US3732120A - Pressure-sensitive recording sheet - Google Patents

Abstract

SENSITIZED RECORD SHEET MATERIAL, SUITABLE FOR DEVELOPING USEFUL COLOR IN OILY, COLORLESS, CHROMOGENIC DYE-PRECURSOR INKS APPLIED THERETO. SAID RECORD SHEET MATERIAL HAS A COATING COMPRISING AN OIL-SOLUBLE METAL SALT OF A PHENOL-FORMALDEHYDE NOVOLAK RESINS.

Description

ay 8, 1973 B. w. BROCKETT ETAL PRESSURESENSITIVE RECORDING SHEET Filed June 14, 1971 INVENTORS & T b R E E K L m m H B.E.H. @m WTL 1m E M C U ROA \L BRM W fi w 5 Z Y. B m02 mm0wm THEIR ATTORNEY 8: AGENT United States Patent 6 3,732,120 PRESSURE-SENSITIVE RECORDING SHEET Bruce W. Brockett and Robert E. Miller, Dayton, and

Mary L. Hinkle, Middletown, Ohio, assignors to The National Cash Register Company, Dayton, Ohio Filed June 14, 1971, Ser. No. 152,830 Int. Cl. B41m 5/16 US. Cl. 117-16 14 Claims ABSTRACT OF THE DISCLUSURE Sensitized record sheet material, suitable for developing useful color in oily, colorless, chromogenic dye-precursor inks applied thereto. Said record sheet material has a coating comprising an oil-soluble metal salt of a phenol-formaldehyde novolak resin.

This invention relates to record material sheets bearing a coating of an oil-soluble metal salt of a phenol-formaldehyde novolak resin as a co-reactant for colorless, chromogenic dye-precursor materials to develop a useful color therein. Oil-soluble phenol-formaldehyde novolak resins, preferably those derived from the condensation of a parasubstituted phenol with formaldehyde, have long been used, with great commercial success, in making acid-reactant record material sheets capable of developing color in oil solutions of base-reacting colorless, chromogenic dye-precursor materials. Such resins and the use of them are disclosed in applications for United States Patents, Ser. Nos. 44,805, filed June 9, 1970, by Robert E. Miller and Paul S. Phillips, Ir., now US. Pat. 3,672,935, and 830,921, filed May 26, 1969, by Robert E. Miller and Bruce W. Brockett, now US. Pat. 3,663,256.

United States Patent 3,516,845, which issued June 23, 1970 on application of Bruce W. Brockett, represents an improvement on the known-art acid-reacting record material sheets of the previously cited applications. In the Brockett improvement patent, acidic, water-soluble metal salts, such as zinc chloride, are provided in the sheet coating, intermixed and juxtaposed with particles of oilabsorptive kaolin clay and oil-soluble phenol-formaldehyde resin particles. The metal salt-kaolin-phenolic resin combination gives improved intensity and fade resistance to the developed color of prints made thereon with basereacting colorless chromogenic dye-precursor materials. A definite synergistic effect was noted wherein the improvement was greater than that which was predicted by the arithmetic combination of intensities and fade rates obtained on prints developed by the three agents (kaolin, zinc chloride and phenolic resin) separately. Thus, certain water-soluble salts and certain oil-soluble resins mixed together with kaolin on a record receiving sheet represents an improvement in the art.

Now it is found that the record receiving sheets of this invention constitute a further improvement wherein both the metallic moiety and the acidic resin are part of the same oil-soluble molecule and both are available for colordeveloping reaction in oil solution. This improvement can be realized by providing on the sheet surface certain oil-soluble metal salts of phenol-formaldehyde resins. Such salts are known, but not in the record material art. See United States Patent 2,760,852, which issued Aug. 28, 1956 on application of Donald R. Stevens et al., for a discussion of syntheses of phenol-formaldehyde-metal salts and their use as lubricating oil additives.

It has been found that the amount of color developed in a fixed amount of a colorless chromogen, such as CVL in fixed concentration in oil solution, by a phenolic resin is greatly enhanced by the replacement of part of the Patented May 8, 1973 resins phenolic protons with certain metal ions such as zinc(II), Such a proton replacement gives a metal resinate, also called herein a metal-modified resin. As more and more protons in a metal-modified resin are replaced with metal ions, zinc(II) ions for instance, a maximally effective chromogen/metal-modified resin combination is obtained. In the CVL/zinc-modified resin combination, maximum color development is realized in a combination containing one gram-atom of zinc(II) per CVL molecule. When the maximum color has been achieved by a CVL/zinc-modified resin combination, the addition of more zinc ions to the combination by either further proton replacement or the addition of more zinc-modified resin to the combination brings about a slight decrease in the color intensity that is realizable with the combination.

An object of this invention is to provide a metal-modified oil-soluble phenol-formaldehyde resin, for use in carbonless copypaper record materials, which give developed prints that are more resistant to fade than those developed by the known-art resins. This object is realized by replacing part of the phenolic protons of an oil-soluble phenolformaldehyde resin with a metallic cation. The fade-resistance of known-art resins is improved by replacement of part of the phenolic protons with metallic cations, the choice of which metal cation being of minor importance. It is a further object of this invention to provide a metal-modified oil-soluble phenol-formaldehyde resin for use in carbonless copy-paper record materials which give developed prints that are about as intense or more intense when freshly developed than those developed by known art resins. This object is best realized by replacing part of the phenolic protons of a phenol-formaldehyde resin with certain preferred cations, namely cadmium (III), zinc(II), and zirconium(II) to give metal-modified resin with enhanced fresh-print intensity. Other metallic ions which give improved fade-resistance and similar (but not necessarily improved) fresh-print intensity to known-art unmodified resins when used to make metal-modified resins according to this invention include: vanadium(II), manganese(II), calcium(II), nickel(II), cobalt(II), strontium(H), aluminum(III), copper(III), and tin(II).

Concerning the necessary amounts of metal ions to introduce into the disclosed phenol-formaldehyde resins in order to realize the benefits of this invention, the weight percent of metal ion in useful metal resinates will vary depending on the metal chosen and the resin chosen. In general, only small amounts of metal ion need be introduced (about one percent by weight) to give appreciable improvement in print fade resistance and print intensity. If zinc(II) is chosen as the metal to replace one phenolic proton in each molecule of a commercial sample of paraphenylphenol-formaldehyde resin, having an average of three repeating units per molecule, a maximum of about 6 percent by weight of zinc can be readily introduced. Although it is theoretically possible to replace all phenolic protons of phenol-formaldehyde novolaks with metallic ions, there is considerable evidence in the literature that only about one phenolic proton per molecule is readily available for replacement, the other phenolic protons being less acidic because of their involvement in intramolecular hydrogen-bonding. In this disclosure, replaceable protons will be defined as readily replaceable protons, that is only about one phenolic proton per molecule of resin mixture. Thus the above discussed weight percent range (1 to 6 percent) of zinc(II), in the zinc resinate derived from the specified para-phenylphenol-formaldehyde resin, represents a metal ion replacement of about 15 to percent of the replaceable protons. For purposes of improving the print fade resistance and print intensity of prints made therewith according to the teachings of this invention, the preferred range of proton replacement or metallization in a phenol-formaldehyde 3 novolak is about 30 to 100 percent of the replaceable protons. For zinc(II) and the specified para-phenylphenol-formaldehyde novolak, this preferred range of proton replacement represents a metal resinate having a composition that includes about 2 to 6 weight percent of zinc(II).

A further object of this invention is to make a colordeveloping agent for basic-chromogens that is completely oil-soluble (unlike acidic clays and the combination agents exemplified by para-phenylphenol-formaldehyde resin together with zinc chloride) so that it may be used in a variety of ways including particulate coating on a sheet, solution coating on a sheet, said coatings in combination with encapsulated oily solvents provided in or near said coatings for dissolution and transfer of said color-developing agent in use, and coatings of oily solution droplets of resin isolated and contained by organic, hydrophilic, polymeric film material as microcapsules or dried emulsion films.

Furthermore, an object of this invention is to realize improvements in the speed and intensity of print development as well as improvements in stability toward the environment of the coated developing agent prior to print color-development and of the dye color in the developed print without resorting to coatings of water-soluble metal salts together with the commonly-used novolak resins. Novolak powder particles are commonly bound to paper with cooked starch binder and latex binders such as styrene-butadiene latexes, but novolaks in combination with zinc chloride and other useful water-soluble metal salts cannot be successfully bound to paper with latexes and/or cooked starch binder, thereby necessitating the use of other binders such as poly(vinyl alcohol). Adequate adhesion is difficult to achieve with poly(vinyl alcohol) as the sole binder and furthermore such sheets do not give good printing characteristics with off-set printing presses and inks.

These and other objects have been realized by the embodiments of this invention.

In reducing the tendency of developed dye color images to fade when exposed on a CF receiving sheet surface to environmental influences, metal resinates are greatly advantageous over known-art resins. The following metals as the cation of a para-phenylphenol-formaldehyde resin have all been found to improve fade-resistance (when compared to un-modified para-phenylphenolformaldehyde resin): aluminum(III), barium(II), cadmiunr(II), calcium(II), cobalt(II), copper(II-I), indium (III), magnesium (II), manganese(II), molybdenum(V), nickel(II), lead(II), sodium(I), strontiumfII), tin(I=I), titanium(IV), vanadiumfll), zinc(II), and zirconium- (IV). The great diversity of the metal resinates tested and found useful for decreasing print fade should be noted inasmuch as they include metals from Periodic Groups I-A and B, I I-A and B, III-A and B, IV-A and B, V-B, VI-B, VII-B, and VIII. The choice of metal in making metal resinates, as fade-resistant, chromogenic-materialprint developers, appears to be of little importance, inasmuch as all metal resinates, as far as is known, function well in this regard.

The effect of the replacement of phenolic protons with metal ions, such as zinc(iII), on the intensity of developed dye color can be seen in the figure. In the figure are shown the visible-light absorption curves of a solution of CVL and resin (1 equivalent of CVL to about 1.4 equivalents of resin) Curve l0, and a solution of CVL and the zinc-modified resin of Example 1 (1 equivalent of CVL to about 1.3 equivalents of metal-modified resin containing 5.0 weight percent of zinc(II), Curve 11. The optical density of the peak absorption of Curve 11 is about 4.7 times that of Curve 10. The solvent in both cases was benzene and the concentration of CVL was the same in both cases. Further enhancement of the absorption peak, and therefore the color intensity, can be effected by replacement of additional resin protons with zinc(II) or by the addition of more zinc-modified resin to the soltuion, but the effect does of course become less pronounced as the maximum effect is approached. At the point of maximum effect, Curve 11 can be enhanced to the extent of at least about 50 times the optical density of Curve 10.

In general, it has been found that the effectiveness of metal-modified resins in enhancing color-production, in chromogenic dye-precursors such as CVL, is inversely related to the chelating-ability of the metal ion used to make the metal-modified resin. For instance, metals that form very stable chelates with acetylacetone, having stability constant logs (log Kstabimy corected to zero ionic strength) greater than about 5.5, do not generally enhance CVL color-production when used to make metalmodified resins. The metals of more unstable metal acetylacetone chelates, having ionization constant logs less than about 5.5, will generally be found to enhance a CVL-resin color intensity in solution. Such metallic ions and resins modified therewith are designated herein as color-enhancing metals and color-enhancing metalmodified resins. That is to say, solutions of CVL and metal-modified resin will generally show higher optical densities as the stability constants of the chelates of the chosen metals and acetylacetone decrease. However, it should be noted that there will be wide variance among the oil-solubilities of these color-enhancing metal-modified resins which Will affect the maximum concentration of the colored species attainable in the chosen oil. In any chosen record-material system, the most useful metals will be those color-enhancing metals whose metal resinates are readily soluble in the liquid vehicle droplets used in the record material system capsules. For a metal to be useful as a metal-modified resin in a record material copy sheet, the metal must be a color enhancer and the metal-modified resin must be readily soluble in the oil droplets included in the copy paper.

In practice, oily, colorless, chromogenic dye-precursor inks used in the carbonless copy-paper field are solutions of solid, colorless, basic, chromogenic dye-precursor materials in oily vehicles having a dielectric constant of about 5 or less. Halogen-substituted aromatic hydrocarbons, alkylated aromatic hydrocarbons and dialkyl phthalates are typical of the oils used as ink vehicles. The metal-modified resins of this invention are designed to operate and do operate well in developing oily dyeprecursor inks of the type described. The oily vehicle preferred herein is one of low volatility, such as chlorinated or alkylated biphenyl, which leaves an essentially wet print on the paper surface rather than a more volatile one such as xylene that readily evaporates to leave a dry print. The enhancement of print intensity by the metal-modified resins of this invention is considerably greater in wet prints than in dry prints.

In the preceding discussion, the metal-modified resins of this invention are viewed as being coated on a receiving sheet for the receipt and development of color in liquid dye-precursor materials, but they are not so-limited in use. As is taught in the previously-cited application of Miller and Phillips, there are various ways of arranging, in a record material, the different components of a color-developing system comprising oil-soluble dye precursor material, oil-soluble polymeric resin co-reactant material and mutual-solvent oil. FIG. 2 of the Miller- Phillips application shows a number of such arrangements. Any and all of the metal-modified resins of this invention may be coated on paper, as particulate material or as a printed solution residue, or included among the fibers of a fibrous substrate such as paper, or dissolved in oil and encapsulated as solution droplets prior to being coated on paper so as to operate in all of the record-material constructions of the Miller-Phillips applications FIG. 2. The metal-modified resins of this invention are oil-soluble and are grindable to a fine powder, and are encapsulatable as fine oil-solution droplets. So

they are adaptable for use in any of the ways Miller and Phillips envisioned and taught that oil-soluble polymeric resin co-reactants could be used. Furthermore, as analogously taught in the Miller-Phillips application using novolaks, the inclusion, in metal-modified resin papercoatings of microcapsules which contain a chemicallyinert oily solvent for the metal-modified resin, gives effective transfer sheets for use with receiving sheets that include particles of colorless chromogenic dye precursor materials. In use, the oil-containing microcapsu'les rupture under writing pressure and release the oily solvent droplets which act as a solvent for adjacent metalmodified resin particles and effectively transfer the resulting solution to nearby chromogenic particles for color-developing chemical reaction at the site of the chromogenic particles. The preparations of both kinds of metalmodified resin transfer sheets are taught in Example 3: transfer sheets having coated on a surface oil-soluble meal-modified resin particles together with microcapsules containing an inert oily solvent and transfer sheets having surface coatings of microcapsules containing oilsolution droplets of a metal-modified resin.

The metal-modified resins of this invention may be applied to substrate sheets in many different ways including being: (1) applied to a sheet from a printing solution as taught in the aforementioned Miller-Phillips application and in United States Pat. No. 3,466,184, which issued Sept. 9, 1969 on the application of Richard G. Bowler and Robert E. Miller, (2) applied as a substratum below the surface of a fibrous record material as taught and claimed in U.S. Pat. No. 3,466,185 which issued Sept. 9, 1969 on the application of John E. G. Taylor, (3) applied as a particulate, finely ground powder as taught in the aforementioned Miller-Phillips application or in combination with an oil-adsorbent coating-clay such as kaolin as taught and claimed in U.S. Pat. No. 3,455,721, which issued July 15, 1969 on the application of Paul S. Phillips, Jr. and Gerald M. 'Hein, and (4) applied as a film-coating on paper coating pigment particles such as kaolin clay particles as taught and claimed in U.S. application No. 807,960 which was filed on Mar. 17, 1969 in the name of Bruce W. Brockett.

Methods of making the useful metal resinate salts of this invention include reaction of an oil-soluble phenolaldehyde resin, preferably a para-substituted-phenol-formaldehyde novolak resin, with a desired metal hydroxide or oxide. Alternatively, a water soluble intermediate metal resinate may be made by treatment of the resin with a strong aqueous base, such as aqueous sodium hydroxide for instance, to give an aqueous solution of sodium resinate, followed by treatment of the sodium resinate solution with an aqueous solution of a salt of a desired metal, zinc chloride for instance, to bring about a precipitation of the desired metal resinate, zinc resinate in this instance.

A preferred method involves the reaction of an oilsoluble phenol-aldehyde novolak melt with a desired metal carboxylate or enolate. This method is exemplified in Example 1 where a novolak is melted and treated with zinc hydroxy benzoate powder to give zinc resinate plus benzoic acid. When zinc acetylacetonate is used in place of zinc hydroxy benzoate, zinc resinate is similarly formed together with free acetylacetone in the hot melt reaction. As a variation of this method, a metal salt may be added to a phenol-formaldehyde reaction mixture at the time of resin manufacture. It is to be noted that in the acidcatalyzed condensation of monomeric phenols and aldehydes, water and acid is generally distilled from the reaction mixture as the reaction proceeds. The addition to the condensation reaction medium of an acidic, water soluble metal salt, such as zinc chloride, will contribute hydrochloric acid to the distillate and leave zinc resinate as the reaction product in the pot residue. To some extent the last-described method probably involves the condensation of monomeric metal phenolates (such as zinc phenolates) with aldehydes to give the desired metal resinates.

When the metal-modified resin is intended for application in solution as the core-material of microcapsules, a particularly convenient method is to simply dissolve the chosen novolak and a carboxylate or enolate of the chosen metal in an encapsulatable oil. The novolaks used in this invention are sufliciently acidic to compete for the metal ions and act as metal resinates even in the presence of the added metal salt anion.

Methods of making useful metal resinoatcs and the uses of said resinates in record material sheets for the development of color in chromogenic dye-precursor materials are set out in detail in the following specific examples. All parts therein are parts by Weight unless otherwise specified.

EXAMPLE 1 Useful metal resinates A mixture of two kilograms of p-phenylphenolformaldehyde resin with 400 grams of zinc hydroxy benzoate was heated and stirred for one hour, under a helium blanket, at elevated temperatures. The temperature was gradually raised from room temperature to about 200 to 220 degrees centigrade over a period of about 45 minutes and then allowed to cool to about degrees centigrade over the next fifteen minutes. At the end of the reaction time the hot zinc resinate was poured from the reaction vessel and allowed to cool and harden. The hardened resin was ground under water in an attritor to give a fine powder suitable for coating as particulate matter on a paper sheet. The zinc content of this resinate (after discarding and disregarding a small amount of oil-insoluble inorganic sludge present in the reaction product) was found to be 5.0 percent, by Weight.

Alternatively, a hot melt of one kilogram of p-phenylphenol-formaldehyde resin at 160 degrees centigrade was agitated and treated with 100 grams of zinc acetylacetonate which was added slowly. Following the addition, the agitated melt was held at the elevated temperature for ten minutes, poured and allowed to harden.

EXAMPLE 2 Metal-modified-resin-coated CF sheets A paper-coating slurry of 30 percent solids content was prepared by mixing the following ingredients:

air knife coater (air-pressure 2.75 pounds/square inch) and dried, by a 12-second pass through a high-velocity-air oven at an average temperature of about degrees Fahrenheit, to give a dry-coat Weight of 4 pounds per ream of 500 sheets (25 by 38 inches) having a total area of 3,300 square feet.

The CF test sheet of this invention used to obtain the test data in the table following these examples was made according to the procedure of this example with a slight variation in the dry formulation: zinc-modified resin (12.0), kaolin clay (60.0), silica gel (3.0), calcium carbonate (9.0), styrene-butadiene latex binder (7.5), cooked starch binder (8.5). The dry formulation was made up to 30 percent solids and coated as before to give a 5 pound per specified ream dry coat weight.

Commercial NCR Paper CB sheets, having capsular coatings containing oily solution droplets of Crystal Violet Lactone (CVL) and benzoyl leuco methylene blue (BLMB), were coupled with the above CF sheets to make a mark-producing, transfer-receiving sheet couple.

EXAMPLE 3 Metal-modified resin transfer sheets (A) The coating slurry of Example 2 was coated at 4 pounds coat weight per specified ream on a paper sheet surface which already carried a coat (2.5 pounds per specified ream) of oil-containing rnicrocapsules bound thereto with cooked starch binder. The rnicrocapsules were made according to the procedure of B. K. Green and L. Schleicher (US. Pat. 2,800,457) with gelatin-gum arabic walls and with isopropyl-biphenyl droplets as the core material. The so-made copy sheets was mated with a second sheet of paper (which had been dipped in a 2 percent solution of CVL in alcohol and dried to leave a residue of CVL thereon) with the coated face of the copy sheet opposing said second sheet. When the uncoated face of the copy sheet was written on with a pencil, a copy of the writing appeared on the second sheet as a result of the oil transfer of the metal modified resin from the coated surface of the copy sheet to the CVL- containing sheet.

(B) A metal-modified resin solution was encapsulated according to the procedure of Example II (C) of United States Pat. No. 3,341,466, which issued Sept. 12, 1967 on the application of Carl Brynko et al. The core material in this case was prepared by dissolving in 50 parts of 1,2,4 trimethylbenzene, parts of para-phenylphenolformaldehyde resin and a solution of 14.5 parts of zinc naphthenate in parts of a low-volatility hydrocarbon solvent, and dispersing the oily solution in an aqueous vehicle to give droplets of about 3.5 micron average diameter. These so-prepared capsules were coated on 33 pound bond paper stock (at a dry-coat weight of 2.5 pounds of capsules per specified ream) using as binder material poly(vinyl alcohol) (one part to ten parts of capsules). The metal-modified resin capsule-coated sheets were mated with a CVL-sensitized sheet to make a transfer-receiving sheet couple. Pressure writing and typing on the uncoated, top surface of the resin-containing capsule-coated transfer sheet, coupled with the CVL- sensitized receiving sheet, produced intense blue marks on the pressure pattern on the receiving sheet.

When the receiving sheet was sensitized with 1-(2- pyridylazo) 2 naphthol is a colorimetric indicator genmark was produced by the above transfer sheet. 1-(2- pyridylazo) 2 naphthol is a colorimetric indicator generally used for the detection of zinc(II).

EXAMPLE 4 Self-contained copy-sheets Self-contained pressure-sensitive sheets, that is single sheets which contain all the color-producing elements, namely metal-modified resin, chromogenic dye-precursor material, and isolated solvent capable of dissolving both the co-reactants, were produced by coating a metal-modified resin slurry (according to Example 2) over a commercial NCR Paper CB sheet capsular coating or alternatively by coating the metal-modified resin-containing capsules, of this example, directly on the CVL-sensitized sheet of this example.

The following table presents comparable data on a known-art, resin-sensitized receiving sheet, a CF sheet, of good commercial quality and a metal-modified resinsensitized CF sheet of this invention, for use with various capsular transfer sheets, CB sheets, which yield colorless, liquid dye-precursor inks under imaging pressure.

( 3-week wall fade, TI 3-week wall decline, 20-minute TI Fresh sheet, Instant TI 3-week wall decline, Instant 'II DOA DOP ARO DOA DOP ARO Tufts DPO DOA DOP ARO DPO DOA DOP DPO DPO DOA DOP ARO DPO CB cheats Phillips-Hem CF sheet CF sheet of this invention TI stands for "Typewriter Intensity" and is equal to times the ratio of the reflectance of a printed character divided by the background reflectance. A Tl value of 100 indicates no discernible print and a lower I value indicates a darker or more intense print. Column (1) gives TI values read 20 minutes after printing. A time of 20 minutes is chosen so all prints will 0 be fully developed and differences in print speed will not; be erroneously reflected in print intensity data. Column (2) gives TI values on fully-developed prints which have been aged by hanging [or 3 weeks on the wall, exposed to air, natural and fluorescent room light, and ambient temperature and moisture levels. This is a measure of the environmental stability of developed print colors on particular CF sheets. -1ninute TI values of prints made of CF sheets that were aged 3 weeks on the wall before the print was made. This is a measure of the stability of CF sheets in maintaining their ability to develop genie dyes during and after exposure to the CF sheets to the environment. gives instant TI-values (that is immediately after pressure-imaging) of freshly-made sheets. Column (5) gives instant TI-valucs of sheets alter the above-discussed three-week wall decline. A comparison (4) and (5) gives a measure of print-speed loss in aged sheets. y used abbreviation for Crystal Violet Lactone; BLMB is the commonly used yl leuco methylene blue; N102 is a dark neutral dye (2'-ani1ino-U-diethylamino-W- methyltiuoran) disclosed and claimed in United States application N 0. 90,097 in the name of Ghee-Han Lin The Phillips-Hem CF Sheet" is a kaolin-phenolic CF sheet prepared according to United States Patent 721 with 5.5 parts of kaolin to one part of paraphenylphenol-iormaldehyde resin at a dry coat The CF Sheet of This Invention is a sheet of Example 2, prepared from the zinc-modified resin of Example 1, having 5.0 weight percent zinc(II), in the resin or about 90 to 100% of its available protons replaced with ARO sheet having 3.3 pounds/ream of rnicrocapsules containing chlorinated biphenyl-high boiling alkane ream of rnicrocapsules containing diphenyl oxide-high boiling alkane (2:1) 3.5 pounds/ream of rnicrocapsules containing dioctyl adlpate-alkylated benzene (2:1) 2.6 pounds/ream oi rnicrocapsules containing dioctyl phthalate-high boiling alkune (2:1)

) and BLMB (0.5 part). d to deliver to the receiving sheets as near as possible equal weights of In the above table, the typewriter intensities presented give a measure of several properties of the CF sheets, being compared. These are:

(a) Primary Typewriter Intensity, the total color developable by a freshly-made CF sheet (against a given CB sheet)-Column (1).

(b) Fade, the stability of a colored-image on exposure to the environment-Column (2) compared to Column (1).

(e) Decline, the decrease in the ability of a CF, sheet to develop color of CB-sheet dye-precursors after. exposure to the CF sheet to the environment-Column (3) compared to Column (1).

((1) Fresh sheet print speed-Column (4) compared to Column (1).

(e) Aged sheet print speed-Column (5) compared to Column (3).

(If) Loss of print speed on aging-compare item ((1) above with item (e).

What is claimed is:

1. A pressure-sensitive record sheet material comprising supporting web material having adhesively bound on a surface thereof a coating which includes at least two color-forming reactants, one an oil-soluble metal salt of a phenol-formaldehyde novolak resin, and another a colorless, chrornogenie dye-precursor material reactively colorable by said novolak resin salt, an oily solvent droplets capable of dissolving said color-forming reactants in mutual solution, wherein said oily solvent droplets are isolated from at least one of said, color-forming reactants and are held in 21 contained condition by hydrophilic organic polymeric film material.

2. The record sheet material of claim 1 wherein the metal of the metal salt is selected from the group consisting of aluminum, barium, cadmium, calcium, cerium, cesium, cobalt, copper, indium, magnesium, manganese, molybdenum, nickel, lead, sodium, strontium, tin, titanium, vanadium, zinc and zirconium.

3. The record sheet material of claim 2 wherein the metal of the metal salt is selected from the group consisting of aluminum, cadmium, calcium, cobalt, copper, manganese, nickel, strontium, tin, vanadium, zinc, and zirconium.

4. The records sheet material of claim 3 wherein the metal of the metal salt is selected from the group consisting of cadmium, zinc and zirconium.

5. The record sheet material of claim 4 wherein the metal of the meltal salt is zinc.

6. The record sheet material of claim 1 wherein the novolak resin is a para-substituted phenol-formaldehyde resin.

7. The record sheet material of claim 6 wherein the novolak resin is a para-phenylpehnol-formaldehyde resin.

8. The record sheet material of claim 5 wherein the novolak resin is a para-phenylphenol-formaldehyde resin.

9. The record sheet material of claim 8 wherein the zinc salt of para-phenylphenol-formaldehyde has a zinc content in the range of about one to about six percent by weight. 1

10. The record sheet material of claim 8 wherein the chromogenic dye-precursor "material comprises Crystal Violet Lactone present to the exent of about one grammolecular weight per gram-atom of zinc.

11. The record sheet material of claim 1 wherein the metal salt ofthe novolak resin is adhesively bound to the web with a binder material that includes a latex binder.

12. The record sheet material of claim 1 wherein the metal salt of the novalak resin is a fine powder.

'13. The record sheet material of claim 1 wherein the metal salt of the novolak resin is a solution-deposited film residue.

14. The record sheet material of claim 1 wherein the metal of the metal salt is selected from metal ions that form chelates' wtih acetylacetone having stability constant logs (log K corrected to zero ionic strength) no greater than 5.5.

References Cited UNITED STATES PATENTS 2,886,554 5/1959 Schenker 260-59 2,981,652 4/1961 Peterson et al. 26059 3,418,273 12/1968 Economy et al. 260-59 3,516,845 6/1970 Brockett 117-155 L 3,451,338 6/1969 Baum 117-362 MURRAY KATZ, Primary Examiner US. Cl. X.R.

117-362, 36.8, 36.9, L, 155 UA; 26059

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