US3458336A - Pressure sensitive transfer sheet having screen layer and method of making - Google Patents

Description

y 1969 D. A. NEWMAN PRESSURE SENSITIVE TRANSFER SHEET HAVING SCREEN LAYER AND METHOD OF MAKING Filed Feb. 14, 1967 V h l e 'r I N N pouylas A Newman M w W 4r7 0E/ E Y3 United States Patent 3,458,336 PRESSURE SENSITEVE TRANSFER SHEET HAVING SCREEN LAYER AND METHOD OF MAKING Douglas A. Newman, Glen Cove, N.Y., assignor to Columbia Ribbon and Carbon Manufacturing C0., Inc, Glen Cove, N.Y., a corporation of New York Filed Feb. 14, 1967, Ser. No. 616,026 Int. Cl. B41m 1/24; 844d 1/22 US. Cl. 117-15 8 Claims ABSTRACT OF THE DISCLOSURE Novel pressure-sensitive carbonless copying system comprising squeeze-out type donor sheet including colorforming reagent and receptor sheet including complementary reactive reagent, the donor coating being provided with an open fine screen layer which spaces the donor and receptor layers and yet is open to the pressure-transfer of the donor chemical; and the process of manufacturing such a system.

There are many known carbonless copying systems or no-carbon-required systems which have met with varying degrees of success in eliminating the necessity and disadvantages of carbon paper in forms. Possibly the most successful system employs the donor chemical in an encapsulated form whereby the shell of the capsules provides a barrier between the donor and receptor chemicals in the form and prevents overall reaction therebetween except in areas where the capsules are ruptured by imaging pressure.

There are other systems which employ the donor chemical in a pressure-transferable layer, such as one based upon a wax binder material, covered by a protective supercoating which is either rupturable or pressure-transferable and which prevents premature reaction between the donor and receptor chemicals until imaging pressure is applied.

While these known systems have many advantages, there is certainly room for much improvement. Images formed from encapsulated donor chemicals are generally quite weak in tone or density and tend to fade with age, apparently due to the inability to include a sufiicient quantity of donor chemical and vehicle in the capsules. In other types of donor sheets where the donor chemical is present in a solid binder material, such as wax, the binder continues to act as a barrier even after transfer to the receptor sheet so that a large quantity of the transferred donor chemical is unable to react with the receptor chemical and the formed images are weak and fade quickly.

Due to the low intensity of the images formed and their tendency to fade quickly, it is not possible to produce many duplicate copies simultaneously since the defects of the copies increase as the imaging pressure is cushioned by the thickness of the multi-part form.

It is the primary object of the present invention to provide a donor-receptor manifolding system in which the donor chemical is easily transferable to a receptor sheet in liquid form and in large quantity and yet which is protected against contact with the receptor chemical until imaging pressures are applied to produce strong, faderesistant images.

It is another object of this invention to provide a carbonless copy manifolding system which is stable to premature development in unintended areas and yet is so sensitive to imaging pressure to permit the simultaneous production of up to eight or more duplicate copies having strong, fade-resistant images.

These and other objects and advantages of this inven- 3,458,336 Patented July 29, 1969 tion will be clear to those skilled in the art in the light of the present disclosure including the drawings in which:

FIGURE 1 is a perspective view of a donor sheet according to the present invention.

FIGS. 2 and 3 are perspective views of a continuous web carrying a donor coating and being printed thereover with different types of open screen layers in continuous manner.

FIG. 4 is a diagrammatic cross-section, to an enlarged scale, of a donor sheet-receptor sheet system according to this invention.

The present novel donor sheet-receptor sheet carbonless copy system comprises a conventional type receptor sheet in association with a novel donor sheet which comprises a substantially non-transferable film-forming squeeze-out type donor layer containing the donor chemical in a liquid vehicle and having over the transfer layer a substantially non-transferable open fine screen of filmforming material having openings through which the donor chemical can be exuded to the receptor sheet under the effects of imaging pressure.

The essence of this invention resides in the combination of the squeeze-out type donor layer and the open fine screen thereover. Squeeze-out type imaging layers are well-known in the carbon paper field and are exemplified by U.S. Patents Nos. 2,820,717; 2,944,037; 3,037,879 and 3,117,018. Such layers comprise a non-transferable porous network of synthetic thermoplastic resin containing within the pores a pressure-exudable ink comprising an oily vehicle and coloring matter. Up until the present invention such layers could not be used in the carbonless copy field because they tend to have a Wet surface due to the sweating of the ink because of its incompatibility with the resinous binder. Thus casual contact of such a layer with a reactive receptor layer results in overall color formation. While such sweating can be overcome by the use of a solid ink vehicle, such as lanolin, this reduces the pressure sensitivity of the layer and introduces a pressure-transferable solid which can mask the donor chemical from reaction with the receptor chemical. The use of a protective layer over the squeeze-out layer also has these same adverse elfects.

I have now discovered that it is not necessary to prevent the sweating of the squeeze-out layer or to apply a continuous protective coating thereover, with resultant disadvantages, in order to adapt squeeze-out type layers for use in the carbonless copy field. I have discovered that such squeeze-out type layers provide excellent results as carriers for reactive color-forming chemicals in forms provided that they are printed with an open nontransferable fine screen of film-forming composition which serves to space the squeeze-out layer from the receptor layer but which does not hinder the transfer of the color-forming chemical.

The open screen layers suitable for use according to the present invention may have several different forms and structures. The preferred structure is that show in FIG. 1 of the drawings in which the screen consists of intersecting strips to form discrete openings. Such a screen is preferably applied as shown in FIG. 2 by means of an offset printing technique. A thin layer of a solution of the synthetic thermoplastic film-forming composition is supplied from a solution fountain (not shown) to applicator roll 15 using a doctor blade (notshown) to control the thickness. The applicator roll transfers a thin layer of the solution to the peaks of a printing cylinder 16 containing raised line areas or peaks 17 and discrete valleys 18 which receive no ink. The donor sheet is expended from supply roll 40 and is passed in the nip between the printing cylinder 16 and an impression roll 41 whereby the donor layer 12 is overprinted with screen layer 13. The printed web is then heated to evaporate the solvent and dry the screen layer prior to the rolling of the final web on take-up roll 42.

According to another embodiment, illustrated by FIG. 3, the open screen layer may have a gravure structure which is a negative of the structure shown in FIG. 2 in that the screen has open intersecting line areas 22 which surround spaced islands or spots 23 of the synthetic thermoplastic film-forming composition. Such a structure is formed in the manner shown in FIG. 1 whereby the printing cylinder 16 is coated with a solution of the film-forming composition by immersion in a solution fountain (not shown) and a doctor blade (not shown) is used to scrape the solution from the peaks 17 of the cylinder so that only the discrete valleys 18 of the cylinder contain a supply of the solution. The solution is printed over the donor layer and dried to form a screen of the type shown.

It should also be pointed out that it is not necessary that the open screen layers of the present invention have a square configuration consisting of intersecting printed or unprinted areas as shown in FIGS. 2 and 3. The printing cylinder may have its raised area or peaks in the form of closely spaced parallel lines running in only one direction and forming between them hollow depressions or valleys which are also parallel and uninterrupted. Such screens may also be applied according to the techniques of either FIG. 2 or FIG. 3.

FIG. 4 shows a donor sheet and a receptor sheet 20 in position for imaging but spaced for purposes of illustration. The receptor sheet has a flexible foundation 21, such as paper or plastic film, carrying a receptor layer 22 containing a chemical which is reactive with the chemical of the donor sheet to form an intenselycolored reaction product.

Aside from the substitution of a substantially colorless color-forming chemical for the pigment, the squeezeout type donor layers of the present invention may be the same as those of any of the aforementioned U.S. Patents and may be applied to their flexible foundations in the manner taught by said patents.

The selection of the color-forming chemicals is a matter of choice depending upon the color desired and it will be obvious to one skilled in the art to use any of the conventional combinations of color-forming chemicals which are commercially available. Acid-sensitive colorless dye bases perform in a most satisfactory manner as the donor chemical in combination with receptor sheets coated with acidic electron acceptor materials such as bentonite, attapulgite and the like. US. Patents Nos. 2,981,733 and 2,548,366 are illustrative of such color-formers, and the receptor sheets of these patents are useful in the present invention. Also reactive colorforming dye components may be used as the donor and receptor chemicals as taught by US. Patent No. 3,244,548. US. Patent No. 3,011,905 is also illustrative of colorformers such as color-forming salts which are useful ac cording to this invention. In all cases the receptor coatings of the prior art are useful in the present invention and it is only the donor sheets which differ in structure and formulation from prior known donor sheets.

The novel donor sheets of the present invention have the donor chemical present in a resinous layer which comprises a porous network of non-transferable synthetic thermoplastic resin containing within the pores thereof a pressure-exudable liquid which is substantially incompatible with the resin and which functions as a vehicle for the color-forming donor chemical which is dissolved or dispersed therein. I have found that such a layer is exceptionally suitable for use in the carbonless copy fiield because it delivers the donor chemical in liquid form, free of masking solids, and in sufiicient concentration to produce sharp, clear images of deep and immediate intensity. However, due to the liquid nature of the squeeze-out composition, the placement of the printed screen over the donor layer forms an essential and critical element of the invention.

The open screen layer 13 is applied over the donor coating by conventional printing techniques such as by means of etched intaglio printing cylinders, as shown by FIGS. 2 and 3 of the drawing, or by screen printing. It should be pointed out that the open layer need not have the configuration of a straight or square screen, as shown in FIG. 1, but rather may consist of parallel strips or lines which are curved or zigzag or which intersect at any desired angle.

The open screen layer comprises a synthetic thermoplastic film-formiug binder material such as a vinyl resin, acrylic resin, cellulose plastic, or the like, and may contain coloring matter such as white pigment, metallic lamelliform particles, carbon black, or the like, in order to give the surface of the donor sheet any desired color. However, the screen layer is not pressure-transferable and the color thereof is for decorative purposes and takes no part in the imaging of the receptor sheet. The screen layer is preferably applied as a solution of the binder in a volatile organic solvent which is a non-solvent for the resin network of the donor layer. The selection of appropriate binders and solvents for the screen layer will depend upon the resin used in the donor layer and will be obvious to one skilled in the art. In general the same resins and solvents taught by US. Patents Nos. 2,820,717; 2,944,037; 3,037,879 and 3,117,018 as useful for producing carbon papers can also be used in the present donor layers and open screen layers except that different resins must be used in the donor and screen layers so as to avoid dissolving the donor resin with the screen layer solvent.

It is also possible to print the screen layer on the donor layer in the form of an organosol or plastisol using little or no volatile solvent but incorporating liquid plasticizers which are solvents for and become part of the resin at high temperatures after printing onto the donor layer.

In all cases the open screen layer comprises intersecting strips which are at least 0.00001 inch and no more than 0.01 inch in height and thickness and are spaced from parallel strips by at least 0.00001 inch and not more than 0.01 inch. The strips are preferably between 0.001 inch and 0.0001 inch in height and thickness and are spaced by from about 0.05 inch to about 0.0001 inch.

The following example is given by way of illustration and should not be considered limitative.

A continuous web of 0.5 mil polyethylene terephthalate polyester film (available under the trademark Mylar) is coated with a donor layer having the following composition.

Ingredients: Parts by weight, gm. Vinyl chloride-vinyl acetate copolymer (Vinylite VYHI-I) 10.0

Mineral oil 5.0 Butyl stearate 7.5 Bis(p-dimethylaminophenyl) N methylpiperazinyl methane Toluene 15.0 Ethyl acetate 45.0

The colorless methane derivative is preferably first dissolved in a portion of the toluene and added to the oils in which it is at least partially soluble. The coating is dried by evaporation of the solvents to form a porous resin structure containing the oil phase as a pressureexudable liquid solution of the methane derivative. The donor layer has a thickness of about 0.001 inch.

Next the coated web is printed in the manner shown by FIG. 2 of the drawing with an open screen layer of the following composition.

Ingredients: Parts by weight, gm. Ethyl cellulose 10 Ethyl alcohol 40 Bronze powder 2 The ethyl alcohol is evaporated to leave the open screen layer which masks the donor coating from view with the naked eye but which contains a multiplicity of openings through which the donor chemical can be exuded under the effects of imaging pressure. The ethyl cellulose screen consists of intersecting strips which are about 0.0001 inch in height and width and which are spaced by about 0.001 inch.

The donor web is cut into sheet lengths for manifolding use in association with acidic copy sheets. Some copy papers are sufliciently acidic to develop the donor chemical without the necessity of applying an acidic coating thereto because of the presence of residual alum in the paper stock itself. However, other papers require impregnation with weak acids such as boric acid, lactic acid, benzoic acid, or the like, or application of an acidic coating which is preferably an electron acceptor material such as bentonite, attapulgite, or the like.

The donor and receptor sheets may be used in the manner shown in FIG. 4 or may be coated on opposite sides with the donor and receptor layers for use in forms work for the simultaneous imaging of up to eight copies.

The printing cylinders useful according to the present invention are commercially-available engraved rolls having fine linear peaks at the rate of from about 50 to about 200 per inch, the depressions between the peaks being from about 0.00001 inch to about 0.01 inch in depth.

Variations and modifications may be made within the scope of the claims and portions of the improvements may be used without others.

I claim:

1. Pressure-sensitive carbonless copying system including a donor sheet comprising a flexible foundation sheet having thereon a donor layer comprising a non-transferable porous network of synthetic thermoplastic resin binder material containing within the pores thereof a pressure-transferable liquid comprising an oil which is substantially incompatible with said binder material and a substantially-colorless chemical, and a receptor sheet comprising a flexible foundation sheet carrying a second substantially-colorless chemical capable of reacting with said donor chemical on contact therewith to form an intensely-colored reaction product, characterized in that said donor layer has printed onto the surface thereof a multiplicity of uniform, parallel, non-transferable strips of synthetic thermoplastic resin, said strips being between 0.00001 inch and 0.01 inch in height and thickness and being uniformly spaced from each other by from 0.00001 inch to 0.01 inch in distance, the spaces between said strips permitting the unimpeded free transfer of said donor chemical to said receptor sheet under the effects of imaging pressure to form intensely-colored images thereon which appear substantially unbroken to the naked eye, while said strips space said donor layer from said receptor sheet to prevent contact between said chemicals in unimpressed areas.

2. System according to claim 1 in which the donor layer comprises a vinyl resin binder material and the pressure-transferable liquid comprises a solution of the donor chemical in the oil.

3. System according to claim 1 in which said strips are from about 0.001 inch to 0.0001 inch in height and thickness and are spaced from parallel strips by from about 0.05 inch to 0.0001 inch.

4. System according to claim 1 in which said donor chemical is acid-sensitive and said second chemical is acidic.

5. Process for producing a donor sheet for use in a carbonless copy system which comprises the steps of:

(a) coating a flexible foundation sheet with a composition comprising a film-forming binder material, a non-volatile oily material which is incompatible with said binder, a substantially-colorless color-forming donor chemical and a volatile solvent;

(b) evaporating said solvent to form a donor layer comprising a non-transferable porous network of said binder material containing within the pores thereof a pressure-transferable liquid comprising said oily material and said donor chemical;

(c) printing over said donor layer, in the form of a multiplicity of uniform parallel strips, a composition comprising a solution of a synthetic thermoplastic resin in a volatile solvent which is a non-solvent for the binder material of the donor layer; and

(d) evaporating said volatile solvent to form a multiplicity of uniform, parallel, non-transferable strips of said resin bonded to said donor layer, said strips being between 0.00001 inch and 0.01 inch in height and thickness and being uniformly spaced from each other by from 0.00001 inch and 0.01 inch in distance, the spaces between said strips permitting the unimpeded free transfer of said donor chemical to a receptor sheet containing a color-forming reactive chemical under the effects of imaging pressure to form intensely-colored images thereon which appear substantially unbroken to the naked eye, while said strips are adapted to space said donor layer from a receptor sheet in contact with said strips to prevent contact between said chemicals in unimpressed areas.

6. The process according to claim 5 in which said strips are from about 0.001 inch to 0.0001 inch .in height and thickness and are spaced from parallel strips by from about 0.05 inch to 0.0001 inch.

7. Donor sheet for use in the carbonless copying system which comprises a flexible foundation sheet having thereon a donor layer comprising a non-transferable porous network of synthetic thermoplastic resin binder material containing within the pores thereof a pressure-transferable liquid comprising an oil which is substantially incompatible with said binder material and a substantiallycolorless color-forming donor chemical, and having printed onto said donor layer a multiplicity of uniform, parallel, non-transferable strips of synthetic thermoplastic resin, said strips being between 0.00001 and 0.01 inch in height and thickness and being uniformly spaced from each other by from 0.00001 inch to 0.01 inch in distance, the spaces between said strips permitting the unimpeded free transfer of said donor chemical to a receptor sheet containing a color-forming reactive chemical under the effects of imaging pressure to from intensely-colored images thereon which appear substantially unbroken to the naked eye, while said strips are adapted to space said donor layer from a receptor sheet in contact with said strips to prevent contact between said chemicals in unimpressed areas.

8. Donor sheet according to claim 7 in which said strips are from about 0.001 inch to 0.0001 inch in height and thickness and are spaced from parallel strips by from about 0.05 inch to 0.0001 inch.

References Cited UNITED STATES PATENTS 1,962,082 6/1934 Miller 11736.4 2,213,645 9/1940 Antrim 1l736.4 2,790,742 4/1957 Wharton 117-36.4 2,803,579 8/1957 Stolle et a1 11736.4 3,080,954 3/1963 Newman et al 11736.4 3,104,980 9/1963 Maierson 11736.4 3,260,612 7/1966 Dulmage et al. 11736.2

MURRAY KATZ, Primary Examiner US. Cl. X.R.

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