WO1987000723A1

WO1987000723A1 - Covering element with light cascade effect particularly for agricultural applications

Info

Publication number: WO1987000723A1
Application number: PCT/FR1986/000276
Authority: WO
Inventors: Philippe Gravisse
Original assignee: Philippe Gravisse
Priority date: 1985-08-02
Filing date: 1986-08-01
Publication date: 1987-02-12
Also published as: FR2585716B3; EP0231312A1; DK166187A; JPS63500352A; DK166187D0; FR2585716A1

Abstract

Covering element, particularly for agricultural greenhouses, comprised of an organic matrix containing a plurality of luminescent and/or scintillating doping materials forming at least one light cascade which absorbs an electromagnetic radiation in at least one first predetermined wave length band to reemit said light cascade into at least one second predetermined wave length band, characterized in that said organic material further comprises substances which diffuse the incident radiation.

Description

_El ement _o f lap light cascades effect particularly for agricultural applications;

The present invention relates to a covering element of the type consisting of an organic matrix containing several luminescent and / or scintillating doping materials forming at least one light cascade absorbing electro- ^• magnetic radiation in at least one first strip. of predetermined wavelengths to re-emit it in at least a second band of predetermined wavelengths.

Such elements are described in their application as a covering element for agricultural greenhouses and as a herbicide film in French patent applications No. 81.16.678 of

September 2, 1981 and No. 85,083.85 of the present depositor. In the pre¬ Mière implementation is intended to promote photosynthesis plano ^{^'your'} while absorbing the tape lengths of harmful waves plant development. In the second application, on the contrary, the aim is to absorb the radiation in the bands of wavelengths favorable to photosynthesis and a re-emission of the radiation in bands of wavelengths preventing the development of plants. - 'The two elements invented and ^; developed by the present applicant have made it possible to obtain excellent results during experiments and operations in different climatic zones. These ^'results- quite exceptional exposed no¬ MENT in the French patent application No. 81 16 678.

On the other hand, the products developed so far for the two said applications have two major drawbacks which make their widespread use costly. First, the doping materials used to form the light cascades are complex chemicals of very high cost. On the other hand, their stability in the organic matrix is relatively limited, which considerably reduces the effective life of the products obtained, which has a major drawback for these agricultural applications.

The main object of the present invention is to conceive of an element of said type having an improved active service life allowing general use of the elements for the two applications described above.

In the covering element according to the present invention which is of the type described above, characterized in that the organic matri¬ comprises moreover materials diffusing the incident radiation. Practical tests have unexpectedly demonstrated that the presence of the diffusing materials not only increases the stability of the doping materials in the organic matrix but also considerably improves the yield of the light cascades thus formed. The reasons for these two results combined are not understood, but the applicant considers that the diffusing materials protect the doping materials against direct incident radiation, which makes it possible to increase their stability. In addition, thanks to the presence of diffusing materials in the matrix, the length of the path of the photons of the incident radiation inside the matrix is increased and each photon consequently meets with greater probability at least one dopant during of its path through the matrix. This very considerably increases the efficiency of the light cascades for a given doping material concentration for a predetermined thickness of the element according to the invention.

According to the invention, said diffusing materials are mineral materials used in the form of particles of very small dimensions. ^' ; "According to a preferred embodiment of the invention, the diffusing material is titanium oxide.

According to another advantageous variant, the diffusing material is an ultrafine silica. These two products made it possible to obtain very satisfactory results. However, it is also possible to use, according to the invention, known organic diffusing substances and in particular organic resins.

According to a particular embodiment of the invention, said matrix is a sheet of polyethylene with a thickness of the order of 100M. at 200M. which contains as diffusing material a polystyrene resin in homogeneous emulsion and in a content of the order of 10% to 40% by weight.

According to yet another advantageous variant of the invention, said organic matrix is a sheet of polymethylmethacrylate (PMMA) with a thickness of about 3 mm containing as diffusing material water in a content of the order of 1 to 3xl0 ~ ⁴ mole / liter.

The invention also relates to the use of iffusantes ^of materials in a member for forming in particular a cover element for greenhouses, and of the type in le- which the absorption band or bands of the light cascades are located in wavelengths which do not favor the photosyn¬ thesis of plants while their re-emission bands are si¬ killed only in the wavelengths favoring the photo-

0 synthesis and in particular in bands between 4000 A

0 0 0 and 5000 A and between 6000-A and 7000 A, and in which said doping materials comprise at least one first aromatic cyclic material of the five-core type.

In this embodiment, the present invention provides that the concentration of said first aromatic cyclic material is approximately 5 × 10 -3 mole / liter and that of said second

_ _4th aromatic cyclic material is approximately 9 × 10 mole / liter for a matrix with a thickness of the order of 100 to 200 LL.

This considerable reduction (division by 100) in the concentration of doping materials is possible thanks to the improved rendering of the light cascades obtained thanks to the presence of the diffusing materials in the organic matrix.

When such a cover element for agricultural greenhouses further comprises a third and ^; fourth aromatic cyclic material, the concentrations of these materials can also be reduced in the same proportions for a given sheet thickness without reducing the yield of the luminous cascades.

The invention also relates to the use of diffusing materials in an element of the type forming a herbicidal sheet intended to be placed above a culture plane and in which the absorption bands of the light cascades run

0 0 have wavelengths between 4200 A and 5000 A and

0 0 between 6000 A and 7000 A while the retransmission bands

0 0 have wavelengths between 5000 A and 6000 A and

0 wavelengths greater than 7000 A, and the doping materials comprise a first and a second aromatic cyclic material.

According to the present invention the concentrations of said first and said second aromatic cyclic material are

-4 ₄ of about 5x10 mole / liter and about 5x10 mole / liter respectively for a sheet with a thickness of about 80 ~ This division, per hundred of the concentration of the materials of page also proven to be possible in this application without loss of light cascade performance. According to the invention, the doping materials can be introduced into the matrix by simple compounding or according to known chemical grafting procedures. These latter methods make it possible to obtain good results for the stability of the dopants in the organic matrix.

To further increase the output of the light cascades in an element according to the invention, said organic matrix has microperforations regularly spaced over its entire surface and preferably the diameter of the perforations is about 1 mm and their spacing about 1.5 cm. These perforations constitute true waveguides avoiding self-absorption of the reemission photons when their average path exceeds a given critical length.

The efficiency of light cascades is further improved according to the invention when said organic matrix has on its surface exposed to incident light an anti-reflective texture such as a texture in the shape of a diamond point.

Other embodiments and advantages of the invention will emerge from the description which follows, and with reference to the appended drawings in which FIG. 1 is a diagram showing in a very schematic manner the effect shade obtained with cover sheets of agricultural greenhouses according to the prior technique and with a sheet according to the invention and the light cascade effect obtained with a sheet according to the invention and Figures 2 to 5 illustrate improvements obtained with the aid of the sheet according to the invention in the cultivation of different varieties of beans under an agricultural tunnel.

In Figure 1 are shown in 1'énergie overall percentage of incident solar radiation according to the wavelengths of the shadowing effects obtained with neutral films, a film doped to said French Patent Application No. 81.16.678 and ^σ a film according to the present invention. For reasons of clarity, the shading effect is represented here as a uni¬ form phenomenon over the entire band of wavelengths covered by the incident radiation, that is to say in the form of linear curves parallel to the horizontal axis of the diagram. The upper line indicates for reference the level of 100% corresponding to the all of the energy of the incident radiation. The line below the reference line shows the shading effect obtained with a conventional ethyl-vinyl-acetate sheet without dopant and is approximately 85% of the energy of the incident radiation. The following line illustrates the shading obtained with an ethyl -> vinyl - acetate sheet comprising dopants forming luminous cascades according to said French patent application No. 81. 16,678. This leaf lets through 84% of the energy.

Finally the lower line shows the shading effect obtained with a film according to the invention which allows only 76% of the energy of the incident sunlight to pass. This gives a significant shading effect which is very advantageous in itself since it enables the greenhouse to be overheated.

In addition, we see in FIG. 1 four curves 1 to 4 illustrating very schematically the results of reemission obtained thanks to the use of light cascades whose reemission bands are located in the wavelength bands favoring

0 0 0 photosynthesis namely between 4000 A and 5000 A and 6000 A and 7000 A. The curves 2 and 4 show the re-transmission obtained with a film- cascades- with light in said patent application ^"Applicant's earlier French and reaching peaks at 105% and 110% respectively of the energy of the incident radiation in these two bands. Curves 1 and 3 show the results obtained with a film according to the present invention, which reach levels of 109%. and 128% of the incident radiation in the two so-called wavelength bands favoring plant photosynthesis.

It is thus seen that the invention makes it possible to simultaneously improve the shading effect of the sheet and the efficiency of the light cascades.

The invention thus constitutes a considerable and unexpected improvement the sheets according to said French patent application No. 81.16.678 _m The elements according to said patent application have the drawback of reduced stability of doping materials and of limited yield bright waterfalls.

According to the present invention, diffusing materials are introduced into the organic matrix in addition to doping materials, such as very fine particles of mineral materials, or organic resins. Such diffusing materials increase the stability of the doping materials and the efficiency of the light cascades and thus make it possible to considerably reduce the necessary concentration of the doping materials which are very expensive products.

Very positive results have been obtained with mineral materials such as titanium oxide or ultrafine silicas used in concentrations of approximately 3 × 10 mole / liter for a sheet with a thickness of approximately 100 to 200 M. also used organic resins such as polyester resin in concentrations of the order of 10 to 20% for very thin films 100 to 200 JJL.

Thanks to the invention it was possible to significantly reduce the concentrations of dopants as clearly shown in the following examples illustrating the application of the inven¬ tion to agricultural greenhouses cover film of the request for _/ French Patent No. 81 16 678 of the depositor. • in the practical examples below each film is made of an organic ma¬ trice (polyméthylméthatelat for example) comprising four body doping formed by cyclic aromatic materials ^"c .telles described in said French patent application -from .

Example 1: film thickness: 80 ^ -. (polyethylene - ethyl - vinyl-acetate body concentration in mole / liter 5 n ° 1 5 x ÎO ^ ³ n ° 2 9 x 10 n ° 3 7 x 10 ^" n ° 4 2,5 x 10 ⁴ polystyrene type diffuser - 20 % in weight

0 Example 2: film thickness: 200 jx.Xpolyethylene - ethyl-vinyl-acetate) body concentration in mole / liter n ° 1 2 x 10 ^" ? N ° 2 4 x 10 5 n ° 3 2,5 x lθ ^{" 4} # 4 1.5 x 10 diffuseur- polystyrene type ^'- 10% by weight

These concentrations being a function of the thickness of the film, we notes that the concentrations cited in these examples are much smaller (divided by a hundred) than those according to la¬ said prior patent application while ensuring better performance of light cascades. This result, obtained through the use of diffusing materials, also makes it possible to envisage an explanation of certain apparently random observations made by the depositor during the experimentation of greenhouse cover films according to his invention. The variations in the operation of the observed light cascades can now be explained by the fact that the efficiency of the light cascades is greater in diffuse light than in direct light.

The element according to the invention consequently presents in its application as an element for covering agricultural greenhouses two considerable advantages:

- in direct light it forms an advantageous diffusing screen which limits the heating of the greenhouse and tightens the gaps between the maximum and the minimum of illumination.

- in diffused light, the yield of light waterfalls is better and favors the development of plants in cases of significant needs (in cloudy weather in particular - in the early season). In Examples 1 and 2, the following doping materials have been used successfully in combination with said diffusing materials:

_^ case 1 case 2 case 3 body n ° l PPO PPO PPO body n ° 2 POPOP bis (MSB) Coumarine 102 body n ° 3 Rodamine B bis (MSB) Coumarine 102 body n ° 4 Sulphorodamine 101 bis (MSB) Coumarine 102

Below are the comparative experimental results of a mash culture carried out under simple films and equivalent films according to the present invention. The variety of lamb's lettuce was VIT and the elementary plots of forty frames were sown in November and fully harvested at the end of March of the following year. O 87/00

Figures 2 to 5 show the output curve (rende¬ ment ^accumulated in gr / day) plot of four varieties of hari¬ costs, the type Talisman CV (Figure 2), Martingal CV (Figure 3) CV Calvy ( figure 4) and CV Cristal (figure 5). • In these figures, the dashed curves show the production obtained under an ordinary control ethyl vinyl acetate sheet without light cascades while ^" in dot lines illustrate the production carried out under a sheet according to the invention with light cascades and diffusing materials. It is clearly seen that the use of the leaf according to the invention leads to an improvement in weight of the production for all the varieties over the entire period of plant development.These results are particularly advantageous for the variety CV Cristal (Figure 5) In this case the cumulative yield goes from around 6,600 gr / plot to 12,500gr / plot at the end of normal harvesting. This result is completely unexpected given the very low concentration of doping materials used in the film. according to the present invention.

As already explained above, the invention also applies to films according to French patent application No. 85.083.85 by the applicant, which is aimed at a film with light cascades intended to prevent the development of plants. In this case, the introduction of diffusing materials into the organic matrix also makes it possible to reduce the concentration of doping materials while increasing the efficiency of the light cascades. For an element about 80 xx thick. comprising two aromatic cyclic materials as dopants, it is possible, thanks to the introduction of diffusing materials according to the present invention, to reduce the contents to values of approximately 5 × 10 -4 mole / liter and 5 × 10 -4 mole / liter.

In the two applications mentioned above, the results can be further improved by providing micro-perforations in the organic matrix with a diameter of approximately 1 mm and a spacing of 1.5 cm. This avoids self-absorption of photons.

Of course, the invention is not limited to the embodiments described here.

Claims

O 87/00723

1) Covering element of the type consisting of an organic matrix containing several luminescent and / or scintillating doping materials forming at least one light cascade absorbing electromagnetic radiation in at least a first band of wavelengths predetermined for re-emitting in at least a second band of pre-determined wavelengths, characterized in that the organic material also comprises materials diffusing the incident radiation. 2) Element according to claim 1, characterized in that said diffusing materials are mineral materials used in the form of particles of very small dimensions. 3) Element according to claim 2, characterized in that the diffusing material is titanium oxide. 4) Element according to claim 2, characterized in that the diffusing material is an ultrafine silica.

5) Element according to claim 1, characterized in that the diffusing materials are organic materials.

6) Element according to claim 5, characterized in that the diffusing materials are organic resins.

7) Element according to claim 6, characterized in that the said matrix is a polyethylene sheet with a thickness of the order of 100d. To 20p * which contains as diffusing material a polystyrene resin in homogeneous emulsion and in a content of the order of 10% to 20% by weight.

8) Element according to claim 5, characterized in that the said organic matrix is a sheet of polymethylmethacrylate (PMMA) with a thickness of about 3 mm containing as diffusing material water in a content of l '' order from 1 to

—4 3 x 10 mole / liter.

9) Element according to any one of claims 1 to 8 intended in particular to form a covering element for agricultural greenhouses and of the type in which the band or bands of absorption of light cascades are located at wavelengths do not favor the photosynthesis of plants while their re-emission bands are located only in the wavelengths favoring photosynthesis and in particular in bands between 4000'A and 5000 A and 0 0 between 6000 A and 7000 A, and wherein said doping materials comprise at least a first aromatic cyclic material of the three-core type and a second aromatic cyclic material of the five-core type, characterized in that the concentration of said first cyclic matter aro-

_ _{3 material} is approximately 5x10 mole / liter and that of ladiitt "e -5 second aromatic cyclic material is approximately 9x10 mole / liter for a matrix with a thickness of the order of 100 to 200 JLX. 10) cover element according to claim 9, and of the type comprising a third aromatic cyclic material, charac¬ terized in that the concentration of said third aromatic cyclic material is about 5x10 -4 mole / liter, for a matrix with a thickness of the order of 100 to 200JΛ. 15 11) cover element according to claim 10, caracté¬ ized in that it contains a fourth cyclic material aro

_5 matic in order content _. from 1 to 5x10 mole / liter for a matrix with a thickness of the order of 100 to 200 x.

12) Element according to any one of claims 1 to 8,

20 and of the type forming a herbicidal sheet intended to be placed above a cultivation plane and in which the absorption bands of the light cascades cover tones

0 0 wavelengths between 4200 A and 5000 A and between

0 0

6000 A and 7000 A while the retransmission bands cover

0 0

25 wavelengths between 5000 A and 6000 A and

0 wavelengths greater than 7000 A, and the materials on page comprise a first and a second aromatic cyclic material, characterized in that the concentrations of said first and said second aromatic cyclic material are of about 5x10 -4 mole / liter respectively for a sheet with a thickness of about 80 ..

13) Cover element according to any one of claims 1 to 12, characterized in that said do¬ page materials are introduced into the organic matrix by compoun-

35 dage.

14) Cover element according to any one of claims 1 to 12, characterized in that said doping materials are introduced into the organic matrix by chemical grafting.

40 15 ⁾ Cover element according to any one of the claims cations 1 to 12, characterized in that said organi¬ matrix has microperforations regularly spaced over its entire surface.

16) Cover element according to any one of claims 1 to 12, characterized in that said organic matrix has on its surface exposed to incident light an anti-reflection texture such as a diamond-tip texture .

17) Cover element according to claim 16, characterized in that the diameter of the perforations is approximately 1 mm and their spacing approximately 1.5 cm.