US3264385A

US3264385A - Method of casting a printed pattern on a plastic sheet

Info

Publication number: US3264385A
Application number: US252016A
Authority: US
Inventors: Stanley F Reed
Original assignee: American Scientific Corp
Current assignee: American Scientific Corp
Priority date: 1963-01-14
Filing date: 1963-01-14
Publication date: 1966-08-02
Anticipated expiration: 1983-08-02

Description

Aug. 2, 1966 s. F. RE ED 3,264,385

METHOD OF CASTING A PRINTEDPATTERN QN A PLASTIC SHEET 5 Sheets-Sheet 1 Filed Jan. 14, 1963 METHOD OF CASTING A PRINTED PATTERN ON A PLASTIC SHEET F1106 Jan. 14. 1963- Aug. 2, 1966 :5 Shees-Sheet 2 Aug. 2, 1966 s. F. REED 3,264,385

METHOD OF CASTING A PRINTED PATTERN ON A PLASTIC SHEET Filed. Jan. 14, 1963 5 Sheets-Sheet 5 United States Patent F 3,264,385 METHOD OF CASTING A PRINTED PATTERN ON A PLASTIC SHEET Stanley F. Reed, McLean, Va., assignor to American Scientific Corporation, Alexandria, Va., a corporation of Virginia Filed Jan. 14, 1963, Ser. No. 252,016 5 Claims. (Cl. 264-104) This invention relates to a process of printing, product thereof and to apparatus therefor. It has to do more particularly with a novel printing process wherein the material which is to form the pattern is applied to a solidifiable base or carrier material while the latter is in a fluid or semi-solid state and to novel apparatus for carrying out such process.

This application is a continuation-impart of an original application, Serial No. 831,926, rfiled August 17, 1959, for printing processes and apparatus, and now abandoned.

'In prior printing processes the material which is to form the pattern is customarily applied to the base or carrier material while the latter is in solid form. Where such base material is absorbent, as in the case of paper, for example, it is difficult to produce a pattern in very fine detail since the pattern-forming material, which is usually ink, strikes into the base material and spreads beyond the desired limits of the pattern to be produced. Where the base material is not readily absorbent, as in the case of high gloss papers, plastic materials and the like, it is diflicult to prevent the pattern forming material from spreading on the surface beyond the limits of the desired pattern. Moreover, great care is required to prevent blotting or smearing of the pattern-forming material. Printing processes employing conventional material, such as paper and common types of ink, result in products which are essentially short-lived under detrimental conditions such as those resulting from exposure to damp environment, rough usage, and the like. In addition, such products have an inherent lack of permanency, the paper being readily subject to tearing, abrasion and deterioration.

Where'the base or carrier material is of a non-absorbent nature, as for example, when it is a high-gloss paper or is formed of a synthetic commercial plastic, it is difficult to prevent smearing and spreading of the pattern-forming material on the base material. Moreover, where the base is a plastic, the pattern-forming material usually may be readily rubbed or worn oft the base material.

Patterns also heretofore have :been formed in a coating carried on a base by etching away certain portions of the coating to leave only the portions which are to form the pattern. Such technique is employed for example in forming printed electrical circuits wherein a conductive material, such as a metal, is placed on a base of insulated mate rial, such as a synthetic plastic or paper and the metal is etched away to leave the desired circuit elements. This process is both expensive and time-consuming. Furthermore, it is diflicult to control the extent of the etching and, accordingly, the accuracy of the pattern formed by the conductive mate-rial which remains after the etching. Further, it is ditficult, expensive, or impossible to derive an etched pat-tern wherein the depth and thickness of the coating may be made difierent at different points or places. Electrical conductors, for example, must in general, be

made wider when more current carrying capacity is re- :degree of accuracy and a high uniformity of quality.

quired.

Heretofore tapes for reproducing electromagnetic impulses have been formed by applying to a base material, such as a synthetic plastic, a uniform coating of magnetic particles. Electromagnetic impulses are then applied to the tape to magnetize the particles in such manner to rform a pattern whereby the impulses may be reproduced by passing the tape through suitable apparatus which is responsive to the magnetization of the particles. It has been found diflicul-t to produce such a tape wherein the information recorded thereon is truly permanent and not subject to unintentional erasure.

Patterns have heretofore been produced on sheets, webs and tapes by common photographic techniques but such techniques have been relatively expensive and time-consuming.

One of the objects of the present invention is to provide a novel method of printing which is capable of producing a pattern of extremely fine detail in a relatively permanent form.

Another object is to provide a printing process wherein the material which is to form the pattern is applied to the base or carrier material while the latter is in a fluid or semi-solid state,

Another object is to provide a printing process wherein a finely divided solid patternproducing material is embedded in the surface of the base or carrier material.

A further object is to provide a method whereby the effective thickness of the pattern-forming material may be con-trolled and caused to vary throughout the pattern as desired.

Still another object is to provide a printing process wherein the pattern-forming material is applied to the mate-rial which is to form the base or carrier during the formation of a sheet or web from the base-forming material.

A further object is to provide a novel process for em bedding finely divided solid particles in a base or carrier a sheet or web principally composed of relatively low cost material but having a high quality surface.

Another object is to provide an inexpensive but efficient process for making permanently prerecorded magnetic tape. Still another object is to provide an inexpensive and eflicient process for making permanently prerecorded optical tape.

A further object is to provide an inexpensive and effi- -cient process for making printed circuits having a high A further object is to provide a method of (forming printed electrical circuits which is simple and inexpensive and which is capable of producing with a high degree of accuracy circuits including various desired components such as resistances, capacitances, inductances and simple conductors.

It is another object of the invention to provide inexpensive and efiicient processes for making electrical cables having a plurality of mutually insulated conductors.

Patented August 2, 1966 It is a further object of the invention to provide a, 7 process wherein the base or carrier material may be readily reclaimed and reused.

Other objects and advantages of the invention will appear from the following description taken in connection with the appended drawings, wherein:

FIG. 1 is a diagrammatic illustration of apparatus for carrying out the preferred embodiment of the invention;

FIG. 2a is a perspective view showing one of the cylinders of the apparatus of FIG. 1;

FIG. 2b is an enlarged, fragmentary, longitudinal crosssectional view through a printed article formed in accordance with the invention;

FIG. 2c is a fragmeentary perspective view partially in cross-section'showing a multi-conductor electricalcable manufactured in accordance'with the invention;

FIG. 2d is a greatly enlarged fragmentary longitudinal cross-sectional view through a printed particleformed in accordance with the invention showing the pigment particles individually or collectively surrounded by the base material;

FIG. 3 is a diagrammatic illustration of apparatus-for carrying out a second embodiment of the invention;

FIG. 4a is an enlarged fragmentary cross sectional view. of a portion of the surface of one of the printing rolls in.

accordance with the preferred form of the invention;

FIG. 4b is an enlarged fragmentary cross-sectional illustration of a portion of one of the rollsin accordance with an alternative embodiment of the invention;

FIG. 5 'is an enlarged fragmentary view of a portion of ly low quality web;

apparatus for effecting high quality printing on a relative-.

FIG.=6 is a diagrammatic illustration of apparatus, in a V accordance with still another embodiment of the invention in which information is printed on a semi-soft web of base or carrier material;

' FIG. 7 is adiagrammatic perspective'view ofapparatus. in accordance with a further embodiment of the invention which is especially adapted for manufacturing strips or tapes such as magnetic tapes;

FIG. 8 is a diagrammatic illustration-of apparatus in accordance with a further embodiment of the invention in which a web-like stream of liquid is extruded ontoa flat, plate for printing thereby.

In accordance with the preferred embodiment of the invention, 'a base or carrier material is employedto form a sheet or web to which the pattern-forming material-is \applied'to produce the desired pattern. The base .or carrier material is initially in a liquid state and is caused to form afree-falling stream contacting a member carrying a semi-solid state, and later is again charged into its solid state to form a continuous web. For convenience, the

material while in any of these three states is sometimes referred to herein as web material.

Other embodiments of the invention efiect the transfer of pattern-forming particles into the surface of the base or carrier material while it is in either a liquid or semisolid state. For convenience, either or both of these states are sometimes referred to herein as moldable states,

implying that the web material is in a visco-elastic state or in a condition where it will readily change its shape and permit the pattern-forming particles to be embedded in,

and cast into, the surface of the web.

Referring now to FIG. 1, there is shown an extruder 10, adapted to extrude a sheet of liquid web 12 onto the surface of a roller 14.

The liquid web 12 is preferably a plastic maintained in its liquid state by reason ;of a high temperature within extruder 10, but may be any .materialwhich is in its solid state at ordinary room temperatures, but capable'of being easilymelted. The web material may be either thermosetting or thermoplastic, and it is found that nylon which is in its liquid state at about 500 F., may conveniently be used. The web materialpreferably Wets the materialof which the rolls are constructed.

Roll 14 is rotated in a counterclockwise direction-and carries with it the liquid web 12 on its surface. After the,

liquid web has travelledapart way. around the :circumdistance between rollers14 and 16.?

Both 'rollsi14and 16 have surfaces which'are engraved or otherwise provided with depressions in accordance with;

the information to be. printed on the web, inthe manner, shown in FIG. 2a.

FIG. 2a. also shows the manner in which the coolant-is introduced and extracted from chilling roll 16. The pipes 18,-in addition to carrying the coolant, also form an axle for the roll. Each pipe is i'connected toa coupling-bearing assembly 23 which supports the-.roll and at. the same time; allows passage.of'coolantthrough tubes 25, which remain stationary and do=not rotate. The coolant, which may conveniently be .ethylene glycol, is circulated through a refrigeration: apparatus which -'closelycontrolsits temperature before being reintroduced into .the chilling. roll. The

r-oll isi provided with ya .surface which has very high heat conductivity, and may conveniently be any suitable metal.

The surface is preferably relatively thin ;to allow a large amount of heat: to be transferred in a short time, thus maintaining the temperature 'at the surface ofthe chilling roll relatively; constant and'invariable.

The depressions 21Jare filled during the .course :of the rotation of each roller with small particles of, pigment fed through

hoppers

22 and 24 to applicators 26:.and 28.

Doctor blades

30 and 32 on each roller scrape off'the excess pigment, allowing it to occupy only the depressions in the. roll representative of I information tobe printed. The-.ssmallparticles 'of pigmentmay; be either in dry powder form, .or in a visco-elastic state as a thick suspension. In the, latter case, the suspension maybe formed in" any liquid which will wetsthe rollsiand' be chemically compatible. with the liquid web material.

The particles themselves are very finely divided solid matter, and are preferably of the;order, of a few microns in diameter.;, The particles are chemically compatible with i the liquid web material: and distinguishable therefrom by opticalor magnetic characteristics and,'preferably,= of a material which vdoes not dissolve in the hot liquid carrier. Many materials have these characteristics as; for example, finely divided iron or one ofthe oxides ofiron," and any of these materials may. be used.

As roller 14 receives the.liquid web 12,ithe liquid runs into the engraved portionaof each roller. and commingles with the solid pigment particle's, occupying those depres sions.;

Thehot liquid is very fluid and easily runs around the particles of pigment, no matter how tightly they may be packed into the depressions and completely surrounds them by wetting the roll around the .depression. This efifect may be greatly enhanced by selecting a material for the surfaces of the r0lls'14 and 16for which the liquid has great afiinity, and readily wets.- Ifnylon is used as the webmaterial, the use of stee1;for the surfaces of the rollsiwillenhance this'eifecgbecause of 'hotnylons great afi'inity for -steel.

The liquid ,web does not solidifythroughout its thick-1 ness immediately upon contactwith roll 14, although the v surface of the web next to the roll may be converted into the solid state. The outside surface remains in the liquid state until it encounters the chilling roll 16. The liquid web is then converted into a solid state in a very short time, but not before it also has oommingled with the solid pigment borne by the depressions in roll 16. The solidified web emerges at 20, in a solid state, with the solid particles borne by the engravings of both rolls cast into both its surfaces, thereby resulting in the finished product, shown in cross-section in FIGS. 2b and 2c.

It will be seen from FIG. 20 that the printed Web comprises a base portion 31, and raised portions 33 which contain the pigment particles embedded therein. The raised portions 33 are due to the casting effect of the web into the depressions in the rolls, and its solidification in that shape. The result of the casting of raised lines where the printed indicia represented by the pigmentappear, is to increase the definition of the printed product. A three-dimensional effect is created in which the printed image has depth, as well as color and form.

The thickness of the base portion 31 of the printed product can be closely controlled by adjusting the extrusion speed of extruder 10, the speed of rotation of

rolls

14 and 16, and the distance of the space between

rolls

14 and 16. The height of the raised portions 33 can be closely controlled by regulating the depth of the depressions formed in the rolls. Thus, by suitably forming the depressions in the rolls, the reproduction of paintings may be made more accurate by correctly depicting the third-dimensional effect created by the height of the brush strokes.

The definition attainable on the printed web is limited only by the size of the particles of pigment which are used, and the exactitude with which the depressions are formed in the rolls. The fineness of lines which may be accurately printed approaches the invisible.

FIG. 20 shows a transverse cross-sectional illustration of a cable which may be manufactured with the apparatus of FIG. 1. The cable is shown in two sections, a top section and an identical bottom section, each of which is provided with eight conductors 33 cast into their surfaces, four on each side of the base 31. Each of the sections of the cable may be manufactured with the device of FIG. 1, with the depressions in

rolls

14 and 16 forming circumferential grooves. Each of the grooves is filled with particles, as described, which are in this case electrically conductive, thus forming a cable section as show.

The conducting particles making up the conductors of the cable form a continuous conductive path throughout the cable. However, to insure that such a conductive path exists, a high voltage is applied to the ends of each conductive portion in order to break down any insulating web material interrupting the conductive path. Alternatively, the entire cable is exposed to a high intensity magnetic field produced by an electromagnet fed by a high frequency alternating current. Eddy currents are produced in the conductive particles, in response to the magnetic field, and those currents raise the temperature of the particles. The magnetic field strength is sulficiently strong, and the resulting eddy currents are sufiiciently large as to raise the temperature of the conductive particles above the melting point of the web. Any portion of the web material lying between the conductive particles is thus melted away, allowing the current path of the conductors to be completed.

The two steps of application of a high voltage and exposure to a magnetic field may conveniently be performed at the same time, thus insuring that the current carrying paths are completed.

The dimensions of

rollers

14 and 16 are not critical for the casting of the particles into the web. They must, however, have a large enough diameter to accommodate the amount of information to be printed onto the web.

The temperature of roll 16 is maintained at a sufiiciently low temperature by the coolant hereinbefore descrew feed, for example.

scribed to effect solidification of the liquid web almost instantly on contact. The temperature of roll 14, on the other hand, may conveniently be at room temperature, and thus is shown in FIG. 1 as not having a pipe for insertion of coolant. At normal speeds of operation, the maintenance of roll 14 at room temperature will be sufficient to bring down the temperature of the liquid web to a semi-soft state whereby the lower temperature of roll 16 can best perform its function of simultaneously casting the pigment and solidifying the web. At greater speeds, however, it is necessary to also cool roll 14 in the same manner as has been described for roll 16.

When nylon or other thermoplastic materials are used, the web material may be easily reclaimed from scrap, by the simple process of remelting. The pigment, being in the form of solid particles, will settle to the bottom of the reliquified web material, and may also be extracted by filtration. There is, therefore, no wastage involved in the process according to the invention.

An alternative form of apparatus for printing embodying the invention is shown in FIG. 3. In this figure, the liquid web is fed from a well 34 formed between two

chilling rolls

36 and 38, which are rotated together at the same peripheral speed. A thin film of the liquid web is solidified by the surface of each of the

rolls

36 and 38 as the surfaces of those rolls pass through the well, thereby casting the particles into the surface of the web in the same manner as in FIG. 1. The two films of web, each of which is solidified on the roll side, but still hot and in its liquid state on the well side, proceeds around the

rollers

36 and 38 and are squeezed together to form a single solid web into which the particles have been cast on or into both surfaces. This arrangement also produces the finished product of which FIGS. 2b and 2c are crosssections.

In this embodiment, strands of cheap fiber-filling material may be used to reduce the cost of the printing by reducing the amount of web required to form a given final thickness. They are fed into hopper 35, along with the liquid web which fills Well 34. The filler material is not forced into the depressions of the rolls, but remains in the body of the web, serving to strengthen it.

The well 34 of liquid web material is fed by a hopper 35 which maintains the well of hot web material at the correct level. This correct level is a function of the speed of the

rolls

36 and 38, and of the temperature of the liquid in the well. The hotter the material, the longer it will take to solidify a given thickness of it, thus necessitating a higher level to permit the cooling to be started earlier; and faster peripheral speeds of the rolls also make it necessary to raise the level to permit the proper cooling time.

These relationships also affect the final thickness of the printed product in the following manner. As a point on one of the rolls contacts the well by being rotated into it, a small amount of liquid runs into the depressions of the roll carrying the pigment, and immediately solidifies. As the roll continues to rotate, the chilling effect of the coolant will be felt farther into the well from the surface of the roll, and a progressively thicker film is solidified as that point travels through the well. The rate at which the thickness increases around the roll is dependent on the speed of the roll, and the temperatures of the liquid and the roll.

In both FIGS. 1 and 3, the solid particles comprising the pigment are applied to the rolls by

applicators

26 and 28 which maintain the supply of particles, fed from

hoppers

22 and 24, at a suitable pressure, by means of a The pressure thus causes the pigment to fill the depressions in the rolls, and any excess pigment is removed by

doctor blades

30 and 32.

When the liquid web touches the rolls, it will completely occupy those depressions mingling around the solid particles. The detail of the printed representation attainable by the use of apparatus as shown in FIG. 3 is the same as that obtainable by the use of FIG. 1 apparatus,

causing the chilling rolls to maintain a very high temperature, sufficient to drive off the volatile solvent on contact. The pigment particles carried by the depressions in these rolls are cast into the web while it is in its dissolved state,- and are retained in the surface of the .web

as it is simultaneously solidified by driving off thesolvent. The rolls in FIGS. 1 and 3 may be of the form shown in FIGS. 4aand 4b. The roll proper is madeof an electrically conductive material 42 having a removable" ex-' When the ternal shell '44 of non-conductive material. roll is engraved, or depressions are otherwise formed there-. in, the grooves thusproduced extend through the thickthe conductive roll material 42. The pigment particles are held in the grooves by electrostatic forces produced. by opposite electrical charges on the particles and on the conductive portion of the roll.

force of gravity to overcome the inherent centrifugal force and, hold the particles within the grooves. The brush 45 and slip ring 46 of FIG. 1 is connected to a positive source of potential 48. and permits a positive charge. to

be applied to the conductive portion of the surface of the This type roll is preferred. when the rollers are rotating toofast to allow the normal ness of the non-conductive material 44 thereby exposing roll, causing negatively charged particles to remain in the grooves, held there by electrostatic attraction.

charge on the roll material 42'.

The roll of FIG. 4a may also be used to provide ad-.

When

herence of the particles by magnetic attraction. the roller is thus used, the small solid particles are of the magnetically permeable material such as iron, nickel, and cobalt,'or compounds of these elements. The outside channel is then composed of magnetically non-permeable material, whereas the roll proper is a material 42 in which a relatively strong magnetic field is set up, by either a permanent magnet or an electromagnet. The particles will tend to remain in those portions of the magnetic field in which the lines of flux are most highly concentrated, which, .of course, are the grooves exposing the magnetic material.

FIG. 4b shows a cross-sectional view of an alternative roll, which is composed uniformly of an electrically conductive or a magnetically permeable material, and which has a smooth surface without any engravings or other depressions formed therein. When this roll is used, the roll is caused to attract either electrically charged particles (by electrostatic attraction) or magnetically permeable particles (by magnetic attraction) in the same manner as the roll of FIG. 4a. The particles thusattracted are caused to adhere to the. surface of the rollat the place where they land, and there is, therefore, no,

shifting of position permitted of particles on the roll, and

the particles are held in position in small piles 46. When these particles are cast into the web, of course, no,

raised portions are formed, and the thickness of the web must be sufiicient to accommodate these particles ,when' they are cast into both sides of the web at the same point. Some loss of definition of the printed web resultsfrom the use of rolls constructed as shown in FIG. 4b, but:,the. advantage in their use lies in the fact that no engraved.

surface need be provided on the roll. 7 Thus preparatory steps need not be taken in the way of forming depressions, etc., to achieve the printing of the invention.

is primarily composed of cheap, low quality paper.= The Of course, positively charged particles will require a negative paper 78 is fed from-a paper .supplyy(not shown), and.

passed between rollsf82 and 84, which are of thesame type as the chilling vrolls hereinbefore described: Two.

wells, 86 and 88 are formed between the paper 78 and each ofthe=rolls82 and 84. The wells contain the webv surface, in.liq'uid form, in the samemanner as has been described ,in connection with FIG.,3. The operation of the apparatus is also the same as that of'FIG. 3, with the exception thatonly. a veryv thin film of webis allowed to solidify before .the web reacheszthe nip between the-rolls;

The two solidified films of web, with their inside surfaces still liquid; ,are pressed'together with the paper. 78 between them. The paper .78 constitutes the supporting member of the finished :web' 92,. 'Whichis thus comprised primarily of inexpensive paper; ;78 but.with high quality. Web surefaces 94 and 96;,int-o which thersolid: particles-have been;

cast This process produces the advantageous. result of allowing high quality printing ;up on a web which is primarily of inexpensive material, and eliminates. the. necessity of providing high quality, material throughout. the entire .web, or of providing a sufiiciently thickJsurface portion :to be self-supporting.

FIG. 6 illustrates apparatus. embodying the invention 1 in which the printing of the web is effected while .it isin' -a semi-soft state.y Extruder 10 extrudes; the liquidweb material onto a roll 14. .These elements are identical to; thesirnilarly numbered elements shown in FIG. l.' The roll 14 is uncooled fornormalprinting speeds, andthe resulting web falling off roll 14 is in a semi-soft,state',;

not yet completely solidified; The web falls between rolls 93 and which-are provided with depressions filled with pigment particles by

applicators

97 and 99, respectively, 'and excess pigment is removedby doctor- '

blades

101 and 103. Rolls 93 and .95-"are also at-room temperature and are rotatedtogether at the same. peripheral speed, thereby casting the pigment carried. inthe depressions into the surface ofthe web.

Even though rolls 93 and 95 are not chilled, they tend to lower. the/temperature of the semi-softweb, and the web is also cooled by its passage through the air. The speed of the semi-soft web is so fast,:however, that a negligible amount of heat transfer takes place, andthe web emerges at 105, after having successively passed through three additional similar pairs of rolls, still in a semi-soft state. They web thenpasses through

chilling rolls

107 and 109, which are cooled inthemannerhereinbefore described, was to transform the web into its solid state.

Each of ithe .pairs of-printing rolls have depressions filledwith particles of pigment, and the depressions; in

each set correspond to color separations of the -information to be printed.1 The particles castinto the surface of the Web by each set of rolls are of the color correspond-v ing to the color separationrepresented by the depressions in. the. roll. The resultant web is therefore printed in :four colors in accordance with the information to be printed, as for example, apicture.,..

this semi-soft state is achieved is not :critical andrnay be any temperature at which the liquid web enters the depressionsv of the rolls and the pigment particles are fully cast into the web surface. The correct temperature is in the vicinity of 430 F. when nylon is used asthe web material.

FIG. 7 illustrates apparatus embodying the; invention which 'is'adapted for the cheap and efiicient production of Rolls 98 and l00 are, of the..- same form as those described in connection with FIGS.

unrecorded .magnetic tape.

100. Rolls 106 and 107' carry electrostatically charged particles by means of an electrostatic attraction. The particles fill the grooves 102 in

rolls

98 and 100, and are cast into the ribbons of webs 108 which emerge from between the two

rolls

98 and 100. The result is that each of the ribbons 108 has cast into both of its surfaces a uniform distribution of magnetically permeable particles and is therefore suitable for use as reversible magnetic tape. The advantage of this method of manufacture is its speed and uniformity of completed product.

This apparatus may be combined with the apparatus illustrated in FIG. 5 in order to produce paper having several stripes of magnetizable material bonded to its surface. Such paper is useful in business machines of various kinds in which it is desired to magnetically record data written on the paper, to enable automatic reading of that data.

FIG. 8 is an illustration of the apparatus embodying the invention which may be used if discontinuous sheets of printed web are desired. A flat plate 122 is provided with depressions 124 in accordance with the image desired to be produced and is reciprocated in the direction of arrows 126. The liquid web is extruded from extruder 10 during the time that plate 122 is passing under it, and the liquid web 128 lying on the plate is carried forward to chilling roll 130. Roll 130 may also be provided with depressions representative of an image desired to be printed on the opposite side of the web. The depressions on both the plate 122 and the roll 130 are filled with particles of pigment which are than cast into the surface of the web 128 as it solidifies. The particles may be applied to the engraved portions of roller 130 and held thereon either magnetically or electrostatically in the manner previously described, the excess being wiped off with a doctor blade 132. Particles may similarly be applied to the engraved portions of plate 122 and the excess removed with a similar doctor blade. With this process, it is not necessary to provide any electrostatic or magnetic means for making the particles adhere to plate 122, since gravity is sufiicient.

It will therefore be seen that the invention shown and described herein satisfies the objects hereinbefore set out by providing methods and apparatus for producing extremely fine detail of printed indicia, which detail may be enhanced by the fact that the lines making up the indicia and containing the particles of pigment are raised above the surface of the web.

It can also be appreciated that the printed result is considerably more permanent in form than is paper, since the Web may be composed of a very hard and durable plastic such as nylon. The speed of production of the printed articles is also extremely high because of the nature of the web in solidifying almost immediately upon contact wit-h the chilling rollers.

It is evident that the product of the present invention has a high degree of resistance to abrasion and tearing andthat the indicia printed thereon is highly resistant to being smudged, marred, or otherwise obliterated.

Having thus described certain exemplary emlbodiments of my invention, what I desire to claim is:

1. A method of producing an article having a pattern of predetermined configuration arranged therein, comprising the steps of applying finely divided, solid particles to preselected portions only of at least one face of a base material while said base material is in a moldable state, said preselected portions of said base material defining the said pattern,

causing said base material to completely enclose said particles,

and thereafter solidifying said base material while maintaining the enclosed particles in said pattern, whereby said particles are held in said pattern by said base material.

2. A method as set forth in claim 1 wherein said particles are applied to selected portions of said base material and are enclosed by said base material by the steps of placing said particles in a cavity in a mold member having a surface more wettable by said base material than by said particles, and there-after supplying said base material in liquid form to said cavity,

whereby said base material flows around said particles as it follows the surfaces of said cavity.

3. A method as set forth in claim 2 wherein said particles are electrically conductive and said base material is an electrical insulator.

4. A printing process for casting a plastic sheet having a predetermined pattern of finely divided solid particles embossed thereon, comprising the steps of providing a mold having depressions on one face thereof in the shape of said predetermined pattern,

at least partially filling said depressions with said finely divided solid particles, thereafter covering said one face of said mold with a thin layer of fluid plastic material in which said particles are insoluble such that said fluid flows into said depressions and commingles with said particles while said particles remain in said depressions,

then causing said plastic material to set while maintaining said particles in said depressions .to bind said particles together and to said plastic material, and

then removing said plastic material and said particles from said mold,

thereby to provide a plastic sheet on one surface of which said particles are embossed in said predetermined pattern.

5. A printing process as set forth in claim 4 wherein said particles are pigment having a color different from that of said plastic material.

References Cited by the Examiner UNITED STATES PATENTS 2,326,723 8/1943 Fasold et al. 161l58 2,720,476 10/ 1955 Baymiller 161l58 2,740,991 4/ 1956 Hess et al. 264-349 XR 2,936,814 5/ 1960 Yakubik 264271 2,963,748 12/1960 Young 264l04 2,981,981 5/1961 Luhn 264l04 3,029,403 4/1962 Kreuger 264131 XR 3,085,295 4/ 1963 Pizzino et al. 264--272 XR FOREIGN PATENTS 712,865 8/1954 Great Britain.

715,207 9/ 1954 Great Britain.

768,706 10/1954 Great Britain.

ROBERT F. WHITE, Primary Examiner. ALEXANDER H. BRODMERKEL, Examiner.

I. R. DUNCAN, J. A. FINLAYSON,

Assistant Examiners.

Claims

1. A METHOD OF PRODUCING AN ARTICLE HAVING A PATTERN OF PREDETERMINED CONFIGURATION ARRANGED THEREIN, COMPRISING THE STOP OF APPLYING FINELY DIVIDED, SOLID PARTICLES TO PRESELECTED PORTIONS ONLY OF AT LEAST ONE FACE OF A BASE MATERIAL WHILE SAID BASE MATERIAL IS IN A MOLADABLE STATE, SAID PRESELECTED PORTIONS OF SAID BASE MATERIAL DEFINING THE SAID PATTERN, CAUSING SAID BASE MATERIAL TO COMPLETELY ENCLOSED SAID PARTICLES,AND THEREAFTER SOLIDIFYING SAID BASE MATERIAL WHILE MAINTAINING THE ENCLOSED PARTICLES IN SAID PATTERN, WHEREBY SAID PARTICLES ARE HELD IN SAID PATTERN BY SAID BASE MATERIAL.