WO1986001750A1

WO1986001750A1 - Method for forming images by ultraviolet irradiation

Info

Publication number: WO1986001750A1
Application number: PCT/FR1985/000249
Authority: WO
Inventors: Pierre Le Cars
Original assignee: Pierre Le Cars
Priority date: 1984-09-17
Filing date: 1985-09-17
Publication date: 1986-03-27
Also published as: EP0194296A1

Abstract

Method for forming images by ultraviolet irradiation and products for the obtention of such images. According to the invention, there are deposited on an object a sublayer, and a transparent base including a fluorescent body in a proportion at the most equal to 5% by weight of the base. Application particularly to displays.

Description

METHOD FOR FORMING IMAGES BY ULTRAVIOLET IRRADIATION

The subject of the present invention is a method of forming images by irradiation with an ultraviolet source intended in particular, but not exclusively, for obtaining new aesthetic effects.

We know that objects do not have their own color and that the apparent color of an object results from the reflection of part of the spectrum of the irradiation source, the other part of the spectrum being absorbed by the object. .

We also know bodies which have the property of being fluorescent or luminescent, that is to say of transforming a received radiation into a radiation of longer wavelength and in particular of giving, by irradiation by a source. emitting outside the visible spectrum, ^" visible light. We know, in particular bodies which, by UV irradiation, that is to say by a source emitting in a spectrum whose frequencies are lower than 0.4 microns (such as 'an OOD lamp, allowing to select radiations in the near ultraviolet thanks to a black filter with nickel oxide, for example) constitute a visible secondary source. When the photons of the radiation strike the atoms of a fluorescent substance, there is absorption of the energy supplied and transformation thereof which is re-emitted with a lower frequency, that is to say with a wavelength greater than that of the incident radiation. , so-called fluorescent paints visible in both daylight and "black" light, resulting from a mixture of fluorescent pigments and a binder, constitute, by UV irradiation, a secondary source. But both in visible light and in Wood light, these paintings, the colors of which are limited to four or five, are aggressive and difficult to bear with the eye. They are also opaque, brittle and deteriorate by friction. Furthermore, it has already been proposed to use fluorescent bodies to identify and control paintings, works of art in patent FR-A- 1 456 784, or banknotes.

The object of the present invention is to develop the applications of fluorescent bodies by overcoming the drawbacks of known bodies and by making it possible to obtain practically any shade of color in ood light.

According to the present invention, the method for forming images by ultraviolet irradiation is characterized in that it consists in coating an object, a part of an object or a set of objects with a transparent support into which is introduced a solution of '' a fluorescent body in a proportion at most equal to 5% by weight of the support.

It is thus possible to obtain the fluorescence of tints or body colors which are not naturally fluorescent either by reflection if the UV source is arranged above the object, or by transmission if the object being itself transparent the UV source is arranged behind the object relative to the observer. The invention makes it possible to identify a much wider colorimetric range than the existing one and, possibly, to highlight fluorescent colors already existing, and, currently seventy shades are available instead of only five in the prior art.

The colors thus obtained show good resistance to light, mechanical resistance to friction, and to a pressure equivalent to 5000 bars, as well as chemical resistance to acids.

The present invention also relates to a display method combining the bodies obtained by the above method, characterized in that it consists in forming on the same support a first image sensitive to irradiation. by a light source emitting according to a first frequency spectrum and at least a second image, at least partially transparent with respect to the first spectrum and sensitive to at least one radiation of a radiation of c wavelength different from that of the first spectrum.

It is thus possible to obtain a visualization of absolute clarity in a dark area, although total black is not necessary, on the one hand and in an area lit by the

10 daylight, on the other hand.

Of course, the two images, primary and latent, juxtaposed or superimposed, can present common parts, that is to say that in a landscape certain details - _j _5 can belong to the primary image and others to the latent image. . But the two images can be perfectly independent of each other.

Colors can be applied on all supports

20 suitable, including transparent supports such as Altuglass (registered trademark).

To obtain the desired effect, one can either use an existing image, for example formed from conventional paints or inks, and cover this image with

25 polymer-fluorescent or luminescent compound mixture in solution, either producing the image using a mixture of conventional colored pigments, a polymer and fluorescent pigments. This result essentially results from the transparency effect created by the polymer layer which can be

30 adjust in thickness and fluorescence depending partly on the concentration of the solution in fluorescent pigments. The transparency of the support makes it possible to use only a small proportion of fluorescent pigments. For example, if we spread a layer of mixture on a canvas

35 painted in oil, this canvas irradiated by a UV source gives a very luminescent image. According to another characteristic of the invention, the transparent support consists of a vinyl or acrylic polymer soluble in water. The support + solution assembly can thus be extended over any surface or used in the liquid state. The fluorescent bodies used in solution can be, for example: fluorescein or autunite for the greens, esculin for the blues, fluorite for the mauves, auramine for the yellows, rhodamine for the roses, etc. .... Other transparent polyymers can also be used.

Other characteristics and advantages of the present invention will appear during the description which follows of particular embodiments, given only by way of nonlimiting examples.

The mixture is, for example, constituted by a polymethyl acrylate into which a plasticizer composed of an acrylic monomer in emulsion at 50% in water is introduced. ^'The pigment is formed, for example fluorescein diluted between 2 and 5% in water. It can also be constituted by a polymethacrylate with 3 or 4% ammonium, an acrylic acid neutralized with ammonia being added in a suitable proportion in the polymer. The fluorescent solution is then added to the polymer before application to the object to be covered.

Throughout the following description, the plastic particles are dispersed in a medium formed essentially of water; very small particles have a diameter between 0.05 and 5 u. Mention may first be made of polyvinyl acetates. The particles and their binder do not turn yellow and remain insensitive to aging. The film-forming properties turn out to be better at - 10 ° C, which allows significant fixation of all fluorescent substances. the film thus obtained has the characteristics of elasticity, transparency, good adhesion to lean background, insensitivity to freeze-thaw, sun, moon, rain ^', etc. The base or universal primai underlay consists of a base of pure acrylic resin with white pigments in dispersion. It allows the realization of universal adherent funds and suitable after drying in oil colors as well as in aqueous paints such as fluorescent acrylic colors, polymer colors, vinyl or others.

This undercoat has been specially studied for the preparation of alkaline materials such as concrete, cement or mortar, new siding, asbestos cement and all other materials with alkaline properties. The film of pure acrylate resin in dispersion is indeed an alkaline-resistant, excellent adhesion on this type of funds. It can also be used on canvas, non-woven, ecru cotton. It avoids the oxidation of fibers by linseed oil.

The fluorescent products are applied to the sublayer, which will be described below, by way of example.

EXAMPLE 1 BASE OF ETHYL POLYMETACRYLATE

Acrylic medium - based on dispersions of acrylate resins with the same chemical composition as the binder of acrylic paint.

This milky white medium is fluid, it is used as a thinner in acrylic and polymer colors for glazes. Also, by introducing in proportions of

2 ° / ooo to 20 ° / ooo fluorescent pigments such as those specified in the attached table. Transparent fluorescent colors are obtained. Some disappear in daylight or under incandescent lighting, only to appear under excitation of the W00D lamp. Properties and application:

- milky liquid becoming colorless, transparent and water resistant after drying.

- elastic film - gloss of paint

- physical drying, film formation by evaporation of water

- Thinner: water

- applies with brushes, paint spray guns, airbrushes or any other means

EXAMPLE 2 POLYMETACRYLATE METHYL BASE -

Medium gel - based on dispersed acrylate resins and stabilizers

A milky white aqueous gel which becomes colorless and transparent on drying. Elastic and water resistant film, mixing with acrylic and polymer colors. This gel increases the transparency and the brightness of the colors.

Also, by introducing in proportions of 2 ° / ooo to 20 ° / ooo fluorescent pigments as specified in the table, fluorescent colors with gel consistency are obtained which become completely transparent. Some disappear completely in daylight or incandescent artificial light to appear only under excitation of the 00D lamp.

Properties and applications: - pasty medium for acrylic and polymer color

- transparent and colorless

- fluorescent by introduction of fluorescent pigments

- fast drying

- water and weather resistant plastic film - does not yellow

- is used on a thin background

- can be used with a brush, a knife and screen printing.

- applies to all degreased substrates beforehand

- thinner: water The mixtures obtained as just exposed are deposited on an already painted support such as an oil paint on canvas.

EXAMPLE 3 COATING PASTE TO BE MODELED -

based, among other things, on normal or fluorescent pigments and fillers such as marble dust or glass microbeads finely distributed in a plastic solution in dispersion.

- white paste with water which looks like a coating which gives an opaque layer. It allows to give relief in relief - must be mixed with acrylic medium at a rate of 20 to 50% or medium gel at 50%

- this product can be applied on all materials

- we can repaint by transparency with a / fluorescent medium gel b / fluorescent medium

- gives pastel fluorescent colors

- water and weather resistant

- thinner: water applications: brush, paint spatula, roller, screen printing

The applications of the invention are extremely diverse since the fluorescent solution can be applied to any support or material such as: artistic works, decorations, stage props and costumes, jewelry, advertising works, video films, toys, etc.

The present invention also finds purely industrial applications, for example for the protection of information carried on security documents. These, after printing, are covered by a fluorescent layer according to the invention. The dilution of the fluorescent body is around 3%. Any attempt at falsification immediately appears in the light of ood since it necessarily results in a scratching of the layer to access the support. The falsifier cannot find the exact composition of the protective layer. The present invention also relates to a display device for implementing the method comprising a panel illuminated by a light source, characterized in that it comprises' at least one second source emitting a light spectrum of wavelengths different from the first and illuminating at least part of the panel.

Of course, the first source can be the sun. Thus, on an advertising panel, it is possible to obtain two different images, one by lighting with a first spectrum of light radiation, for example by daylight, and the other by lighting with a WOOD lamp. .

On a display panel, it is also possible to provide on the one hand a white light source and, on the other hand, a "black" light source. As soon as night has fallen, the two images can be revealed successively and possibly alternately by switching the white source and the black source at a given rate.

The hues of the latent and primary images and consequently the structure of the image which appears can also be modified by modifying the wavelengths of the sources. While Wood light illumination involves the phenomenon of fluorescence, it is also possible to use bodies with phosphorescent properties for the formation of the latent image or bodies having both properties simultaneously, such as rare earth. In the case where phosphorescent bodies are used, energy is stored by insolation and this energy is restored by infrared irradiation.

In the description which has just been given, the primary image is assumed to have been formed on an opaque support. It is however possible to form it on an at least partially transparent support which may include, for example Windows. In this case, a black light source can be placed in the panel, behind the primary image so that the parts corresponding to the windows are activated by black light.

A light column or panel can be sensitized from the inside (or from the back) as it is already used today but with a much higher brightness. As an indication, a light column using four fluorescent tubes of 65W each, a total of 260 watts, can be replaced under light ^awareness' of Wood with one or two tubes of 40 watts each which saves the energy with better result.

It is also possible to apply to the layer constituting the latent image a third layer composed of photophores which, by bombardment of light rays, emit UV light and activate the latent image.

The present invention can be implemented both by reflection and by transmission, which makes it possible to obtain new effects.

The applications which have been indicated above are understood in the case where the polymer is associated with a plasticizer which ensures its very rapid drying. The invention also finds applications in the field of fluorescent fluids. To this end, transparent tubes are filled with fluids carrying fluorescent pigments, the mobility of the fluids being ensured for example by suction and pressure pumps. The following table I indicates for the colors white, blue, yellow, orange, green, red, purple, brown and gray which fluorescent bodies have been used successfully. Of course, each color corresponds to a certain number of shades depending on the nature of the body used.

The pigments mentioned in the second column of the table can be used alone or in combination with traces of another pigment, as mentioned in column 3.

Column 4 indicates in certain cases the results obtained from the point of view of colors.

TABLE I

color / S UV Pigment% Observations

Esculine white 2 at 20 ° / ooo depending on the nature of the support and the background color, vε from white to blue

Calcium pyrophosphate Calcium halophosphate

Blue Esculine Blue in diluted alkalis

Esculetin trace of Blue eosine azur cyanine

Acid sky blue A 2 at 20 ° / ooo ^*

Rhapontin. Fluorex blue

Esculine + malachite green Blue green

Methyl trace malachite

= Cotton blue 2 at 20 °. / Ooo esculine

Fluorescine Yellow Fluorescine + Auramine Auramine = yellow

Eosine! more golden - we can

Resorcinol or 2 at 20 ° / ooo adjust the nuances

Tropéoline 0 of yellow by% + or

- Alizarin's - high Esculine

Methyl + Fluorescin

Eseuline + Auramin

Esculine + Eosine TABLE I

Claims

°) A method of forming images by ultraviolet irradiation, characterized in that it consists in coating an object, a part of an object or a set of objects ^" with a transparent base into which a solution of a body is introduced fluorescent in a proportion at most equal to 5% by weight of the support, then to irradiate the object.

°) Method according to claim 1, characterized in that the support consists of a vinyl or acrylic polymer and in particular a polymethylacetacrylate.

°) Method according to claim 2, characterized in that a polymethylacetacrylate gel is formed including 304% ammonium acrylate into which is introduced a solution of acrylic acid neutralized with ammonia and a fluorescent body.

°) Method according to any one of the preceding claims, characterized in that the fluorescent body or bodies are chosen from the box comprising: fluorescein, autunite, malachite for the greens, esculin for the blues, fluorine , auramine, rhodamine, eosin, pink bengal.

°) Products obtained by applying a solution according to one of the preceding claims. 6 °) display method implementing the method according to claims 1 to 4, characterized in that it consists in forming on the same support a first image sensitive to irradiation by a light source emitting according to a first frequency spectrum and at least a second image, at least partially transparent with respect to the first spectrum and sensitive to the radiation of ultraviolet radiation.

7 °) A method according to claim 6 characterized in that the latent image is formed from pigments introduced into a base transparent to white light, the first source being a source of natural or artificial white light and the second source being a ultraviolet source.

8 °) Method according to claim 6, characterized in that one of the radiations is an infrared radiation.