FR2710768A1 - Document, especially label, including invisible indications, especially a bar code, which can be revealed by exposure to ultraviolet light - Google Patents

Abstract

This document comprises: - a substrate (1) made of a material which is essentially luminescent under ultraviolet light, especially a common type of white paper - a layer (3) which is essentially non-luminescent under ultraviolet light, applied selectively to this substrate so as to cover almost the entire surface with the exception of predetermined areas (4) defining, in reserve, the said invisible indications, the thickness and the nature of this layer being chosen so as partially or totally to occult the luminescence of the substrate, and - the said visible indications (5), printed on the support thus covered.

Description

Document, in particular a label, comprising
invisible indications, in particular a bar code,
revealable by exposure to ultraviolet light
The invention relates to a method of manufacturing a document bearing directly visible printed indications and invisible indications, which can only be revealed by exposure to ultraviolet light.

 The invention will be particularly described in the context of label printing and in that where the invisible indications are bar codes, but the invention is however in no way limited to these particular cases of application, as is will further specify below.

 In the case, for example, of labels for pharmaceutical products, it may be desirable to affix a bar code on the label allowing, at different points in the automatic packaging and packaging chain, to verify that the correct label has been been affixed to the correct product. The label must therefore include a double marking, namely a clear marking, readable by the user or the doctor, and a coded marking, readable by the machine, the two markings being carried out on the same support.

 Most of the time, the machine-readable marking consists of a barcode printed in black ink either on the label itself or on the adhesive. These solutions are however unsatisfactory from the point of view of appearance and, moreover, the printing of the bar code on the label itself takes up space on a label which is already very often of small size as to printing on the adhesive is relatively expensive.

 We have already tried to print bar codes that are invisible in normal light (therefore not bothersome for the user to read the information in plain text), but which may, by using an ink containing fluorescent pigments, present a phenomenon luminescence when exposed to ultraviolet light; the codes can then be easily read by an automatic reader with a photocell, of a type known as such.

 However, in the attempts of the prior art in this direction, the luminescent inks or varnishes used to print the bar code have revealed poor repeatability and fairly rapid aging, not allowing reliable implementation on an industrial scale. .

 One of the aims of the present invention is to overcome these drawbacks, by proposing a method and a product having a very high consistency of photometric qualities and an almost absence of aging, thus allowing perfectly reliable operation on automatic packaging lines. , in particular for packaging pharmaceutical products.

 To this end, the method of the invention comprises the steps consisting in: (a) taking a substrate of a material essentially luminescent in ultraviolet light; (b) selectively applying a substantially non-luminescent layer in ultraviolet light to this substrate, so as to cover almost the entire surface thereof with the exception of predetermined zones defining, in reserve, said invisible indications, the thickness and the nature of this layer being chosen so as to partially or totally obscure the luminescence of the substrate; and (c) print said visible indications on the support thus covered.

 Optionally, there may be provided, before step (b), a step of pretreatment of the substrate consisting in applying thereto a uniform layer of an agent for adjusting the degree of luminescence.

 The invention also covers, as a new product, a document bearing directly visible printed indications and invisible indications, revealable only by exposure to ultraviolet light, comprising: a substrate made of a material essentially luminescent in ultraviolet light; an essentially non-luminescent layer in ultraviolet light, applied selectively to this substrate so as to cover almost the entire surface thereof with the exception of predetermined zones defining, in reserve, said invisible indications, the thickness and the nature of this layer being chosen so as to partially or totally obscure the luminescence of the substrate; and said visible indications, printed on the support thus covered.

 Very advantageously, the substrate is a substrate which is not pretreated with a material which is itself luminescent, such as white paper of common type. Optionally, there may be provided between the substrate and the essentially non-luminescent layer, a uniform layer of an agent for adjusting the degree of luminescence.

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Other characteristics and advantages of the invention will appear on reading the detailed description below, made with reference to the accompanying drawings.

 Figure 1 is a sectional view, along I-I of Figure 2, of a label made according to the teachings of the invention.

 Figure 2 is a plan view of the same label.

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The figures illustrate a label produced according to the teachings of the invention. The reference 1 designates the substrate of the label, typically a paper of current commercial quality such as for example a paper of vellum type, which is luminescent like almost all the papers of this type taking into account the incorporation of brighteners. optics during the production of pulp. The "natural" luminescence of these substrates is very high, often close to 9 to 10 on the Ciba scale for white papers. The luminescence of the paper can possibly be adjusted to the chosen value (around 7 on the Ciba scale) by application of a first layer 2 of covering ink (which can for example be of the same type as that which will be used for the 'next step, but applied to a lesser thickness).

A layer 3 of covering ink is then selectively applied to the substrate, for example a white brand ink
Aarberg, of luminescence notably lower than that, possibly adjusted, of the substrate 1, for example a luminescence of the gold of 4 on the Ciba scale, leaving in reserve, in 4, the bars of the code.

 The plain text is then printed with an ink visible at 5, in a conventional manner, on the covering ink layer 3. This visible ink is typically an opaque ink, for example a black ink.

 It is thus seen that, contrary to current attempts which all sought to use a luminescent ink (with the aforementioned drawbacks of dispersion of the characteristics and of rapid aging), the invention does not use any luminescent ink but is content to use the pre-existing luminescence of the substrate itself by obscuring (partially or totally) it around the code in order to make it readable in ultraviolet light. Of course, the invention is thus limited to luminescent substrates, which most often means white substrates, but this restriction is in practice not very troublesome.

 This technique has many advantages.

 First, the luminescence of the substrate, which is generally extremely stable over time (much more in any case than that of varnishes or luminescent inks) provides excellent stability over time.

 Secondly, it is possible to make all the desired adjustments of the contrast between the code bars and the background and thus to optimally adapt this contrast to the reading device used, since the covering ink layer 3 can be chosen (by its thickness and / or its nature) to only partially eliminate, if desired, the luminescence of the substrate (for example from 9 to 0, or to 1 on the Ciba scale).

 Of course, the present invention is not limited to the registration of a bar code, but can be extended to the printing of any text or luminescent inscription.

 By adapting the formulation of inks 3 and 5, it can also be implemented with any printing technology (screen printing, offset, gravure printing, etc.).

 The invention can moreover be generalized to all cases in which it is desired to make an invisible impression on a document with good resistance to aging, improved resolution and better control of contrast than existing solutions based on luminescent inks.

Claims (6)

 1. A process for manufacturing a document, in particular a label, comprising directly visible printed indications and invisible indications, in particular a bar code, revealable by exposure to ultraviolet light, comprising the steps consisting in:  (a) taking a substrate (1) of an essentially lumi material  descending in ultraviolet light,  (b) selectively applying a layer (3) to this substrate  essentially non-luminescent in ultraviolet light,  so as to cover almost the entire surface ex  ception of predetermined zones (4) defining, in reserve,  the said invisible indications, the thickness and the nature of this  the layer being chosen so as to partially obscure or  totally luminescence of the substrate, and  (c) print the said indications on the support thus covered  visible (5).  2. The method of claim 1, comprising, before step (b), a step of pretreatment of the substrate consisting in applying thereto a uniform layer (2) of an agent for adjusting the degree of luminescence.  3. A document, in particular a label, comprising directly visible printed indications and invisible indications, in particular a bar code, revealable by exposure to ultraviolet light, comprising:  - a substrate (1) made of an essentially luminescent material  in ultraviolet light,  - a layer (3) essentially non-luminescent in light  ultraviolet, applied selectively on this substrate of  so as to cover almost the entire surface except  tion of predetermined zones (4) defining, in reserve, the  tell invisible indications, the thickness and the nature of this  layer being chosen so as to partially obscure or  totally luminescence of the substrate, and  - said visible indications (5), printed on the support  thus covered.  4. The document of claim 3, wherein the substrate is a substrate not pretreated with a material by itself luminescent.  5. The document of claim 4, wherein the substrate not pretreated by itself luminescent material is white paper of common type.  6. The document of claim 3, comprising, between the substrate and the essentially non-luminescent layer, a uniform layer (2) of an agent for adjusting the degree of luminescence.