CH617958A5 - Process for obtaining a product which is photoluminescent in its bulk - Google Patents

Abstract

The product which is photoluminescent in its bulk comprises a synthetic binder and crystalline fillers whose light transmissivity coefficient (Tr) is at its maximum in a range extending from the ultraviolet to the infrared; it additionally comprises at least one phosphorescent substance, "upstream" products drawing energy from short wavelengths ( lambda ). The above product is advantageously applied to the fields of building and of textiles. <IMAGE>

Description

The present invention relates to a process for obtaining a photoluminescent product in its mass. It aims in particular to allow obtaining a product of this type improved, in particular for the fields of building materials and textiles.

Reference will be made more particularly, for example, to what is described in French patent disclosure No. 72.01865 (with its first addition No. 72.43104) and in French patent disclosure No. 72.10248 (with its first addition No. 72.43105). In addition to the conventional essential constituents fulfilling the essential function of the product, that is to say allowing it to be, as the case may be, in particular a real building material or a real textile, we find in the product, with incorporation in the mass, chemical matrices comprising:

1) a synthetic binder whose spectral response ranges from near ultraviolet to infrared with a maximum light transmissibility coefficient, such as, for example, acrylics, methacrylics, silicones or other similar resins,

2) crystal charges with high light transmissibility in the same spectral range,

3) phosphorescent substances known per se, such as zinc sulfide, cadmium, strontium sulfide, calcium sulfide or any other analog (for zinc sulfide, for example, the absorption of light takes place between 3800 and 4500 Â ). It should be noted now that the term phosphorescent relates, in the present description and in the appended claims, to a phenomenon of photoluminescence the remanence of which is long (greater than or equal to 10-8 s for example). Likewise, the term “fluorescence” is understood to mean the phenomenon of photoluminescence with a brief remanence (less than 10 −8 s, for example), photoluminescence being a phenomenon thus covering both phosphorescence and fluorescence.

It had already appeared useful (see on this subject the patents and additions above) to increase the energy mobilized at the level of the sensitivity range of zinc sulfide, for example by the association of aromatic substances, of the carbide type. heavy, with three nuclei such as anthracene. In this case, the function of anthracene or an equivalent substance with cyclic aromatic rings is to increase the incident energy in the products considered to increase the residual result; there is effectively proportionality between the quantity of energy emitted and the quantity of energy received (E = hv).

Said patents and additions describe products, photoluminescent in their mass, whose energy useful for the afterglow is increased by these cyclic nuclei, this being able to be understood

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as upstream products, i.e. towards short wavelengths, high frequency.

The present invention aims to provide a process for obtaining a further improvement of the products considered, mainly downstream, that is to say on the side of the longest wavelengths, and also upstream, by specifying the quantities of aromatic components to be used and the type of said components.

The method according to the invention achieves this object by the fact that it has the characteristics set out in the first appended claim.

By way of example, it is possible to envisage materials or materials which comprise at least one aromatic nucleus, a phosphorescent substance and a fluorescent substance, allowing:

1) the shift of the spectral line of the ultraviolet towards blue to amplify the incident energy (for example thanks to anthracene),

2) the re-emission of this incident energy by zinc sulphide for example (or calcium, cadmium, etc.) in a phosphorescent manner, and therefore with a prolonged remanence (greater than 10 "8 s),

3) the use of part of this residual energy and any other incident light (in night or daytime regime) to excite fluorescent dyes which give a colored quality to these emissions (with a remanence of less than 10 "8 s) .

The characteristics and advantages of the subject of the invention will emerge more clearly from the description which follows, given with reference to the appended drawing, given for information and in which:

fig. 1 diagrammatically represents the absorption (hatched areas) and emission (non-hatched areas) curves of the constituents of a photoluminescent material according to a first embodiment of the invention,

fig. 2 schematically illustrates the emission spectrum of the material according to FIG. 1, in night mode,

fig. 3 is similar to FIG. 1, the photoluminescent material corresponding to a second embodiment of the invention, and FIG. 4 represents various remanence curves as a function of time.

Referring now to FIG. 1 where the wavelengths are plotted on the abscissa, and the transmissibility coefficient Tr on the ordinate, it is found that the photoluminescent material comprises, in addition to the crystalline charges and the binder, of anthracene (dashed spectrum), a phosphorescent substance such as Zns (solid line spectrum), and a fluorescent substance (dotted spectrum). Such a material makes it possible, thanks to anthracene, to draw energy from the short wavelengths (3000-3800 Å) and to restore it, at least partially, taking into account the phosphorescence yields and fluorescence, in long wavelengths (5800-6800 Â), thanks to the phosphorescent substance and the fluorescent substance.

As shown in this fig. 1, the absorption spectrum of the fluorescent substance largely overlaps the emission spectrum of the phosphorescent substance (ZnS): this amounts to saying that there will be practically no remanence of the zinc sulfide but a fluorescence artificially maintained, with prolonged remanence, thanks to the energy emitted by ZnS. The behavior of such a material will be as follows:

- by day, the material will appear, in this case, orange, and with a strong intensity, since the fluorescent substance absorbs both part of the ambient light, as well as the energies absorbed and emitted by zinc sulfide and by l 'anthracene,

- at night, the material will also appear orange, although more yellow, and with a lower intensity than previously, the ambient light component having disappeared, it being understood that the ambient light corresponds to the part of the energy spectrum available during the day.

It will be understood the advantage of such a material, the apparent color of which is preserved, day and night, thanks to photoluminescent phenomena.

Fig. 2 shows, in solid lines, only the emission spectrum of the night material. This spectrum brings out a medium-intense green-yellow afterglow due to ZnS, as well as an orange reflection due to the fluorescent substance. Due to photoluminescence phenomena, the material therefore appears between green-yellow and orange, the colors accumulating. Although this material is less luminous than that of day, it can however perfectly be used as photoluminescent material.

According to fig. 3, in addition to the anthracene spectrum (dashed), there are emission spectra for the phosphorescent substance (in solid lines), such as ZnS, and absorption spectra for the fluorescent substance (dotted lines), which are disjoint ; this amounts to saying that the energy emitted by the zinc sulphide will not be reabsorbed as previously by the fluorescent substance.

Obviously there are differences in behavior, depending on what we see:

- by day, when the material will appear red, by fluorescence, a phenomenon which here almost completely masks that of phosphorescence,

- at night, where the material will appear green-yellow, by phosphorescence, which is then the only phenomenon occurring.

This material will be more particularly used when aspects of the material differing from day to night are desired, aspects rendered by photoluminescence phenomena.

Whichever scheme is used, fig. 1 or fig. 3, it is also possible to make certain modifications to these base materials, in terms of the products used upstream of the phosphorescent substance. As has been seen previously, the upstream product which is used here is anthracene, with three aromatic rings. This body is particularly interesting because its emission spectrum overlaps the absorption spectrum of the phosphorescent substance (ZnS), thus allowing an energy transfer from 3000-3800 Â up to 4500-5200 Â.

It was noted that anthracene could be partially replaced by other substances with similar properties.

Particularly interesting results were found when the aforementioned replacement substance was naphthalene, with two aromatic rings. This leads to photoluminescent materials, the products of which located upstream from the phosphorescent substance comprise naphthalene and anthracene; the benefits of this mixture are twofold.

A first advantage consists in that the quantity of final energy emitted by the fluorescent substance is increased; this is due to the fact that naphthalene has an absorption / emission spectrum shifted towards short wavelengths compared to that of anthracene: a certain energy will therefore be absorbed by naphthalene, then re-emitted and absorbed by anthracene, the rest of the process being illustrated in figs. 1 or 3.

A second advantage is that it is possible to reduce the amount of anthracene used, and which is expensive. All other things being equal, the same luminosity results are obtained when we go down to an anthracene molar proportion of 1% o compared to naphthalene much less expensive than anthracene. As the quantities of such products used upstream are already relatively small, it is easy to see that, in this case, the anthracene is only present in trace amounts.

When naphthalene and anthracene are used as previously indicated, this results in an absorption / emission spectrum, the absorption part of which corresponds practically to the absorption zone of the naphthalene spectrum, and the emission part of which corresponds practically to the zone emission of the anthracene spectrum.

It is understood that the presence of anthracene is made necessary by the fact that its emission spectrum overlaps the absorption spectrum of zinc sulfide, playing the role of phosphorescent substance. Depending on the type of phosphorescent substance used, this anthracene may prove to be useless (phosphorescent substance with absorption spectrum shifted towards the weak

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wavelengths) or insufficient (shift of the abovementioned absorption spectrum towards long wavelengths). In the first case, naphthalene may suffice and the anthracene will be eliminated and, in the second case, it will be necessary to provide, in addition to the anthracene, one or more relay elements, having an absorption spectrum corresponding to the emission of l anthracene, and an emission spectrum corresponding to the absorption of the phosphorescent substance; such relay elements may consist in particular of naphtacene and / or pentacene, respectively with four and five aromatic rings.

These elements find their application in particular when the zinc sulfide is replaced in whole or in part by cadmium sulfide, the latter, when it is pure, emitting in red.

The table below gives the remanence for various ZnS-CdS mixtures (molar proportions).

ZnS (%)

CoS (%)

Emission color

100

0

green

80

20

yellow green

60

40

yellow

40

60

yellow orange

20

80

Orange-red

0

100

red

Consequently, and when a photoluminescent material emitting at night in orange red is desired, or else a phosphorescent substance such as zinc sulfide is added a fluorescent body emitting in this color, the absorption spectrum of which overlaps the spectrum d emission of the phosphorescent substance (see fig. 1), or the zinc sulphide is partially replaced by cadmium sulphide (this body representing, for example, in this case, 70 to 80% of the ZnS-CdS mixture).

The daytime behavior of the material will vary depending on whether one has a ZnS-CdS (orange-red afterglow, very intense), ZnS and a fluorescent substance of the type illustrated in FIG. 1 (orange persistence, intense), ZnS and a fluorescent substance of the type illustrated in fig. 3 (orange-yellow aftertaste, moderately intense).

Various fluorescent substances can of course be used, the choice depending in particular on their absorption or emission spectrum (type fig. 1 or 3) and on the desired color.

As an indication, good results have been obtained using pigments sold by the company Marcel Quarre et Cie, under the name Radglo.

Three pigments are interesting for their color, as well as for the intensity of the emission peak:

- orange-yellow: emission peak at 5800 Â

- orange: emission peak at 6000 Â

- orange-red: emission peak at 6200 Å.

Other fluorescent substances have been tried, and have presented a certain interest: they are aromatic bodies with five or six aromatic rings (pentacene, hexacene). It is precisely pentacene which is illustrated in FIG. 1.

The use of these aromatic nuclei is particularly advantageous insofar as homologous bodies, but with a smaller number of nuclei, are used upstream of the phosphorescent substance. Indeed, in this case, the aromatic bodies with a high number of nuclei constitute dopants for those which have a limited number of aromatic nuclei.

Two sequences were found to be very good: © anthracene-ZnS-pentacene (case of Fig. 1 with overlapping phosphorescence / fluorescence spectra), © anthracene-ZnS-hexacene (case of Fig. 3 with disjoint phosphorescence / fluorescence spectra) .

Examples of embodiments will now be described, it being understood that they are in no way limiting.

Example 1

This example relates to a photoluminescent textile, obtained by coating, using the system known as doctor blade on cylinder.

A typical coating composition is obtained as follows:

a) 800 g of ZnS (phosphorescent substance) are dissolved in 3% Tylose 4000 (2000 g); this dissolution takes place around 30-40 ° C with stirring,

b) 2 g of anthracene (product upstream of ZnS) and 0.03 g of pentacene (fluorescent substance) are dissolved in 380 g of propanol-2; this dissolution is done by heating under reflux, at a temperature below 80 ° C.,

c) mixing, using a plunging agitator, 2174 g of transparent fillers (SÌO2 type), with the resin complex formed of 1000 g of Acrymil Protex, 30 g of Actiron (catalyst) and 120 g d 'softener,

d) the solutions a) and b) are mixed at around 40 ° C., gradually introducing, with constant stirring, b) into a), until complete homogenization,

e) then added to the solution d) the mixture c).

Example 2

The material which is the subject of this example can in particular be used in building, and the operating mode is as follows:

a) 600 g of ZnS (phosphorescent substance) are dissolved in 3% Tylose 4000 (1200 g); this dissolution takes place around 30-40 ° C with stirring,

b) 4 g of anthracene (product upstream of ZnS) and 0.06 g of pentacene (fluorescent substance) are dissolved in 760 g of propanol-2; this dissolution is done by heating at reflux, with a temperature below 80 ° C.,

c) using a stirrer, 6000 g of transparent fillers (type S mélangeO2) are mixed with the resin complex formed of 2000 g of Rodopas-AM 054 (Rhône-Poulenc), and 32 g of Texanol,

d) the solutions a) and b) are mixed at around 40 ° C. by gradually introducing, with constant stirring, b) into a) until complete homogenization,

e) then added to the solution d) the mixture c).

An identical formula, but without crystalline fillers, makes it possible to achieve continuous dyeing of thread, for example using a nozzle of the process from the company O.P.I., or other similar process.

Example 3

The anthracene of Example 2 is replaced by a naphthalene / anthracene mixture, with an anthracene / naphthalene molar ratio = 0.01.

The materials obtained in examples 1, 2, 3, all have orange remanent colors.

Preferably, in the photoluminescent materials of the present invention, the proportions are as follows:

- upstream products: 0.1 to 1% (molar proportion) relative to the synthetic binder,

- phosphorescent substance: 5 to 15% (proportion by weight) relative to the chemical matrix (synthetic binder + crystalline charges),

- fluorescent substance: 0.1 to 1% (weight proportion) relative to the phosphorescent substance.

Various lighting tests of these materials were carried out, more particularly with regard to the textile of Example 1. In this last case, the textile material was illuminated for 20 s at 300 Ix, and the curve of the intensity of remanence as a function of time was studied.

This curve appears in solid lines in FIG. 4 where the time (in hours) is plotted on the abscissa, the intensity of remanence appearing on the ordinate. For comparison, we dotted the curve of a conventional photoluminescent textile, that is to say without upstream product or fluorescent substance, the photoluminescent material applied to the textile comprising only ZnS

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as a photoluminescent substance, the application being made in film-forming form. A dashed curve is also shown in fig. 4, so-called ideal curve, of the battery discharge type, towards which the curve in solid line should tend.

It appears from this fig. 4 that the initial intensity I'o of our curve is much higher than that Io of the ZnS curve, and this intensity (solid line) remains higher than that of ZnS most of the time, mainly in the interval 5 h- 9 p.m. (which normally corresponds to the time limit for ZnS remanence).

It appeared that better results were obtained when the upstream product was diphenyloxazol, which also has the same property as anthracene, namely to draw energy at short wavelengths to re-emit it at the spectrum level. absorption of the phosphorescent substance such as zinc sulfide.

Thus, a basic formula (A) was produced containing a synthetic binder, crystalline fillers and other elements necessary for its constitution. This formula (A) comprises in weight shares:

Synthetic binder: vinyl acetate / maleic ester 200 copolymer

ZnS 54.7

Tylose MH 4000 K at 4% 49.5:

Texanol 3.2

Methanol 10

Crystal charges 693

1010.4.

Preferably, the upstream product used will be diphenyloxazol (PPO).

The following examples of photoluminescent products have been produced, where the proportions of upstream and downstream products are expressed in M (mole / kg of synthetic binder).

Sample

Afterglow after cutting the excitation

Example 4

(A) + upstream product downstream product

Example 5

(A) + upstream product downstream product

Example 6

(A) + upstream product downstream product

Example 7

(A) + upstream product downstream product f PPO (10_ 3 M) 1 Rhodamine B (8.3 • 10 "6 M)

f PPO (10 "3M)

1 Rhodamine B (1.25-10 "5 M)

f PPO (10 "3M) 1 Rhodamine B (10-4 M)

[PPO (10 "3M) | Rhodamine B (2 • 10" 5M) (Uranin S (10 "5M)

The samples corresponding to formula (A), that is to say containing neither upstream product nor downstream product, as well as in examples 4,5,6, and 7, were tested as follows:

- excitation: 2 min at 160 lx

- lamp: color temperature 4200 ° K.

The table below summarizes the remanence values obtained as a function of time, expressed in candelas / square meter (cd / m2).

15 "

30"

45 "

(cd / m2; Y

1

the 30 "

2 '

2'30 "

Formula (A)

0.395

0.253

0.19

0.158

0.123

0.102

0.0917

Example 4

0.438

0.275

0.202

0.165

0.125

0.105

0.0933

Example 5

0.417

0.257

0.194

0.159

0.121

0.102

0.0915

Example 6

0.401

0.253

0.191

0.156

0.120

0.101

0.0919

Example 7

0.404

0.270

0,201

0.165

0.123

0.104

0.0924

The table below summarizes the photoluminescent gains, expressed as a percentage, compared to conventional phosphorescent products (formula (A)):

AT%

15 "

30"

45 "

1 '

the 30 "

2 '

2'30 "

Example 4

10.9

8.69

6.31

4.43

1.62

2.94

1.74

Example 5

5.57

1.58

2.10

0.6

-1.6

0

-0.2

Example 6

1.52

0

0

0

0

0

0

Example 7

2.28

6.7

0.55

4.43

0

1.96

0.76

It will be noted, except for example 6, that the gain is appreciable, especially for the first minute following extinction (excitation stops); As such, Example 4 is quite remarkable since, even after 2'30 ", there is still a gain in photoluminescence. However, the photoluminescent products which are the subject of the present invention are essentially safety materials which must be effective especially when switching off a light, so as to avoid any surprise on the part of the user caught off guard in the dark.

It should be noted that the anthracene examples (examples 1 to 3) also resulted in an interesting initial gain (cf. fig. 4).

Depending on the concentration of the fluorescent substances, daytime colors ranging from creamy white to yellow and orange can be obtained, while mixture A has a green-yellow color.

Conventional fluorescein has also been used to replace uranine S.

Another type of product, still within the scope of the present invention, has been produced, with a view to application in industrial floors, car parks and road markings.

This product has the following composition, in weight proportions:

R2o alloprene (chlorinated rubber) Xylene

PPO (upstream product)

Rhodamine B (downstream product) Aerosol 200 Cerechlor 42 Methyl ethyl ketone ZnS

Glass beads (crystal fillers) type 063.200 type 250.630

35 65

0.022 (10 "3M) 4.79 10_5 (10" 6M) 0.5 17.5 25 40

190.5 127

500.5

These good results are the consequence of two factors which combine, namely, firstly, a mass effect of the material, the light being able to reach the core of the material thanks to the transparent charges and, secondly, an energy transfer effect thanks to overlapping the spectra of the upstream product (s) and the phosphorescent substance (s) and, possibly, thanks to the overlapping of the spectra of the phosphorescent substance (s) and the fluorescent substance (s).

2 sheets of drawings

Claims (19)

617 958 1. Method for obtaining a photoluminescent product of the type comprising in particular a synthetic binder, the spectral response of which ranges from ultraviolet to infrared with a maximum light transmissibility coefficient, crystalline charges with high light transmissibility in the same spectral range, and at least one phosphorescent substance, characterized in that one uses: - 0.1 to 1% in molar proportion relative to the synthetic binder, of so-called upstream products, drawing energy from short wavelengths and re-emitting it at the level of the absorption spectrum of the or the 'one of the phosphorescent substances, 2. Method according to claim 1, characterized in that said auxiliary substance is fluorescent and is chosen so that its absorption spectrum overlaps the emission spectrum of the phosphorescent substance. 2 3. Method according to claim 1, characterized in that said auxiliary substance is fluorescent and is chosen so that its absorption spectrum and the emission spectrum of the phosphorescent substance are separated. 4. Method according to claim 1, characterized in that said auxiliary substance is fluorescent and is an aromatic compound with a high number of nuclei. 5. Method according to claims 2 and 4, wherein the main phosphorescent substance is zinc sulfide, characterized in that said aromatic compound is pentacene. - 5 to 15% by weight proportion of at least one main phosphorescent substance relative to the chemical matrix constituted by the synthetic binder and the crystal charges, - 0.01 to 10% in weight proportion relative to the main phosphorescent substance of at least one fluorescent or phosphorescent auxiliary substance chosen to give a residual color different from that of the main phosphorescent substance or substances. 6. Method according to claims 3 and 4, wherein the main phosphorescent substance is zinc sulfide, characterized in that said aromatic compound is hexacene. 7. Method according to claim 1, characterized in that said auxiliary substance is fluorescent and consists of one or more pigments. 8. The method of claim 1, wherein the main phosphorescent substance is zinc sulfide, characterized in that said upstream substance is anthracene. 9. Method according to claim 8, characterized in that the anthracene is partially replaced by naphthalene, the anthracene / naphthalene molar ratio preferably being of the order of 10 ~ 3 to 10 "2. 10. Method according to claim 1, characterized in that said auxiliary substance is phosphorescent. 11. Method according to claim 10, characterized in that said auxiliary substance is cadmium sulphide, the main phosphorescent substance being zinc sulphide. 12. The method of claim 1 wherein the phosphorescent substance is zinc sulfide, characterized in that said upstream substance is diphenyloxazol. 13. Method according to claim 12, characterized in that the concentration of diphenyloxazol is 10 "3 mole / kg of synthetic binder. 14. Method according to claim 12, characterized in that the downstream product is rhodamine B and / or uranine S. 15. The method of claim 14, characterized in that the concentration of the product downstream is 10 "6 to 10" 4 mole / kg of synthetic binder. 16. Method according to one of claims 12 to 15, characterized in that about 20% by weight of synthetic binder is used such as the vinyl acetate / maleic ester copolymer, and 70% of crystalline fillers. 17. Method according to claim 1, characterized in that the following steps are carried out: a) dispersion of the main phosphorescent substance or substances, b) dissolution of the products upstream and, where appropriate, of the fluorescent substance by any suitable solvent, c) mixing the crystalline fillers and the synthetic binder, d) introduction of solution b) into solution a) and mixing until homogenization, e) addition to the mixture c) of the mixture d). 18. Method according to claim 17, characterized in that, the main phosphorescent substance being zinc sulphide, the dispersion takes place in Tylose, and in particular Tylose 4000 at 3%, preferably at a temperature of 30 to 40 ° C. 19. The method of claim 17, characterized in that, the upstream products being constituted by pure anthracene or mixed with naphthalene, and the fluorescent substance being pentacene, the dissolution takes place in propanol-2, preferably at a temperature below 80 ° C.