CA1176461A - Chemical carbonless copy paper and transfer medium therefor - Google Patents

Abstract

ABSTRACT
An improved chemical carbonless copy paper system including an improved not melt type of coating for CB type pressure sensitive carbonless copy paper having discrete liquid droplets of metallic salt solution electron accepting chromogenic reagent material contained therein.

Description

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~ his invention relates to pressure sensitive information transfcr and duplicating systems and parti-eularly to improvcd chemical type transfer and reproduc-tion media for effecting duplicative image transfer on sheet material in response to selectively applied pressure and to processes for forming the same.

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Pressure sensitive imagè transer media o~
diverse character are widely employed in the information r~cordin~ and duplicating ar~s. Chemical type or so-called "earbonlessl' pressure sensitive trans~er and duplicating systems, wherein a visable image is formed by the selective chemical reaction of two essentially colorless reagents, have been long recognized as a viable expedient for the formation of duplicate copy material. Such systems normally broadly comprise a substrate supported coa~ing that con-tains a ~irst normally inactive chemical reagent material that is selectively transferable ;n response to applied pressure into a reaction providing and color producing relationship with a second normally inactive chemical reagent material contained within or comprising a sccond coating disposed on the surface of an interfacially eontiguous sccond substra~e. Conventionally illustrative G~ SUC~ ctlemical type reproduction systcms are trans~er and duplicating systems where;n the rear surfaco on ono paper sheet substrate is provi~ed wi~ll a coating anct , , , ' ' ~ i , 6~l which sheet is then termed a "CB" ~i.e. coated back) sheet and the front side of that same and/or a separate papcr sheet substrate is provided with a coating which is then termed a "CFB" (i.e. coated front and back) or "CF" (i.e. coated front) sheet, respectively. When the coatin~s on a CB and a CF sheet are placed in in~erfacially contiguous relation and subjected to selec~ively applied pressure, as by the pressure of a stylus or the impact of a typewriter key on the obverse surface of the CB
sheet, the operative and usually colorless chemical reagents in such coatings are brought into co-reactive relationship, as for example on the surface of the CF
sheet, to produce a colored image conforming to the contour of the selectively applied pressure member. c Such chemical type pressure sensitive transfer and duplicating systems are in widespread and expanding use at the present time for the making of multiple copies of selectively recordable duplicative information on sheet m~terial, such as paper and the like, due, at least in part, to the~r basic cleanliness and to the fact that the color producing reagents are inactive until placed into operative co-reactive relationship in response to selective application of pressure.
Although it was early recognized, as for e~ample in the Gill U.S. Patent 1,781,902, that many colorless chemical reagents were capable of pro~ucing a visab].c colorcd i~age upon interreaction therebetwecn, most of the syste~s in wide co~mercial usage at the prcsen~ time employ a colorless organic dyestuff as a dye precursor in encapsulated liquid form distributed within the CB
sheet coating and àn electron accepting material in the CF sheet coating. ~hen such CB and CF sheet coatings are placed in contiguous interfacial relation, the application of pressure effects a rupture of the liquid dyestuff confining capsular elements in the area of applied pressure to effect a release of the dye precursor material and selective transfer of at least a portion thereof into co-reacting and color producing relationship with the electron accepting material in the contiguous coating on the CF sheet wi~h the resulting forma~ion of a duplicative image thereon.
Some early and relatively recent patents that illustratively disclose chemical type or so-called "carbonless" transfer media employing encapsulated dye precursor materials as the chromogenic reagent in the CB
coating and electron accepting materials as the c~romo-genic reagent in the CF coating are USP 2,712,507 (1955) to Green; USP 2,730,456 (1956) to Green et al.; and USP 3,455,721 (1969) to Phillips et al.
. Other more recent patents that illustratively dis~lose the disposition o~ the dye precursor material in the CF coating and encapsulated electron accepting mat~rial in th~ CB coating include USP 3,787,325 (1974) to Roover and USP 3,98~,168 (1975) to Brockett et al.
Such "carbonless" ~ransEer media as presently commercially employed and particularly those that con--3- .

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ventionally employ an encapsulated type vehicle for one of the reactive constituents, mos~ usually an organic dyestuff, a~e not without disadvantage. Amollg the recognized di~advantages of such media are the fact that they are not only relatively expensive, requiring speciali~cd fabricating techniques, but are also unduly pressure sensitive. Such unduc sensitivity often results in undesired premature transfer occasioned by inadvertent dye precursor release and ~ransfer resulting from pressures normally attendant packaging, handling and processing operations, spot coating delineation, printing operations and the like, particularly where multicopy manifolding operations are involved. In addition, such media are inherently subject to a progressive-ly increasing laclc of copy definition as the number of desired copies increases as well as by a fading of the copied image with time~
The recently issued Shackle and Young U.S. Patent No. 4,063,754 discloses the utilization of non-aqueous "hot mel~" coating compositions for CF sheets in a carbon-less transfer system incorporating acid reacting color developing reagent materials. Such patent describes, a~
considerable length, numerous disadvantages attendant employing solvent or water based compositions for effecting the deposition of such carbonless coatings on substrates.
Among such enumerated disadvantag~ are ~he health and fire hazards attendant the release of generally volatile solvent vapors and the expen~iture oE significant amoun~s of energy for the evapo~ation of the water from aqueous -4- ' , ~'7~
solvent systems. In addition, the practical necessities of solvent recovery and the drying of aqueous coating compositions requires relatively complex and expensive apparatus as well as the attendant problcm of solvent safety hazards and disposal of polluted wa~er attendant preparation and clean-up of such aqueous coating com-positions.
A further recently issued paten~ to Shackle and Young's assignee, i.e. U.S. Patent No. 4,112,138j Davis and Shackle for Manifold Carbonless Form and Process for the Production Thereof discloses the utilization of non-aqueous, solvent free "hot melt" coating composltions for CB sheets. The specification of this patent similarly describes, at considerable length, the nurnerous dis-advantages attendant employing solvent or water based compositions for efecting the deposition of carbonless coatings on substrates.
The Shackle and Young patent and the Davis and Shackle patent stress the "non-aqueous" and "solvent ree"
character of the assertedly novel hot melt coating com-positions, apparently based upon the asserted disadvantages flowing from the presence of water both in the fabrication process and in the finished product. The Davis and Shackle patent discloses the preferred use of microcapsular chro~o-genic reagent m~terials in the CB coating although the process clairns are not expressly limited thereto. Although the Shackle and Young patent is expressly directed to a hot melt CF coating, the vehicular form of the acidic electron -5- ~

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accepting type of color developer, i.e. whether micro-encapsulated, capsulated, dispersed or other form, is not particularly specified. It is relatively clear, how-ever, that the described CF product is intend~d for use ~ith CB sheets incorporating an organic dyestuff dye precursor in encapsulated form and, as such, represents an asserted impro~ement for the capsular type systems presently in widespread commcrcial use.
The present day widespread commercial employrnent of CB sheets incorporating encapsulated organic dyestuff dye precursor materials, is, as mentioned above, not without disadvantage, such as undue expense, premature activation, limited reproduction fidelity in multiple CQpies and detrim.ental fading of the reproduced images.
Such disadvantages have been largely tolerated hecause of the absence of a viable commercially acceptable alternative.
As pointed out abo~e, it was early recognized that many chemical reagents were capable of producing visable duplicative images in chcmical trans~er payer usage. The aforementioned Gill U.S. Patent, for example, employed a member of the gallo-tannic acid series as the chromogenic reagent in the CB sheet coating in association ~ith a ferrous or ferric salt as the chromogenic reagent in the CF sheet coating. In contradistinction to the later Shackle and Young and Davis and Shackle's disclosures, this system requires thc presence of solvent aC or in the CF sheet coating ~or the color producing reaction to go fo~ard and hence Gill teaches Che inclusion o~ "a small percentage of glycerine or other non-drying substance, or a hygro-scopic ingredient" in 'the CF shee~ coating. The need for the presence of moisture and the deleterious effects of such moisture on the paper substrate was early recognized in the Gookin et al. U.S. Patent No. 1,950,g82, who provided a water impervious film intermediate the substrate and the CB and CF sheet coatings and included in the latter both ~agnesium chloride as chromogenic reagent material and ~lue or gelatine as moisture retaining material. A
somewhat different approach was followed in Groak U.S.
Patent No. 2,168,098, who disclosed a CB sheet coating com-posed of a hard waxy substance having dispersed therein an admixture of starch, a hydroscopic material, such as glycerine, and a color producing reactive substance. In neithe~ of these approaches, ho~Jever', was water included as a necessary ingredient in the coating composition and thus basically confor~ed in such disclosure and teaching to the later issued Shackle patents.
Some of the aspects of the approach that was early suggested by the Gill, Gookin and Groak patents have recently reappeared in Austrian Patent 3319825 which issued March 25, 1976 ~and apparent counterpart Canadian Patelt 993,656 and West German publication 2,342,596 of April ll, 1974). In these disclosures, an organic dyestuff dye pre-cursor is dispersed in a binder on the CF sheet and used in conjunction with an essentially fulLy transferable C~
~heet coating which incorporates clay materials as the ~lectron acccpting chromogenic reagent material, ~ither .
-7- , alone or in associa~ion with phenolic material and in-organic salts of multival~nt metals. Solvent, water based and hot melt systems are specifically disclosed for the CB sheet coatings. Significantly, however, the hot melt CB sheet coatin~s are all wa~er free, again in conformity with the Shackle teachings.
:A later issued West German patent application Z4 56 083.2 of September 2, 1976 (based on Austrian appli-cation ~1405/75 of February 25, 1974 and its apparent counterpart abandoned U.S. application Serial No. 655,019 cf February 4, 1976 as referenced in U.S. Patent No. 4,096,314) discloses the uti~ization of metal chlorides, preferably in combination with urea or urea deri~atives, as CF sheet ..
coatings in both solvent and aqueous sys~ems. In association therewith, there is disclosed the utilization of organic dyestuff dye precursors dispersed in a hot melt coating medium as the CB coatin~. The preerred CF sheet coatings are identified as those, for a water based coating, that contain zinc chloride and urea and further include a metal stearate.
This invention may be briefly described, in its broad aspects, as an improved chemical type transEer and duplicating sys~em comprising a hot melt type o CB sheet coatin~ con-taining and retaining discrete and selectively constituted liquid electron accepting chromogenic reagen~ material and to methods for ~ormi!~g the same. In its narrower aspects, the subject invention includca a novel hot melt CB coating ccnstituted o~ an inte~ixturc o~ natural and synthetic , ., ., . ~ .,r waxes containing and recaining discrete microscopic drop-lets of a selectively constituted solution of a metallic ehloride, pre~erably zinc chloride in water suitably buffered to minimize, if not effectively neutralize, thc available acidic chloride content thereo~ uniformly distributed therewithin as a color producing reagent. In a still further aspect, the invention includes a com-patible improved CF sheet coating havin~ a plurality of water insoluble dye precursors in solid orm selectively dispersed and distributed throughout an alkaline biased carrier film.
Among the manifold advantages atkendant the practice of the subject invention is the provision of improved low eost carbonless transfer media that serve to provide mark-edly increased numbers of duplicative copies with sharper, more intense and highly smear resistant transferred images.
Additional advantages include compatability with "one time"
earbon papers and standard printing inks; a permitted re-duction in basis weights and the provision of an odorless CB sheet coating that can be reused one or more times, thus permitting retyping on the obverse surface thereof.
Ot~er advantages include the provision of a CB sheet coat-ing that can be readily striped and spot coated and which is recyclable. Still other advantages include the pro-vision o~ a C~ sheçt coa~ing that can be fabricated with minimal energy rcquiremen~s on conventional coating equip-ment requiring minimal capital investmen~. Further ad-vantages includc the provision of transferred images _9_ ~76~L .
that are effcctively stable in character and a system which is operablc at temperatures as low as -30F. Still further advantages include the provision of coa~ings of extended shclf life ~hat are markedly resistant to un-. desired premature activation under conditions of high .temperature. andlor high humidity; that are character-ized by-reduced potential to irritate sensitive sklns and to eorrode iron rollers and other componènts of coating, printing and collating apparatus; coatings that are essentially uncritical as to substrate c~laracter and which are highly resistant to undesired transfer on print-ing-presses, collators and other equipment normally in-eident to manifolding, printing and packaging operations~
A principal object of this invention is the pro-~ Yision o~ improved chemical type pressure sensitive trans-fer and reproduction media, to processes for fabricating the.same and to improved systems employing such media.
. A further principal object o~ this invention is the provision oE an improved hot melt chromogenic reagent con-taining coating composition for CB transfer sheets.
Anothêr object of this invention is the provision of an improved composite ~ax base hot melt type of CB
sheet coating containing discrete drop1ets of a selec~ively constitutcd water solution of a ~etallic chloride suitably buffered to minimize, if not e~fectively neutralize, the available acidic chloride content ~hereof uni~ormly dis-tributed t~iere~ithill as a color producing reagcnt.
A further object o~ thi~ invention i5 the provigion .
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of an improved water base metallic chloride solution for use as electron accepting chromogenic reagent material in carbonless transfer systems that is efectively non-corrosive and non-irritating and which is highly resistive, when dispersed in a hot melt carrier vehicle, to undesired premature image actuation under conditions of high temper-ature and/or high humidity.
A still further object of this in~ention is the pro-vision of an improved wacer base metallic chloride soluLion for use as electron accepting chromogenic reagent material in carbonless transfer systems.
Other objects and advantages of ~he subiect in-vention ~ill become apparent from the following portions of this specification which describe, in accord with the mandate of the patent statutes, the principles of the in-vention and best mode presently contemplated by the invent-ors for carrying out said inventions.
Figure 1 is a schematic representation of chemical type pressure sensitive transfer and reproduction media incorporating the principles of this invention; and Figures 2a and 2b are photomicrographs (4200X and 14000X) of an imp`roved hot melt CB coating formed and constituted in accordance with the principles of this invention.
Referring to the drawings and initially to Figure 1, there is provided ~n illustrative set o~ chemical type or carbonless transfer and reproduction media fabricated in accord with t~e principles of the inven~ion. As there shown, such set includes a CB sheet comprising a first planar substrate 10, suitably a paper sheet or web, having a thin solidified hot melt CB coating 12, constituted as hereinafter described, disposed on the undersurface there-of. Adapted to be positioned in interfacially contiguous relation-with the CB coating 1~ on the underside of substrate 10 is a CF sheet coating 16 disposed on the upper surface of a second paper sheet substrate 14.
Such substrate 14 may have its undersurface coated with a CB coating 12 and thus constitute a CFB sheet, or may have an uncoated undersurface and thus constitute a CF sheet.
A~ternatively, and illus~ra~ively adapted to be disposed in interfacially contivuous relation with either a CB
coating 12 on the underside of the "CF,Bi' sheet 14 or with a CB coating 12 on the underside of the "CB" sheet 10, is a separately illustrated "CF" sheet havin~ a CF coating 16 disposed on the upper surface of a third substrate 18. As will be apparent to those skilled in the art, any number of intermediate CFB sheets or webs l~ may be interposed in stacked relation to form a multilamina transfer and reproduction system. Likewise, such multilamina set may include one time carbon transfer sheets interposed with uncoated or CB coated sheets or webs in a manifold arrange-ment in accord with the dictates of the user thereof.
The novel and improved hot melt CB shee~ coa~ing broadly comprises tho resulting set or solidi.fied film from an applied and su~sequontly cooled emulsi~ied liquid inter~ixture o a meltod lo~ oil content wax carrier vehicle, .

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pre~erably of composite character, a melted synthetic flow wax and dispersant and a chromgenic reagent solution of a metallic chloride, pre~erably æinc ch~oride, dissolved in water and suitably buffered to minimize, i not effect-ively neutrali~e the available acidic chloride content there-of; said emulsified intermi~ture also desirably having uniforTnly dispersed therein small but critically limited amounts of a resinous film forming agent to promote film hardness and toughness, an isolating agent to minimize, if not effectively preclude, undesired transfer of the coating or portions thereof in response to unintentional pressure application and an opacifier-filler to reduce the gloss of the finished copy and preserve the appearance of the substrate.
In its narrower aspects, the subject inventiOTI
iTlcludes a hot melt CB sheet coating composition formed of about 35 to 75 percent of a meltable low oil content synthetic or naturally derived hard wax vehicle; at least 1 to about 15 percent of a chemicaLly modi~ied wax-like material having properties of a fl.ow agent, dispersant and emulsifier; and at least 10 to about 35 percent oE
a chromogenic reagent component in the form of a Lewis acid, desirably an electron accepting hygroscopic, if not actually deliquescent, metalLic salt together with an amount of water neccssary to desirably Eorm a relatively concentrated solution thereo.
Optionally but desirably included in such CB
8heet coa~ing composition ~or provision of an cnhanced '76~6~L

co~nercially attractive prodtlct are one or more of the following additional constituents. One such optional constituent comprises a film forming agent to encourage the formation of a harder and tou~her surface film after setting and to thus minimi~e pre~ature actuation of the color producing reaction. This film forming agent must be non:reactive with the chromogenic reagent and may vary in amount from a minimum of about 2~o up to an amount that deleteriously effects ~he Elow characteristics of the mix. Another such optional but yet desirable con-stituent comprises an isolating agent that is essentially incompatible with the wax vehicle when solidified and which serves to provide desirable surface characteristics to the resultant film, s~lch as ~o minimize, if not effect-i~ely preclude, undesired transfer of the coating or portions thereof in response to unintentional pressure application. The isolating agent may vary in amount ~rom a desirable minimum of about 2% up to a maximum of about 20%. A .still further optional but desirable constituent is an opacifier-filler to enhance the appearance of the coated surface of the CB sheet, such as by reducing the gloss thereof. As is well known in this art, such opacifier-filler may vary in amount required to provide a desired appearance, typically about 5%, and m~yincludc titanium dioxide, various non-acidic high brightness clays, litho-pone or other recognized matcrials.
The meltable wax véhicle may s~litably comprise any o~ the low oi.l content paraffin waxe5, microcrystalline ~76~6~
waxes, carnauba, Montan or other conventionally employed low oil content vegetablc, synthetic or mineral derived hot melt wax type carrier vehicles. The presently pre-fexred meltable wax vehiclc, a composite made up of about 3 ~o 4 parts of a low oil content paraffin wax, intermIxed with abouc 1 part or less of carnauba wax. A presently preferred paraffin wax is a low oil content, high melting point, fully refined paraffin wa~, suitably Pacemaker 53 . .
as manufactured and sold by Cities Service Oil Co. of Tulsa, Oklahoma. Such wax has the follo~ing properties:
- Melting point, ASTM, F 143-150 Melting point, AMP 146-153 Oil Content, Wt. % max 0.25 Odorless Viscosityr cs at 210F 5.5 Needle penetration at 77F 13 Flash point F 485 Other suitable low oil content hot melt ~7ax carrier vehicles include alpha ole~inic waxes, suitably ~6317 Synthetic Wax as available from Moore & Munger Inc. of Fairfield, Connecticut; microcrystalline ~ax, suitably 195 Be Square l~hite, available from Petrolite Corporations Bareco Division; carnauba wax, suitably Brazilian Re-fined available from Baldini & Company of Milburn, New Jersey.
Moore & ~unger's ~6817 Synthetic Wax has the followlng propertics:

-lS-~ /r~ V~r k .

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Con~calin~ Point, F., Needle penetration, mm/10, ASTM D 1321 77F. 14 Viscosity, Saybolt (a) 210F.
(SUS), ASTM D 2161 52 Viscosity, Kinematic (a~ 210F.
(Cs.~. ASTM D 445 8 C~lor, Saybolt, ASTM D 156 +4 . Flash Point, F. (COC) 510 Barecois 195 Be Square White microcrystalline wax has the iollowin~ properties:
Mel~ing Point, F. ASTM D 127 193/198 Penetration (a) 77F. ASTM 6~'7 . Color ASI~I D 1500 0.5/0.5+
A preferred carnauba wax is Baldini's Brazilian Refined Carnauba wax that is possessed of the following properties:
Melting Point, min., F. 180.5 Acid Number minimum 4.0 maximum .10.0 Saponiication Number minimum 78.0 . maximum 88.0 The meltable chemically modified wax-like material having the desired properties o a flow agent, dispersant and emulsifier most suitably comprises a material of the type di.sclosed i~ U.S. Patent No. 3,941,608. Other suitably chemically modiEied wax materials havin~ ~he - somewha~ similar propcrties include modiEied synthetic waxes as discolsed in U.S. Patent Nos. 2,890,124, 2,890,125 .

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snd 3,163,548. ~ pre~erred commercially available wax-lilce material formulated in accord with U.S. Patent No. 3,941,608 i~ #731S wax as so~d by Moore & Munger, Inc., of Fairfield, Connecticut. Such #7315 wax has the following general proper~ies:
Penetration Hardness (FLP~I-225 Typical Melting Point ~Fisher Johns)144Typical Acid Nu~ber (AST~ D 974)Z Typical Another suitable wax-like material having somewhat similar properties as the foregoing suitably comprises an amide of a fatty acid, such as Armid HT as available from Axmour Industrial Chemical Company. Such Armid HT is possessed of the following properties-Amide /O ~min.)90 lodine value minimum maximum 5 Free fatty acid %
minimum maximum S
Melting Point, C.
minimum 98 maximum 103 The resinous film forming agent serves to enhance the formation of a relatively hard and tou~h coating to minimize undesired transEer oE reagent material across the CBtCF interEace in the absence of intentional posi.tive pressure application. A suitable film Eorming agent, which ~ust be non-reactive with the chromogenic reagen~ component, f ,. . .
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desirably comprises a relatively low melting point ethylene-vinyl acetate copolymer, such as AC-400~ as manufactured and sold by Allied Chemical Corporation.
Such resinous film forming agent has the following properties:
Softening Point (~SI~ E-28) 204F.
Harc~ess dmm (ASTM D- 5) 9.5 Density 8/cc (ASTM D-1505) 0.92 Viscosity (284F - Brookfield) 550 Another suitable film Xorming agent comprises oxidized polyethylene, suitably AC-629~as manufactured and sold by Allied Chemical Company. Such film for~ing agent has the following properties:
... . .. . . . . .
Softening Point 214hF.
Hardness 5.5 Density g/cc 0.93 Average Viscosity CPS 284F. 160 Acid Number 15 The isolating agent cooperatively functions as blooming agent to provide a lubricating and barrier sur-face to the solidified coating. Such isolating agent, which should be essentially incompatible with the wax carrier vehicle when solidi~ied, so as to be selectively effective at the exposed surface, sui~ably comprises a small amount of stearic acid, desirably ~YSTRENE 9718 as manuactured and 301cl by the Humko Chemical Company. Zinc stearate may al~.o be employecl.
~ he opacifler-~iller, which cosme~ically scrves ~l j/r~ i, k .

both to reduce the gloss o the finished coating and to preserve ~he appearance of the substrate, suitably com-prises iinely~ divided titaniu~ dioxide such as UNITAN ~0-110 as manufactured and sold by American Cyanamid Company. This material has a specific gravity of about 3~9 and is so fin21y divided as~to leave only about a 0.10% residue on a 325 mesh screen.
The chromogenic reagent component prcferclbly com-prises a concentrated water base solution of zinc chloride as the electron accepting metallic chloride, suitably buffered to minimize, if not effectively neutralize, the available acidic chloride content thereof. Such solution is preferably made up o about 2 to 4 parts o zinc chloride with about l part of wa~er and which approaches a saturated solution.
Other chromogenic reagent components comprise concentrated water base solutions of metallic halogen salts such as stannous chloride, ferric chloride, lithium bro-mide and nickel chloride.
While unbuffered solutions of zinc chloride as the chromogenic reagent have provided highly effective image formation in transfer coatings as formulated in accord with the foregoing disclosed formulations, such have been subject, under extreme climatic conditions of high temperatures and/or high humidity, to tlle apparent genera-tion and emanation of hydrogen chloride. Although the qu~ntities o~ h~drogen chloride so generated, appear to be minimal, even under such ex~reme climatic conditions, i~ trqJ~ f,~`k the apparent emanation ~hereof ~rom the applied coating has resultcd in varying degrees of premature actuation of the dye precursors over the entire surface of an inter-facially contiguous CF coating and, depending on the ambient climatic conditions, in varying degrees of actuation of such CF sheet. Such premature ac~uation is, of course, highly undesirable, as is the generation of hydrogen chloride with its potential to irritate sensitive skins and to corrode iron rollers and other components o~
the processing equipment under any set of ciimatic con-ditions.
In order to neutralize, if not actually prevent, the generation and emanation of such hydrogen chloride, a s~all amount of a neutralizing ammonium salt, suitably ammonium carbonate or ammonium bicarbonate, is dissolved in the zinc chloride solution. For à concentrated solution of about 2 parts of zinc chloride to 1 part of water, about .1 part of such neutralizing ammonium salt is generally satisfactory. Experience to datc has generally indicated that the addition of about 2 to 4% of a~monium carbonate to ~inc chloride solutions oE the type herein disclosed results ir. effective avoidance o~ the above problems in an improved prod~lct .
~ hile the mechanics o~ the reaction process are not fully understood it is surmised that the ammonium salt operates to neutralixe or othe~ise reduce the available act~ve or acid chloride ion content and to thus preclude its association with available hydro~en ions. Also the possible availability oE a~nonia in both the liquid ~md gaa~ous phase may also contribute to thc ncutrali~.ation oE hydro~en chloride in both such phases.

- 2 Apart from the foregoing, the additions of such neutralizing ammonium salt has provided some totally un-expected and,-as yet, unexplainable advan~ages and results.
Such unexpected results are a bleaching and a marked in-crease in the hardness of the solidified CB hot melt coat-ing. Such increase in hardness not only functions to minimize pick oif on processing components, reduces the tendency to smear and provides sharper copy, but also per-mits of significant reduction in the quantity of carnauba wax that is otherwise desirably included ~herein. Carnauba wax is not only one of the more cost significan~ components of the coating bu~ is also only obtainable from a foreign source of supply who controls the ever increasing price thereof. .
The unexpected bleaching action also enhances the appearance oE the product through an enhancemerlt of the "whiteness" of the coating.
A presently preferred hot melt CB sheet coating broadly comprises the resulting set or solidified film from an applied and subsequently cooled emulsified liquid intermixture of about 50-60% of a melted low oil content composite wax carrier vehicle, made up of about 3 to 4 parts of a low oil content para~fin wax intermixed with about 1 part of carnauba wax; about 2 ~o 5% of a chemi-cally modified synthetic 1OW wax and dispersan~ and about ~5-35% of a chromo~enic rea~ent solution of at least 2 parts of zinc chloride dissolved in about 1 part oE water buffered by a small amount of ammonium carbonate as out-. -21-.

, lined above; said emulsified intermixture also desirably having uniformly dispersed therein about 3 to 10% of a resinous film forming agent to promote film hardness and toughness, about 3-10% of an isolating agent to minimize, if not effectively preclude, undesired transfer of the coating or portions thereof in response to unintentional pressure application and about 5% of an opacifier-fil.ler to reduce the gloss of the finished copy and preserve the appearance of the substrate.
In the production of the above described preferred CB sheet coating composition in accord with the principles of this invention, the requisite amounts of the electron accepting metallic chloride, preferably ZnC12, and water are int`ermixed in a reaction vessel, suitably a stea~
Jacketed ke~tle having a 210F temperature settin~, to form a hot concentrated solution thereof. To such solu-tion is then added the neutralizing ammonium salt, preferably ammonium carbonate. To such elcvated tempera-ture and now neutralized chromogenic reagent solution, the requisite amounts of melted low oil content paraEin wax and carnauba wax components of the composite wax carrier vehicle are added and thoroughly intermixed as by use of a high speed dispersing blade for about 10 Minutes or longer.
To the intermixture as so constituted, the flow wax and dispersant constituent and the polyethylcne filming agent and stearic acid isolating agent constituents are added in ~olid form with continual mixing uncil such constituents are completely melted and dissolvcd in the coN~osite wax carrier vehicle. When so melted and dissolved the opa-ci~ier-filler, pre~erably titanium dioxide is added and the entire mass thoroughly mi-~ed at high speed for 30 to 40 minutes to form a selectively constituted liquid hot melt emulsion.
The resulting liquid hot melt emulsion is readily and selectively applied in the form of a thin film, as fo~ example at a coating weight of as low as 2 grarms/square meter, by conventional means to the surface of a substrate, such as a sheet or web of paper or resinous film. The conventional coating means may comprise a print type coater, a roll coater or the like. The so coated substrate is then passed over a chill roll or the like to rapidly solidify or set the applied emulsified coating composition.
In contradistinction to the systems of the prior art which were operatively dependent upon an external water source (often humid air) to provide the necessary ionized zinc chloride to react with the dye precursor, the system of the present invention contains and retains water as an operative element in discrete droplet liquid form within thP solidified CB film and thus effects the selective trans-fer of ionized zinc chloride as the operative entity.
Photomicrographs of coakings formulated in accord with the principles of this invention are shown in Figures 2a and 2b at magnifications o 4200X and 14000X respectively.
These photomicrographs clearly depict the presence of dis-crete, microscopLcally sized zinc chloride an~oni~n salt solution globules distributcd throughou~. the coating. Most , '~ f.

. of such globules arc less than 1 micron in diameter with the grcat majority thereof falling between .25 and .75 mi-crons. Such photomicrographs further show that such zinc-chloride solution globules peripherally incorporate..an interface layer or the like that differs, at least in some physical respects from both the 7inc chloride solution globules and from the surrounding solidified wax material as evidenced by the clearly different refractive indices involved.
To the above ends, the foregoing described method of formulation provides a selectively constituted emulsion in which zinc chloride solution entities are thoroughly dispersed within the film. The basic hygroscopic, if not actual deliquescent, properties of 7inC chloride and the nature of the resultant film serve to minimize, if not . effectively prevent, water loss in storage with enhanced operating life for the product.
Another factor which contributes to the retention of the dispersed zinc chloride solution in discrete liquid globular form within the C~ film is the enhanced emuls-ification obtained through the use of an essentially alkaline and amino containing dispersant - flow wax con-stituent in association with the relatively high acid number wax and film forming components.
. .By way of further examples the following formula-tions have provi(led CB sheet coating having in varying degree, the manifold advantages earlier set forth.

. . EXAMPLE I
%
, Paraffin Wax . 45.0 7315 Wax 2.0 AC-400 Polyethylene 5.0 Stearic Acid 3.0 Titanium Dioxide 5.0 Zinc Chloride 30.0 Water 10.0 EXAMPLE II
.
Paraffin Wax 41.0 7315 Wax 2.0 AC-629 Polyethylene 7.0 Titanium~Dioxide 5.0 Zinc Stearate 10.0 Zinc Chloride 30.0 Water 5,0 EXl~PLE III
Parafin Wax . 35,0 AC-400 Polyethylene lO.0 Zinc Chloride. 20.0 Nater 10.0 7315 Wax 10.0 Stearic Acid 10.0 Titanium Dioxide s,o .

EXAMPLE IV

Paraffin Wax 55.0 Carnauba Wa`x , 20.0 ~inc Chloride l5.0 Water 5.0 7315 Wax . 2.0 Stearic Acid 3 0 EXAMP~E V
Paraffin Wax lO.0 ~icrocrystalline Wax . 3b.0 Stannous Chloride 30.0 Water lO.0 7315 Wax 3,0 Stearic Acid . 7.0 Titanium Dioxide lO.0 EXA~IPLE Vl Carnau~a Wax lO.0 Alpha Olefin Wax 40.0 AC-629 Polyethylene . 7.0 Ferric Chloride 20.0 Water lO.0 73~5 Wax j 3,0 Stearic Acid 5.0 T.~tan~um Dioxidc 5.0 , . -2~- .

By way of further preferential example, the above formulations, when buffcred to minimize, if not effecLively neutralize, the available acidic chloride content thereof, are modified as follows:

. EXAMPLE IA
%

Paraffin Wax 42.G
7315 Wax 2.0 AC-400 Polyethylene 5.0 Stearic Acid 3.0 Titanium Dioxide 5.0 Zinc Chloride 30.0 Ammonium Carbonate 3.0 Nater - 10.0 EXAMPLE IIA

Paraffin Wax 38.0 7315 Wax 2.0 AC-629 Polyethylene 7.0 Titanium Dioxide 5.0 Zinc Stearate lO.0 Zinc Chioride 30.0 Ammonlum Bicarbonate 3.0 ~J~ter 5-~17~6~ `
EXAMPLE IIIA .
X
Paraffin Wax 33.0 AC-400 Polyethylene . lO.0 Zinc Chloride 20.0 Al~nonium Carbonate 2.0 `Uater 10.0 7315 Wax 10.0 5tearic Acid 10.0 ~itanium Dioxide 5.0 i, ~
1~76~
E~MPLE IVA
X
Paraffin Wax 51.0 Carnauba Wax 20.0 Zinc Chloride 15.0 Ammoniu~ Carbonate 4.0 Water 5-0 7315 Wax 2.0 Stearic Acid 3.0 ~X~PLE VA
Paraffin Wax 9.0 Microcrystalline Wax 28.0 Stanno`us Chloride 30.0 Ammoniu~ Bicarbonate 3,0 Water 10.0 7315 Wax 3.0 Stearic Acid 7.0 Titanium Dioxide 10.0 : EX~MPLE VIA
Carnauba Wax . 8.0 Alpha Olefin Wax 38.0 AC-629 Polyethylene 7.0 Ferric Chloride 20.0 Ammonium Carbonate 4.0 ~ater 10.0 7315 Wax \ 3.0 Stearic Acid 5.0 Titanium Dioxide 5.0 ~ .

The follo~ing formulations h.ave providcd highly preferred CB sheet coatings: ~

EXAMPLE VII

Paraffin ~ax 39.0 C~rnauba llax 14.~
Zinc Chloride . 20.0 Water . . 10.0 7315 Wa~ 2.0 AC-400 Polyethylene 5.0 Stearic Acid 5.0 Titanium Dioxide 5.0 EXAMPLE VIIA
Paraffin Wax 36.0 Carnauba Wax 14.0 Zinc Chloride 20.0 Water lO.0 Ammoniu~ Carbonate 3.0 7315 Wax 2.0 AC-400 Polyethylene 5.0 Stearic ~cid 5.0 Titanium Dioxide 5.0 The foregoing hot melt CB coatings may be employed with efectively all CF coatin~s that incorporate an organie ~yestuf or other chromo~enic reagent color precursor that will react with ~.he ionizcd electron accepting metallic salt when the latter is introduced into operative relation there-with. By way of urther example, satisEac~ory results have been obtained when such CB sheets are used with CE coating compositions consti~uted as hereinafter dlsclosed.

f 7~
In its broad aspects, suitable CF coa~ings com-prise the solid residue of an applied alkaline homgeneous mixture of an evaporable liquid carrier, a chemically neutral or alkaline resinous binder, an o~ganic color precursor and an opacifier-filler. Such solidified CF
coatings are further characterized by the presence oE
the organic color precursor in solid form and which is in-soluble in the liquid electron accepting chromogenic reagent soiution contained in the CB coating. Optionally but desirably included therein is a dispersant to assure the uniform dispersion of the color precursor throughout the mix and a thickener to provide the requisite viscosity properties to facilitate the coating of the mix in accord with the particular requirements of the ~oating equipment employed.
The evaporable liquid vehicle may comprise water or numerous organic solvents or mixtures thereof such as ethyl alcohol, meth~yl ethyl ketone, toluene and the like.
Likewise, the opacifier-fiLler may constitute titanium dioxide, ~inc oxide, lithopone, calcium carbonate or neutral clays or intermixtures thereof.
. A preferred CF coating employs water as the evapor-able liquid vehicle and generally comprises the solid residue of an applied water based intermicture, such inter-mixture comprising about 3 to 20 parts of a chemically neutral or allcaline resinous binder, sui~ably polyvi.nyl acetate; about 10 to 40 parts of an opacifier-filler; abou~
.5 to 5 parts oE a water insoluble acid reactable orgallic , .

6~
color precursor ~ixture and about 30 to 70 parts of water.
Althou~h ~lany acid reactable organic color pre-cursors can be employed, the presently preEerred color precursor comprises a mixture of water insoluble, alka-line stable and acid sensitive organic dyes~uffs to pro-duce a dark light stable and lasting image. Desirably included in such preferred mi~ture is crystal violet lac-tone, suitably about 0.7 parts thereof, which provides for rapid reaction and image production, together with about an equal amount of a blue/black dye precursor, and lesser amounts of a red color dye precursor, suitably about 0. 2 parts thereof and a blue dye precursor, suitably about 0.4 par~s thereof to provide for desired image color and a high degree of light stability and increased use~ul life.
A suitable crystal violet lactone comprises Brilliant Violet Leuco (CVL) as ~anufactured by Hilton Davis Chemical Co. This dye precursor is believed to be 6-dimethylamino-3,3-bis(p-dimethyla~inophenyl)phthalide having a molecular formula oi C26H29N302 and a molecular weight of about 415.5. The blue/black dye precursor suitably comprises CopykeM VI as manufactured by Hilton Davis Chemical Co. and the blue dye precursor suitably coMprises Reacto Blue B as manufactured by BASF.
~ he naturc of the binder is not attended with any par~icular degree oE criticality as long as it E~mctions as a blnding agcnt for the opacifier-~iller and the color precursor, with both of the latter being in solid fonm.
, .

, ~7~
.. . .
A preferred ~esinous binder material comprises polyvinyl aeetate emulsion, suitably Airflex~456 as manufaetured by Air Produets & Chemieals Company. Another suitable binder material comprises an acrylie emulsion, for example Rhople~
P-376 as manufactured by Rohm & Haas Corp.
The opaeifier-filler, whieh serves both to enhance th2 appearanee of the coating and to eooperate in the uniform distribution and spaeed separation of the solid color precursor in the CF eoating ~ust also be of neut~al or alkaline eharacter. Such filler may suitably comprise calcium carbonate such as Albaglos~as manufactured by Chas. Pfizer & Co. This material has a pH o 9.4, a spPeifie gravity of 2.7 and an average partiele size of about .75 microns. Another suitable opaeifier-filler is ~NITANE 0-110 titanium dioxide as manufactured by the Ameriean Cyanamid Company. This material has a ~inimum TiO2 content of 99%, a pH of about 7.7 and a specific gravity of about 3.9.
A presently preferre~ dispersant comprises sodium salt of polymerie earboxylic aeid,-sueh as Tamol 850 as manufactured by Rohm & Haas Company of Philadelphia, Pa.
This material has a pH of about 9.8 and a specifie gravity at 25 of 1.19.
In the production of the above described receptor coating for the CF sheets, a wa~er base intermixture of preemulslEied polyvinyl aeetate, the dispersant and ~he opaeifier-filler, suitably TiO2, is Eonned with eontinuous agitation to e~eet a thorough dispersion o the filler and ~ 7~r~7J~ h7~Yr/<
.

, ~'7~

binder constituents therin. Into this mixture is intro-duced the organic dyestuff dye prccursor chromogenic re-agent component, again with continuous agitation to effect a complete and uniform dispersion of the dye precursor particles within the liquid intermixture.
The resultant e~ulsion-dispersion is readily and selectively applied by conventional coating equipment in the form of a thin film to the surface of a substrate, such as a sheet or web of paper or of resinous film.
I~hen so applied, the water is then evaporated from the mixture and residuP constitutes the improved CF coating.
By way of specific example, the following fo{mula-tions have provided a CF sheet coating possessing the ~arked advantages hereinbefore set forth~

EXA~IP~E VIII
Wa~er 46.3 Dispersant (Ta~ol 850) 0.2 Titanium dioxide 5.5 Calcium carbonate 26.8 PolyvinyLacetate emulsion 19.2 (52% solids) Crystal violet lactone 0.7 Red dye precursor 0.2 Blue/black dye precursor 0.7 Blue dye yrecursor 0.4 , t~-a~ irk .

~76~

EXA~IPLE IX
Water ~9.0 Disporsant (Tamol~850~ - 0.3 Calciu~ carbonate 17.0 Acrylic emulsion - 13.0 (50% solids) Crystal violet lactone 0.5 Red dye precursor 0.2 Such CF shee~ coating may also comprise the solid residue of an applied intermix of an evaporable solvent earrier, suitably 35 to 75 parts of 95% ethyl alcohol and at least about 3 parts of methyl ethyl ke~one, having dis-solved therein at least about 5 parts of a binder, suitably polyvinyl acetate. Added thereto is about O.Z parts of a dispersant and about O~la/o oE dry potassium hydroxide to pro~ide an alkaline cast to the mix and to minimize in-advertcnt color reactions on the CF coated sheet. Also included in the mix is about 5 parts of an opaci~ier-filler, suitably finely divided titanium dioxide and about ~5 parts of calciu~ carbonate. Starch, such as corn starch, may also be included, in lieu of or in addition to, portions of opacifier-filler to serve as a spacin~ agent. While any suitable chromogenic reagent material ~ay be employed, satisfactory results have been obtained throu~h the i~-eorporation therein o~ small but critical quantities of a primary organic dyestuff dye precursor, such as about .5 to 2 parts of crystal violet lactone. Prcferably, additional organic dyestuEE dyo precursor materials serving as color modifier~ ancl inLenslficrs may al50 be includecl in the .

-3~-;~ tr 4~ rk .

~ r 764~
ehromogenie reagent material, sui~ably red and blue/blaek eolor organic dyestuff dye precursors.
A preferred binder material which is readily soluble in the above described composite evaporable solvent earrier comprises polyvinylacetate, suitably Vinae~B-15, as manufaetured by Air Products & Chemieals Company.
A presently preEerred dispersant comprises sodium salt of polymerie earboxylic acid sueh as Tamol 731 as ~anufactured by Rohm & Haas Company of Philadelphia, Pa.
The ehromogenic material may be of conventional eharacter and a presently preferred material comprises "Brilliant Violet Leuco" (CVL) as manufactured by the ~ilton Davis Chemieal Company of Cineinnati, Ohio.
In the produetion of the above described receptor eoating for CF sheets, a liquid mixture is first formed by (a) intermixing the ethyl alcohol and ~ethylethylketone solvents; then (b) the polyvinyl aeetate binder material, the dispersant, the potassium hydroxide (to cast the pH
of the solution to the alkaline side) are added with eontinuous agitation until completely dissolved after ~hich (c) the organic dyestuff dye precursor ~aterials are added with continued stirring until dissolved. To the above liquid mixture is then added the requisite amounts o~
ealeium earbonate and the titanium dioxide opacirier-filler. Such addition should be aceompnnied by eontinuo~ls ~tirring of sueh eonstituents in the liquid vehicle to obtain a uniform dispersion thereoE.
The above deseribed organic dyestuEf color preeursor ~36-t, ~ ? ~ ~r l~

mat~rials are stable in alkaline media and, within theabove formul~tion ranges, such coating composition can be used to coat most all paper substrates without any effect on the reaction time or thc density of the image produced when using -~he CB sheet coatin~s described above.
By way of specific example, the following formula-tion ha~ provided a satisfactory CF sheet coating.
, ' EXAMPLE X
. Raw Materials .
Ethyl Alcohol (95Zo) 5~-3 Polyvinyl Acetate Beads 15.0 Potassium ~ydroxide Flakes 0.1 Tamo ~731S.D. Dispersant 0.2 Titanium Dioxide . 5.0 Cal~ium Carbonate 15.0 ~ethyl Ethyl Ketone 10.0 Crystal Violet Lactone (CVL3 1.2 Red Color Precursor 0.6 Blue/Black Precursor 0.6 A further example of a satisfactory GF coating is , EXAMPLE XI
~et Bases /0 Ethyl Alcohol (95%) 40.0 Polyvinylacetatc 10.0 Tamol~?31 ~ispcrs~nt 0.
Potassium Hydroxide ~o.5 -~-t~ V~ k 7~
Titanium Dioxidc 17.0 Calcium Carbonate ~ 7.0 Corn Starch . 10.0 Methyl Ethyl Kctone 15S~
Crystal Violct l.actone (CVL) ~.2 Secondary Dye Precursors (mixed~ 0.1 Eaeh of the foregoing CF coating formulations results in a CF coa~ing layer of neutral or alkaline character, of acceptable appearance and having the color precursor chromogenic reagen-t homogeneously distribu~ed .. . . . .
there throughout. Such coatings are singularly abrasion and odor free and have been formed of coating weights as low as .2 grams/square meter. When used wi~h CB coatings of the type herein described the image fontting reaction proceeds ~ithout the color precursor chromogenic reagent material in the CF coating being solubilized and ionized the liquid electron accepting chromogenic r~agent materîal emitted from the CB coating.
Having thus desribed our invention, we claim:

, .

Claims (24)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A pressure sensitive chemical type transfer medium comprising:
planar sheet material having an at least partially transferable coating layer disposed on one surface thereof con-stituted by the solidified residue of an applied hot melt low oil content wax base emulsified liquid film including a chemically modified wax-like material having flow agent and dispersant properties homogeneously intermixed therewith and having discrete liquid droplets of a water base solution of an ionized metallic halogen salt electron accepting chromogenic reagent material distributed therein.

2. A pressure sensitive chemical type transfer medium as set forth in Claim 1 wherein:
said water base solution of an ionized metallic halogen salt electron accepting chromogenic reagent material is selective-ly displaceable form said coating layer in response to application of pressure to the obverse surface of said planar sheet material.

3. A pressure sensitive chemical type transfer medium as set forth in Claim 1 wherein:
the majority of said discrete droplets of the water base solution of an ionized metallic halogen salt electron accepting chromogenic reagent material are homogeneously distributed within the solid coating layer and the majority of which are less than 1 micron in diameter.

4. A pressure sensitive chemical type transfer medium as set forth in Claim 1 wherein:
said liquid electron accepting chromogenic reagent material is a concentrated water base solution of a hygroscopic metallic halogen salt selected from the group consisting of zinc chloride, stannous chloride, lithium bromide, ferric chloride and nickel chloride.

5. A pressure sensitive chemical type transfer medium as set forth in Claim 1 wherein:
said discrete droplets o-f liquid electron accepting chromogenic reagent material consists of a concentrated water base solution of zinc chloride.

6. A pressure sensitive chemical type transfer medium as set forth in Claim 4 wherein:
said concentrated water base solution of a metallic halogen salt includes an acidic halogen neutralizing agent therein.

7. A pressure sensitive chemical type transfer medium as set forth in Claim 5 wherein:
said concentrated water base solution of zinc chloride further includes a relatively small amount of an acidic chloride neutralizing agent selected from a group consisting of ammonium carbonate and ammonium bicarbonate

8. A pressure sensitive chemical type transfer medium comprising:
a planar sheet material having an at least partially transferable coating disposed on one surface thereof, said transferable coating layer constituted by the solidified residue of an applied hot melt emulsified liquid film comprising a low oil content meltable wax carrier vehicle and a chemically modified wax like flow agent and dispersant homogeneously intermixed therewith, and discrete droplets of a concentrated water base solution of ionized hygroscopic metallic halogen salt electron accepting chromogenic reagent material selected from the group consisting of zinc chloride, stannous chloride, lithium bromide, ferric chloride and nickel chloride homogeneously distributed therewithin..

9. A pressure sensitive chemical type transfer medium as set forth in Claim 8 wherein:
said low oil content meltable wax carrier vehicle is compositely constituted of a major portion of paraffin wax and minor portion of carnauba wax;
said hygroscopic metallic halogen salt is zinc chloride;
and said medium further includes an opacifier and a resinous film forming agent homogeneously intermixed in said hot melt emulsified liquid film.

10. A pressure sensitive chemical type transfer medium as set forth in Claim a wherein said chemically modified wax-like flow agent is selected from the group consisting of the product obtained by reacting a selectively oxidized linear unsaturated hydrocarbon having a terminal carbon double bond with ammonia or a primary organic amine and further reacting the resulting modified hydro-carbon with an isocyanate; the product obtained by reacting an oxidized microcrystalline wax with an isocyanate, the product obtained by reacting an oxidized non-benzenoid wax with an isocyanate; the product obtained by reacting an oxidized mycrocrystalline wax with ammonia or an amine and further reacting the resulting modified hydrocarbon with an isocyanate and the product obtained by reacting an oxidized non-benzenoid wax with ammonia or an amine and further reacting the resulting modified hydrocarbon with an isocyanate.

11. A pressure sensitive chemical type transfer medium as set forth in Claim 9 wherein:
said concentrated water base solution of zinc chloride further includes a relatively small amount of an acidic chloride neutralizing agent selected from a group consisting of ammonium carbonate and ammonium bicarbonate.

12. A pressure sensitive chemical type transfer medium comprising:
a planar sheet material having at least partially transferable coating layer disposed on one surface thereof;
said transferable coating layer constituted by the solidified residue of an applied hot melt emulsified film consisting of about 35 to 75% of a meltable low oil content hard wax;
at least 1% to about 15% of a chemically modified wax-like material having flow agent and dispersant properties and about 10 to 35% of an ionized electron accepting metallic halogen salt chromogenic material selected from the group consisting of zinc chloride, stannous chloride, lithium bromide, ferric chloride and nickel chloride dissolved in water to form a concentrated solution thereof.

13. A pressure sensitive chemical type transfer medium as set forth in Claim 12 wherein:
. said meltable low oil content hard wax is compositely constituted of a major portion of a wax selected from the group consisting of paraffin wax, microcrystalline wax and alpha olefin wax;
said chromogenic material is a concentrated water solution of zinc chloride containing a relatively small amount of an acidic chloride neutralizing agent selected from the group consisting of ammonium carbonate and ammonium bicarbonate.

14. A pressure sensitive chemical type transfer medium as set forth in Claim 12 wherein said chemically modified wax-like flow agent is selected from the group consisting of the product obtained by reacting a selectively oxidized linear unsaturated hydrocarbon having a terminal carbon double bond with ammonia or a primary organic amine and further reacting the resulting modified hydrocarbon with an isocyanate the product obtained by reacting an oxidized microcrystalline wax with an isocyanate, the product obtained by reacting an oxidized non-benzenoid wax with an isocyanate; the product obtained by reacting an oxidized microcrystalline wax with ammonia or an amine and further reacting the resulting modified hydrocarbon with an isocyanate and the product obtained by reacting an oxidized non-benzenoid wax with ammonia or an amine and further reacting the resulting modified hydrocarbon with an isocyanate.

15. A pressure sensitive chemical type transfer medium as set forth in Claim 12 further including:
at least 2% of a resinous film forming agent;
and at least 2% of an isolating agent.

16. A pressure sensitive chemical type transfer medium comprising:
planar sheet material having an at least partially transferable coating layer disposed on one surface thereof, said transferable coating layer constituted by the solidified residue of an applied hot melt emulsified liquid film consisting of about 50 to 60% of a composite meltable low oil content wax carrier vehicle made up from 3 to 4 parts of paraffin wax to 1 part of carnauba wax;
about 2 to 5% of a synthetic chemically modified wax-like material having the properties of a flow agent and dispersant;
about 3 to 10% of a polyethylenic film forming agent;
about 5% of an opacifier-filler;
about 3 to 10% of stearic acid and about 25 to 35% of a concentrated solution of zinc chloride made up of at least 2 parts of zinc chloride to 1 part of water as an electron accepting chromogenic reagent;
said transferable coating layer having emulsified discrete liquid droplets of said concentrated zinc chloride solution distributed therewithin.

17. A pressure sensitive chemical type transfer medium as set forth in Claim 16 wherein:
. said concentrated solution of zinc chloride further contains a relatively small amount of an acid chloride neutralizing agent selected from the group consisting of ammonium carbonate and ammonium bicarbonate.

18. A pressure sensitive chemical type transfer medium as set forth in Claim 16 wherein said chemically modified wax-like flow agent is selected from the group con-sisting of the product obtained by reacting a selectively oxidized linear unsaturated hydrocarbon having a terminal carbon double bond with ammonia or a primary organic amine and further reacting the resulting modified hydrocarbon with an isocyanate; the product obtained by reacting an oxidized microcrystalline wax with an isocyanate, the product obtained by reacting an oxidized non-benzenoid was with an isocyanate;
the product obtained by reacting an oxidized microcrystalline wax with ammonia or an amine and further reacting the resulting modified hydrocarbon with an isocyanate and the product obtained by reacting an oxidized non-benzenoid wax with ammonia or an amine and further reacting the resulting modified hydrocarbon with an isocyanate.

19. A pressure sensitive chemical type transfer medium as set forth in Claim 16, wherein:
the majority of said emulsified liquid droplets of concentrated zinc chloride solution are less than 1 micron in diameter,

20. A pressure sensitive chemical type transfer medium as set forth in Claim 8, wherein said planar sheet material has a non-transferable image producing receptor layer on the other surface thereof;
said image receptor layer comprising the solidi-fied residue of an applied alkaline liquid intermixture of an evaporable liquid vehicle, a resinous binder, an opacifier-filler and a water insoluble colorless color precursor as the chromogenic reagent distributed therewithin, said color precursor chromogenic reagent being insoluble in said water base metallic halogen salt solution and being selectively convertible into a color producing condition upon interreaction therewith.

21. A pressure sensitive chemical type transfer medium as set forth in Claim 20 wherein:
said color precursor chromogenic reagent material in said image receptor layer comprises a mixture of water insoluble, alkaline stable and acid reacting organic dyestuffs to produce a dark, light stable and enduring image.

22. A pressure sensitive chemical type transfer medium as set forth in Claim 20 wherein said chemically modified wax-like flow agent is selected from the group con-sisting of the product obtained by reacting a selectively oxidized linear unsaturated hydrocarbon having a terminal carbon double bond with ammonia or a primary organic amine and further reacting the resulting modified hydrocarbon with an isocyanate; the product obtained by reacting an oxidized microcrystalline wax with an isocyanate, the product obtained by reacting an oxidized non-benzenoid wax with an isocyanate;

the product obtained by reacting an oxidized microcrystalline wax with ammonia or an amine and further reacting the result-ing modified hydrocarbon with an isocyanate and the product obtained by reacting an oxidized non-benzenoid wax with ammonia or an amine and further reacting the resulting modified hydrocarbon with an isocyanate.

23. A pressure sensitive chemical type transfer medium comprising:
planar sheet material having an at least partially transferable coating layer disposed on one surface thereof constituted by the solidified residue of an applied hot melt low oil con-tent wax base emulsified liquid film containing an amine modified synthetic wax flow agent and dispersant as an emulsifying agent therein and having dis-crete liquid droplets of a water base solution of an ionized metallic halogen salt electron accepting chromogenic reagent material distributed therewith.

24. A pressure sensitive chemical type transfer medium as set forth in Claim 23 wherein:
the majority of said discrete droplets of the water base solution of an ionized metallic halogen salt electron accepting chromogenic reagent material. are homogen-eously distributed within the solid coating layer and the majority of which are less than 1 micron in diameter.