CA1036861A - Imaging method - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE
An imaging method is provided for obtaining a resinous toner image fixed to a copy substrate. The method comprises applying to a copy substrate in image configuration a toner comprising a crystalline polymer having a melting point of from 50° to 150°C., an activation energy for viscous flow of less than 35 K.cal./molce, a bulk resistivity of greater than 1012 ohm-cm, and a molecular weight within the range of from 5,000 to 200,000, and fixing the image to the copy substrate by a heated roll fusing device.

Description

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- ~Q36861 ~sMh~I~--k~THOD ~, This invention relates to electrostatography and more particularly to an improved imaging method. In its more specific aspects, the present invention provides an electrostatographLc imaging method employing crystalline S toner materials which enable hot roll fusing of the image over a broad fusing latitude.
The formation and development of images on the surface of photoconductive materials by electrostatic means is well known. The basic electrostatographic process, as taught by ~-;
C. F. Carlson in U.S. patent 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 11ght and developing the resulting electrostatic latent image lS by depositing on the image a finely dlvided electroscopic material referred to ln the art as "tonern. The toner will normally be attracted to those areas of the layer which re-~;
ta~n a charge, thereby forming a toner image corresponding~;
to the electrostatic latent image. This toner image may then be transferred to a copy substrate such as paper. The transferred image may subsequently be permanently affixed - to the copy substrate such as by fusion with heat. Instead of forming the latent image by uniformly charging the photo-conductive layer and then exposing the layer to a light and shadow image, one may form the latent image by directly charging an insulating layer, which can be either photo-conductive or non-photoconductive, in image configuration.
The powder may be fixed directly to the insulating layer if desired. ~ ~
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~, In the Carlson patent, it is noted that a variety of types of finely divided electroscopic powders may be employed for developing electrostatic latent images. However, as the art of electrostatography has progressed, it has been found preferable to develop line oopy i~ages with a powder or toner formed of any of a variety of pigmented thermoplastic resins that have been specifically developed for the purpose. A ;
number of such developing materials are manufactured and '~
marketed commercially and are specificaily compounded for 10 producing dense images of high resolution. Such developing materials are compounded to permit them to be fixed to the surface of a copy substrate by suitable techniques, in accordance with the particular application in which they are employed. - -One of the important applications of electrostatography comprises its use in automatic copying machines for general office use wherein an electrostatic latent image is developed with fine particles of res1nous toner, and the thus formed powder image is transferred to a copy substrate and then 20 fixed thereon. Considerable effort has been expended to pro- ;
vide suitable developers and associated fixing techniques ~ -~
for modern high speed copying machines-.
Although several development techniques are employed commercially today, the most widely used commercial electro-statographic development technique is the process known as~cascade~ development. A general purpose office copying machine -' incorporating this development method is described in U.S.
patent 3,099,943.~ The cascaae development technique is generally '-~ 3 I --,~
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1~36861 ~
carried out in a commercial apparatus by cascading a developer mixture, comprising toner and carrier particles, over the surface of an electrostatic latent image-bearing drum having a hori!zontal axis. The developer mixture can be transported fro~
5 a trough or sump to the upper portion of the drum by means ~' of an endless belt conveyor. After the developer mixture is cascaded downward along the upper quadrant surface of the drum ,' into the sump, it is recycled through the developing system .to develop additional electrostatic latent images. The 10 composition Gf the carrier particles is so selected as to triboelectrically charge,the toner particles to the desired polarity. As the mixture cascades or rolls across the image ,~
. ~
bearing surface, the toner particles are electrostatically deposited and secured to the charged portion of the latent image 15 and are not deposited on the discharged or background portions , ' of the ~mage. Most of the toner pa_tic~es accider.tall,r deposited in the background are removed by the rolling ,~, carri-r due, apparently, to a greater electrostatic attraction '~
. between the toner and the carrier than between the toner and ~r the discharged background. Small quantities of toner are periodically added to the developing mixture to compensate ~ '~
for the toner depleted by development. The resulting toner ~,~
- image is usually transferred to a copy substrate and therè-after fused thereon by suitable means. The surface of the drum is 25 thereafter cleaned for reuse. This imaging process is then -~
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repeated for each copy produced by the machine and is ordinarily -repeated many thousands of time during the usable life of the developer.

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1(~36861 The ~-~ner material used must have s~itable electro-static properties to perMit attraction by the carrier and -~ - then s!elective attraction by the latent images. It must further be physically strong to per~it constant recycling S in a bouncing type of movement. The toner must further be resistant to blocking or aggregating at ordinary operating temperatures, but yet be capable of being readi`ly fixed to the copy sheet. ~ ;
Fixing techni~ues empl6ying heat, pressure, solvents and various combinations thereof have been devised; however, each ,.
of these systems is subject to severe practical limitations whioh inhere in the systems themselves and also the toner compositions heretofore available. Whatever method of fixing i8 used, speed, effectiveness, and simplicity in operation are .
the principal, desirable characteristics to be obtained.
The most commonly empioyed fixing techniques employ the use of heat alone or heat in combination with pressure. The toner materials employed must melt or block sufficiently above . ..
the ordinary operating temperatures of the machines involved to assure convenient storage and handling. However, the materials must also melt at a practically low temperature to avoid excessively-high energy consumption and possible-heat damage to the copy substrate or delicate machine parts. . ;
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~ It has long been recognized that one of the fastest and st positive methods of applying heat for fusing the powder image to paper is to bring the powder image into direct contact with a hot surface, such as a heated flat plate or roller.
- Howeve~, it was found that as a powder image is tackified by contact heating, part of the image carried by the copy sheet would stick to the hot surface so that as the next : . :

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copy sheet was con~tact~ wi~h t~e.hDt'~rf.ace, ~he tackified ~
image partially removed from the first sheet would partially ~' .':'transfer to the next sheet and, at the same time, part of the .. .,, . ~, . . ....
- tackifiea image from said next sheet would adhere to the hot .-surface. This phenomenon is commonly referred to in the printing art as "offset". For a given system, this upper ~;
temperature limit is re~erred ~o~a;s~t~e "ho* off~.et bempera.ture".
Thus, contact heat fusers are inherently limited to the use of : . temperatures and toners which do not cause hot offset of the .7 ".10 toner material.
; ~ It is further necessary that the particular toner be ~
used at a temperature above the minimum fusing temperature. '~:
.~
The temperature at which a toner fuses is that temperature -at which the viscosity of the toner becomes low enough to A
"' 15 permit adhesion of the toner to.the receiving sheet and is .~-referred to as the ~minimum fusing temperaturen. The minimum fusing t mperature and the hot offset temperature are machine related . parameters'~depending upon pressure, characteristics of the '.
heating surface, speed, etc.) and the difference between the ' -~
20 two temperatures defines a fusing latitude of acceptable viscos~
~ity ranges for image fixing.~
Initially, the severe practical restrictions presented '' . by~the offset of toner onto the.hot contacting surface and .'i:
. ~ the narrow fusing latitudes obtainable with toner materials $
25 heretofore ~nown, led to the reject_on of contact fusers in favor of other heat fusing devices, primarily radiant element .
heaters with reflectors. Recent increases in machine speed, ~and the use of toners having relatively high glass transition ,~
temperatures to avoid blocking of the toner materials during :, .
storage, have necessitated the use of high capacity heating ' units. Such units give rise to the conflicting problems of provid- ^
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~; ing'adequate heat 'for fusing while avoiding charring of the paper copy substrates and of adequately dissipating the heat evolved from the fusing unit or units. Thus, in order to avoid ~' scorching or discoloration of the paper additional equipment S such as complex, costly cooling units is necessary to properly dispose of the large quantities of he-a~ generated by the fuser.
Incomplete removal of the evolved heat can result in operator discomfort and deterioration of heat sensitive machine components;
Further, the increased space occupied by, and the high operating costs Qf, the heating and cooling units often outweigh the ad~
~antages achieved by the increased machine speed.
While further advances in the art~of fixing, including ~' - , - , , , ,~
the-use of offset reducing roller surfaces, have provided more suitable means to fuse toner îmages through the use of heat ' a~d pressure with decreased offset, these devices are still .. . , restricted to operate within close tem~erature ~oleranGes dne to the narrow-fusing latitudes obtainable with toner materials heretofore available. Exemplary of these contact fusing devices ar~ those disclosed in U.S. patents 3,256,002, 3,268,351, 3,291,466, 3,437,032, 3,498,596'and 3,539,161, The toner compositions of -. ,,, ,: .
the present invention are especially useful in conjunction with such contact fusing devices. ~ ' --' It is an object of the present invention to provide an improved method for-obtaining a resinous image fixed to a copy substrate.
It is another object of the present invention to provide an electrostatographic imaging method empIoying toner materials having sufficiently high blocking tempera-30 ' tures to avoid the practical problems associated with blocking ~-of the toner material under operating temperatures ordinarily ~4 ''`~
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~036~61 employed in electrostatographic copying machines.
It is a further object o~ the present invention to provide an electrostatographic imaging method employing toner materials having relatively low minimum fusing tem~
S peratures thereby avoiding the use of excessively high quantities of heat which could cause serious technical and ~s practical problems. `
It is yet another object of the present invention . to provide an electrostatographic imaging method employing toner materLals having sufficiently~high hot offset-temperatures to prevent the adverse effects caused by offsetting of the hot toner material.
It is yet a further object of the present invention to provide an electrostatographic imaging method employing toner , .
lS materials having broad fusing latitudes, thus providing a ~-high degree of flexibility in electrostatographic copying systems employing hot roll fusing of the toner images.
These as well as other objects are accomplished by the present inv ntion which provides a method for developing an electrostatic latent image-bearing surface comprising:
developing an electrostatic latent image-bearing surface with a developer comprising a toner being characterized `~
as a crystalline polymer exhibiting~
, ~
(i) a melting point of from 50 to 150C, and preferably from 55 to 100C;
(ii) an activation energy viscous flow of less than 35 R.cal./mole, and preferably less than 15 K.cal./mole;
(iii) bulk resistivities of greater than 1012 ohm-centimeters; and,~
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(ivl a molecular weight wLt~n the ~an~e of from S,000 to 200,000, and fixing said developed image by passiny said developed image-bearing surface through a zone of heat and pressure.
In pressure roll ~ixing of electrostatographic toners, three interrelated parameters of utmost importance in toner performance are: (1) the minimum fusing temperature, MFT, (the minimum temperature required for fusing the taner);

(2) the hot offset temperature, HOT, ~the minimum temperature at which the hot toner melt begins to adhere to the pressure .
member, i.e., the maximum temperature of operation which avoids -.
~ this type of fixing failure); and (3) the fusing latitude, FL, - .;
(the operating range defined as the aifference between HOT and MFT).
Viscosity-temperature relationships for toner materials have been established, and it~is found that a certain viscosity range is required for the onset of fusing.
A second, somewhat lower, viscosi * range has been found t~
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to correspond to offsetting. The difference between these .
viscosity ranges is called the ~fusing window". The fusing ~
~-~
; window depends to a great extent on cpecific machine parameters, such as COmpQnentS~ configuration, speed, etc. For maximum range of fixing operation, i.e., maximum fusing latitude, one ~ ?
reguires a toner having a minimum temperature dependence on viscosity and miximum traverse of the fusing window.
It has been found that the toner compositions employed according to the present invention satisfy these criteria.
Furthermore, the melting points of the crystalline polymers employed accordi~-g to the present invention effectively control the blocking behavior of the toner compositions.
These sharp melting crystalline toners do not block under ~;
ordinary ambient operation conditions; however, they melt _ g _ . , .
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~sharply near the minimun~ fusing temperatur~ and provide a broad traverse of the f~sing window.
It is desirable, and a principal feature of the present invention, to have the toner materia} melt sharply at - 5 a temperature safely above the ambient operating conditions for the system, with a molecular weight appropriate to brins the toner material to a viscosity which wiLl readily prqvide adherence to the copy sheet, and once melted to have a rela- -~
tively low activation energy, siow viscosity change with increasing temperature, such that the broadest possible fusing window can be achieved. The crystalline toner materials loyed according to the present invention exhibit low - activation energies for viscous flow, being on the order of less than 35 K.cal./mole, and preferably less than 15 R.cal./mole.
; 15 Furthermore, the crystalline toner materials used in the present ~nvention meitsharply and nave a minimal dependence of viXco4iry - .~
on temperature.
` The crystalline polymers employed in the toner compositions used according to the present invention are those 20 having (a) melting points of from 50 to 150C., and preferably -~
from 55 to 100C.; (b) activation energies for viscous flow of less than 35 K.cal./mole, and preferably less than 15~K.cal./mole; (c) bulk resistivities of greater than 1012 ' ~
ohm-cm.; and (d) molecular weights of from 5,000 to 200,000 and ~`
25 more preferably 20,000 to 100,000. The exact choice of mole- -g cular weight will of course depend upon polymer structure and ~
molecular weight distribution. In general, the preferred ~:
molecular weight.will be lower for polar polymers than for non-polar polymers. Particularly suitable for the toner ..
materials employed according to the present invention are the following polymers which have the indicated melting points -~

Tm(C) and are described in the reerences noted. Th~ first .; ..... -, ~,, - . :

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number in the reference column is an iden~ification number for the reference as listed in Polymer Handbook, Editors J. Brandrup and F.H. Immergut, Interscience Publishers, , : New York, New York, third printing (1967), pp. III-51 to r~
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- ~036B61 ....................... ~ ~
,~, The term"crystalline polymers"is me~ant to incl-ude homopolymers, copolymers, and mixtures of polymers and/or copolymers in which at least one component is crystalline, -and has a melting point in the defined range and which has an overall activation energy in the defined range. Examples of suitable copolymers include copolyesters, such as formed from ethylene sebacate and ethylene succinate hexamethyl:en~ sebacate and ethylene succinate and the like; p_lyolefln copolymers, such as formed between ethylene and propylene, mixed copolymers ~
such as ethylene and vinyl acetate, copolyamides; copolyethers and the like. . ~ ~
The toners employed in the method of the present ~.-invention are desirably colored by~a suitable pigment or dye. ~
Toner colorants are well known and;include,.for example, .
carbon black, nigrosine dye, aniline blue, Calco Oil Blue, : ; .
chrome yellow, ultra marine blue, Quinoline Yellow, methylene blue chlorlde, Monastral Blue, Malaohite Green Oxalate, ; t lampblack, Rose 8engal, Monastral Red, Sudan Black BN, and mixtures thereof. The pigment or dyes should be present in~ m the toner in sufficient quantity to render lt highly colored~-so that it will form a clearly vlsible lmage~.on a recording;~
member. Thus, for example, where:.conventional electrostato-graphic copies of typed documents are des1red, the toner may ` L
- comprise black pigments such as carbon black or a black dye such as Sudan Black BN dye available from GAF Corporation.
Prefe.ably, for sufficient color density, the pigment is employ-. ed in an amount from about 1% to about 20% by weight based on -the total weight of the colored toner. If the toner colorant employed is a dye, substantially:smaller quantlties of the 30 colorant may be used. The colorants may be mixed with the resin ,~!

component prior to, during, or after the polymerization of-the -~
~ -~22 ~
~,.

~03~;86i ~
resin companent. Obviously, any colorant which inhibits poly- -~merization should be blended with the resin after the resin is formed.
Plasticizers and melt diluents may also be employed so long as they do not ad~ersely affect the sharp melting character, temperature ~oefficient of viscosity or viscosity of the toner compositions. Thus, the plasticizers and melt diluents can also be crystalline materials which maintain their crystallin-ity i~ the final toner composition, and should not have too low of a viscosity. Where such materials are employed, they must-:
be selected on a case by case basis to insure that they do not ad-~versely affect the final characteristics of the toner composition.
The toner compositions employed in the method of thé ;~
present invention can be prepared by any well known toner mixing and comminutating technigue. For example, the ingredients can -~be thoroughly mixed by blendinq and milling the components and , thereafter micropulverizing the resulting mixture. Another well known technique for forming toner particles i5 to spray dry or `~

~ freeze dry a dispersion, a hot melt, or a solution of the toner composition.
, . , . ~
- ~`When the toner compositions employed in the method of this invention are to be employed in cascade development processes, ~;
. -~
i ~ the toner particles shouLd have an average diameter of less than -` ~ about 30 microns and preferably between about 3 and about 10 microns for optimum results. Particle diameters, generally are - determined as optimums for the various types of development ; known.

Suitable coated and uncoated carrier materials for cascade and magnètic brush development are well known in the art.

30 ~ Carrier particles can be electrically conductive, insulating, - ~ - 23 -....
.
. ~ : - , . . , . ~
. ,~ .. . , ,~

~r 1~3~61 magnetic or non-magnetic, provi.ded thalt the carrier par~icles ~.
acquire a charge having an opposite polarity to that of the toner particles when brought into close contact with the toner -~
particles so that the toner particles adhere to and surround ..
the carrier particles. When a positive.reproduction of an ~ ~
electrostatic image is desired, the carrier particles are selected ~:
o that the toner particles acquire a charge having a polarity oppo~ite to that of the electrostatic latent image. Alternatively, if a reve~sal reproduction of the electrostatic image is desired, the Carriers are selected so;that the toner particles acquire a charge having the same polarity as that of the electrostatic ~
image. Thus, the materials for the carrier particles are selected ..
- in accordance with their triboelectric properties relatLve to .
the electroscopic toner so that when mixed or brought into mutual lS contact, one component of a developer is charged positively if .
the other component is below the first component in the tribo~
olectric 8eries and negatively if the other component is above the first component in the trLboelectrlc series. By proper selec-tion of materials in accordance with their triboelectric effects, the polarities of their charge when mixed are such that the~elec- ~.^
:- troscopic toner particles adhere to and are coated on the-sur-~ . faces of carrier particles and also adheré to that portion~of .
. ~ ., .......................................... . . .
- the electrostatic image bearing surfaces having a:greater~
attraction for the toner than the carrier particles. .~
z5 Typical carriers include sodium chloride, ammonium chloride, aluminum potassium ch}oride,.Rochelle salt, sodium nitrate, aluminum nitrate, potassium chloride, granular zircon, granular silicon, methylmethacrylate, glass, silicon dioxide, .-~
iron and alloys thereof and the like.`` The carriers can be..coated or uncoated. Many of the foregoing and other typical carriers are described by L.E. Walkup in U.S. patent 2,618,551; L.E. Walkup - 24 ~ .

- , - , . .~

1036B6~
et al in U.S. patent 2,638,~16 and E.N. Wise in U.S. pat~nt 2,618,552. An ultimate, coated carrier particle diameter between about 50 microns to about 1,000 microns is preferred be-cause the carrier particles must possess sufficient density and inertia to avoid adherence to the electrostatic images ~
during the cascade development process. Adherence of the ~ i carrier beads to electrostatographic drum surfaces is undesirable because of the possible formation of deep scratches on the surface dur$ng the image transfer and drum cleaning steps, particularly where cleaning is accomplished by web cleaner such as the web disclosed by W.P. Graff, Jr., et al in U.S. patènt 3,186,838. ~~
-~ Al~o, print deletion occurs when carrier beads adhere to the electrostatographic imaging surfaces. Generally speaking, ~
~.
atisfactory results are obtained when about 1 part toner is used with about 10 to 200 parts by weight of carrier. ~--The toner compositions employed in the m~thod of ~he present invention can be employed to develop electrostatic latent images on any sultable electrostatic latent image-bearing- -~urface including conventional photoconductive surfaces as well as insulating, non-photoconductive surfaces. Well known ~
photoconductive materials include vitreous selenium, organic --; `~ ` or inorganic photoconductors embedded in a non-ph~toconductive matrix, and the like. Representative patents in which photo-conductive materials are disclosed include U~S. patent 2,803,542 to Ullrich, U.S. patent 2,970,906 to Bixby, U.S. patent 3,121,006 - to Middleton, U.S. patent 3,121,007 to Middleton, and U.S.
, . . .
- patent 3,151,982 to Cortson. -- The crystalline polymeric component of the toner compositions in the present invention may be made according to well known polymerization techniques such as those described in R.W. Lenz, "Organic Chemistry of Synthetic ~igh Polymers", ~ 25 - - s . I

J~
~03~
Interscience, New York, New York (1967). However, because it is necessary that the resultant toner materials have the requisite bulk resistivity of greater than about 1012 ohm-centimeters, it is!essential that all impurities which may adversely effect ~!~
S the electrical properties of the toner be removed by suitable -~
techniques.
The following examples are for the sole purpose of further describing the present invention and are not to be taken.as iimiting the invention~'~o the specific materials or 10 conditions employed therein. Unless otherwise specified, all parts or percentages are by weight.
EXAMPLE I
~ Poly(hexamethylene sebacate) is prepared by reacting /-~' 52 lbs. of hexamethylene glycol and 85 lbs. of sebacic acid in the presence of 62 grams of lead acetate in a kettle at 430F. at abmo~phPri- pressur2. Dur:ng the rcactior., the temperatur is ad~usted to 480F. and vacuum applied. After 13 hours of '~
reaction time,the product of intrinsic viscosity 0.6 deciliter/gm.
is cooled. This polymer has a number average molecular weight -~
. . ~-of 11,400 and a melt viscosity at 85C. of 2.3x103 poises. The melt viscosity is Newtonian, i.e.,'independent of shear rate, up to at least 10 sec. 1. The activation energy for viscous .
flow, Ea, is found to be 8.4 K.cal./mole. The crystalline polymer melted at 65C., with a heat of fusion, ~Hf, of 23 cal./gm. and an 25 estimated degree of crystallinity, x, of 72%. The volume-~
resistivity is 4xlO ohm-cm.
EXA~LE I I
4so grams'of the poiymer produced in Example I is ad-mixed with MOGUL~L carbon black (50 grams), chloroform (6600 grams) -' and hexane (1/1 by Vol.; 2900 grams). This mixture containing ''~-5% solids is fed through a small spray dryer'at an inlet temperature of about 130F. and an outlet temperature of about ~
*Trademark - 26 - ;

1036861 ', - 105 - 114F. at a feed rate of about 200 ml./min. to produce 390 grams of jet black toner material having a particle size by volume of 9.8 microns. rrhe resulting toner material is !~
admixed with 100 micron steel carrier beads coated with a terpoly-' mer of styrene~methyl methacrylate/triethoxysilane as described in U.S. Patent 3,467,634 to Jacknow, to produce a developer composition containing about 1% by weight of toner. This ¦
developer mixture is used in a "Model D" electrostatographic machine to develop an electrostatic latent image prepared by , 10 ~ exposing a charged selenium photoconductor to a light image of an ANPEG No. 7.011 standard test pattern, contacting the electro-static latent image with the developer, transferring the thus developed image to a sheet of bond paper and fusing the-image by contact-wi~h a heated, pressure rol-l fuser. The quality of the pript produced is good. While adequate fusion is achievéd at temperatures,as low as 230,F., no,offsetting is observed on ¦
the fuser rolls up to a temperature of about 310F., showing a fusing latitude for the toner to be about 80F. The samples ', prepared are tested to determine the number of abrasion cycles for a fixed reduction in optical density for the various fuser roll surface-temperatures. These results are shown-in Table 1. .
TABLE_1 ' - ' ' , .
Fuser Temperature Abrasion (F.) Offsetting Cycles 25 - 230 No 8 230 ~ No 9 .
280 ~ No 9 280 No 11 300 No ' 18 300 - N~ 20 310 , Yes 21 310 Yes 22 ' ~ *Trademar~

t , , , ~.
~ ~ ~

The following comparative examples illustrate the .criticality of the criteria set forth hereinabovo for ~he .~ -crystalline polymers employed in the toner compositions of -.
: of the present invention. ~ r ~ ~: ' ! .
S - Comparative Example I
Two pounds of poly(hexamethylene sebacate) is pre- .
pared by the method of Example I. The intrinsic viscosity of .~-the product is O.lS dl/g and the number average molecular ; weight is 2,000. The activation energy of the molten polymer ~ 10 is 6.i K.cal./mole. Toner is prépared from this polymer by ~- .
~. i , ;.~
the method of Example II. Upon fixing with the same heated ~ :
. pressure roll of Example II, the toner showed immédiate hot ``-. ~ .
. offsetting at the melting point of the crystalline polymér ~--~; - because of the low melt viscosity encountered at thiS low lS molecular weight. -. . Comparative Example II
~ Two pounds of poly(hexamethylene sebacate) is prepared r,~
; by the method of Example I using excess diol. ~The intrinsic :. ~ viscosity of the product is 0.37 and the weight average molecular weight determined by light scattering is 18,000. The diol~
~ terminated polymer is converted to high molecular weight polymer ~ `
- by coupling with TDI (toluene diisocyanate). The product has an intrinsic viscosity of 1.2 and a number average molecular ~.
~ weLght of 700,000. The melt viscosity of the polymer is non-;~25 Newtonian and has a value of 5x107 poise at 10 2 sec 1 at 85C. .
.~ . Toner made from this polymer by the method of Example II does not show satisfactory fixing at temperatures up to 430F with the heated roll fusing apparatus of Example II, because of the .
high viscosity of~this high molecular weight polymer.

: ~ ~ 28 ~

' , . ' ' ',., .

103~86~, Comparativ.e.Exampl.e III ~;
Two pounds of amorphous polymer, polystyrene (PS-2,~. ~
Dow Chemical Co.1 Tg, 68C., having an activation energy for ~ r' visco~s flow of.approximate~y 40 K.cal./mole in the temperature region of 85-100C, is made into toner by the method of Exa~ple II.
S The toner is found to have a fusing latitude of only 20~F in the heated roll fusing apparatus of Example II, because of the ~-.~
rapid reduction in viscosity with temperature indicated by the "
; hlgh actLvation energy of the amorphous polymer.
. .~- Many modifications and variations of the present ~ ~
invention will become obvious to those skilled in the art ~ :
n : upon reading the above disclosure, and it is intended that all : such modifications.and variatlons be included:within the scope ~. .
of the present inventlon which is defined by the following ~- . .
. claims.
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,

Claims (8)

WHAT IS CLAIMED IS:

1. A method for developing an electrostatic latent image-bearing surface comprising:
developing an electrostatic latent image-bearing surface with a developer comprising a toner having at least one component thereof characterized as a crystalline polymer exhibiting:
(i) a melting point of from 50° to 150°C;

(ii) an activation energy for viscous flow of less than 35 K.cal./mole;
(iii) bulk resistivities of greater than 1012 ohm-centimeters, and (iv) a molecular weight within the range of from 5,000 to 200,000, and fixing said developed image by passing said developed image-bearing surface through a zone of heat and pressure.

2. A method according to Claim 1 wherein the crystal-line polymer has a melting point of from 55° to 100°C.

3. A method according to Claim 1 wherein the polymer has an activation energy for viscous flow of less than 15 K.cal./
mole.

4. A method according to Claim 1 wherein the polymer has a molecular weight of from 20,000 to 100,000.

5. A method according to Claim 1 wherein the developed image is transferred to a copy substrate prior to fixing and the developed image is fixed on the copy substrate.

6. A method according to Claim 5 wherein the toner is applied to the surface of the copy substrate in image config-uration by creating an electrostatic latent image on an insulating surface, electrostatically attracting the toner material thereto in image configuration, and transferring the toner image from the insulating surface to a surface of the copy substrate.

7. The method according to Claim 6 wherein the insulating surface is an electrically photoconductive member and the electrostatic latent image is created by uniformly charging the photoconductive member in the dark, and then.
exposing it to a light image.

8. The method according to Claim 1 wherein the crystalline polymer component of the toner is a poly(hexamethylene sebacate).