Note: Descriptions are shown in the official language in which they were submitted.
I'IIN 73.J~
~ O/Yi~rl3/~;L~L~I
17--12-1971~
~(943~
~Glass for te1e~is:ioll di5pla~ catllo~o~ray tubes".
_____.
The in~ention re1~tes to glass ~or a catllode-ray
tube env~1opo ~Ol' displa~rin~ colour te1evision ~:ictures, p~r-
tiou1ar1y glass ~or the ;race-p1a~e of tho tuba~
Such a series of specia1 glasses i5 knowll I`rom the
5 UK Patent Specification 1,290,608, ~ ose.composition in ~ by
weight lies Wit}lill tlle ran~e 1imited as ~o110~rs, ~ tll tlle
associatcd additional conditions:
SiO2 5l~69
Na20 6 10)
t Na O ~ K O combi~ed 14-2
.10. K 0 5-1oJ 2 2
- CaO 0-4
MgO 0-2.5
A123 o_6 1
zro2 o-6~ r2 ~ A12o3 ~ 6
~ ~aO 8~ BaO ~ 2ZrO2 ~ ZnO ~ IISb203 > 20
ZnO 0~5 J zro2 ~ ZnO ~ Sb203 ~ 3
~2 -5~93
Sb203 o_3 .
~203 ` As203 + Sb203 ~ -3
The~e series o~ g1asses was found to sat1s~y the ~or~
- . .
stringent requirements relati~o to X-ray transmission~ This
stringent requirement states that the intensity o~ tlle trans-
mitted X-ray radiation must be not more -tl-a~ 0.5 mi1lirontge~
per hou~ (mr/h)~ mea~llred at 5 om~ ~rom tlle screen at an
acceleration voltage o~ 35 kV and an anode current Or 3 x 100
: -2
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:E'IIN 73~
17~ 7 l1
~6~43~95
in a television display tubc.
Starting from a minimum thicl~ness of 11 n~n of tho
screcn gla~.s~ the above-ment-io}l-~d r~n~e of glass~s amply c;at:is-
fies this requirement; a nwllber of gla35es locatcd witl-Lin t]liS
ran~e o~ compositions remains ~ithin ~he impos~ r-~quircm~nt,
even at an acceleratlon volta~e of l~o ~
Thesc glasses were a satisfactol~y comproltl~sc rela~ e
to the othcr roquire~ nts to be imposed on glas~es :for tllis
use ~ to wit:
a) the temperature difference be~-~eell the so~teni.n~ point, i.e
the temperaturo at which the vi.scosity of the glass is 107 ~
poises, and the alLnealing point, i . e~ the temperatule at W31iCn
the viscosity of the glass is 10 34 poises9 must be at lca~t
1 ~)0C .
b) the annelaîng point must bo not less than 4850C~
c~ the thermal coe~ficient of expallsion must De ap~ro~il~teL-y-
100 x 10 7/oc in the range of 30-300C~
d~ the glasses must not show any.trace o~ devitrification
phenomena~ ~
~e) when re-usingr rejected screons on which the ~luor0scent
coatin~r is.~removod and which are cleaned by meuns of a
.~hydrofluoric acid-containing solution, thore may be no trace
o~ selocti~e attack~ and
f) the ~alue of T ~ ~i.e. the temp0raturc at which e = 10 5
. Ohm~cm) must be not less than 3600C.
The tendency of still further increaslng the safety
margin rolati~e to X~ray radiation emitted by television
displcLy tubes has continuod.
Accordin~r to this more strin~ent requirement a dis~lay
tube operated at an acceleration volt-a~re o~ ~0 kV and an anO~
: ~3
~ .
l"rN 7~5
17-12~1~7
30g5
curront of 3 x 100 /uA ~nc~ mit not more tl~an 0.5 Ill~/h of X-
ray radiat:ion, me;lsured~lt a distance of 5 cnl from the screen.
Tllis more stringent requirelllent can easily bc satis-
~ied by il~creasing th.e sllare o~ o~ es o~ hcavy ~let~ in glass
of the above-mentioned type, bl.lt the probl~l i.. s that at tlle sas,~e
time the other propertie.s stated l-ereinbcfore must not ~eviate.
The invention provides a range o~ ~la9se~ wi-th which
this com~lex Or proporties is realised and sollle o~ th~m yield
an X-ray radiation within the abo~re~mentio~d In~rgln at an
acceleration voltage o~ up to 45 kV. Su*pris:ingl~ , the ZrO2
content relati~e to the above~ entione~ knowll glasses could
ev0n ~urther be increased ~ithout devit-i~ication phcnonlana
occurrin~O Generally~ ZrO2 considerably irlcreases tll~ crystalli-
sation tendency of glassos; ZrO2 is ~requentl~r used as a
. nuclai-forming agent in the-manu~acture Or ~lass ceramics.
- The~lasses according t~ the inven tion are character-
ized in that-~ their composition lios within the ~ollol-ring ~ange
limited in ~ by lre:ight: i
.
; . . . SiV2 58 66
.
~ Na20 7_~o
K~O 6-11 cnmbined 1~-20
L- 0 0-2 . . -
CaO 0-4
MgO -0-2.5
2 3 0-2
Zr2 6-10 l
BaO 4-18 ~ BaO ~ 2ZrO2 ~ 3.1PbO ~ 28
- P~o o_l~
:
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I'lIN 7~5
1 7- 1 2~ '7
4 ~ 9 ~
~2 ~5 - ~3
Sb23 ~ ~523 -3 ~ -7
~ 0.2--2
Tho glasses ~ithi~ t~le follo~Yin~ limi.ts in ~ by w~ig~t
are proforred, because their omitted X-ra~ radiatio~ ramai.~s
within the above-mentio.ncd mar~in, e~on at an acc~leratio~
~olta~e of up to 2~5 k~r
SiO2 . 5~-66
Na 0 7-10
K20 6-10 combincd 14-20
L~20 0-2
- CaO 0-4
MgO ow~,5
.15 ~123 0-D.5
Z~2 ~ 7~9 )
~aO 8-18 ~ BaO ~ 2ZrO2 ~ 3.1PbO ~ 28
PbO 0-2'J
- CeO2 -5-~-3
. Sb23 + AS23 -3'~7
- F 0.2-2
Sevcral glasses according to the in~ention will now
.be mentioned b~ way o~ example with their important physical
val~e~. They ara obtainod in the conventional~glass--technological
manner by melting a mi~ture o~ sand~ potassium carbollate~ sodium
car~onate, dolomite) cerium oxide, barium carbonate, zirconium
silicate~ antimony oxide and sodium silicofluoride, and if
~vccssary, ~olspar, magnesium oxi~e, calcium carbonate, peta~ite,
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- - -- T ~
lll~ 7~$
~, 17~l2 19'74
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3Q95
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minium, sodi~n nitrato and arsellous trioxid~.
The relQvant mi~tures a~e intro~ucecl into a platinum
crucibl~ in a ~as-fir~d furn.~o~ at 1400C wi~h ~.n air excess Or
1:2.5~ ~ft~r n~lti~g l~ tcmperature in th~ furnac~ i.3 mai.n-
tainod at 1/150C for 2~ hour.s, cooled to 1200C alld t~len 1;lle
~lass~s are pour~d ou~.
~aea//~g
. l'h~ U'~ ,, poi.nt and the soft~ning p~in-t ar~-
denoted b~r ~he ~bbreviations an.p. and sr~p, r2spec~i~elyO
." . Thc coef~ici~nt Or e~pansion o~ -t~le gl~ss~s lies
betw2en 98 and 102 x lG 7/oc, measured ~et~ n 30 and 300C.
C omp o ~s ~ t i OIl ~, _
1 1 2 1 3 . 4
~r SiO2 61 .6 60.6 6002 60006
Na2~ 8~8 .9-3 8~5 8~7
K20 8.1 8~ 1 .8-1 10~6
BaO 13.6 13.6 16.3 10.7
Zr2 6.o ;7.5 6.o 9.o .
PbO 1.0 : - . .
23 0.1 0.1 0.1 0.14
2 3 o.6 oO6 0~6 o~6
CeO~ I 0.2 0.2 0.2 0,2
to ~hich is . : . .
added in ~ ~ 0 . 8 : 1. 5 0 ~ 8 0 ~ 8 .
__~ ~ , , . _
an.p 490 490 4~8 497
~-P I 680 ~88 691 713
T ¦ 366 360 377 3~0
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