Radiant energy – Invisible radiation responsive nonelectric signalling – Optical change type
Reexamination Certificate
1999-05-03
2001-09-25
Hannaher, Constantine (Department: 2878)
Radiant energy
Invisible radiation responsive nonelectric signalling
Optical change type
C250S482100
Reexamination Certificate
active
06294792
ABSTRACT:
The subject of the invention is a UV dosimeter suitable for visual evaluation and a procedure for its production.
About 5% of the sunshine reaching the earth-surface is ultraviolet (UV) radiation (200-400 nm). The UV radiation has both favourable and unfavourable, moreover harmful effect on the human body. Harmfull consequences are detectable either immediately after the radiation, or even some decades later. Since the biological effect strongly depends on the wavelength, thus the whole UV spectrum is usually divided into three regions, such as UVA, UVB and UVC spectra. The UVB radiation (290-320 nm) is responsible for the major biological effects and also for the harmful consequences.
As a biological effect on the human body the UV light has an influence on the skin, eyes and the immune system. Among the early acute damages there are the dermatitis, conjunctivitis, keratitis, the delayed damages include the early skin ageing, skin cancer, exacerbation of skin diseases, cataract formation, weakening of the body's prophylactic mechanism, susceptibility to skin infection and skin cancer.
The simplest way of the protection or the prevention against the harmful consequence of the UV irradiation is to measure the intensity of the irradiation and to expose the skin to the solar radiation (UV radiation) only as much extent as the exposure dose is even harmless.
The chemical actinometers being appropriate for personal use are the simplest UV dosimeters. Their operation is based upon the analysis of the effect of the chemical reaction (or reactions) initiated by a light irradiation, which need the quantitative analysis of the starting substance(s) or the product(s) (H. J. Khun, S. E. Braslavsky, R. Schmidt: Chemical Actinometry, Pure and Appl. Chem., Vol.61, No2, pp 187-210, 1989). Since generally the evaluation is done by a spectrophotometer, these dosimeters are not convenient for a simple or multitudinous application.
For a self-checking device the most suitable dosimeter is a simple and easily utilizable dosimeter, which is implemented on a visually evaluable solid carrier, which is disposable and does not pollute the environment.
The device suitable for the above purposes should fulfil the following requirements:
the light-sensitive layer should be sensitive enough in the UVB range of the sunlight,
the colour change (density) should be proportional to the dose of the light irradiated the photosensitive layer,
the density should be visually evaluable within 1 minute and 1-2 hours interval, i.e. the “density curve” being characteristic of the system should have a linear section with a specific angular coefficient,
the photoinduced reaction should be irreversible id est non-reversible, i.e. the quantity of the density being proportional to the quantity of the irradiated light should be constant both in the function of time and in dark even if later it is exposed by a light with longer wavelength, then the detecting light wavelength.
Several reactions are known, which are effected by light and which result in a visually detectable colour change. However for some reasons these reactions are not convenient for the analysis of the doses of the UVB radiation. The reasons are, that first of all those are sensitive also in the visible light range and consequently those are not selective in the UVB range, furthermore the reaction is reversible and consequently if it is left in dark the irradiated layer is lightened and the evaluation become impossible.
Among the ultraviolet dosimeters being suitable for personal use the polisulphon film dosimeters are considered as the most updated devices. [Davis, A., Deane, G. H. W. and Diffey, B. L.: Possible dosimeter . . . , Nature 261 169-170 (1976)]. The polisulphon film dosimeter is carrier coated by a polisulphon layer with 40 &mgr;m thickness, which is applicable in the range of 250-330 nm. Its disadvantage is, that the application is awkwardish difficult, since its evaluation can be carried out by means of an instrument.
In accordance to the above a visually evaluable UV dosimeter indicator is presented by the Hungarian patent no. 208 865, which light-sensitive layer consists of mercuric (I), mercuric (II) and argentic-oxalate. The bulky application of the indicator is not convenient, since by the application of the disposable light-sensitive layer the environment could be polluted with mercuric salts.
Our aim was to develop a UV dosimeter, which both corresponds to the above requirements and even does not pollute the environment. According to the literature one of the best known chemical actinometers is the sulphuric acid solution of the potassium tris-oxalic ferric (III) complex (H. J. Khun at al: Pure & Appl. Chem. 61, 187 (1989). The tris-oxalic ferric (III) anion is degraded in a fotoreduction procedure as it is labelled in the gross reaction equation no. 1:
2
Fe
(
C
2
O
4
)
2
3
-
=
hv
2
Fe
2
+
+
5
C
2
O
4
2
-
+
2
CO
2
By reacting ferro (II) ions obtained in the photoreduction process with an appropriate complex forming agent e.g. orthophenan-throline (further on: phen) as it is labelled in the equation no. 2, a characteristic ruddy trisphenanthroline ferro (II) complex is formed which molar absorbance is considerably high (1.1×10
4
M
−1
cm
−1
), consequently it is now convenient for the detection of the photoreduction process.
Fe
2+
+3(phen)=Fe (phen)
3
2+
This actinometer operates in the wavelength range of 250-580 nm (A. J. Gordon, R. A. Ford: The Chemist's Companion, A Handbook of Practical Data, Techniques and References; John Wiley Sons, New York p 362). Since this range is too wide and overreach even into the visible light range, this device is not convenient for the selective measurement of the UV radiation doses.
A further problem is, that since the tris-oxalic ferric (III) salt is highly soluble in water, the diffusion rate in the carrier layer of the dosimeter is considerably high, consequently after the irradiation the system does not remain constant and the obtained colour change is not evaluable.
The invention is based on the recognition, that the above mentioned problems can be discarded, when the light-sensitive layer contains not only the ferric (III) oxalate complex alone but as a light-sensitive system it contains the argentic (I) oxalate as well, moreover the ferro (II) oxalate complex is produced within the light-sensitive system. In this case the ferric (III) ions are chemisorbed on the surface of the argentic (I) oxalate being precipitated in solid form and a multinuclear argentic (I) oxalate-ferric (III) oxalate complexes are formed, which adequately stabilise the system in order to obtain as a result of the irradiation a constant and evaluable coloration (browning).
In the above light-sensitive system and in the presence of argentic (I) oxalate the Fe
2+
ions being formed in the first stage of the photoreduction are reoxidized by the argentic (I) ions to Fe
3+
ions (
3
). According as the quantity of the efficient photons reaching the emulsion is high enough, then the previous nearly white layer irreversibly turns to brown. The browning becomes the degree of its generating light dosage.
Fe
2+
+Ag
+
=Fe
3+
+Ag
The subject of the invention is a UV dosimeter, which consists of a layer containing the above light sensitive system being applied on an appropriate carrier and an upper layer.
The concentration of the light-sensitive layer forming suspension is 95-105 g/dm
3
and calculated to the volume of the suspension it contains in a water bloated high molecular weight polymer amenable to hardening preferably in gelatine 0.004 to 0.2 mole/dm
3
of argentic (I) salt, 0.0014 to 0.07 mole/dm
3
of water soluble multivalent metallic salt, free dicarboxylic acid in maximum equivalent quantity relative to the argentic (I) ions and 0.00044 to 0.006 mole/dm
3
of complexing additive.
Beside the ferric (III) ions e.g. cobaltic (III) and nickelic (III) ions are also suitable for the
Bazsa György
Beck Mihály
Fazekas Zsolt
Fleischinger Vincze Zsuzsanna Györgyné
Horkay Irén
Hannaher Constantine
Israel Andrew
Keil & Weinkauf
Kossuth Lajos Tudomanyegyetem
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