GB2200662A - Generating bar codes in recording material - Google Patents

Abstract

Bar codes are generated within sheet material including a colour developer, by reaction with a colour former formulation released from pressure sensitive micro-capsules, using: (a) one or more colour formers in the formulation selected to give absorption and hence contrast in readout under illumination at 633 and 900 nm; (b) high concentrations of these colour formers in the micro-capsules, namely 1 to 6 weight %; advantageously 1.5 to 2.5 weight %, of the formulation. The sheet material may be self contained, with the colour developer and micro-capsules present in the same sheet, or part of a copy set in which the colour developer and micro-capsules are in separate sheets. The bar codes may be used in retail outlets for labeling of goods, or for stock control in manufacturing processes.

Description

RECORD MATERIAL The invention relates to the production of bar codes.

Bar codes are in wide use for data storage and computerised data management. Data is stored as a series of bars and spaces and read by optical scanning.

In principle, scanning can be at any wavelength but in practice narrow band-width systems work at 633 nm or 900 nm, corresponding to two established sources.

The 633 nm reader uses a helium-neon laser source giving visible red light and the 900 nm reader a gallium arsenide solid-state source operating in the infra red. Practical bar codes have therefore to absorb at these wavelengths, though there are also broad-band readers based on white light illumination with detectors operating at suitable wavelengths.

Other desiderata are adequate definition, adequate contrast between bars and spaces and adequate intensity of absorption.

The above desiderata are quite difficult to satisfy to give reliable readout. The difficulty is increased when, as in the present invention, it is sought to develop pressure sensitive copy systems that will give successful bar codes. Nevertheless we have seen that the successful use of such systems will be advantageous. The bar codes produced, being within rather than on the surface of the carrier material like printed codes, will be difficult to damage physically or by smudging in handling. They will also not be subject to degradation by further colour development like thermally developed bar codes which, further, cannot give multiple copies.

There are various prior proposals for generating bar codes by methods other than straightforward printing, for example Ricoh Japanese 58-117766 = Koka; 60-8364 concerning heat sensitive material, and proposals in two European specifications Nos. 0 124 360A and 0 174 868A (Kureha), concerning encapsulated dye or pigment/adhesive compositions. They do not however disclose the use of a system generating the bar code image by reaction within the material that is to carry it, and we believe this is new.

Pressure sensitive copy systems are in themselves well known, and typically consist of a top (CB) sheet coated on its back with one part of an image generating system, a bottom (CF) sheet coated on its front with the complementary part of the system, and optionally one or more intermediate (CB) sheets coated correspondingly on both front and back. The coatings are such that on image-wise application of pressure, material is transferred from one sheet to the next and reaction generating the image takes place in that sheet. Usually a 'colour former' is contained in microcapsules that are broken by the imaging pressure which, further, transfers the colour former to react with an acidic clay or other 'colour developer' present on the facing sheet . There are also reverse transfer and self-contained systems.It is these microcapsule based systems that the present invention uses.

We have found that to apply such systems in the generation of bar codes it is necessary to employ (a) One or more specifically selected colour formers to give absorption and hence contrast under illumination at 633 and 900 nm; (b) High concentrations of these colour formers in the micro-capsules, namely 1 to 6 weight %, preferably 1.5 to 2.5 weight %, related to the encapsulated formulation; and the invention accordingly lies in a method of generating bar codes using pressure sensitive systems as set out, and in the bar codes produced.

The specified concentrations of the colour formers relate to the usual coating mix application rates of 7 to 8 g/m2, giving a corresponding application rate of the colour formers of O.04 to 0.26 g/m2, preferably 0.06 to 0.12 g/m2.

The micro-capsules used and the formulation overall are designed to secure maximum colour former transfer (in a transfer system) in a way that will be known per se to those skilled in the art, and generally for good image contrast, and to the same end the high imaging pressures available from industrial printers are desirably used in producing the bar codes themselves.

For the colour formers themselves there has been development over approximately the last decade of materials suited to the required wavelengths, primarily in connection with OCR-compatible copy papers, and for example a suitable colour-former formulation contains one or both of: 3,6-bis(dimethylamino)fluorene-9-spiro-3'-(6' -dimethylamino)phthalide ('GllB') and 3,3-bis[2,2-bis(4-dimethylaminophenyl )ethenyl] -4,5,6,7-tetrachlorophthalide ('MG1') These colour formers are satisfactory on clay colour developers, even though in general such colour developers cause a blue shift in the absorption peak of a colour former, counterindicative to a bar code application.

The formulations generally need to be suited not only to narrow band scanners but also to give an acceptable visual image, for example for possible white light scanning but more particularly for normal use of the copy sets for presentation of eye-readable information or for example for use with optical character recognition (OCR) equipment. Accordingly theabove colour formers may be used with further colour formers to build up for example a quickly developed and fade and hue-shift resistant black image.

The invention is described herein in t-erms of copy sets where the base material is paper and the colour developer is an acidic clay, but there is no restriction to these particular instances. Nor there is particular restriction to the end use of the bar codes. They may be required for example for stock control in manufacturing processes, when otherwise conventional copy paper sets with three or more copies can be prepared. They may also be used in the bar-code labelling of goods for retail outlets where the codes, at least as to one copy, will be required on selfadhesive labels. In such cases the labels with their release paper backing sheet will conveniently form the CF sheet of the set.

The following examples illustrate the application of the invention, encapsulatable formulations being made up as follows: Example I Component Weight % A. MG1 1.5 B. Mixture of PSDV Pergascript I-5R OY 80 SRB 635 Pergascript I-2R

4.9 C. Alkylnaphthalene solvent to 100% Example II Component Weight % A. G 118 B. Mixture of PSDV Pergascript I-5R OY 80 SRB 635 Pergascript I-2R

1.5 4.9 C.Alkylnaphthalene solvent to 100% These formulations give a black visual image and also provide the red/infra red absorption necessary for reading of a bar code by the established scanners. PSDV is a fluoran colour former giving a red or vermillion image; Pergascript I-5R is another fluoran colour former giving an orange or orange red image; OY 80 gives a yellow-orange; the MG1 or G 118 as to their visual image give a green; the SRB gives a blue colour, similar to that of CVL (crystal violet lactone), slow in development but fade resistant; 635 is a spirobipyran colour former; and Pergascript I-2R is CVL, which gives a quick development of a blue colour, shifting later to greenish and less intense.

This formulation is encapsulated in a conventional manner, for example in a coacervation medium giving gelatin capsules, and the resulting emulsion coated on the back of CB and CFB sheets in the form of a coating mix made up buy including cellulose floc as a stilt and starch as binder with water to give a mix solids of 20%, coatweight of 7 to 8 + 2 equivalent to approximately 4.9 to 5.6 +;2 of colour former solution. The colour developer, used on the face of the CFB sheets and on a CF sheet used to complete the set is a conventional CF coating from a mix based on acid clay ('silton'), kaolin and styrene butadiene latex binder to give a dry coatweight of 8 9tun2.

The sheets are made up into sets of CB/CFB/CFB/CF and imaged with bar codes using an industrial printer.

They give 80% to 85% first time readout in tests comparable to supermarket checkout conditions, and negligible readout failure.

Appendix The trade names of the colour formers, other than MG1 and G 118 given above, represent: PSDV 2-chloro-6-diethylamino-3-methylfluoran Perg. I-5R 3-ethyhexylaminofluoran OY 80 3-chloro-6-cyclohexylaminofluoran SRB N-butylcarbazol-4-yl-bis (4-N-methyl-N- phenylaminophenyl)methane 635 7-dibenzylamino-3-isopropyl-2,2 '-spirobi [2H-chromene Perg. I-2R 3,3-bis(4-dimethylaminophenyl)-6 dimethylaminophthalide (CVL)

Claims (5)

1. CLAIMS 1. Generation of bar codes from pressure sensitive microcapsule based systems using: (a) One or more colour formers selected to give absorption and hence contrast under illumination at 633 and 900 nm; (b) High concentrations of these colour formers in the micro-capsules, namely 1 to 6 weight %, preferably 1.5 to 2.5 weight %, related to the encapsulated formulation; and the bar codes produced.
2. 2. The generation of bar codes according to claim 1, where the specified concentrations of the colour formers relate to the usual coating mix application rates of 2 7 to 8 g/m , giving a corresponding application rate of the colour formers of 0.04 to 0.26 g/m , preferably 2 0.06 to 0.12 g/m
3. 3. Generation of bar codes according to claims 1 or 2 wherein the high imaging pressures available from industrial printers are used in producing the bar codes.
4. 4. Generation of bar codes according to claims 1, 2 or 3 using a colour-former formulation of one or both of: 3,6-bis(dimethylamino)fluorene-9-spiro-3'-(6' -dimethylamino)phthalide ('G118') and 3,3-bis[2,2-bis(4-dimethylaminophenyl)ethenyl] -4,5,6,7-tetrachlorophthalide ('MGl') on clay or other colour developers.
5. 5. Generation of bar codes according to any preceding claim, wherein the above colour formers are used with further colour formers to build up a quickly developed and fade and hue-shift resistant black image.