DE102007041395A1 - UV dosimeter with self-supply and warning signal (display) - Google Patents

Abstract

thin, flexible and affordable UV dosimeter which absorbed the Dose as a function of irradiation and time as measured value indicates and / or after reaching a certain dose, a warning signal gives off, characterized in that it without additional Power supply manages that on a thin, flexible Carrier material is made that it consists of at least a solar cell, a capacitor, a transistor circuit and a signal generator and / or a display and that all components be produced in thin film technology.

Description

The The invention relates to a thin, flexible and inexpensive UV dosimeter which depends on reaching a certain dose of irradiation and time either indicates a value and / or a Gives warning signal. The dosimeter works without additional Power source, such. B. batteries.

[State of the art]

Known UV dosimeters are often based on photochromic layers, which change their color when irradiated. Such dosimeters can be cheap as disposable items in the form of small test strips getting produced. But they contain no warning function or quantitative Measurement.

In the case of purely visual evaluation, practically only a qualitative statement is obtained by comparison with a reference color scale. By means of photometric evaluation, one also obtains quantitative statements, but this requires an additional measuring procedure with a suitable measuring device. For dose determination in radiation-curing processes in the printing and coating industry, this system is offered by Hönle AG under the name UV Scan. However, this is more of a hindrance, especially for portable applications in the leisure sector (eg outdoor activities) or in occupational safety in exposed environments (construction sites, agriculture). Known electronic dosimeters are based on a UV-sensitive component, such. B. a photodiode. This is part of an electronic circuit that integrates the charge generated by the UV sensor over the measurement time and finally displays the measured dose. Examples can be found in US 4428050 . US 3710115 . DE 4012984 and DE 4317405 , where the information about the circuits are different in detail. In addition or as an alternative to the measured value display, the dosimeters can still be provided with an optical or acoustic warning function, which is activated when a specific nominal value is reached ( US 4428050 . US 3710115 . DE 4317405 ). These circuits are constructed with discrete components and are therefore not arbitrarily compact and inexpensive to manufacture. In addition, they require a power supply (mains connection, battery or similar).

In WO8603319 we describe an energy self-sufficient circuit for an electronic UV dosimeter with an electro-acoustic warning function. The circuit includes an optical sensor, resistors, capacitors, a preamplifier, a comparator, switches, diodes, a piezo-transducer and a solar cell for power supply. For the production of the circuit no information is given. The circuit is located in a housing with window and is therefore also not thin, flexible and not really cheap.

Another solution describes WO 0118510 where the dosimeter is integrated into a wristwatch. The disadvantage here is that you would have to acquire a suitably equipped wristwatch for dose measurement.

OBJECT OF THE INVENTION

The The invention relates to a dosimeter for determining the dose of UV rays, which acts on a person or an object. This is z. B. Of importance when sunbathing under natural or artificial Sunlight, other leisure or work activities outdoors or in engineering processes where UV-curing Materials are processed.

task The invention is a simple, small, lightweight, flexible and inexpensive UV dosimeter for mobile use too create, which manages without additional power supply and displays the dose value or if it exceeds a certain Value gives a warning signal. The aim of the invention is ultimately the advantages of a photochromic test strip (compact, flexible, inexpensive) with those of an electronic dosimeter (integrated alarm function or display of a measured value). The invention UV dosimeter can save space in the form of a small test strip attached to the body, clothing or objects become. Due to the low production costs it is for intended for single use.

The Solution of the problem is achieved by the dosimeter as an integrated circuit in thin film technology on one flexible plastic film is present. As a photosensitive element a thin film solar cell is used, which also has one charged in thin-film technology capacitor charges. Thin functional layers according to the invention have Layer thicknesses of approx. 1 μm and below. The total layer thickness a built of several functional layers electronic Component should not exceed 10 microns (without Substrate and encapsulation).

The voltage across the capacitor increases with time as a function of the irradiation. This value can be displayed with a small display, whereby the dose values from the voltage values are determined via a calibration. The display can z. As an OLED (organic light emitting diode) - be an electrochromic or an electrophoretic display, which is also integrated in thin film technology in the film substrate. A drive circuit for the display can by means of Thin-film transistors (TFT) can be realized. In addition to or instead of the display, an electroacoustic or electro-optical component can be integrated which emits a signal when a threshold value is reached. An electro-acoustic signal generator can, for. B. be a thin piezoelectric vibrator, which is excited with an oscillator circuit consisting of thin film transistors. An electro-optical signal generator can, for. B. be a single OLED. In order not to overload the capacitor when operating the signal generator, a thin-film transistor can be inserted to drive the signal generator.

For the power supply of the display or signal generator can be a second Solar cell or a series connection of solar cells (solar module) integrated which, in contrast to the UV-sensitive solar cell also over be sensitive to a wider spectral range can and advantageously also over a larger Area has.

Around a linear dependence of the voltage of irradiation and achieve time, it is beneficial to use the capacitor over to load an operational amplifier. The operational amplifier, which can be realized with thin-film transistors, forms an integrator with the capacitor and a resistor.

The Spectral sensitivity of the solar cell is preferably to be set that it absorbs UV light, but in the visible spectral range insensitive. This can be achieved by appropriate selection of the absorbent semiconductor material which is a large Band gap (greater about 3 eV) have should. Alternatively or in parallel, spectral filters can be used non-relevant parts of the light spectrum are hidden. Farther can be parts of the UV spectrum, in particular from the UV-B range, in which the solar cell is not sufficiently sensitive, converted by fluorescent substances into longer-wave light become.

By suitable dimensioning of the components (solar cell, capacitor, Resistors) can be dosimeters for different measuring ranges or threshold dose values can be realized. In general it is Also required to connect several solar cells in series to the for driving the active components (eg transistors, OLEDs, piezo oscillators, display) necessary tensions.

The required for the production of thin-film components Functional materials (semiconductors, conductors, insulators) can both organic (eg conjugated polymers or oligomers, fullerenes), inorganic nature (metals, transparent conductive oxides (eg. ITO, ZnO)) and also composites of organic and inorganic Be materials. For the production, the known thin film coating and patterning processes such as printing, knife coating, free-fall coating, casting coating, Dip coating, electrode position, coating, vapor deposition (PVD, CVD), sputtering, lithography, laser structuring and the like a. be used. In terms of a low-cost manufacturing such materials and Preferred processes that are highly productive, energy efficient and enable cost-effective production. Especially soluble organic materials in combination with wet coating or printing processes seem particularly suitable.

Of the if necessary, the entire circuit structure is provided by means of transparent high-barrier layers or encapsulated. This is especially necessary when solar cells, OLEDs and TFTs from organic materials are used.

to better adhesion to persons or objects can the The back of the sensor is exposed to an adhesive layer so that the sensor is similar to a patch or an adhesive strip can be used.

example 1

This example shows a variant of the UV sensor consisting of a UV-sensitive solar cell 1 and several solar cells 2 for power supply, a capacitor 4 a resistance 3 , an enhancement field effect transistor 5 and an organic light emitting diode 6 (Image 1 ). All components are produced according to the invention in thin-film technology with organic and / or inorganic functional materials on a flexible base. The first solar cell 1 charges the capacitor 4 , which increases the voltage across the capacitor as the dose increases 4 and at the gate of the transistor 5 grows. The transistor becomes conductive, whereby the voltage drop across the first not yet conductive LED 6 increases. If this voltage drop exceeds the threshold voltage of the light-emitting diode, then this also becomes conductive and starts to light up. A second solar module consisting of a series connection of solar cells 2 , which can also absorb in the visible and infrared spectral range, serves the power supply of the transistor and the OLED. By suitable dimensioning of all components, one can set the dose value at which the LED starts to glow.

Example 2

This example shows a variant of the UV sensor with a linearized characteristic consisting of one or more UV-sensitive solar cells 11 , one or more solar cells 12 to the energy power supply, a capacitor 14 a resistance 13 , an operational amplifier 15 and an organic light emitting diode 16 (Image 2 ). To the operating voltage for the operational amplifier 15 will provide a second solar module 12 consisting of several series-connected solar cells integrated. These solar cells can, in contrast to the UV-sensitive solar cells 11 absorb in a wider spectral range and also have a larger area. The operational amplifier 15 consists of thin-film transistors and passive thin-film components. operational amplifiers 15 , Resistance 13 and capacitor 14 form an integrator whose output voltage increases in proportion to the size and duration of the applied input signal. Exceeds the output voltage at the operational amplifier 15 the threshold voltage of the OLED 16 , it starts to shine.

Example 3

A solar module consisting of five series-connected polymer thin-film solar cells with the photoactive layer poly-3-hexylthiophene / [6,6] -phenyl-C ₆₁ -butyrate (layer thickness? Nm), is connected to a capacitor of capacity 1000 μF. The maximum sensitivity of this solar cell is at a wavelength of 500 nm. Furthermore, the solar module was provided with a UV filter, which only lets wavelengths between 300 nm and 400 nm (maximum at 360 nm). The irradiation was carried out with a standard light source AM 1.5 with an irradiation of 100 mW / cm ² . Due to the filter, only about 4.5 mW / cm ² strike the photoactive layer. The voltage of the capacitor initially increases proportionally with time and finally reaches a saturation value (Fig 3 ).

Example 4

In the construction of Example 3, the capacitor was replaced by a 5 μF capacitor and in addition a 5 MΩ resistor was connected in series. The voltage-time curve is similar to Example 3, but the charge time is significantly reduced until saturation is reached (Fig 4 ).

1

UV-sensitive solar cell

2

solar cell for energy supply

3

resistance

4

capacitor

5

Enhancement field effect transistor

6

organic led

11

UV-sensitive solar cell

12

solar cell for energy supply

13

resistance

14

capacitor

15

operational amplifiers

16

organic led

QUOTES INCLUDE IN THE DESCRIPTION

This list The documents listed by the applicant have been automated generated and is solely for better information recorded by the reader. The list is not part of the German Patent or utility model application. The DPMA takes over no liability for any errors or omissions.

Cited patent literature

• US 4428050 [0003, 0003]
• US 3710115 [0003, 0003]
• - DE 4012984 [0003]
• - DE 4317405 [0003, 0003]
• WO 8603319 [0004]
• WO 0118510 [0005]

Claims (9)

Thin, flexible and inexpensive UV dosimeter which displays the absorbed dose as a function of irradiation and time as a measured value and / or emits a warning signal after reaching a certain dose, characterized in that it requires no additional power supply, that it on a thin, flexible Carrier material is manufactured, that it consists of at least one solar cell, a capacitor, a transistor circuit and a signal generator and / or a display and that all components are manufactured in thin-film technology. UV dosimeter according to claim 1, characterized that the signal transmitter an organic light emitting diode (OLED) or a Piezo oscillator is. UV dosimeter according to claim 1 and 2, characterized that the signal transmitter after reaching a certain dose an acoustic or optical signal. UV dosimeter according to claim 1, characterized that the transistor circuit of one or more transistors and passive components. UV dosimeter according to claim 1 and 4, characterized that by means of the transistor circuit z. B. operational amplifier, Integrators, comparators and a drive circuit for a display can be realized. UV dosimeter according to claim 1, characterized that the display z. As an OLED, electrochromic or electrophoretic Display is. UV dosimeter according to claim 1-6 characterized that the spectral sensitivity of the sensory solar cell up the UV range of the light spectrum is tuned, z. B. by the Choice of photoactive absorber material or an additional spectral filter layer and / or additional fluorescent dyes. UV dosimeter according to claims 1-7 characterized in that that the functional layers with barrier materials against moisture and oxygen are encapsulated. UV dosimeter according to claims 1-8, characterized that the back of the carrier film with an adhesion layer is provided, which allows the UV sensor z. On clothes, to stick to a component or the skin.