High Refractive Index (RI) Resins for Bright Diffractive Optical Elements (DOE)

High refractive index (RI) materials are used for diffractive optical elements (DOEs) employed in augmented, virtual, and mixed reality (AR/VR/MR) devices and optical sensors.  One cost-effective approach for DOEs with high RI is to use a resin that can be processed rapidly by photo nano-imprint lithography (P-NIL) methods.  When the RI exceeds 1.7 at 589 nm, injection molding is no longer possible due to the lack of very high RI thermoplastics, and P-NIL becomes the overwhelming method of choice for fabrication of elements with nano scale features.   ACW has been a leader in developing resins for P-NIL since the methodology was referred to as 2P (for photo polymer) and used for information layers in data storage applications including Blu-Ray discs.

ACW offers a range of P-NIL resins including several that give high RI cured films.  IP-158 and PR-1600-CA with cured films’ RI at 25 °C of 1.58 and 1.60, respectively, have been marketed for more than a decade.  More recently, ACW developed a higher RI P-NIL resin, PR-1612, which gives a cured film with RI = 1.612 at 589 nm.  And, in 2022, ACW introduced the LuxNIL® line of very high RI resins with tunable RI ranging from 1.6 to 1.8 at 589 nm allowing index-matching with the underlying high RI glass.

The high RI resins IP-158, PR-1600-CA, and PR-1612 are solvent free and can be used for relatively thick films.  These materials are optically clear as can be seen in the UV-vis-Near IR spectra of a 150 micron thick PR 1612 film.  The only loss of light for this film is from surface reflections.  And these materials are quite robust surviving both 85 °C/85% RH for 1,000 hours and 1,000 thermal shock cycles of -40 °C/150 °C with very little effect.  For more information on these high RI resins, click HERE to see a brochure.

The LuxNIL® very high RI resins are inorganic/organic hybrids containing PGMEA solvent.  They were developed specifically for thin films (100 nm to 3 microns) required for AR/VR/MR applications.  These films have high transmittance and clarity and exceptionally low haze as demonstrated below for LuxNIL® P79.  For more information on the LuxNIL® resins, click HERE to see a brochure.

ACW High and Very High RI P-NIL Resins

Resin η25°C (cps)  RI589nm Data Sheet
IP-158     450    1.584    TDS
PR-1600-CA     400    1.600    TDS
PR-1612   1,800    1.612    TDS
LuxNIL® P65   3 – 5    1.65
LuxNIL® P73   3 – 5    1.73
LuxNIL® P79   3 – 5    1.79


UV-vis-Near IR spectra of PR1612