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Heatsinking for Magnetic Matrix Display

IP.com Disclosure Number: IPCOM000123385D
Original Publication Date: 1998-Oct-01
Included in the Prior Art Database: 2005-Apr-04
Document File: 2 page(s) / 79K

Publishing Venue

IBM

Related People

Beeteson, JS: AUTHOR [+4]

Abstract

A Magnetic Matrix Display (MMD) is essentially a flat, thin CRT. If a thermionic area cathode is used as an electron source then good thermal design is essential to remove the heat generated by the hot filament wires. The structure described here provides a glass/metal composite vacuum sealed package that gives excellent heatsinking.

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Heatsinking for Magnetic Matrix Display

   A Magnetic Matrix Display (MMD) is essentially a flat,
thin CRT.  If a thermionic area cathode is used as an electron
source then good thermal design is essential to remove the heat
generated by the hot filament wires.  The structure described here
provides a glass/metal composite vacuum sealed package that gives
excellent heatsinking.

   Figure 1 is a cross section through the improved
display.  A is the front glass plate coated with phosphors and black
matrix.  B is the glass side plates frit sealed to glass plate A and
the rear substrate.  C is the rear substrate and sides of the
display.  D is a flat, thin magnet carrying a grid structure front
and back.  E is a mesh grid and F are oxide coated tungsten filament
wires which operate at a temperature of 993oK.  G is the rear plate
of the cathode structure which is typically held at a low negative
voltage.  H is a plane of low velocity, high density electrons,
produced during cathode operation.

   The improved structure uses a metal rear substrate, which
plainly gives a very high thermal conductivity.  A glass to metal
seal is then required between rear substrate C and glass side plates
B.  Achieving a good, vacuum tight seal is possible provided that the
metal has a precisely matched thermal expansion to the glass.
Preferably a properly formulated stainless steel material would be
used.  A simple frit sealed flange may then be used, but preferably
the flange will partly run up the sides of the glass.  Some options
are shown in figure 2.

   When the MMD is evacuated the pressure on the materials
becomes very large, and thus a high stiffness is required.  Thick
stainless steel may be used, but this would be both heavy and
expensive.  One way round the weight and cost problem is the use of a
die cast Magnesium alloy, which is light, strong and low cost, and
can also have integra...