CA2047675C - Liquid developer systems with self-replenishment of bulk conductivity - Google Patents
Liquid developer systems with self-replenishment of bulk conductivityInfo
- Publication number
- CA2047675C CA2047675C CA002047675A CA2047675A CA2047675C CA 2047675 C CA2047675 C CA 2047675C CA 002047675 A CA002047675 A CA 002047675A CA 2047675 A CA2047675 A CA 2047675A CA 2047675 C CA2047675 C CA 2047675C
- Authority
- CA
- Canada
- Prior art keywords
- liquid
- liquid developer
- developer system
- charge director
- director compound
- Prior art date
- Legal status (The legal status 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 status listed.)
- Expired - Fee Related
Links
- 239000007788 liquid Substances 0.000 title claims abstract description 88
- 239000002245 particle Substances 0.000 claims abstract description 36
- 150000001875 compounds Chemical class 0.000 claims abstract description 30
- 238000003384 imaging method Methods 0.000 claims abstract description 20
- 239000007790 solid phase Substances 0.000 claims abstract description 8
- 238000000034 method Methods 0.000 claims description 10
- 239000007787 solid Substances 0.000 claims description 9
- 239000000758 substrate Substances 0.000 claims description 7
- 230000008569 process Effects 0.000 claims description 5
- HCWYXKWQOMTBKY-UHFFFAOYSA-N calcium;dodecyl benzenesulfonate Chemical compound [Ca].CCCCCCCCCCCCOS(=O)(=O)C1=CC=CC=C1 HCWYXKWQOMTBKY-UHFFFAOYSA-N 0.000 claims description 4
- 239000000203 mixture Substances 0.000 claims description 4
- 230000003287 optical effect Effects 0.000 claims description 3
- 239000011148 porous material Substances 0.000 claims description 3
- HFQQZARZPUDIFP-UHFFFAOYSA-M sodium;2-dodecylbenzenesulfonate Chemical compound [Na+].CCCCCCCCCCCCC1=CC=CC=C1S([O-])(=O)=O HFQQZARZPUDIFP-UHFFFAOYSA-M 0.000 claims description 3
- JSFATNQSLKRBCI-NLORQXDXSA-N 73945-47-8 Chemical compound CCCCCC(O)\C=C\C=C\C\C=C\C\C=C\CCCC(O)=O JSFATNQSLKRBCI-NLORQXDXSA-N 0.000 claims description 2
- 150000001338 aliphatic hydrocarbons Chemical class 0.000 claims description 2
- 229930195733 hydrocarbon Natural products 0.000 claims 2
- 150000002430 hydrocarbons Chemical class 0.000 claims 2
- 239000004215 Carbon black (E152) Substances 0.000 claims 1
- 238000009835 boiling Methods 0.000 claims 1
- 229910052751 metal Inorganic materials 0.000 claims 1
- 239000002184 metal Substances 0.000 claims 1
- 239000000344 soap Substances 0.000 claims 1
- 230000003068 static effect Effects 0.000 claims 1
- CNPVJWYWYZMPDS-UHFFFAOYSA-N 2-methyldecane Chemical compound CCCCCCCCC(C)C CNPVJWYWYZMPDS-UHFFFAOYSA-N 0.000 description 21
- 239000000463 material Substances 0.000 description 13
- 239000000243 solution Substances 0.000 description 9
- 241000274177 Juniperus sabina Species 0.000 description 6
- 239000006185 dispersion Substances 0.000 description 6
- 235000001520 savin Nutrition 0.000 description 6
- 239000000725 suspension Substances 0.000 description 6
- 238000002360 preparation method Methods 0.000 description 5
- 238000007747 plating Methods 0.000 description 4
- OYPRJOBELJOOCE-UHFFFAOYSA-N Calcium Chemical compound [Ca] OYPRJOBELJOOCE-UHFFFAOYSA-N 0.000 description 3
- 239000011575 calcium Substances 0.000 description 3
- 229910052791 calcium Inorganic materials 0.000 description 3
- 238000010438 heat treatment Methods 0.000 description 3
- 239000006228 supernatant Substances 0.000 description 3
- 238000011067 equilibration Methods 0.000 description 2
- ZXEKIIBDNHEJCQ-UHFFFAOYSA-N isobutanol Chemical compound CC(C)CO ZXEKIIBDNHEJCQ-UHFFFAOYSA-N 0.000 description 2
- 238000005259 measurement Methods 0.000 description 2
- 238000002156 mixing Methods 0.000 description 2
- 238000012544 monitoring process Methods 0.000 description 2
- 238000012360 testing method Methods 0.000 description 2
- 238000012546 transfer Methods 0.000 description 2
- 238000005406 washing Methods 0.000 description 2
- ZRRKYAMPPGJTDM-UHFFFAOYSA-N 1,4-bis(2-methylpropoxy)-1,4-dioxobutane-2-sulfonic acid;calcium Chemical compound [Ca].CC(C)COC(=O)CC(S(O)(=O)=O)C(=O)OCC(C)C ZRRKYAMPPGJTDM-UHFFFAOYSA-N 0.000 description 1
- CBCQTCPKFYFJEU-UHFFFAOYSA-N 1,4-dioxo-1,4-dipentoxybutane-2-sulfonic acid Chemical compound CCCCCOC(=O)CC(S(O)(=O)=O)C(=O)OCCCCC CBCQTCPKFYFJEU-UHFFFAOYSA-N 0.000 description 1
- FGRBYDKOBBBPOI-UHFFFAOYSA-N 10,10-dioxo-2-[4-(N-phenylanilino)phenyl]thioxanthen-9-one Chemical group O=C1c2ccccc2S(=O)(=O)c2ccc(cc12)-c1ccc(cc1)N(c1ccccc1)c1ccccc1 FGRBYDKOBBBPOI-UHFFFAOYSA-N 0.000 description 1
- SNPHTGNJBGLZTN-UHFFFAOYSA-N 4-(2-methylpropoxy)-4-oxo-3-sulfobutanoic acid Chemical compound CC(C)COC(=O)C(S(O)(=O)=O)CC(O)=O SNPHTGNJBGLZTN-UHFFFAOYSA-N 0.000 description 1
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 1
- XZMCDFZZKTWFGF-UHFFFAOYSA-N Cyanamide Chemical compound NC#N XZMCDFZZKTWFGF-UHFFFAOYSA-N 0.000 description 1
- 229920003345 Elvax® Polymers 0.000 description 1
- CTQNGGLPUBDAKN-UHFFFAOYSA-N O-Xylene Chemical compound CC1=CC=CC=C1C CTQNGGLPUBDAKN-UHFFFAOYSA-N 0.000 description 1
- BUGBHKTXTAQXES-UHFFFAOYSA-N Selenium Chemical compound [Se] BUGBHKTXTAQXES-UHFFFAOYSA-N 0.000 description 1
- ULUAUXLGCMPNKK-UHFFFAOYSA-N Sulfobutanedioic acid Chemical compound OC(=O)CC(C(O)=O)S(O)(=O)=O ULUAUXLGCMPNKK-UHFFFAOYSA-N 0.000 description 1
- UCKMPCXJQFINFW-UHFFFAOYSA-N Sulphide Chemical compound [S-2] UCKMPCXJQFINFW-UHFFFAOYSA-N 0.000 description 1
- CEGOLXSVJUTHNZ-UHFFFAOYSA-K aluminium tristearate Chemical compound [Al+3].CCCCCCCCCCCCCCCCCC([O-])=O.CCCCCCCCCCCCCCCCCC([O-])=O.CCCCCCCCCCCCCCCCCC([O-])=O CEGOLXSVJUTHNZ-UHFFFAOYSA-K 0.000 description 1
- SRSXLGNVWSONIS-UHFFFAOYSA-M benzenesulfonate Chemical compound [O-]S(=O)(=O)C1=CC=CC=C1 SRSXLGNVWSONIS-UHFFFAOYSA-M 0.000 description 1
- 229940077388 benzenesulfonate Drugs 0.000 description 1
- 229910052793 cadmium Inorganic materials 0.000 description 1
- BDOSMKKIYDKNTQ-UHFFFAOYSA-N cadmium atom Chemical compound [Cd] BDOSMKKIYDKNTQ-UHFFFAOYSA-N 0.000 description 1
- 229910052799 carbon Inorganic materials 0.000 description 1
- 230000015556 catabolic process Effects 0.000 description 1
- 239000013058 crude material Substances 0.000 description 1
- 230000006735 deficit Effects 0.000 description 1
- 238000006731 degradation reaction Methods 0.000 description 1
- YRIUSKIDOIARQF-UHFFFAOYSA-N dodecyl benzenesulfonate Chemical compound CCCCCCCCCCCCOS(=O)(=O)C1=CC=CC=C1 YRIUSKIDOIARQF-UHFFFAOYSA-N 0.000 description 1
- 125000003438 dodecyl group Chemical group [H]C([H])([H])C([H])([H])C([H])([H])C([H])([H])C([H])([H])C([H])([H])C([H])([H])C([H])([H])C([H])([H])C([H])([H])C([H])([H])C([H])([H])* 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 239000004615 ingredient Substances 0.000 description 1
- 239000007791 liquid phase Substances 0.000 description 1
- 230000007246 mechanism Effects 0.000 description 1
- 239000000155 melt Substances 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 239000012071 phase Substances 0.000 description 1
- 239000000843 powder Substances 0.000 description 1
- 238000001556 precipitation Methods 0.000 description 1
- 239000011369 resultant mixture Substances 0.000 description 1
- 229920006395 saturated elastomer Polymers 0.000 description 1
- 239000012047 saturated solution Substances 0.000 description 1
- 229910052711 selenium Inorganic materials 0.000 description 1
- 239000011669 selenium Substances 0.000 description 1
- UMEWSJNRBXKWKZ-UHFFFAOYSA-M sodium;1,4-dioxo-1,4-dipentoxybutane-2-sulfonate Chemical compound [Na+].CCCCCOC(=O)CC(S([O-])(=O)=O)C(=O)OCCCCC UMEWSJNRBXKWKZ-UHFFFAOYSA-M 0.000 description 1
- 238000002798 spectrophotometry method Methods 0.000 description 1
- 238000003756 stirring Methods 0.000 description 1
- 238000005292 vacuum distillation Methods 0.000 description 1
Classifications
-
- G—PHYSICS
- G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
- G03G—ELECTROGRAPHY; ELECTROPHOTOGRAPHY; MAGNETOGRAPHY
- G03G13/00—Electrographic processes using a charge pattern
- G03G13/06—Developing
- G03G13/10—Developing using a liquid developer, e.g. liquid suspension
-
- G—PHYSICS
- G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
- G03G—ELECTROGRAPHY; ELECTROPHOTOGRAPHY; MAGNETOGRAPHY
- G03G9/00—Developers
- G03G9/08—Developers with toner particles
- G03G9/12—Developers with toner particles in liquid developer mixtures
- G03G9/135—Developers with toner particles in liquid developer mixtures characterised by stabiliser or charge-controlling agents
- G03G9/1355—Ionic, organic compounds
Landscapes
- Physics & Mathematics (AREA)
- General Physics & Mathematics (AREA)
- Liquid Developers In Electrophotography (AREA)
- Wet Developing In Electrophotography (AREA)
Abstract
A self-replenishing liquid developer system for an electrostatic imaging system including an insulating non-polar carrier li-quid. toner particles dispersed in the carrier liquid, at least one charge director compound having a limited solubility in the carrier liquid and dissolved therein at its saturation concentration and excess ofthe at least one charge director compound comprised in a solid phase and being in equilibrium contact with the carrier liquid.
Description
~rO90/1089~ PCT/Nl90J~002~
,- ~047675 1LIQ~ID ~EVE~PER 8YRTEH~ ~IT~ 8ELF-~EPLENI~H~NT
2OF B~R COND~CTIVITY
4This invention relates to the field of electrostatic imaging, ~nd ~ore particularly to a liguid 6 developer system having improved properties.
8 In the art of electrostatic photocopying cr photo 9 printing, a latent electrostatic image is generally produced ~y first providing a photoconductive imaging-s~rface with a 11 uniform electrostatic charge, e.g. by exposing the imaging 12 surface to a charge corona. The uniform electrostatic 13 charge is then selectively discharged ~y exposing it to a 14 modulated beam of light corresponding, e.g., to an optical image of ~n original to be copied, there~y forming an 16 electrostatic charge pattern on the photoconductive imaging 17 surface, i.e. a latent electrostatic image. Depending on 18 the nature of the photoconductive ~urface, the latent image l9 may have either a positive charge te.g. on a selenium photoconductor) or a negative charge (e.g. on a cadmium 21 sulfide photoconductor). The latent electrostatic image can 22 then be developed by applying to it oppositely charged 23 pigmented toner particles, which adhere to the undischarged 24 "print" portions of the photoconductive surface to form a toner image which is sub seguently transferred by ~arious 26 techniques to a copy sheet (e.g. paper).
27 In liquid-developed electrostatic imaging, the toner 28 particles are generally dispersed in an insulating non-polar 29 liquid carrier, generally an aliphatic hydrocarbon fraction, which generally has a high-volume resistivity above 109 ohm 31 cm, a dielectric constant below 3.0 and a low vapor pressure 32 (less then 10 torr. at 25-C). ~he liquid developer system 33 further comprises so-called charge directors, i.e. compounds 34 capable of imparting to the toner particles an electrical charge of the desired polarity and uniform magnitude so that 36 the particles may ~e electrophoretically deposited on the 37 ph~toconductive surface to form a toner image. These charge 38 director compounds are qenerally ionic or zwitterionic A
CA 0204767~ 1997-07-21 -~'O 90/10894 ~ u 4 ~ 6 7 5 PCr/~L90/0002~
1 compounds which are soluble in the non polar carrier liquid.
,- ~047675 1LIQ~ID ~EVE~PER 8YRTEH~ ~IT~ 8ELF-~EPLENI~H~NT
2OF B~R COND~CTIVITY
4This invention relates to the field of electrostatic imaging, ~nd ~ore particularly to a liguid 6 developer system having improved properties.
8 In the art of electrostatic photocopying cr photo 9 printing, a latent electrostatic image is generally produced ~y first providing a photoconductive imaging-s~rface with a 11 uniform electrostatic charge, e.g. by exposing the imaging 12 surface to a charge corona. The uniform electrostatic 13 charge is then selectively discharged ~y exposing it to a 14 modulated beam of light corresponding, e.g., to an optical image of ~n original to be copied, there~y forming an 16 electrostatic charge pattern on the photoconductive imaging 17 surface, i.e. a latent electrostatic image. Depending on 18 the nature of the photoconductive ~urface, the latent image l9 may have either a positive charge te.g. on a selenium photoconductor) or a negative charge (e.g. on a cadmium 21 sulfide photoconductor). The latent electrostatic image can 22 then be developed by applying to it oppositely charged 23 pigmented toner particles, which adhere to the undischarged 24 "print" portions of the photoconductive surface to form a toner image which is sub seguently transferred by ~arious 26 techniques to a copy sheet (e.g. paper).
27 In liquid-developed electrostatic imaging, the toner 28 particles are generally dispersed in an insulating non-polar 29 liquid carrier, generally an aliphatic hydrocarbon fraction, which generally has a high-volume resistivity above 109 ohm 31 cm, a dielectric constant below 3.0 and a low vapor pressure 32 (less then 10 torr. at 25-C). ~he liquid developer system 33 further comprises so-called charge directors, i.e. compounds 34 capable of imparting to the toner particles an electrical charge of the desired polarity and uniform magnitude so that 36 the particles may ~e electrophoretically deposited on the 37 ph~toconductive surface to form a toner image. These charge 38 director compounds are qenerally ionic or zwitterionic A
CA 0204767~ 1997-07-21 -~'O 90/10894 ~ u 4 ~ 6 7 5 PCr/~L90/0002~
1 compounds which are soluble in the non polar carrier liquid.
2 This desired charging is achieved by providing a constant 3 optimum concentration of charge director compound in the 4 carrier liguid, which concentration is usually determined so as to achieve the highest copy quality for the particular 6 application.
7 Stable electrical characteristics of the liquid 8 developer, in particular its bulk conductivity, are crucial 9 to achieve high quality imaging, particularly when a large number of impressions are to be produced without changing 11 the liquid developer system. A major factor determining the 12 electrical characteristics of the li~uid developer and 13 affecting the electrophoretic developing process of the 14 toner particles, is the concentration of the charge director in the carrier liquid. Thus, one of the major problems 16 arising in Iiquid-developed electrostatic imaging is the 17 variation in the charge director concentration and it is 18 believed that many low quality copies are a result of charge 19 director imbalance in the liquid developer system.
The application of liquid developer to the 21 photoconductive surface clearly depletes the overall amount 22 of liquid developer in the reservoir of an electrocopying or 23 electroprinting machine of this type. In practice, the 24 liquid reservoir is continuously replenished, as necessary, by addition of two liquids from two separate sources, the 26 one providing carrier li~uid and the other - a concentrated 27 dispersion of toner particles in the carrier liquid. This 28 is necessary in order to maintain in the carrier liquid in 29 the reservoir a relatively constant concentration of toner particles, because the total amounts of carrier liquid and 31 toner particles utilised per electrocopy vary as a function 32 of the proportional area of the printed portions of the 33 latent image on the photoconductive surface. An original 34 having a large proportion of printed area will cause a greater depletion of toner particles in the liquid developer 36 reservoir, as compared to an original with a small 37 proportion of printed area. Thus, in accordan~e with the 38 aforementioned practice, the rate of replenishment of CA 0 2 0 47 6 7 ~ ~9~74~~ -b 1 carrier liquid is controlled by monitoring the overall 2 amount or level of liquid developer in the reservoir, 3 whereas the rate of replenishment of toner particles (in the 4 form of a concentrated dispersion in carrier liquid) is controlled by monitoring the concentration of toner 6 particles in the liquid developer in the reservoir. An 7 optical float can combine both these functions, i.e. can be 8 utilized to monitor both the overall amount of liquid 9 developer in the reservoir and the toner particle concentration therein.
11 The amount of charge director in the liquid developer 12 reservoir must also be replenished, since the charge 13 director is also depleted together with the carrier liquid 14 and the toner particles. In existing liquid-developed electrostatic imaging machines the charge director is 16 replenished by adding it with the carrier liquid 17 replenishment or with the concentrated toner dispersion. As 18 explained hereinbelow, this results in charge director 19 imbalance in the liquid developer system with consequent impairment of the quality of the copies.
21 As discussed above, the amount of toner particles 22 utilized per electrocopy varies in proportion to the 23 relative printed area of the image. Thus, a large number of 24 so-called "white" copies (i.e. originals with small printed areas) will result in very small depletion of toner 26 particles whereas the amount of carrier liquid depleted will 27 be comparatively large. This amount of carrier liquid will 28 be replenished and, in machines designed for adding the 29 charge director only with the replenished carrier liquid, this will result in an increase of the concentration of 31 charge director relative to the toner concentration. It can 32 easily be seen that an opposite result will be observed in a 33 photocopier machine designed so that the charge director is 34 replenished together with the concentrated toner suspension only. In such machines a large number of ~white" copies 36 will cause a decrease in the concentration of charge 37 director in the liquid developer system.
38 Similarly, a large number of "black~' copies (i.e.
WO90/10894 PCT~L90/0002~
~ 4 ~ ~4 7b75 1 original~ with l~rge printed areas) will czuse a degradation 2 of -copy quality in-opposite directions to the above. In 3 ~achines wherein charge director is added with the carrier 4 liguid only, a large number of black copies will reduce the concentration of charge director in the liguid developer, 6 resulting in degraded copies. Against t~is, in ~achines 7 where charge director is ~dded to the reservoir with the 8 concentrated toner suspension only, its concentration in the 9 liguid developer will be increased by ~ larger num~er of black copies, resulting in lighter than optimal ~opies.
11 A possible solution to the above problem of charge 12 dire~tor imbalance in the liguid developer would be to 13 monitor separately the concentration of the charge director 14 and replenish it separately from a ~eparate source. This solution, however, is uneconomic, because it would involve 16 the cost and complexity of providing additional measurement 17 devices and replenishment mechanism. ~t follows that a 18 simpler and more feasible solution to the problem is needed.
19 It is an object of the present invention to provide a solution to the problem of charge director imbalance in 21 liguid developer systems, thereby to maintain a constant 22 high-quality of copies in electrostatic imaging processes, 23 independent of the "print" proportions of the originals.
24 Other objects and advantages of the present invention will become clear from the following description of the 26 invention.
28 The above object is achieved by the present invention 29 which, in accordance with one aspect thereof, provides a self-replenishing liguid developer system for use in 31 electrostatic imaging, which system comprises:
32 (a) an insulating non-polar carrier liguid;
33 (b) toner particles dispersed in said carrier liguid:
34 (c) at least one charge director compound having a limited solubility in said carrier liquid and dissolved 36 therein at its saturation concentration; and 37 (c) excess of said at least one charge director 38 compound co~iprised in a solid phase and being in equilibrium CA 0204767~ 1997-07-21 0 90~10894 2 0 1 7 6 7 5 PCr/~L90/0002~
1 contact with said carrier liquid.
2 The present invention is based on the concept of using 3 a charge director compound which has a limited low 4 solubility in the carrier liquid, such that the saturation concentration of the charge director in the carrier liquid 6 is at a proper concentration as to bring about the 7 electrical charging of the toner particles, to disperse them 8 and to maintain them at the desired degree of dispersion.
9 When such a saturated solution of charge director in the carrier liquid is maintained in contact with a solid phase 11 comprising or consisting of a considerable excess of the 12 charge director compound, this solid phase will serve as a 13 reservoir for the charge director compound. Whenever the 14 concentration of this charge director in the liquid phase, i.e. in the carrier liquid in contact with the solid phase, 16 falls below its saturation concentration value, it will be 17 rapidly equilibrated with the excess charge director in the 18 solid phase so that the saturation concentration of the 19 charge director in the carrier liquid is constantly and automatically ~aintained. As shown in the following, non-21 limiting examples, suitable charge director-carrier liquid-22 toner systems can be found which have the desired 23 characteristics.
24 In accordance with one embodiment of the present invention, it is the toner particles themselves which serve 26 as the solid phase comprising the excess charge director 27 compound. To this end, from about 5 to about 10% by weight 28 of charge director compound, based on the total weight of 29 the imaqing ~,aterial, are milled together with the remaining ingredients of the imaging material to form the toner 31 particles.
32 In accordance with this embodiment the concentration of 33 the charge director compound is continuously maintained by 34 natural and rapid equilibration between the charge director in solution in the carrier liquid and the excess charge 36 director comprised in the toner particles. ~hen, for 37 example, a large number of white copies are made, resulting 38 in a replenishment of pure carrier liquid thereby lowering CA 0204767~ 1997-07-21 '~'0 90/10894 2 0 7 6 7 a PCI/NL90/0002~
1 the concentration of charge director in the liquid developer, 2 some charge director compound will diffuse from the solid 3 -phase, i.e. from within the toner particles, into the 4 carrier liquid until dynamic equilibrium is reached when the concentration of charge director in the carrier liquid 6 reaches its saturation value. In the opposite case, where a 7 large number of "black" copies are made, consuming a 8 relatively high proportion of toner particles as compared to 9 the consumed carrier liquid, the resultant replenishment of concentrated suspension of toner particles in carrier liquid ll into the reservoir, would not affect the concentration of 12 charge director because the added carrier liquid in said 13 concentrated suspension will already be saturated with the 14 charge director compound owing to the presence of excess of that compound in the toner particles in that concentrated 16 suspension.
17 In accordance with an alternative embodiment of the 18 present invention, the excess of charge director compound, 19 preferably in the form of a finely dispersed powder, is contained in a container, at least a portion of the walls of 21 which being made of a porous material which is permeable to 22 the carrier liquid but does not permit the passage 23 therethrough of the particulate solid charge director 24 compound. Such container will be wholly or partially immersed in the reservoir of liquid developer so as to be in 26 direct contact therewith. A suitable container may be, for 27 example a closed bag made of thin porous sheet material, 28 e.g. filter paper or the like. In this embodiment of the 29 invention, the liquid developer is always in direct equilibrium contact with the excess charge director in solid 31 form, thereby achieving a constant saturation concentration 32 of charge director in the liquid developer.
33 The invention will be further described by the follow-34 ing, non-limiting examples, all of which relate to negative-working liquid developer systems, i.e. those in which the 36 toner particles are negatively charged. It should be 37 understood, however, that the invention is not limited to 38 such negative-working liquid developers, but is rather ~'O 90/10894 2 0 ~ 7 6 7 S PC~/NL90/0002~
~ equally applicable to positive-working liquid developer 2 systems. It should also be understood that the invention is 3 not limited to the specific toner of Preparation 1 herein 4 nor to the specific carrier liquids exemplified, but rather extends to all modifications falling within the scope of the 6 claims.
8 Preparation of Black Imaging material 9 Black imaging material which is used in Examples 1 to 5 hereinbelow is prepared as follows:
11 10 parts by weight of Elvax 5720 tE.I. Du Pont), and 5 12 parts by weight of Isopar L (Exxon) are mixed at low speed 13 in a jacketed double planetary mixer connected to an oil 14 heating unit, for 1 hour, the heating unit being set at 130-C.
16 A mixture of 2.5 parts by weight of Mogul L carbon 17 black (Cabot) and 5 parts by weight of Isopar L is then 18 added to the mix in the double planetary mixer and the 19 resultant mixture is further mixed for 1 hour at high speed.
20 parts by weight of Isopar L preheated to 110-C are added 2~ to the mixer and mixing is continued at high speed for 22 hour.
23 The heating unit is then disconnected and mixing is 24 continued until the temperature of the mixture drops to 40 C.
27 Calcium laurylbenzenesulfonate in toner particles 28 Calcium laurylbenzenesulfonate was prepared from its 29 68 - 70% solution in xylol and isobutanol commercially available under the name Emcol P-1020 (Witco), by one of the 31 following methods:
32 1) Emcol P-1020 is subjected to vacuum distillation 33 at 170 C. The solid residue is allowed to equilibrate with 34 air moisture and dissolved in Isopar H at the desired concentration.
36 2) The Emcol P-1020 is diluted with Isopar H to a 10%
37 content of non volatile solids (n.v.s.) and the obtained 38 solution is allowed to stand at room temperature whereupon a ~'O 90/10894 2 0 4 7 6 7 ~ PCI/NL90/0002~
. - 8 -1 yellow ~eA~ t is formed followed within 30 - 35 days by 2 precipitation -Qf a white material which is separa~ed and 3 dissolved in Isopar H at the desired concentration.
4 The crude material thus obtained is washed repeatedly with Isopar H with stirring until a constant conductance in 6 the supernatant Isopar H solution is reached. The resultant 7 solid residue was dried.
8 The solubility of calcium laurylbenzensulfonate in 9 Isopar H was determined ~y U.V. spectrophotometry and found to be 0.069% by weight.
11 PreParation of the liquid developer.
12 One part by weight of the solid dry calcium lauryl 13 benzenesulfonate was co-melted with 9 parts by weight of 14 black imaging material at 130-C. The melt was cooled and 100 g thereof and 120 g of Isopar L were milled together for 16 19 hours in an attritor to obtain a dispersion of particles 17 with an average diameter of about 2~. The attrited material 18 obtained was washed several times with Isopar H and then 19 dispersed in Isopar H at a content of 1% n.v.s. The conductance of the toner was 3 pmho/cm.
21 The performance of the developer was tested in a Savin 22 V-35 photocopier machine using both Savin 2200+ and Printers 23 Stock copy sheets. The results obtained are summarised in 24 the following Table 1.
27 Substrate Solid Fixing Bleed 28 Area Density through 29 (SAD) (SAD) 31 Savin 2200 ~ 1.51 good 0.15 33 Printers 34 Stock 1.67 good 0.09 37 ~odiu~ laurylbenzenesulfonate in toner 38 The title material was purchased from Fluka and used ~090/10894 2 0 4 7 6 75 PCT/NL90/0002~
_ g _ ~ without further treatment, after being left to equilibrate 2 with air moisture. The material was repeatedly washed with 3 Isopar H until a constant conductance of the supernatant 4 solution was reached.
The solubility of sodium laurylbenzenesulfonate in 6 Isopar H was determined spectrophotometrically to be 0.027%
7 by weight.
8 Preparation of the liquid developer 9 One part of weight of-sodium laurylbenzenesulfonate was co-melted with 9 parts by weight of black imaging material.
11 100 g of the co-melt were mixed with 120 g of Isopar G and 12 attrited as described in Example 1 to give an average 13 particle size of about 1.9~. The final developer, after 14 washing, had a conductance of 5.5 pmho/cm at a concentration of 1% n.v.s. in Isopar G. It was placed in the developer 16 bath of a Savin 870 photocopier and the performance on 17 various substrates was tested. The results are shown in the 18 following Table 2.
21 Substrate S.A.D. Transfer 22 efficiency %
24 Gilbert Bond 1.33 72 Printers Stock 1.64 87 28 ~odium diamyl sulfosuccinate in toner 29 The title material is commercially available under the name Aerosol AY (Cyanamide). It was used without further 31 treatment, except for equilibration with the air humidity 32 and successive washing with Isopar H to constant conductance 33 (about 1-2 pmho/cm).
34 Preparation of the developer 5 parts of sodium diamyl sulfosuccinate and one part of 36 aluminium stearate were co-melted with 44 parts by weight of 37 black imaging material in accordance with the procedure 38 described in Example 1. lOO g of the co-melt were added to - - ~
090/10894 2 0 ~ 7 6 7 5 PCT/NL90/0002~
1 120 g of Isopar H and milled for 19 hours as described in 2 Example l. The milled'toner thus obtained was washed several 3 times with Isopar and diluted with Isopar G to a 1% n.v.s.
4 content of toner.
The obtained dispersion was placed in the developer 6 bath of a Savin 870 photocopier and the performance tested 7 on various substrates. The results are summarised in the 8 following Table 3.
g ~AB~E 3 11 Substrate S.A.D. Transfer 12 Efficiency (%) 14 Savin 2200 ~ 1.32 84 15 Gilbert Bond 1.61 63 17 EXAMPLB ~
18 Calcium laurYlberlzenesulfonate in filter paper baq.
19 The material obtained as described in Example 1 was placed in a bag prepared from folded Whatman MN filter 21 paper, and the bag was immersed in a liquid developer and 22 the conductance of the liquid developer measured. From time 23 to time the bag was removed from the li~uid developer which 24 was centrifuged to remove the supernatant and the resultant toner particles were redispersed in pure Isopar H. There-26 after, the filter paper bag containing the charge director 27 compound was re-installed and after several hours of stir-28 ring the conductivity of the liquid developer was measured 29 again. To eliminate effects related to possible permeation of the charged toner particles through the filter paper, the 31 conductance values obtained were compared with those of an 32 identical control bag immersed in pure Isopar H.
33 It was found that the conductance of the liquid 34 developer surrounding the bag reached a time-independent 3S steady-state value of about 4 pmho/cm at a toner concentra-36 tion of 1% n.v.s. The same conductance value was observed 37 when the bag was removed from the toner suspension and 38 immersed in pure isopar H.
~'090/10894 2 0 ~ 7 6 7 ~ PCT/NL90/0002~
1 Measurements in a test plating cell showed negative 2 plating with the above described liquid developer system.
~ ~XAMP~E S
4 When the procedure of Example 4 was repeated with sodium laurylbenzenesulfonate (in Isopar H), calcium di-6 isobutyl sulfosuccinate (in Isopar G) and ~odium diamyl 7 sulfosuccinate (in Isopar H using a bag made from Whatman 8 No. 2 filter paper), similar results as in Example 4 were 9 obtained.
In all the above cases, a steady-state conductance was 11 reached and significant charge transport followed by 12 negative plating were observed in the test cell. In the 13 case of calcium diisobutyl sulfosuccinate a markedly low 14 conductance of 0.5-2 pmho/cm was ~easured (at toner con-lS centration of 1~ n.v.s.), but this did not affect the pro-16 nounced charge transport and the negative plating in the 17 cell.
7 Stable electrical characteristics of the liquid 8 developer, in particular its bulk conductivity, are crucial 9 to achieve high quality imaging, particularly when a large number of impressions are to be produced without changing 11 the liquid developer system. A major factor determining the 12 electrical characteristics of the li~uid developer and 13 affecting the electrophoretic developing process of the 14 toner particles, is the concentration of the charge director in the carrier liquid. Thus, one of the major problems 16 arising in Iiquid-developed electrostatic imaging is the 17 variation in the charge director concentration and it is 18 believed that many low quality copies are a result of charge 19 director imbalance in the liquid developer system.
The application of liquid developer to the 21 photoconductive surface clearly depletes the overall amount 22 of liquid developer in the reservoir of an electrocopying or 23 electroprinting machine of this type. In practice, the 24 liquid reservoir is continuously replenished, as necessary, by addition of two liquids from two separate sources, the 26 one providing carrier li~uid and the other - a concentrated 27 dispersion of toner particles in the carrier liquid. This 28 is necessary in order to maintain in the carrier liquid in 29 the reservoir a relatively constant concentration of toner particles, because the total amounts of carrier liquid and 31 toner particles utilised per electrocopy vary as a function 32 of the proportional area of the printed portions of the 33 latent image on the photoconductive surface. An original 34 having a large proportion of printed area will cause a greater depletion of toner particles in the liquid developer 36 reservoir, as compared to an original with a small 37 proportion of printed area. Thus, in accordan~e with the 38 aforementioned practice, the rate of replenishment of CA 0 2 0 47 6 7 ~ ~9~74~~ -b 1 carrier liquid is controlled by monitoring the overall 2 amount or level of liquid developer in the reservoir, 3 whereas the rate of replenishment of toner particles (in the 4 form of a concentrated dispersion in carrier liquid) is controlled by monitoring the concentration of toner 6 particles in the liquid developer in the reservoir. An 7 optical float can combine both these functions, i.e. can be 8 utilized to monitor both the overall amount of liquid 9 developer in the reservoir and the toner particle concentration therein.
11 The amount of charge director in the liquid developer 12 reservoir must also be replenished, since the charge 13 director is also depleted together with the carrier liquid 14 and the toner particles. In existing liquid-developed electrostatic imaging machines the charge director is 16 replenished by adding it with the carrier liquid 17 replenishment or with the concentrated toner dispersion. As 18 explained hereinbelow, this results in charge director 19 imbalance in the liquid developer system with consequent impairment of the quality of the copies.
21 As discussed above, the amount of toner particles 22 utilized per electrocopy varies in proportion to the 23 relative printed area of the image. Thus, a large number of 24 so-called "white" copies (i.e. originals with small printed areas) will result in very small depletion of toner 26 particles whereas the amount of carrier liquid depleted will 27 be comparatively large. This amount of carrier liquid will 28 be replenished and, in machines designed for adding the 29 charge director only with the replenished carrier liquid, this will result in an increase of the concentration of 31 charge director relative to the toner concentration. It can 32 easily be seen that an opposite result will be observed in a 33 photocopier machine designed so that the charge director is 34 replenished together with the concentrated toner suspension only. In such machines a large number of ~white" copies 36 will cause a decrease in the concentration of charge 37 director in the liquid developer system.
38 Similarly, a large number of "black~' copies (i.e.
WO90/10894 PCT~L90/0002~
~ 4 ~ ~4 7b75 1 original~ with l~rge printed areas) will czuse a degradation 2 of -copy quality in-opposite directions to the above. In 3 ~achines wherein charge director is added with the carrier 4 liguid only, a large number of black copies will reduce the concentration of charge director in the liguid developer, 6 resulting in degraded copies. Against t~is, in ~achines 7 where charge director is ~dded to the reservoir with the 8 concentrated toner suspension only, its concentration in the 9 liguid developer will be increased by ~ larger num~er of black copies, resulting in lighter than optimal ~opies.
11 A possible solution to the above problem of charge 12 dire~tor imbalance in the liguid developer would be to 13 monitor separately the concentration of the charge director 14 and replenish it separately from a ~eparate source. This solution, however, is uneconomic, because it would involve 16 the cost and complexity of providing additional measurement 17 devices and replenishment mechanism. ~t follows that a 18 simpler and more feasible solution to the problem is needed.
19 It is an object of the present invention to provide a solution to the problem of charge director imbalance in 21 liguid developer systems, thereby to maintain a constant 22 high-quality of copies in electrostatic imaging processes, 23 independent of the "print" proportions of the originals.
24 Other objects and advantages of the present invention will become clear from the following description of the 26 invention.
28 The above object is achieved by the present invention 29 which, in accordance with one aspect thereof, provides a self-replenishing liguid developer system for use in 31 electrostatic imaging, which system comprises:
32 (a) an insulating non-polar carrier liguid;
33 (b) toner particles dispersed in said carrier liguid:
34 (c) at least one charge director compound having a limited solubility in said carrier liquid and dissolved 36 therein at its saturation concentration; and 37 (c) excess of said at least one charge director 38 compound co~iprised in a solid phase and being in equilibrium CA 0204767~ 1997-07-21 0 90~10894 2 0 1 7 6 7 5 PCr/~L90/0002~
1 contact with said carrier liquid.
2 The present invention is based on the concept of using 3 a charge director compound which has a limited low 4 solubility in the carrier liquid, such that the saturation concentration of the charge director in the carrier liquid 6 is at a proper concentration as to bring about the 7 electrical charging of the toner particles, to disperse them 8 and to maintain them at the desired degree of dispersion.
9 When such a saturated solution of charge director in the carrier liquid is maintained in contact with a solid phase 11 comprising or consisting of a considerable excess of the 12 charge director compound, this solid phase will serve as a 13 reservoir for the charge director compound. Whenever the 14 concentration of this charge director in the liquid phase, i.e. in the carrier liquid in contact with the solid phase, 16 falls below its saturation concentration value, it will be 17 rapidly equilibrated with the excess charge director in the 18 solid phase so that the saturation concentration of the 19 charge director in the carrier liquid is constantly and automatically ~aintained. As shown in the following, non-21 limiting examples, suitable charge director-carrier liquid-22 toner systems can be found which have the desired 23 characteristics.
24 In accordance with one embodiment of the present invention, it is the toner particles themselves which serve 26 as the solid phase comprising the excess charge director 27 compound. To this end, from about 5 to about 10% by weight 28 of charge director compound, based on the total weight of 29 the imaqing ~,aterial, are milled together with the remaining ingredients of the imaging material to form the toner 31 particles.
32 In accordance with this embodiment the concentration of 33 the charge director compound is continuously maintained by 34 natural and rapid equilibration between the charge director in solution in the carrier liquid and the excess charge 36 director comprised in the toner particles. ~hen, for 37 example, a large number of white copies are made, resulting 38 in a replenishment of pure carrier liquid thereby lowering CA 0204767~ 1997-07-21 '~'0 90/10894 2 0 7 6 7 a PCI/NL90/0002~
1 the concentration of charge director in the liquid developer, 2 some charge director compound will diffuse from the solid 3 -phase, i.e. from within the toner particles, into the 4 carrier liquid until dynamic equilibrium is reached when the concentration of charge director in the carrier liquid 6 reaches its saturation value. In the opposite case, where a 7 large number of "black" copies are made, consuming a 8 relatively high proportion of toner particles as compared to 9 the consumed carrier liquid, the resultant replenishment of concentrated suspension of toner particles in carrier liquid ll into the reservoir, would not affect the concentration of 12 charge director because the added carrier liquid in said 13 concentrated suspension will already be saturated with the 14 charge director compound owing to the presence of excess of that compound in the toner particles in that concentrated 16 suspension.
17 In accordance with an alternative embodiment of the 18 present invention, the excess of charge director compound, 19 preferably in the form of a finely dispersed powder, is contained in a container, at least a portion of the walls of 21 which being made of a porous material which is permeable to 22 the carrier liquid but does not permit the passage 23 therethrough of the particulate solid charge director 24 compound. Such container will be wholly or partially immersed in the reservoir of liquid developer so as to be in 26 direct contact therewith. A suitable container may be, for 27 example a closed bag made of thin porous sheet material, 28 e.g. filter paper or the like. In this embodiment of the 29 invention, the liquid developer is always in direct equilibrium contact with the excess charge director in solid 31 form, thereby achieving a constant saturation concentration 32 of charge director in the liquid developer.
33 The invention will be further described by the follow-34 ing, non-limiting examples, all of which relate to negative-working liquid developer systems, i.e. those in which the 36 toner particles are negatively charged. It should be 37 understood, however, that the invention is not limited to 38 such negative-working liquid developers, but is rather ~'O 90/10894 2 0 ~ 7 6 7 S PC~/NL90/0002~
~ equally applicable to positive-working liquid developer 2 systems. It should also be understood that the invention is 3 not limited to the specific toner of Preparation 1 herein 4 nor to the specific carrier liquids exemplified, but rather extends to all modifications falling within the scope of the 6 claims.
8 Preparation of Black Imaging material 9 Black imaging material which is used in Examples 1 to 5 hereinbelow is prepared as follows:
11 10 parts by weight of Elvax 5720 tE.I. Du Pont), and 5 12 parts by weight of Isopar L (Exxon) are mixed at low speed 13 in a jacketed double planetary mixer connected to an oil 14 heating unit, for 1 hour, the heating unit being set at 130-C.
16 A mixture of 2.5 parts by weight of Mogul L carbon 17 black (Cabot) and 5 parts by weight of Isopar L is then 18 added to the mix in the double planetary mixer and the 19 resultant mixture is further mixed for 1 hour at high speed.
20 parts by weight of Isopar L preheated to 110-C are added 2~ to the mixer and mixing is continued at high speed for 22 hour.
23 The heating unit is then disconnected and mixing is 24 continued until the temperature of the mixture drops to 40 C.
27 Calcium laurylbenzenesulfonate in toner particles 28 Calcium laurylbenzenesulfonate was prepared from its 29 68 - 70% solution in xylol and isobutanol commercially available under the name Emcol P-1020 (Witco), by one of the 31 following methods:
32 1) Emcol P-1020 is subjected to vacuum distillation 33 at 170 C. The solid residue is allowed to equilibrate with 34 air moisture and dissolved in Isopar H at the desired concentration.
36 2) The Emcol P-1020 is diluted with Isopar H to a 10%
37 content of non volatile solids (n.v.s.) and the obtained 38 solution is allowed to stand at room temperature whereupon a ~'O 90/10894 2 0 4 7 6 7 ~ PCI/NL90/0002~
. - 8 -1 yellow ~eA~ t is formed followed within 30 - 35 days by 2 precipitation -Qf a white material which is separa~ed and 3 dissolved in Isopar H at the desired concentration.
4 The crude material thus obtained is washed repeatedly with Isopar H with stirring until a constant conductance in 6 the supernatant Isopar H solution is reached. The resultant 7 solid residue was dried.
8 The solubility of calcium laurylbenzensulfonate in 9 Isopar H was determined ~y U.V. spectrophotometry and found to be 0.069% by weight.
11 PreParation of the liquid developer.
12 One part by weight of the solid dry calcium lauryl 13 benzenesulfonate was co-melted with 9 parts by weight of 14 black imaging material at 130-C. The melt was cooled and 100 g thereof and 120 g of Isopar L were milled together for 16 19 hours in an attritor to obtain a dispersion of particles 17 with an average diameter of about 2~. The attrited material 18 obtained was washed several times with Isopar H and then 19 dispersed in Isopar H at a content of 1% n.v.s. The conductance of the toner was 3 pmho/cm.
21 The performance of the developer was tested in a Savin 22 V-35 photocopier machine using both Savin 2200+ and Printers 23 Stock copy sheets. The results obtained are summarised in 24 the following Table 1.
27 Substrate Solid Fixing Bleed 28 Area Density through 29 (SAD) (SAD) 31 Savin 2200 ~ 1.51 good 0.15 33 Printers 34 Stock 1.67 good 0.09 37 ~odiu~ laurylbenzenesulfonate in toner 38 The title material was purchased from Fluka and used ~090/10894 2 0 4 7 6 75 PCT/NL90/0002~
_ g _ ~ without further treatment, after being left to equilibrate 2 with air moisture. The material was repeatedly washed with 3 Isopar H until a constant conductance of the supernatant 4 solution was reached.
The solubility of sodium laurylbenzenesulfonate in 6 Isopar H was determined spectrophotometrically to be 0.027%
7 by weight.
8 Preparation of the liquid developer 9 One part of weight of-sodium laurylbenzenesulfonate was co-melted with 9 parts by weight of black imaging material.
11 100 g of the co-melt were mixed with 120 g of Isopar G and 12 attrited as described in Example 1 to give an average 13 particle size of about 1.9~. The final developer, after 14 washing, had a conductance of 5.5 pmho/cm at a concentration of 1% n.v.s. in Isopar G. It was placed in the developer 16 bath of a Savin 870 photocopier and the performance on 17 various substrates was tested. The results are shown in the 18 following Table 2.
21 Substrate S.A.D. Transfer 22 efficiency %
24 Gilbert Bond 1.33 72 Printers Stock 1.64 87 28 ~odium diamyl sulfosuccinate in toner 29 The title material is commercially available under the name Aerosol AY (Cyanamide). It was used without further 31 treatment, except for equilibration with the air humidity 32 and successive washing with Isopar H to constant conductance 33 (about 1-2 pmho/cm).
34 Preparation of the developer 5 parts of sodium diamyl sulfosuccinate and one part of 36 aluminium stearate were co-melted with 44 parts by weight of 37 black imaging material in accordance with the procedure 38 described in Example 1. lOO g of the co-melt were added to - - ~
090/10894 2 0 ~ 7 6 7 5 PCT/NL90/0002~
1 120 g of Isopar H and milled for 19 hours as described in 2 Example l. The milled'toner thus obtained was washed several 3 times with Isopar and diluted with Isopar G to a 1% n.v.s.
4 content of toner.
The obtained dispersion was placed in the developer 6 bath of a Savin 870 photocopier and the performance tested 7 on various substrates. The results are summarised in the 8 following Table 3.
g ~AB~E 3 11 Substrate S.A.D. Transfer 12 Efficiency (%) 14 Savin 2200 ~ 1.32 84 15 Gilbert Bond 1.61 63 17 EXAMPLB ~
18 Calcium laurYlberlzenesulfonate in filter paper baq.
19 The material obtained as described in Example 1 was placed in a bag prepared from folded Whatman MN filter 21 paper, and the bag was immersed in a liquid developer and 22 the conductance of the liquid developer measured. From time 23 to time the bag was removed from the li~uid developer which 24 was centrifuged to remove the supernatant and the resultant toner particles were redispersed in pure Isopar H. There-26 after, the filter paper bag containing the charge director 27 compound was re-installed and after several hours of stir-28 ring the conductivity of the liquid developer was measured 29 again. To eliminate effects related to possible permeation of the charged toner particles through the filter paper, the 31 conductance values obtained were compared with those of an 32 identical control bag immersed in pure Isopar H.
33 It was found that the conductance of the liquid 34 developer surrounding the bag reached a time-independent 3S steady-state value of about 4 pmho/cm at a toner concentra-36 tion of 1% n.v.s. The same conductance value was observed 37 when the bag was removed from the toner suspension and 38 immersed in pure isopar H.
~'090/10894 2 0 ~ 7 6 7 ~ PCT/NL90/0002~
1 Measurements in a test plating cell showed negative 2 plating with the above described liquid developer system.
~ ~XAMP~E S
4 When the procedure of Example 4 was repeated with sodium laurylbenzenesulfonate (in Isopar H), calcium di-6 isobutyl sulfosuccinate (in Isopar G) and ~odium diamyl 7 sulfosuccinate (in Isopar H using a bag made from Whatman 8 No. 2 filter paper), similar results as in Example 4 were 9 obtained.
In all the above cases, a steady-state conductance was 11 reached and significant charge transport followed by 12 negative plating were observed in the test cell. In the 13 case of calcium diisobutyl sulfosuccinate a markedly low 14 conductance of 0.5-2 pmho/cm was ~easured (at toner con-lS centration of 1~ n.v.s.), but this did not affect the pro-16 nounced charge transport and the negative plating in the 17 cell.
Claims (17)
1. A self-replenishing liquid developer system for an electrostatic imaging system comprising:
(a) an insulating non-polar carrier liquid;
(b) toner particles dispersed in said carrier liquid;
(c) at least one charge director compound having a limited solubility in said carrier liquid and dissolved therein at its saturation concentration; and (d) excess of said at least one charge director compound comprised in a solid phase and being in equilibrium contact with said carrier liquid.
(a) an insulating non-polar carrier liquid;
(b) toner particles dispersed in said carrier liquid;
(c) at least one charge director compound having a limited solubility in said carrier liquid and dissolved therein at its saturation concentration; and (d) excess of said at least one charge director compound comprised in a solid phase and being in equilibrium contact with said carrier liquid.
2. A liquid developer system according to claim 1 wherein said excess of charge director compound is comprised in said toner particles.
3. A liquid developer system according to claim 1 wherein said excess of charge director compound is in a finely dispersed solid form and is comprised in a container in contact with and permeable to said carrier liquid throughout at least a portion of the walls of the container.
4. A liquid developer system according to claim 3, wherein said container is a bag made of thin sheets of a porous material.
5. A liquid developer system according to claim 4, wherein said porous material is filter paper.
6. A liquid developer system according to any of claims 1-5, wherein said carrier liquid is a branched chain aliphatic hydrocarbon or a mixture of such hydrocarbons.
7. A liquid developer system according to any of claims 1-6, wherein said carrier liquid is an isoparaffinic hydrocarbon fraction having a boiling range above 155°C.
8. A liquid developer system according to any of claims 1-7, wherein said charge director compound is ionic or zwitterionic.
9. A liquid developer system according to claim 8, wherein said charge director compound is a metal soap.
10. A liquid developer system according to any of claims 1-9, wherein said charge director compound is capable of imparting a negative charge to the toner particles suspended in the carrier liquid.
11. A liquid developer system according to any of claims 1-10, wherein said charge director compound is calcium laurylbenzenesulfonate.
12. A liquid developer system according to any of claims 1-11, wherein said charge director compound is sodium laurylbenzenesulfonate.
13. A liquid developer system according to any of claims 1-12 wherein said charge director compound is sodium diamyl sulfosuccinate.
14. An electrostatic imaging process comprising the steps of:
(a) forming a latent electrostatic image on a surface;
(b) applying to said surface electrically charged toner particles from a liquid developer system according to any of the preceding claims to form a toner image on said surface; and (c) transferring the resulting toner image to a substrate.
(a) forming a latent electrostatic image on a surface;
(b) applying to said surface electrically charged toner particles from a liquid developer system according to any of the preceding claims to form a toner image on said surface; and (c) transferring the resulting toner image to a substrate.
15. An electrostatic imaging process comprising the steps of:
(a) electrostatically charging a photoconductive surface;
(b) exposing said photoconductive surface to an optical image thereby forming a latent electro static image on said photoconductive surface;
(c) applying to said photoconductive surface electrically charged toner particles from a liquid developer system according to any of claims 1-13 to form a toner image on said photoconductive surface; and (d) transferring the resulting toner image to a copy sheet substrate.
(a) electrostatically charging a photoconductive surface;
(b) exposing said photoconductive surface to an optical image thereby forming a latent electro static image on said photoconductive surface;
(c) applying to said photoconductive surface electrically charged toner particles from a liquid developer system according to any of claims 1-13 to form a toner image on said photoconductive surface; and (d) transferring the resulting toner image to a copy sheet substrate.
16. A method for developing a latent electrostatic image in a liquid-developed electrostatic imaging process which comprises the use of a liquid developer system according to any of claims 1-13.
17. A liquid-developed electrocopying or electroprinting apparatus comprising a self replenishing liquid developing system according to any of claims 1-13.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US31912689A | 1989-03-06 | 1989-03-06 | |
| US319,126 | 1989-03-06 |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CA2047675A1 CA2047675A1 (en) | 1990-09-07 |
| CA2047675C true CA2047675C (en) | 1998-08-11 |
Family
ID=23240964
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002047675A Expired - Fee Related CA2047675C (en) | 1989-03-06 | 1990-03-05 | Liquid developer systems with self-replenishment of bulk conductivity |
Country Status (5)
| Country | Link |
|---|---|
| EP (1) | EP0462174B1 (en) |
| CA (1) | CA2047675C (en) |
| DE (1) | DE69012987T2 (en) |
| HK (1) | HK137695A (en) |
| WO (1) | WO1990010894A1 (en) |
Families Citing this family (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US7070900B2 (en) * | 2003-09-30 | 2006-07-04 | Samsung Electronics Company | Adjuvants for positively charged toners |
| US7118842B2 (en) * | 2003-09-30 | 2006-10-10 | Samsung Electronics Company | Charge adjuvant delivery system and methods |
| US7144671B2 (en) * | 2003-09-30 | 2006-12-05 | Samsung Electronics Company | Adjuvants for negatively charged toners |
Family Cites Families (10)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3669886A (en) * | 1968-09-11 | 1972-06-13 | Hunt Chem Corp Philip A | Liquid developer for electrostatography |
| US4003500A (en) * | 1970-12-31 | 1977-01-18 | Hoechst Aktiengesellschaft | Metering device |
| US4193683A (en) * | 1978-08-21 | 1980-03-18 | Langner Fred R | Method and apparatus for filtering developing liquid in a photocopier |
| WO1987005128A1 (en) * | 1986-02-14 | 1987-08-27 | Savin Corporation | Liquid developer charge director control |
| US4707429A (en) * | 1986-04-30 | 1987-11-17 | E. I. Du Pont De Nemours And Company | Metallic soap as adjuvant for electrostatic liquid developer |
| DE3725002C2 (en) * | 1986-07-28 | 1998-04-30 | Ricoh Kk | Development refill material for an electrostatic copier |
| US4656966A (en) * | 1986-08-04 | 1987-04-14 | Eastman Kodak Company | Method and apparatus for developing electrographic images uses molecular sieve zeolite |
| US4785327A (en) * | 1987-09-03 | 1988-11-15 | Savin Corporation | Pneumatic charge director dispensing apparatus |
| US4812382A (en) * | 1987-12-17 | 1989-03-14 | Eastman Kodak Company | Electrostatographic toners and developers containing new charge-control agents |
| US4869991A (en) * | 1988-03-24 | 1989-09-26 | Olin Hunt Specialty Products Inc. | Charge director composition for liquid toner formulations |
-
1990
- 1990-03-05 EP EP90904452A patent/EP0462174B1/en not_active Expired - Lifetime
- 1990-03-05 CA CA002047675A patent/CA2047675C/en not_active Expired - Fee Related
- 1990-03-05 DE DE69012987T patent/DE69012987T2/en not_active Expired - Fee Related
- 1990-03-05 WO PCT/NL1990/000025 patent/WO1990010894A1/en active IP Right Grant
-
1995
- 1995-08-31 HK HK137695A patent/HK137695A/en not_active IP Right Cessation
Also Published As
| Publication number | Publication date |
|---|---|
| DE69012987D1 (en) | 1994-11-03 |
| EP0462174A1 (en) | 1991-12-27 |
| DE69012987T2 (en) | 1995-05-04 |
| HK137695A (en) | 1995-09-08 |
| CA2047675A1 (en) | 1990-09-07 |
| EP0462174B1 (en) | 1994-09-28 |
| WO1990010894A1 (en) | 1990-09-20 |
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| EEER | Examination request | ||
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Effective date: 20060306 |