US3375125A - Method of making transfer sheet and resultant article - Google Patents

Description

March 26, 1968 sHENlAN 3,375,125

METHOD OF MAKING TRANSFER, SHEET AND HESUL'IANT ARTICLE Filed Oct. 14, 1963 SINGLE UNIFIED TRANSFER LAYER Inventor POPKIN SHENIAN By KM 1.

United States Patent 3,375,125 METHOD OF MAKING TRANSFER SHEET AND RESULTANT ARTICLE Popltin Shenian, Pittsfield, Mass., 'assignor to General Electric Company, a corporation of New York Filed Oct. 14, 1963, Ser. No. 316,001 4 Claims. (Cl. 117-364) This invention relates to transfer writing and particularly to the transfer placement of marks and indicia by means of printing or writing pressure or a type blow, acting through a pressure sensitive transfer sheet of the carbon paper type.

Transfer sheets of the carbon paper type have, of course, been known and used for many years. Lately, however, the transfer placement of various types of record marks on the receiving surfaces of copy sheets or cards to be handled and sensed by data processing equipment has become a matter of increasing interest. The use of the carbon paper or typewriter ribbon type pressure sensitive marking media for placing spots of the required properties has been suggested. For data processing the use of a pressure sensitive product designed for a single pass through a character transfer apparatusis preferred. Such products have come into commercial use in connection with the use of electric typewriters and the like.

It has been found, however, that most of the prior pressure transfer layers were lacking in certain respects when an attempt was made to adapt them to data processing use. While the marks made are of adequately permanent nature considered in the sense of ordinary carbon copy use and will remain sufficiently legible under most conditions, there is an undesirable tendency for the pressure deposited marks to smudge and spread if the marked sheet is handled a great deal, or used with the ordinary sheet or card feeding and handling equipment encountered in data processing machinery.

Also, in conventional practices, it is difficult to control the release of smudge from a transfer sheet in the transfer process due to the low contact pressure at which material is released from a transfer sheet. When this smudging occurs, the reliability with which the true mark can be automatically sensed is severely impaired, even though the impairment is sometimes comparatively slight by visual standards, and false indications are picked up due to contact of the coated surface of the transfer sheet with the record caused by handling during the transfer process.

One means for overcoming these defects is that proposed in US. Patent 3,017,297. This is done by con structing the transfer sheet with a coating having at least two distinct layers or strata, simultaneously transferable from the carrier sheet in a substantially stenciling fashion. In this mode of construction both the bottom stratum or layer nearest the carrier sheet and the top layer have smudge-resistant properties. These properties of smudgeresistance are due to the absence from the top layer of material to which the sensing device will react, so that even though the top layer is partially displaced by handling, the displaced portion will not affect the sensing means. These properties may also be due to the character of the bottom layer, as where the bottom layer is relatively hard and of low adhesiveness so that, even though charged with a type of material to which the sensing device in question will react, it is not subject to ready displacement from a spot to which it has been applied.

The use of pressure sensitive character transfer sheets or ribbons in which the sensible material is present in a separate layer sandwiched between a base stratum and a protective over-layer, while useful in overcoming some of the limitations of earlier character transfer sheets, also imposes certain restrictions on the potential use of the sheet due to the presence of the protective over-layer.

One of the problems which attends the use of character transfer sheets having protective over-layers is that they require the use of a relatively higher striking force to effect a transfer of a well-defined firmly deposited character. This problem arises because the transfer of the character is accomplished only when the material from the inner layer of the ribbon is transferred to the receiving surface. The transfer accordingly requires sufficient striking energy to first transfer the material from the protective over-layer to the receiving surface and to then imprint also the inner layer which alone contains the ingredient to which data processing machines will respond.

One of the objects of the present invention is to provide a character transfer sheet which is more responsive to different levels of applied transfer force, and which is particularly responsive to lower levels of striking force in forming transfer characters having the other combination of advantages pointed out more fully hereinafter.

Another object is to provide a sheet from which the release of the sensable material may be controlled more readily.

Another object is to provide a character transfer sheet from which characters may be transferred with an extremely well-defined edge.

Still another object of the invention is to provide a single surface layer from which characters may be transferred responsive to applied localized pressure but which layer 'is also smudge resistant and abrasion resistant.

Afurther object is to provide a character transfer sheet from which characters may be transferred in distinct intensities responsive to the application of distinct levels of transfer inducing pressure.

, Still another object is to provide transferred characters which are both smudge resistant and abrasion resistant where these characters have been transferred from a pressure sensitive transfer sheet.

Other objects and advantages of the present invention will be in part apparent and in 'part pointed out from the description which follows.

In one of its broader aspects the objects of the present invention may be achieved by depositing on a carrier substrate sheet, two distinct layers of film forming materials, and blending of these distinctly deposited layers into a single layer under the influence of a drying heat.

The features of the present invention and the manner in which it is carried out will be understood with greater clarity by reference to the accompanying drawing in which FIGURE 1 is a schematic fragmentary sectional viewof a transfer sheet formed in accordance with the present invention.

v The following examples illustrate the manner in which the article of the present invention is formed and used. It will be understood, however, that these examples are given primarily for illustrative purposes and are not to be interpreted as limiting or defining the scope of the invention. I

Example 1 isoprene hydrochloride. One such sheet is available from the Goodyear Rubber Company as a tensilized Pliofilm bearing a number 40N-1.

In forming a transfer sheet, a specimen of the isoprene hydrochloride carrier film is first smoothed onto a glass plate whose surface temperature is maintained at about 40 C. On this carrier film a basic sub-coat is first formed and a basic top coat is applied over the subecoat in the manner to produce a single unified pressure sensitive character transfer coating.

The basic sub-coat is formed on the carrier film as follows: A basic sub-coat dispersion is first prepared by ball milling or grinding the following ingredients:

Ingredient Parts by Function Specific Material Weight of Ingredient Sensing Materialflu Ferrosmferric Black Oxide (IRN-IOO, 50

C. K. Williams 00.). Binder Ethyl Cellulose, 10 cps. standard 8 ethoxy (Dow Chemical 00.). Plasticizer Nevlac Hard (Neville Chem. Co.) {4 (Mineral Oil). 6 Wetting Agent,. Ten Lo 70 oil soluble non-ionic 1 surfactant (Nopco Chem. 00.). $olvent Methyl Ethyl Ketone 125 The ball milling or grinding used must be sufiicient to reduce the size of particulate material to a size of the order of 10 microns or less on Hegman gauge.

The sub-coat dispersion thus prepared is applied to the substrate sheet by an appropriate spreading or film casting device such as a doctor blade or the like to apply a 1 mil wet film of the basic sub-coating lacquer to the heated carrier film. The deposited lacquer is allowed to dry on the carrier film while it is maintained at a temperature of about 40 C.

Soon after the solvent from the basic sub-coating has evaporated, a layer of a basic top-coating lacquer is applied over the sub-coat. This second coating of lacquer is allowed to dry under the influence of the 40 temperature at which the base coat, carrier film and supporting surface are maintained.

The preparation of the top coat lacquer composition is as follows: a

A wax blend is prepared by fusing 50 parts of pure and refined carnauba wax with 50 parts of mineral oil, The wax used in this case is a product of the International Wax Refining Co. The wax blend formed has a melting point of approximately 72 to 79 C. A dispersion is then prepared to contain parts of this vwax blend in 95 parts of ethyl alcohol. This dispersion is subjected to a high efficiency ball milling such as that described above to reduce the size of dispersed particles to a means diameter of microns or less.

A solution is prepared to contain of a synthetic resin ester prepared from rosin in methyl ethyl ketone.

A particular ester which has been found to produce highly satisfactory results is Staybelite Ester 2 a product of the Hercules Powder Company.

Six parts of the ester solution is added to 100 parts of the dispersion of the wax blend in ethyl alcohol prepared as described above. The resulting composition constitutes the material used to deposite a top coating lacquer.

layer on the basic sub-coat described above to form a unitary transfer coating of a transfer sheet article prepared in accordance with the present invention.

The basic top coating lacquer is applied to the basic sub-coat to a wet layer thickness of about 1 mil and is allowed to dry under the influence of the heat received from the mildly heated .substrate. The transfer sheet article formed in this way is then removed from the mildly heated glass surface and allowed to cool to room temperature.

' It has been observed from a cross section prepared from the transfer sheet formed as described in this example that the deposited sub-coating and top-coating lose their identity as separate layers and are effectively mingled and blended into a unitary coating structure 10 on the carrier film 1 2v as illustrated schematically in FIGURE 1.

A portion of the transfer sheet prepared as described above was employed in stenciling characters onto a receiving surface. Clear, sharp images of the characters employed in applying pressure to the reverse side of the carrier film were observed on the receiving paper surface. One distinct advantage of the formed product is that substantially complete transfer can be obtained at very low levels of impact energy of the order of about 75,000 to 100,000 ergs per character.

Example 2 To demonstrate the importance of the co-mingling of the top coat with the sub-coat a product was prepared in which a top coat resided as a separate and distinct stratum on the sub-coat. This product was prepared as follows:

A substrate of 40 mil Pliofilm was smoothly applied to the surface of a glass plate which was maintained at the prevailing ambient temperature of approximately 22 C. To this film a film of the basic sub-coating lacquer composition was applied as described in Example 1 to a wet coating thickness of 1 mil.

After a sufficient interval to allow the deposited subcoat to dry at the ambient temperature a second lacquer coating was applied. The second coating was formed from the basic top coating lacquer, and it was applied in the manner also described in Example 1 with the exception, however, that methyl alcohol was substituted for the ethyl alcohol used in Example 1. The thickness of the wet layer of top coating after application was again 1 mil. During the drying of the top coating a blast of unheated air was directed over the surface of the wet film to accelerate the drying time.

As a result of the use of the unheated casting plate in this example, in addition to the substitution of the lower boiling solvent and the use of forced air in aiding the drying, the top coat formed in this example did not penetrate into the sub-coat and was detected as a separate stratum. The sheet product produced in this manner was tacky and had a tendency to be smudgy. It was also observed that the coatings thus deposited on the Pliofilm tended to be somewhat flaky.

The sheet product formed in this example was used in a character transfer stenciling test similar to that described in Example 1. However, it was found that the characters transferred were characterized by much poorer edge definition. Some areas of the characters which should have been formed by a uniform transfer of the coating material were found in fact to contain voids. Also the characters were surrounded by extraneous transferred markings. In general the stencilled characters as well as the product from which they were formed were definitely inferior to those produced using the method of the first example.

Example 3 A procedure substantially similar to that of Example 1 was repeated but in this case the ball milling was less than sufiicient to bring the particle size of the coating compositions to the range of about 10 microns or less. It was observed that the characters transferred from this ribbon were inferior in quality particularly in that the uniformity of coating was inferio particulaly with regard to the tendency toward production of void areas in the transfer characters.

It will be apparent from the foregoing that the present invention provides a uniquely advantageous method for forming an article of improved performance capabilities in responding to pressures exerted over defined areas thereof to impart characters of like area definition to receiving surfaces. The improved performance is attributed to the unified character of the transfer layer formed from two coatings.

The precise manner by which the ingredients of the two layers are rearranged or redistributed in forming the single layer from the deposit of two coatings as described is not fully understood. However the advantages of the comingling of ingredients in a very fine state of subdivision which does take place is readily evident in the distinctly improved results which are obtained as illustrated in the above examples. It will also be apparent, however, that the advantages of the invention may be obtained using individual steps and materials or combinations of such steps and materials other than those specified in Example 1 above. The results obtainable will be more advantageous where the materials and steps chosen for practice of this invention are made to depend on specific uses to be made of the sheet article formed.

For example, with regard first to the sensable component of the coating, i.e., the component of the transferred material which is sensed by the data processing apparatus, this may be selected depending on the type of detection to be used. Where iron oxide is employed as the sensable component the sensing device will be magnetic. Correspondingly Where light reflecting or absorbing media, such as carbon black, is the sensable component, the sensing device will depend on visual or optical phenomena. Electro conducting sensable material such as aluminum powder may be incorporated in the layer and used in connection with electric detection apparatus. Also luminescent material such as zinc sulphide may alternatively be used in the transferable coating where optical detection is used. Further, the material may be radioactive, being either a natural or induced radioactive element, the detection relying on detection of emitted sub-atomic particles or short wave length electromagnetic Waves.

The binder material employed in the transferable layer may be almost any thermoplastic or thermosetting resin which has capabilities for forming coatings and which also make available the following coating characteristics:

(A) Releasable adherence to the base film,

(B) A tensile strength to enhance clean fracture, and

(C) Compatibility, that is blendability, with the material of the top coat to be deposited thereon, under the infiuence of the solvent of the top coating composition and mild heating in the order of to 85 C. depending on the thermal and solubility characteristics of the'top coating solvents, and non-volatile components of the top and sub-coatings. The binder material which has given most satisfactory performance in providing the required characteristics is ethyl cellulose having a viscosity of 10 centipoises. However, other materials of similar characteristics may be employed such as cellulose nitrate, cellulose acetate, methyl cellulose, vinyl acetate, vinyl chloride, vinyl acetate copolymers, vinyl alcohol, and polystyrene.

Plasticizers may be employed to modify the properties of a binder material in the manner illustrated in the above examples to make them meet the requirements for a binder particularly pointed out above. In the specific case of ethyl cellulose, a plasticizer consisting of a combination of coumarone-indene type resin with an oil such as mineral oil, castor oil, silicone oil and the like, yields highly satisfactory results. The selection of other plasticizers or combinations of plasticizers to modify binder materials for usein accordance with this invention can be made employing the knowledge available to those familiar with the art of binder materials, and through confirmation with a few tests performed for this purpose using the criteria described herewith and illustrated in the above examples.

A wetting agent is included in the sub-coat composition principally to assist in the milling and dispersing of the sensable component and in wetting the base film to enhance the application of the sub-coat. Numerous wetting agents capable of performing these functions in the formation or application of the sub-coat composition can be selected based on information available in this art particularly when coupled with a few experiments to demonstrate the most suitable of selected materials, as well as the concentration to 'be used for satisfactory wetting depending on the particular ingredients of the composition employed.

The solvent used informing this sub-coat and the solvent concentration should similarly be related to the other ingredients of the composition as well as the mild heating temperature to be used and can be based on the use of the extensive information available in this art.

Turning now to the composition and ingredients of the top coat, there are three components of this top coat composition which are important to the results which are obtained through its use in connection with the present invention. These three are the wax component, the adhesive, and the solvent.

With specific regard first to the wax component, a Wax or wax blend is preferred which displays a balance of dispersibility, attraction for paper, as well as for the ingredients of the coatings, hardness, and the ability to undergo clean fracture. A wax composition which has been found to have a particularly advantageous combinationof these properties is a blend of carnauba wax with mineral oil, parafiin wax and the other ingredients as recited in Example 1 above. However, any of the other vegetable waxes such as ouricury, montan, candelilla and similar waxes may be employed either alone or in combination with oils, parafiin waxes, and like combining materials. The blends prepared to include these combining materials should, however, exhibit the group of required properties as discussed more specifically above. There is an important relationship between the wax component used and the mild heating employed to cause intermingling of the ingredients of the two doposited layers. The temperature used must be below that at which the wax blends fuse, i.e., the finely dispersed wax particles fuse and form a continuum as such fusion impairs the product quality. The quality is impaired particularly in that there is an increased tendency toward formation of transferred characters with voids or more uniform deposit of sensable material.

With more specific regard now to the adhesive ingredient of the top coat composition, the general properties which are required in this component of the top coating composition are the following:

(a) It must be soluble in the solvent system employed. (b) It must be compatible with the binder system in the sub-coat.

(c) It must be -a tackifier for the dispersed wax particles I and paper.

A material which has been found particularly advantageous for use in the combination recited in the Example 1 above is a diethylene glycol ester of hydrogenated rosin which is available from Hercules Powder Company as Staybelite Ester No. 2. However, any of numerous alternate similar synthetic resin esters prepared from rosin may be used in this application where they provide the combination of properties recited a-bove.

Similarly, many other adhesive materials may serve advantageously in carrying out the present invention including such materials as shellacs, low molecular Weight phenol-formaldehyde resins, and other adhesive agents of like properties.

Now more specifically with regard to the solvent employed in the top coating composition, the solvent must exercise a solvent action on the binder system used in the sub-coat sufficient to induce the co-mingling of top coat ingredients into the sub-coat. The solvent action needed is not a complete solution of the sub-coat binder, but for a solvent action to induce the co-mingling of ingredients of the two coatings into a unified coating structure. Most of the common alcohols and ketones such as the ethyl, propyl, isopropyl, and isobutyl alcohol as well as the methyl ethyl ketone and other aliphatic ketones are suitable for this purpose.

The carrier or base film employed in forming the sheet article of the present invention may be any paper metal foil or plastic film which has physical and chemical characteristics compatible with the coating system deposited thereon. In other words, the primary consideration in this article is the nature, content, and form of the transfer coatings. The carrier or base film may be selected or modified to meet the needs of the coatings. Certain characteristics predominate in this selection of base film among which are the following:

The chemical composition of the carrier film must be that adapted to receive and retain the materials deposited thereon and to release them uniformly under the influence of a uniform pressure applied to the uncoated surface of the film and transmitted therethrough. The carrier film should be limited in thickness to permit a full realization of the capability of the deposited transfer layer to deposit characters having sharp, clear edge definition on receiving surfaces. The carrier film must also possess uniform tensile and other physical properties to insure that the concentration of the transfer layer beneath a striking character will be constant and thus able to impart a uniform measure of sensable material :to the receiving surface. The thermal properties of the film must be such that the film will not be adversely affected, as for example undergo dimensional distortion, due to the exposure to a temperature such as that used in the mild heating used to induce formation and co-mingling of the coating layers. Some tensilized films for example may undergo shrinkage due to short exposures to temperatures in the range of to 85 C. and many are subject to shrinkage at temperatures above this range. For example, the tensile strength of the film should be adequate to prevent any significant stretching of the film under use conditions as this would reduce the amount of the sensable component deposited on the receiving surface. A film which has been found to display a highly satisfactory combination of properties for the purposes described above is a 0.4 mil gauge Pliofilm of isoprene hydrochloride which may be obtained from the Goodyear Rubber Co. under the designation N-1 type. Other films which may yield advantageously uniform results are Mylar type polyester, linear polyethylene, polypropylene, and irradiated polyethylene.

Since many embodiments may be made of the articles of the present invention and since many alternative steps may be employed in forming the articles, the foregoing is to be interpreted as illustrative and not as defining or limiting the scope of the invention except as may be necessitated by the statement of the claims which follows.

What is claimed is as follows:

1. The method of forming a coated sheet article suitable for use in transferring characters to a receiving surface responsive to the application of pressure to the reverse side thereof which comprises the steps of:

(1) Disposing a coating on a polymeric base sheet, said coating being in the form of :a dispersion with the particulate material having a maximum average particle size of approximately 10 microns, the coating containing the following ingredients:

(a) a major portion of a sensable component,

(b) a minor portion of a plastic binder and a plasticizer for said plastic binder, said binder and plasticizer combination being capable of forming a coating that has a releasable adherence to the base sheet and is blendable with a wax blend top coating at temperatures above 30 C.

(c) a wetting agent capable of assisting in the dispersion of the sensable material in a solvent, and

(d) an inert organic solvent medium;

(2) maintaining the temperature of said base sheet and coating above 30 C. for a time sufficient to substantially dry said coating on said base sheet;

(3) depositing on said dried sub-coat a top coating, said coating being in the form of a dispersion with the particulate material having a maximum average particle size of approximately 10 microns, the top coating containing a wax blend of a vegetable wax and mineral oil in dispersion form in a lower aliphatic alcohol and a solution of a synthetic resin ester prepared from rosin in a ketonic solvent; and

(4) maintaining the temperature of the two deposited layers at a level above 30 C. to induce the comingling of the ingredients thereof into a single unitary layer.

2. A coated sheet article suitable for use in transferring characters to a receiving surface responsive to the application of pressure to the reverse side thereof made in accordance with the procedure of claim 1.

3. The method of forming a coated sheet article suitable for use in transferring characters to a receiving surface responsive to the application of pressure to the reverse side thereof which comprises the steps of:

(1) disposing a coating on a polymeric base sheet, said coating being in the form of a dispersion with the particulate material having a maximum average particle size of approximately 10 microns, the coating containing the following ingredients:

(a) fifty parts of ferric black oxide,

(1)) six parts of ethyl cellulose,

(c) four parts of coumarone-indene type resin, (d) six parts of mineral oil, and

(e) one part of an oil soluble non-ionic surfactant;

(2) maintaining the temperature of said base sheet and coating above 30 C. for a time suflicient to substantially dry said coating on said base sheet;

(3) depositing on said dried sub-coat a top coating, said coating being in the form of a dispersion with the particulate material having a maximum average particle size of approximately 10 microns, the top coating containing 2.5 parts of carnauba wax, 2.5 parts of mineral oil, and 1.5 parts of a diethyleneglycol ester of hydrogenated rosin; and

(4) maintaining the temperature of the two deposited layers at a level above 30 C. to induce the comingling of the ingredients thereof into a single unitary layer.

4. A coated sheet article suitable for use in transferring characters to a receiving surface responsive to the application of pressure to the reverse side thereof made in accordance with the procedure of claim 3.

References Cited UNITED STATES PATENTS 1,546,747 7/ 1925 Pembroke 11736.4 2,318,096 5/1943 Quick 11736.4 2,762,715 9/1956 Newman 11736.4 3,029,157 4/1962 Sutheim et al. 11736.1 3,031,327 4/1962 Newman 11736.4 3,062,676 11/1962 Newman et al. 117158 X FOREIGN PATENTS 1,287,122 1/ 1962 France.

MURRAY KATZ, Primary Examiner.

Claims (1)

1. THE METHOD OF FORMING A COATED SHEET ARTICLE SUITABLE FOR USE IN TRANSFERRING CHARACTERS TO A RECEIVING SURFACE RESPONSIVE TO THE APPLICATION OF PRESSURE TO THE REVERSE SIDE THEREOF WHICH COMPRISES THE STEPS OF: (1) DISPOSING A COATING ON A POLYMERIC BASE SHEET, SAID COTING BEING IN THE FORM OF A DISPERSION WITH THE PARTICULATE MATERIAL HAVING A MAXIMUM AVERAGE PARTICLE SIZE OF APPROXIMATELY 10 MICRONS, THE COATING CONTAINING THE FOLLOWING INGREDIENTS: (A) A MAJOR PORTION OF SENSABLE COMPONENT, (B) A MINOR PORTION OF A PLASTIC BINDER AND A PLASTICIZER FOR SAID PLASTIC BINDER, SAID BINDER AND PLASTICIZER COMBINATION BEING CAPABLE OF FORMING A COATING THAT HAS A RELEASABLE ADHERENCE TO THE BASE SHEET AND IS BLENDABLE WITH A WAX BLEND TOP COATING AT TEMPERATURES ABOVE 30*C. (C) A WETTING AGENT CAPABLE OF ASSISTING IN THE DISPERSION OF THE SENSABLE MATERIAL IN A SOLVENT, AND (D) AN INERT ORGANIC SOLVENT MEDIUM; (2) MAINTAINING THE TEMPERATURE OF SAID BASE SHEET AND COATING ABOVE 30*C. FOR A TIME SUFFICIENT TO SUBSTANTIALLY DRY SAID COATING ON SAID BASE SHEET; (3) DEPOSITING ON SAID DRIED SUB-COAT A TOP COATING, SAID COTAING BEING IN THE FORM OF A DISPERSION WITH THE PARTICULATE MATERIAL HAVING A MAXIMUM AVERAGE PARTICLE SIZE OF APPROXIMATELY 10 MICRONS, THE TOP COATING CONTAINING A WAX BLEND OF A VEGETABLE WAX AND MINERAL OIL IN DISPERSION FORM IN A LOWER ALIPHATIC ALCOHOL AND A SOLUTION OF A SYNTHETIC RESIN ESTER PREPARED FROM ROSIN IN A KETONIC SOLVENT; AND (4) MAINTAINING THE TEMPERATURE OF THE TWO DEPOSITED LAYERS AT A LEVEL ABOVE 30*C. TO INDUCE THE COMINGLING OF THE INGREDIENTS THEREOF INTO A SINGLE UNITARY LAYER.

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