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biomimetic moth-eye nanofabrication: enhanced antireflection with superior self-cleaning characteristic - polycarbonate transparent

by:Cailong     2019-08-09
biomimetic moth-eye nanofabrication: enhanced antireflection with superior self-cleaning characteristic  -  polycarbonate transparent
Wavelength antireflection moth
Manufacture of eye structure by roller with nickel moldto-Plate (R2P)
UV Nano-imprint (UV-NIL)
Transparent polycarbonate (PC)substrates.
The average reflection of samples with good replication patterns is 1.
It is 21% in the range of visible light and 380 to 760 nm under normal irradiation.
At 50 °, the average reflection is less than 4%, showing the excellent transparency of the wide range of angle of attack.
Compared to patterned UV rays
Cured resin coating, resulting fromWavelength moth-
In addition to anti-reflection, the structure of the eye also shows increased water-solubility.
This method is especially suitable for big-
Preparation of regional products and bionic moth-
Eye structures with a variety of properties can be applied to optical devices such as display screens, solar cells, or LEDs. Research on subsidiaries
The wavelength structure of the surface of the moth eye leads to antireflection (AR)
Natural phenomena.
Each small eye of the moth is covered by AR nano-structure
Column array of 200 to 300nm size-
At the same time, the reflection of light is reduced, and the night vision ability is enhanced.
These features allow moths to see well the reflections that their predators do not see in the dark.
As shown in the figure. , the sub-
The wavelength structure is arranged on the surface of the moth's small eye with a highly ordered array.
Since these AR nanoparticles are smaller than the visible wavelength, the effective refractive index between the air and the eye medium gradually changes (380 to 760u2009nm).
In this way, the index of refraction of light does not change suddenly, which will result in proportional reflection.
After observing the AR nano-structure,
The wavelength structure also shows such excellent anti-reflection performance, called "moth-eye effect”.
In recent years, the rapid development of nano-processing technology has led to the bionic moth
Eye structure applied to optical devices such as display screens, solar cells and LEDs (LED).
Up to now, multi-layer coating and graded exponential coating are the two most commonly used methods for the preparation of efficient AR coatings.
The former is based on physical vapor deposition to obtain ultra-thin inorganic layers on different substrates.
However, there are several limitations to this approach.
For large-sized surfaces, it is difficult to process by gas deposition.
The precise thickness of each inorganic layer should also be precisely designed and repeatedly optimized to ensure a high transmission ratio at a wide angle and at a wavelength range.
In addition, it is well known that there are inherent problems with multi-layer coatings such as loss of absorption and scattering, low durability, thermal deformation, etc.
The latter method was inspired by the eye of the moth, using a graded exponential coating to reduce the reflection of light.
This bionic coating consists of highly ordered ya
The wavelength structure array has the advantage of obtaining ultra-low reflection ratio in the wide spectrum and field range.
So far, many surface treatment methods, such as plasma etching, electron-
Beam exposure, sol-
Gel method and self
Assembly methods have been developed and utilized to manufacture antireflection
Wavelength structure on different types of substrates.
Nano-imprint printing has the advantages of high precision, high efficiency, simple operation and low cost (NIL)
Methods, including hot nano-stamping and ultraviolet nano-stamping (UV-NIL)
It is also considered one of the most promising anti-reflection technologies.
NIL is one of the most reliable and effective technologies to manufacture nano-structures at reasonable low cost.
This technology was first proposed by teacher Zhou.
Prepared for 1995
The structure of the polymer surface is 25 nm.
Grant Wilson and his colleagues, 1999
Workers extend the NIL Technology to UV-curable resins.
Therefore, the thermal and UV imprint are involved in the NIL technology, both of which can be applied directly to the polymer surface.
In the process of NIL, a mold with a pattern (
Usually composed of silicon, nickel and polymer substrates)
Covered with a layer of UV
Cure the resin or thermoplastic polymer and imprint by applying appropriate imprint force and temperature within a reasonable time.
In the past ten years, AR technology has been widely used in the manufacture of AR products. Jung .
Turn AR moth-
Using UV-eye structure on the surface of the glass substrateNIL method.
In the range of 91% to 800nm wavelength, the normal transmission ratio of the bare glass substrate is from ~ 93% to 97% and ~ 400 for single and double sided patterned AR products. Kim and co-
Workers reported that based on the heat-
The NIL process on a PC film with an average normal event transmission ratio of about 92% (
The wavelength range is 400 to 800nm). Abbott .
A soft Roll NIL Technique for preparing subwavelength silicon moth is reported. eye structures.
Their products are within the spectral range of 400-1000 µnm, with an average reflection of 3% from a 45 ° perspective.
In addition to the enhanced AR performance, superior hydrophobic behavior is also common
Products of subsidiariesWavelength moth-eye structure.
Usually, the water contact point of AR structure samples prepared on the polymer or glass substrate with NIL Technology can reach different geometric structures ~ 100 ~ 120 ° range.
For AR structures formed by certain chemical processes (e. g.
Reaction ion etching)
Or special grading structure, AR products can present super-drain performance at water contact points higher than 150 ° (
Even above 170 °).
Based on the theory of effective media, this paper proposes
When light interacts with the surface of the coating, the wavelength structure will be used as an effective medium.
For example, look at UV-curable resin.
Refractive index change of schematic diagram as shown in figure shown in. .
This event Light and single
Coating without AR structure (Fig. )
It will experience three different refractive indexes, the refractive index of air (n), UV-curable resin (n)
, And substrate (n), respectively.
However, a coating with a column
Wavelength structure array (Fig. )
There will be an extra effective refractive index (n)
, Controlled by the ratio between the structure and the Channel.
Effective refractive index (n)
Tapered subwavelength structure of triangular profile (Fig. )
An infinite thin layer equal to a linear change of duty cycle will undergo a linear change from n to n.
Schematic diagram of bionic moth-
Eye structure is the focus of this work, as shown in the figure.
As a variant of the tapered subwavelength structure, the n of this moth
Eye structure with parabola
The outline of the shape will undergo a gradual change, not a linear change.
In this studyInverse wavelength
The reflective structure is made of rollersto-Plate (R2P)UV-
No method for transparent polycarbonate surface (PC)substrate. A GP756 UV-
Curing Resin provided by Everwide chemical, Ltd.
Select for preparation of AR coating.
It was found that the main component of GP756 was tripentyl alcohol triacrylic acid (PETA)
Infrared spectrum analysis (As shown in the figure. ).
The product has two properties: AR and hydrophobic. The R2P UV-
The NIL method is especially suitable for large-
The preparation and efficiency of regional products are very high.
The main program can be completed within 1 or 2 minutes.
In addition, the cost of R2P UV-
The NIL method is much lower than traditional etching and electronic techniques.
Beam exposure
Therefore, the proposed manufacturing method and the Bionic moth
In the near future, eye products with a variety of performance may be applied to optical devices such as display screens, solar cells and led.
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