WO2008133617A1 - Photoconductor - Google Patents

Photoconductor

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Publication number
WO2008133617A1
WO2008133617A1 PCT/US2007/010254 US2007010254W WO2008133617A1 WO 2008133617 A1 WO2008133617 A1 WO 2008133617A1 US 2007010254 W US2007010254 W US 2007010254W WO 2008133617 A1 WO2008133617 A1 WO 2008133617A1
Authority
WO
Grant status
Application
Patent type
Prior art keywords
charge transport
surface
photoconductor
chemicals
portion
Prior art date
Application number
PCT/US2007/010254
Other languages
French (fr)
Inventor
Bruce Jackson
John Thompson
John Stewart
Original Assignee
Hewlett-Packard Development Company, L.P.
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date

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Classifications

    • GPHYSICS
    • G03PHOTOGRAPHY; CINEMATOGRAPHY; ELECTROGRAPHY; HOLOGRAPHY
    • G03GELECTROGRAPHY; ELECTROPHOTOGRAPHY; MAGNETOGRAPHY
    • G03G5/00Recording members for original recording by exposure, e.g. to light, to heat, to electrons; Manufacture thereof; Selection of materials therefor
    • G03G5/02Charge-receiving layers
    • G03G5/04Photoconductive layers; Charge-generation layers or charge-transporting layers; Additives therefor; Binders therefor
    • G03G5/043Photoconductive layers characterised by having two or more layers or characterised by their composite structure
    • G03G5/047Photoconductive layers characterised by having two or more layers or characterised by their composite structure characterised by the charge-generation layers or charge transport layers
    • GPHYSICS
    • G03PHOTOGRAPHY; CINEMATOGRAPHY; ELECTROGRAPHY; HOLOGRAPHY
    • G03GELECTROGRAPHY; ELECTROPHOTOGRAPHY; MAGNETOGRAPHY
    • G03G5/00Recording members for original recording by exposure, e.g. to light, to heat, to electrons; Manufacture thereof; Selection of materials therefor
    • G03G5/14Inert intermediate or cover layers for charge-receiving layers
    • G03G5/147Cover layers
    • GPHYSICS
    • G03PHOTOGRAPHY; CINEMATOGRAPHY; ELECTROGRAPHY; HOLOGRAPHY
    • G03GELECTROGRAPHY; ELECTROPHOTOGRAPHY; MAGNETOGRAPHY
    • G03G5/00Recording members for original recording by exposure, e.g. to light, to heat, to electrons; Manufacture thereof; Selection of materials therefor
    • G03G5/14Inert intermediate or cover layers for charge-receiving layers
    • G03G5/147Cover layers
    • G03G5/14708Cover layers comprising organic material

Abstract

Various methods and apparatus relating to a photoconductor are disclosed.

Description

PHOTOCONDUCTOR

BACKGROUND

[0001] Photoconductors are sometimes used to form images of printing material which is subsequently transferred to a print medium. During printing, surfaces of the photoconductors may become contaminated, reducing print quality or resulting in costly replacement of the photoconductors.

BRIEF DESCRIPTION OF THE DRAWINGS

[0002] Figure 1 is a sectional view of a photoconductor according to an example embodiment.

[0003] Figure 2 is a side elevation of view schematically illustrating a printer including a photoconductor of Figure 1 according to an example embodiment.

[0004] Figure 3 is a schematic illustration of an immunization system for immunizing a photoconductor according to an example embodiment.

[0005] Figure 4 is a sectional view of one example of a photoconductor prior to immunization by the system of Figure 3 according to an example embodiment.

DETAILED DESCRIPTION OF THE EXAMPLE EMBODIMENTS

[0006] Figure 1 is a sectional view of a photoconductor 20 for an electrophotographic imaging system according to one example embodiment. Photoconductor 20, also sometimes referred to as a photoreceptor, comprises a multi-layered structure configured to be charged and to have portions selectively discharged in response to optical radiation such that charged and discharged areas form a discharged image to which charged printing material is adhered. Photoconductor 20 may be supported by a drum, belt or other movable structure or member. As will be described hereafter, photoconductor 20 may be less susceptible to contamination brought about by chemical reactions at its surface. As a result, photoconductor 20 may have a longer life. [0007] Photoconductor 20 includes support 22, electrically conductive layer 24, barrier layer 26, charge generation layer 28 and charge transport layer 30. Support 22 comprises a carrier or substrate upon which layers 24, 26 and 30 are formed or otherwise provided. In one embodiment, support 22 is formed from one or more dielectric materials. In one embodiment, support 22 is formed from one or more flexible dielectric materials such as one or more polymers. In the example illustrated, support 22 comprises a single layer of polyethylene terephthalate. In other embodiments, support 22 may comprise other flexible or inflexible materials, including, but not limited to aluminum or stainless steel.

[0008] Electrically conductive layer 24 comprises a layer between support 22 and barrier layer 26 that is electrically resistive. Layer 24 is configured to carry electrons discharged from the charge generation layer 28 upon bombardment with light or photons. In one embodiment, the electrically conductive layer 24 comprises a metal film. Examples of metals from which layer 24 may be formed include, but are not limited to, aluminum, stainless steel, copper, nickel, palladium, tin oxide or indium oxide. .

[0009] Barrier layer 26 is an electrically resistive layer extending between conductive layer 24 and charge generation layer 28. Barrier layer 26 is configured to facilitate movement of electrons discharged by charge generation layer 28 to conductive layer 24. Barrier layer 26 may comprise an inorganic layer such as an anodized aluminum film, aluminum oxide or aluminum hydroxide. Barrier layer 26 may alternatively comprise an organic layer such as a layer of polyvinyl alcohol, casein, polyvinyl pyrrolidone, pollyacrylic acid, cellulose, gelatin, starch, polyurethane, polyimide, or polyamide. In the particular example illustrated, barrier layer 26 has a thickness of about 1.2 microns or micrometers (μ). In other embodiments, barrier layer 26 may be formed from one or more other materials and may have other thicknesses. [0010] Charge generation layer 28 comprises a layer of one or more materials configured to emit negative charge or electrons in response to bombardment with light, such as laser light. At the same time, positive charge or "holes" are generated by layer 28. These holes are transported by charge transport layer 30 to surface 34 of photoconductor 20 to neutralize or discharge negative static charge along the surface 34. Examples of materials from which charge generation layer 28 may be formed include, but are not limited to, selenium or it's alloy, arsenic selenium, cadmium sulfide, zinc oxide or other inorganic photoconductor materials. Alternatively, charge generation layer 28 may be formed from various organic photoconductor materials such phthalocyanine, an azo dye, quinacridone, a polycyclic quinine, a pyrylium salt, a thiapyrylium salt, indigo, thioindigo, anthanthrone, pyranthrone or cyanine. Particular examples include metal free phthalocyanine, a phthalocyanine having a metal or its oxide or chloride, such as copper indium chloride, gallium chloride, tin, oxytitanium, zinc or vanadium, coordinated, or an azo pigment such as a monoazo, bisazo, trisazo or polyazo pigment. In the example embodiment illustrated, charge generation layer 28 has a thickness of about 0.1 μ. In other embodiments, charge generation layer 28 may be formed from other materials and may have other thicknesses. [0011] Charge transport layer 30 transfers or carries positive charge or holes from charge generation layer 28 to surface 34, where such positive charge dissipates or discharges negative electrical static charge along corresponding areas are portion of surface 34. Charge transport layer 30 comprises a substantially homogenous layer which includes charge transport chemicals 40 (schematically represented) captured within and dispersed throughout a binder or matrix 42. Charge transport chemicals 40 include hole carriers and charge transport enhancers. Hole carries include, but are not limited to, aromatic amines and aromatic hydrazones. Examples of hole carriers include, but are not limited to, 4-Dibenzylamino-2-methyl benzaldehyde (CAS# 1424- 65-3), 4-(N-ethyl-N-benzyl)amino-benzaldehyde (CAS# 67676-47-5), 2-methyl-4-(N- ethyl-N-benzyl)-aminobenzaldehyde (CAS# 77147-13-8), 4,4'-Bis(4- methylphenyl)aminobenzaldehyde-l,l-diphenylhydrazonee (CAS# 83992-95-4), 2- methyl-4-dibenzyl aminobenzaldehyde-1,1- diphenylhydrazone (CAS# 103079-11-4), 2-methy l-4-(N-ethy l-N-benzyl)aminobenzaldehyde- 1 , 1 -diphenylhydrazone (C AS# 106618-38-6), 4-(N-ethyl-N-benzyl)amino benzoaldehyde- 1 , 1 -diphenylhydrazone (CAS# 96861-52-8), Triphenylamine (CAS# 603-34-9), 4-methyltriphenylamine (CAS# 4316-53-4 ), 4,4-Dimethyltriphenylamine (CAS# 20440-95-3), Tris (4- Bromophenyl) amine (CAS# 4316-58-9), 4,4'-Bis (4-methylphenyl) aminobenzaldehyde (CAS# 42906-19-4), 4-Diphenylamino Benzaldehyde (CAS# 4181-05-9), N,N,NI,N'-Tetra-phenyl-l,l'-biphenyl-4,4t-diamine(TPB) (CAS# 15546- 43-7), N,N,N',NI-tetra(4-methylphenyl)-l,lt-biphenyl-4,4t-diamine (CAS# 76185-65-4), N,N'-bis(4-methylphenyl) -N,N'-Bis(3,4-dimethylphenyl) -l,r-biphenyl-4,4'-diamine , NsN'-bis(3-methylphenyl)-N,N'-Bis(4-methylphenyl)-l ,r-biphenyl-4,4'-diamine (CAS# 261638-90-8), 3,3^5,5'-tetra-tert-butyl-4,4Miphenoquinone (CAS# 2455-14-3), 3,3',5,5'-tetramethyl-4,4'-diphenoquinone (CAS# 4906-22-3), S.S-dimethyLθ'^'-ditert- butyl- diphenoquinone (CAS# 134781-54-7), 3,3'-dimethyl-5,5'-ditert-butyl- diphenoquinone (CAS# 2417-00-7), Oxytitamivim phthalocyanine (CAS# 26201-32-1), Oxy vanadium phthalocyanine (CAS# 13930-88-6), Silicon dihydroxyl phthalocyanine (CAS# 19333-15-4) Chloride aluminium phthalocyanine (CAS# 14154-42-8), Ferreous phthalocyanine (CAS# 132-16-1), 2-(4-aminophenyl)-6-aminobenzoxazole (CAS# 16363-53-4), 2,5-bis(4-aminophenyl)-l,3,4-oxadiazole (CAS# 2425-95-8, 4,4'-[l,3,4- oxadiazole -2,5-diylbis(4, 1 -phenyleneazo)] bis[3-hydroxy-N-phenyl]-2- naphthalenecarboxamide (CAS# 70621-09-9), 4,4'-[l,3,4-oxadiazole-2,5-diylbis(4,l- phenyleneazo), bis[N-(2-chlorophenyl)-3-hydroxy-2-naphthalenecarboxamide (CAS# 109299-00-5), 4,4'-[l ,3,4-oxadiazole-2,5-diylbis(4,l-phenyleneazo)]bis[N-(4-chloro- 2,5-dimethoxyphenyl)]-3-hydroxy-2-naphthalenecarboxamide (CAS# 70621-24-8), 4,4'-[l,3,4-oxadiazole-2,5-diylbis(4,l-phenyleneazo)]bis[3-hydroxy-N-(2- methoxyphenyl)-2-naphthalenecarboxamide (CAS# 73212-56-3), 4,4'-[l,3,4- oxadiazole-2,5-diylbis[(2-methyl-4,l-phenylene)azo]bis[3-hydroxy-N-ρhenyl-2- naphthalenecarboxamide (CAS# 73212-59-6), 4,4'-[l,3,4-oxadiazole-2,5-diylbis(4,l- phenyleneazo)]bisjN-(2-ethoxyphenyl)3-hydroxy-2-naphthalenecarboxamide (CAS# 70621-14-6), N-(2-chlorophenyl)-4-[[4-[6-[[3-[[(2-chlorophenyl)amino]carbonyl]-2- hydroxy- 1 -naphthalenyl]azo]-benzoxazolyl]phenyl]azo]-3-hydroxy-2- naphthalenecarboxamide (CAS# 107047-67-6), Polyphenylene vinylene (PPV), 4- Dibenzylamino-2-methylbenzaldehyde-l,l-diphenylhydrazone (CAS # 103079-11-4), N,N'-Di(3-Methylphenyl)-1, I1 -biphenyl-4, 41 -diamine (CAS # 78888-06-9), Tris(4- Iodophenyl)amine (CAS# 4181-20-8), Tris(4-Nitroρhenyl)amine (CAS# 20440-93-1) and 1,4-Cyclohexanedione monoethylene acetal (CAS# 4746-97-8), each of which is commercially available from SinoRefin Corp. Located in Caohejing Hi-TECH Park Shanghai China. In other embodiments, other hole carriers may be utilized. Charge transport enhancers include various substituted alkyl phenols.

[0012] The binder or matrix 42 may comprise one or more polymers including, but not limited to, bis-phenol A and related polycarbonates. Matrix 42 may also include various polyester structural polymers suitable for use in organic photoconductors. For example, a vinyl polymer such as polymethyl methacrylate, polystyrene or polyvinyl chloride, or its copolymer, polycarbonate, polyester, polyester carbonate, polysulfonate, polyimide, or a phenoxy, epoxy or silicone resin may be used. Partially cross linked products thereof may also be used.

[0013] According to one example embodiment, a majority of charge transport layer 30 has a substantially uniform proportion of matrix 42 to charge transport chemicals 40 within a range of from 30 to 200 parts by weight, nominally from 40 to 150 parts by weight, per 100 parts by weight of the binder or matrix 42. As will be described hereafter, surface portions of charge transport layer 30 have a lower density of charge transport materials.

[0014] The charge transport layer 30 has a thickness from 10 to 60 microns, nominally from 10 to 45 microns. In the particular embodiment illustrated, charge transport layer 30 has a thickness of a approximately 16 μ. In other embodiments, the carrier or charge transport layer 30 may have other thicknesses and may additionally include various additives such as an antioxidant and a sensitizer.

[0015] As further shown by Figure 1, charge transport layer 30 is configured such that surface portions of charge transport layer 30 have a lower density of charge carrier materials as compared to other portions of charge transport layer 30. In particular, charge transport layer 30 includes a first portion 46 along surface 34 of layer 30 and a second portion 48 extending from the first portion 46 to a second opposite surface 50 of layer 30. As compared to portion 48, portion 46 has a lower density of charge carrier chemicals. As a result, chemical or electrostatic reactions that would normally occur along surface 34 which would otherwise result in contaminants bonding to exposed charge transport materials is postponed or inhibited. By postponing or preventing such buildup of contamination along surface 34, photoconductor 20 experiences less lateral conductivity resulting from conductive contaminants and less charge traps resulting from non-conductive contaminants. Thus, print quality may be enhanced and the useful life of photoconductor 20 may be prolonged.

[0016] In the particular example illustrated, portion 46 has a depth of between about 20 nm and about 35 ran. Layer 30 has a total thickness or depth of about 16 μ. In one embodiment, portion 46 has a reduced density of charge transport chemicals 40 such that portion 48 has a density of charge transport materials at least twice that of portion 46. In such an embodiment, portion 48 has a density of charge transport chemicals 40 that is less than or equal to about 4.5 times that of the density of charge transport chemicals 40 of portion 46. In one embodiment, portion 46 has a percent by weight charge carrier chemicals to binder resin of between about 3 percent by weight and about 15 percent by weight , and nominally about 3 percent by weight. Portion 48 has a percent by weight charge carrier chemicals to binder resin of between about 20 percent by weight and about 45, percent by weight and nominally about 35 percent by weight. In particular embodiments, it has been found that such embodiments of photoconductor 20 may have a life increase of 33% to 500% as compared to similar photoconductors wherein charge transport layer 30 has a substantially uniform density of charge transport chemicals 40.

[0017] According to one embodiment, portions 46 and 48 are initially provided with substantially similar densities of charge transport chemicals 40 within matrix 42. Charge transport layer 30 is treated or "immunized" such that portion 46 has a lower density of charge transport materials. In one embodiment, a solvent is applied to surface 34, facilitating subsequent washing away of charge transport materials from matrix 42 along surface 34. As a result, surface 34, after removal of charge transport materials, is porous.

[0018] According to one embodiment, portion 46 has between about 60% and about 90% of the charge transport materials removed. Portion 46 and 48, collectively, have between about 10% and about 20% of charge transport chemicals 40 removed. Although Figure 1 schematically illustrates a sharp demarcation between portions 46 and 48, in other embodiments, there may be a gradual transition between portion 46, having a lower density of charge transport chemicals 40, and portion 48 having a greater density of charge transport chemicals 40. In particular embodiments, even within portion 46, the density of charge transport chemicals 40 may vary, with the lowest density of charge transport chemicals 40 (and corresponding higher density of matrix 42) occurring closer to surface 34. Likewise, regions of portion 48 closer to surface 34 may have lower densities of charge transport chemicals 40 (and higher densities of matrix 42). Such transitioning may be dependent upon the particular solvent or immunization fluid employed, characteristics of charge transport chemicals 40 and matrix 42 and characteristics of the process used to form layer 30 or remove such charge transport chemicals 40 from proximate to surface 34 of layer 30. [0019] Figure 2 schematically illustrates imaging system or printer 120, one example of an imaging system that may employ photoconductor 20 (enlarged in Figure 2 for purposes of illustration). Printer 120 is an electrophotographic printer, using static electricity to form an image or pattern of charge to printing material upon a surface which is subsequently transferred to a printed medium. Because printer 120 employs photoconductor 20, printer 120 may print a greater number of images or sheets prior to photoconductor 20 having to be replaced due to contamination. [0020] In the particular example illustrated, printer 120 comprises a liquid electrophotographic (LEP) printer. In other embodiments, photoconductor 20 be employed as part of other electrophotographic printing systems. In addition to photoconductor 20, printer 120, (sometimes embodied as part of an offset color press) includes drum 122, charger-126, imager 128, developer 130, intermediate transfer member 134, heating system 136, impression member 138 and cleaning station 140. Drum 122 comprises a movable support structure supporting photoconductor 20. In one embodiment, photoconductor 20 is removably attached to drum 122, facilitating replacement of photoconductor 20. In one embodiment, photoconductor 20 is clamped to drum 122 providing electrical contact between electrically conductive layer 24 and grounding contacts of drum 122. In other embodiments, photoconductor 20 may be removably mounted to drum 122 in other fashions or maybe fixedly secured or coupled to drum 122.

[0021] For purposes of this disclosure, the term "coupled" shall mean the joining of two members directly or indirectly to one another. Such joining may be stationary in nature or movable in nature. Such joining may be achieved with the two members or the two members and any additional intermediate members being integrally formed as a single unitary body with one another or with the two members or the two members and any additional intermediate member being attached to one another. Such joining may be permanent in nature or alternatively may be removable or releasable in nature. The term "operably coupled" shall mean that two members are directly or indirectly joined such that motion may be transmitted from one member to the other member directly or via intermediate members.

[0022] Drum 122 is configured to be rotationally driven about axis 142 in a direction indicated by arrow 144 by a motor and transmission (not shown). As a result, distinct surface portions of photoconductor 20 are transported between stations of printer 120 including charger 126, imager 128, ink developers 130, transfer member 134 and charger eraser 132. In other embodiments, photoconductor 20 may be removably supported for being driven between substations in other manners. For example, photoconductor 20 may be provided as part of an endless belt supported by a plurality of rollers.

[0023] Charger 126 comprises a device configured to electrostatically charge surface 34 of photoconductor 20. In one embodiment, charger 126 comprises a charge roller which is rotationally driven while in sufficient proximity to photoconductor 20 so as to transfer a negative static charge to surface 34 of photoconductor 20. In embodiments where charger 126 comprises a charge roller, charger 126 may provide enhanced charging of photo conductor 20 as compared to other charging devices such as scorotrons. However, in such embodiments, photoconductors having a substantially uniform density of charge transport chemicals 40 throughout layer 30 may be more susceptible to contamination. In contrast, it has been found that the use of photoconductor 20 addresses such issues associated with charger 126 comprising a charge roller. In other embodiments, charger 126 may alternatively comprise one or more corotrons or scorotrons. In still other embodiments, other devices for electrostatically charging surface 34 of photoconductor 20 may be employed. [0024] Imager 128 comprises any device configured correctly upon surface 34 so as to form an image. In the example shown, imager 128 comprises a scanning laser which is moved across surface 34 as drum 122 and photoconductor 20 are rotated about axis 142. Those portions of surface 34 which are impinged by light or laser 150 are electrostatically discharged to form an image (or latent image) upon surface 34. In other embodiments, imager 128 may alternatively comprise other devices configured to selectively emit or selectively allow light to impinge upon surface 34. For example, in other embodiments, imager 128 may alternatively include one or more shutter devices which employ liquid crystal materials to selectively block light and to selectively allow light to pass to surface 34. In yet other embodiments, imager 128 may alternatively include shutters which include micro or nano light-blocking shutters which pivot, slide or otherwise physically move between a light blocking and light transmitting states. [0025] Ink developers 130 comprises devices configured to apply printing material to surface 34 based upon the electrostatic charge upon surface 34 and to develop the image upon surface 34. In the particular example shown, such printing material may comprise a liquid or fluid ink comprising a liquid carrier and colorant particles. The colorant particles have a size of less than 2 μ. In different embodiments, the particle sizes may be different. In the example illustrated, the printing material generally includes approximately 3% by weight, colorant particles or solids part to being applied to surface 34. In one embodiment, the colorant particles include a toner binder resin comprising hot melt adhesive. In one embodiment, the printing material comprises HEWLETT- PACKARD ELECTRO INK commercially available from Hewlett-Packard. [0026] According to one embodiment, ink developers 130 comprise binary ink developers (BIDs) (commercially available from Hewlett-Packard) circumferentially located about drum 122 and photoconductor 20. Such ink developers are configured to form a substantially uniform 6 μ thick electrostatically charged film composed of approximately 20% solids which is transferred to surface 34. In yet other embodiments, ink developers 130 may comprise other devices configured to transfer electrostatically charged liquid printing material or toner to surface 34. In still other embodiments, developers 130 may be configured to apply a dry electrostatically charged printing material, such as dry toner, to surface 34.

[0027] Intermediate transfer member 134 comprises a member configured to transfer the printing material upon surface 34 to a print medium 152 (schematically shown). Intermediate transfer member 134 includes an exterior surface 154 which is resiliently compressible and which is also configured to be electrostatically charged. Because surface 154 is resiliently compressible, surface 154 conforms and adapts to irregularities in print medium 152. Because surface 154 is configured to be electrostatically charged, surface 154 may be charged so as to facilitate transfer of printing material from surface 34 to surface 154. In one embodiment, intermediate transfer member 134 may include a drum 156 and an external blanket 158. Drum 156 supports blanket 158 which provides intermediate transfer member 134 with surface 154. In other embodiments, intermediate transfer member 134 may have other configurations. For example, in other embodiments, intermediate transfer member 134 may alternatively comprise an endless belt supported by a plurality of rollers in contact with or in close proximity to surface 34.

[0028] Heating system 136 comprises one or more devices configured to apply heat to printing material being carried by surface 154 from photoconductor 20 to media 152. In the example illustrated, heating system 136 includes internal heater 160 and external heater 162. Internal heater 160 comprises a heating device located within drum 156 that is configured to emit heat or inductively generate heat which is transmitted to surface 154 to heat and dry the printing material carried at surface 154. External heater 162 comprises one or more heating units located about transfer member 134. According to one embodiment, heaters 160 and 162 may comprise infrared heaters. [0029] Heaters 160 and 162 are configured to heat printing material to a temperature of at least 85°C and less than or equal to about 1100C. In still other embodiments, heaters 160 and 162 may have other configurations and may heat printing material upon transfer member 134 to other temperatures. In particular embodiments, heating system 136 may alternatively include one of either internal heater 160 or external heater 162. In yet other embodiments, heating system 136 may be omitted.

[0030] Impression member 138 comprises a cylinder adjacent to intermediate transfer member 134 so as to form a nip 164 between member 134 and member 138. Media 152 is generally fed between transfer member 134 and impression member 138, wherein the printing material is transferred from transfer member 134 to medium 152 at nip 164. Although impression member 138 is illustrated as a cylinder or roller, impression member 138 and alternatively comprise an endless belt or a stationary surface against which intermediate transfer member 134 moves.

[0031] Cleaning station 140 comprises one or more devices configured to remove any residual printing material and electrical charge from photoconductor 20 prior to surface areas of photoconductor 20 being once again charged at charger 126. In one embodiment, cleaning station 140 may comprise one or more devices configured to apply a cleaning fluid to surface 34, wherein residual toner particles are removed by one or more is absorbent rollers. In one embodiment, cleaning station 140 may additionally include one or more scraper blades. In yet other embodiments, other devices may be utilized to remove residual toner and electrostatic charge from surface 34. [0032] In operation, charger 126 electrostatically charges surface 34 with a negative charge across substantially an entire area of surface 34. Surface 34 is subsequently exposed to light from imager 128. In particular, surface 34 is exposed to laser 150 which is controlled by a raster image processor that converts instructions from a digital file into on/off instructions for laser 150. Laser light 150 passes through the substantially transparent charge transport layer 30 so as to bombard selected portions of charge generation layer 28 (shown in Figure 1). Upon being bombarded, selected portions of charge generation layer 28 emit electron hole charge pairs. Electrons are available to transferred through barrier layer 26 to electrically conductive layer 24. At the same time, the same portions of emitted positive charge or holes are carried by charge transport chemicals 40 across charge transport layer 30 to surface 34 where such holes neutralize or discharge the negative charge along corresponding portions of surface 34. This results in a latent image being formed for those electrostatically discharged portions of surface 34.

[0033] Ink developer 130 develops an image upon surface 34 by applying electrostatically charged ink having a negative charge (or a charge equal to the charge apply by charger 126). Once the image upon surface 34 is developed, cleaning station 140 erases any remaining electrical charge upon such portions of surface 34 and ink image is transferred to surface 154 of intermediate transfer member 34. In the example shown, the printing material formed comprises and approximately 1.0 μ thick layer of approximately 90% solids color or particles upon intermediate transfer member 134. [0034] Heating system 136 applies heat to such printing material upon surface 154 so as to evaporate the carrier liquid of the printing material and to melt toner binder resin of the color and particles or solids of the printing material to form a hot melt adhesive. Thereafter, the layer of hot colorant particles forming an image upon surface 154 is transferred to media 152 passing between transfer member 134 and impression member 138. In the embodiment shown, the hot colorant particles are transferred to print media 152 at approximately 900C. The layer of hot colorant particles cool upon contacting media 152 on contact in nip 164.

[0035] These operations are repeated for the various colors or preparation of the final image to be produced upon media 152. In other embodiments, in lieu of creating one color separation at a time on a surface 154, sometimes referred to as "multi-shot" process, the above process may be modified to employ a one-shot color process in which all color separations are layered upon surface 154 of intermediate transfer member 134 prior to being transferred to and deposited upon medium 152. [0036] Figure 3 schematically illustrates treatment system 220 for forming one embodiment of photoconductor 20. Treatment system 220 is configured to treat or "immunize" an existing photoconductor 320 (shown in Figure 4) to form photoconductor 20 (shown in Figure 1). Photoconductor 320 may be a preformed or pre-existing photoconductor. Like photoconductor 20, photoconductor 320 includes support 22, electrically conductive layer 24, barrier layer 26 and charge generation layer 28. Unlike photoconductor 20, photoconductor 320 includes charge transport layer 330. Like charge transport layer 30, charge transport layer 330 includes charge transport or carrier chemicals 40 captured and dispersed throughout a binder resin or matrix 42. However, unlike charge transport layer 30 of photoconductor 320, charge transport layer 330 has a substantially uniform dispersion and density of transport chemicals 40 throughout layer 330. In other words, the density of charge transport chemicals 40 along surface 34 of layer 330 is substantially similar to the density of charge transport chemicals 40 anywhere throughout layer 330, including portions of layer 330 adjacent surface 50 of charge transport layer 330. As noted above, if photoconductor 320 were to be employed in printer 120 without immunization, surface 34 of charge transport layer 330 may have a greater susceptibility to chemical and electrostatic interactions which contaminate surface 34, causing such issues as latteral conductivity in the case of conductive contamination and charged traps in the case of non-conductive contamination.

[0037] System 220 in Figure 3 comprises one example system for carrying out a process or method for treating photoconductor 320 to immunize photoconductor 320 against such enhanced susceptibility to contamination. In particular, system 220 immunizes photoconductor 320 to modify charge transport layer 330 so as to have the architecture and composition of charge transport layer 30 illustrated and described above with respect to Figure 1. In particular, system 220 modifies charge transport layer 330 such that charge transport layer 330 has a lower density of charge transport chemicals 40 adjacent to surface 34. System 220 includes transport system 224, . removal units 228A, 228B (collectively referred to as units 226), cleaning units 234A, 234B, drying units 240, motor 242 and controller 246.

[0038] Transport system 224 comprises a mechanism configured to transport or carry photoconductor 320 (shown in Figure 4) to each of removal units 228, cleaning units 234 and drying units 240. In the particular example illustrated, transport 224 includes supply reel 250 and take-up reel 252. Supply reel 250 comprises a spool or winding of photoconductor 320 which is configured to be rotated about axis 254 as reel 250 is unwound. Take up reel 252 comprises a spool or reel configured to take up or wind photoconductor 320 after it has been immunized to form photoconductor 20. Reels 250 and 252 cooperate to extend and move a web 257 of photoconductor 320 across each of units to 228, 234 and 240. Take up reel 252 is configured to be rotationally driven in a direction indicated by arrow 258 such that the web 257 is moved across such units in a direction as indicated by arrow 255. In one embodiment, take up reel 252 in rotationally driven by motor 242. In other embodiments, take up reel 256 may be rotationally driven by a separate distinct motor. In yet other embodiments, other driven rollers may be used to move web 257 as well to rotate take-up reel 252.

[0039] Removal units 228 comprise stations or systems configured to apply and immunization fluid along with pressure or rubbing to facilitate removal of a predetermined percentage range of charge transport chemicals 40 from matrix 42. Charge transport or carrier chemicals 40 are removed by a predetermined extent or depth of layer 330. In one embodiment, the applied charge transport chemicals removing fluid or immunization fluid comprises a liquid configured to extract charge transport chemicals from matrix 42 without significantly changing the structural characteristics of matrix 42. Examples of immunization fluids include, not limited to, low viscosity liquids of organic esters, ketones, aldehydes, carboxylic acids, halogenated organic solvents, organic carbonates and inorganic acids. According to one example embodiment, wherein matrix 42 comprises polycarbonate, the immunization fluid may comprise a propylene carbonate solvent. In other embodiments, other immunization fluids or solvents may be utilized.

[0040] In the example illustrated, each removal unit 228 includes supply spool 260, take-up spool 262 and pressure roller 264. Supply spool 260 comprises a winding of a strip or web 266 of one or more materials configured to carry the immunization fluid. In one embodiment, web 266 comprises a strip of one or more materials configured to absorb such immunization fluid. For example, in one embodiment, web 266 to may comprise a polyester fabric. In one embodiment, spool 260 supplies a winding of such absorbent material that is pre-soaked or pre-saturated with the immunization fluid. In another embodiment, web 266 of absorbent material or non-absorbent material may be passed through a bath or basin of immunization fluid or may have immunization fluid applied to at least one face of web 266 by a brush, sponge or other applicator which is supplied with the immunization fluid.

[0041] Take-up spool 262 comprises a reel or spool about which used web 266 is a wound and collected for disposal or recycling. Take up spool 262 is operably coupled to motor 242 for being rotationally driven by motor 242. As a result, web 266 is moved across and against surface 34 of photoconductor 320. Spools 260 and 262 provide a continuous clean unused supply of web 266 for carrying and applying the immunization fluid against surface 34 of photoconductor 320.

[0042] Pressure rollers 264 press web 266, carrying the immunization fluid, against surface 34. Pressure rollers 264 facilitate application of a controlled amount of pressure to reduce likelihood of damage to matrix 42 and photoconductor 320 during such immunization. In one embodiment, pressure rollers 264 are resiliently biased toward surface 34 with a controlled amount of pressure. For example, pressure rollers 264 may be resiliently biased towards surface 34 by one or more springs 265 (schematically shown) captured between a housing or frame (not shown) and an axle of an associated roller 264 configured to apply the desired amount of pressure.

[0043] Although each of units 228 is illustrated as including a single pressure roller 264, in other embodiments, such units may include one or more additional pressure rollers 264 to increase the area of photoconductor 320 contacted by web 266 at each unit. In other embodiments, web 266 may be a continuous endless belt which is repeatedly driven or moved across surface 34 of photoconductor 320. In such an embodiment, additional mechanisms for supplying the web 266 with immunization fluid and for at least periodically cleaning web 266 may be provided. [0044] Cleaning units 234A and 234B comprise stations or systems configured to apply a cleaning fluid to surface 34 after immunization fluid has been applied to surface 34. The applied cleaning fluids are liquids configured to dilute or neutralize the immunization fluid and to facilitate removal of the immunization fluid. In one embodiment, the cleaning fluid may comprise water.

[0045] Cleaning units 234 reduce the likelihood of such applied immunization fluids remaining in contact with surface 34 for too long of a period of time. Cleaning units 234 further inhibit the immunization fluid from penetrating too far into charge transport layer 330. In addition, cleaning units 234 assist in removing the previously applied immunization fluid as well as any dissolved or loosened charge transport chemicals 40. [0046] In the embodiment illustrated, cleaning units 234 include supply spool 270, take-up spool 272 and pressure roller 274. Supply spool 270 comprises a winding of a strip or web 276 of one or more materials configured to carry a cleaning fluid. In the example embodiment illustrated, web 276 comprises a strip of one or more materials configured to absorb such cleaning fluid. For example, in one embodiment, web 276 may comprise a polyester fabric. In one embodiment, spool 260 supplies a winding of such absorbent material that is pre-soaked or pre-saturated with the cleaning fluid. In another embodiment, web 276 of absorbent material or non-absorbent material may be passed through a bath or basin of cleaning fluid or may have cleaning fluid applied to at least one face of web 276 by a brush, sponge or other applicator which is supplied with the cleaning fluid.

[0047] Take-up spool 272 comprises a reel or spool about which used web 276 is wound and collected for disposal or recycling. Take up spool 272 is operably coupled to motor 242 for being rotationally driven by motor 242. As a result, web 276 is moved across and against surface 34 of photoconductor 320. Spools 270 and 272 provide a continuous clean and unused supply of web 276 for carrying and applying the cleaning fluid against surface 34 of photoconductor 320.

[0048] Pressure rollers 272 press web 276, carrying the cleaning fluid, against surface 34. Pressure rollers 272 facilitate application of a controlled amount of pressure to reduce likelihood of damage to matrix 42 and photoconductor 320 during cleaning. In one embodiment, pressure rollers 274 are resiliently biased toward surface 34 with a controlled amount of pressure. For example, pressure rollers 274 may be resiliently biased towards surface 34 by one or more springs 275 (schematically shown) captured between a housing or frame (not shown) and an axle of an associated roller 274 configured to apply the desired amount of pressure.

[0049] Although each of units 234 is illustrated as including a single pressure roller 274, in other embodiments, such units may include one or more additional pressure rollers 274 to increase the area of photoconductor 320 contacted by web 276 at each unit. In other embodiments, web 276 may be a continuous endless belt which is repeatedly driven or moved across surface 34 of photoconductor 320. In such an embodiment, additional mechanisms for supplying the web 276 with cleaning fluid and for at least periodically cleaning web 276 may be provided.

[0050] Drying units 240 comprise stations or systems configured to dry surface 34 after immunization and the cleaning of surface 34 with fluids. Drying units 240 absorb any remaining immunization fluid or cleaning fluid as well as any remaining charge transport chemicals or chemicals 40

[0051] In the embodiment illustrated, drying units 240 include supply spool 280, take- up spool 282 and pressure roller 284. Supply spool 280 comprises a winding of a strip or web 286 of one or more materials configured to absorb any remaining fluids upon surface 34. For example, in one embodiment, web 286 to may comprise a polyester fabric.

[0052] Take-up spool 282 comprises a reel or spool about which used web 286 is a wound and collected for disposal or recycling. • Take up spool 282 is operably coupled to motor 242 for being rotationally driven by motor 242. As a result, web 286 is moved across and against surface 34 of photoconductor 320. Spools 280 and "282 provide a continuous clean unused supply of web 286 for absorbing and curing away fluids from surface 34 of photoconductor 320.

[0053] Pressure roller 282 presses web 286 against surface 34. Pressure roller 282 facilitates application of a controlled amount of pressure to reduce likelihood of damage, such as scratches, to surface 34. In one embodiment, pressure roller 284 is resiliently biased toward surface 34 with a controlled amount of pressure. For example, pressure roller 284 may be resiliently biased towards surface 34 by one or more springs 285 (schematically shown) captured between a housing or frame (not shown) and an axle of an associated roller 284 configured to apply the desired amount of pressure. [0054] Although units 240 are illustrated as including a single pressure roller 284, in other embodiments, such units may include one or more additional pressure rollers 284 to increase the area of photoconductor 320 contacted by web 286. In other embodiments, web 286 may be a continuous endless belt which is repeatedly driven or moved across surface 34 of photoconductor 320.

[0055] Although treatment system 220 is illustrated as including two sets of immunization, cleaning and drying units, in other embodiments, system 220 may include a single set or greater than two sets. Although immunization of photoconductor 320 is illustrated as being performed in a reel-to-reel process, enhancing efficiency, in other embodiments, photoconductor 320 may be immunized using other transport mechanisms. In still other embodiments, charge transport chemicals 40 may be removed from matrix 42 in other fashions.

[0056] Motor 242 comprises a source of torque for rotationally driving take-up rollers 262, 272 and 282 of units 228, 234 and 240, respectively. In the particular example illustrated, motor 242 is further configured to rotationally dried take-up reel 256. Although motor 242 is illustrated as a single motor, such as an electric motor, operably connected or coupled to each of rollers 262, 272, 282 and reel 252 by a transmission 290 (schematically shown), in other embodiments, multiple independent motors may be used to individually rotationally drive such rollers or 262, 272, 282 and reel 252. [0057] Controller 246 comprises one or more processing units configure to generate control signals directing operation least motor 242. For purposes of this application, the term "processing unit" shall mean a presently developed or future developed processing unit that executes sequences of instructions contained in a memory. Execution of the sequences of instructions causes the processing unit to perform steps such as generating control signals. The instructions may be loaded in a random access memory (RAM) for execution by the processing unit from a read only memory (ROM)5 a mass storage device, or some other persistent storage. In other embodiments, hard wired circuitry may be used in place of or in combination with software instructions to implement the functions described. For example, controller 92 may be embodied as part of one or more application-specific integrated circuits (ASICs). Unless otherwise specifically noted, the controller is not limited to any specific combination of hardware circuitry and software, nor to any particular source for the instructions executed by the processing unit. Controller 246 generates control signals such that the web 257 of photoconductor 320 is moved relative to units to 28, 234 and 240 such that treatment occurs at a proper temperature, contact time and mechanical energy.

[0058] According to one embodiment, matrix 42 comprises a polycarbonate. The hole carriers comprise aromatic amines and aromatic hydrazones. The charge transport enhancers include various substituted alkyl phenol. The immunization fluid comprises propylene carbonate, the cleaning fluid comprises water and each of webs 266, 276 and 286 comprise polyester fabric. In such an embodiment, such treatment occurs at room temperature. Each of pressure rollers 264, 274 and 284 applies a circular mechanical motion of about 25 cm per second with a force of about 5 g per cm2. Surface 34 is contacted by at each unit at least 5 seconds. In addition, the immunization fluid remains in contact with surface 34 between rubbing with the immunization fluid at pressure rollers 264 and rubbing surface 34 with cleaning fluid at rollers 274. The total time for contact of the immunization fluid or solvent with surface 34 (rubbing time plus additional time before rubbing with cleaning fluid) at the two pairs of immunization and cleaning units is less than or equal to about two minutes. As a result, although the immunization fluid has sufficient contact time with surface 34 to remove a desired amount of charge transport materials to convert photoconductor 320 to photoconductor 20, the immunization fluid is less likely to damage surface 34 by softening the polycarbonate matrix 42. In other embodiments, different contact times may be appropriate for different immunization fluids or different solvents depending on how chemically aggressive such immunization fluids are with respect to the polycarbonate matrix 42 or other structural polymers forming matrix 42.

[0059] Although the present disclosure has been described with reference to example embodiments, workers skilled in the art will recognize that changes may be made in form and detail without departing from the spirit and scope of the claimed subject matter. For example, although different example embodiments may have been described as including one or more features providing one or more benefits, it is contemplated that the described features may be interchanged with one another or alternatively be combined with one another in the described example embodiments or in other alternative embodiments. Because the technology of the present disclosure is relatively complex, not all changes in the technology are foreseeable. The present disclosure described with reference to the example embodiments and set forth in the following claims is manifestly intended to be as broad as possible. For example, unless specifically otherwise noted, the claims reciting a single particular element also encompass a plurality of such particular elements.

Claims

WHAT IS CLAIMED IS:
1. An apparatus comprising: a photoconductor comprising : a charge generation layer electrically coupled to the electrically conductive layer; and a charge transport layer electrically coupled to the charge generation layer, the charge transport layer comprising: a matrix; and charge transport chemicals within the matrix, wherein the charge transport layer has a first portion adjacent a first surface of the charge transport layer and a second portion extending from the first portion to a second opposite surface of the charge transport layer, the first portion having a first density of the charge transport chemicals and the second portion having a second greater density of the charge transport chemicals.
2. The apparatus of claim 1, wherein the first portion has a depth of between about 20 nm and about 35 nm.
3. The apparatus of claim 2, wherein the second density is at least about twice that of the first density.
4. The apparatus of claim 2, wherein the second density is less than about 4.5 times the first density.
5. The apparatus of claim 1, wherein the first density is less than or equal to about 15 percent by weight of charge transport chemicals to matrix..
6. The apparatus of claim 5, wherein the second density is at least 20 percent by weight of charge transport chemicals to matrix.
7. The apparatus of claim 1, wherein the first portion has between about 60% to about 90% of the charge transport material removed and wherein the first portion and the second portion, collectively, have between about 10% to about 20% of the charge transport material removed.
8. The apparatus of claim 1 , wherein the matrix is polymeric.
9. The apparatus of claim 1, wherein the charge transport chemicals include hole carriers and charge transport enhancers.
10. The apparatus of claim 1 further comprising a movable support structure supporting the photoconductor.
11. The apparatus of claim 1 further comprising: a charger configured to charge the first surface of the charge transport layer; an imager configured to irradiate the photoconductor to form an image; and a developer configured to apply charged printing material to the photoconductor.
12. The apparatus of claim 11 , wherein the charger comprises a roller configured to transfer charge to be photoconductor.
13. The apparatus of claim 1, wherein the surface of the charge transport layer is porous.
14. A method comprising: providing a photoconductor having a first surface and a charge transport layer proximate the first surface, the transport layer having charge transport chemicals within a matrix; and removing charge transport chemicals from the matrix proximate the first surface.
15. The method of claim 14, wherein at least 60% of the charge transport chemicals are removed.
16. The method of claim 15, wherein less than or equal to about 90% of the charge transport chemicals are removed.
17. The method of claim 14, wherein the charge transport chemicals are removed such that the charge transport layer has a first portion proximate the first surface with a depth of between about 20 nm and about 35 nm and a second portion extending from the first portion to a second opposite surface of the charge transport layer and such that the first portion has between about 60% and about 90% of the charge transport chemicals removed and wherein the first portion and the second portion, collectively, have between about 10% and about 20% of the charge transport chemicals removed.
18. The method of claim 14, wherein the removing comprises applying a solvent to the first surface.
19. The method of claim 14, wherein the removal of the charge transport chemicals is performed prior to any application of printing material to the first surface.
20. A system comprising: a solvent application station configured to apply a solvent to a surface of a charge transport layer of a photoconductor, the solvent being configured to remove charge transport chemicals from a matrix surrounding the charge transport chemicals along the surface; and a cleaning station configured to remove the applied solvent and remove charge transport chemicals from the surface.
PCT/US2007/010254 2007-04-25 2007-04-25 Photoconductor WO2008133617A1 (en)

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