Optical Film for LED with Triangular-Pyramidal Array Using Size-Reducible Embossing Method

Abstract

This study presents a modified hot-embossing process to fabricate micro-triangular-pyramidal array (MTPA). First, a tungsten (W) steel mold (as the first mold) is manufactured by precision machining including optical projection grinding, lapping, and polishing processes. The dimension of a triangular pyramid with acute angle of 85°on the W-steel mold is about 300 lm in width and 139 lm in height. The pitch between two triangular-pyramidal tips is about 170 lm. Then, only the portion of the tip area of the triangular-pyramidal patterns is transferred on bulk metallic glass (BMG, Mg 58 Cu 31 Y 11 ) using this modified multi-step hot-embossing method to reduce the pattern size. With a position-adjustable mechanism, size-reduced concaved-shaped MTPA can be selectively formed, used as the secondary mold. In this way, not only can the size of triangular-pyramidal patterns on W-steel mold be reduced down on BMG, but also the tool arc between each triangular-pyramid on W-steel mold caused by machine tool can be eliminated. This is based on the fact that amorphous glass alloys contain no dislocation that can be responsible for yielding in crystalline materials. Thus, BMG is expected to be strong and hard enough to be used as a mold material. Then the secondary mold is used to emboss convex-shaped MTPA on PolymethylMethacrylate (PMMA) optical film. Experiments with different embossing times and embossing pressures are conducted and discussed. Large-sized triangular-pyramidal array on the W-steel mold has been successfully and selectively miniaturized on BMG, and then transferred on PMMA. Finally, this optical film of PMMA with MTPA is packaged on light-emitting diode (LED) to improve its lighting uniformity and luminance. In comparison with commercial 3M Ô optical film (3M Ô Vikuiti Ô TBEF2-T-65i), the film with MTPA shows a good optical performance.

Lens of controllable optical field with thin film metallic glasses for UV-LEDs

“…Application examples of bulk metallic glasses (BMG) have been extended to much valuable fields. Liu et al [12] studied the fabrication of triangular-pyramidal metal molds using BMG master molds with micro structures by thermal imprint process. By alloying minor addition of Al and Ag into Zr-based MG, the thermal stability and homogeneity could be further enhanced to satisfy the requirement of sputtering target [13].…”

A facile fabrication of light diffusing film with LDP/polyacrylates composites coating for anti-glare LED application

“…It is widely used in various applications such as LED light systems, backlight unit (BLU) of liquid crystal display (LCD), signs, etc. [1][2][3][4][5][6][7][8].…”

“…When the light passes through the surface with microstructure, a refraction event occurs between the interface of the film and the air, and the incident light is deflected from its course, resulting in light diffusion. There are various methods for fabricating surface-relief type such as replica molding method [14,15], embossing process [7,16,17], lithography [8,18,19], electrospray method [20,21], etching [22,23], holographic technology [24], etc. According to the different preparation methods, the micro-structure can be a hemisphere [14,15,20,21], paraboloidal shape [8], polygonal shape [3,26], pyramid [27,28], cylindrical lens [16], V-shaped mirror [17], or irregular type [4,19,22,23], etc.…”

Compound Optical Film Using Gray Scale Mask Embedded with Microvoids

“…The optical properties of glass such as reflection and refraction indexes can be modified [5]. A modified hot-embossing process fabricated microtriangular-pyramidal array and the optical film of PMMA with microtriangular-pyramidal array were packaged on LED to improve its lighting uniformity and luminance [6]. An optical film with aspherical microlens array by using multistep lithography process for an OLED (organic light-emitting diode) package was fabricated, by which method the luminance of OLEDs can be enhanced [7].…”