WO2000056553A1

WO2000056553A1 - Latent halftone image

Info

Publication number: WO2000056553A1
Application number: PCT/EP2000/002387
Authority: WO
Inventors: Raimund Heinrich Behrend
Original assignee: Philip Morris Products S.A.
Priority date: 1999-03-22
Filing date: 2000-03-17
Publication date: 2000-09-28
Also published as: CH695375A8; RU2238189C2; EP1038690A1; AU4395700A; CH695375A5; NO20014583L; NO20014583D0

Abstract

The invention relates to a latent halftone image on a carrier that shows an especially multicolor reversible image upon the exposure to UV light, said halftone image preferably containing a plurality of UV-luminescent dyes. The invention also relates to a method for producing such an image and its use in advertising.

Description

Latent raster print image

The present invention relates to a latent raster print image on a carrier, which reversibly shows a single or multi-colored image, to processes for its production and its use in advertising or for advertising and promotional purposes.

There is a need to store items e.g. Sales products and their packaging, so that the labeling is not visible to the viewer at all times, but only under certain circumstances. Such latent labeling is of interest, for example, for the promotion of products with pictures and image motifs, because this means e.g. Surprising and particularly appealing optical effects that can be used for advertising the labeled products.

WO 88/01288 describes a method for identifying a substrate for security purposes - for example to protect bank cards against counterfeiting - in which a photochromic color is first applied to the substrate (ie a color which is colorless in daylight and is only affected) of UV light reversibly discolored) printed and then a protective layer, for example made of plasticized PVC, is applied over the color layer. The photochromic color is preferably applied by a screen printing process. WO 88/01288 does not describe the labeling of products with complex images and image motifs, for example for advertising purposes.

Another possibility of securing security-sensitive objects such as check cards with the aid of a latent identification is described in EP-A-0 279 526. By printing on the substrate with two different line bundles which cross one another at selected locations, a moiré pattern is generated which is difficult to fake. The printing inks used can include contain a UV-fluorescent dye that only becomes visible when exposed to UV light. The use for advertising purposes is not disclosed here either.

The object of the present invention is to provide a product which allows objects to be equipped with latent monochrome or multicolored, even complex, images and image motifs for advertising purposes.

The task is solved by a latent raster print image which is on a carrier and which is not (or at most only vaguely) visible to the human eye when exposed to visible light and / or daylight and which only becomes visible under the influence of UV light. or multi-colored picture shows. The appearance of the image is reversible, ie as soon as there is no more UV light, the image disappears, which becomes visible again after UV light is shone in again. It is preferred that this colored image is multicolored. By applying the latent image with a raster printing process, in contrast to the prior art, complex images and image motifs, in particular for advertising purposes, can be printed on a carrier. Colored, also multicolored, raster print images have been known for a long time. They are printed according to the screening methods commonly used in the conventional printing processes (see, for example, HM Speirs, "Introduction to Printing Technology", British Printing Industries Federation, 4th edition, 1992, chapter 2) (see, for example, HM Speirs, "Introduction to Printing Technology", Chapter 5, in particular pp. 61-68), whereby several differently colored layers of pressure dots are applied next to and on top of one another on a carrier and the resulting color mixture and intensity variation produces an image effect. The raster print images produced in this way are readily recognizable to the human eye, ie they show black-and-white or monochrome or multicolor images under the action of visible light (for example in daylight), ie light in a wavelength range from approximately 400 to approximately 700 nm.

Furthermore, color applications are known which do not show colored images under the influence of visible light, but they do, however, if they are exposed to UV light in a wavelength range from approximately 190 to approximately 400 nm. Such pictures are called "latent pictures" because they are not recognizable under normal lighting conditions and only become visible as pictures if they are specifically stimulated. These color applications contain a so-called luminescent dye. A luminescent dye is in an energetically excited state; upon exposure to radiation, for example, the luminescent dye changes into a state of lower energy, the excess energy being emitted by emission of light quanta of a certain wavelength. If this emission wavelength is in the visible range, the radiation emitted can be perceived by the human eye as colored.

Such latent luminescent color applications can be used, for example, to identify people. In entertainment venues, for example, it is customary to apply a stamp of the latent luminescent color on the skin (e.g. on the hand area). This application of color is not visible under "normal" light, but it is visible under UV light, so that visitors to the entertainment venue can easily check whether they have paid the entrance fee and the latent color has been applied to them by briefly applying the area of skin under one UV lamp is held. In this way, it can also be ensured in the case of elections that the respective voter votes only once.

So far, these color applications have only been used in one color, i.e. the viewer perceives only a monochromatic image when exposed to UV light. It is also not known to use them for advertising purposes.

DE 32 16 568 A1 also discloses a photographic recording method in which a photographic recording material which contains at least one layer of photosensitive silver halide and at least one luminescent compound is exposed imagewise and developed to produce a latent luminescent image and the image information contained in the latent luminescence image is photo-selectively scanned by means of a luminescence spectroscopic method and electronically recorded in the form of monochrome luminescence signals; the process delivers single and multi-color images. This recording process does not provide a raster print image and is not used for the latent identification of objects with colored images.

The raster print image according to the invention usually contains at least one dye luminescent under UV light. Dyes are used as luminescent dyes, which are first converted into an energetically excited state by the action of UV light, in order to then also be stimulated by the action of UV radiation to emit light quanta, the light quanta with one in the visible Wavelength range can be emitted. The human eye then only takes that color corresponding to the wavelength of the emitted light quantum is true only when the raster print image is exposed to UV light.

The dyes luminescent under UV light are known and commercially available compounds (see Römpp Lexicon Lacquers and Printing Inks, 1998, p. 355 keyword "fluorescent dyes"). They are, for example, those described in WO 88/01288 as photochromic compounds. Other suitable dyes that are luminescent under UV light include in WO 98/32799, DE-A-195 12 773 and DE-A-196 51 712. The printing inks containing luminescent dyes can be, for example, the printing inks from SICPA-AARBERG, Switzerland, with the name Aarberg INNOVA 62-LC (LumiColor).

They preferably show luminescence when exposed to UV radiation in a wavelength range from 240 nm to 380 nm, in particular at about 366 nm.

The halftone printing dots of the halftone printing image according to the invention preferably have 60 to 120 dots / cm, the number of dots in a given raster being independent of the size of the dots. By varying the raster pressure dot size, an optical modulation of the image impression is generated. If larger dots are plotted, they can touch their neighboring points, so that complete surface coverage can be achieved.

The use of additive color mixing methods (see, for example, ED Stiebner, "Bruckraann's Handbuch der Drucktechnik", Bruckmann, 5th edition, 1992, pp. 100-103; HM Speirs, "Introduction to Printing Technology", 4th edition, 1992 , Pp. 76-81) for the production of the raster print images according to the invention is particularly preferred before likewise possible subtractive color mixing processes if the carrier of the raster print image according to the invention is used for the subtractive driving is not sufficiently white. Based on the assumption that UV-influenced lighting situations occur in a predominantly dark environment, also in order to bring the effect of UV lighting to better effect (night clubs, entertainment venues, etc.), it must be expected that white is an essential component is often not available for (composite) multi-color raster print images produced after subtractive color mixing. This deficiency in white is overcome by the use of the additive color mixture for the generation of the multicolored raster print image. This method can be used wherever there is either no white light or no white radiation from the substrate used for printing. White paper or white cardboard, for example, only emits white light under UV lighting (ie when illuminated with a light that has no white component) if optical brighteners were used in the production of this carrier material. However, optical brighteners are often undesirable for environmental reasons. For example, they are largely banned for the manufacture of paper and cardboard used in the cigarette industry. The absence of this source of white light under UV conditions, which also applies to other possible carrier materials for the application of multicolored latent raster print images, for example polypropylene film, is taken into account by using the additive color mixture for the image structure. The darker the background, the better the print image according to the invention, produced by the additive process, can be seen. The raster print image according to the invention then has a blue, a red and a green and possibly another dye which is luminescent under UV light. Alternatively, a subtractive method is also possible, in which case the colors magenta (red), cyan (blue) and yellow and possibly black (for better contrast), which are luminescent under UV light, are applied. A prerequisite for the visibility of the images is either white light as a component of the irradiated Light or, under UV light, the presence of optical brighteners that reflect white.

The halftone printing images according to the invention can be made by any suitable printing process (see, for example, HM Speirs, "Introduction to Printing Technology", 4th edition, 1992, pp. 7-10), in particular by offset printing, lithographic printing, flexographic printing, high-pressure printing. or gravure process. To avoid disturbing moiré patterns, screen angulation is preferably used (see E. D. Stiebner, "Bruckmann's Handbuch der Drucktechnik", 5th edition, 1992, pp. 123-125).

The support for the halftone printed image can be made of any suitable material, preferably it consists for example of paper, cardboard, textiles or film or foil materials made of a natural or synthetic polymer (e.g. polypropylene). For example, the raster print image can be applied to polypropylene, as is usually used for the clear film of cigarette packs. The raster print image can either be on a separate support

(For example, a sticker, an adhesive film or a label) are applied, this carrier then being connected to the goods to be labeled. Or the raster print image is applied directly to the product, which is then the carrier, such as the outer one

Polypropylene wrapping, the paper or cardboard box or the inner liner of a cigarette packet, a postcard, a poster, a t-shirt or packaging in general, in particular gift or food packaging. The manufacturer can use a typical print image or logo, but also complex graphic designs for advertising purposes. Halftone printing dots from different layers can contain different dyes that are luminescent under UV light, so that a multicolored halftone printing image appears under the action of UV light. The use of raster print images according to the invention is particularly suitable in advertising. For example, conventional packaging, such as cigarette packs, can be printed with a raster print image according to the invention as described. This raster print image is not recognizable to the viewer in daylight or visible light. Only when exposed to UV light, for example in an entertainment venue, does a multicolored image become recognizable. Printing of so-called point-of-sales material, such as posters, is also possible.

Claims

Expectations

1. Latent raster print image on a carrier, which reversibly shows a single or multi-colored image when exposed to UV light.

2. Raster printed image according to claim 1, which contains at least one dye luminescent under UV light.

3. Raster printed image according to claim 1 or 2, wherein the image is multi-colored.

4. Raster printed image according to one of the preceding claims, which is produced by an additive color mixing process.

5. Raster printed image according to claim 4, which has a blue, a red and a green under UV light luminescent dye.

6. Raster printed image according to one of the preceding claims, wherein the printed image carrier consists of paper, cardboard, textiles or film or foil materials made of a natural or synthetic polymer.

7. Process for producing a raster print image that becomes reversibly visible under UV light by a raster print process.

8. The method according to claim 7, wherein printing inks which are UV-light are used according to subtractive and / or additive color mixing methods.

9. Use of a raster print image according to one of claims 1 to 6 for advertising or promotional purposes.