FR2769979A1 - UV sensor having a photoluminescent-doped phosphate glass sheet - Google Patents

Abstract

An UV sensor has a photoluminescent Tb2O3-doped and Ce2O3-doped phosphate glass sheet (3) for converting UV light into visible light. An UV sensor having a spectral response close to the sensitivity of human skin at 280-400 nm comprises an UV pass filter (1, 2), a photoluminescent sheet (3) for converting UV light into visible light and a visible light pass filter (4). The photoluminescent sheet (3) consists of a photoluminescent phosphate glass which is doped with (expressed as cation %) \>2 and <= 20% Tb2O3 and 0.05-0.4% Ce2O3, the P2O5 content being at least double the total Tb2O3+Ce2O3 content. Independent claims are also included for: (i) an UV dosimeter including the above UV sensor; and (ii) a photoluminescent glass as described above.

Description

The invention relates to a sensor and a dosimeter for ultraviolet radiation and to photoluminescent glasses for their manufacture.

This invention relates to ultraviolet radiation dosimetry for skin protection.

For humans, the biological effect resulting from exposure to natural or man-made ultraviolet radiation depends on the amount and spectral distribution of the incident radiation. For this reason, the dose of exposure to radiation causing a photobiological response (UV erythema or "sunburn, pigmentation, skin cancer, etc.) can be determined using a dosimeter for personal use. This dosimeter is calibrated on the spectral sensitivity characteristic of photobiological processes.

où
Ee(x) est le spectre d'irradiance de la source,
Eeff est l'irradiance actinique (la puissance de la dose actinique), et
S(X)rei est le spectre d'action, c'est-à-dire l'efficacité relative du rayonnement à produire un effet biologique particulier dans un certain domaine de longueur d'ondes, normalisée à l'unité à une longueur d'onde de référence X0. According to the Technical Report of the Commission
International Lighting Institute (CIE), [l], irradiation can be correlated with the resulting biological effect by an equation of the type

or
Ee (x) is the irradiance spectrum of the source,
Eeff is actinic irradiance (the potency of the actinic dose), and
S (X) rei is the action spectrum, i.e. the relative efficiency of the radiation to produce a particular biological effect in a certain wavelength range, normalized to unity at a length d X0 reference wave.

où
Heff est la dose actinique d'exposition, égale à une dose de rayonnement monochromatique de longueur d'onde X0, qui produit le même effet biologique que le rayonnement ultraviolet de la source à laquelle le sujet est exposé.The actinic exposure dose is given by the following expression

or
Heff is the actinic exposure dose, equal to a dose of monochromatic radiation of wavelength X0, which produces the same biological effect as ultraviolet radiation from the source to which the subject is exposed.

Personal UV dosimeter indications should therefore ideally be independent of the Ee (X) irradiance spectrum. Consequently, its spectral sensitivity should be identical to the action spectrum of the photobiological effect considered. In other words, it should simulate the sensitivity of human skin.

The determination of the action spectra of human skin has been the subject of numerous experimental and theoretical studies over the last fifty years (see for example [2] and [3]). The essential and unanimously accepted conclusion of this work is the erythema action spectrum defined by McKinley-Diffey as being the best ideal response for human skin [4]. The advantage of this approach over others is that it takes into account the UVA part of the spectrum, between 320 and 400 nm, a particularly large interval for the erythemal threshold (“sunburn” threshold). Other responses of human skin to UV irradiation, such as melagenesis, photoinduced elastosis, or photocarcinogenesis are similar [3].

Most commercially available UV dosimeters for personal monitoring are based on polymers [1]. Upon exposure to ultraviolet radiation, photochemical reaction products are formed which modify the physical properties of these polymers. By measuring one of these physical properties, the exposure dose can be deduced therefrom. Other dosimeters are still based on the characteristics of thermoluminescent materials, the intensity of the resulting thermoluminescence depending on the ultraviolet doses absorbed.

The most commonly used personal dosimeters to date include a 40mm thick polysulfone (PSF) film [1]. The assay is based on the measurement of the increase in the absorption of this material at 330 nm, during its exposure to UV.

The advantages of polysulfone for personal dosimeters are its insensitivity to exposure intensity, ease of handling and low cost. However, this material also has drawbacks
- a spectral sensitivity range restricted to the interval between 250 and 330 nm, ie an absence of sensitivity to most of the UVA range (330400nm). In addition, the spectral response of the material is only roughly in agreement with the characteristic erythemal action spectrum.
- a non-linear dependence as a function of the dose of incident ultraviolet rays
- a limited dynamic range (up to two orders of magnitude).

There is therefore a need for dosimeters with improved properties.

The invention aims to meet this need by means of a new approach to ultraviolet radiation dosimetry.

According to one of its aspects the invention relates to a UV sensor having essentially the same spectral response as the characteristic erythemal action spectrum, which is based on the use of a photoluminescent glass which converts the incident ultraviolet radiation into visible luminescence. that can be measured. According to another aspect, the subject of the invention is a UV dosimeter incorporating said UV sensor. According to yet another aspect, the invention relates to novel photoluminescent glasses necessary for the production of the sensors and dosimeters of the invention.

More precisely, the invention relates to a UV sensor having a spectral response close to the sensitivity of human skin between 280 and 400 nm, comprising filtering means (1, 2) allowing only incident UV radiation to pass, a plate ( 3) of photoluminescent material converting the W radiation into visible radiation and a filter (4) allowing only visible luminescence to pass, characterized in that said plate consists of a photoluminescent glass whose composition comprises constituent oxides of glass including P2Ost and doping oxides consisting of Tb203 and Ce2O3, with the conditions that the P2O5, Tb203 and Ce2O3 contents, expressed as cationic percentages, satisfy the following relationships
0.05 S Ce203 S 0.4
2 <Tb203 S 20
P2O5 2 2 (Ce2O3 + Tb203).

Ce2O3 and Tb203 are the doping oxides, which combined with phosphorus oxide, provide adequate luminescence properties.

At least 0.05% Ce203 and 2% Tb203 are needed to obtain a glass with an appropriate action spectrum (spectral sensitivity) and luminescence spectrum. The presence of more than 0.48 of Ce2O3 does not provide additional benefits while a proportion of more than 20% of
Tb203 gives a distorted spectral response. A content of
P205 at least double the sum of the Ce203 contents and
Tb203 is necessary to ensure an appropriate structural environment for cerium and to achieve the luminescence properties required for the intended application. It is preferred that the content of P205 is equal to at least 3 times, and more preferably at least 10 times, the sum of the contents of Ce203 and Tb203.

The constituent oxides, other than P205, Tb203 and Ce2O3, completing the composition of the glasses used in the invention are not critical and can be chosen from the usual constituents, network formers, included in the glasses. By way of nonlimiting examples, mention may be made of SiO2, B203, A1203, alkaline earth oxides such as CaO, SrO, BaO and MgO, alkali metal oxides such as Na2O, K2O, Li2O, oxides such as ZrO2,
ZnO, La203, etc. ... The use of glasses whose composition includes La203, CaO and Al203 in addition to P205, Tb203 and Ce203, is preferred. Are particularly preferred to date glasses whose composition consists of cationic% of: 65-77% P205, 2.5-22% La203, 0-7% Au203, 020% CaO, 2-10% Tb203 and 0, 05-0.4% Ce203.

The invention also relates to a UV dosimeter comprising such a sensor and means for metering the visible radiation emitted by the sensor, as well as the photoluminescent glasses used in the sensor and the dosimeter of the invention.

Most of the luminescence generated by the glasses of the invention is located in a narrow spectral band, between 530 and 560 nm. In the UV sensor of the invention, a direct proportionality is obtained between the intensity of the incident ultraviolet radiation and that of the resulting luminescence. Finally, the exploitation of the luminescence signal (number of photonic pulses in real or cumulative time) allows the direct dosage of the power of the dose and the dose of ultraviolet radiation.

Prior art
Photoluminescent glasses containing Tb203 and / or Ce2O3 as doping oxides are already known.

US-A-4,134,851 claims a luminescent aluminophosphate glass emitting in the green when excited by UV radiation, which consists essentially of 25 to 36 mole% of A1203 and P2O5 for the remainder and which is doped with 0.5-1% cationic of Ce3 + and by 6-98 cationic of Tb3 +. This glass is used as a luminescent envelope for mercury lamps.

EP-A-0 199 409 describes luminescent aluminoborate and / or aluminosilicate glasses, consisting of a matrix formed from 5-65 mol% of at least one of the alkaline earth oxides BaO, SrO, CaO, ZnO and MgO , from 20-85 mole% of at least one of the oxides B203 and SiO2, and from 1-35 mole% of Al203, of dopants Tb3 + and Ce3 + in an amount calculated as Tb2O5 and / or Ce203, from 0.1 to 10 mole% based on the matrix.

These glasses, which do not contain P2O5, are used in gas discharge lamps, cathode ray tubes and lasers.

EP-A-0 265 983 generally claims a luminescent glass consisting of a matrix formed from SiO2 and from 0 to 0.15 moles of MO per mole of SiO2, where MO is at least one of the oxides Au203, B203 , P2O5, ZrO2, Suc203, Y203, La2O3, Gd2O3, Ln2O3,
ZnO, alkaline and alkaline earth oxides, and at least one of the activating oxides Tb203 and Ce203 in a proportion of 0.75 to 15 mole% relative to the matrix. No glass containing P2O5 is specifically illustrated. These glasses are described as being useful in particular in discharge lamps.

Detailed description of the invention
The description which will follow, given with reference to the drawings, will make the invention clearly understood. On the drawings
Figure 1 is a graph showing the erythemal CIE action spectrum compared to the spectral response of polysulfone (PSF).

Figure 2 is a schematic view of a dosimeter with
UV according to the invention.

Figure 3 is a graph illustrating the transmission spectra of the color filters used in the dosimeter of Figure 2.

Figures 4a and 4b are graphs illustrating the spectral sensitivity (Figure 4a) and the luminescence spectrum of a slide, 0.5 mm thick, of a photoluminescent glass whose composition (outside the invention ) is, in cationic%: 25% La203, 74.9% P205 and 0.11% Ce2O3.

FIG. 5 is a graph illustrating the spectral responses of three sensors according to the invention and the erythemal CIE action spectrum, and
FIG. 6 is a graph illustrating the photoresponse curve of a UV sensor according to the invention as a function of the UV irradiation dose at a wavelength of 315 nm.

In FIG. 1 which represents the erythemal CIE action spectrum compared to the spectral response of the polysulfone (PSF), it can be seen that the polysulfone (PSF) gives a response which only very imperfectly follows the erythemal action spectrum.

In Figure 2 is schematically illustrated a UV dosimeter according to the invention.

This dosimeter includes a UV sensor and a photodetector. The UV sensor consists of
- a photoluminescent glass slide 3 which converts incident UV radiation into visible light, and
- colored filters (1, 2, 4) of commercial origin and listed in the catalog "Color Optical Glass and
Special Glasses, Moscow, House of Optics, 1990 ", whose characteristic transmission spectra are shown in Figure 3. The function of these filters is to filter UV radiation and visible light and to refine the spectral response of the sensor for that it coincides with the erythemal action spectrum defined in Figure 1.

The luminescent glass slide should be thin, typically between 0.05 and 0.5mm, preferably 0.1 to 0.2mm in order to minimize any unwanted absorption due to impurities such as Ce3 iron *) normally present in glasses.

The principle of operation is as follows. The filter 1 allows only the transmission of the ultraviolet part of the incident radiation. In particular, the spectral range between 250 and 390 nm is transmitted without distortion, as shown in figure 3. The UV radiation thus transmitted excites the luminescence of the glass of the slide 3. An essential characteristic of the present sensor is that the intensity of luminescence is directly proportional to the irradiance, Eeff, of the incident UV source. The function of filter 4 is to filter all spectral contributions except the luminescence band of interest, centered at 550 nm, which is then transmitted to photodetector 5. Filter 2 corrects, if necessary, the action spectrum of the sensor. photoluminescent, in order to optimize its agreement with the reference spectrum.

où K est un coefficient de calibration. Cette intégration est facilement réalisée par des circuits électroniques classiques couplés à une photodiode.The photodetector records luminescence, the intensity of which, I, is proportional to the power of the actinic dose of the incident UV radiation, Eeff. The UV exposure dose is given by the expression

where K is a calibration coefficient. This integration is easily achieved by conventional electronic circuits coupled to a photodiode.

The key element of the UV sensor is the luminescent glass slide. We have discovered that the best luminescence characteristics are obtained with glasses containing P2O5, Tb203 and Ce203 and satisfying the above-defined concentration conditions which must be observed to obtain the luminescence properties suitable for the application envisaged.

The simultaneous presence of Ce2O3 and Tub203, next to P205, in the glass has been shown to be critical for obtaining said properties. Glasses comprising P205 and Ce203 but no Tb203 have also been tried but have been found to be unsatisfactory. By way of comparison, a UV sensor has been produced based on such a glass consisting of 75% of P2O5 and 25% of La203 and doped with 0.2% of Ce203.

However, as shown in Figure 4a, the action spectrum of such a UV sensor is located in the spectral range between 280 and 340 nm. FIG. 4b illustrates the luminescence spectrum of the same glass and emphasizes the small amplitude of the Stokes shift between the excitation spectrum and the emission spectrum. Glass doped with
Ce203 alone is therefore not suitable for the envisaged application, for which the target spectral sensitivity range is 280 to 400 nm, accompanied by a separate visible luminescence.

As a result of the research carried out, it was found that it was also necessary to add terbium oxide to the glass composition. The result of the co-doping of the glass with Ce3 + and Tb3 + ions is a significant increase in the sensitivity spectrum of the UV sensor, as well as the possibility of making this sensitivity coincide with the reference erythemal action spectrum. Co-doping with
Ce3 + and Tb3 + from glasses containing phosphorus leads to a greater Stokes shift in luminescence and to an extended sensitivity range up to 400 nm.

The glasses of the invention have been manufactured in the following manner from suitably mixed conventional raw materials. For example, phosphoric acid and hydrated alumina are suitable sources for the oxides of phosphorus and aluminum. Melting was carried out in glassy carbon crucibles for 4 hours at 1400-1450 "C, under a continuous flow of nitrogen or argon. After the glass was melted, it was poured onto a graphite plate and annealed. at a temperature of the order of 500-600 "C. At the end of this annealing, blades of thickness suitable for the invention were sawn and polished. Thanks to the good luminescence generated by the glasses of the invention, a thickness between 0.1 and 0.2 mm is usually sufficient.

Examples of glass compositions having the desired properties are shown in Table I.

To manufacture a UV sensor having a spectral sensitivity similar to that of human skin, several commercial filters have been used, as explained above. Their spectral characteristics are presented in figure 3. The last component of the assembly is a commercial photodiode (type BPW-21) which has been placed downstream of the assembly shown schematically in figure 2.

The typical spectral responses of three sensors to
W made in this way, from the photoluminescent glasses NO 1 (thickness 0.15mm), 19 (thickness 0.2mm) and 20 (thickness 0.5mm) of Table 1, is compared with the skin sensitivity spectrum human in Figure 5. The agreement between the sensitivity spectrum of human skin and the spectral responses of the first two sensors above is excellent, in particular up to 380 nm, critical spectral range for erythemal action.

We have also determined the characteristics of such a UV sensor in association with a photodiode making it possible to detect the luminescent signal. The combination of luminescent glass (see curve 3 in figure 5) with colored filters (see figure 3) and a BPW-21 photodiode ensures the linear dependence of the photoresponse as a function of the incident UV radiation in a covering domain. at least three orders of magnitude (see figure 6).

The lower limit of detection of the present sensor, in terms of irradiation dose (Heff), is of the order of 2 * 10-4 kJm-2. This sensitivity is greater by a factor of 10,000 than that of polysulfone.

In summary, the new type of UV dosimeter for personal use described in the present invention has the following advantages over commercial dosimeters based on organic film technology.
- direct reading in real time (while having the possibility of analyzing the signal cumulatively);
- essentially the same spectral sensitivity as human skin, as described by the standard erythemal action spectrum
- a linear dependence of the luminescent signal on the incident ultraviolet dose;
- the absence of thermal dependence; and
- a much improved detection threshold.

BOARD

Composition%
<tb> cationic <SEP> 1 <SEP> 2 <SEP> 3 <SEP> 4 <SEP> 5 <SEP> 6 <SEP> 7 <SEP> 8 <SEP> 9 <SEP> 10
<tb> La2O3 <SEP> 19.8 <SEP> 17.8 <SEP> 15.6 <SEP> 13.4 <SEP> 11.0 <SEP> 8.5 <SEP> 17.4 <SEP> 15 , 3 <SEP> 13.1 <SEP> 10.7
<tb> Tb2O3 <SEP> 5.6 <SEP> 5.8 <SEP> 5.9 <SEP> 6.1 <SEP> 6.3 <SEP> 6.5 <SEP> 5.6 <SEP> 5 , 8 <SEP> 6.0 <SEP> 6.1
<tb> CaO <SEP> 0 <SEP> 2.5 <SEP> 5.2 <SEP> 8.0 <SEP> 11.0 <SEP> 14.2 <SEP> 0 <SEP> 12.5 <SEP > 5.2 <SEP> 8.0
<tb> Al2O3 <SEP> 0 <SEP> 0 <SEP> 0 <SEP> 0 <SEP> 0 <SEP> 0 <SEP> 2.5 <SEP> 2.5 <SEP> 2.6 <SEP> 2 , 7
<tb><SEP> P2O5 <SEP> 74.4 <SEP> 73.8 <SEP> 73.1 <SEP> 72.4 <SEP> 71.6 <SEP> 70.8 <SEP> 74.4 <SEP> 73.7 <SEP> 73.1 <SEP> 72.4
<tb> Ce2O3 <SEP> 0.11 <SEP> 0.11 <SEP> 0.11 <SEP> 0.11 <SEP> 0.10 <SEP> 0.10 <SEP> 0.11 <SEP> 0 , 11 <SEP> 0.11 <SEP> 0.11
<tb> TABLE (Continued)

Composition%
<tb> 11 <SEP> 12 <SEP> 13 <SEP> 14 <SEP> 15 <SEP> 16 <SEP> 17 <SEP> 18 <SEP> 19 <SEP> 20 *
cationic <tb>
<tb> La2O3 <SEP> 8.3 <SEP> 5.7 <SEP> 14.9 <SEP> 12.7 <SEP> 10.4 <SEP> 8.0 <SEP> 5.5 <SEP> 2 , 8 <SEP> 14.7 <SEP> 4.9
<tb> Tb2O3 <SEP> 6.3 <SEP> 6.5 <SEP> 5.6 <SEP> 5.8 <SEP> 5.9 <SEP> 6.1 <SEP> 6.3 <SEP> 6 , 5 <SEP> 11.2 <SEP> 22.1
<tb> CaO <SEP> 11.0 <SEP> 14.2 <SEP> 0 <SEP> 2.5 <SEP> 5.2 <SEP> 8.0 <SEP> 11.0 <SEP> 14.2 <SEP> 0 <SEP> 0
<tb> Al2O3 <SEP> 2.8 <SEP> 2.8 <SEP> 5.0 <SEP> 5.1 <SEP> 5.2 <SEP> 5.4 <SEP> 5.5 <SEP> 5 , 7 <SEP> 0 <SEP> 0
<tb><SEP> P2O5 <SEP> 71.6 <SEP> 70.8 <SEP> 74.4 <SEP> 73.8 <SEP> 73.1 <SEP> 72.4 <SEP> 71.6 <SEP> 70.8 <SEP> 73.7 <SEP> 72.9
<tb> Ce2O3 <SEP> 0.10 <SEP> 0.10 <SEP> 0.11 <SEP> 0.10 <SEP> 0.10 <SEP> 0.10 <SEP> 0.10 <SEP> 0 , 10 <SEP> 0.33 <SEP> 0.06
<tb> * outside the invention

Claims (11)

1. UV sensor having a spectral response close to the sensitivity of human skin between 280 and 400 nm, comprising filtering means (1, 2) allowing only incident UV radiation to pass, a plate (3) of photoluminescent material converting UV radiation into visible radiation and a filter (4) allowing only visible luminescence to pass, characterized in that said plate consists of a photoluminescent glass whose composition comprises constituent oxides of glass including P205, and doping oxides consisting of Tb203 and Ce203, with the conditions that the contents of P205, Tb203 and Ce203, expressed in cationic percentages, satisfy the following relationships 0.05 S Ce203 5 0.4 2 <Tb203 <20 P205> 2 (Ce203 + Tub203) 2. Sensor according to claim 1, characterized in that the constituent oxides of glass, other than P205, are chosen from La203, CaO, A1203, SiO2 and B203. 3. Sensor according to claim 1 or 2, characterized in that the constituent oxides of glass, other than P2O5, are La203, CaO and A1203. 4. Sensor according to claim 3, characterized in that the glasses have the following composition, in cationic percentages 65-77 P205 2,5-22 La203 0-7 Al203 0-20 CaO 2-10 Tb203 0.05-0.4 Ce203 5. Sensor according to any one of claims 1 to 4, characterized in that said blade has a thickness of 0.05 to 0.5 mm. 6. Sensor according to claim 5, characterized in.ce that said thickness is from 0.1 to 0.2 mm. 7. UV dosimeter comprising a UV sensor and means for metering the visible radiation emitted by the sensor, characterized in that said sensor is as defined in any one of claims 1 to 6. 8. Photoluminescent glasses converting ultraviolet radiation into visible radiation, characterized in that their composition comprises constituent oxides of glass including P2O5, and doping oxides consisting of Tb203 and Ce203, with the conditions that the contents of P2O5, Tb203 and Ce203, expressed in cationic percentages, satisfy the following relationships 0.05 <Ce203 # 0.4 2 <Tb203 S 20 P205> 2 (Ce203 + Tb2O3). 9. Glasses according to claim 8, characterized in that the constituent oxides of glass, other than P205, are chosen from La2O3, CaO, Al2O3, SiO2 and B203. 10. Glasses according to claim 8 or 9, characterized in that the constituent oxides of glass, other than P2Os, are La2O3, CaO and Al203. 11. Glasses according to claim 10, characterized in that they have the following composition, in cationic percentages 65-77 P205 0-20 CaO 2,5-22 La203 2-10 Tb203 0-7 Al203 0.05-0.4 Ce2O3