Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
  • B41M—PRINTING, DUPLICATING, MARKING, OR COPYING PROCESSES; COLOUR PRINTING
  • B41M5/00—Duplicating or marking methods; Sheet materials for use therein
  • B41M5/124—Duplicating or marking methods; Sheet materials for use therein using pressure to make a masked colour visible, e.g. to make a coloured support visible, to create an opaque or transparent pattern, or to form colour by uniting colour-forming components
  • B41M5/1243—Inert particulate additives, e.g. protective stilt materials

Definitions

• This invention relates to carbonless papers incorporating refined legume starch as a stilting material into the CB (coated back) coatings.
• Carbonless papers incorporating refined legume starch are particularly useful when used in high speed electrophotographic copier/duplicators, offset printing presses, and laser printers.
• Carbonless papers incorporating refined legume starch as a stilting material are less prone to capsule rupture during printing operations and less prone to feeder induced smudging when compared with carbonless papers employing the traditionally used wheat starch.
• Carbonless impact marking papers for the transfer of images are papers which are capable of producing an image upon application of pressure.
• Products employing this chemistry generally comprise at least two substrates (for example, two sheets of paper) and involve coating one reactant, known as a color-former, on one substrate, and the other reactant, known as a developer, on another "mating" substrate.
• One surface, or side, of each substrate is coated with one of the two primary reactants.
• the two substrates are often referred to as a donor sheet and a receptor sheet.
• Means for preventing the reacting of the two until intended i.e., until activating pressure is applied
• This is typically accomplished by encapsulation of one of the reactants.
• a fill solution of the color-forming compound(s) in a hydrophobic solvent is encapsulated or contained in microcapsules and is coated on the back side of one sheet of paper to form a donor sheet.
• This donor sheet is then mated with a receptor sheet coated with a developer or reactant for the color-forming compound.
• the microcapsules serve the purpose of isolating the reactants from one another and preventing reaction.
• the two substrates come into contact under sufficient pressure so that the capsules rupture (i.e., those capsules corresponding to the pattern of applied pressure) and the solution of encapsulated color-former is released and transferred from the donor sheet to the receptor sheet.
• the receptor sheet On the receptor sheet, a reaction between the previously separated reactants occurs. Since the color-former and the developer form a deeply colored image when reacted, an image forms on the receptor sheet.
• the resulting reaction will, of course, form a colored image corresponding to the path traveled by the stylus or the pattern of pressure provided by the stylus or key.
• activating pressure includes, but is not limited to, pressure applied by hand with a stylus or pressure applied by a business machine key (for example, a typewriter key); and the term “encapsulation” and “encapsulated compounds” refer to microcapsules enclosing a fill material.
• the chemistry used in carbonless papers is of two general types.
• the image results from the reaction between an encapsulated leuco dye color-former and an acid, a phenolic, or acidic clay developer.
• the image results from the formation of a colored coordination compound by the reaction between an encapsulated ligand color-former and a transition metal developer.
• a preferred construction contains an encapsulated color-former dissolved in appropriate hydrophobic solvent(s) within microcapsules and coated with a suitable binder onto a back side of the donor sheet, sometimes referred to as a "coated back” (CB) sheet.
• a developer also optionally in a suitable binder such as a starch or latex, is coated onto the front side of the receptor sheet sometimes referred to as a “coated front” (CF) sheet.
• suitable binder refers to a material, such as starch or latex, that allows for dispersion of the reactants in a coating on a substrate.
• Each CB coating contains rupturable capsules which, when ruptured, release reagents to produce a color-changing reaction at the adjacent CF coating.
• the preparation of such carbonless sheets is disclosed by Gale W. Matson in U.S. Patent Nos. 3,516,846 and 3,516,941, the disclosures of which are incorporated herein by reference.
• a popular material for shell formation is the product of the polymerization reaction between urea and formaldehyde (UF capsules), or between melamine and formaldehyde (MF capsules), or the polycondensation products of monomeric or low molecular weight polymers of dimethylolurea or methylolated urea with aldehydes.
• the two sheets are positioned such that the back side of the donor sheet faces the developer coating on the front side of the receptor sheet.
• the uncoated surface of the donor (CB) sheet contains a form of some type and the activating pressure is generated by means of a pen or other writing instrument used in filling out the form.
• the image appearing on the receptor (CF) sheet is a copy of the image applied to the top sheet.
• Constructions containing a first substrate surface, on which is coated the encapsulated color-former, and a second substrate surface, on which is coated a developer, are often prepared.
• the coated first substrate surface is positioned within the construction in contact with the coated second substrate surface.
• Such a construction is known as a "set” or a "form-set” construction.
• Substrates with one surface, on which is coated the encapsulated color-former, and a second, opposite surface, on which is coated a developer, can be placed between the CF and CB sheets in a construction involving a plurality of substrates.
• Such sheets are generally referred to herein as "CFB" sheets (i.e., coated front and back sheets).
• CFB sheets are also typically used in form-sets. In some applications, multiple CFB sheets have been used in form-sets. These contain several intermediate sheets, each having a developer coating on one side and a coating with capsules of color-former on the opposite side.
• the sheets in the form-set are sequenced in the order (from top to bottom) CB, CFB(s), and CF. This insures that in each form-set a color former and a color developer will be brought into contact when the microcapsules containing the color-forming material are ruptured by pressure.
• CB, CF, and CFB sheet are self-contained (SC), or autogenous, carbonless paper in which both the color-former and developer are applied to the same side of the sheet and/or are incorporated into the fiber lattice of the paper sheet.
• SC self-contained
• carbonless paper in which both the color-former and developer are applied to the same side of the sheet and/or are incorporated into the fiber lattice of the paper sheet.
• Stilt particles may be of many different compositions, but have the common property of being inert to the solvents used in the capsules and being from 1.5 to about 2.5 times the size of the capsules.
• Cellulose fibers have been used as stilt material, and U.S. Patent No. 4,630,079 describes use of such fibers with a specified fiber length for such use.
• Cellulose fibers have a tenancy to "mat up" on coaters used to coat carbonless papers and thus cause problems during manufacture of carbonless paper sheets.
• Another stilt material described in U.S. Patent 3,625,736, uses particles composed of a water insoluble polymer with a size of 1.5 to 2.0 times that of the capsules.
• EP 0,017,385 describes the use of starch stilt at a level of least 150% of the capsule weight.
• EP 0,011,367 also describes the use of starch as stilting material.
• Dutch Patent 70/05,045 compares the efficiency of different starches as stilt materials for carbonless paper. Tests for imaging in a typewriter (typewriter intensity test) and for handling resistance (friction staining test) determined starch derived from arrowroot to afford the best stilting material.
• Johnson, et al., U.S. Patent No. 4,280,781 describes the use of classified wheat starch as stilt materials for carbonless papers. They found the fraction of wheat starch from 12 to 40 microns in size with at least 22% of the particles being 22 microns or larger was equivalent to arrowroot starch in friction staining resistance. Fractionation required a cyclone separator to produce the large sized particles suitable as a stilting material. However, since arrowroot starch is scarce and expensive, wheat starch is a desirable substitute.
• Carbonless paper is often used in the form of printed form-sets for preparing multiple copies of receipts, bills, and other business forms and form-sets are prepared by collating from 2 to 8 sheets.
• Form-sets are typically made by applying an adhesive to the edge of a stack of the carbonless paper.
• Each of the coated sheets in a form-set is somewhat porous and permits the adhesive to penetrate into the pores of the paper, such penetration being necessary to attain satisfactory adhesion of sheets within the form-set.
• Adhesives useful for edge-padding carbonless papers are described, for example, in U.S. Patent No. 5,079,068, the disclosure of which is incorporated herein by reference.
• the adhesively bound papers are then "fanned-out” to separate into individual form-sets.
• carbonless copy paper form-sets often have a release coating (for example, a fluorocarbon or silicone coating) applied to at least one of the outer faces of each form-set.
• a release coating for example, a fluorocarbon or silicone coating
• Pad coats function as an abhesive (or non-adhesive) to provide low adhesion properties to the outer faces of a form-set; act as a release agent for the edge-padding adhesive; and promote "fan-out properties" in edge padding to allow the adhesively edge-padded stack to "fan-out” or “fan-apart” and separate into individual form-sets upon fanning.
• Individual form-sets are prepared by stacking the collated carbonless paper, trimming, edge-padding with an edge-padding adhesive, and fanning-out.
• Fan-out is a method of separating a stack or pad of multiple form-sets into individual form-sets.
• carbonless paper is prepared and packaged in precollated unpadded form-sets.
• the sheets are arranged in the order in which they will appear in the finished form.
• the coated back sheet (CB) is first in the form-set, the coated front sheet (CF) is last, and the required number of CFB sheets are in between.
• the paper may be prepared and packaged in precollated form-sets referred to as "reverse sequence form-sets,” wherein sheets of various colors and surfaces are arranged opposite to their normal functional order.
• the coated front sheet (CF) is first in the form-set, the coated back sheet (CB) is last, and the required number of CFB sheets are in between.
• Carbonless paper is widely used in the forms industry and carbonless paper forms have been printed in the past by conventional printing techniques such as offset printing, lithography, etc.
• conventional printing techniques such as offset printing, lithography, etc.
• electrophotographic copiers having dependable, high capacity collating systems and enhanced copy quality
• compatibility of the carbonless paper with the machine is critical.
• the base sheets upon which carbonless paper coatings are applied to form carbonless papers conventionally imaged via offset printing do not have sufficient stiffness or sufficient sensitivity to machine conditions for curl and moisture control to be handled in copier processors and sorters.
• Capsule rupture also leads to development of smudge marks on the CF coated surfaces because of transfer of the color former from the capsules to the developer.
• Capsule rupture also changes the imaging character of the carbonless paper, increasing the sensitivity of the paper and increasing the resistance to inadvertent capsule rupture, herein referred to as "scuff.”
• Sensitivity is an indication of the pressure needed to break the capsules and is significant in form-sets wherein 3 or more copies may be desired or heavier basis weight carbonless papers are used. It is desirable for sensitivity to remain low while “scuff" be as high as possible.
• Other changes in image density and in the speed of formation of the image may also be affected due to the reduced number of unbroken capsules on the CB sheet.
• a major problem encountered when precollated carbonless papers are used in friction fed machines is the formation of dense, noticeable smudge marks on CF sheets. Smudging occurs when two or more carbonless paper sheets enter the feed mechanism together and is believed to be caused by inadvertent capsule rupture and transfer of color-former from CB to CF surface. This problem is particularly acute when the copier uses a pressure roller or belt for pick up and feeding the sheet into the copier. This problem was addressed by Beery in WO 89/04804 who attributed the smudge to mechanical locking between the sheets due to the relatively high coefficient of friction between the sheet surfaces.
• His solution was to modify the feed rollers in the machine to make them softer, so that the pressure exerted on the capsule coated surface was reduced and less pressure was placed over the areas of the sheet engaged by the feed mechanism. While photocopier modification by changing the configuration and hardness of the feeding system represents one solution, machine modification is often costly and requires cooperation of the machine manufacturer. It would be advantageous to decrease smudge mark formation without machine modification. A more desirable solution would be to modify the paper surface to eliminate smudging in machine operation.
• Capsule rupture is reduced by preparing carbonless copy paper sheets in which the coefficients of friction of the various faces of the paper are kept within 0.1 units of each other. While this provides a dramatic improvement in reducing the extent of background staining in carbonless paper, smudging is still present. Further improvement is desired.
• the present invention provides a novel process for the transfer of an image to the surface of a sheet of carbonless paper comprising refined legume starch as a stilt material.
• the inventive process comprises the steps of:
• the carbonless paper comprises a donor (CB) sheet and a receptor (CF) sheet wherein the refined legume starch is pea starch and is contained in the dried coating on the donor sheet in amount of from 2 to 45 wt%, and more preferably, from about 4 to 25 wt%, based upon the total weight of the coating contained on the donor (CB) sheet.
• the refined legume starch granules have an average particle size ranging from about 10 to 50 microns and more preferably, from about 20 to 30 microns.
• the present invention provides carbonless paper with an image on the surface thereof produced by the foregoing disclosed inventive process, the carbonless paper comprising refined legume starch as a stilt material.
• the present invention provides an improved process for offset printing employing carbonless paper comprising refined legume starch granules as a stilt material.
• Refined legume starch particles when incorporated into carbonless paper as a stilt material, provide a completely unexpected improvement in the appearance of the printed sheet and reduce press and copier machine contamination compared to that observed when a wheat starch or other stilt materials are used.
• Carbonless papers printed on offset presses, electrographic or electrophotographic copier/duplicators, and laser printers display less smudge and scuff and exhibit reduced capsule rupture when compared with papers incorporating other stilting materials such as wheat starch.
• the refined legume starch granules have an average particle size ranging from about 10 to 50 microns and more preferably from about 20 to 30 microns.
• the refined legume starch may be used in any type of carbonless copy paper such as self-contained (SC) constructions, or those which comprise coated donor (CB) and receptor (CF) sheets.
• SC self-contained
• CB coated donor
• CF receptor
• the refined legume starch granules are present in the coating on the donor (CB) sheet in an amount of from about 2 to 45 wt%, and more preferably from about 4 to 25 wt%, based upon the total weight of the CB coating.
• Carbonless papers having microcapsules coated thereon are subject to premature rupture of capsules when subjected to pressure.
• Photocopiers and offset presses typically apply pressure to the paper sheets in many stages of machine operation. This results in capsule rupture. Preferentially, the larger capsules are ruptured. Destruction of these capsules and release of color-former cause smudging.
• Capsule rupture also changes the imaging characteristics of the carbonless paper, decreasing speed of image formation and making the paper less sensitive. Other changes in image properties may also be affected due to the reduced number of unbroken capsules on the CB sheet and increased resistance to further capsule rupture.
• a photoconductor is a material that is an insulator in the dark and which has the property of being able to transport electric charge when exposed to light.
• a latent image can be generated on the surface of a suitable imaging element utilizing either an electrographic or an electrophotographic process.
• An “electrographic process” is one which involves the production of images by addressing an imaging surface, normally a dielectric material, with static electric charges (e.g., as from a stylus) to form a latent image which is then developed with a suitable toner.
• the term is distinguished from an "electrophotographic process" in which an electrostatic charge latent image is created by addressing a photoconductive surface with light.
• the photoconductor may be either organic or inorganic.
• Solid toners typically contain a pigment or colorant, such as carbon black, either dispersed in or coated with a thermoplastic material.
• Liquid toners typically are in form of organosols comprising a pigment dispersed in a non-conductive, hydrocarbon medium.
• the latent image generated on the surface of the imaging element is developed with toner in any conventional manner, such as by electrophoretic or electrostatic disposition of the toner on the surface of the imaging element.
• the developed image may then be transferred from the surface of the imaging element to the surface of the carbonless copy paper by any conventional method used in either electrography or electrophotography such as by utilizing heat and/or pressure or the application of an electric field.
• capsule rupture may occur at several places in the copier where pressure on the paper is used to facilitate movement of the sheet through the copier.
• the first place where premature capsule rupture may take place is the feed assembly station where paper is fed into the copier from the paper tray.
• feed rollers introduce the top sheet from the stack of carbonless paper into the machine's paper path.
• the feeding of paper into printing presses or electrophotographic copiers depends upon individual sheets being fed from a stack of the paper, and the mode of transfer of the sheet into the printing press or photocopier varies with the machine.
• Printing presses and electrophotographic copiers are designed to feed paper into the machine by several mechanisms.
• the paper may be fed by a vacuum pickup and transfer system, by a roller or belt which exerts pressure on the top sheet in the stack, by a roller or belt which exerts pressure on the top sheet in the stack in combination with a retard roller or belt beneath the stack, or by other suitable means.
• a roller or belt pressed against the top sheet of the paper stack is employed as the feed means.
• These feed means move into engagement with the top sheet of the stack, exert pressure on the top sheet, usually by buckling the sheet, and releases and separates the sheet from the stack.
• the sheet can then be fed through "take away rolls” into the copier.
• the feed means usually remain at a fixed position in relation to the stack during sheet feeding.
• a forward moving belt removes the top sheet from a stack of paper and advances the sheet to a set of pinch rolls which then feed the sheet into the imaging and toner transfer stations.
• a retard roller under the feed belt catches any second sheet that begins to transfer with the top sheet.
• a smudge mark often develops on the CF surface of a sheet. Smudging is caused by CB capsule rupture and color-former transfer to the CF surface. Capsule rupture can be caused by the feed mechanism (such as a belt or roller) sliding across the paper. Capsule rupture can also be caused by double or multiple sheet feeds of carbonless papers into the feeder assembly and subsequent abrasion by the retard roller along the CB surface. Transfer of color-former from the CB sheet to the CF surface can take place in the paper feed mechanism as another sheet is fed, within the copier, or in the collection tray as the sheets lie on top of each other.
• a second location for capsule rupture is at the toner transfer station.
• the paper travels between the photoreceptor and a bias transfer roll where it is subjected to shear and pressure forces. Capsule rupture at this site causes release of the encapsulated solution of the color-former.
• the released solvent can wet the surface of the bias transfer roll and come into contact with toner.
• Toners are typically made of pigments such as carbon black in a polymer such as styrene-butyl methacrylate copolymer and can be readily plasticized by the color-former solvent to a soft tacky state.
• plasticized toner particles from the bias transfer roll back to the photoreceptor results in spots on the photoconductor and causes spots on the photocopies after a number of sheets have been printed.
• the plasticized toner can retransfer from the photoreceptor to the paper in non light-struck (i.e., background) areas to form specks about 200 to 300 microns in diameter.
• a third location where pressure is applied to the paper during the photocopying process is at the heat/pressure toner fusing station.
• the surface temperature of the heat roller is about 204°C (400°F) and the pressure is thought to be about 140 psi. Pressure at these points can again cause capsule rupture and release of the encapsulated color-former solution with resultant reduced performance of the carbonless system.
• Copier components particularly sensitive to solvent are wires which serve the purpose of transferring electrical charges to photoconductor belts, copy paper, or toner. Solvents may react with ions generated by these wires to form compounds that interfere with the function of these wires and other machine components and cause poor machine performance.
• the wires may be single wires or units commonly referred to as a corotron or a dicorotron. These wires are described in U.S. Patent No. 4,086,650.
• capsule rupture may occur at several places in the press where pressure on the paper is used to facilitate movement of the sheet during printing.
• drive rollers buckle a sheet paper and feed it to a grip mechanism. Pressure exerted by the drive rollers can break capsules.
• the grip mechanism grabs the edge of the paper and feeds it into the printing mechanism. The pressure exerted by the grip mechanism can also break capsules.
• the paper is fed between a blanket roll and an opposing impression cylinder. In this region, where machine adjustment is critical to insure efficient and uniform ink transfer to the paper under controlled pressure, additional capsule rupture can occur.
• Carbonless papers prepared with various stilt materials were evaluated before and after being printed in various electrophotographic copiers, and on offset printing presses.
• the printed papers were evaluated to determine changes in sensitivity, scuff, smudge, image speed, and ultimate image density.
• the amount of smudge originating in the copying or printing operation was measured.
• Tests were performed on coated CB sheets to determine their characteristics and acceptability for use. These tests include evaluation of imaging speed, and ultimate image density. Imaging speed measures the time to achieve an image acceptable for viewing and is controlled by the kinetics of the imaging reaction, while ultimate image density measures the image after complete reaction and is a measure of the thermodynamics of the imaging reaction.
• Imaging speed was determined by passing a CB and a CF sheet under a steel roller with an impact pressure of approximately 350 pli (pounds per linear inch) and measuring the reflectance of the resultant image four seconds after imaging.
• a Photovolt Model 670 Reflectance Meter with a Model 610 Search Unit fitted with a green filter was used. This instrument is available from Seragen Diagnostics, Inc., Indianapolis, IN. In interpreting reflectance numbers, a high number indicates high reflectance, and a low number indicates low reflectance. Thus a white surface would have a reflectance of close to 100, and a black surface would have a reflectance approaching zero. A "slower" imaging system would be expected to have a greater reflectance after 4 seconds than a faster imaging system.
• a high speed number indicates a weak, light image.
• a low speed number indicates a strong, dark image. Thus, the lower the value for speed, the darker the 4-second image. Lower speed values are desired.
• Ultimate image reflectance was also measured using the Photovolt Model 670 Reflectance Meter. Following image formation the imaged sheet was heated to 215 ⁇ 5°F (102 ⁇ 3°C) for 7 seconds to fully develop the image, and the reflectance was measured. A high ultimate image number indicates a weak, light image. A low ultimate image number indicates a strong, dark image. Thus, the lower the value for ultimate image, the darker the image. Lower ultimate image values are desired.
• Sensitivity was determined by placing a strip of CB paper on a strip of CF paper so as to form a 2-part form-set and then scribing the form-set with a set of ball point pens set 15/32'' apart with sufficient pressure to form a good image on the front surface.
• the form-set was then heated to 215 ⁇ 5°F (102 ⁇ 3°C) for about 10 seconds to fully develop the image.
• the optical density of the image was measured with a Photovolt Reflection Meter Model 670.
• a high sensitivity value indicates a weak, light image. The lower the sensitivity value, the more apparent the image is to a lighter pressure. Lower sensitivity values are desired.
• Scuff was determined by placing a strip of CB paper on a strip of CF paper so as to form a 2-part form-set and then applying a weight such that the two surfaces were in intimate contact but no capsules were broken. The CF sheet was then pulled across the CB sheet to initiate capsule rupture by the abrasive action of the movement of one sheet on the other. The CF sheet was then heated to 215 ⁇ 5°F for about 10 seconds to fully develop the image. The image density was again measured with a Photovolt Reflection Meter, Model 670. A high scuff value indicates a weak, light image. A low scuff value indicates a strong, dark image. Thus, the higher the scuff value, the more resistant the carbonless paper is to scuff. Higher scuff values are desired.
• Smudge is defined as the percent reflectance of the mark created in printing in the press or copier.
• the intensity of the smudge introduced at the leading edge of the paper by the pressure feed rolls was determined by measuring the percent reflectance of the smudge and subtracting this number from the base sheet background percent reflectance.
• Smudging results from CB capsule rupture during paper feed and subsequent color-former transfer to a CF developer sheet. Capsule rupture and consequent smudging is caused by the feed mechanism (such as a belt or roller) sliding across the paper and dragging the CF sheet over the CB sheet or vice versa. This commonly takes place under the force of the retard roller and nip rollers of the feed mechanism.
• smudge indicates the change (i.e. ⁇ ) in percent reflectance.
• a high smudge value indicates a strong, dark mark.
• a low smudge value indicates a weak, light mark. It is preferred to have low smudge values.
• Manifolding is the number of sheets through which a legible image is reproduced. Manifolding is determined by, for example, the ease of capsule breakage, paper thickness, and sensitivity.
• binder refers to the soluble-starch/styrene-butadiene latex/zinc rosinate in which the capsules and stilt are slurried.
• the soluble-starch should not be confused with the starch particles evaluated as stilt materials.
• the above formulations correspond to 5%, 15%, and 30% stilt based on dry capsule weight.
• the above formulations were coated to give a coat weight of 1.3 pounds per ream (1300 square feet) on 20 pound basis weight xerographic grade bond paper.
• the papers were fed through the feed mechanism of a Xerox 1090 copier as a precollated 2 part form-set. These papers were not printed upon in the machine.
• the intensity of the smudge introduced at the leading edge of the paper by the pressure feed rolls was then determined by measuring the percent reflectance of the smudge and subtracting this value from the percent reflectance of the base sheet. The difference in the amount of smudge generated was very evident upon visual examination of the printed sheets.
• a series of formulations was prepared varying the amount of binders and stilts.
• the stilt materials evaluated were Keestar-328, a wheat starch available from Ogilvie Mills, and Accugel, a refined pea starch available from Woodstone Co., Winnipeg, Canada.
• the levels of stilt were 0%, 40%, and 70% of the dry capsule weight.
• the color-formers, encapsulation procedures, binders, and coating methods are again similar to those described in U.S. Patent Nos. 3,516,846 and 5,084,433. All weights are in lb.
• the capsules accounted for 30.5% of the weight of capsule slurry.
• the formulations were roll coated to give the coating weights shown in the fifth column.
• Coat weight is in lb/ream (1300 ft2).
• Sample Weight of Capsule Slurry Wheat Stilt Pea Stilt Coat Weight Binder Weight A 479 lb 0 lb 0 lb 1.20 lb 317 lb B 479 lb 0 lb 0 lb 1.59 lb 317 lb C 467 lb 58 lb 0 lb 1.41 lb 348 lb D 467 lb 58 lb 0 lb 1.89 lb 348 lb E 409 lb 89 lb 0 lb 1.54 lb 333 lb F 409 lb 89 lb 0 lb 2.03 lb 333 lb G 478 lb 0 lb 58 lb 1.50 lb 348 lb H 478 lb 0 lb 58 lb 1.83 lb 348 lb I 431 l
• the change ( ⁇ ) between the initial and final values in Table 3 is an indication of how extensive the capsule rupture is in the printing operation.
• sample A where no stilt is present, and the coat weight is 1.2 pounds/ream the sensitivity increases 6.9 units, indicating large amounts of capsules were destroyed in the printing step. Scuff also increased by a large amount, 5.8 units, which also indicates extensive capsule rupture.
• sample C where wheat starch stilt was used at a 40% level (based upon dry capsule weight) and the coat weight of capsules was about the same as A, the sensitivity increased by 4.1 units and the scuff value increased by 2.1 units. This indicates less capsule rupture during printing and that the wheat starch is indeed affording increased capsule protection.
• CB sheets, prepared as in Example 2 were imaged in a Xerox 1090 copier and evaluated for smudge and scuff.
• the results, shown in Table 4, demonstrate that at both high and low coating weights, pea starch provides both lower smudge and higher scuff values than wheat starch.
• the lower smudge values and higher scuff values indicate that carbonless papers containing pea starch have a greater tolerance to handling.
• the following example compares the effect of different loadings of wheat starch and pea starch stilt materials on the sensitivity of sheets before and after imaging.
• CB sheets, coated as in Example 2 were prepared and imaged in a Xerox 9900 copier.
• the sensitivity of the sheets was determined before (initial) and after (final) imaging in the photocopier and the change ( ⁇ ) in sensitivity determined by subtraction.
• the increase in sensitivity values of carbonless papers incorporating pea starch as a stilting material is much lower than samples incorporating wheat starch as a stilting material. This indicates much less capsule rupture during the printing operation.
• a formulation was prepared with a binder of Vinol 205 polyvinyl alcohol (13 wt. % solids, available from Air Products Co., Allentown, PA) in place of the latex/starch combination of the prior examples.
• the capsule/binder ratio in this formulation was more than double that in the earlier examples.
• the formulation was prepared by mixing: Water 416 lb Capsules (wet) 454 lb (177 lb dry wt) Stilt 55 lbs Binder Materials (11.4%) 275 lb
• the stilt used was again wheat starch or pea starch.
• a control formulation was prepared without stilt, as well.
• the formulations were coated to give a coat weight of 1.2 pounds per ream.
• the sheets were printed in a Xerox 1090 photocopier and the smudge and scuff were measured, with the following results.
• Table 6 Effect of Stilt With Poly(vinyl alcohol) Binders on Xerox 1090 Copier Stain Sample Smudge Scuff Coating Weight Control (No Starch) 45.8 60.6 1.18 35.2 63.9 1.53 40% Wheat Starch 23.6 73.6 1.32 23.0 72.5 1.60 40% Pea Starch 20.1 74.2 1.08 16.6 75.4 1.42

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