United States Patent [19]
`Shields et a1.
`
`llllllllllllllllllllillllllllllllllllllllllllllllllllllllllilllllllllllllll
`USOO5428383A
`[11] Patent Number:
`5,428,383
`[45] Date of Patent: * Jun. 27, 1995
`
`METHOD AND APPARATUS FOR
`PREVENTING COLOR BLEED IN A
`MULTI-INK PRINTING SYSTEM
`
`Notice:
`
`Inventors: James P. Shields; Garold E. Radke,
`both of Corvallis, Oreg.
`Assignee: Hewlett-Packard Corporation, Palo
`Alto, Calif.
`The portion of the term of this patent
`subsequent to Mar. 30, 2010 has been
`disclaimed.
`Appl. No.: 926,259
`Filed:
`Aug. 5, 1992
`
`Int. Cl.6 ............................................ .. C09D 11/02
`US. Cl. ................................. .. 347/96; 106/20 D;
`106/20 R
`Field of Search ............ .. 106/20 R, 20 D; 347/96
`
`References Cited
`U.S. PATENT DOCUMENTS
`
`[75]
`
`[73]
`
`[21]
`[22]
`[5 1]
`[52]
`
`[58]
`[56]
`
`4,500,895 2/ 1985 Buck et a1. ............................ .. 347/9
`4,740,420 4/ 1988 Akutsu et al. .
`.... .. 428/341
`4,771,295 9/1988 Baker et a1. ................... .. 347/9
`4,794,409 12/1988 Cowger et a1.
`.... .. 222/187
`4,818,285 4/1989 Causley et a1.
`106/20 D
`
`4,963,189 10/1990 Hindagolla . . . . . . . .
`
`. . . . . . .. 106/22
`
`5,025,271 6/1991 Baker et al. ....................... .. 347/9
`5,108,504 4/1992 Johnson et a1.
`.............. .. 106/25
`5,196,056 3/1993 Prasad ..... ..
`5,198,023 3/1993 Stoffel ............................. .. 160/22 R
`
`OTHER PUBLICATIONS
`Hewlett-Packard Journal, vol. 39, No. 4 (Aug. 1988): pp.
`l-89.
`Color Index, vol 4, 3rd Ed., The Society of Dyers and
`Colourists, Yorkshire, England (1971), pp. 4018, 4035,
`4059, 4132, 4193, 4194, 4340, 4385, 4406-4410, 4419,
`4618, and 4661.
`Primary Examiner-Benjamin R. Fuller
`Assistant Examiner-Valerie Ann Lund
`[57]
`ABSTRACT
`A method for controlling color bleed in multi-color
`thermal inkjet printing systems. Color bleed involves
`the migration of coloring agents between adjacent
`zones in a multi-color printed image on a substrate. To
`control color bleed between any two ink compositions
`in a multi-ink system, at least one of the ink composi
`tions will contain a precipitating agent (e.g. a multi
`valent metal salt). The precipitating agent is designed to
`react with the coloring agent in the other ink composi
`tion of concern. As a result, when the two ink composi
`tions come in contact, a precipitate is formed from the
`coloring agent in the other ink composition which pre
`vents migration thereof and color bleed problems. This
`technique is applicable to printing systems containing
`two or more ink compositions, and enables distinct
`multi-color images to be produced without the prob
`lems normally caused by color bleed.
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`14 Claims, 3 Drawing Sheets
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`METHOD AND APPARATUS FOR PREVENTING
`COLOR BLEED IN A MULTI-INK PRINTING
`SYSTEM
`
`BACKGROUND OF THE INVENTION
`The present invention generally relates to thermal
`inkjet printing technology, and more particularly to a
`multi-color thermal inkjet printing system in which
`color bleed problems between adjacent printed regions
`are controlled.
`Substantial developments have been made in the ?eld
`of electronic printing technology. Speci?cally, a wide
`variety of highly ef?cient 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. Thermal inkjet systems basi
`cally involve a cartridge which includes at least one ink
`reservoir/compartment in ?uid communication with a
`substrate having a plurality of resistors thereon. Selec
`tive activation of the resistors causes thermal excitation
`of the ink and expulsion thereof from the ink cartridge.
`Representative thermal inkjet systems are discussed in
`US. Pat. No. 4,500,895 to Buck et al.; No. 4,794,409 to
`Cowger et al.; and the Hewlett-Packard Journal, Vol. 39,
`No. 4 (August 1988), all of which are incorporated
`herein by reference.
`Recently, additional developments have been made
`in the ?eld of thermal inkjet technology involving the
`generation of multi-colored images. This is typically
`accomplished through the use of specially-designed
`thermal inkjet cartridges having a plurality of individ
`ual ink compartments therein. Each of the compart
`ments is designed to retain a selected ink having speci?c
`physical/color characteristics. By combining these ink
`materials on a substrate (e. g. paper) in varying con?gu
`rations and quantities, multi-colored images having a
`high degree of print resolution and clarity may be pro
`duced. Exemplary thermal inkjet cartridges having
`multiple ink-containing compartments are illustrated
`and described in US. Pat. No. 4,771,295 to Baker et. a1.
`and US. Pat. No. 5,025,271 to Baker et. al. which are
`both incorporated herein by reference.
`However, under certain circumstances, a signi?cant
`problem can occur when multi-color images are printed
`using thermal inkjet technology as described above.
`Speci?cally, this problem involves a situation known as,
`“color bleed ”. In general and for the purposes set forth
`herein, color bleed is a term used to describe the diffu
`sion/mixture of at least two different colored ink re
`gions into each other. Such diffusion/ mixture normally
`occurs when the different colored regions are printed
`next to and in contact with each other (e.g. at their
`marginal edges). For example, if a region consisting of a
`?rst coloring agent (e.g. black) is printed directly adja
`cent to and against another region consisting of a sec
`ond coloring agent (e. g. yellow), the ?rst coloring agent
`will often diffuse or “bleed ” into the second coloring
`agent, with the second coloring agent possibly bleeding
`into the ?rst coloring agent. Accordingly, indistinct
`images with a poor degree of resolution are produced.
`An insuf?cient degree of resolution results from the
`production of jagged, nonlinear lines of demarcation
`between adjacent colored regions instead of sharp bor
`ders therebetween. This can create signi?cant prob
`lems, especially when high volume printing systems are
`used to print complex, multi-color images.
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`In addition, color bleed problems in multi-ink systems
`are also caused by strong capillary forces generated in
`many commonly-used paper substrates. These capillary
`forces cause a “wicking ” effect in which coloring
`agents are drawn into each other by capillary action
`through the ?bers of the paper materials. This situation
`also results in a ?nal printed image of poor quality and
`de?nition.
`The present invention represents a unique and highly
`effective approach in the control of color bleed in multi
`color thermal inkjet printing systems. The methods
`described herein may be implemented at a minimal cost,
`and do not require the use of extra equipment, custom
`manufactured paper, and/or special paper coatings. The
`present invention therefore represents an advance in the
`art of thermal inkjet printing technology as described in
`greater detail below.
`
`SUMMARY OF THE INVENTION
`It is an object of the present invention to provide an
`improved multi~color thermal inkjet printing system.
`It is another object of the invention to provide an
`improved multi-color thermal inkjet printing system
`which uses a plurality of colored ink materials to pro
`duce multi-color images.
`It is another object of the invention to provide an
`improved multi-color thermal inkjet printing system
`which avoids problems associated with color bleed
`between adjacent printed regions.
`It is a further object of the invention to provide an
`improved multi-color thermal inkjet printing system
`which avoids problems associated with color bleed
`through the use of specially formulated ink materials in
`which the coloring agents therein do not migrate into
`each other after printing.
`It is a still further object of the invention to provide
`an improved multi-color thermal inkjet printing system
`which avoids problems associated with color bleed
`through the use of specially-formulated ink materials
`which are manufactured and used in an economical and
`highly effective manner.
`It is an even further object of the invention to provide
`an improved multi-color thermal inkjet printing system
`which effectively avoids problems associated with
`color bleed without the use of extra equipment, custom
`manufactured paper, and/or special paper coatings.
`In accordance with the foregoing objects, the present
`invention involves a highly ef?cient thermal inkjet
`printing system which is capable of generating multi
`color images on a substrate (e.g. paper) without color
`bleed between adjacent color regions. As indicated
`above, color bleed involves a situation in which the
`migration of coloring agents occurs between adjacent
`printed regions on a substrate. Color bleed substantially
`decreases print quality and resolution, and prevents
`distinct boundaries from being produced between adja
`cent color regions.
`The invention as described herein is especially suit
`able for use in thermal inkjet and other printing systems
`which include multiple cartridges, with each cartridge
`having one or more different color ink materials therein.
`In addition, the invention is also suitable for use in con
`nection with specially designed ink cartridges (de
`scribed below) which each include a plurality of com
`partments that are designed to retain a different color
`ink therein. In many instances, each individual cartridge
`will contain separate supplies of cyan, yellow, and/or
`magenta ink, and may further include a separate supply
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`3
`of black ink. These inks are then applied in various
`patterns on a substrate (e.g. paper) using conventional
`techniques in order to produce a wide variety of multi
`color images. However, regardless of which application
`method is used, color bleed can occur between adjacent
`printed regions if the coloring agents (e. g. dyes and/or
`pigment materials) from each ink region have physical
`characteristics which cause migration of the coloring
`agents into each other. This problem is especially acute
`when a region of black ink is printed adjacent to and in
`contact with a region of cyan, magenta, yellow or other
`color ink. Color bleed problems involving black ink
`cause a signi?cant and extensive reduction in print qual
`ity.
`As indicated above, the present invention involves a
`method for preventing color bleed between at least two
`different color ink compositions. To accomplish this,
`the speci?c ink compositions which are prone to color
`bleed are formulated in a unique and special manner. In
`general, the ?rst ink composition of concern will in
`clude about 2—7% by weight coloring agent and about
`1-70% by weight solvent. In a preferred embodiment,
`the coloring agent of the ?rst ink composition will in
`clude one or more carboxyl and/ or carboxylate groups
`as described in greater detail below. The second ink
`composition of concern (from a color bleed standpoint)
`will include a precipitating agent therein which is de
`signed to react with the coloring agent in the ?rst ink
`composition in order to prevent color bleed between
`the two ink compositions. Speci?cally, the precipitating
`agent from the second ink composition and the coloring
`agent from the ?rst ink composition react to form a
`solid precipitate. Precipitate formation is facilitated by
`interaction between the precipitating agent and the
`carboxyl/carboxylate groups associated with the color
`ing agent of the ?rst ink composition. Precipitate forma
`tion prevents migration of the coloring agent from the
`?rst ink composition into the second ink composition
`when both compositions are printed adjacent to and in
`contact with each other. In a preferred embodiment, the
`precipitating agent consists of a multi-valent metal salt.
`Exemplary metal cations suitable for use in the multi
`valent metal salt include but are not limited to Ca”,
`Cu'l-Z, Co+2, Ni+2, Fe+2 , La+3, Nd+3, y+3, or Al+3.
`Exemplary anions which may be coupled with these
`cations include but are not limited to NO3—, F‘, Cl—,
`Br—, I‘, CH3COO', and 804-2. Preferably, the sec
`ond ink composition will include about l-l5% by
`weight multi-valent metal salt.
`The second ink composition containing the multi
`valent metal salt will further include a selected coloring
`agent as described in greater detail below which will
`not physically or chemically react with the precipitat
`ing agent. Speci?cally, the second ink composition will
`include about 2-7% by weight coloring agent, in com
`bination with about 1-70% by weight solvent.
`When the ?rst ink composition and second ink com
`position are printed adjacent to and in contact with each
`other on a substrate, the above-described precipitation
`reaction will occur between the multi-valent metal salt
`of the second ink composition and the coloring agent of
`the ?rst ink composition. While the foregoing reaction
`does not signi?cantly affect the desired visual/color
`characteristics of the printed image, it does, in fact,
`eliminate migration of the coloring agent from the ?rst
`ink composition into the second ink composition. In
`addition, while this procedure is primarily described
`herein with respect to a dual ink system using a single
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`precipitating agent for the sake of clarity, the concepts
`inherent in this invention are equally applicable to ther
`mal inkjet printing systems/cartridges which involve
`more than two colored ink compositions. Regardless of
`the type and complexity of the thermal inkjet printing
`system being used, the present invention effectively
`prevents color bleed between adjacent multi-color ink
`regions in a highly ef?cient manner. As described in
`greater detail below, this enables the production of
`clear, high-de?nition printed color images.
`These and other objects, features, and advantages of
`the invention shall be described below in the following
`Detailed Description of Preferred Embodiments and
`Brief Description of the Drawings.
`
`10
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`BRIEF DESCRIPTION OF THE DRAWINGS
`FIG. 1 is an exploded perspective view of an exem
`plary thermal inkjet cartridge having multiple ink com
`partments therein which may be used to produce multi
`color images without color bleed therebetween in ac
`cordance with the present invention.
`FIG. 2 is an exploded perspective view of an alterna
`tive thermal inkjet cartridge which may be used in
`accordance with the present invention.
`FIG. 3 is a schematic illustration of the thermal inkjet
`cartridge of FIG. 1 wherein such cartridge is dispensing
`the ink compositions of the present invention in separate
`regions on a substrate.
`FIG. 4 is a schematic illustration of a printing system
`using multiple thermal inkjet cartridges of the types
`shown in FIGS. 1 and FIG. 2 in order to dispense the
`ink compositions of the present invention in separate
`regions on a substrate.
`
`DETAILED DESCRIPTION OF PREFERRED
`EMBODIMENTS
`In accordance with the present invention, a unique
`and highly effective method for controlling color bleed
`between adjacent multi-color ink regions on a substrate
`is described herein. Conventional ink compositions used
`in thermal inkjet printing systems normally include a
`wide variety of chemical components. For example,
`typical ink compositions suitable for use in thermal
`inkjet printing systems are described in US. Pat. No.
`4,963,189 to Hindagolla which is incorporated herein by
`reference. The primary components in such ink compo
`sitions include: (1) a coloring agent (e.g. a dye or pig
`ment material) and (2) a solvent. Exemplary solvents,
`coloring agents, and other important ink components
`will be described in greater detail below.
`However, when two different color ink compositions
`are applied to a substrate (e. g. paper) in regions which
`are adjacent to and in contact with each other (e.g. at
`their marginal edges), the coloring agents from each
`composition can bleed or migrate into each other. As a
`result, indistinct color images are produced which are
`characterized by non-linear and incomplete lines of
`demarcation between adjacent colored zones. When
`complex and intricate printed images are being applied
`to a substrate, the foregoing problems will result in a
`printed product having a low degree of print quality.
`Color bleed (e. g. coloring agent migration) typically
`occurs between two ink compositions when the color
`ing agent from the ?rst ink composition has properties
`which cause migration thereof into the second ink com
`position and vice versa. This phenomenon results in
`coloring agent movement between adjacent printed
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`regions when both regions come in contact with each
`other.
`Coloring agent migration is a particularly dif?cult
`problem when aqueous inks are used, since a signi?cant
`amount of time is necessary for all of the volatile ink
`components therein to evaporate. During this delay,
`coloring agent migration can occur as described above.
`Likewise, the migration of coloring agents may be en
`hanced through capillary forces exerted on the ink com~
`positions by ?bers which are present in ?brous organic
`substrates (e.g. paper). Finally, it should be noted that
`the problem of color bleed is especially signi?cant
`(from a visual/print quality perspective) when a region
`of black ink is applied adjacent to and in contact with a
`region of another ink color. In this situation, the black
`ink will typically migrate into the adj acent color region,
`thereby causing substantial image quality problems.
`The present invention as described below involves a
`method in which at least two ink compositions which
`are especially prone to color bleed problems may be
`chemically formulated to prevent such problems from
`occurring. The method set forth herein effectively con
`trols color bleed with respect to the ink compositions
`under consideration, and substantially eliminates print
`quality problems associated therewith.
`In order to facilitate a full and complete understand
`ing of the present invention, a discussion will ?rst be
`provided involving exemplary thermal inkjet cartridges
`and printing systems which may be used to deliver the
`ink formulations of the present invention to a substrate.
`FIG. 1 schematically illustrates an exemplary thermal
`inkjet cartridge which is suitable for use in accordance
`with the present invention. It should be noted and em
`phasized that the method of the present invention and
`the formulations described herein shall not be limited to
`use in the speci?c thermal inkjet cartridge of FIG. 1.
`Other thermal inkjet cartridges known in the art which
`are suitable for the purposes described herein may also
`be used as indicated below.
`With reference to FIG. 1, an exemplary thermal ink
`jet cartridge 10 designed to produce multi-color printed
`images is schematically illustrated. Cartridge 10 is of the
`type illustrated and disclosed in U.S. Pat. Nos. 4,771,295
`and 5,025,271 both to Baker et. al. which are incorpo
`rated herein by reference. As shown in FIG. 1, the
`cartridge 10 includes a housing 12 having ?rst, second,
`and third chambers or compartments 14, 16, 18 therein.
`Compartments 14, 16 are separated by a solid, continu
`ous wall 20 (shown in dashed lines in FIG. 1), while
`compartments 16, 18 are separated by a solid, continu
`50
`ous wall 24 (also shown in dashed lines in FIG. 1). The
`housing 12 further includes an externally-positioned
`support structure 26 which is constructed of a plurality
`of side walls 28, 30, 32, 34 with a substantially rectangu
`lar center zone 40 therebetween. Positioned within the
`center zone 40 and passing entirely through the housing
`12 are a plurality of ink outlet ports 42, 44, 46 which
`respectively communicate with the compartments 14,
`16, 18.
`With continued reference to FIG. 1, the center zone
`40 of the support structure 26 is sized to receive a thin
`?lm resistor-type printhead unit 47 which is well known
`in the art. The printhead unit 47 includes a substrate 48
`having a plurality of resistors 49 thereon which ' are
`schematically illustrated and enlarged for the sake of
`65
`clarity in FIG. 1. Likewise, the substrate 48 further
`includes a plurality of ori?ces 50, 51, 52 which pass
`entirely through the substrate 48 and communicate
`
`6
`respectively with the ink outlet ports 42, 44, 46 in the
`assembled cartridge 10. In addition, secured to the sub
`strate 48 is an ori?ce plate 54. The ori?ce plate 54 is
`preferably made of an inert metal composition (e. g.
`gold-plated nickel), and further includes a plurality of
`ink ejection ori?ces 55, 56, 57 which pass entirely there
`through. The ink ejection ori?ces 55, 56, 57 are ar
`ranged on the ori?ce plate 54 so that they respectively
`register with the ori?ces 50, 51, 52 in the substrate 48.
`This con?guration ultimately enables ink to be with
`drawn from the compartments 14, 16, 18 and thereafter
`expelled from the ink ejection ori?ces 55, 56, 57.
`As shown in FIG. 1, three ink ?lters 60, 62, 64 are
`provided which are each mounted respectively within
`the compartments 14, 16, 18 as illustrated. Speci?cally,
`the ink ?lter 60 is mounted within compartment 14
`directly adjacent to and against the ink outlet port 42.
`Likewise, the ink ?lter 62 is mounted within compart
`ment 16 directly adjacent to and against the ink outlet
`port 44, while the ink ?lter 64 is mounted within com
`partment 18 directly adjacent to and against the ink
`outlet port 46. The ink ?lters 60, 62, 64 are preferably
`manufactured from stainless steel wire mesh having a
`porosity suf?cient to provide substantial ?ltration of air
`bubbles and solid particulates when ink passes from the
`compartments 14, 16, 18 into and through the ink outlet
`ports 42, 44, 46.
`Also provided as illustrated in FIG. 1 are three foam
`portions 70, 72, 74. The foam portions 70, 72, 74 are
`each designed for placement within compartments 14,
`16, 18, respectively. Likewise, the foam portions 70, 72,
`74 are preferably sizedto be slightly larger than the
`compartments designed to receive them so that when
`the foam portions 70, 72, 74 are placed therein, they will
`expand outwardly within the compartments. The foam
`material used to produce the foam portions 70, 72, 74
`preferably consists of an ether-type foam well known in
`the art which is commercially available from the Scott
`Paper Company of Philadelphia, Penn.
`Fitted onto the ends 76, 78, 80 of the foam portions
`70, 72, 74 and secured to the rear 82 of the housing 12 is
`a cap member 84 which prevents back pressure build-up
`and facilitates the ultimate delivery of ink from the foam
`portions 70, 72, 74 to the printhead unit 47. Air vents 86,
`88, 90 are provided which are each covered with po
`rous plastic membranes (not shown). The membranes
`allow air to pass therethrough while preventing ink
`from leaking outwardly through the air vents 86, 88, 90.
`Finally, the cap member 84 further includes compres
`sion tabs 93 which are designed to facilitate proper
`placement/orientation of the foam portions 70, 72, 74
`within their respective compartments. Further struc
`tural and operational information regarding cartridge
`10 is provided in U.S. Pat. Nos. 4,771,295 and 5,025,271
`both to Baker et. al., as well as in the Hewlett-Packard
`Journal, Vol. 39, No. 4 (August 1988).
`FIG. 2 schematically illustrates a simpli?ed version
`of cartridge 10 which is also suitable for use in accor
`dance with the present invention. With reference to
`FIG. 2, a single-chamber cartridge 100 is illustrated
`which includes a housing 112 having a single chamber
`or compartment 114 therein. The housing 112 further
`includes an externally-positioned support structure 126
`which is constructed of a plurality of side walls 128,130,
`132,134 with a substantially rectangular center zone 140
`therebetween. Positioned within the center zone 140
`and passing entirely through the housing 112 is an elon
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`gate ink outlet port 142 which communicates with the
`compartment 114 as illustrated.
`With continued reference to FIG. 2, the center zone
`140 of the support structure 126 is sized to receive a
`thin~?lm resistor-type printhead unit 147 which is well
`known in the art. The printhead unit 147 includes a
`substrate 148 having a plurality of resistors 149 thereon
`which are schematically illustrated and enlarged for the
`sake of clarity in FIG. 2. Likewise, the substrate 148
`further includes an elongate ori?ce 150 which passes
`entirely through the substrate 148 and communicates
`directly with the ink outlet port 142 in the assembled
`cartridge 100. In addition, secured to the substrate 148 is
`an ori?ce plate 154. The ori?ce plate 154 is preferably
`manufactured of an inert metal composition (e.g. gold
`plated nickel), and further includes an ink ejection ori
`?ce 155. The ink ejection ori?ce 155 registers with the
`ori?ce 150 in the substrate 148. This con?guration ulti
`mately enables ink to be withdrawn from the compart
`ment 114 and thereafter expelled from the ink ejection
`ori?ce 155.
`As shown in FIG. 1, an ink ?lter 160 is provided
`which is mounted within the compartment 114 as illus
`trated. Speci?cally, the ink ?lter 160 is mounted within
`compartment 114 directly adjacent to and against the
`ink outlet port 142. The ink ?lter 160 is preferably man
`ufactured from stainless steel wire mesh having a poros
`ity suf?cient to provide substantial ?ltration of air bub
`bles and solid particulates when ink passes from the
`compartment 114 into and through the ink outlet port
`142.
`Also provided as illustrated in FIG. 2 is a single foam
`portion 170. The foam portion 170 is preferably sized to
`be slightly larger than the compartment 114 designed to
`receive it so that when the foam portion 170 is placed
`therein, it will expand outwardly within the compart
`ment 114. The foam material used to produce the foam
`portion 170 preferably consists of an ether-type foam
`well known in the art which is commercially available
`from the Scott Paper Company of Philadelphia, Penn.
`Fitted onto the end 176 of the foam portion 170 and
`secured to the rear 182 of the housing 112 is a cap mem
`ber 184 which prevents back pressure build-up and
`facilitates the ultimate delivery of ink from the foam
`45
`portion 170 to the printhead unit 147. Air vent 186 is
`provided which is covered with a porous plastic mem
`brane (not shown). The membrane allows air to pass
`therethrough while preventing ink from leaking out
`wardly through the air vent 186. Finally, cap member
`184 may further include one or more compression tabs
`193 which are designed to facilitate proper placement
`/orientation of the foam portion 170 within compart
`ment 114. Further structural and operational informa
`tion regarding cartridge 100 is generally provided in the
`Hewlett-Packard Journal, Vol. 39, No. 4 (August 1988)
`and in US Pat. No. 4,794,409 to Cowger et al.
`Basically, cartridge 10, cartridge 100, and other ther
`mal inkjet cartridges known in the art which are suit
`able for the purposes set forth herein deliver ink
`through the selective activation (heating) of the thin
`?lm resistors associated with the printhead substrate.
`Selective heating of the resistors causes ink coming in
`contact therewith to be forcefully expelled from the
`ori?ce plate of the selected cartridge. Heating of the
`resistors is accomplished using pulse drive circuitry (not
`shown) which is either integrated onto the printhead or
`externally positioned within the main printer unit. By
`
`8
`activating the cartridge in this manner, ink can be ex
`pelled therefrom to produce a ?nished printed image.
`Multi-compartment ink cartridges of the type illus
`trated in FIG. 1 and described herein are designed to
`retain supplies of various colored ink compositions
`therein. For the purposes of this invention, the term
`“colored ink compositions ” shall also encompass black
`ink. Speci?cally, the multi-compartment cartridge 10 of
`FIG. 1 may be con?gured to retain any number of col
`ored ink compositions including but not limited to cyan,
`magenta, yellow, and/ or black ink. The black ink may
`be contained within one of the foam portions 70, 72, 74
`held within compartments 14, 16, 18. In the alternative,
`the black ink may be retained within a separate car
`tridge (e. g. within the foam portion 170 in the compart
`ment 114 of cartridge 100 as shown in FIG. 2). The
`cartridge 100 would then operate in the same printer
`unit along with cartridge 10. Having a separate car
`tridge for black ink is often desirable since black ink is
`typically consumed at a greater rate compared with
`other color inks in a multi-ink system. As a result, once
`the black ink is consumed, the black ink cartridge may
`be discarded without disposal of the other ink cartridge
`and any ink left therein.
`As previously indicated, color bleed problems may
`occur when at least one of the foregoing ink composi
`tions is printed in a region directly adjacent to and in
`contact with (e.g. at the marginal edges of) a region
`consisting of another colored ink composition. This
`problem is especially acute when a region of black ink is
`printed adjacent to and in contact with a region of a
`different colored ink (e.g. cyan, magenta, and/or yel
`low). The present invention involves a method for for
`mulating the foregoing ink compositions so that color
`bleed therebetween is minimized and/ or eliminated.
`Since color bleed normally occurs between two differ
`ent ink compositions printed adjacent to and in contact
`with each other, the present invention will be described
`herein for the sake of clarity with respect to a dual ink
`system wherein both ink compositions are specially
`formulated to avoid color bleed therebetween. How
`ever, it should be noted that the basic conceptual meth
`ods described below with respect to a dual ink system
`are also applicable to a system involving more than two
`colored ink compositions. An individual skilled in the
`art may readily accomplish this by merely applying the
`broad concepts set forth herein to other ink composi
`tions which may be prone to color bleed problems.
`Accordingly, the present invention shall not be limited
`to use exclusively in dual ink systems, and shall also not
`be limited to the speci?c ink compositions set forth
`herein.
`In order to prevent color bleed between any two ink
`compositions in accordance with the present invention,
`both of the ink compositions must be specially formu
`lated. In an exemplary situation involving the control of
`color bleed between two ink compositions (hereinafter
`“Ink Composition 1” and “Ink Composition 2”), the
`preferred formulations thereof are as follows:
`Ink Composition 1
`The ?rst component of ink composition 1 consists of
`a ?rst coloring agent preferably in the form of an or
`ganic dye having at least one and preferably two or
`more carboxyl and/or carboxylate groups. Exemplary
`carboxylated dye materials suitable for use in the pres
`ent invention are listed in US Pat. No. 4,963,189 to
`Hindagolla which is incorporated herein by reference.
`
`55
`
`65
`
`Memjet Ex. 2008, Page 8
`
`

`
`W
`
`X
`
`N=N
`
`N=N
`
`NI-IR
`
`OH
`
`H035
`
`Y
`
`Z
`
`‘
`
`---COOH
`—H, or —COOH
`
`In this structure, it is preferred that there be at least
`two --COOI-I groups as indicated above, and that the
`number of —COOH groups be equal to or greater than
`the number of —SO3H groups. Speci?c and exemplary
`dye structures are provided in Table I below:
`TABLE I
`Y
`Z
`
`R
`
`5,428,383
`10
`Further information regarding the foregoing composi
`Such materials are black and involve the following
`tions is provided on pages 4059, 4193, 4194, 4340, and
`basic structure:
`4406-4410 of the Color Index, supra, with such pages
`being incorporated herein by reference. In a preferred
`embodiment, ink composition 1 will have a coloring
`agent concentration level broadly ranging from about
`0.5% by weight up to the