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What is the official name again for the small black trimming 'border'/'mask' around the four edges of a display?

I just forgot the official name.. and google turns up results about a wrong display ratio or to small display setting, which is not what I'm after.

As one can see on the following picture the image (desktop) is to big and gets 'cropped' by this 'border', before reaching the edge of the display's case.

picture with over-scanned image falling behind this 'border'

Here is another image, where I put a circle around a piece of this 'border':

enter image description here

and another (burned in, over 3 years, cool right?) bare tube:

enter image description here

Update 1:
Thanks to DeanB's answer, a close-up picture showing that this 'border' is part of a shadow mask:

close-up picture of from a corner of a shadow mask

Update 2:
Upon further research on DeanB's answer, the term 'shadow mask skirt' seems most appropriate (according to a multitude of patents, if I interpret their accompanying texts correct, but please don't hesitate to comment/answer/correct this if I should be wrong).

Update 3:
I have added 2 extra images.
According to Richman's answer, this border is a separate border, called 'oversan skirt' and not related to the shadow-mask.
I might have been been to hasty to accept an answer (because the shadow-mask detail image made sense), but Richman seems to have a point to, since different types (crt/trinitron/diamondtron) of tubes have this edge/border, so I'm un-accepting DeanB's answer for now.

For extra clarification, I'll reformulate my question to: Complete the following sentence: "adjust the width/height/over-scan until the image touches the edge of the ????"

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2 Answers 2

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Actually the black "skirt" on the peripheral is to provide a sharp mask to overscan on CRT's. Judging by your photo you have excessive overscan and the corner of the beam is cut off by the "overscan skirt"

The overscan skirt is not the "shadow-mask skirt" which was designed to provide a unique aperture so that each color gun only casts its beam on the its own color phosphor on a flat screen.

enter image description here

Overscan skirts only apply to CRT where deflection is analog. Unlike LCD or plasma displays where pixels are addressed electrically. However LCD's may have CFL edge diffused backlights which can bloom light on the edges, so a very small edge mask is used here. For LED backlight LCD's no edge mask is required.

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  • \$\begingroup\$ Since different types of display have this border, you must have a point. Could you elaborate your answer a little, maybe point to a reference where this overscan skirt is mentioned/displayed? Thank you!! \$\endgroup\$
    – zduk
    Commented Nov 30, 2012 at 19:13
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This is CRT-specific, but what you see is the outer edge of the shadow mask.

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  • \$\begingroup\$ I had that wiki-link, yet missed the image (I'll add to my post). So I thought the shadow mask was the grid only. So 'shadow mask outer edge' would be the best/proper terminology? Thank you, sorry, can't upvote. \$\endgroup\$
    – zduk
    Commented Nov 29, 2012 at 18:08
  • \$\begingroup\$ I'd call it the shadow mask "surround" or "frame", but "outer edge" works, too. \$\endgroup\$
    – HikeOnPast
    Commented Nov 29, 2012 at 18:21
  • \$\begingroup\$ 'shadow mask frame' seems to be a specific component that holds the shadow mask (under tension), as far as I can see on google images. Whilst I like 'surround' it seems a lot of crt-related patents SEEM to talk about a 'skirt(-portion)'. Being a non-native speaker, I'm not fully sure if this 'skirt' equals 'surround'/'edge'. \$\endgroup\$
    – zduk
    Commented Nov 29, 2012 at 19:25
  • \$\begingroup\$ 'skirt' makes sense. \$\endgroup\$
    – HikeOnPast
    Commented Nov 29, 2012 at 19:39
  • \$\begingroup\$ Then.. the best answer would be 'shadow mask skirt'? PS, thank you for the thorough help/aftercare so far! I'll ask a colleague to up-vote. \$\endgroup\$
    – zduk
    Commented Nov 29, 2012 at 19:49

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