolidone; 1,5-pentanediol; N-methyl pyrrolidone; 2-propanol; 2-ethyl-2-hydroxymethyl-1,3-propanediol; cyclohexanol, and others as discussed in considerable detail below. Solvent evaporation can result in a chemical deterioration of the ink supply which will reduce overall print quality and can cause premature failure of the ink delivery printhead. Accordingly, these factors must be carefully considered in any ink delivery system regardless of whether the ink containment unit (e.g. housing, vessel, or tank) is of the “on-board” variety or remotely positioned from the printhead.

Many ink cartridge units have employed rigid, thick-walled ink storage housings for containing ink therein which is present in “free flowing”, unconstrained form or held within a multi-cellular foam-type member. Representative ink cartridge units which employ these types of rigid ink containment systems are illustrated in U.S. Pat. Nos. 5,185,614 and 5,168,285. Plastic is commonly used to construct the housings associated with these and other cartridge units. Representative plastic compositions which have been employed in the past for this purpose include but are not limited to polytetrafluoroethylene (Teflon®), polystyrene plastic, polyethylene terephthalate, polysulfones, and polycarbonate compositions. While these materials typically have good physical strength characteristics, they may be subject to chemical deterioration, undesired fluid permeability problems, gas transfer into and out of the ink supply, and other related conditions depending on the particular ink composition being delivered. Should any of these difficulties actually occur, they will cause operational problems in the printing system of interest (including increased “down-time”, enhanced maintenance requirements, ink deterioration, and the like) as discussed above. Likewise, numerous materials are employed in traditional ink formulations which can be characterized as “corrosive” when placed in contact with plastic products (including those listed above). This “corrosion” (or, more specifically, chemical deterioration) is typically caused by the various organic solvents in the ink products which can create the problems outlined herein.

A substantial need has therefore existed for an ink containment unit applicable to both of the systems listed above (namely, self-contained and “off-axis” units) which is durable, impact-resistant, and able to (1) provide appropriate protection against ink corrosion problems; (2) present air from entering the ink supply; and (3) avoid the evaporation of volatile ink components including organic solvents and water from the ink. The present invention described below solves these problems in a unique and highly effective manner. Specifically, a novel ink containment unit (typically in the form of a housing, vessel, or tank) and ink containment method are provided which offer a solution to the problems outlined above including those involving the corrosive effects of ink materials. Furthermore, the compositions and materials discussed below which are used to produce the claimed ink containment vessels provide a considerable degree of thermal and dimensional stability during production and thereafter. In accordance with these benefits, high levels of operating efficiency, excellent print quality, and increased longevity are maintained in connection with the ink delivery systems under consideration. These and other benefits associated with the claimed invention (as well as the specific details thereof) shall be discussed in substantial detail below.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide an ink delivery system of improved operating efficiency and longevity.

It is another object of the invention to provide an improved ink containment unit (also characterized herein as a “housing”, “vessel”, or “tank”) for use in an ink delivery system which is applicable to a wide variety of different printing devices including both thermal inkjet and non-thermal-inkjet systems.

It is another object of the invention to provide an improved ink containment unit for use in an ink delivery system which employs ink supplies that are either “on-board” (e.g. directly attached to the printhead) or remotely connected to the printhead in an “off-axis” manner.

It is another object of the invention to provide an improved ink containment unit for use in an ink delivery system which is resistant to the corrosive effects of ink compositions.

It is another object of the invention to provide an improved ink containment unit for use in an ink delivery system which prevents the introduction of air into the unit so that high levels of print quality and prolonged printhead longevity can be maintained.

It is a further object of the invention to provide an improved ink containment unit for use in an ink delivery system which controls the evaporation of volatile ink components (including organic solvents and water) from the ink supply contained within the unit.

It is a further object of the invention to provide an improved ink containment unit for use in an ink delivery system which is substantially fluid-impermeable to the gases and liquids (e.g. water and/or organic solvents) that are typically associated with ink compositions.

It is a still further object of the invention to provide an improved ink containment unit for use in an ink delivery system which is thermally and dimensionally stable during production and thereafter. Specifically, the unit is not subject to undesired deformation when exposed to heat and/or the physical forces that are normally encountered during production and use.

It is a still further object of the invention to provide an improved ink containment unit for use in an ink delivery system which is durable, corrosion resistant, and capable of effective use in a wide variety of ink delivery systems.

It is an even further object of the invention to provide an improved ink containment unit for use in an ink delivery system which is readily manufactured in a cost-effective manner using mass-production techniques.

It is an even further object of the invention to provide an improved ink containment unit for use in an ink delivery system which is capable of achieving the benefits listed above in connection with many different ink compositions having multiple ingredients therein.

It is an even further object of the invention to provide an improved ink containment unit for use in an ink delivery system which is capable of being fabricated in many different shapes, sizes, capacities, and design configurations so that the unit can be employed in multiple printing systems including self-contained thermal inkjet cartridges and “off-axis”devices as previously noted.

It is an even further object of the invention to provide an ink delivery system in the form of a printhead having the claimed ink containment unit operatively connected thereto so that the foregoing benefits can be achieved.

It is an even further object of the invention to provide an effective method for preventing the introduction of air into an ink supply within an ink delivery system and controlling the evaporation of volatile ink components therefrom by retaining the ink supply inside the novel ink containment unit discussed above.

The unique ink containment system of the present invention involves a storage vessel which is made from specialized materials (designated as “barrier compositions”) designed to provide improved durability, chemical-resistance, and dimensional stability. The novel features of this vessel (which may also be characterized as a “housing”, “tank” or “containment unit”) will now be summarized. More detailed information along with a discussion of specific construction materials and other important parameters will be provided below in the Detailed Description of Preferred Embodiments section.

In accordance with the invention, a highly effective ink containment vessel is provided for use in an ink delivery system. The term “ink delivery system” shall, without limitation, involve a wide variety of different devices including cartridge units of the “self-contained” variety having a supply of ink stored directly therein. Also encompassed within this term are printing units of the “off-axis” type which employ a printhead connected by one or more conduit members (or similar structures) to a remotely-positioned ink containment unit in the form of a tank, vessel, housing, or other equivalent structure as previously indicated. It should also be noted that the claimed ink containment vessel shall be construed to encompass any applicable cap members or “crowns” that are optionally employed to seal the system as further summarized below.

The novel ink containment vessel described herein which is made from the claimed barrier compositions shall also not be restricted to any particular sizes, shapes, capacities, or overall configurations which will be selected in accordance with the particular ink delivery system under consideration. Finally, while the present invention shall be discussed below with primary reference to systems employing thermal inkjet technology, it is likewise applicable to non-thermal-inkjet printing units (examples provided below) which include a supply of ink that can cause the previously-listed problems (e.g. corrosion, evaporation of volatile ink components, undesired fluid permeability, and the like). Thus, in its broadest sense, the invention described and claimed herein is widely applicable to a diverse group of printing systems, applications, and environments.

The claimed ink containment vessel made from the specialized chemical compositions of interest includes an internal cavity surrounded by a side wall. The side wall is optimally of unitary, single-piece construction. The particular compositions which are employed to produce the side wall of the ink containment vessel will now be discussed in detail, with the use of these materials constituting a departure from prior ink containment systems. All of these materials have a number of common attributes, namely, their ability to produce an ink containment vessel which is resistant to the corrosive effects of ink materials, is substantially fluid/gas impermeable, is dimensionally stable, and provides all of the other benefits listed above. The claimed materials are therefore related in view of their functional attributes and other important features. For this reason, they all constitute “barrier compositions” in accordance with their ability to store ink materials within the claimed vessels in a highly efficient and ink-resistant manner. In a first embodiment, the side wall of the ink containment vessel is constructed from a material designated herein as “polyethylene naphthalate” (e.g. “PEN”) which is also known as a homopolymer of dimethyl 2,6-naphthalenedicarboxylate and ethylene glycol. It specifically has the following chemical structure (with either alternative being applicable):

In a non-limiting preferred embodiment, n=about 10-1000 in the above-listed structure.

Regarding the chemical characteristics of this material, they involve a tensile strength of 32,000 lbs./sq. in. and a tensile modulus of 750,000 lbs./sq. in. The water vapor transmission rate of polyethylene naphthalate has been reported in the vicinity of 3.6 gm/m

2

/day. These parameters were determined according to a standardized procedure referenced in ASTM D-882-88. Polyethylene naphthalate also has a glass transition temperature (T

g

) of approximately 120° C. and a melting temperature of 262° C. Compared to, for example, polyethylene terephthalate (“PETE”), polyethylene naphthalate has a 43° C. higher glass transition temperature, a 50% higher tensile modulus, a 33% higher tensile strength, a five-fold improvement in its ability to function as a gas barrier (as measured in accordance with biaxially-oriented films), a three-fold improvement in hydrolysis resistance, a four-fold enhancement in moisture barrier capacity, and greater chemical resistance. In this regard, polyethylene naphthalate is highly beneficial when used to manufacture the side wall of an ink containment vessel in accordance with its considerable degree of chemical resistance to the corrosive effects of ink materials, the ability to withstand relatively high temperatures which are traditionally encountered during the manufacturing processes associated with ink containment vessel fabrication, low moisture absorption, low water vapor transmission, a high retention of tensile strength even after being exposed to hydrolysis conditions, a high continuous use temperature in an electrical environment, and the ability to be formed into many shapes in a rapid and effective manner using conventional injection molding techniques. Polyethylene naphthalate provides all of these benefits yet is economical from a material cost standpoint. Thus, the use of polyethylene naphthalate for the purposes specified herein offers many advantages and represents a significant technical advance in the art of ink containment vessel fabrication.

While polyethylene naphthalate may be obtained from a number of different sources, it is commercially available from, for example, Imperial Chemical Industries (“ICI”) of Wilmington, DE (USA) under the trademark “KALADEX” and from Amoco Polymers, Inc. of Alpharetta, Ga. (USA).

At this point, it should be emphasized that the present invention and its various embodiments shall not be restricted to any particular compositions, materials, proportions, amounts, and other parameters unless otherwise stated herein. All numerical values and ranges presented below are provided for example purposes only and represent preferred embodiments of the invention designed to achieve maximum operational efficiency. Likewise the various embodiments of this invention shall not be limited to any particular construction techniques in connection with the claimed ink containment vessels and specialized barrier compositions listed herein. However, in a preferred embodiment designed for use on a mass-production scale, standard injection molding processes that are known in the art for plastic component fabrication can be employed to manufacture the claimed ink containment vessels including any applicable cap members or “crowns” associated therewith.

In a second embodiment (which shall be implemented in accordance with routine preliminary pilot testing taking into account the chemical characteristics of the ink compositions under consideration), the side wall of the ink containment vessel may be constructed from at least one or more “liquid crystal polymers”. The term “liquid crystal polymer” shall be defined herein to involve a class of thermoplastic polymers that exhibit a highly ordered structure in both the melt and solid states and incorporate an aromatic backbone. In particular, liquid crystal polymers are made up entirely of aromatic monomers. The aromatic character of liquid crystal polymers as a general class contributes to the beneficial ink-resistant characteristics thereof, excellent mechanical properties, and a high degree of thermal/thermooxidative stability. The ordered character of liquid crystal polymers is likewise another distinguishing feature of these materials relative to other polymeric compounds. Accordingly, liquid crystal polymers are readily molded or fabricated more effectively in a wide variety of configurations using standard production methods. The term “aromatic” as used in this discussion shall encompass materials which contain one or more benzene ring units therein. In addition, from a structural standpoint as discussed in the

Encyclopedia of Polymer Science and Engineering

(Kroschwitz, J. ed.), Vol. 9 (entitled “Liquid Crystal Polymers to Mining Applications), John Wiley & Sons, Inc., New York (1987), pp. 1-8 (incorporated herein by reference), liquid crystal polymers shall further be defined to involve a “succession of para-oriented ring structures to give a stiff chain with a high axial ratio (ratio of length of molecule to its width, aspect ratio) x.” As further stated in this reference, “The common structural feature of low molecular weight LC compounds is asymmetry of molecular shape, manifested either as rods characterized by a uniaxial order with an axial ratio usually greater than three or by thin platelets with biaxial order.”

Liquid crystal polymers are particularly useful in producing the claimed ink containment vessels when ink materials are employed that are especially corrosive. The term “corrosive” shall again involve the ability of a particular chemical to dissolve or otherwise deteriorate a given material. Accordingly, the use of liquid crystal polymers to form the side wall of an ink containment vessel (particularly in thermal inkjet systems) offers many advantages and therefore constitutes another substantial advance in the art of ink delivery technology.

This embodiment of the invention shall not be restricted to any particular liquid crystal polymers or combinations thereof. Either one liquid crystal polymer or multiple liquid crystal polymers may be used in combination without limitation. Exemplary and non-limiting examples of liquid crystal polymers which can be employed for the construction of an ink containment vessel as indicated above shall involve the following commercially-available liquid crystal polymer materials:

1. A product sold under the name/trademark “Vectra” by the Hoechst Co. of Summit, N.J. (USA). From a chemical standpoint, this proprietary composition essentially consists of a wholly aromatic polyester/polyamide made from aromatic diacids, aromatic dialcohols, and aromatic moieties with two different substituents, with the substituents involving alcohols, acids, or amines. In particular, the “Vectra” line of liquid crystal polymers involves several compositions including but not limited to: (A) p-hydroxybenzoic acid modified with 2-oxynaphthalene-6-carbonyl units; or (B) 2,6-dioxynaphthalene modified with terephthaloyl units.

2. A product sold under the name/trademark “Xydar” by Amoco Polymers, Inc. of Alpharetta, Ga. (USA). Chemically, this composition basically consists of a product of the modification of p-hydrobenzoic acid with 4,4′-biphenol and terephthalic acid.

3. A product sold under the name/trademark “Zenite” by E. I. DuPont de Nemours & Company of Wilmington, Del. (USA).

Other liquid crystal polymers which may be employed include but are not limited to the following materials: aromatic polyamides, aromatic polyoxamides, aromatic polyhydrazides, aromatic poly(oxalic hydrazides), aromatic poly(amine hydrazides), poly(p-phenylenebenzobisthiazole), and polyimides.

Notwithstanding the materials listed above, the present invention shall not be restricted to any particular liquid crystal polymers or mixtures thereof with many commercial compositions suitable for this purpose being applicable. A number of these materials are proprietary in nature, yet fall within the basic definition listed above and also provide the foregoing benefits.

Finally, in a third embodiment, the novel ink containment vessels of the present invention may be constructed from polyethylene naphthalate in combination with at least one or more liquid crystal polymers as defined above to form a polyethylene naphthalate/liquid crystal polymer “blend”. All of the information, parameters, examples, commercial sources, and other data presented above regarding polyethylene naphthalate and liquid crystal polymers as employed in the first and second embodiments shall be equally applicable to and incorporated by reference in this embodiment. The use of at least one liquid crystal polymer in combination with polyethylene naphthalate is designed to further enhance the beneficial characteristics discussed above (including improved chemical resistance to ink materials and the control of gas/liquid permeability problems). In particular, blends involving polyethylene naphthalate and at least one liquid crystal polymer in combination enable the best features of both compositions to be employed in a single mixed compound. Thus, by using a blend of both materials, the resulting product (from a chemical composition standpoint) can be appropriately “adjusted” as needed to properly tailor the ink containment vessel to the type of ink composition under consideration. In other words, by selectively controlling the amount of each material in the chosen blend, the desired characteristics to be imparted to the ink containment vessel can be accurately selected in accordance with preliminary pilot studies on the ink compositions being delivered. Thus, the use of at least one liquid crystal polymer in combination with polyethylene naphthalate to produce the side wall of an ink containment vessel provides an even further advance in the art of ink delivery technology. Both of these materials in combination produce unexpectedly superior results as indicated above.

In accordance with the present embodiment which again involves a combination of (1) polyethylene naphthalate; and (2) at least one or more liquid crystal polymers, the invention shall not be restricted to any particular numerical proportions. However, in a representative example designed to provide optimum results, the side wall of the selected ink containment vessel will contain about 10-50% by weight polyethylene naphthalate and about 50-90% by weight total liquid crystal polymer (whether a single material is used or multiple polymers are employed in combination, with the range listed above involving the total amount of liquid crystal polymers included in the combination). Any determination regarding the proportions of polyethylene naphthalate and liquid crystal polymers in this embodiment shall be undertaken in accordance with routine preliminary testing taking into account the ink materials under consideration and their chemical characteristics.

Regarding the construction of an ink delivery system which incorporates the claimed compositions and ink containment vessels, many different systems (both thermal inkjet and non-thermal-inkjet) may be employed for this purpose including those described in the foregoing issued U.S. patents. A representative and preferred apparatus will comprise a printhead having at least one ink ejector for expelling ink on demand from the printhead and an ink containment vessel operatively connected to and in fluid communication with the printhead. The novel ink containment vessel will again include an internal cavity therein surrounded by a side wall which is used to retain an ink supply within the vessel. The side wall (which is specifically designed to prevent air and volatile ink components from passing therethrough along with the other benefits listed above) is constructed from the specialized barrier compositions listed above. These materials again include: (1) polyethylene naphthalate; (2) at least one liquid crystal polymer; or (3) polyethylene naphthalate in combination with at least one or more liquid crystal polymers to form a “blend” as previously defined. Furthermore, the term “operatively connected” which is used to specify the interrelationship between the printhead and the ink containment vessel shall be broadly construed to encompass: (A) a system in which the ink containment vessel is directly attached to and in fluid communication with the printhead to form, for example, a single cartridge unit having an “on-board” ink supply; and (B) an “off-axis” system as previously discussed in which the ink containment vessel is remotely spaced from the printhead and not “directly” attached thereto. In system (B), the ink containment vessel is preferably in fluid communication with the printhead using at least one ink transfer conduit connected to and between the printhead and the vessel. Both of these systems shall be applicable to all of the various embodiments of the claimed ink containment unit and methods for ink preservation.

The present invention shall likewise encompass a general method for preventing the evaporation and leakage of volatile ink components (e.g. organic solvents and/or water) from an ink delivery system having a supply of ink therein. The claimed method also avoids the introduction of air into the ink supply and improves the overall chemical-resistance of the system. These goals are accomplished by: (1) providing an ink delivery system of the type discussed above which includes a printhead having at least one ink ejector for expelling ink on demand from the printhead; and (2) storing a supply of ink within an ink containment vessel operatively connected to and in fluid communication with the printhead wherein the ink containment vessel includes a side wall which prevents air and volatile ink components from passing therethrough. The side wall is again constructed from the following barrier compositions: [A] polyethylene naphthalate; [B] at least one or more liquid crystal polymers; or [C] polyethylene naphthalate in combination with at least one or more liquid crystal polymers to form a “blend”. Accordingly, all of the information presented above regarding representative ink delivery systems, ink containment units, and preferred barrier compositions is incorporated by reference relative to the claimed method(s). These methods shall not be limited to any specific materials, construction methods, component arrangements, or other parameters unless otherwise noted herein.

The present invention represents a significant advance in the art of ink printing technology and the generation of high-quality images. The structures, components, and methods outlined in detail below provide many important benefits including (1) resistance to the corrosive effects of ink materials; (2) the prevention of air introduction into the ink supply contained within the printing system; (3) the avoidance of evaporative ink losses; and (4) the ability to prevent fluid leakage from the ink supply. In addition, containment vessels produced from the claimed compositions are dimensionally stable during and after production notwithstanding the application of heat and/or physical force to the vessels. As a result, high levels of operating efficiency, print quality, and longevity are maintained in connection with the ink delivery system. These and other benefits, objects, features, and advantages will now be discussed in the following Brief Description of the Drawings and Detailed Description of Preferred Embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

Any reference numbers carried over from one drawing figure to other drawing figures shall constitute common subject matter applicable to all of the drawing figures under consideration. Likewise, the drawing figures presented herewith are shown in enlarged schematic format for illustrative purposes.

FIG. 1

is a schematically-illustrated, exploded perspective view of a representative ink delivery system in the form of an ink cartridge which is suitable for use with the components and methods of the present invention. The ink cartridge of

FIG. 1

has an ink containment vessel directly attached to the cartridge so that an “on-board” ink supply is provided.

FIG. 2

is a schematically-illustrated perspective view of an alternative ink containment vessel which may be constructed from the specialized barrier compositions described herein.

FIG. 3

is a partial cross-sectional view of the ink containment vessel shown in

FIG. 2

taken along lines 3—3 which is operatively connected to a printhead using at least one ink transfer conduit in an “off-axis” system.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

The present invention involves a high-durability ink containment unit in the form of a vessel, housing, or tank for use in an ink delivery system including those which employ thermal inkjet technology. For the sake of convenience, the term “ink containment vessel” will be used hereinafter with the understanding that it is synonymous with all of the other terms listed above. The novel ink containment vessel is produced from highly-specialized chemical compounds which are not subject to chemical deterioration caused by the corrosive effects of ink materials. Likewise, the chemical compositions described herein substantially prevent the passage of air therethrough (and into the ink supply of interest) while simultaneously controlling the escape of volatile ink components including organic solvents and water. In this manner, the longevity of the entire printing system is extended along with the maintenance of high print quality levels. Furthermore, the claimed ink containment vessels are fluid-impermeable and dimensionally stable during production and thereafter when exposed to heat and/or physical force. The term “dimensionally stable” shall involve a situation where the ink containment vessel does not experience undesired deformation when heated and/or exposed to physical forces normally encountered during production and use. While the present invention shall be described below with primary reference to thermal inkjet technology, many different ink delivery systems may be employed with equivalent results provided that the selected systems include a printhead having at least one ink ejector associated with the printhead. The term “ink ejector” shall involve any component, device, element, or structure which may be used to expel ink on-demand from the printhead. For example, in a thermal inkjet printing system, “ink ejector” will encompass the use of one or more selectively-energizable thin-film heating resistors as outlined in greater detail below. In this regard, the materials, methods, and structures of the invention are not “system-specific” which will become readily apparent from the detailed discussion presented herein. To provide a clear and complete understanding of the invention, the following description will be divided into three sections, namely, (1) “A. A General Overview of Thermal Inkjet Technology and Ink Compositions Associated Therewith”; (2) “B. The Novel Ink Containment Vessels”; and (3) “C. Additional Information and Methods of Use.”

A. A General Overview of Thermal Inkjet Technology and Ink Compositions Associated Therewith

The present invention is again applicable to a wide variety of ink cartridge systems which include (1) a printhead; (2) at least one “ink ejector” associated with the printhead; and (3) an ink containment vessel of the type described herein which is operatively connected to and in fluid communication with the printhead. The ink containment vessel may be directly attached to the printhead or remotely connected thereto in an “off-axis” system using one or more ink transfer conduits. The phrase “operatively connected” as it applies to the printhead and ink containment vessel shall encompass both of these variants and equivalent structures. As previously stated, the term “ink ejector” is defined to involve any component, system, or device which selectively ejects or expels ink on-demand from the printhead. Thermal inkjet cartridges which use multiple heating resistors as ink ejectors are preferred for this purpose. However, the claimed invention shall not be restricted to any particular ink ejectors or ink printing technologies. A wide variety of different ink delivery devices may be encompassed within the invention including but not limited to piezoelectric drop systems of the general type disclosed in U.S. Pat. No. 4,329,698 to Smith, dot matrix devices of the variety described in U.S. Pat. No. 4,749,291 to Kobayashi et al., as well as other comparable and functionally equivalent systems designed to deliver ink using one or more ink ejectors. The specific operating components associated with these alternative systems (e.g. the piezoelectric elements in the system of U.S. Pat. No. 4,329,698) shall be encompassed within the term “ink ejectors” as previously defined.

To facilitate a complete understanding of the claimed components and methods as they apply to thermal inkjet technology (which is the preferred system of primary interest), an overview of thermal inkjet technology will now be provided. A representative ink delivery system in the form of a thermal inkjet cartridge unit is illustrated in

FIG. 1

at reference number

10

. It shall be understood that cartridge

10

is presented herein for example purposes and is non-limiting. Cartridge

10

is shown in schematic format in

FIG. 1

, with more detailed information regarding cartridge

10

and its various features (as well as similar systems) being provided in U.S. Pat. No. 4,500,895 to Buck et al.; U.S. Pat. No. 4,794,409 to Cowger et al.; U.S. Pat. No. 4,509,062 to Low et al.; U.S. Pat. No. 4,929,969 to Morris; U.S. Pat. No. 4,771,295 to Baker et al.; U.S. Pat. No. 5,278,584 to Keefe et al.; and the

Hewlett

-

Packard Journal,

Vol. 39, No. 4 (August 1988), all of which are incorporated herein by reference.

With continued reference to

FIG. 1

, the cartridge

10

first includes an ink containment vessel

11

in the form of a housing

12

which is manufactured from the specialized barrier compositions discussed below. As noted above, the housing

12

shall constitute the ink containment unit of the invention, with the terms “ink containment unit”, “housing”, “vessel”, and “tank” all being considered equivalent from a functional and structural standpoint. The housing

12

further comprises a top wall

16

, a bottom wall

18

, a first side panel

20

, and a second side panel

22

. In the embodiment of

FIG. 1

, the top wall

16

and the bottom wall

18

are substantially parallel to each other. Likewise, the first side panel

20

and the second side panel

22

are also substantially parallel to each other.

The housing

12

additionally includes a front wall

24

and a rear wall

26

which is optimally parallel to the front wall

24

as illustrated. Surrounded by the front wall

24

, rear wall

26

, top wall

16

, bottom wall

18

, first side panel

20

, and second side panel

22

is an interior chamber or compartment

30

within the housing

12

(shown in phantom lines in

FIG. 1

) which is designed to retain a supply of an ink composition

32

therein that is either in unconstrained (e.g. “free-flowing”) form or retained within a multicellular foam-type structure.

The front wall

24

also includes an externally-positioned, outwardly-extending printhead support structure

34

which comprises a substantially rectangular central cavity

50

. The central cavity

50

includes a bottom wall

52

shown in

FIG. 1

with an ink outlet port

54

therein. The ink outlet port

54

passes entirely through the housing

12

and, as a result, communicates with the compartment

30

inside the housing

12

so that ink materials can flow outwardly from the compartment

30

through the ink outlet port

54

. Also positioned within the central cavity

50

is a rectangular, upwardly-extending mounting frame

56

, the function of which will be discussed below. As schematically shown in

FIG. 1

, the mounting frame

56

is substantially even (flush) with the front face

60

of the printhead support structure

34

. The mounting frame

56

specifically includes dual, elongate side walls

62

,

64

.

With continued reference to

FIG. 1

, fixedly secured to housing

12

of the ink cartridge

10

(e.g. attached to the outwardly-extending printhead support structure

34

) is a printhead generally designated in

FIG. 1

at reference number

80

. For the purposes of this invention and in accordance with conventional terminology, the printhead

80

actually comprises two main components fixedly secured together (with certain sub-components positioned therebetween). The first main component used to produce the printhead

80

consists of a substrate

82

preferably manufactured from silicon. Secured to the upper surface

84

of the substrate

82

using standard thin film fabrication techniques is a plurality of individually-energizable thin-film resistors

86

which function as “ink ejectors” and are preferably fabricated from a tantalum-aluminum composition known in the art for resistor construction. Only a small number of resistors

86

are shown in the schematic representation of

FIG. 1

, with the resistors

86

being presented in enlarged format for the sake of clarity. Also provided on the upper surface

84

of the substrate

82

using conventional photolithographic techniques is a plurality of metallic conductive traces

90

(e.g. circuit elements) which electrically communicate with the resistors

86

. The conductive traces

90

likewise communicate with multiple metallic pad-like contact regions

92

positioned at the ends

94

,

95

of the substrate

82

on the upper surface

84

. The function of all these components which, in combination, are collectively designated herein as a “resistor assembly”

96

will be summarized further below.

Many different materials and design configurations may be used to construct the resistor assembly

96

, with the present invention not being restricted to any particular elements, materials, and components for this purpose. However, in a preferred, representative, and non-limiting embodiment, the resistor assembly

96

will be approximately 0.5 inches long, and will likewise contain 300 resistors

86

thus enabling a resolution of 600 dots per inch (“DPI”). The substrate

82

containing the resistors

86

thereon will preferably have a width “W” (

FIG. 1

) which is less than the distance “D” between the side walls

62

,

64

of the mounting frame

56

. As a result, ink flow passageways are formed on both sides of the substrate

82

so that ink flowing from the ink outlet port

54

in the central cavity

50

can ultimately come in contact with the resistors

86

. It should also be noted that the substrate

82

may include a number of other components thereon (not shown) depending on the type of ink cartridge

10

under consideration. For example, the substrate

82

may likewise comprise a plurality of logic transistors for precisely controlling operation of the resistors

86

, as well as a “demultiplexer” of conventional configuration as discussed in U.S. Pat. No. 5,278,584. The demultiplexer is used to demultiplex incoming multiplexed signals and thereafter distribute these signals to the various thin film resistors

86

. The use of a demultiplexer for this purpose enables a reduction in the complexity and quantity of the circuitry (e.g. contact regions

92

and traces

90

) formed on the substrate

82

.

Securely affixed to the upper surface

84

of the substrate

82

(with a number of intervening material layers therebetween including an ink barrier layer) is the second main component of the printhead

80

. Specifically, an orifice plate

104

is provided as shown in

FIG. 1

which is used to distribute the selected ink compositions to a designated print media material (e.g. paper). In accordance with the claimed invention, the orifice plate

104

consists of a panel member

106

(illustrated schematically in

FIG. 1

) which is manufactured from one or more metal compositions (e.g. gold-plated nickel [Ni] and the like). In a typical and non-limiting representative embodiment, the orifice plate

104

will have a length “L” of about 5-30 mm and a width “W

1

” of about 3-15 mm. However, the claimed invention shall not be restricted to any particular orifice plate parameters unless otherwise indicated herein.

The orifice plate

104

further comprises at least one and preferably a plurality of openings or “orifices” therethrough which are designated at reference number

108

. These orifices

108

are shown in enlarged format in FIG.

1

. Each orifice

108

in a representative embodiment will have a diameter of about 0.01-0.05 mm. In the completed printhead

80

, all of the components listed above are assembled so that each of the orifices

108

is aligned with at least one of the resistors

86

(e.g. “ink ejectors”) on the substrate

82

. As result, energization of a given resistor

86

will cause ink expulsion from the desired orifice

108

through the orifice plate

104

. The claimed invention shall not be limited to any particular size, shape, or dimensional characteristics in connection with the orifice plate

104

and shall likewise not be restricted to any number or arrangement of orifices

108

. In an exemplary embodiment as presented in

FIG. 1

, the orifices

108

are arranged in two rows

110

,

112

on the panel member

106

associated with the orifice plate

104

. If this arrangement of orifices

108

is employed, the resistors

86

on the resistor assembly

96

(e.g. the substrate

82

) will also be arranged in two corresponding rows

114

,

116

so that the rows

114

,

116

of resistors

86

are in substantial registry with the rows

110

,

112

of orifices

108

. Further general information concerning this type of metallic orifice plate system is provided in, for example, U.S. Pat. No. 4,500,895 to Buck et al. which is incorporated herein by reference.

It should also be noted for background purposes that, in addition to the systems discussed above which involve metal orifice plates, alternative printing units have effectively employed orifice plate structures constructed from non-metallic organic polymer compositions. These structures typically have a representative and non-limiting thickness of about 1.0-2.0 mils. In this context, the term “non-metallic” will encompass a product which does not contain any elemental metals, metal alloys, or metal amalgams. The phrase “organic polymer” shall involve a long-chain carbon-containing structure of repeating chemical subunits. A number of different polymeric compositions may be employed for this purpose. For example, non-metallic orifice plate members may be manufactured from the following compositions: polytetrafluoroethylene (e.g. Teflon®), polyimide, polymethylmethacrylate, polycarbonate, polyester, polyamide, polyethylene terephthalate, or mixtures thereof. Likewise, a representative commercial organic polymer (e.g. polyimide-based) composition which is suitable for constructing a non-metallic organic polymer-based orifice plate member in a thermal inkjet printing system is a product sold under the trademark “KAPTON” by E. I. du Pont de Nemours & Company of Wilmington, Del. (USA). Further data regarding the use of non-metallic organic orifice plate systems is provided in U.S. Pat. No. 5,278,584 (incorporated herein by reference).

With continued reference to

FIG. 1

, a film-type flexible circuit member

118

is likewise provided in connection with the cartridge

10

which is designed to “wrap around” the outwardly-extending printhead support structure

34

in the completed ink cartridge

10

. Many different materials may be used to produce the circuit member

118

, with representative (non-limiting) examples including polytetrafluoroethylene (e.g. Teflon®), polyimide, polymethylmethacrylate, polycarbonate, polyester, polyamide, polyethylene terephthalate, or mixtures thereof. Likewise, a representative commercial organic polymer (e.g. polyimide-based) composition which is suitable for constructing the flexible circuit member

118

is a product sold under the trademark “KAPTON” by E. I. du Pont de Nemours & Company of Wilmington, Del. (USA) as previously noted. The flexible circuit member

118

is secured to the printhead support structure

34

by adhesive affixation using conventional adhesive materials (e.g. epoxy resin compositions known in the art for this purpose). The flexible circuit member

118

enables electrical signals to be delivered and transmitted from the printer unit (not shown) to the resistors

86

(or other ink ejectors) on the substrate

82

as discussed below. The film-type flexible circuit member

118

further includes a top surface

120

and a bottom surface

122

(FIG.

1

). Formed on the bottom surface

122

of the circuit member

118

and shown in dashed lines in

FIG. 1

is a plurality of metallic (e.g. gold-plated copper) circuit traces

124

which are applied to the bottom surface

122

using known metal deposition and photolithographic techniques. Many different circuit trace patterns may be employed on the bottom surface

122

of the flexible circuit member

118

, with the specific pattern depending on the particular type of ink cartridge

10

and printing system under consideration. Also provided at position

126

on the top surface

120

of the circuit member

118

is a plurality of metallic (e.g. gold-plated copper) contact pads

130

. The contact pads

130

communicate with the underlying circuit traces

124

on the bottom surface

122

of the circuit member

118

via openings or “vias” (not shown) through the circuit member

118

. During use of the ink cartridge

10

in a printer unit, the pads

130

come in contact with corresponding printer electrodes in order to transmit electrical control signals from the printer unit to the contact pads

130

and traces

124

on the circuit member

118

for ultimate delivery to the resistor assembly

96

. Electrical communication between the resistor assembly

96

and the flexible circuit member

118

will again be outlined below.

Positioned within the middle region

132

of the film-type flexible circuit member

118

is a window

134

which is sized to receive the orifice plate

104

therein. As shown schematically in

FIG. 1

, the window

134

includes an upper longitudinal edge

136

and a lower longitudinal edge

138

. Partially positioned within the window

134

at the upper and lower longitudinal edges

136

,

138

are beam-type leads

140

which, in a representative embodiment, are gold-plated copper and constitute the terminal ends (e.g. the ends opposite the contact pads

130

) of the circuit traces

124

positioned on the bottom surface

122

of the flexible circuit member

118

. The leads

140

are designed for electrical connection by soldering, thermocompression bonding, and the like to the contact regions

92

on the upper surface

84

of the substrate

82

associated with the resistor assembly

96

. As a result, electrical communication is established from the contact pads

130

to the resistor assembly

96

via the circuit traces

124

on the flexible circuit member

118

. Electrical signals from the printer unit (not shown) can then travel via the conductive traces

90

on the substrate

82

to the resistors

86

so that on-demand heating (energization) of the resistors

86

can occur.

It is important to emphasize that the present invention shall not be restricted to the specific printhead

80

illustrated in FIG.

1

and discussed above, with many other printhead designs also being suitable for use in accordance with the invention. The printhead

80

of

FIG. 1

is provided for example purposes and shall not limit the invention in any respect. Likewise, it should also be noted that if a non-metallic organic polymer-type orifice plate system is desired, the orifice plate

104

and flexible circuit member

118

can be manufactured as a single unit as discussed in U.S. Pat. No. 5,278,584.

The last major step in producing the completed printhead

80

involves physical attachment of the orifice plate

104

in position on the underlying portions of the printhead

80

so that the orifices

108

are in precise alignment with the resistors

86

on the substrate

82

as previously noted. Attachment of these components together may likewise be accomplished through the use of conventional adhesive materials (e.g. epoxy and/or cyanoacrylate adhesives known in the art for this purpose).

As a final note regarding ink cartridge

10

, the rear wall

26

shown in

FIG. 1

may involve a separately-produced structure in the form of a cap member or “crown” that is affixed in position to the other portions of the housing

12

by conventional thermal welding process or the use of adhesives (e.g. standard epoxy resins or cyanoacrylate materials). In accordance with the inventive concepts disclosed herein, the terms “ink containment unit”, “housing”, “vessel”, “tank”, and the like shall be construed (if desired and appropriate) to likewise encompass any cap members or “crowns” that are optionally employed to seal the system.

The ink cartridge

10

discussed above in connection with

FIG. 1

involves a “self-contained” ink delivery system which includes an “on-board” supply of ink. The claimed invention may likewise be used with other systems (both thermal inkjet and non-thermal-inkjet) which employ a printhead and a supply of ink stored within an ink containment vessel that is remotely spaced but operatively connected to and in fluid communication with the printhead. Fluid communication is accomplished using one or more tubular conduits. An example of such a system is disclosed in co-owned U.S. patent application Ser. No. 08/869,446 (filed on Jun. 5, 1997 and now U.S. Pat. No. 6,158,853) entitled “AN INK CONTAINMENT SYSTEM INCLUDING A PLURAL-WALLED BAG FORMED OF INNER AND OUTER FILM LAYERS” (Olsen et al.) and co-owned U.S. patent application Ser. No. 08/873,612 (filed Jun. 11, 1997 and now U.S. Pat. No. 5,975,686) entitled “REGULATOR FOR A FREE-INK INKJET PEN” (Hauck et al.) which are all incorporated herein by reference. This type of “remote” system (which is basically known as an “off-axis” unit) involves a tank-like housing containing a supply of ink therein that is operatively connected to and in fluid communication with a printhead containing at least one ink ejector as defined above. Representative ink ejectors include the resistor units employed in thermal inkjet systems and other devices (e.g. piezoelectric elements and the like). Accordingly, the main difference between an “off-axis” system and the apparatus

FIG. 1

is the proximity and orientation of the ink containment vessel relative to the printhead.

With reference to

FIGS. 2-3

, an alternative ink delivery system is shown which includes a tank-like ink containment vessel

170

that is designed for remote operative connection (preferably on a gravity feed or other comparable basis) to a selected printhead. Again, the terms “ink containment unit”, “vessel”, “housing”, and “tank” shall be considered equivalent in this case. The printhead may be of a thermal inkjet type or other variety as previously noted. The ink containment vessel

170

is configured in the form of an outer shell or housing

172

which includes a main body portion

174

and a top panel member

176

having an inlet/outlet port

178

passing therethrough (FIG.

3

). While this embodiment shall not be restricted to any particular assembly methods in connection with the housing

172

, the top panel member

176

is optimally produced as a separate structure from the main body portion

174

. The top panel member

176

is thereafter secured to the main body portion

174

as illustrated in

FIG. 3

using known thermal welding processes or conventional adhesives (e.g. epoxy resin or cyanoacrylate compounds). However, the top panel member

176

shall, in a preferred embodiment, be considered part of the overall ink containment vessel

170

/housing

172

.

With continued reference to

FIG. 3

, the housing

172

also has an internal chamber or cavity

180

therein for storing a supply of an ink composition

32

. In addition, the housing

172

further includes an outwardly-extending tubular member

182

which passes through the top panel member

176

and, in a preferred embodiment, is integrally formed therein. The term “tubular” as used throughout this description shall be defined to encompass a structure which includes at least one or more central passageways therethrough that are surrounded by an outer wall. The tubular member

182

incorporates the inlet/outlet port

178

therein as illustrated in

FIG. 3

which provides access to the internal cavity

180

inside the housing

172

.

The tubular member

182

positioned within the top panel member

176

of the housing

172

has an outer section

184

which is located outside of the housing

172

and an inner section

186

that is located within the ink composition

32

in the internal cavity

180

(

FIG. 3.

) The outer section

184

of the tubular member

182

is operatively attached by adhesive materials (e.g. conventional cyanoacrylate or epoxy compounds), frictional engagement, and the like to a tubular ink transfer conduit

190

positioned within the port

178

shown schematically in FIG.

3

. In the embodiment of

FIG. 3

, the ink transfer conduit

190

includes a first end

192

which is attached using the methods listed above to and within the port

178

in the outer section

184

of the tubular member

182

. The ink transfer conduit

190

further includes a second end

194

that is operatively and remotely attached to a printhead

196

which may involve a number of different designs, configurations, and systems including those associated with printhead

80

illustrated in FIG.

1

. All of these components are appropriately mounted within a selected printer unit at predesignated locations therein, depending on the type, size, and overall configuration of the entire ink delivery system. It should also be noted that the ink transfer conduit

190

may include at least one optional in-line pump of conventional design (not shown) for facilitating the transfer of ink.

The systems and components presented in

FIGS. 2-3

are illustrative in nature. They may, in fact, include additional operating components depending on the particular systems under consideration. The information provided above shall not limit or restrict the present invention and its various embodiments. Instead, the embodiment of

FIGS. 2-3

may be varied as needed and is presented entirely to demonstrate the applicability of the claimed invention to ink delivery systems which employ a remotely located ink containment vessel.

Many different ink formulations may be employed without limitation as the ink composition

32

in the claimed ink delivery systems. Likewise, the term “ink” as used herein shall encompass dye-based materials, pigment dispersions, and liquid-toner products. However, the present invention is especially suitable for use with ink materials that contain volatile components (e.g. organic solvents and water) and compounds that are “corrosive” when placed in contact with traditional plastics. Representative corrosive materials include acidic dyes, organic solvents, and the like. The term “corrosive” shall again involve the ability of a particular chemical to dissolve or otherwise deteriorate a given material. Some representative and non-limiting ink formulations will now be discussed in detail which may be employed in connection with the ink composition

32

.

The ink products of interest will first contain at least one coloring agent. The coloring agents may include one or more colored dyes or achromatic (black or white) dyes. For example, representative black dyes that are suitable for use in the ink compositions are listed in U.S. Pat. No. 4,963,189 to Hindagolla which is incorporated herein by reference. Colored dyes which may be employed are described in the

Color Index,

Vol. 4, 3rd ed., published by The Society of Dyers and Colourists, Yorkshire, England (1971) which is incorporated herein by reference and is a standard text that is well known in the art. Exemplary dye materials listed in the

Color Index,

supra, that are suitable for use herein include but are not limited to the following compositions: C.I. Direct Yellow 11, C.I. Direct Yellow 86, C.I. Direct Yellow 132, C.I. Direct Yellow 142, C.I. Direct Red 9, C.I. Direct Red 24, C.I. Direct Red 227, C.I. Direct Red 239, C.I. Direct Blue 9, C.I. Direct Blue 86, C.I. Direct Blue 189, C.I. Direct Blue 199, C.I. Direct Black 19, C.I. Direct Black 22, C.I. Direct Black 51, C.I. Direct Black 163, C.I. Direct Black 169, C.I. Acid Yellow 3, C.I. Acid Yellow 17, C.I. Acid Yellow 23, C.I. Acid Yellow 73, C.I. Acid Red 18, C.I. Acid Red 33, C.I. Acid Red 52, C.I. Acid Red 289, C.I. Acid Blue 9, C.I. Acid Blue 61: 1, C.I. Acid Blue 72, C.I. Acid Black 1, C.I. Acid Black 2, C.I. Acid Black 194, C.I. Reactive Yellow 58, C.I. Reactive Yellow 162, C.I. Reactive Yellow 163, C.I. Reactive Red 21, C.I. Reactive Red 159, C.I. Reactive Red 180, C.I. Reactive Blue 79, C.I. Reactive Blue 216, C.I. Reactive Blue 227, C.I. Reactive Black 5, C.I. Reactive Black 31, C.I. Basic Yellow 13, C.I. Basic Yellow 60, C.I. Basic Yellow 82, C.I. Basic Blue 124, C.I. Basic Blue 140, C.I. Basic Blue 154, C.I. Basic Red 14, C.I. Basic Red 46, C.I. Basic Red 51, C.I. Basic Black 11, and mixtures thereof. These materials are known in the art and commercially available from a variety of sources including but not limited to the Sandoz Corporation of East Hanover, N.J. (USA), Ciba-Geigy of Ardsley, N.Y. (USA), and others.

The term “coloring agent” shall likewise encompass conventional pigment dispersions which basically involve a water-insoluble colorant (e.g. a pigment) which is rendered soluble through association with a dispersant (e.g. an acrylic dispersant). Specific pigments which may be employed to produce pigment dispersion materials are known in the art, and the present invention shall not be limited to any particular chemical compositions in this regard. Examples of such pigments include the following compounds which are listed in the

Color Index,

supra: C.I. Pigment Black 7, C.I. Pigment Blue 15, and C.I. Pigment Red 2. Dispersant materials suitable for combination with these and other pigments include monomers and polymers known in the art for this purpose. An exemplary commercial dispersant involves a product sold by W. R. Grace and Co. of Lexington, Mass. (USA) under the trademark DAXAD. In a preferred embodiment, the ink compositions of interest will contain about 2-7% by weight total coloring agent therein (e.g. whether a single coloring agent or combined coloring agents are used). However, the amount of coloring agent to be employed may be varied as needed, depending on the ultimate purpose for which the ink composition is intended and the other ingredients in the ink.

The ink composition will also include an ink “vehicle” which essentially functions as a carrier medium and main solvent for the other components in the composition. Many different materials may be used as the ink vehicle, with the present invention not being limited to any particular products for this purpose. A preferred ink vehicle will consist of water combined with other ingredients including organic solvents. These organic solvents include but are not limited to 2-pyrrolidone; ethoxylated glycerol; 1,5-pentanediol; N-methyl pyrrolidone; 2-propanol; 2-ethyl-2-hydroxymethyl-1,3-propanediol; and cyclohexanol. Such materials are volatile in character and can be lost by evaporation. If this situation occurs, the ink compositions may experience changes in viscosity, homogeneity, and color character which will typically cause a substantial deterioration in print quality. All of these materials may be used in various combinations as determined by preliminary pilot studies on the ink formulations of concern. However, in a preferred embodiment, the ink compositions will contain about 70-80% by weight total combined ink vehicle, wherein at least about 30% by weight of the total ink vehicle will typically consist of water (with the balance comprising any one of the above-listed organic solvents alone or combined). An exemplary ink vehicle will contain about 60-80% by weight water and about 10-30% by weight of one or more organic solvents.

The ink materials may also include a number of optional ingredients in varying amounts. For example, an optional biocide may be added to prevent any microbial growth in the final ink product. Exemplary biocides suitable for this purpose include proprietary products sold under the trademarks PROXEL GXL by Imperial Chemical Industries of Manchester, England; UCARCID by Union Carbide of Danbury, Conn. (USA); and NUOSEPT by Huls America, Inc. of Piscataway, N.J. (USA). In a preferred embodiment, if a biocide is used, the final ink composition will typically include about 0.05-0.5% by weight biocide, with about 0.30% by weight being preferred.

Another optional ingredient to be used in the ink compositions will involve one or more buffering agents. The use of a selected buffering agent or multiple (combined) buffering agents is designed to stabilize the pH of the ink compositions. In a preferred embodiment, the desired pH of the ink compositions will range from about 4-9. Exemplary buffering agents suitable for this purpose will comprise sodium borate, boric acid, and phosphate buffering materials known in the art for pH control. The selection of any particular buffering agents and the amount of buffering agents to be used (as well as the decision to use buffering agents in general) will be determined in accordance with preliminary pilot studies on the particular ink compositions of concern. Additional ingredients (e.g. surfactants) may also be present in the ink formulations if needed.

The novel ink containment vessels described herein can be used with the ink formulations listed above and other ink products without limitation. Specifically, many other ink compositions may be employed including those recited in U.S. Pat. No. 5,185,034 which is incorporated herein by reference.

B. The Ink Containment Vessels

The ink containment vessels of the present invention (including those listed above and illustrated in

FIGS. 1-3

) are constructed of special materials which effectively prevent air and volatile components from passing therethrough. These particular materials will now be described in detail and are applicable to many different ink containment structures including the housing

12

in FIG.

1

and the housing

172

in

FIGS. 2-3

. As shown in

FIG. 1

, reference number

200

is used to designate the overall side wall structure which defines the entire housing

12

, with side wall

200

being produced from the claimed barrier compositions. Likewise, as illustrated in

FIG. 2

, reference number

202

is used to designate the overall side wall structure which defines the entire housing

172

, with side wall

202

being produced from the claimed materials.

The side walls of the novel ink containment vessels are produced from one of three formulations which will now be discussed. The selection of any given formulation will be undertaken in accordance with preliminary pilot testing involving numerous factors including the chemical content of the ink composition being used, the overall configuration of the ink delivery system, and other related considerations. All of the materials described below have a number of common attributes, namely, their ability to produce an ink containment vessel which is resistant to the corrosive effects of ink materials, is substantially fluid/gas impermeable, is dimensionally stable, and provides all of the other benefits listed above. The claimed materials are therefore related in view of their functional attributes and other important features. For this reason, they all constitute “barrier compositions” in accordance with their ability to store ink materials within the claimed vessels in a highly efficient and ink-resistant manner.

1. Formulation No. 1

In a first embodiment, the side walls of the claimed ink containment vessels (including but not limited to those listed above) are constructed from a material designated herein as “polyethylene naphthalate” (e.g. “PEN”) which is also known as a homopolymer of dimethyl 2,6-naphthalenedicarboxylate and ethylene glycol. It specifically has the following chemical structure (with either alternative being applicable):

Number	Name	Date
4329698	Smith	May 1982
4415886	Kyogoku et al.	Nov 1983
4500895	Buck et al.	Feb 1985
4509062	Low et al.	Apr 1985
4749291	Kobayashi et al.	Jun 1988
4771295	Baker et al.	Sep 1988
4794409	Cowger et al.	Dec 1988
4929969	Morris	May 1990
4963189	Hindagolla	Oct 1990
5147682	Takiguchi et al.	Sep 1992
5168285	Winslow	Dec 1992
5185034	Webb et al.	Feb 1993
5185614	Courian et al.	Feb 1993
5278584	Keefe et al.	Jan 1994
5359353	Hunt et al.	Oct 1994
5719609	Hauck et al.	Feb 1998
5737001	Taylor	Apr 1998
5759653	Collette et al.	Jun 1998
5780130	Hansen et al.	Jul 1998
5939153	Valyi	Aug 1999
6083639	McHugh et al.	Jul 2000

Number	Date	Country
0864437	Sep 1998	EP
09084248	Oct 1998	JP
WO9831547	Jul 1998	WO

High-durability ink containment unit for use in an ink delivery system

Information

Patent Number

Date Filed

Date Issued

Inventors

Original Assignees

Examiners

CPC

US Classifications

Field of Search

US

International Classifications

Abstract

Description

Claims

US Referenced Citations (21)

Foreign Referenced Citations (3)

Non-Patent Literature Citations (7)