Safety inks and documents

Abstract

This safety ink is useful for printing a background of fine lines or dots on a document of value, such as a bank check. The background extends over an area which is adapted to be written upon. If the area in question is written upon and an attempt is thereafter made to eradicate the writing, the background changes color, thereby making it obvious upon visual inspection that an attempt has been made to alter the writing. The ink includes a dye which is soluble and bleachable and a fluorescent pigment whose fluorescence is enhanced if the attempted alteration is by means of a dissolving or bleaching technique, so that removal of part of the dye results in a change in color and also in an enhancement of the fluorescent intensity of the remaining printed matter. If an attempt is made to alter the writing by erasure, rather than eradication, some of the fluorescent pigment is removed, and its fluorescent intensity is consequently decreased. Hence, an attempted alteration is detectable either under ordinary light by the change in visible color or under ultraviolet light by the change in the fluorescent intensity.

Description

BACKGROUND OF THE INVENTION

The safety inks and documents disclosed herein are improvements over those shown in the U.S. Pat. Nos. to Guertin No. 3,088,841 and No. 3,400,003, both of which are assigned to the assignee of the present application. Guertin U.S. Pat. No. 3,088,841 discloses a printed document having adjacent background areas printed in different inks of the same color. One of the inks is bleachable and soluble in water and insoluble in the lower alcohols and lower ketones. The other ink is soluble only in the lower alcohols and lower ketones and is insoluble in water and unbleachable. Hence, the two areas react differently to alteration attempts involving either bleaching or solution in water or in the lower alcohols and lower ketones. However, any such alteration attempt produces a color contrast between the two areas, which makes the attempted alteration readily detectable visually.

Guertin U.S. Pat. No. 3,400,003, shows a document which is printed with two superimposed background patterns, of different colors, each composed of fine lines or dots. One of the patterns is printed in ink whose coloring matter contains a component which is bleachable, and soluble in water and in the lower alcohols and ketones. The other pattern is printed in an ink which is nonbleachable and not soluble in water and the lower alcohols and lower ketones. Again, any attempt to alter the document by bleaching or solution produces a color contrast.

BRIEF SUMMARY OF THE INVENTION

The present invention is an improvement on the safety inks and documents described in the Guertin patents mentioned above. According to the present invention, the background, which may be either an even color or an array of elements such as lines or dots, is printed in an ink whose coloring matter includes a dye which is bleachable and soluble in water and the lower alcohols and ketones, and a fluorescent pigment which is not bleachable, insoluble in water, and no more than very slightly soluble in the lower alcohols and ketones, but which is at least partly removed by an attempted erasure.

A document in accordance with the present invention may include two sets of background elements printed in adjacent areas in the same color. Alternatively, the document may include two superimposed sets of background elements printed in different colors.

However, the present invention does not require more than a single set of background elements, or a single even background color, printed in a single ink.

DETAILED DESCRIPTION

This invention relates to safety papers, ie., printed documents, such as negotiable instruments, which are adapted for the insertion of names, amounts, etc., either by hand, by typewriter or other mechanical devices and which are sensitive to attempts to alter inserted names, amounts, etc. The invention includes both inks designed to give the required sensitivity and having the characteristics necessary for such documents, and the documents printed with such inks. By sensitivity to attempted alteration is meant that an attempt to alter the printed document results in an observable change in the appearance of the document so as to alert a person receiving it to the fact that the document has been altered.

Documents of value are most commonly written upon in ink. The inks which are commonly used to write on documents of value may be classified either as conventional inks, ball point pen inks, or transfer sheet inks. Conventional inks are water solutions of either a dye, typically an aniline dye, or a ferrous salts which oxidizes to a ferric salt after writing, or combinations of both a salt and a dye.

The techniques of eradication of conventional inks were established many years ago. Where the dried ink was water soluble, such techniques simply involved the use of water as a solvent (socalled washable ink). Where the dried ink was not water soluble, the eradication techniques employed some type of bleaching reaction. The bleaching solutions (ink eradicators) for such inks are commonly sold.

A ball point pen ink is typically relatively stiff and heavy and may consist of one of the higher glycols as a vehicle, with an aniline dye for coloring material. Many of the ball point pen inks cannot be eradicated either by the use of water as a solvent or by the bleaching method.

While the details of all processes which might eradicate ball point pen inks are unknown, it has been determined that all processes so far known involve the use, at some stage of the process, of a solvent selected from the lower alcohols or lower ketones. By "lower" is meant that the number of carbon atoms in the particular alcohol or ketone is not greater than 8.

There have been recognized in the past two general techniques of eradication which may be classified as "line" eradication and "sheet" eradication. Line eradication involves the application of eradicating solution only to the particular line or lines to be eradicated. In sheet eradication, the entire sheet or document is immersed in the solvent or other agent used. The line eradication technique is the one most frequently employed in connection with conventional inks. It has been determined that the ball point pen inks require, in all the known processes, the sheet eradication technique.

It is also known that time is very important in the ball point ink eradication techniques. To be successful, the eradication must be completed within a relatively short time, of the order of 30 seconds. It the eradication has not been completed in that time, then the solvent may start to spread the ball point ink into the paper, thereby frustrating the attempted eradication.

Transfer sheet ink is used herein as a generic term to describe the materials employed on transfer sheets to produce a mark on an underlying sheet when the overlying sheet is written or typewritten upon. The term transfer sheet includes typewriter ribbons, carbon paper, "carbonless" carbon paper and any other sheet, usually employing a coated under surface, which is sensitive to localized pressure on the top of the overlying sheet to make a mark on the underlying sheet. The term transfer sheet ink is intended to include those materials which are latent in that there is no observable color on the sheet or on the underlying sheet until after the writing is applied.

Most transfer sheet inks may be described as either solvent types, in which the coloring matter is dissolved in material analogous to those used in the ball point pen inks, or wax types, in which the coloring material is carried by a wax vehicle, whether in solution or by simply mixing it with the wax vehicle.

Transfer sheet inks and the techniques for eradicating them, are of many different types. Some such inks are water soluble. Some are soluble in the lower alcohols or in the lower ketones or both. Some are bleachable. Some can be removed only by mechanical erasure.

The inks of the present invention produce an observable indication that an attempt has been made to alter written material on a document, whether that attempt was made by a solution technique, by bleaching, or by mechanical erasure.

Safety papers prepared in accordance with the invention have printed matter thereon, which is changed in color and in its fluorescent intensity by the techniques presently known for eradicating ball point pen ink. Typically, the printed matter so changed consists of a background of closely spaced fine lines, which may appear in any suitable configuration of characters, words, geometric figures, etc. The ink in which at least some of the printed patterns of the background appear should be soluble in organic solvent selected from the class having not more than 8 carbon atoms and consisting of the lower alcohols and lower ketones. There are two principal reasons for so limiting the class of organic solvents. One reason is that the alcohol and ketones as defined above are the ones most available commercially, and hence most likely to be used by a person attempting to alter a document. Another reason is that the higher ketones and alcohols do not act rapidly enough as solvents, and spread the ink into the paper instead of carrying it away. Consequently, a person seeking to alter such a document is frustrated if he attempts to use any of the higher alcohols or ketones.

Where more than one ink is used, the two inks must be compatible if a single impression printing process is to be employed. At least one of the inks must include a coloring matter component soluble in the lower alcohols and lower ketones, and a fluorescent pigment which is insoluble in water and has only a very low solubility in the lower ketones and lower alcohols.

The ink components may or may not be soluble in water, as desired. Typically, it is desired that the ink components which are soluble in the lower alcohols and lower ketones be also soluble in water. However, in some cases, printed documents may be exposed for long periods of time to the air in humid climates. In those cases, it is essential that the ink components employed should not be so water soluble that high humidity will make it start to run and destroy the pattern.

VEHICLE

The vehicle is the one described in U.S. Pat. No. 3,400,003, which is suitable from the standpoint of being miscible with the various coloring matters employed in inks manufactured according to the invention and which is also soluble in water and in the lower alcohols and ketones. This vehicle consists essentially of about 20% glycerine, about 64% sorbitol and about 16% water. These percentages are by weight. The proportion of glycerine employed in this vehicle may vary from about 10% to about 30%. If the proportion of glycerine is reduced below about 10%, tendencies to crystallize are observed. If the proportion of glycerine is increased above about 30%, the consistency of the vehicle becomes too thin for proper operation on conventional printing presses. The relative proportions of sorbitol and water should remain about the same (i.e. about 80% by weight of the material other than glycerine should be sorbitol and about 20% water).

Printing inks containing this vehicle perform satisfactorily on the printing press and are stable during printing and after being applied to the paper by the printing press. The resulting printed lines support writing by all the usual writing media without noticeable "bleed" and "feather" of the written line. Additionally, the resulting printed material is stable to handling during use and does not tend to change in color and effectively responds in the intended to fraudulent manipulation of the written material to create a noticeable change in the appearance of the document.

The documents printed with the inks and in accordance with the techniques of the Guertin patents mentioned above depend solely upon changes in color of the background elements to show that an attempt has been made to alter the writting material placed on the document. It has been discovered that in some cases, as for example, where an alteration is carefully performed and new writting is placed on the document in wide lines which cover the alteration, it may be difficult to observe the attempted alteration by observing change in color alone.

COLORING MATTER

It is therefore now proposed to use a fluorescent pigment in the ink, in such a manner that a document which has been subject to an attempted alteration will show a change in intensity of the fluorescence, in addition to the change in color under normal light. The change may be either an increase or decrease in fluorescent intensity in those areas where the alteration technique has been applied. In either event, when the document is viewed in ultraviolet light, the generally even tone of the pattern of background elements will be interrupted, in each location where an alteration has been attempted, by either intensified fluorescence or lessened fluorescence, depending upon the particular type of alteration technique which has been employed. The pigment selected should be non-bleachable, insoluble in water, and no more than very slightly soluble in the lower alcohols and lower ketones. A substance is defined as "very slightly soluble" by Hackh's Chemical Dictionary, if it requires from 1,000 to 10,000 parts of solvent to dissolve one part of the substance. A substance is defined by the same authority as "insoluble" if it requires more than 10,000 parts of solvent to dissolve one part of the substance.

If the technique employed has been one involving a solution or bleaching, then a part of the solution sensitive dye or bleaching sensitive dye will have been removed, but the fluorescent pigment will not have been removed. Since the dye tends to mask the pigment, there will be a resulting increase in fluorescent intensity in any area where a solution or bleaching technique has been applied. This intensified fluorescence will be readily visible if the document in question is viewed under an ultraviolet light.

If a line eradication technique has been employed, then the areas which were subjected to the eradicating solution will present a contrast to the other areas of the background. This contrast will be observable in visible light as a color contrast and will also be observable in ultraviolet light as a contrast between two areas of different fluorescent intensity, i.e., the eradicated areas will be brighter than the areas where no eradicating solution has been used.

If a sheet eradicating technique has been employed, then there will be no areas of contrast in the background visible on the face of the document, either in natural light or ultraviolet light. On the other hand, the entire background of the document will be changed in color. This color change should be readily noticeable under natural light. Under ultraviolet light, the entire document will fluoresce more intensely than would be the case if no eradication had been attempted.

The foregoing statements about the appearance of documents subjected to sheet eradication techniques are applicable to documents where backgrounds are printed in a single ink. Where the background is printed in different ink on different areas, as in the Guertin U.S. Pat. No. 3,088,841, the sheet eradication technique will bring out the color differences in those areas and will readily appear as an observable color contrast under natural light.

If an attempt is made to alter the writing on a document by erasure, i.e., by mechanically removing the deposit of ink left by the writing, then some of the fluorescent pigment is also necessarily removed ty the same operation, so that the fluorescence in the altered area is reduced.

Ultraviolet viewers are in common use by bank tellers, cashiers, and the like, so that a person accepting such a document can readily make a check of its validity by placing it under an ultraviolet light. This test can confirm a suspicion that a particular document has been altered, in those instances where a visual inspection gives only borderline results. Furthermore, it can detect some alterations which are not observable by a visual test.

EXAMPLE

The ink may consist essentially of the vehicle described above and coloring matter including a fluorescent pigment such as Resoform Fluorescent Yellow (Pigment Yellow No. 101, C.I. No. 48052, GAF Corp.) which may be 70.6 by weight of the coloring matter and a mixture of dyes including:

% of coloring matter by weight Acid Blue, C.I. No. 42755 6.0 Croceine Acid Red, E.I. No. 27290, 9.3 Tartrazine C Acid Yellow No. 23, C.I. No. 19140 12.0 Fuschine S.B.P. Basic Violet No. 14, C.I. No. 42510 2.1

All of these dyes are soluble in water and soluble in lower alcohols and ketones.

The C.I. numbers above are Color Index numbers of the American Association of Textile Chemists and Colorists, P.O. Box 12,2215, Research Triangle Park, N.C. 27,709, The Colour Index containing these numbers is published by Society of Dyeists and Colourists, P.O. Box 244, 82 Grattan Road, Bradford, Yorkshire, England.

The particular pigment described above is not bleachable and is insoluble in water and in the lower alcohols and ketones.

Claims

I claim:

1. A printing ink consisting essentially of coloring matter and a vehicle soluble in water and lower alcohols and lower ketones, said vehicle consisting essentially of glycerine, sorbitol and water, the glycerine being present in an amount in the range 10-30% by weight based on said vehicle, the remaining percentages of sorbitol and water having a weight ratio of about 4:1, said coloring matter including a dye soluble in lower alcohols and lower ketones wherein said lower alcohols and said lower ketones contain not more than 8 carbon atoms per molecule, and a fluorescent pigment which is non-bleachable, insoluble in water and no more than very slightly soluble in said lower alcohols and lower ketones.

2. A printed document comprising:

1. an area adapted to be writted upon and sensitive to attempted alteration of written material thereon by either solution, bleaching or erasure;

2. said area having a background of printed elements including a pattern printed in an ink consisting essentially of coloring matter and a vehicle soluble in water and lower alcohols and lower ketones;

a. said vehicle consisting essentially of glycerine, sorbitol, and water, the glycerine being present in an amount in the range 10-30% by weight based on said vehicle, the remaining percentages of sorbitol and water having a weight ratio of about 4:1;

b. said color matter including:

i. a dye soluble in lower alcohols and lower ketones, wherein said lower alcohols and said lower ketones contain not more than eight carbon atoms per molecule, said dye being bleachable and soluble in water, said dye being at least partly removed by solution or bleaching, and thereby changing the color of the background in response to attempted alteration of written material by solution or bleaching techniques; and

ii. a fluorescent pigment which is non-bleachable, insoluble in water, and no more than very slightly soluble in said lower alcohols and lower ketones, said pigment having its fluorescence enhanced by removal of the dye during solution or bleaching, and being at least partly removed by erasure, thereby changing the color and flourescent intensity of the background, when viewed under ultraviolet light, in response to attempted alteration of written material by erasure.