An apparatus for artificial exposure containing two light sources

Abstract

To solve the problem that a xenon lamp used as a radiation source in conventional exposure testers must be prevented from overheating a sample and has a life of only about 1500 hours.SOLUTION: A device 10 for artificial exposure or light fastness testing of a sample 3, comprises: an exposure chamber 1; a first light source 4.1 provided in the exposure chamber 1, where the first light source 4.1 comprises one or more fluorescent UV lamps each comprising a light emitting spectrum having a maximum wavelength less than a predetermined wavelength; and a second light source 4.2 provided in the exposure chamber 1, where the second light source 4.2 comprises one or more light emitting diodes 4.2 each comprising a light emitting spectrum having a maximum wavelength exceeding the predetermined wavelength.SELECTED DRAWING: Figure 1A

Description

[Technical field]

[0001] The present disclosure relates to an apparatus for artificial exposure, or for lightfastness testing, which comprises two types of light sources, the first of which comprises a fluorescent UV lamp and the second of which comprises one or more light emitting diodes. [Background technology]

[0002] Artificial exposure or solar simulator devices are intended to estimate the lifetime of materials that are constantly exposed to natural weather conditions during their use and are therefore subject to climatic influences such as sunlight, solar heat, moisture, etc. In order to obtain a good simulation of natural exposure conditions, the spectral energy distribution of the light generated in the device should correspond as much as possible to the spectral energy distribution of natural solar radiation, for that reason xenon radiators are used as radiation sources in such devices. Accelerated aging tests of materials are essentially achieved by a much more intense irradiation of the sample compared to natural conditions, which speeds up the aging of the sample. In this way, predictions of the long-term aging of material samples can be made after a relatively short time.

[0003] A large number of the samples studied in the artificial exposure apparatus consist of polymeric materials. Their degradation upon exposure is essentially caused by the UV component of solar radiation. The main photochemical processes that occur during this time, namely the absorption of photons and the generation of excited states or free radicals, are temperature independent. However, subsequent reaction steps with polymers or additives may be temperature dependent, so that the observed aging of the material is also temperature dependent.

[0004] Prior art exposure testers usually use xenon lamps as radiation sources. It is known that such lamps can simulate the solar spectrum very well, but nevertheless the emitted radiation has a relatively high spectral content in the infrared spectral range, which needs to be suppressed by filters to prevent excessive heating of the sample. Moreover, commercially available xenon radiation sources have a lifetime of only about 1500 hours.

[0005] For these and other reasons, there is a need for the present disclosure. Summary of the Invention [Means for solving the problem]

[0006] One aspect of the present disclosure relates to an apparatus for artificial exposure or light fastness testing of samples, the apparatus comprising an exposure chamber, a first light source disposed within the exposure chamber and including one or more fluorescent UV lamps each having an emission spectrum with a maximum wavelength less than a predetermined wavelength, and a second light source disposed within the exposure chamber and including one or more light emitting diodes, each of the light emitting diodes having an emission spectrum with a maximum wavelength greater than a predetermined wavelength.

[0007] The predetermined wavelength can be, for example, 360 nm, since there are currently no satisfactorily operating LEDs available below 360 nm. Thus, the fluorescent lamp is intended to fill a gap that LEDs cannot cover. However, depending on the available LEDs, the cut-over between the two types of UV sources may be another wavelength, for example, 350 nm or 380 nm. [Brief description of the drawings]

[0008] The accompanying drawings are included to provide a further understanding of the aspects, and are incorporated in and constitute a part of this specification. The drawings illustrate the aspects and, together with the description, serve to explain the principles of the aspects. Other aspects and many of the intended advantages of the aspects will be readily appreciated, as better understood by reference to the following detailed description. Elements of the drawings are not necessarily to scale relative to each other. Like reference characters may indicate corresponding like parts.

[0009] The present disclosure is explained in more detail below with reference to exemplary embodiments in conjunction with the drawings. [Figure 1A] 1 shows a horizontal cross-sectional down view of an example of an apparatus for artificial exposure, the apparatus being of the dynamic type with a rotating sample. [Figure 1B] FIG. 1 is a perspective view of a radiation module comprising an LED and a fluorescent lamp. [Figure 1C] FIG. 2 is a cross-sectional view of a radiation module with an LED and a fluorescent lamp. [Figure 2A] 1 shows a vertical cross-sectional view of an apparatus for artificial exposure according to the present disclosure, the apparatus being of a static type with a fixed sample. [Figure 2B] 2B is a bottom view of the radiation module at line BB in FIG. 2A. [Figure 3A] 1 is a wavelength-intensity diagram showing the spectrum of natural sunlight along with the overlaid emission curves of several LEDs. [Figure 3B] A wavelength intensity diagram showing the spectrum of natural sunlight with the short wavelengths expanded, along with the emission curve of a fluorescent UV lamp, as well as the overlaid emission curves of several LEDs. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] The accompanying drawings are included to provide a further understanding of the aspects, and are incorporated in and constitute a part of this specification. The drawings illustrate the aspects and, together with the description, serve to explain the principles of the aspects. Other aspects and many of the intended advantages of the aspects will be readily appreciated, as better understood by reference to the following detailed description. Elements of the drawings are not necessarily to scale relative to each other. Like reference characters may indicate corresponding like parts.

[0011] In the following detailed description, reference is made to the accompanying drawings which show, by way of example, specific embodiments in which the present disclosure may be practiced. In this regard, directional terms such as "top," "bottom," "front," "back," and the like may be used with reference to the orientation of the drawings being described. Because components of the described devices may be arranged in many different orientations, the directional terms may be used for purposes of illustration and are in no way limiting. Other embodiments may be utilized and structural or logical changes may be made without departing from the concept of the present disclosure. Therefore, the following detailed description is not to be taken in a limiting sense, and the concept of the present disclosure is defined by the appended claims.

[0012] Furthermore, while a particular example feature or aspect may be disclosed with respect to only one of several implementations, such feature or aspect may be combined with one or more other features or aspects of other implementations as may be desirable and advantageous for any given or particular application. Moreover, to the extent that the terms "include," "have," "with," or other variations thereof are used in either the detailed description or the claims, such terms are intended to be inclusive in a manner similar to the term "comprise." The terms "coupled" and "connected" may be used with their derivatives. These terms may be used to indicate that two elements or layers cooperate or interact with each other, regardless of whether they are in direct physical or electrical contact, or that they are not in direct contact with each other, meaning that there may be one or more intermediate elements disposed between them. Also, the term "exemplary" is meant merely as an example, not as best or optimal. Thus, the following detailed description should not be taken in a limiting sense, and the scope of the present disclosure is defined by the appended claims.

[0013] FIG. 1, which comprises FIGS. 1A-1B, shows an apparatus according to the present disclosure for artificial exposure of a sample (A), and a radiation module (B, C) for use in such an apparatus.

[0014] The apparatus 10 of Figure 1 comprises an exposure chamber 1 and a holding frame 2 mounted for rotation within the exposure chamber 1. The holding frame 2 has a closed ring shape and the sample 3 or workpiece can be held on a suitable holding platform or socket provided in the holding frame 2. The holding frame 2 can in particular have a cylindrical form and a circular cross section.

[0015] The device 10 of Fig. 1 further comprises a radiation module 4 including a first light source 4.1 in the form of a fluorescent UV lamp 4.1. The fluorescent UV lamp 4.1 may have an emission spectrum with a maximum wavelength of less than 360 nm. The device 10 of Fig. 1 further comprises a second light source 4.2 in the form of a number of light emitting diodes (LEDs) 4.2. The LEDs 4.2 may each have an emission spectrum with a maximum wavelength of more than 360 nm. In particular, the LEDs 4.2 may be spectrally arranged in a number of different spectra from 360 nm to 1100 nm or even higher.

[0016] The fluorescent UV lamps 4.1 may be of the same type and have nominally identical emission spectra.

[0017] The fluorescent UV lamp 4.1 can have, for example, an emission spectrum in the UV-A range, for example a maximum emission wavelength of 351 nm or 340 nm. The fluorescent UV lamp 4.1 may alternatively comprise an emission spectrum in the UV-B range, for example with a maximum emission wavelength of 313 nm. It is also possible to use two or more fluorescent UV lamps with different emission spectra, for example as two or more lamps each comprising one of the emission spectra mentioned above.

[0018] The fluorescent UV lamp 4.1 may comprise a mercury vapor lamp, in particular a low-pressure mercury vapor lamp. More specifically, the fluorescent UV lamp 4.1 may comprise a glass or quartz bulb filled with mercury vapor. The pressure inside the lamp may be around 0.3% of atmospheric pressure. The bulb may also be filled with another gas, in particular one of argon, xenon, neon or krypton, or a mixture between at least two of these gases, possibly together with mercury. In the operation of the lamp, it is important that the excited gas is able to emit at least one strong UV ray having a wavelength of less than 300 nm.

[0019] The inner surface of the bulb is coated with a phosphorescent coating consisting of various blends of metal and rare earth phosphor salts. The spectrum of light emitted from a fluorescent lamp is a combination of the light emitted directly by the mercury vapor and the light emitted by the phosphorescent coating. For the purposes of this disclosure, it is important to select phosphorescent salts capable of emitting a fluorescent spectrum that is spectrally located on the shortwave UV rising edge of the solar spectrum, as will be shown in more detail below.

[0020] 1B and 1C, the radiation module 4 further comprises a hollow glass or quartz cylinder 4.3, on whose inner surface the fluorescent lamps 4.1 and the LEDs 4.2 are mounted. The glass or quartz cylinder 4.3 serves the purpose of protecting the light sources from humidity and possibly filtering the light / radiation to a required spectral distribution.

[0021] As mentioned above, the LEDs 4.2 can include different emission spectra, such that the superimposed spectrum of the fluorescent UV lamp 4.1 and the LEDs 4.2 approximates the spectrum of sunlight. The LEDs 4.2 can include any desired number of different emission spectra, for example 4 to 10 or even more different emission spectra. The LEDs 4.2 can be electrically connected in series. However, it is also possible to power each emission type of the LEDs 4.2 individually, so that the superimposed spectrum can be adapted to individual requirements.

[0022] FIG. 3 shows a wavelength-intensity diagram to illustrate a simulation of the solar spectrum in the visible and infrared range (A) and also in the UV range (B).

[0023] The wavelength-intensity diagram in FIG. 3A shows the spectrum of natural sunlight (solid line) with the superimposed emission curves of the LEDs (dashed line). It can be clearly seen that the LEDs cover only the wavelength range above 360 ​​nm up to a wavelength of 750 nm. Additional LEDs can be employed to match the solar spectrum to 1100 nm or even higher. Due to the fact that LEDs below 360 nm are not employed, there is a UV gap between 295 nm and 350 nm.

[0024] The wavelength-intensity diagram of Figure 3B shows how this UV gap is filled. Figure 3B shows an enlarged short-wavelength portion of the diagram of Figure 3A, and further shows the emission curve of a fluorescent UV lamp (dotted line) whose emission curve contains a maximum at about 340 nm, thus completely filling the UV gap between 295 and 350 nm. At the falling edge of the emission curve, it can be seen that the UV-LEDs are spectrally arranged with a maximum at 367 nm, and that with increasing wavelength, more LEDs are employed to approximate at least a portion of the solar spectrum.

[0025] Thus, the superposition curve of the LED curve and the UV fluorescent curve may be such that it best approximates the natural sunlight curve. The approximation can be defined mathematically by calculating the integral, i.e. the area under the curve, of both the superposition curve and the natural sunlight curve between two wavelength values, e.g. 300 nm and 500 nm, 600 nm, 700 nm, 800 nm, or 900 nm, and then calculating the difference between both area values. In this case, the maximum value of the difference can be defined as, e.g., 20%, 10%, or 5% of the higher value of the two area values. If the difference value is less than this maximum, it is known that the superposition curve satisfactorily approximates the natural sunlight curve.

[0026] In a manner known per se, the exposure chamber 1 can also have other artificial exposure equipment, such as moisture generators, but these do not play an essential role in the present disclosure and will therefore not be described in detail. As an example only for generating condensation, a heated reservoir at the bottom of the exposure chamber can generate water vapor that rises to the upper chamber where the sample is exposed to UV radiation and is uniformly moistened with 100% relative humidity. As another example, an air stream can be blown into the exposure chamber 1 and past the sample 3.

[0027] FIG. 2, which comprises FIGS. 2A and 2B, shows an example of a static-type artificial exposure apparatus with a fixed sample (A) and a view onto the radiation module attached to the exposure apparatus (B).

[0028] As shown in Figure 2, the apparatus 20 for artificial exposure includes an exposure chamber 21 configured to allow placement of a plurality of samples 23 or workpieces on a bottom surface of the exposure chamber 21. The apparatus 20 of Figure 2 further includes a radiation module 24 having a fluorescent lamp 24.1 and an LED 24.2. Similar to Figures 1B and 1C, the fluorescent lamp 24.1 and the LED 24.2 may be mounted on a glass or quartz plate mounted between opposing inner walls of the exposure chamber 21.

[0029] Apparatus 20 may include further features similar to those already described in relation to apparatus 10 of FIG.

[0030] Although the present disclosure has been shown and described with respect to one or more implementations, equivalent variations and modifications will occur to those skilled in the art based at least in part on reading and understanding this specification and the accompanying drawings. The present disclosure includes all such modifications and variations, and is limited only by the scope of the following claims. In particular, with respect to the various functions performed by the above-mentioned components (e.g., elements, resources, etc.), the terms used to describe such components are intended to correspond to any components that perform the specified function (e.g., functionally equivalent) of the described components, unless otherwise indicated, even if they are not structurally equivalent to the disclosed structures that perform the functions in the exemplary implementations of the present disclosure shown herein. In addition, although certain features of the present disclosure are disclosed with respect to only one of several implementations, such features can be combined with one or more other features of other implementations, as may be desired and advantageous for any given or specific application.

Claims

1. An apparatus (10; 20) for artificial exposure or lightfastness testing of a sample (3; 23), comprising An exposure chamber (1;21); a first light source (4.1; 24.1) provided in said exposure chamber (1; 21), said first light source (4.1; 24.1) comprising one or more fluorescent UV lamps (4.1; 24.1), each of which comprises an emission spectrum with a maximum wavelength of less than 360 nm; a second light source (4.2; 24.2) provided in said exposure chamber (1; 21), said second light source (4.2; 24.2) comprising one or more light emitting diodes (4.2; 24.2) each comprising an emission spectrum with a maximum wavelength greater than 360 nm, the fluorescent UV lamp of the first light source comprises a glass or quartz bulb filled with mercury vapor, the inner surface of the bulb being coated with a fluorescent salt, whereby the fluorescent UV lamp is capable of emitting a fluorescent spectrum that is spectrally located at the shortwave UV rising edge of the sunlight spectrum; The device (10; 20), wherein the first light source interpolates the shortwave UV gap of the second light source, such that a superposition of the emission spectra of the first and second light sources (4.1, 4.2; 24.1, 24.2) approximates the solar spectrum.

2. 2. An apparatus (10; 20) according to claim 1, comprising two or more fluorescent UV lamps (4.1; 24.1) with nominally equal emission spectra.

3. 3. Apparatus (10; 20) according to any one of claims 1 or 2, wherein the second light source (4.2; 24.2) comprises one or more light emitting diodes with an emission spectrum in the visible and / or infrared range.

4. 4. The device (10; 20) according to claim 3, wherein the superposition of the emission spectra of the first and second light sources (4.1, 4.2; 24.1, 24.2) approximates at least a part of the visible and infrared regions of the solar spectrum.

5. 2. The apparatus (10; 20) of claim 1, wherein the one or more fluorescent UV lamps (4.1; 24.1) comprise one or more of a mercury lamp, a mercury low pressure lamp, or a metal halide lamp.

6. 2. The apparatus (10) of claim 1, wherein the apparatus (10) is configured to rotate the sample (3) around the first and second light sources (4.1, 4.2).

7. 7. The apparatus (10) according to claim 6, wherein the first and second light sources (4.1, 4.2) are mounted on the inner wall of a hollow glass or quartz cylinder (4.3).

8. The apparatus (20) of claim 1, wherein the apparatus (20) is configured to position the sample (23) stationary.

9. 9. The apparatus (20) according to claim 8, wherein the first and second light sources (24.1, 24.2) are attached to a surface of a glass or quartz plate.

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