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Back in the eighties, batteries weren't yet at the point where they could run a laptop with similar computing power to a desktop. If you wanted that much computing power, you just accepted that your laptop needed to plug into the mains.

Given that, early portables used CRT screens on the order of 5 inch. Hard to read and very heavy.

The Toshiba T3100 released in 1986 used a plasma screen. Much bigger display area, thinner, a better choice all round.

But apparently plasma screens were around more than a decade earlier than that, and 1970s plasma screens don't look deficient in the pictures I've seen of them. So why weren't plasma screens used in laptops earlier than 1986? Or is it that they were and I missed it?

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    You seem to be asking several different questions. From the body, it seems that you want to know why plasma screens weren't widely used in laptops before 1986, not the earliest occurrence of them as the title implies. – wizzwizz4 May 16 '17 at 16:12
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    1982's Grid Compass, often cited as the first genuine laptop, and utilising the same clamshell design as any modern laptop, used an electroluminescent display rather than a CRT. So I suspect the question might inadvertently make a false dichotomy? – Tommy May 16 '17 at 16:42
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    I'm far from an expert, but based on the names I think electroluminescent is a different technology from plasma — gas plasma is electricity within neon gas, just like neon lighting, whereas the archetypal electroluminescent display per Wikipedia uses gallium arsenide. – Tommy May 16 '17 at 20:30
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    @rwallace AC-powered plasma screens were commercialized by the end of the 60s, but DC-powered plasma screens did not emerge until the 70s with "dot-matrix" versions (what you want for a computer display) appearing in the late 70s. In these early stages power requirements (and cost) were significant, lots of R&D was still required to get to a point where you could use them in a laptop. So no you didn't miss anything, mid-80s is about the time plasma matured enough to be commercially viable in laptops and other portable con/pro-sumer devices. – misha256 Jul 6 '17 at 3:32
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    A plasma screen needs several 100Volts to light the pixels. That was hard to draw from batteries and pretty hard to create from battery voltage with acceptable efficiency. – tofro Jul 6 '17 at 22:48
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There is a fascinating publication called Flat Panel Displays in Perspective, put out by the (now closed) Office of Technology Assessment, United States Congress. The key quote from the publication:

...the first direct current (DC) plasma displays were segmented displays developed in the 1970s to replace the Nixie tube. Later in the decade, dot-matrix versions were developed.

It doesn't give exact dates but if development of dot-matrix DC panels didn't happen until the "late 70s" then it's safe to assume the technology could not have become commercially viable until some time later, i.e. in this case the mid-80s.

5

The Plato IV computer terminal introduced in 1972 had a 512×512 pixel plasma display.

The reason why plasma displays were never popular in battery-powered laptops is because they use a lot of power compared to LCD displays, especially when not all laptops were backlit.

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