CA2135022A1

CA2135022A1 - Verification latent image

Info

Publication number: CA2135022A1
Application number: CA002135022A
Authority: CA
Inventors: Robert P. Coe; Theodore Blend
Original assignee: Robert P. Coe; Theodore Blend; Moore Business Forms, Inc.
Current assignee: Moore Business Forms Inc
Priority date: 1993-11-04
Filing date: 1994-11-03
Publication date: 1995-05-05
Also published as: JP2742226B2; NZ264863A; GB9422030D0; GB2283456A; FR2711945A1; FR2711945B1; JPH07223359A; US5468581A; GB2283456B

Abstract

ABSTRACT OF THE DISCLOSURE

A security document with a design (e. g. a generally oval seal) is constructed in such a way that the design is full value halftone, such as produced from juxtaposed line screens having a frequency between 100-133 lines per inch.
Negative and positive masks having an image (e. g. arabic numeral, letter, or other symbol), are used with the screens to produce a printing plate. A document is printed with the printing plate in a conventional lithographic process, and there is an overprinting on the design (at least that portion having the image) with a white opaque ink or overprint varnish to produce an image. The image is not readily visible to the naked human eye when viewed generally perpendicular to the plane of the document, but is readily visible by the naked human eye when the document is tilted so that it is viewed distinctly non-perpendicular to the plane of the document. A fluorescent material or brightener may be added to the white ink, and the image will then also be visible by shining long wave length black light on the design.

Description

~13~022 VERIFICATION LATENT IMAGE

- BACRGROUND AND SUMMARY OF THE INVENTION

Many di~ferent types of ~ecurity documents are utilized in commerce, such as watermarked paper, visible and invisible fiber~, optical variable inks, holograms, latent images (e. g.
see U S Patents 4,715,623, 4,033,059 and 4,210,345), security ;; threads with microprinting, and the like, in order to thwart ~,10 counterfeiters. Latent images have been used in security printing for many years by bank note printers using an intaglio process (utilizing engraved steel printing plates).
The latent image wa~ visible when a document printed thereby wa~ viewed at an angle, and the image was caused by the lS ~ormation of a ~light shadow from the raised ink pattern , depo~ited by the engraved printing plate. The shadow was " cau~ed by each of the raised ridges that occurred during the , printing of the pattern. Most of the printing is done using a ~, 120 line line ~creen producing a shadow in the direction away from the light source for each of the 120 lines. That is, the ,, 8hadowg 60 produced on the document create what appears to be ' a hidden image.
The invention relates to a particular method of providing a latent image, and the document produced thereby, that is ~:~2~ ~olatively ea~y tc practice using conventional materials, i9 woll c~moufl~ged when normally viewed, yet readily revealed to the nakod human eye ~imply by tilting the document (e. g. at An anglff o about 45-90 degrees to perpendicular). The invontion al~o i~ readily adaptable to the inclusion of ~30 ~luoro~cent material or brighteners in the ink providing the ;~ latent imAge, ~o that the latent image may al~o be revealed by ~ hlning a long wave length black light thereon. The latent "~ image produced according to the invention is produced by a combination of line images ~imilar to the intaglio process, but highlight~ the image when held at an angle to the light by J

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; 2 a change in the reflected light. This creates the illusion of diffexent densities of color, revealing the latent image.
According to one aspect of the present invention, a method i~ provided of producing a security feature on a document disposable in a plane. The method comprises the steps of: (a) making first and second halftone line screens of the same design; (b) superimposing the first and second screens one upon the other so that the designs provided thereon are juxtaposed; (c) producing a copy film having a ~10 full value halftone using the screens; (d) making image masks;
(e) juxtaposing the image masks and copy film to produce a printing plate; (f) printing the design with latent image on a document using the printing plate; and (g) overprinting at least part of the design with an ink or varnish; and wherein steps (a) - (g) are practiced ~o as to produce an image in the design on the document which is not readily visible to the naked human eye when viewed generally perpendicular to the plane of the document, but which i8 readily visible by the ; naked human eye when the document is tilted 80 that it is viewed distinctly non-perpendicular to the plane of the document.
St~p~ (d) and (e) are preferably practiced to make first and ~ocond mask~, one with an image, and one without, and po~ltloning the masks ~o that they align with the design on the copy fllm, and then transferring the design and image from khe copy film and masks to the printing plate.
Step (c) i~ preferably practiced by exposing the film ono~, then removlng the film from registration and rotating ~' tho ~creen~ at a predetermined angle (e. g. 90, 60, or 45 degrees) and then re-registering the film with the screens and making a ~econd expo~ure before developing the film.
Additional exposures can also be made before developing as ' necc~ary to produce a full value halftone.
Step (a) is preferably practiced to produce screens with 135 A frequency of lines in the range of 100-133 lines/inch, e. g.
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120 lines/inch; and step (f) by conventional lithographic printing. Step (g) may be practiced by using an opaque white ink or overprint varnish, or a clear, dull, or matte finish ink or varnish. The design produced by the method may be a seal, e. g. having a generally oval configuration, or a border. The image produced may be in the form of an arabic numeral, a letter, or other sym~ol (e. g. a logo).
Step (g) also may be practiced with a white ink containing a fluorescent material or brightener. The fluorescent material or brightener makes the latent image more visible when~a~ an angle, however then the method may also ~ /~1l~/7 comprise the further step of shining long wave length black light on the document to reveal the image.
The invention also comprises a document made by the ~'15 method described above.
According to another object of the present invention, a ~ecurity paper document having a planar surface is provided.
The document comprise~s: a full value halftone image printed on the planar surface; a clear, dull or matte finish ink or ~20 varni~h overprinted on at least that portion of the design ~ having the image; and the image not readily visible by the ; naked hum~n eye when viewed generally perpendicular to said plan~r sur~ace o~ the document, but being readily visible by ~ tho naked human eye when the document is tilted so that it is ,~25 viewed di~tinctly non-perpendicular to the planar surface of the document.
~ The full value halftone seal may be formed by 's conv~ntional lithographic printing proces~es using halftone line ~cxeens having a frequency within the range of 100-133 lino~/inch. The image ink or varnish may be opaque white ink or cverprint varni~h, e. g. white ink with a fluorescent materlal or brightener. The design may be a seal, e. g. one g~nerally oval in shape, and the image may be an arabic numeral, a letter, or other symbol (e. g. logo).
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213~0~2 ,, It is the primary object of the present invention to ; provide a security document with a readily revealed latent imaqe, and a simple yet effective manner of production ~i ~hereof. This and other objects of the invention will becomeclear from an inspection of the detailed description of the invention, and from the appended claims.

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BRIEF DESCRIPTION OF THE DRAWINGS

FIGURE 1 is a box diagram schematically showing exemplary steps for practicing an exemplary method according to the present invention;
FIGURE 2 i~ a top plan view of an exemplary security ;
document according to the present invention; and ; 15 FIGURE 3 i8 a perspective view of the document of FIGURE

2, held at an angle that allows the latent image thereon to be seen. ;~
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~, DETAILED DESCRIPTION OF THE DRAWINGS

~ The invention comprises a method of producing a document 'i that includes a design ~such as a seal) which reveals a lakent image when view~d at an angle (e. g. about 45-90 do~r~o0 ~rom porpendlcular) distinctly non-perpendicular to tho plane of ~ document, and the document so produced. ~3 ~xemplary ~teps for practicing the method according to the invention are illustrated schematically in FIGURE 1.
Ao ~een in FIGURE 1, irst contact ~creens are made --ao indicated wchematically at 10 -- which screens provide ; 30 ~pocialized effect whereby lines change width to produce i ohadow~ and highlight~ needed for halftone reproduction.
That Ls, two halftone line screens are constructed with a ,3 de~irod design ~art work) thereon, each line ~creen having a ~ fr~quenay of about 100-133 liens per inch (e. g. about 120 i35 llnon por inch).
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_5_ After step 10, step 11 is practiced. In the practice of ~tep 11, typically, a hlack and white of the design (such as engraved art work) is placed on a copy board of a copy camera. The copy board holds the original copy while it is being photographed by the camera. Copy film (typically a plate) is placed on the back board of the copy board to receive the photographic image from the art work once the film is exposed. A contact screen (from step 10) is ;
positioned over the film in the X or Y axis, and a film positive (preformed mask) is pinned over the screen so that - the latent image to be formed will appear exactly where it is to appear on the copy. The film is then exposed to create a full value halftone. The film is then removed from the ; registration with the copy board, the contact screen is rotated to another position (e. g. 90, 60, or 45 degrees), then the film i5 re-registered with the screen and the copy film, and a second exposure is made. The number of exposures i8 increased, as necessary, until a full value halftone is produced (i. e. like typical halftones produced in connection with continuous tone photographs prepared ~or litho printing). If additional exposures are required, the ~ oxposure time should be substantially equal to the time of

3 oach o~ the f ir~t two expo~ures.
Masko aro al~o prepared, as indicated at 16 in FIG. 1, ', 25 ~uch a~ one with an image 17 such as a letter (the letter 'M"
in FIGURE 3), arabic numeral, or other symbol ~e. g. logo), and the other wlthout. These masks are the positive and nog tlvo oxpo~ure~ of one another. If the M of FIGURE 3 is produced, the "~olid M" of one mask i~ placed over one of the ~croon~ ~rom step 10 and ma~ks out the indicia once the film iN oxpo~ed. The "clear M" mask is placed over another screen ~rom step 10 in the same fashion and allows the M to be 3 photographod with tho pattern of the design showing through I aftor oxpo~uro. Thu~ there are now two films, one with the pattern of the de~ign (e. g. seal) with the "M" (image) cut ., ,. " . ~ , ~, . .
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out, and the second with just the "M" having that porti.on of the pattern covered by the "M" filling in the area of the "M".
Then the two films are juxtaposed one over the other to transfer the combined pattern and image onto the printing plate, as indicated by step 18 in FIGURE 1. The printing plate then prints (see step l9 in FIGURE l) the latent image (17 in FIGURE 3) on a document (see the document 14 in FIGURE
2). Printing is practiced in a conventional fashion with the printing plate, producing print having rai~ed ink patterns.
- At least part of the design 13 (see FIGURE 2) -- at least that portion having the image 17 -- is then overprinted (see ~tep 21 in FIGURE 1) using an ink or varnish, such as an opaque white ink, or an overprint varnish, or a clear, dull, ~15 or matte ink or varnish. For example PMS Opaque White Ink, or AVX 300 Overprint Varnish, both available from Graphic ~3 A ~ ~ of ~orrl~ r~Lns~ Ne~-dc~e~, may be utilized, ~ /~
~ a3 may other overprint inks or varnishes. The same mask used ;~ to create the image 17 may be u~ed in the overprinting "~20 proce~s 21 if de~ired.
Tho de~ign may be a ~eal, such as the generally oval ~;
l~hough with an irregular border) in configuration, seal ,~ ~hown by ro~erence numeral 13 in FIGURES 2 and 3. An exomplary p~per tocument on which it is printed is shown by ~25 roferencc numeral 14. The document 14 produced according to the invontion, which may be a qecurity document (e. g. having indicla 20 thereon Lndicating that it i~ a bond, check, stoc~
co~ti~ t0, property title, etc.), does not readily reveal tho image 17 to the naked human eye when viewed generally ~30 porpendicular to the plane of the document 14 -- such as seen in FIG. 2. However, the image 17 is readily visible by the naked human eye when the document is tilted so that it is viowod distlnctly non-perpendicular to the plane of the document, a~ schematically indicated at 24 in FIGURE 1, and ~,35 a~ illustrated in FIGURE 3. Indicia 22 may be printed on the ' "

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; same planar surface 23 of the document 14 as the seal 13 and image 17 to instruct a user as to how to reveal the latent lmage 17.
Instead of a seal, the design 13 according to the invention may be a border, or part of a border, of a document ; 14, or other feature.
In order to enhance the visibility of the image 17 when the document 14 i5 tilted, and/or to provide another security check for the document 14, according to the invention a conventional fluorescent material or brightener, such as an anionic etilbene derivative such as LEUCOPHOR B-302, f'~ available from Sandoz of Charlotte, North Carolina, may be ~ added to the over print ink, e. g. an opaque white ink overprinting the image 17. The image 17 is then also f15 revealed by shining a long wave length black light on the ~,t; seal 13, as indicated schematically at 25 in FIGURE 1.
It will thu~ be seen that according to the present invention a method of producing a security document with latent image ~eal, and a security document with latent image seal, have been provided. While the invention has been ~ her~in ~hown and de~cribed in what is presently conceived to - b~ the mo~t practlcal and preferred embodiment thereof, it wlll ~q app~rent to those o~ ordinary skill in the art that % many modi~lcAtlons may be made thereof within the scope of ~ > j3 invention, which ~cope i~ to be accorded the broadest f intorpretation of the appended claims 90 as to encompass all rquiv~l~nt mothod~ or document~.

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Claims

WHAT IS CLAIMED IS:

1. A method of producing a security feature on a document disposable in a plane, comprising the steps of:
(a) making first and second halftone line screens of the same design;
(b) superimposing the first and second screens one upon the other so that the designs provided thereon are juxtaposed;
(c) producing a copy film having a full value halftone using the screens;
(d) making image masks;
(e) juxtaposing the image masks and copy film to produce a printing plate;
(f) printing the design with latent image on a document using the printing plate; and (g) overprinting at least part of the design with an ink or varnish; and wherein steps (a) - (g) are practiced so as to produce an image in the design on the document which is not readily visible to the naked human eye when viewed generally perpendicular to the plane of the document, but which is readily visible by the naked human eye when the document is tilted so that it is viewed distinctly non-perpendicular to the plane of the document.

2. A method as recited in claim 1 wherein steps (d) and (e) are practiced to make first and second masks, one with an image, and one without, positioning the masks so that they align with the design on the copy film, and then transferring the design and image from the copy film and masks to the printing plate.

3. A method as recited in claim 1 wherein step (c) is practiced by exposing the film once, then removing the film from registration; then rotating the screens at a predetermined angle; and then re-registering the film with the screens and making a second exposure before developing the film.

4. A method as recited in claim 3 wherein said rotating step is practiced to effect rotation at an angle of about 90, 60, or 45 degrees.

5. A method as recited in claim 3 comprising the further step of making additional exposures can also be made before developing, the number of exposures being as necessary to produce a full value halftone.

6. A method as recited in claim 1 wherein step (a) is practiced to produce screens with a frequency of lines in the range of 100-133 lines/inch, and step (f) is practiced by lithographic printing.

7. A method as recited in claim 1 wherein step (g) is practiced a clear, dull, or matte finish ink or varnish.

8. A method as recited in claim 1 wherein step (i) practiced to provide a seal having a generally oval configuration as the design.

9. A method as recited in claim 1 wherein step (d) is practiced to provide an image in the form of an arabic numeral, a letter, or other symbol.

10. A method as recited in claim 1 wherein step (g) is practiced by using an opaque white ink or overprint varnish.

11. A method as recited in claim 1 wherein step (g) is practiced with a white ink containing a fluorescent material or brightener; and comprising the further step of shining long wave length black light on the document to reveal the image.

12. A method as recited in claim 1 wherein step (g) is practiced using a mask from steps (d) and (e).

13. A security paper document having a planar surface, and comprising:
a full value halftone design and image printed on said planar surface;

a clear, dull or matte finish ink or varnish overprinted on at least the part of said design containing said image; and said image not readily visible by the naked human eye when viewed generally perpendicular to said planar surface of the document, but readily visible by the naked human eye when the document is tilted so that it is viewed distinctly non-perpendicular to said planar surface of the document.

14. A document as recited in claim 13 wherein said full value halftone design is formed by halftone line screens having a frequency within the range of 100-133 lines/inch.

15. A document as recited in claim 14 wherein said ink or varnish is opaque white ink or overprint varnish.

16. A document as recited in claim 13 wherein said ink or varnish comprises white ink with a fluorescent material or brightener.

17. A document as recited in claim 13 wherein said design comprises a seal that is generally oval in shape.

18. A document as recited in claim 13 wherein said image is an arabic numeral, a letter, or another symbol.

19. A document as recited in claim 13 wherein said image ink or varnish is opaque white ink or overprint varnish.

20. A security paper document having a planar surface, produced by the steps of:
(a) making first and second halftone line screens of the same design;
(b) superimposing the first and second screens one upon the other so that the designs provided thereon are juxtaposed;
(c) producing a copy film having a full value halftone using the screens;
(d) making image masks;
(e) juxtaposing the image masks and copy film to produce a printing plate;

(f) printing the design with latent image on a document using the printing plate; and (g) overprinting at least part of the design with an ink or varnish; and the image in the design on the document not being readily visible to the naked human eye when viewed generally perpendicular to the plane of the document, but being readily visible by the naked human eye when the document is tilted so that it is viewed distinctly non-perpendicular to the plane of the document.