Are you familiar with photochromic materials?
Photochromic is a term coined by combining the Greek words “Phos/Photo (light)” and “Chroma (color),” and refers to materials that change not only their color but also their molecular structure when exposed to light.
The most remarkable feature of these materials is that their molecules can switch between transparent and colored states depending on whether they are exposed to light or not. While ordinary materials do not return to their original state once changed, photochromic materials are very unique in that they can “go back and forth (return to their original state).”
A familiar example of a photochromic material for many people is transition lenses in sunglasses (eyeglasses). They become colored when exposed to sunlight, and lose their color when the light disappears (or diminishes).
The light spectrum that triggers photochromic reactions is primarily ultraviolet light.
When ultraviolet light is irradiated onto photochromic materials, they change their molecular structure into a form that absorbs visible light.
Recently, materials that can react even in the short wavelength range of visible light (violet to blue) have been developed.
This is a countermeasure for the fact that when the windshield of a car has an ultraviolet ray-blocking function, sunglasses no longer undergo a photochromic reaction.
Photochromic materials are already used across a wide range of applications other than sunglasses, such as:
・Printed matter (cards or packages where logos or designs appear under ultraviolet light)
・Parasols and tents (designs that appear when exposed to sunlight)
・Clothing (changes color with ultraviolet light)
And there are many other fields in which they are used. The materials are also widely used in the fashion industry.
Photochromic materials are also used in the UV check cards that change color when exposed to ultraviolet light and are used to check the presence or absence of UV rays. These cards can be used repeatedly, as their color returns to its original state when ultraviolet rays are blocked, making reusability one of their key features. They are available even at 100-yen shops, so please purchase one and try it yourself if you are interested.
Our artificial solar lighting includes a lineup of filters that let ultraviolet light through, and artificial solar lighting with B/BF and L/LF filters is used for evaluation.
To evaluate materials, first measure the ultraviolet intensity of the surface to be irradiated, and then assess the following properties:
・Speed at which the color changes
・Color after the change
・The amount of change in opacity after the color changes, for transparent products
・Speed at which they return to the original state when ultraviolet rays are blocked
For these measurements, stable ultraviolet irradiation is essential, and that is why artificial solar lighting is used.
Since the evaluation method for spectacle lenses is specified in the JIS standard, test equipment other than a light source is also required. Temperature control in particular is an important factor, as the speed of change often varies depending on the temperature. Therefore, it is necessary to conduct tests in which light is irradiated while controlling the temperature and humidity in a chamber in which temperature and humidity are constant.
The main models selected by users are:
・Artificial solar lighting 500W series: XG-500B/BF or XG-500L/LF
・Artificial solar lighting 100W series: XG-100B/BF or XG-100L/LF
・Super spotlight artificial solar lighting (if the same ultraviolet intensity as natural sunlight is required): XG-100BFSS/LFSS, XG-500BFSS/LFSS
For accurate data measurement, the 500W super spotlight lighting type XG-500BFSS is recommended. It can irradiate an area of φ10 cm with the same irradiation intensity as natural sunlight. Also, if you want to verify the influences of both ultraviolet and infrared light and the effectiveness of the material, we recommend the XG-500LFSS.
The recommended application varies depending on the XELIOS 100W Series/ or XELIOS 500W Series and the type of filter used.
The detailed relationship between recommended applications and models is as follows.
| When you want to uniformly irradiate an area of φ10 cm and measure accurate data | XG-500BFSS |
| When you want to uniformly irradiate an area of φ10 cm and simultaneously measure the influences of heat and the effectiveness of the material | XG-500LFSS |
| When you want to measure an area of φ2–3 cm with the same amount of ultraviolet rays as direct sunlight | XG-100BFSS |
| When you want to measure an area of φ2–3 cm with an ultraviolet dose equivalent to direct sunlight, while simultaneously measuring the influence of heat and the effectiveness of the material | XG-100LFSS |
| When you want to assess a workpiece of approximately postcard size for the relationship between the state of change and color, and visually inspect the color after the change | XG-100B/BF |
| When you want to assess a workpiece of approximately postcard size for the relationship between the state of change and color, and reproduce the state in which the influence of heat is added to the color after change | XG-100L/LF |
| When you want to assess a workpiece of approximately A4 to A3 size for the relationship between the state of change and color, and visually inspect the color after the change | XG-500B/BF |
| When you want to assess a workpiece of approximately A4 to A3 size for the relationship between the state of change and color, and reproduce the state in which the influence of heat is added to the color after the change | XG-500L/LF |
The market for photochromic materials is expanding steadily and has already reached a scale of 200 billion yen. The market is also expected to more than double in size over the next 10 years, and the use of photochromic materials is advancing in a variety of fields.
In the evaluation of photochromic materials, results are greatly affected by irradiation conditions and the environment, which makes it important to select an appropriate light source and evaluation environment that are suited to the purpose of evaluation. Artificial solar lighting has been adopted by a broad range of customers to replicate these evaluation environments.
If you are considering product differentiation using photochromic materials, new market entry, or measuring sales promotion data, please feel free to contact our experienced team. We will propose the equipment best suited to your needs.
Please refer to the following pages for the specifications and performance of artificial solar lighting.
・Artificial Solar Lighting – XELIOS 500W Series
・Artificial Solar Lighting – XELIOS 100W Series
・Artificial concentrating-type solar lighting (super spotlight type) capable of producing 1sun (1,000 W/m2) or 100,000 Lx
