US3368989A - Image transfer compositions comprising ethylene-vinyl acetate or ethyleneethyl acrylate copolymer, wax and incompatible plasticizer - Google Patents

Description

Feb. 13. 1968 R. R. WISSINGER ET AL 3,368,989

IMAGE TRANSFER COMPOSITIONS COMPRISING ETHYLENE-VINYL ACETATE OR ETHYLEINE-ETHYL ACRYLATE COPOLYMER, WAX AND INCOMPATIBLE PLASTICIZER Filed Oct. 27, 1966 ROSA-P7 P. W/SS/A GEA GERRY H. E'HIPHARDT A 7' ram/5 y.

United States Patent ()filice 3,368,989 Patented Feb. 13, 1968 3,368,989 IMAGE TRANSFER COMPOSITIONS COMPRISING ETHYLENE-VINYL ACETATE R ETHYLENE- ETHYL ACRYLATE COPDLYMER, WAX AND IN- COMPATIBLE PLASTICIZER Robert R. Wissinger, Des Moines, and Gerry H. Ehrhardt, West Des Moines, Iowa, assignors to Pacific Industries Inc., San Francisco, Calif., a corporation of California Continuation-impart of applications Ser. No. 292,392, July 2,1963, and Ser. No. 307,615, Sept. 9, 1963. This application Oct. 27, 1966, Ser. No. 590,024

16 Claims. (Cl. 26023) ABSTRACT OF THE DISCLOSURE An improved pressure sensitive transfer media constituted by a carrier su-bstrate having a transfer coating formed of a relatively small amount of a high molecular weight copolymer of ethylene and a mono-ethylenically unsaturated monomer, selected from the group consisting of vinyl acetate and ethyl acrylate in a wax base in association with a pigment and an incompatible plasticizer.

This invention relates to transfer media of improved character and more particularly to an improved pressure sensitive transfer media characterized by essentially complete release from a carrier substrate and production of transferred images of markedly uniform definition and intensity and withincreased smudge or smear resistance.

This application is a continuation-in-part of our applications Ser. No. 292,392, filed July 2, 1963, and Ser. No. 307,615, filed Sept. 9, 1963, both now abandoned.

Transfer material of the conventional carbon paper type has been used for many years for image transfer purposes with generally good results. However, the increasing use of data processing equipment with automatic image scanning systems, such as magnetic and optical readers, and the increasing-demand for increased numbers of copies in high speed printers and like apparatus has created a need for transfer media capable of producing transfer images of improved character and, in particular, transfer images Which are more highly smear and smudge resistant, have markedly uniform definition and intensity and which are capable of producing and reproducing effectively identical signal levels in automatic sensing equipment. While the transfer images produced with ordinary carbon paper formulations will remain sufficiently legible under most conditions, such images have the tendency to smear or spread out or otherwise lose definition when used in conjunction with card feeders or other handling components normally associated with data processing equipment. Such smearing or other loss of definition not only greatly impairs the capability for automatic image scanning thereof but also renders the transferred image generally less legible.

for all purposes. Such ordinary carbon papers also have the tendency of effecting non-uniform image transfer as well as transferring images of insufficient intensity or uniformity to produce acceptable signal levels or images of non-uniform character or dimension because of poor release of the transfer coating from the carrier sheet, all of which impair accurate automatic scanning thereof.

Insofar as ordinary carbon paper formulations, as referred to above, are concerned, a high degree of smear resistance, sharpness of transfer and intensity of transferred image constitute essentially antithetical requirements and a greater degree of one such advantageous characteristic can normally only be obtained at the expense of the others.

This invention may be briefly described as an improved transfer media of novel formulation both as to constituent elements and quantity and which, in its broad aspects, includes a selected ethylenic copolymer resin component in cooperative association with selected wax and pigment components and whose properties are markedly modified by an incompatible plasticizer component to complementally obtain, at least to a markedly improved degree, the heretofore antithetical characteristics of a high degree of smear resistance, sharpness of transfer and intensity of transferred image.

Among the advantages attendant the subject invention is the provision of an essentially complete release of the transferred image from a carrier substrate which, apart from the permitted utilization of thinner transfer films, in association with appreciably higher degrees of smear and smudge resistance, sharpness of transfer and uniformity of both definition and intensity of the transferred image results in an improved product of wide utility. Another advantage of the subject invention is the provision of an improved transfer media that is readily fabricatable by hot melt techniques on conventional equipment. A further advantage of the subject invention is the provision of a transfer image capable of use in heat tranfer, transfer posting, and in hectograph type reproduction systems. Still another advantage is the provision of a transfer media of markedly improved cleanliness both in normally occasioned handling and in specialized handling as encountered in data processing equipment.

The principal object of this invention is the provision of transfer media of improved character characterized by essentially complete release of the transfer image from a carrier substrate and by production of transferred images of markedly uniform definition and intensity and with increased smear resistance.

Another object of this invention is the provision of a transfer media adapted to provide a transfer image that will be highly smudge resistant to normal handling operations or to its passage through data processing equipment.

A further object of this invention is to provide a transfer media characterized by transfer images having marked uniformity of definition, dimension and'intensity and of such character as to effect sufficiently high signal levels to facilitate accurate reading thereof by automatic sensing equipment in data processing apparatus.

A still further object of this invention is the provision of a transfer media of improved cleanliness and which is characterized by essentially complete release of the transfer image from a carrier sheet for use with high speed data processing output printers.

A still further object of this invention is the provision of a pressure sensitive transfer media which will produce not only images of improved smear resistance but which will also be of increased definition and improved legibility.

A still further object of this invention is to provide means for producing a transfer image capable of use in heat transfer, transfer posting, hectograph paper and other image transfer products in which uniformity, cleanliness and definition of image and complete release of the image from a carrier substrate are of utmost importance.

Other objects and advantages of the invention will be pointed out in the following specification and claims and will be apparent from the accompanying drawings which illustrate one embodiment incorporating the principles of the invention and in which:

FIGURE 1 is an enlarged longitudinal sectional view of the transfer medium consisting of the transferable coating and the carrier sheet.

FIGURE 2 is an enlarged sectional view of the copy formed by the transfer of the image from the transfer medium.

FIGURE 3 is an enlarged sectional view of the transfer medium after the image has been transferred.

As illustrated, the transfer medium includes a carrier sheet or substrate 12 and a transfer coating 14, disposed on the surface thereof. The carrier sheet can be any type of film or carbonizing tissue conventionally employable for transfer media. The carrier sheet can be coated with the herein disclosed transfer coating by any of the various well known methods utilizable for hot melt type formulations.

As indicated earlier, the transfer film 14 is a formulation of particular quantities of a selected ethylenic copolymer in cooperative homogeneous association with selected wax and pigment components and an incompatible plasticizer. The selected resins comprise high molecular weight copolymers of ethylene and a mono-ethylenically unsaturated monomer selected from the group consisting of vinyl acetate and ethyl acrylate.

The preparation of ethylene-vinyl acetate copolymers is described in US. Patents Nos. 2,490,550 and 2,492,760 and such ethylene-vinyl acetate copolymers are commerically available, for example, under the trademark Elvax resins. Such resins suitably have estimated molecular weights in the order of 150,000 and greater, for example up to about 270,000, as calculated by the weight average molecular weight method.

The subject high molecular weight ethylene-vinyl acetate copolymers are of amorphous character, have a vinyl acetate content ranging from about 17 to 42%, refractive indices varying from about 1.476 to 1.493, tensile strength (per ASTM D882) of from about 500 to 3000 psi, melt indices of from 1.6 to 470 g./10 m. (per ASTM D1238 modified) and softening points (ring and ball ASTM E28) of from about 180 F, to 370 F.

The ethylene-ethyl acrylate copolymers are commercially available, for example, under the trademark Zetafin resins. According to the manufacturer such Zetafin resins are characterized by greatly increased flexibility and increased clarity and flow over conventional low density polyethylene resins. Such high molecular weight copolymers are non-hygroscopic, have an ethyl acrylate content ranging from about to and a tensile strength at yield from about 450 to 700 p.s.i. (as per ASTM D412- SIT). The ultimate strength thereof varies from 800 to 2000 p.s.i. (as per ASTM D63858T and D412-51T) depending on the type of moulding used. This material also has a melt index of from about 2.5 to 18.5 (as per ASTM D1238-57T), a density of about 0.928 to 0.952 (as per ASTM Gradient Column test), a Shore D hardness of from about 30 to and a Shore A hardness of from about 88 to 90 (as per ASTM 131706-591"), a low temperature brittleness test of a minus 70 C. (as per ASTM D74657T) and a vicat softening temperature varying between 125 to 150 F.

These copolymers are also believed to possess a high degree of polarity and an appreciable film forming ability and to have a relatively low tensile strength as compared to other resins of similar high molecular weight.

It was found that any of the ethylene-vinyl acetate copolymers could be used. The results using the available ditferent high molecular weight copolymers varied somewhat but good results were obtained with all of the copolymers which were tested. The quantity of ethylenevinyl acetate copolymer employed generally varies in inverse relation with the molecular weight thereof and in direct relation with proportional vinyl acetate content of the copolymer as well as in general accord with the end use of the product, More specifically, ethylene-vinyl acetate copolymers having a vinyl acetate content of 17 to 29% are preferred and optimum results appear to be obtained using a copolymer having about 27 to 29% vinyl acetate content. Such preferred copolymers have melt indices of about 2.1 to and those giving optimum results have melt indices of from about 5 to 28. The quantity of ethylene-vinyl acetate copolymer may vary between limits of 1 to 25% by weight of the total formulation but percentages above 20% appear to provide only marginal results and a preferred range of the selected resin component will be from 4 to 14% thereof, with the lower percentages being correlated to the higher range of the noted high molecular weight resins and the higher percentages being correlated to the lower range of the noted high molecular weight resins.

While the use of the specified ethylene-vinyl acetate copolymers is generally preferred, the ethylene-ethyl acrylate copolymers can be used in place of and in the same proportion as the ethylene-vinyl acetate copolymers in the various formulations incorporating the principles of this invention.

The wax components constitute the greatest percentage component of the ink film or transfer coating 14. While the type and amount of the wax is primarily selected to achieve a suitable coating viscosity to facilitate the application of the transfer film to the carrier by utilization of the so-called hot melt techniques, it also is at least partially determinative of the adhesive and cohesive properties of the transfer coating 14, as well as the hardness thereof. The cohesive forces referred to exist within the transfer film and affect the shearing characteristics thereof to permit a sharp fracture or shearing of the film under impact pressure. In contradistinction therewith the adhesive properties referred to are primarily concerned with the adhesion of the transferred image to its receptor sheet and, to a lesser extent, with the adhesion of the transfer film to the carrier sheet. The base wax component suitably comprises a hydrocarbon wax selected from the group consisting essentially of parafiin waxes or micro-crystalline waxes in amounts up to about 75% by weight of the coating constituents although a preferred range therefor is from about 30 to 75%. If desired, combinations of the' above paraffin and microcrystalline waxes may be employed as well as with minor additions of carnauba and montan waxes.

The type or kind and the amount of pigment used in the formulations does not appear to be critical and is determined by the nature of the desired copy and final use of the transfer medium. The transfer coating can be made in almost any desired color and intensity. For example, if the transfer film is to be used as a magnetic coating, a magnetic material will be used in a large percentage, whereas, if the transfer images are to be used as a heat transfer type of coating, a large percentage of pigment and dyes will be used. Likewise, for an optical scanning carbon a small percentage of pigment will be used. The percentage of pigment will also vary for other copy methods depending on the results desired and the type of equipment executing the form. Apparently pigments in amounts up to as high as 50% by weight may be employed although the preferred amount thereof will normally fall below 30% for most uses and will usually fall in the range of 5% to 10%.

The plasticizer component apparently functions as a release agent as well as a lubricant during formulation and must be of such nature as to be substantially incompatible with the selected ethylene-vinyl acetate or ethylene-ethyl acrylate copolymer and with the wax component of the formulation. That is, the plasticizer component should be such as to naturally separate from the selected ethylenic copolymer resin component after mix- Formulations, in terms of percent by weight, which provide transfer films having the desired improved characteristics include the following for transfer media adapted for typewriter use:

Percent Ethylene-vinyl acetate or ethylene-ethyl acrylate copolymer 15 Paraffin wax 60 Castor oil 15 Carbon black Ethylene-vinyl acetate or ethylene-ethyl acrylate copolymer 8 Hard microcrystalline wax 72 Castor oil 10 Carbon black 10 and the following for general pressure applications Percent Ethylene-vinyl acetate or ethylene-ethyl acrylate copolymer 12 Paraffin wax 53 Castor oil 25 Blue pigment 10 Ethylene-vinyl acetate or ethylene-ethyl acrylate copolymer 6 Soft microcrystalline wax 64 Castor oil 20 Milori blue 10 and the following for an optical scanning carbon Percent Ethylene-vinyl. acetate or ethylene-ethyl acrylate copolymer 10 Paraffin wax 65 Castor oil 20 Carbon black 5 and the following for a heat transferable carbon Percent Ethylene-vinyl acetate or ethylene-ethyl acrylate copolymer 6 Hard microcrystalline wax 30 Soft parafiin Wax -1. 24 Castor oil 20 Carbon black 20 sheet 16'. A void 22 is created in the transfer coating 14 by the separated image 20 adhering to the receptor sheet 16. This phenomenon takes place because the cohesive forces of the transfer coating 14 are less than the force of pressure of impact which creates a shearing action at points 24 and 26 and which effects the separation and release of image 20. The adhesive forces between the engaging surfaces of the transferred image 20 and the receptor sheet 16 are greater than the adhesive forces between the transfer coating 14 and the carrier sheet 12, whereupon the image 20 becomes firmly fixed to the receiver sheet 16.

While the theoretical explanation underlying the improved characteristics obtained by the apparent complemental combination of characteristics heretofore regarded as antithetical in the subject invention is not fully understood at the present time, it is believed that such are attributable in large part to the particular resinous copolymer of ethylene and mono-ethylenically unsaturated monomer and quantity thereof employed in combination with the wax component and as modified by the specified use of the incompatible plasticizers component which apparently alters the properties thereof. More specifically it is believed that the specified high molecular weight ethylene-vinyl acetate and ethylene-ethyl acrylate copolymers, due perhaps to their polarity or to the size and length of the molecules forms a matrix for the wax and pigment components which not only minimizes, if not actually prevents, migration of the ink film components across the carrier sheet interface but which also so increases the cohesive forces within the transfer film as to effect sharp shearing thereof under impact pressure with an attendant and unusual increase in smear and smudge resistance. It is further believed that such complemental combination of normally antithetical properties is also largely attributable to the utilization of selective amounts of the specified incompatible oily liquid plasticizer. More specifically it is believed that such lasticizer maintains its integrity within the matrix and migrates or is otherwise present in suflicient quantity at the transfer film-carrier sheet interface to decrease the adhesive forces intermediate the transfer film and the carrier sheet and prevent the transfer film from looking to the carrier sheet and thus to subsequently permit a complete release therebetween in response to impact pressure.

As mentioned earlier, the outstanding feature of this invention is the effecting of the full release of the transfer film from the carrier sheet in response to impact pressure in integral association with the complemental combination of the heretofore antithetical characteristics of a high degree of smear resistance, sharpness of transfer and intensity of transferred image.

Having thus described our invention, we claim:

1. An improved transfer coating composition for effecting selective image transfer to an abutting receiving surface in response to application of impact force to a carrier sheet coated therewith, comprising a mixture of not greater than 20% by weight of a high molecular weight resin selected from the group consisting of ethylenevinyl acetate copolymers having a vinyl acetate content of about 17 to 42% and a melt index of from about 1.6 to 470 and ethylene-ethyl acrylate copolymers having an ethyl acrylate content of about 1; 5to 25% and a melt index of from about 2.5 to of from 30 to by weight of a hydrocarbon wax selected from the group consisting of paraflin waxes and microcrystalline waxes, of from 5 to 35% by weight of an oily liquid plastic1zer incompatible with said high molecular weight copolymer of said Wax and selected from the group consisting of castor oil, tricresyl phosphate and esters of phthalic acid and aliphatic alcohols containing up to 8 carbon atoms, and v of at least 5% by weight of a pigment.

2. The coating as set forth in claim 1 wherein said esters of phthalic acid and aliphatic alcohols includes dibutyl and dioctyl phthalate.

3. The transfer coating as set forth in claim 1' wherein said mixture includes from 1 to 14% of said high molecular weight resin.

4. The transfer coating as set forth in claim 3 wherein said mixture includes from 15 to 30% of plasticizer.

5. An improved transfer coating composition for effecting selective image transfer to an abutting receiving surface in response to application of impact force to a carrier sheet coated therewith, comprising a mixture of not greater than 6% by weight of a high molecular weight resin selected from the group consisting of ethylene-vinyl acetate copolymers having a vinyl acetate content of about 17 to 42% and a melt index of from about 1.6 to 470 and ethylene-ethyl acrylate copolymers having an ethyl acrylate content of about 15 to 25% and a melt index of from about 2.5 to 18.5,

from 10 to 35% by weight of an oily liquid plasticizer component incompatible with said high molecular weight copolymer selected from the group consisting of castor oil, tricresyl phosphate and esters of phthalic acid and aliphatic alcohols containing up to 8 carbon atoms,

of at least by weight of a pigment, and the balance of hydrocarbon wax selected from the group consisting of parafiin waxes and microcrystalline waxes.

6. In a transfer film, a homogeneous sheet of material containing a resin selected from the group consisting of ethylene-vinyl acetate copolymers having a vinyl acetate content of about 17 to 42% and a melt index of from about 1.6 to 470 and ethylene-ethyl acrylate copolymers having an ethyl acrylate content of about 15 to 25% and a melt index of from about 2.5 to 18.5, hydrocarbon waxes and an oily liquid incompatible with said copolymer resins and selected from the group consisting of castor oil and tricresyl phosphate and pigment wherein the respective percentages by Weight thereof are 8 percent; 72 percent; 10 percent; and 10 percent.

7. In a transfer film, a homogeneous sheet of material containing a resin selected from the group consisting of ethylene-vinyl acetate copolymers having a vinyl acetate content of about 17 to 42% and a melt index of from about 1.6 to 470 and ethylene-ethyl acrylate copolymers having an ethyl acrylate content of about to 25 and a melt index of from about 2.5 to 18.5, hydrocarbon waxes and an oily liquid incompatible with said copolymer resins and selected from the group consisting of castor oil and tricresyl phosphate and pigment wherein the respective percentages by weight thereof are 6 percent; 54 percent: percent; and 20 percent.

8. In a transfer film, a homogeneous sheet of material containing a resin selected from the group consisting of ethylene-vinyl acetate copolymers having a vinyl acetate content of about 17 to 42% and a melt index of from about 1.6 to 470 and ethylene-ethyl arcylate copolymers having an ethyl arcylate content of about 15 to and a melt index of from about 2.5 to 18.5, hydrocarbon waxes and an oily liquid incompatible with said copolymer and selected from the group consisting of castor oil and tricresyl phosphate and pigments wherein the respective percentages by weight thereof are 6 percent; 64 percent; 20 percent; and 10 percent.

9. In a transfer film, a homogeneous sheet of material containing a resin selected from the group consisting of ethylene-vinyl acetate copolymers having a vinyl acetate content of about 17 to 42% and a melt index of from about 1.6 to 470 and ethylene-ethyl acrylate copolymers having an ethyl acrylate content of about 15 to 25 and a melt index of from about 2.5 to 18.5, a hard microcrystalline wax, castor oil, and a pigment, each present by weight in the proportions of 8 percent, 72 percent, 10 percent, and 10 percent, respectively.

10. In a transfer film, a homogeneous sheet of material containing a resin selected from the group consisting of ethylene-vinyl acetate copolymers having a vinyl acetate content of about 17 to 42% and a melt index of from about 1.6 to 470 and ethylene-ethyl acrylate copolymers having an ethyl acrylate content of about 15 to 25% and a melt index of from about 2.5 to 18.5, a soft microcrystalline wax, castor oil, and a pigment, each present by weight in the proportions of 6 percent, 64 percent, 20

percent, and 10 percent, respectively.

11. In a transfer film, a homogeneous sheet of material containing a resin selected from the group consisting of ethylene-vinyl acetate copolymers having a vinyl acetate content of about 17 to 42% and a melt index of from about 1.6 to 470 and ethylene-ethyl acrylate copolymers having an ethyl acrylate content of about 15 to 25% and a melt index of from about 2.5 to 18.5, a hard wax, a soft wax, an oily liquid selected from the group consisting of castor oil and tricresyl phosphate and a pigment, each being present by weight in the percentages of 6 percent, percent, 24 percent, 20 percent and 20 percent.

12. In a transfer film, a homogeneous sheet of material containing a resin selected from the group consisting of ethylene-vinyl acetate copolymers having a vinyl acetate content of about 17 to 42% and a melt index of from about 1.6 to 470 and ethylene-ethyl acrylate copolymers having an ethyl acrylate content of about 15 to 25 and a melt index of from about 2.5 to 18.5, a hard wax, a soft wax, an oily liquid selected from the group consisting of castor oil and tricresyl phosphate and a pigment, each being present by weight in the percentages of 6 percent, 30 percent, 24 percent, 20 percent and 20 percent, and a carrier sheet superimposed on one surface of said sheet of material.

13. The transfer medium as set forth in claim 1 having a carrier sheet superimposed on one surface thereof.

14. An improved transfer coating composition for effecting selective image transfer to an abutting receiving surface in response to applications of impact force to a carrier sheet coated therewith, comprising a mixture of from 4 to 14% by weight of a high molecular weight resin selected from the group consisting of ethylenevinyl acetate copolymers having a vinyl acetate content of about 17 to 42% and a melt index of from about 1.6 to 470 and ethylene-ethyl acrylate copolymers having an ethyl acrylate content of about 15 to 25% and a melt index of from about 2.5 to 18.5,

of from 30 to 75% by weight of a hydrocarbon wax selected from the group consisting of paraifin waxes and microcrystalline waxes,

of from 10 to 20% by weight of an oily liquid plasticizer incompatible with said high molecular weight copolymer and selected from the group consisting of castor oil, tricresyl phosphate and esters of phthalic acid and aliphatic alcohols containing up to 7 carbon atoms, and

of at least 5% by weight of a pigment.

r 15. An improved transfer coating composition for effecting selective image transfer to an abutting receiving surface in response to application of impact force to a carrier sheet coated therewith, comprising a mixture of not greater than 20% by weight of a high molecular weight resin selected from the group consisting of ethylene-vinyl acetate copolymers having a vinyl acetate content of about 17 to 42% and a melt index of from about 1.6 to 470 and ethylene-ethyl acrylate copolymers having an ethyl acrylate content of about 15 to 25% and a melt index of from about 2.5 to

18.5, of from 30 to 75 by weight of a hydrocarbon wax selected from the group consisting of parafiin waxes and microcrystalline waxes, of from 5 to 35% by weight of castor oil, and of at least 5% by weight of a pigment. 16. An improved transfer coating composition for effecting selective image transfer to an abutting receiving surface in response to applications of impact force to a 7 5 carrier sheet coated therewith, comprising a mixture of from 4 to 14% by weight of a high molecular weight resin selected from the group consisting of ethylenevinyl acetate copolymers having a vinyl acetate content of about 17 to 42% and a melt index of from about 1.6 to 470 and ethylene-ethyl acrylate copolymers having an ethyl acrylate content of about 15 to 25% and a melt index of from about 2.5 to 18.5,

of from 30 to 75% by weight of a hydrocarbon wax selected from the group consisting of paraflin Waxes and microcrystalline Waxes,

of from 10' to 20% by weight of castor oil, and of at least 5% by weight of a pigment.

References Cited UNITED STATES PATENTS 2,810,661 10/1957 Newman et a1 117-36.1 5 3,010,899 11/1961 Boyer 26033.6 3,061,454 10/ 1962 Graf et a1 260-23 3,177,086 4/ 1965 Newman et a1. 1*1736.1 3,207,716 9/1965 Lippoldt 260-23 3,308,086 3/1967 Wartrnan 26030.6

1O DONALD E. CZAJA, Primary Examiner.

LEON I. BERCOVIT Z, Examiner.

R. WHITE, Asistam Examiner.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,368,989 February 13, 1968 Robert R.' Wissinger et a1.

It is certified that error appears in the above identified patent and that said Letters Patent are hereby corrected as shown below:

Column 6, line 32, "lasticizer" should read plasticizer line 64, "of" should read and Column 7, lines 52 and 53, "arcy1ate, each occurrence, should'read acrylate Signed and sealed this 10th day of March 1970.

(SEAL) Attest:

Edward M. Fletcher, Jr.

Attesting Officer Commissioner of Patents WILLIAM E. SCHUYLER, JR.

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