David Leksell

The influence of chlorine on the crystal structure and electroluminescent behavior of ZnS:Mn Films in thin film electroluminescent devices

Comparative experiments showed that the addition of chlorine at the preparation of the ZnS:Mn source materials for TFEL device fabrication can enhance grain growth in the ZnS:Mn films during post-deposition anneal. Correspondingly the luminescent properties of these films improved as compared to those without chlorine. Depending upon the Mn concen-tration and annealing temperature, both the saturation brightness and the peak luminous efficiency have increased by up to a factor of three. Optimized experimental para-meters resulted 810fL saturation brightness and 0.6l/W peak luminous efficiency. A practical significance is that useful TFEL devices can be fabricated using source materials with Cl, addition when post deposition annealing temperatures have to be kept low.

Preparation and characteristics of white EL display panels

Two methods for preparing white emitting EL panels are well known in principle: (1) blending a blue and an orange emitting EL phosphor and (2) partially cascading of green EL emission with a red photoluminescent material, typically an organic fluorescent dye. Both methods have their advantages and shortcomings. Panels containing phosphor blends are readily viewed even in moderately bright ambient light but the “ white” color is reasonably stable only over limited times because the blue phosphor comnonent deteriorates faster than the orange. Cascading panels show very long lives, depending on the green EL phosphor involved, without any visible color change but these panels can be used only under restricted ambient light conditions. Brightnesses and efficiencies of both kinds of panels are about comparable

Crystal growth aspects of the fabrication of high output thin film electroluminescent edge emitterTM arrays

Abstract Edge emitter TFEL samples were prepared by vacuum deposition. The composition of the source materials for the ZnS:Mn films was varied, and so was the substrate temperature during deposition. In particular, the source materials had an addition of Cl, and the substrate temperature was kept low during deposition. The edge emitter with the lowest attenuation was deposited from the highest Cl containing source material and at a substrate temperature that was initially high but was decreasing quickly during deposition. We believe that the likely reason for low attenuation is grain growth in the ZnS film which is not accompanied by the formation of intergranular cavities.

Test Station For Thin Film Electroluminescent (TFEL) Edge Emitter Array, A Potential Low-Cost, All Solid State Imaging Device

A test station was developed to evaluate the TFEL edge emitter array in various imaging applications. It consists of 400-dpi and 20-dpi resolution edge emitter array test samples, a sample mount that accepts both kinds of edge emitters, and an electronic drive system. The drive system provides variable drive frequency and excitation voltage, internal test patterns, and an option for external data input. As an example of its capabilities, electrophotographic printing samples are shown.

Gray scale and resolution enhancement capabilities of edge emitter imaging stations

Westinghouse has developed a thin film electroluminescent (TFEL) edge emitting imaging station for use in electrophotographic printing. The physical and electrical drive characteristics offer unique opportunities for gray-scale printing and resolution enhancement. The physical dimension of the light-emitting element in the process direction is less than to micrometers . In addition, the light output of the edge-emitting array is not Lambertian but, rather, is highly directed. The majority of light is emitted in a wedge with a 30 deg half angle measured form the plane of the device. The array is activated by an ac waveform. Light emission occurs as the field across the device changes direction. The rise time to peak light emission is a few microsecond(s) and the decay is a few hundred microsecond(s) . This allows an array element to be turned on and off several times during the exposure of a single 300 dot-per-inch pixel in a low-speed printer. This paper provides a detailed description of the physical dimensions, electronic drive system, and light emission characteristics of edge-emitting array. Several print samples are shown illustrating the gray scale and resolution enhancement capabilities.

Development of full-size thin film electroluminescent Edge Emitter array for electrophotographic applications

A full size 400 dpi Edge Emitter array was designed and constructed. The light-emitting edge is 8. 18 inches long capable of printing across the full width of the page. An Edge Emitter head was assembled consisting of three components: a 400 dpi Edge Emitter array a circuit board containing the channel driver ICs and a SELFOC R lens array in a frame. The frame also provided the means of mounting in a 6 ppm electrophotographic printer. Pages of graphics and alphanumerics were printed to demonstrate capabilities of the Edge Emitter array. 1.

A Multiplexed Drive Mode For A TFEL Edge Emitter Array

The already low cost of the thin-film electroluminescent (TFEL) edge emitter imaging station will be further reduced by implementation of a multiplexed drive system. Therefore, the multiplexing modes for TFEL edge-emitting devices were examined. Several multiplexing modes were tested and 12.5% duty cycle was selected as having the potential to be the most economical. It was demonstrated that the output power required for printing can be maintained at this level of multiplexing.