Various shapes of microlens arrays (MLAs) were developed by utilizing polymer coating on etched quartz substrates.
Spherical and non-spherical plano-concave curvatures were realized via isotropic wet etching of quartz in buffered oxide
etchant (BOE), based on diverse design parameters and calculated etching times. The fabricated curvatures showed a
high fill-factor and uniform elements in the array. By coating a higher refractive index polymer on the etched quartz, the
illuminated light was well focused at the focal plane forming a micronscale light spot array. The experimental focal
length was increased from 39.8 to 49.6 μm, as the shape of microlens was flattened. These results well correspond to
those obtained from an optical simulation.
A microlens array (MLA) was developed based on isotropic wet etching of quartz and coating of polymer on the etched
substrate for maskless lithography application. Through the optimized manufacturing procedures, uniform elements,
excellent light focusing ability, and dense fill factor were obtained. The fabricated MLA has the focal length ranging
from 32.2 to 45.4 μm depending on the etching time and the thickness of the coated polymer. The collimated light was
uniformly focused on the whole focal plane after passing through the fabricated array of microlenses and the size of the
each focused beam was ~1.5 μm. By using the compact imaging ability of the miniaturized lenses, the MLA was applied
to UV photolithography process. The illuminated UV passing the MLA focused on the photoresist, producing micron
scale pattern array. Various sizes and shapes of micropattern arrays were realized onto the PR via controlling the
experimental variables. Even at high temperature, the MLA performances were not changed indicating thermal stability
of the developed MLA.
This paper presents the fabrication and test of a flexible luminous device using hollow cathode discharge. The discharge
device consists of three layers which are a thin anode layer, an insulation layer and a hollow cathode layer. The device
has an array of 10 x 10 holes for the emission. The hole diameter and depth are 100 μm and 120 μm, respectively. The
hollow cathode discharge occurs between two electrodes. The hollow cathode discharge usually has the characteristics
of the high current density. The discharge device is fabricated by micromachining technology. The anode and the
cathode are aluminum and nickel, respectively. Polyimide is chosen as an insulating material because of an excellent
dielectric property and a good mechanical stability. The anode of aluminum is deposited by thermal evaporator.
Polyimide is spin coated and the hollow cathode is fabricated by nickel electroplating. The thickness of the flexible
luminous device is about 150 μm and total size of the device is 20 mm x 10 mm. The discharge test was performed in
argon gas chamber at room temperature for various pressures. The current is measured during the discharge to various
applied voltages. Current-voltage characteristics of the device were obtained for the operation voltage ranging from 250
to 300 V. The discharge appears at the applied voltage of 260 V in 360 torr. The discharge is also observed at the
atmospheric pressure. Compared with a macro discharge device, this device operates at much higher pressure, even at 1
atm. The discharge test confirms that the fabricated device is feasible for a flexible display operating at the atmospheric
This paper presents the fabrication and experiment of a flexible micro hollow cathode discharge device. The device is composed of three layers which are a thin anode layer, a insulation layer and a hollow cathode layer. The micro hollow cathode discharge occurs between two electrodes that have an array of holes with the diameter of 70 μm. The device has an array of 7 × 11 holes. The hollow cathode discharge usually has a characteristic of the high current density. The device is fabricated by micromaching technology. The micro hollow cathode is made by means of nickel electroplating in the photoresist mold. The material of the thin insulator is polyimide. Polyimide is spin-coated on a nickel layer and the anode is fabricated by thermal evaporation of aluminum. The thickness of the flexible discharge device is 50 μm and total size of the device is 20 mm × 10 mm. The test set up consists of a direct current high voltage source, a ballast resistor, a gas chamber and a CCD camera. The discharge test was performed in argon gas chamber at room temperature for various pressures. We measured the current while the discharge occurs for various voltages applied. Compared with macro discharge devices, this device operates at much higher pressure, even at 1 atm. The discharge appears at the applied voltage of 0.23 kV in 260 mm Hg. We observed the stable discharge. The device breaks down when the current is over 3 mA. The obtained current-voltage relationship is linear.