US 3619279 A
Description (OCR text may contain errors)
United States Patent Herbert N. Johnston Columbus;
Nicholas D. Gallagher, Troy, both of Ohio 842,356
July 16, 1969 Division 01 Ser. No. 520,872 Jan. 17, 1966, Pat. No. 3,493,412
Nov. 9, 1971 Xerox Corporation Rochester, N.Y.
 lnventors 211 Appl. No. 22 Filed  Patented 73] Assignee  TONER RECEIVING MEMBER  References Cited UNlTED STATES PATENTS 1,783,442 12/1930 Mayer et a1 117/167 X 2,462,029 2/1949 Perry 117/155 X 2,833,671 5/1958 Funk et a1 117/79X 2,875,168 2/1959 Smith etal 260/314 2,885,306 5/1959 Rigterink et a1. 117/122 2,914,436 11/1959 Nakiclny 117/144 X 3,130,064 4/1964 lnsalaco 117/17.5 3,260,612 7/1966 Dulmage et a1.... 117/33 X 3,336,152 8/1967 Garden 117/121 X Primary Examiner- William D. Martin Assistant ExaminerM. R. Lusighan An0rneys.1ames J. Ralabate, Albert A. Mahassel and Samuel E. Mott ABSTRACT: A toner receiving member having available at an external surface a solid crystalline plasticizer to reduce the fuglycol dibenzoate may be available on the surface of paper.
TONER RECEIVING MEMBER This application is a division of copending application Ser. No. 520,872, filed Jan. 17, 1966, now U.S. Pat. No. 3,493,412.
This invention relates in general to imaging systems, and more particularly, to improved receiving surfaces, their manufacture and use.
The formation and development of images on the surface of photoconductive materials by electrostatic means is well known. The basic xerographic process as taught by C. F. Carlson in U.S. Pat. No. 2,297,691 involves placing a uniform electrostatic charge on a photoconductive insulating layer, exposing the layer to a light and shadow image to dissipate the charge on the areas of the layer exposed to the light and developing the resulting latent electrostatic image by depositing on the image a finely divided electroscopic material referred to in the art as toner." The toner will normally be attracted to those areas of the layer which retain a charge, thereby forming a toner image corresponding to the latent electrostatic image. This powder may then be transferred to a receiving surface such as paper. The transferred image may subsequently be permanently affixed to the support surface as by heat. Instead of latent image formation by uniformly charging the photoconductive layer and then exposing the layer to a light and shadow image, one may form the latent image by directly charging the layer in image configuration. Several methods are known for applying the electroscopic particles to the latent electrostatic image to be developed. These methods include cascade" development, magnetic brush" development, powder cloud" development and liquid development as described in U.S. Pat. Nos. 2,618,552; 2,874,063; 2,221,776; and 2,891,911 respectively. The processes mentioned above together with numerous variations are well known to the art through various patents and publications and through the widespread availability and utilization of electrostatic imaging equipment.
A variety of types of finely divided electroscopic powders are disclosed in the Carlson patent. However, as the art of electrostatic copying has progressed, a variety of pigmented thermoplastic resins have evolved as the preferred toner materials when heat is employed to fuse the thermoplastic toner image to a support surface. While ordinarily capable of producing excellent quality images, these toner materials possess serious deficiencies in certain areas. When the toner is to be fused onto an inflammable surface such as paper, the toner resin should have a fusing temperature below the thermal degradation temperature of the paper. Upon heating to the discoloration temperature or flame point of some papers, resinous toners having high fusing temperatures often do not become sufficiently fluid to penetrate and adhere to the paper. The resulting powdery and incompletely fused images are easily removed by rubbing. On the other hand, toner resins having low fusing temperatures are usually tacky at ordinarily encountered ambient temperatures and fon'n undesirable agglomerates during storage and handling. Additionally, images on copies manufactured from tacky toners have a tendency to offset onto adjacent surfaces. Some tacky toners form smears on reusable electrophotographic imaging surfaces which are difficult to remove. Where the toner materials smears excessively, a film of toner material builds up on the electrophotographic surface. This film has different electrical characteristics than the plate and, if hydroscopic in nature, detrimentally affects the conductivity of the electrophotographic surface when relative humidity is high. Thermoplastic resins having consistently uniform molecular weights are difficult to manufacture. Since thermoplastic resins are usually an amorphous mixture of polymer chains having different molecular weights and normally possess a nonuniform melting range rather than a sharp melting point, it is difficult to accurately predict the temperature at which any given polymeric thermoplastic resin will fuse and adhere to a receiving sheet. Toners having erratic fusing temperatures and wide fusing temperature ranges require that the machines have a built-in fusing safety factor. Since the temperature in the fuser cannot be raised above the char point of the paper, this often imposes an undesirably low upper limit on thespeed ofthe paper through the fuser. Further, the heat fusing units currently employed to fuse conventional thermoplastic toners often cause the temperature of poorly ventilated rooms to reach levels which shorten machine component life and contribute to operator discomfort. It is known, as disclosed in U.S. Pat. No. 3,130,064 to improve toner fusing at lower temperatures by employing business machine record cards treated with thermoplastic resins dissolved in organic solvents. 'Unlike a plasticizer, the thermoplastic resin apparently functions as a melting agent with like melting like." Although the disclosed plastic resin films may reduce toner fixing temperatures, the thermoplastic resin melting range problems described above have not been obviated. Pencil and ink markings are diflicult to apply and remove from surfaces coated with the ther moplastic resin films. Also, more complex equipment and specially designed paper making processes are required when the thermoplastic resin films are applied with inflammable, expensive and toxic organic solvents. Since most thermoplastic toner particles, receiving sheets, and developing processes are deficient in one or more of the above areas, there is a continuing need for abetter system for fusing toner images.
it is, therefore, an object of this invention to provide a receiving surface overcoming the above-noted deficiencies.
It is another object of this invention to provide a receiving surface which reduces the quantity of heat energy necessary to fuse toner images.
It is another object of this invention to provide a receiving surface which effectuates uniform and sharp toner fusion temperatures.
it is another object of this invention to provide a receiving surface which is receptive to ink and pencil markings.
It is another object of this invention to provide a receiving surface which is easily erasable.
It is another object of this invention to provide a receiving surface which allows the employment of cooler, more compact toner fusing units.
It is another object of this invention to provide a receiving surface which permits the use of higher electrophotographic imaging machine speeds.
It is another object of this invention to provide a receiving surface which allows the employment of high melting nontacky toners.
It is another object of this invention to provide a receiving surface having physical and chemical properties superior to those of known receiving sheets.
The above objects and others are accomplished, generally speaking, by providing a receiving surface treated with a solid crystalline plasticizer which effectuates complete thermoplastic toner fusion under heating conditions at which untreated surfaces afford only marginal or no fusion. Crystalline plasticizers, which separate from the thermoplastic resins when the plasticized resin is cooled to room temperature are used because tacky images and attendant offset problems are then avoided. It is believed that separation occurs in the form of tiny islands of crystalline plasticizer particles in a matrix of toner material. Although it is not clear, it is believed that when solid, crystalline plasticizers are heated above their melting point, they weaken the Van der Waal forces existing in the thermoplastic toner polymers and allow slippage of the long linear polymer chains thereby promoting fluidity at lower temperatures. Experiments have revealed that some liquid plasticizers provide virtually complete toner fusion under heating conditions at which untreated receiving surfaces give only marginal fusion, but the resulting image is either permanently tacky or tacky for extended periods of time. Receiving surfaces carrying tacky images plasticized with liquid plasticizers will offset toner material to adjacent surfaces and cause feathering of the images. Additionally, the nonimaged areas of receiving surfaces treated with liquid plasticizer will at room temperature actively soften and render tacky any thermoplastic image on adjacent surfaces. A solid crystalline should have a melting point below the melting range of the 5 thermoplastic toner resin. The uniform and sharp melting point characteristics of crystalline plasticizers permit the employment of cooler and more efficient fusing units in precision electrostatic imaging machines.
Outstanding results have been obtained with ethylene glycol dibenzoate (EGDB) and blends of EGDB and diphenyl phthalate (DPP). When receiving surfaces treated with EGDB are employed, the speed of existing electrophotographic copying machines have been more than doubled. Additionally, EGDB recrystallizes in seconds when cooled to room temperature. Other suitable solid plasticizers may, however, be substituted for EGDB. Typical solid, crystalline plasticizers include: ethylene glycol dibenzoate, dimethyl isophthalate (DMIP), glycerol tribenzoate, dicyclohexyl phthalate (DCHP), diphenyl phthalate, and blends thereo Any suitable receiving surface may be treated with the plasticizer material of this invention. For example, the surface of sheets, webs, planks, or even massive objects may be coated or impregnated with the solid plasticizer of this invention. The 2 5 receiving surface may be composed of any suitable organic material, inorganic material, or mixtures thereof. 1f the receiving surface contains a thermoplastic resin, it may be desirable to select a plasticizer which does not plasticize and distort the receiving surface. Conversely, distortion of the receiving surface may be deliberately induced to achieve a desired decorative effect.
The plasticizer composition may be applied to the receiving surface by any conventional method such as spraying, electrostatic deposition, dipping, fluidized bed coating, brushing, or
roll coating. Further, the plasticizer may be added to the receiving surface in any suitable manner prior to, during, or subsequent to the manufacture of the receiving surface. For example, the plasticizer may be applied alone or in combinaacetylated starch, styrene-butadiene latex, carboxy-methyl cellulose, polyvinyl pyrrolidone, acrylic latex, polyvinyl acetate copolymers, polyvinyl alcohol, soy proteins, casein, hydroxyethylated starch and mixtures thereof. Any of the conventional additives such as antioxidants, emulsifiers,
to immovably attach the solid brightners, solvents, surfactants, suspending agents, antifoam agents, coloring agents and fillers may be employed with the tadiene copolymers, polyvinyl pyrrolidone, casein, polyvinyl alcohol and mixtures thereof are preferred because they are very stable in conventional high-speed paper coating apparatus. Surprisingly, toner images formed on receiving surfaces treated with a binder and plasticizer mixtures are more dense than toner images formed on untreated receiving surfaces. Additionally, paper sheets treated with a binder and plasticizer mixture lie flatter after toner fusion than untreated paper. It is preferred that the binder content remain below about 40 percent, based on the weight of the plasticizer, as this fused to the receiving member.
Paper sheets or webs are nonnally employed as the receiving surface in most conventional electrostatic imaging processes. The paper may comprise organic and/or inorganic fibers such as cellulose, modified cellulose, polymeric resin, glass, and asbestos fibers. The plasticizer may be sheet formation, e.g., in the beater, or subsequent to web formation, impregnation,
of plasticizer per 1,300 square feet is applied to receiving sur- 2,788,415 to Rheinfrank and Jones. These toners generally have an average particle diameter between 1 and 30 microns. Clearly, the plasticizer treated receiving surface should be used with those thermoplastic resin toners which will be plasticized by the specific plasticizer employed in the receiving surface. Selection of compatible combinations of solid crystalline plasticizer and thennoplastic resin toner will be obvious to those skilled in the art. Blends of two or more plasticizers may be used to broaden the toner spectrum of the receiving surface. Typical thermoplastic resins include: acrylic resins, methacrylic resins, cellulose acetate, cellulose nitrate,
TONER FUSION EFFECTS OBTAINED ON PAPER TREATED WITH PLASTICIZERS Plastieizcr compositions,
Styrenebutadione latex Grind" (Dow 636) Examples P (EGDK) 7(DPP) and 73 (EGDB) 299(DMIP) 5 80 (EGDB) so EGI B IIIQIIIIIIIIIIIIIIIIL. *Prepared by diluting ball mill grinds of the following compositions (parts by weight) with the indicated additivr-s:
parts by w eight Polyvinyl pyrroli- Power done, 20% Acetyindex, solids lated watts/ (K-30) starch (ilL/SOC.) 'Ioncrfusionrcsults 500 Fuses, no rub oil, non-tacky.
250 Vvry poor fusing, powdery rub on.
133 Good fusing. no rub off, slightly tricky.
133 (i00(lll1Sl11[ ',1101'11l oil, non-tricky. 115 D0. 276 Do. Do. 30 225 D0.
Sodium salt of processed rosin (Dresinate X): Pvolyvinyl pyrrolidone (PVP type K-130).
Ethylene Dicycloliexyl Diplrenyl glycol Dimothy phthalate p11 tlmlatc dibunzoutc isoplitlnilutv. (DCHI) grind (DPP) grind (EGDB) grind (DM 11) grind 150 150 150 1 l 1 1 2 2 2 2 14" 147 277 146 polystyrene, polyethylene, polypropylene, polycarbonate, modified phenolformaldehyde resins and mixtures thereof.
The following examples further define, describe and compare exemplary methods of preparing the receiving surfaces of the present invention and of utilizing them as substrates for electrostatic latent images. Parts and percentages are by weight unless otherwise indicated.
ln the following, examples l-lX are carried outwith a toner comprising a styrene and n-butylmethacrylate copolymer, polyvinyl butyral, and carbon black prepared by the method disclosed by M. A. lnsalaco in example I of U.S. Pat. No. 3,079,342. The treated receiving sheets carry a surface coating of a plasticizer mixture applied as an aqueous dispersion by means of a smooth metal reverse roll in a Dietzco-Dixon Pilot Coated followed by doctoring with a reverse rotating No. 4 wire-wound and finally dried by heated air. The electrostatiln the following examples X-XXXIX, sheets treated with the compositions in table A are compared with untreated sheets. Different quantities of treatment material per ream and various transport speeds are employed to demonstrate how these two factors affect fusing energy requirements. The power index required to obtain equivalent fusion with untreated paper is determined by comparing the rub off from a treated sheet with a standardized rub off series obtained with untreated sheets. The images on untreated and treated sheets are deemed equivalent when the quantity of rub ofi from each is identical. The toner material is rubbed off by drawing a 2- inch square cloth (Crockmeter Square, Test Fabrics, Inc.) weighted with a 500 gram balance weight across and along an 1 l-inch length of the images sheet. The percentage reduction in power input required to obtain equivalent fusion was calculated according to the following formula:
Percent reduction in power:
Power index required to obtain equivalent fusion with untreated paper TABLE A.PLASTICIZER COMPOSITIONS [Parts by weight] Hydroxyethyl Sodium salt derivative of procof corn Povyvinyl Styrene- Ethylene Polyvinyl essed rosin starch alcohol, butadlene Treatment glycol pyrrolidone, (Dresinate (lenford Elvanol latex system dibenzoate (K-30) Gum 250) 72-60 Water (Dow 636) 840. 0 l1. 2 2, 051. 2 265. 0 840.0 11. 2 1, 551. 2 304. 0 840. 0 11. 2 '..,051. 2 304. 0 840. 0 11. 2 .2, 051. 2 304. 0 840. 0 11. 2 2, 051. 2 304. 0
TONER FUSION PROPERTIES OBTAINED WITH PAPERS TREATE D WITII lLASTICIZE RS Power index Correrequired to spending obtain fewer equivalent Redution Treatment Treatment Power 'Irunsindex, fusion with in power system level, settings port speed, watts/ untreated input, Examples applied* lbs/ream used watts, in./scc. (in./see.) paper percent 864 1. 7 508 508 0 864 1. 4 617 617 0 864 1. 1 783 783 0 864 1. 7 508 718 29. 0 864 1. 4 617 718 14. 1 864 1. 1 783 1, 438 45. 6 864 1. 7 508 718 20. 0 864 1. 4 617 057 35. (i 864 1. 1 783 J57 18. 2 864 1. 7 508 664 21. 3 864 1. 4 617 718 14.1 864 1. 1 783 1, 140 31. .l 864 1. 7 508 718 20. 8 864 1. 4 617 8612 28. 5 864 1. 1 783 1, 438 45. ti 864 1. 7 508 040 20. 1 864 1. 4 617 957 35. 6 864 1. 1 783 1,140 31. 9 864 1. 7 508 783 35. .3 864 1. 4 617 J57 35. 6 864 1. 1 783 1,14!) 31. J 864 1. 7 508 86'. 41. 1 864 1. 4 617 861.. 28. 5 864 1. 1 783 1, 438 45. 6 864 1. 7 508 783 35. 2 864 1. 4 761 J57 35. 6 864 1. 1 783 1, 138 45. 6 864 1. 7 508 862 41. 1 83-1 1.4 617 J57 35. t) 834 1. 1 783 1, 138 45. 6 See Table A. cally imaged sheets are passed at selected speeds under a EXAMPLE XXXX quartz filament infrared heater unit operated with a fixed power input. For comparative evaluations, a power index" value is assigned to the fusing conditions employed. The power index value is computed as follows:
Tack and the quantity of powder rub ofi' of the fused images onto cotton are also compared.
Paper sheets are treated with ethyl phthalyl ethyl glycolate, a liquid plasticizer, by dipping the sheets into a methyl alcohol 70 solution containing about 10 percent by weight of the 75 toner image is completely fused under these heating conditions. With untreated paper, the same heating conditions provide only marginal fusion of the toner image. However, upon aging, the paper treated with the liquid plasticizer is found to offset toner to adjacent sheets and cause feathering of ink images.
EXAMPLE XXXXI Paper sheets are treated with cresyl diphenyl phosphate, a liquid plasticizer, by dipping the sheets into a methyl alcohol solution containing about 9 percent by weight of the plasticizer. After the alcohol solvent is driven off, an electrostatically deposited styrene copolymer toner image is transferred to the treated sheet. The sheet is then heated on a back side with a bar type heater for seconds at 125 C. The toner image is completely fused under these heating conditions. With untreated paper under these same heating conditions, only marginal fusion of the toner image is obtained. However, upon aging, the paper treated with the liquid plasticizer is found to offset toner to adjacent sheets and cause feathering of ink images.
EXAMPLE XXXXII Paper treated with a plasticizer composition containing about 1,080 parts EGDB, 14.4 parts polyvinyl pyrrolidone K-30), 340 parts butadiene-styrene latex, 0.14 part brightner (Calcofluor White CBP), 5 parts ammonium hydroxide (28 percent), 7.2 parts polymerized sodium salt of an alkyl naththalene sulfonic acid (Daxad l 1) and 1,083 parts water is imaged with a styrene copolymer toner in a Xerox 813 electrophotographic copier machine (similar to the machine described in US. Pat. No. 3,099,943) at a 12 copies per minute speed. This speed is twice the normal speed of the Xerox 813 copier. The toner image is fused and nontacky. No toner fix whatever is obtained with standard office bond paper run in the same machine at the same speed.
EXAMPLE XXXXlll EXAMPLE XXXXIV A styrene-methyl methacrylate copolymer toner is imaged onto a paper sheet treated with the EGDB composition of example VIII above. Upon heating between two parallel heater plates, spaced 1 inch apart, the toner fuses more rapidly on the treated paper than on untreated paper under substantially identical heating conditions.
Although specific materials and conditions are set forth in the foregoing examples, these are merely intended as illustrations of the present invention. Various other suitable thermoplastic resin toners, receiving surfaces, plasticizers, binders, and coating processes such as those listed above may be substituted for those in the examples with similar results. Other materials may also be added to the base, plasticizer, binder or toner to sensitize, synergize or otherwise improve the fusing properties or other desirable properties of the system.
Other modifications of the present invention will occur to those skilled in the art upon a reading of the present disclosure. These are intended to be included within the scope of this invention.
1. A toner image receiving member capable of producing nontacky images with no rub off comprising a paper base and adhered thereto and available at an external surface of said base at least one solid crystalline plasticizer, said solid crystalline plasticizer being a plasticizer for finely divided thermoplastic toner particles when said plasticizer and said toner particles are fused together, said plasticizer having a melting point of at least about 45 C. and below the melting range of said thennoplastic resin toner and being present in an amount of at least about 0.4 pound per 1,300 square feet of said external surface of said base, said solid crystalline plasticizer being capable of rapidly recrystallizing after being cooled below the melting point, said external surface of said base being free of material plasticizable by said solid crystalline plasticizer.
2. A toner image receiving member according to claim I wherein said solid crystalline plasticizer is adhered to at least the surface of said member by means of a binder composition, said binder composition being free of material plasticizable by said solid crystalline plasticizer.
3. A toner image receiving member according to claim 2 wherein said solid crystalline plasticizer is adhered to said toner receiving member by less than about 40 percent by weight of said binder, based on the weight of said plasticizer.
4. A toner image receiving member according to claim I wherein said solid crystalline plasticizer is available at said image receiving member as a powder.
5. A toner image receiving member according to claim I wherein said base comprises a paper web.
6. A toner image receiving member according to claim 2 wherein said binder composition comprises a binder selected from the group consisting of polyvinyl pyrrolidone, styrene butadiene copolymer, acetylated starch, casein, polyvinyl alcohol, and mixtures thereof.
7. A toner image receiving member according to claim 1 wherein said solid crystalline plasticizer comprises ethylene glycol dibenzoate.
8. A toner image receiving member according to claim 7 wherein said ethylene glycol dibenzoate is blended with diphenyl phthalate.
9. A toner image receiving member according to claim I wherein said solid crystalline plasticizer comprises dimethyl isophthalate.
10. A toner receiving member according to claim 1 wherein less than about 1.5 pounds per L300 square feet of said solid crystalline plasticizer is present on said external surface.
i 0' i III