SILK SCREEN TACTILE PRINTS AND PROCESS

Abstract: Production of a tactile print using an improved silk screen process which provides a product with raised imprinted surfaces of sufficient local definition to permit tactile "reading" of the print. In the case of a surface imprinted with Braille patterns, the process provides a low cost touch-readable imprint of acceptable clarity and depth for use by Braille readers. The process uses known silk screen procedures using a screen ranging in mesh per square inch from 60 to 100, in combination with high viscosity "ink", which may in some instances be non-pigmented. The process includes the provision of underside spacers, and may also utilize air pressure differential across the thickness of the screen to facilitate flow of the "ink", together with controlled drying rates.

Description: SILK SCREEN TACTILE PRINTS AND PROCESS TECHNICAL FIELD This invention is directed to a printing pro¬ cess, and in particular to a silk screen process for pro¬ ducing tactile prints of high definition, such as Braille characters, and to the printed product. BACKGROUND ART The silk screen printing process is well known, and of ancient antecedents. The ink or other pigment to be deposited upon a surface being imprinted is caused to flow downwardly through a fine mesh screen, and deposited upon a printing surface or substrate located beneath the screen. The desired pattern to be printed is initially imposed upon the screen, with adjacent non-print areas being rendered impervious to ink flow, such that passage of a wave of the printing media across the screen results in selective deposition of the ink through the screen onto the surface below. Owing to the utilization by the process of photographic technology in the preparation of the screens, it is possible to achieve an accuracy of printing that enables precise, multicoloured printing, the printed composite image being formed by successive screen overlays, each screen being used with a selected colour, to achieve precise colour combinations. The nature of the inks thus used do not provide a pattern that is effectively traceable by touch, being therefore effectively tactile-insensitive. Braille patterns, as used by sightless or semi- sighted people comprise a series of "characters" each comprising up to six raised dots in patterned arrange- ment, to form indicia. These dots are embossed and raised from the reading surface so as to present a tactile pattern that, with training, can be "read" through the finger tips. The existing methods of "printing" Braille require the use of embossable media such as paper, cardboard, fort and the like, where a raised impression of circular dots of suitable definition and height may be impressed, to form the Braille indicia. The process requires the use of special machinery and is limited in the types of mat¬ erial that may be thus embossed. Use of Braille requires the user to be trained in its "reading", a capability possessed at most by about forty percent of sight handicapped people. DISCLOSURE OF THE INVENTION The present invention provides a process for silk screen printing an upstanding print of sufficient height and definition to permit "reading" thereof by touch. In the case of Braille indicia, the present in¬ vention provides an imprinted surface wherein the im¬ printed dots are of sufficient height and lateral dimen¬ sion to permit ready reading by trained Braille "readers" of the indicia thus formed. In the subject process a screen is prepared with a desired printing pattern by an existing screen preparation process. An underlying spacing medium is provided. In its simplest form, as in the case of printing Braille, this spacing media may comprise a series of thin strips laterally offset from the screened printing pattern, to effect spacing of the screen underface a predetermined distance above the substrata surface being imprinted. The "ink" to be used should be of the highest "body" and lowest fluidity compatible with the process. This facilitates achieving the desired shape and height of deposition, while the rate of slump is minimized until drying of the print becomes effective. While the use of pigment therewith, as in the case of normal ink, facili¬ tates the carrying out of the process, in the case of Braille printed matter use of such pigmentation may not be necessary. In applying the present process, the high vis¬ cosity of the deposited medium facilitates the use of a deep "flood", while use of a squeegee of suitable hard¬ ness, ranging from medium hard to hard promotes the ef¬ fectiveness of deposition. In general, the screen spacing media, in the form of spacer strips extend longitudinally beneath the screen, lying in generally parallel relation with the path of movement of the squeegee, and the directional flow path of the flood. In addition to the foregoing, the application of an air pressure differential across the thickness of the screen further facilitates the transfer of the fluid medium, through the mesh of the screen and onto the sub¬ strate surface being imprinted. In a preferred embodi¬ ment the air pressure differential is applied by suction. A contemplated procedure for providing the re- quired 5 to 10 thou of spacing media comprises spraying the reverse face of the patterned silk screen with a suitably thick spacer coating, the opposing passage of air through the printing pattern precluding deposition of spacer material adjacent the pattern, and then drying the spacer coating. The tactile print capability of the present invention makes possible the widespread production of tactile printed material more suited to the needs of sight-handicapped people not trained in reading Braille. The present invention further provides an article having a print face, the print face having a substantially smooth reference surface, and at least one non-embossed, tactile-sensed substantially rigid raised pattern thereon, to enable tactile reading of the pattern. The aforesaid raised pattern may be differently coloured from the reference surface, to permit visual access to the pattern. It will be understood that the article may comprise a card, such as a greeting card. It will be further understood that the print face need not be planar, but may comprise outwardly convex surfaces, over which the printing screen can be readily rocked, in carrying out the process. The raised pattern according to the invention does not require to be limited to dots. BRIEF DESCRIPTION OF THE DRAWINGS Certain embodiments of the invention are de¬ scribed by way of illustration, without limitation of the invention thereto, wherein; Figure 1 is a schematic plan view of a printing frame and screen for imprinting Braille-like characters, in accordance with the present invention; Figure 2 shows a tactile readable imprinted pattern resulting from the Figure 1 arrangement; Figure 3 is a section view taken at 3-3 of Fig¬ ure 1; and Figure 4 is a lateral view of the Figure 1 ar- rangement. BEST MODE OF CARRYING OUT THE INVENTION Reference is first made to Figures 1 and 3, with reference also to Figure 2. In order to produce an imprinted dot pattern 20 as that shown in Figure 2, a silk screen 10 is first prepared wherein all of the sur- face of the screen is covered with a photosensitive emul¬ sion, which is dried. The screen 10 is the photographi- cally exposed to a negative of the desired image (i.e. in accordance with Figure 2) . The series of dots of Figure 2, representing the desired image is then washed off from the exposed screen 10, leaving a series of circular imprints 12 over an otherwise still-emulsioned screen surface 13. Spacer means 12 1 , illustrated schematically in Figure 1 as a series of dashed lines and in Figure 3 as spacer pieces having a section of some 0.04 inches to 0.05 inches wide by 0.005 inches to 0.010 inches (i.e. 5 to 10 thou) thick, are secured to the underside of screen 10, adjacent the pattern of columns of indicia. A pool 14 of a dense "ink" is deposited at one end of the screen 10, within the confines of the support¬ ing frame 16, by which the screen >10 is supported, to form a "flood" . A squeegee 18 (See Figure 4) is used to locally depress the screen 10 in front of the flood (pool 14) of ink, causing the flood to flow leftwardly across the sur¬ face of screen 10 in following relation with the squeegee 18 as it transverses the screen leftwardly, thereby fill- ing the imprinted interstices of the imprints 12, and permitting limited downward flow of the ink through and past the screen 10. The application of vacuum, by way of suction box 22 produces air downflow as indicated by the downward arrows, and promotes the deposition of "dots" 23 onto the underlying print substrate 24. This may be of paper, cardboard or almost any other type of surface to which the "ink" will adhere. The printed substrate 24 is then removed and subject to rapid drying, such as with a heat lamp. INDUSTRIAL APPLICABILITY The presently disclosed process provides a printed product having a significantly raised imprint of adequate prominence to permit tactile reading, and makes the printing of Braille and other tactile matter acces¬ sible to silk screen apparatus and techniques.

Claims: What is Claimed: 1. The method of imprinting a substrata with raised indicia having sufficient prominence to permit digit-wise tactile reading therefrom, comprising the steps of: providing a mesh screen having a sufficiently large mesh size to permit the passage of viscous deposi¬ tion medium therethrough; impermeably coating a surface of said screen, and leaving a desired pattern of perme¬ able interstices thereacross; locating substrata support means beneath said screen in spaced relation therefrom, having said substrata in supported relation thereon; in¬ terposing spacing media of predetermined thickness be¬ tween the underside of said screen and said substrate; depositing a pool of said deposition medium on said screen; displacing said pool across said screen, for gen¬ eral distribution and for localized passage of said med¬ ium through said interstices and into said substrata in upstanding relation thereon; and drying said upstanding medium to provide prom¬ inent tactile indicia. 2. The method as set forth in Claim 1, including the step of applying air pressure differential to said screen, to enhance passage of said medium into and through said interstices of said screen. 3. The method as set forth in Claim 1, said sub¬ strata support means comprising separator strips of pre¬ determined thickness, said interposing step including orientation of said strips in the direction of displace¬ ment of said pool across said screen. 4. The method as set forth in Claim 1, said step of displacing said pool comprising displacing said screen to cause flow of said deposition medium across said screen surface. 5. The method as set forth in Claim 1, said screen displacing step comprising depressing said screen local- ly, in a localized zone adjacent said pool, and moving said localized depressed zone away from said pool at a rate substantially equal to the rate of lateral flow of said pool. 6. The method as set forth in Claim 1, said mesh size lying in the range 50 to 100 mesh per square inch. 7. The method as set forth in Claim 1, said spac¬ ing media having a thickness in the range 0.005 inches to 0.010 inches. 8. Apparatus for depositing raised indicia upon a supporting substrata, comprising silk screen means having a mesh size in the range 50 to 100 mesh per square inch, some of said mesh being unobstructed; spacer means locat¬ ed below said silk screen means having a thickness in the range 0.005 to 0.010 inches; substrata support means located below said silk screen means; substrata located upon said support means, for imprinting through said un¬ obstructed mesh; pool supply means to deposit a flood of high viscosity indicia imprinting media upon said silk screen means; and squeegee means for depressing said silk screen means adjacent said flood, in use to enable passage of said flood in flowing relation across said silk screen means, for penetration of said imprinting media through and past said unobstructed mesh, in adher¬ ing relation with said substrata. 9. An article having a print face, said print face having a substantially smooth reference surface, and at least one non-embossed, tactile-sensed, substantially rigid raised pattern thereon, to enable tactile reading of said pattern. 10. The article as set forth in Claim 9, at least a portion of said raised pattern being differently coloured from said reference surface, to permit visual access to the pattern. 11. The article as set forth in Claim 9, comprising a card of predetermined shape, said pattern comprising a communication. 12. The article as set forth in Claim 11, said raised pattern being distinctively coloured. AMENDED CLAIMS [received by the International Bureau on 19 November 1993 (19.11.93); original claims 6 and 9 cancelled; claims 7-12 renumbered as claims 6-10 other claims unchanged (4 pages)] What is Claimed: 1. The method of imprinting a substrata (24) with raised indicia (23) having sufficient prominence to per¬ mit digit-wise tactile reading therefrom, comprising the steps of: providing a mesh screen (10) ; impermeably coat¬ ing a surface (24) of said screen, and leaving a desired pattern (20) of permeable interstices thereacross; locat¬ ing substrate support means (16) beneath said screen in spaced relation therefrom, positioning said substrate in supported relation thereon; depositing a pool (14) of said deposition medium on said screen (10) ; displacing said pool across said screen, for general distribution and for localized passage of said medium through said interstices and into said substrata in upstanding rela- tion thereon; characterized by said mesh screen (10) hav¬ ing a mesh size lying in the range 50 to 100 mesh per square inch to permit the passage of viscous deposition medium therethrough; and drying said upstanding medium to provide prominent tactile indicia (23) . 2. The method as set forth in Claim 1, further characterized by the step of applying air pressure differential to said screen, to enhance said passage of said medium into and through said interstices of said screen. 3. The method as set forth in Claim 1, further characterized by the step of interposing spacing media (12 1 ) of predetermined thickness between said screen (10) and said substrate (24) ; said spacing media (12 1 ) comprising separator strips (12 1 ) of predetermined thickness, said interposing step including orienting said strips (12 1 ) in the direction of displacement of said pool (14) across said screen (10) . 4. The method as set forth in Claim 1, said step of displacing said pool comprising displacing said screen to cause flow of said deposition medium across said screen surface. 5. The method as set forth in Claim 1, said screen displacing step comprising depressing said screen local¬ ly, in a localized zone adjacent said pool (14) , and moving said localized depressed zone away from said pool at a rate substantially equal to the rate of lateral flow of said pool (14) . 6. The method as set forth in Claim 3, said spac¬ ing media (12 1 ) having a thickness in the range 0.005 inches to 0.010 inches. 7. Apparatus for depositing raised indicia upon a supporting substrata, comprising silk screen means (10) having some of the mesh thereof being unobstructed; substrata support means (16) located below said silk screen means (10) ; substrata (24) located upon said support means (16) , for imprinting through said un¬ obstructed mesh; pool supply means to deposit a flood (14) of high viscosity indicia imprinting media upon said silk screen means (24) ; and squeegee means (18) for depressing said silk screen means (10) adjacent said flood (14) , in use to enable passage of said flood (14) in flowing relation across said silk screen means (10) , for penetration of said imprinting media through and past said unobstructed mesh, as a raised pattern (23) in adhering relation with said substrata (24) , characterized by said silk screen (10) , having a mesh size in the range 50 to 100 mesh per square inch, and by spacer means (12 1 ) located below said silk screen means (10) , having a thickness in the range 0.005 to 0.010 inches. 8. The article as set forth in Claim 7, at least a portion of said raised indicia (23) being differently coloured from said supporting strata (24) to permit visual access to the pattern. 9. The article as set forth in Claim 8, comprising a card of predetermined shape, said pattern comprising a communication. 10. The article as set forth in Claim 9, said raised pattern being distinctively coloured.

Inventors: PEREZ JUAN, YIM JOAN MARILYN, PEREZ, JUAN, YIM, JOAN, MARILYN
Applicants: 498775 ONTARIO LIMITED DOING B, 498775 ONTARIO LIMITED, DOING BUSINESS AS INTERNAT
Application year: 1993
Main classification: B41M3
IPC codes: B41M1, B41M3, G09B21