Swiss SuperLuminova Episode 3- How Does It Store & Release The Light?

Where We Are In This SuperLuminova Story

This is the third installment of our Swiss SuperLuminova series. Albert Zeller, the CEO of Luminova A.G., and I are going into the details of how Superlumiova works and how it should be applied to watches for the best results.

Just in case you have missed any of the previous episodes, you can catch up on episode one that introduced us to SuperLuminova, what it really is and how dangerous it is or is not.  Episode two is all about emission colors and daylight colors, and the amazing research keeps Superluminova at the forefront of their industry. 

Daniel and I have had a great time working with Luminova A.G., and by working closely with them, we can offer a wide range of luminous options on all our SNGLRTY watches. 

My name is Stephen Mansfield, and I am delighted to join Albert Zeller to explore the technical details of SuperLuminova. We will get into the details, talking about electrons, how this ceramic material stores the light, and knows when to release the light to see our watches glow in the dark. 

SuperLuminova Wiring Diagram

Steve:

How does this ceramic material store light and know when to release the light for us in our watch?

Albert:

You can imagine SuperLuminova as many light storage batteries all accumulated together. Each light storage battery, which stores enough energy for one photon of light, has different energy levels. You can think of energy levels like a skyscraper and the different floors in the skyscraper. There is a ground floor, but there is also a floor higher up, say on the 50th floor. Imagine an electron is like a little balloon; you take the balloon up to the 50th floor by walking up the stairs. Your legs will probably hurt, that is because you had to invest energy to lift the balloon up to the 50th floor.

Electrons Jumping Energy Bands

In SuperLuminova, it works exactly like that. Energy is provided by UV light; this lifts electrons to a higher energy state. This is equivalent to the balloon being on the 50th floor. On the 50th floor, there many different rooms that the balloon can stay in, depending on which room it is in will depend on how the balloon can be released. The same with the electrons. They can jump in between different rooms or energy levels within the atomic structure of the ceramic.

After a certain time, the electrons will fall back down to the ground state. Falling down to the ground state means that the electrons will lose energy. In the case of SuperLuminova, when an electron falls from the higher energy state to the ground state, visible light is emitted by the crystal (light battery).  This means that you apply UV light to charge the crystal. This raises the electrons up to a higher energy level where it can be stored for a certain period of time.  Then, after a certain period of time, the electron will be excited and fall to the ground state and, in the process, emit a photon of visible light.

These Batteries Are Nothing Like Your Phone Battery

Steve:

Does the performance of the Luminova deteriorate over time? For example, my phone has a great battery life when it is new, but over a few years, the battery starts to decline in its performance, and I have to charge it very regularly. Do we have the same problem with Luminova?

Albert:

You can repeat the process of charging and discharging the luminova without limitation. This means that if you gift your grandson your watch, the luminova will have the same performance then as it did on the first day. There is no half-life like radioactive luminous application. Superluminova will have the same performance over the decades.

Bright Luminova – It All Depends On The Charge

Steve:

Okay, the Luminova needs to be charged with a light source. What is the best light source to ensure we get the best luminous performance?

Albert:

There are many different light sources on this planet. There is a living room lamp which you can see is a few hundred Lux maximum, and there is also a rather big lamp outside called the sun. The sun has a brightness of up to more than a hundred thousand Lux.  The sun will also turn most of us red if you stay in it for too long without any sun blocker.

You will most likely not turn red in the living room because the energy emitted by a normal lamp is so much lower than the sun. This is exactly the reason why SuperLuminova will charge very fast with strong light sources, especially those with high UV content like sunlight. It will take a little longer in a living room because it has less UV content and will never be fully charged.  This means that the best sources to charge the luminova on your watch in sunlight or a high UV content light source. This will bring you the best performances.

Applying The SiperLuminova is Important Too

Steve:

Okay, I think I have a good understanding.  I hope everyone else has got a good understanding of how the Luminova itself works now. From a personal perspective, I am interested to understand how to apply it to a watch. What is the best way to ensure that the luminova is applied correctly to a watch to achieve the best performance possible?

Albert:

This is a crucial point that is often missed, yet it is not difficult to achieve good performance.  You have to imagine that every single grain of Swiss SuperLuminova is a little light battery. If you only have a few light batteries on the pile, this will only give you a little bit of light. If you stack up lots of light batteries, this will give you a lot of light from the pile. So it is quite simple, the more volume of SuperLuminova applied to the watch, the brighter the effect will be.

The More Luminova The Brighter

Therefore the goal is to maximize the amount of Swiss SuperLuminova on a watch. The question is now is how can that be done? There are different ways to increase the volume of luminova or pigment on your watch. 

The most obvious is to expand the surface area, but that is a question of design. Not everybody likes a full face Swiss SuperLuminova dial. Another possibility is to increase the height of the application. If you increase the application’s layer thickness, you can place more pigment onto the same surface area. This will result in a brighter performing luminous deposit.

Steve:

Can you illustrate that for us, please?

Albert:

If you look at the graph above, you can see that we have been doing some measurements on the pigment thickness. In this case, we used Swiss SuperLuminova GL-C3 Grade A. This is a standard performing luminous pigment and has no colorant in it.  This means that it should perform compared to a colored pigment.

There is ISO 17514, which defines how to measure a watch component’s luminous decay. This stipulates that the test piece should be charged for 20 minutes with a 400 lux D65 lamp. As you can remember from above, 400 lux is more or less the light conditions in the average living room.

After 20 minutes of activation, the sample piece is placed into a measurement device, and the emitted light is measured. This is measured in nano candela, and you can see in the chart below that the more material you apply to a watch component, the longer light will be emitted or the flatter the decay curve will be. The ISO norm defines that 39 nano candela is the visibility border, so you start measuring your compound as long as it emits more than 39 nano candela, it will be visible in the dark.

As you can see, you can influence the period an application will be luminous pretty easily by applying more pigment. For example, you can see that if you double the application from one milligram to two milligrams, you can almost double the luminous time.

Go Deep For Long Lasting Luminescence

Steve:

If we do not have any option to increase the surface area or increase the print thickness, are there any other options we can consider?

Albert:

We recommend engravings. You will not see a difference in performance for a volume applied, but it gives you more flexibility to create a greater volume to store the pigments. Another test we have done to illustrate this is shown below.  Here we have produced three dials of exactly the same design except for the engraving depths. One dial has 50-micrometer engraving, the second 150-micrometers, and the last 300-micrometers.  The results are quite self-evident, with the first one, a 50-micrometer, visible for around 400 minutes at 150 micrometers. It is visible for approximately 900 minutes, slightly less than an average night.  The deepest engraving will luminesce for 1400 minutes, which is well more than an average night. 

There Is A Limit Though

Steve:

Is there a maximum depth that we can apply Luminova to? I can not imagine that the light charging the Luminova can penetrate the middle of the application if it is very thick?

Albert:

There is a limit where the luminescence performance is reduced because of the thickness of the Swiss SuperLuminova. It is straightforward to charge the pigments at the top of any application, whereas the pigment at the bottom is harder as it is difficult for the UV light to penetrate deep into the pigment to charge it. Afterward, the emitted light faces the same hurdles. The deeper the light is emitted from, the harder it is to escape and be seen by our eyes.  Therefore, we recommend a maximum of 300 micrometers of application. If you apply it more thickly, you can see from the graph that the curve flattens, and there is less and less luminescence performance. 

The other aspect to bear in mind is that it is unlikely you will find an application of one-millimeter. This is just driven by the dimensions of a watch.

Quality Matters Too

Steve:

Are there any other options we should be thinking about when applying the Luminova to ensure we get the best performance?

Albert:

So what can you do if you cannot exchange the surface or not do any engravings anymore? Then you should think about the quality of the light battery. By the quality of the light battery, I mean the quality of the SuperLuminova. When we started producing SuperLuminova in 1994, we produced the standard grade material.  This was the standard back then, but we have been researching and improving the pigments’ performance over the years. Later we launched Grade A quality, and you see on the chart below that Grade A has a flatter decay curve.  This means that it will be visible in the dark for longer with the same pigment volume applied.

What Comes After Grade A?

By doing this, we created a little problem for ourselves because we called the best quality Grade A. If you find a newer, better performing material, you cannot call it Grade B! Therefore, we decided to call the next iteration the highest quality we currently have on the market, Grade X1. This Grade X1 is easier to activate, which means that it has to spend less time in the sunlight to charge the pigments.  It also has a flatter decay curve, which means that it remains readable for much longer periods of time for a given volume of application. 

I hope that has been illuminating for you. Albert and I had a great time doing this. We have enjoyed all the feedback we have received. Please post any comments or questions below in the comments section, and we will be delighted to answer those for you. 

Next Time

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Or check out Episode 4 to continue to improve your understanding of Swiss Super-Luminova.