science

Plasmatron

Plasmatron is a science topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Plasmatron rather than just read about it. In short: The Plasmatron, or technically plasma addressed liquid crystal (PALC), is a color television display technology developed by Tektronix and Sony in the 1990s. PALC displays combine rows formed from liquid crystals with columns formed from plasma cells, the latter replacing the transistorized switching in a conventional LCD.

Key takeaways

Plasmatron belongs to science; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Plasmatron to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Plasmatron from memory before moving on to harder problems.

Reference excerpt

The Plasmatron, or technically plasma addressed liquid crystal (PALC), is a color television display technology developed by Tektronix and Sony in the 1990s. PALC displays combine rows formed from liquid crystals with columns formed from plasma cells, the latter replacing the transistorized switching in a conventional LCD. Although PALC was successfully developed, thin-film transistor based LCD devices were improved which offset PALC's advantages. PALC development has been largely abandoned since the early 2000s.

History PALC was originally developed by Thomas Buzak, who worked at Tektronix in the U.S. Through the late 1980s and early 1990s he developed and patented a number of concepts that used plasma to provide a switching element for a variety of uses. When the project he was working on was canceled, he turned his attention to using the plasma elements as LCD switches, and the PALC system was born. In 1993, Tektronix licensed the technology to Sony, and together they started development of the Plasmatron televisions. In October 1996 Sony entered a three-year arrangement with Sharp Electronics to share development, with Sharp's role being to help improve the effective display angles. In July 1997, the group was joined by Philips Electronics to improve the resolution of the devices, reduce power consumption and increase brightness. Sony and Sharp both produced high-definition television prototypes using the PALC technology, but these never made it to production. PALC was offset by the rapid introduction of thin-film transistors, which allowed individual cells of the LCD to be addressed directly. A grid of rows and columns allows the transistors to be turned on or off just like the plasma cells, but without the need for high voltages or resetting pulse. At first these devices were difficult to produce, but as processes improved the printing methods developed from the semiconductor industry replaced the mechanical complexity of the PALC cell. PALC is no longer being actively developed.

Description

A conventional LCD consists of a grid of individual LCD "cells" with red, green or blue (RGB) colored filters in front of them. A back light source, typically a fluorescent lamp or LED in modern systems, shines white light through the cells. By changing the opacity of the cells, differing quantities of RGB light are produced at any one triplet of cells, producing a single color as seen by the eye. The main problem with producing such a display is the need to individually address the enormous number of cells; in a modern high-definition television with a 1080p display, this requires 1080 rows of 1920 triplet cells per row, or 6,220,800 individual LCD cells. PALC displays attempted to address this problem by introducing an intermediate area between the backlight and the LCD on top that used plasma techniques as a "switch". Instead of using individual cells, the display was arranged as a series of rows of LCDs, arranged in an RGB pattern. Beneath the LCD, and above the backlight, was a plasma display consisting of columns of anodes. A clear conductive cathode was positioned above every LCD row. To produce a display, the system powered each row of the cathodes in turn, along with lit anodes in the plasma layer. This produced a field between the anodes in the columns and cathodes on the rows, producing individually addressed cells. A small amount of ionized gas is pushed towards the LCD in the cells that are powered, creating a small charged spot just below the LCD layer. This switches the LCD, and the amount of power controls the resulting opacity. Cells had to be "erased" to re-draw, by passing a high negative voltage through the cell to push the gas off the LCD layer.

References

Notes

Bibliography

Patents

Further reading Thomas S. Buzak, "A New Active-Matrix Technique Using Plasma Addressing", Journal of the Society for Information Display, 1990, pp. 420–423 Thomas S. Buzak, "Plasma Addressed Liquid Crystal (PALC), A New Flat Panel Technology for Full-Color Video", Tektronix Inc, Paper 9-036, AES 9th International Conference (February 1991)

Worked examples

Example 1 — a first encounter with Plasmatron

Start with the simplest possible case. Write down what Plasmatron claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In science, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Plasmatron before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Plasmatron ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Plasmatron

In research: Plasmatron appears in science research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Plasmatron in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Plasmatron is common in secondary-school and first-year university syllabi. It links to neighbouring topics Television technology, so understanding it makes those chapters shorter.
In everyday life: Look for Plasmatron outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Plasmatron in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Plasmatron means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Plasmatron out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Plasmatron in simple terms?

Why does Plasmatron matter?

Because it connects several science ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Plasmatron?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Plasmatron.