Liquid Crystal Measurement Instruments 2007 - Instec Inc

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NNLCG1 – Rotational Viscosity for Negative NLC With the advent of projection and direct-view large-sized liquid-crystal monitors and televisions the vertically aligned mode has come into prominence and with it the negative dielectric liquid crystals on which it relies. One of the most critical parameters for any LC is γ , the rotational viscosity, which greatly influences the time response of the display. However, measuring the rotational viscosity of negative dielectrics has traditionally been difficult due to such switching phenomena as backflow and the like. Instec designed the Negative Nematic Liquid Crystal γ 1 test instrument specifically to overcome this problem. With it, one can quickly and accurately measure the rotational viscosity of negative dielectric materials in seconds. The rotational viscosity is a parameter particularly sensitive to temperature. As with all Instec liquid crystal measuring instruments, the NNLCG1 integrates easily with either the ALCT3-TS temperature controlled shielding box or our standard temperature controlled stages. Technical Specifications Output Wave 1 KHz, voltage 0 to ±100V Output Update Rate 500KHz Output Resolution 16 bit Input Resolution 16 bit Input Sample Rate 500KHz Current Measurement Range 1nA ~ 1mA Current Sensing Resistance 10KΩ Current Resolution 100pA Post Gain in the ALCT Box 1, 10, 100, 1000 Capacitance Measurement 2pF to 100nF Easy-to-Use Software 6
IV1 - LC Tester for Ion, Resistivity, VHR, and RDC Instec designed the IV1 specifically with the industrial customers in mind. Its electronics are capable of exceedingly sensitive current measurement and low leakage voltage measurement. Its cables and connectors are triaxial in order to allow guarding against external leakages. The IV1 can be configured to measure any or all of the following: • Ion Density • Liquid Crystal Resistivity • Voltage Holding Ratio (VHR) • Residual DC (RDC) Ion density and liquid crystal resistivity are critical components in the proper functioning of any LC display but especially active matrix LCDs. With too many contaminant ions or too low a resistivity, displays are prone to problems such as image retention and flicker. These measurements are useful to LC manufactures both in the development of liquid crystals and quality control. In addition, display manufacturers can use them for both incoming and in line quality inspection and as a diagnostic tool to trace down root causes of problems on the line. VHR and RDC are a more direct probe for potential problems. Lowered Voltage Holding Ratios can result in noticeable flicker to a display user. Elevated Residual DC values can also produce flicker and/or image retention (or image sticking). In measuring VHR, the IV1’s built in function generator outputs to the sample under test an AC pulse train of user adjustable frequency, amplitude, and duration. Simultaneously, the IV1’s internal electrometer senses changes in voltage on the sample, in particular the voltage droop between pulses. For the measurement of RDC, the IV1 applies a set DC voltage to the liquid crystal cell of user selectable magnitude and duration. The built in electrometer then records the residual DC voltage left on the sample cell, again for a user selectable duration. Since the duration of the initial DC voltage may be an hour or more, while the measurement time may be set to ten or more minutes, a single RDC determination can be a long process. With that in mind we designed the IV1’s electronics with a modular structure and options exist to add up to 8 channels. Technical Specifications Ion/Resistivity Voltage (Min) Voltage (Max) Resolution Frequency Current Range Current Resolution Electrical Connections Voltage (Min) Voltage (Max) Resolution Output Current Offset Voltage Input Capacitance (Hold Mode) Leak Current (Hold Mode) V.G Offset (Hold Mode) Charge Injection Electrical Connections ± 10mV ± 10V (± 100V optional) 100 μ V 0.01 ~ 1kHz 100pA to 1mA 1pA Triaxial Voltage Holding Ratio / Residual DC Voltage Measurement ± 10mV ± 10V 100 μ V ± 100mA (Max) ± 0.1mV < 1pF < ± 0.1pA ± 0.1mV ± 5pC Triaxial 7
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Liquid Crystal Measurement Instruments 2007 - Instec Inc

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