US3413184A - Transfer medium and method for making same - Google Patents

Description

Nov. 26, 1968 FlNDLAY ET AL 3,413,184

TRANSFER MEDIUM AND METHOD FOR MAKING SAME Filed March 9, 1966 FIGZ FIGS

m N T A N W EMR WM IH w E WM UE HK Y ATTORNEY! United States Patent 3,413,184 TRANSFER MEDIUM AND METHOD FOR MAKING SAME Hugh T. Findlay and Kenneth H. Froman, Lexington, Ky.,

assignors to International Business Machines Corporation, Armonk, N.Y., a corporation of New York Continuation-impart of application Ser. No. 171,188, Feb. 5, 1962. This application Mar. 9, 1966, Ser. No. 536,557

18 Claims. (Cl. 161160) ABSTRACT OF THE DISCLOSURE Transfer elements comprising a polymer film having a plurality of pores, a horizontal zone near One surface of the film having a significant relatively high density of pores, a second horizontal zone near the opposite surface of the film having a significant realtively low density of pores, and globules of fluid transfer ink in the pores, the ink being expressible from the pores in response to pressure applied to the film. A particulate filler material present in an amount of at least by weight improves the properties of the film. A process for producing transfer elements as described comprising mixing a fluid transfer ink with a solution of a film-forming polymer in a solvent for the polymer, the ink being relatively insoluble in the solvent, depositing a coating of the resulting dispersion onto a substrate, heating to evaporate the solvent so that as it migrates towards the surface of the coating away from the substrate it carries dissolved plastic towards the surface and produces a relatively high concentration of plastic near that surface and a relatively higher concentration of ink near the other surface of the film and then stripping the film from the substrate.

The present invention relates broadly to novel transfer media useful as carbon papers, typewriter ribbons or the like. More specifically, the present invention is directed to a reusable plastic transfer element and methods for making such transfer elements. This is a continuation-inpart application of US. application Ser. No. 171,188 filed Feb. 5, 1962, now abandoned.

Transfer media or elements now in common usage may be generally classified in the following broad categories: ink impregnated woven fabrics, single-use carbon paper and carbon film materials and supported, reusable porous plastic laminates. Each of the foregoing types of transfer materials is attended by certain important disadvantages. Due to the caliper of the fabric, the impregnated woven fabric ribbons are characterized by lack of conformity of the fabric to the type face under impact and this results in a low-quality transfer. In addition, the fabric weave is apparent in the transferred material and results in reduced sharpness of characters.

Conventional single-use carbon paper and film ribbons have relatively high-quality transfer characteristics, but, due to their extremely thin caliper and structure, must be disposed of after single use. High cost is, therefore, a serious drawback in the use of such transfer materials.

Many reusable ribbons comprising a lamina of porous plastic capable of expressing ink under impact are more economical than the single-use carbon papers and films, but produce poor quality image transfer, due to high caliper and lack of conformity to the type face.

Furthermore, in all prior materials there is a generally uniform distribution of transfer ink throughout the transfer layer. Thus, after the ink has been exhausted from the surface in contact with the transfer receiving sheet there is a drop in the sharpness and depth of color of the images produced.

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It has also been a recurring problem in the prior art to control the expression of ink from a transfer medium under type impact so that the ink is primarily delivered to the transfer-receiving sheet, rather than to the type element. In the case of woven fabrics, various sizing solutions have been applied to the type side of the ribbon to achieve this purpose. In the case of the single-use carbon papers and films and the supported, reusable plastic transfer materials, a solid supporting member, usually paper, overcomes this problem.

Accordingly, the present invention has for its object the production of transfer materials of thin caliper characterized by excellent conformity to type face under impact.

A further object of the present invention is to provide reusable plastic transfer elements which show good impact resistance and handling tensile at low caliper.

An additional object of the present invention is to provide reusable plastic transfer elements which give excellent quality transfer without image distortion due to lack of conformity to type face or undesirable fabric weave impression.

A further important object of the present invention, therefore, is to provide a transfer material from which ink may be expressed under pressure with substantially no expression of ink from the surface of the material receiving the type impact.

Another aspect of the foregoing object of the invention is the provision of transfer elements having a high concentration of transfer medium near the surface of the element in contact with the receiving sheet.

In general, the present invention comprises a solid, cast, porous film of a thermoplastic or thermosetting material having dispersed in its pores globules of ink, expressible under the pressure of a type face, writing instrument, or the like.

The invention will be better understood in the light of the following description and claims and the accompanying drawing which illustrates, by way of example, a preferred mode for carrying out the present invention and the best means which has been contemplated for disclosing the principle of the invention.

In the drawing:

FIGURE 1 is a somewhat schematic side elevational view of a system or apparatus for carrying out the present invention; and

FIGURES 2, 3 and 4 are edge views of transfer elements manufactured according to the present invention.

In general, the products of the present invention comprise a solid, continuous porous matrix containing in the pores globules of a liquid or gelled ink. The products usually contain from 10%to by weight of the plastic matrix and from 10% to 90% by weight of dispersed ink.

A filler, usually in the form of a powder or fibers, may also be added to the formula to clean, harden, strengthen and extend the polymer. Up to 70% by weight of such a material may be added. For example, one or more of the following materials may suitably be incorporated in the formulation for this purpose: diatomaceous earth, glass fiber, graphite, talc, boehmite alumina, silica powder and synthetic fibers.

The use of a filler is greatly preferred, as evidenced by the presence of at least about 10% by weight filler in each of the following embodiments. The filler lends stiffness and body to the final product. This gives a physical firmness to the product which is generally a necessary characteristic for mechanical or easy handling of the product. Thus, when the product is a typewriter ribbon, yield and longitudinal stretching are reduced by the filler whereas without the filler existing ribbon feed mechanisms of typewriters are ineffective. Also, most typewriters move the ribbon vertically during each print stroke.

Without the filler, the ribbon folds away and is therefore not brought to the printing point. It also appears that the filler plays an important part in metering ink from the product during normal use. Some of the filler is believed to occupy the pores of the product and to act as a multitude of tiny wicks. This prevents ink from splattering to the print receiving surface at points other than the points of the direct impact of the raised salient of an impacting type die. Although the mechanism is not well understood, when the filler is in the product, print coverage is more uniform and complete; print opacity is improved by the fact that greater amounts of pigment are expressed. The filler enables the product to utilize more efficiently the ink originally contained in it and to thereby provide more overstrikes and reuse. The filler also roughens the surface of the product slightly, and this reduces a tendency to cling to the parts of the ribbon feed mechanisms of the typewriter.

Suitable synthetic polymers for use as the continuous porous matrix include the following: nylon, polyurethane, polycarbonates, polyethylene, polypropylene, polyvinyl alcohol, epoxy resins, cellulose acetate butyrate and cellulose acetate. Other synthetic resins or mixtures of synthetic and natural resins capable of forming thin, selfsupporting porous matrices may be substituted for the foregoing without departing from the scope of the invention.

The proper understandings must be exercised in selecting the synthetic polymer for production of the best typewriter ribbon. It is preferable, of course, that a typewriter ribbon be as thin as possible. However, thin transfer mediums in accordance with this invention may be cut or severed by impact from a type die during normal typing. Proper selection of the synthetic polymer, however, can overcome this. The polymer should have sufficient internal strength to resist the cutting action of a type die. The nylon, where used in the following embodiments, is entirely effective in resisting being chopped apart or otherwise significantly injured under the direct impact of a type die.

The exact composition of the ink incorporated in the pores of the polymeric matrix is not critical and may be in the form of either a fluid ink or a gelled ink. One requirement of the ink is that it not be soluble in the polymeric matrix. Rather, the ink should be insoluble in the plastic or plastic solution so that it tends to separate and to form small, discrete globules of ink within the plastic.

In general, the method of the present invention comprises dissolving a portion of the polymer in a volatile solvent and then dispersing the insoluble ink in the polymer solution. This solution is then coated on a temporary, heat stable substrate, such as a paper web or an endless belt of Mylar or stainless steel.

As an important feature of the invention, greater ink concentration is provided on one surface of the transfer element by heating the coating to evaporate tlre solvent. As the solvent evaporates it naturally migrates towards the upper surface and the temporary substrate effectively blocks vaporization through the bottom surface. The migrating solvent carries dissolved plastic with it, so that a relatively high concentration of plastic is obtained at the upper surface and a higher concentration of ink is obtained at the lower surface.

After the solvent has been evaporated, the transfer element may be stripped from the substrate and cut into desired shapes. The side of the element having a high ink concentration is the one which is placed against a sheet of paper when used in any writing operation.

If greater strength along with additional sealing against the escape of ink from the upper surface is desired, a solvent solution of plastic may be sprayed or coated on the upper surface of the element before it is stripped from the substrate. Heat is again applied to evaporate the solvent and produce a plastic layer which is integral with the plastic forming the element.

Similar results may be obtained if, instead of coating the element with a solvent solution of plastic, there is applied to the top surface a backing strip of a plastic material. When a backing strip is applied, a high proportion of liquid or gelled ink is added to the formulation in order to obain a tacky upper surface to which the backing strip will adhere.

The present invention will be better understood in the light of the following detailed examples:

Example I A transfer element in accordance with the present invention comprising approximately four parts by weight of nylon, three parts by weight of finely divided filler, and five parts by weight of liquid ink is prepared in the following manner:

(1) One part by weight of nylon is dissolved in sufficient ethyl alcohol to produce a solution containing 12% nylon and 88% ethyl alcohol. The solution is obtained by mixing the nylon and ethyl alcohol in a Cowles dissolver at a temperature of 140 F. Stirring expedites the solution.

(2) The following ink ingredients are weighed into a steel ball mill and are milled for approximately eight hours:

Pigments: Percent by weight Carbon black 2 Toning black 2451L black pigment 8 Toning black 2171 black pigment 5 Black pigment 1686 inorganic pigrnent 8 Total pigments 23 Dyestuffs:

Methyl Violet B base oil-soluble dyestuff 2 Nigrosine base N oil-soluble black dyestulf 16 Total dyestuffs 18 Dye solvent:

Polyethylene glycol 400 dilaurate 15 Total dye solvent 15 Vehicle:

Oleic acid 44- Total vehicle 44 Total (3) Three parts by Weight of diatomaceous earth is mixed with the nylon-ethyl alcohol solution until the admixture is homogeneous.

(4) The ink is prepared in Step 2 is then slowly added to the mixture of fill-er and the nylon-ethyl alcohol solution prepared in Step 3 under high speed agitation in a Cowles dissolver, until complete dispersion of the ink and filler in the nylon solution is obtained.

(5) The remaining three parts of nylon is dissolved separately in a three-to-one mixture of ethyl alcohol and water by stirring in a Cowles dissolver at F., to produce a solution of 5% nylon and 95% ethyl alcohol and water.

Referring now to FIGURE 1 of the drawing, a mixture of the ink and filler dispersed in the nylon-ethyl alcohol solution (Step 4) is charged into supply tank 10 which includes agitating means 11 to maintain the ink and filler in a dispersed condition. The mixture is admitted by valve 21 through conduit 20 into a roll coater basin 30. Roller 31 of the reversed roll coating applicator is rotated counter-clockwise, dipping beneath the level of the mixture 40 in basin 30. Metering roller 32 controls the amount of mixture adhering to the surface of coating roller 31.

A temporary Mylar substrate 50 is unwound from substrate supply reel 51 and is passed between backup roller 52 and contact roller 31, whereupon a thin film of the mixture, approximately 2 /z-3 mils in thickness when first aplied, is transferred to the surface of the substrate 50. The substrate, carrying the cast film, is then passed through oven 60 over guide rollers 61. Heating lamps 62 positioned in the oven provide a temperature of approximately 180 F., at which ethyl alcohol migrates to the upper surface of the cast film causing an increase in the concentration of nylon at the top surface and of ink at the bottom surface of the film.

The film, about one mil in thickness after drying, is then sprayed with the five percent solution of nylon from Step 5.

Air is circulated into oven 60 through conduit 70, along the surface of the cast film, and out through conduit 80 to carry off volatized solvents.

The solution of Step 5 is introduced through conduit 90 and spray head 91 onto the top surface of the cast film during the progress of the Mylar web through the oven. Solvent is also evaporated from the sprayed film leaving an integral, solvent-bonded nylon film on the top surface of the element.

The cast film and substrate are then withdrawn from the oven and the temporary Mylar substrate is peeled from the cast transfer element by knife 92, the substrate being wound on reel 93 and the cast film of transfer material 100 on reel 94.

The transfer element 100 thus produced, and illustrated in FIG. 2, comprises a porous plastic matrix 100 having globules dispersed non-uniformly within the pores. The ink globules 101 are dispersed so as to form a zone or strata 102 of relatively high concentration near the surface which will be in contact with an image receiving sheet and a zone 103 of relatively low ink concentration on the pressure receiving surface. An integral nylon film 104 seals the upper surface of the element to limit ink expression from that side.

The nylon is well suited to resist cutting under the direct impact of a type die. Therefore, a very desirable product of this Example I is obtained by trimming, cutting, or otherwise severing as required to obtain a relatively narrow width usuable for a typewriter ribbon and then winding into a spool or otherwise compacting the transfer medium. The final product is a typewriter ribbon, which is generally in a spool of the external configuration and appearance of a conventional typewriter ribbon.

Example II A transfer element comprising three parts by weight of nylon, two parts finely divided filler and four parts liquid ink is prepared in the following manner:

(1) Three parts nylon is dissolved in suflicient ethyl alcohol to produce a solution containing 12% nylon and 88% ethyl alcohol.

(2) Two parts by weight of talc are homogeneously mixed with the solution of Step 1.

(3) Four parts of liquid ink, of the same formulation as prepared for use in Example I, is then slowly added to the mixture of Step 2 under high speed agitation to produce a thorough dispersion of the ink.

(4) The dispersion of Step 3 is then cast as a film about 3 mils thick on the surface of a continuously moving, temporary paper substrate, after the method of Example I.

(5) The cast film is then dried in an oven at a temperature of 180 F. for two minutes, is stripped from the paper substrate and is cut to size for use as a typewriter ribbon.

FIGURE 3 illustrates an enlarged, schematic edge view of the ribbon prepared according to Example II. The porous plastic matrix 100 containing ink globules 101 is also segregated into zones 102 and 103 of high and low ink concentration respectively. No integral sealing film of plastic is present in this embodiment. The nylon has good internal strength. This product is therefore well suited to be made into a typewriter ribbon in the manner described in connection with Example I.

Example HI A transfer element was prepared in accordance with the method described in connection with Example I and comprising two parts by weight polyethylene, .5 part by weight silica powder and 2 parts by weight of a liquid ink prepared as described in connection with Example 1.

Example IV A transfer medium was prepared in accordance with the method described in connection with Example I comprising eight parts by weight polypropylene, five parts by weight talc and ten parts by weight of a gelled ink. The gelled ink is prepared in the same manner as the liquid ink employed in Example I except that bentonite, a montomorillonite derivative, is dispersed in the ink and the ink is then passed through a roller mill at a pressure of 200 pounds per square inch and again at a pressure of pounds per square inch to gel the ink. The gelled ink is then mixed and dispersed in the same manner as the liquid ink is dispersed in the polymer solution as described in connection with Example 1.

Example V A transfer medium was prepared as in Example IV eX- cept that polyethylene was substituted for polypropylene to provide the matrix of the product.

Example VI A transfer element is prepared comprising five parts by weight nylon, three parts by weight diatomaceous earth and twelve parts liquid ink as follows:

(1) Five parts nylon is added to 'sufiicient ethyl alcohol to form a solution containing 12% nylon and 88% ethyl alcohol.

(2) Three parts diatomaceous earth is mixed with the nylon solution of Step 1.

(3) Twelve parts of liquid ink of the same formula as used in Example I is slowly added to the mixture of Step 2 under high speed agitation until complete dispersion is obtained.

(4) The dispersion of Step 3 is then cast on a Mylar substrate, is heated at 180 F. for about 2 minutes, and is stripped from the Mylar base. Due to the relatively high proportion of ink in the formulation the top surface of the cast film is tacky.

(5) A sheet of polyethylene, about 1 mil in thickness, is then pressed against the tacky surface to produce a transfer element.

FIGURE 4 of the drawing is an enlarged, schematic,

side view of a supported transfer element of the type prepared in accordance with Example VI. The element comprises a support 105 bonded to the top or low ink concentration surface of porous plastic matrix 100.

Plastic backing materials other than polyethylene may be substituted in Step 5 of the foregoing example with comparable results.

As already noted above, various materials may be substituted for the polymer and the liquid or gelled ink. Likewise, various fillers may be used without departing from the spirit of the present invention.

Especially in connection with the ink, all commercially available ink pigments can be interchanged with those set forth in the examples. By the same token, other oil soluble dyestuffs may be employed. Such substitutions may require slight adjustment of the ratio of ink to plastic and filler, but these adjustments will still be in the approximate ranges set forth in the description.

Heating in oven 60 may be accomplished by radiant heat lamps as shown in the drawing, or by passing a preheated current of air through the oven, or by other suitable means. The temperature selected will depend on the volatility of the solvents employed.

While there have been shown and described and pointed out the fundamental novel features of the invention as applied to the preferred embodiment, it will be understood that various omissions and substitutions and changes in the form and details of the device illustrated and in its operation may be made by those skilled in the art without departing from the spirit of the invention. It is the intention, therefore, to be limited only as indicated by the scope of the following claims.

What is claimed is:

1. The method for producing a transfer element comprising:

mixing a fluid transfer ink and substantial amounts of a particulate filler material with a solution consisting of a film forming polymer and a solvent for said polymer to form a substantially homogeneous dispersion of said ink in said solution, said ink being present in an amount sufiicient to occupy a substantial volume of the residue of said dispersion after drying said polymer, said volume of ink being such that the dried residue of said dispersion, after evaporation of said solvent, may be used as a transfer medium by the expression of said ink in response to pressure, and said polymer being soluble in said solvent and said ink being relatively insoluble in said solvent,

depositing a coating of said dispersion on a substrate which is substantially impermeable to vapors of said solvent thereby blocking the evaporation of said solvent in the direction of said substrate,

heating to evaporate said solvent from said coating whereby as the solvent evaporates it migrates towards the surface of said coating which is away from said substrate and carries dissolved plastic towards said surface so that a relatively high concentration of plastic is obtained at said surface and a higher concentration of ink is obtained at the surface adjacent said substrate, to form a porous polymer film in the pores of which said ink is distributed in an amount suflicient so that it is expressed under writing pressure on said polymer film and stripping said film containing said ink from said substrate.

2. The process for producing a typewriter ribbon comprising:

mixing a fluid transfer ink with a solution comprising a film forming polymer and a solvent for said polymer, the residue of said solution after evaporation of said solvent having internal strength sufficient to resist the cutting action of the direct impact of a normally impacting type die, to form a substantially homogeneous dispersion of said ink in said solution said ink being present in an amount sufiicient to occupy a substantial volume of the residue of said dispersion after drying, said volume of ink being such that the dried residue of said dispersion, after evaporation of said solvent, may be used as a transfer medium by the expression of said ink in response to pressure, and said polymer being soluble in said solvent and said ink being relatively insoluble in said solvent,

depositing a coating of said dispersion on a substrate,

heating to evaporate said solvent from said coating whereby as the solvent evaporates it migrates towards the surface of said coating which is away from said substrate and carries dissolved plastic towards said surface so that a relatively high con centration of plastic is obtained at said surface and a higher concentration of ink is obtained at the surface adjacent said substrate, to form a porous polymer film in the pores of which said ink is distributed in an amount sufi'icient so that it is expressed under writing pressure on said polymer film, and stripping said film containing said ink from said substrate.

3. The method of claim 2 wherein said film is slit into the form of a ribbon having the dimensions desired for use as a typewriter ribbon.

4. The method of claim 3 further comprising winding said ribbon into a spool for use as a typewriter ribbon.

5. The method of the above claim 2 further comprising substantially uniformly distributing in said dispersion up to 70% by weight of the film of a particulate filier material.

6. The method as in claim 2 further comprising coating a second solution comprising a film forming polymer, the residue of said second solution having sufiicient internal strength to resist the cutting action of the direct impact of a normally impacting type die, onto one surface of said film, and evaporating the solvent from said second solution to form a thin layer of polymer integral with the polymer of said film.

7. The method as in claim 5 further comprising coating a second solution comprising a film forming polymer, the residue of said second solution having sufiicient internal strength to resist the cutting action of the direct impact of a normally impacting type die, onto one surface of said film, and evaporating the solvent from said second solution to form a thin layer of polymer integral with the polymer of said film.

8. A transfer element comprising a polymer film having a plurality of pores, a horizontal zone near one surface of said film having a significant relatively high density of said pores, a second horizontal zone near the opposite surface of said film having a significant relatively low density of said pores, and globules of fluid transfer ink in said pores, said transfer ink being expressible from said pores in response to pressure applied to said film.

9. A transfer element comprising a porous polymer film containing globules of fluid transfer ink in its pores, said ink being substantially insoluble in said polymer, and a particulate filler material distributed throughout said film in an amount of at least 10% by weight of said film to strengthen said film, and said ink comprising such a volume of said film that it is expressible from said pores in response to writing pressure on said film.

10. A transfer element as described in claim 9 further comprising a solid supporting film bonded to one surface of said film.

11. A transfer element comprising a polymer film having a plurality of pores, a horizontal zone near one surface of said film having a significant relatively high density of said pores, a second horizontal zone near the opposite surface of said film having a significant relatively low density of said pores, globules of fluid transfer ink in said pores, said ink comprising such a volume of said film that it is expressible from said pores in response to writing pressure on said film and a particulate filler material distributed throughout said film in an amount sufiicient to strengthen said film.

12. A transfer element as described in claim 11 wherein, exclusive of said filler material, said film is comprised of from 10% to of polymer and from 10% to 90% of ink.

13. A- transfer element as described in claim 11 further comprising a sealing film of polymer bonded to a surface of said film.

14. The transfer element as described in claim 13 wherein the surface to which said sealing film of polymer is bonded is said opposite surface of said film adjacent the second horizontal zone having a significant relatively low density of said pores.

15. The transfer element as described in claim 11 in which said polymer is nylon.

16. The transfer element as described in claim 14 where both said polymers are nylon.

17. The transfer element of claim 8 wherein said film is in the form of a typewriter ribbon.

18. The method of producing a transfer element comprising:

9 10 mixing a fluid transfer ink with a solution consisting writing pressure on said polymer film, and stripping of nylon, as the film forming polymer, and ethyl said film containing said ink from said substrate. alcohol as the solvent for said polymer, to form a substantially homogeneous dispersion of said ink in References Cited said solution, said ink being present in an amount 5 UNITED STATES PATENTS sufiicient to occupy a substantial volume of the residue of said dispersion after drying, said v lume 2 g 117 l 92 X of ink being such that the dried residue of said dis- 2777824 3 L atzer et a1 26 216 persion, after evaporation of said solvent, may be 7 eeds 117*361 2,872,340 2/1959 Newman et a1 ll736.1 used as a transfer medium by the expression of sa1d ink in response to Pressure, 10 2,893,890 7/1959 Harvey 117-361 depositing a coating at said dispersion on a substrate 7/1960 Clark X to a thickness of from 2 to 3 mils, heating said coat- 3 513:? et a1 b mg 1n contact with sa1d su strate at approximately 3,194,676 7/1965 Kmmbein et all u" 117 36.1

180 F. for approximately 2 minutes to evaporate 15 said solvent from said coating to form a porous polymer film in the pores of which said ink is distributed EARL BERGERT Exammer' in an amount sufiicient so that it is expressed under M. L. KATZ, Assistant Examiner.

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