R. D. KELL, METHOD OF ADHERING PARTICLES TO A SUPPORT SURFACE, FILED MAY 3, 1965

• Document Type: CREST
• Collection: General CIA Records
• Document Number (FOIA) /ESDN (CREST): CIA-RDP81-00120R000100020071-7
• Release Decision: RIFPUB
• Original Classification: K
• Document Page Count: 15
• Document Creation Date: December 20, 2016
• Document Release Date: December 4, 2003
• Sequence Number: 71
• Content Type: CONT

Approved For Release 2007/09/21 CIA-RDP81-00120R000100020071-7
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VITIOD OF ADIm1IH3 FARTICLBS TCJ A SUPPORT SURFACE
Pi1od May 3, 1965
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Approved For Release 2007/09/21 : CIA-RDP81-00120R000100020071-7
 Approved For Release 2007/09/21 : CIA-RDP81-0012OR000100020071-7
Sept. 27, 1966 R. D. KELL 3,2 75,466
METHOD OF AJF:&RINO PARTICLES TO A SUPPORT SURFACE
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 Approved For Release 2007/09/21 CIA-RDP81-0012OR000100020071-7
Sept. 27, 1)66
3,275,466
ME?'ROD OF ADHERING PARTICLES TO A SUPFOR: SURFACE
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 Approved For Release 2007/09/21 : CIA-RDP81-0012OR000100020071-7
United States
3275,466
METHOD OF A171WF.tZl\G PARTICLES 10 A
SUPPORT SURFACE
Ray I). Kell, Princeton, N!., assignor to Radio Corpora-
tion of America, :a corporatk n of 1)claa?.vare
Filed May ;t, 1965, Ser. No. 457,241
22 Claims. (Cl. 117-33.5)
This is a continuation-in-part of patent application
Serial No. 108,535, filed May 8, 1961, now abandoned.
Both applications were filed by the same inventor and
were assigned to the same assignee.
This invention relates generally to a method of adher-
ing particles to a support. The invention is particularly,
although not exclusively, directed to a method of forming
a very thin layer of colloidal particles, such as phosphor
particles, upon a support surface.
In referring here;, to colloidal-size particles, no limita-
tion to a particular size range of particles is intended.
Rather, the term "colloidal" is used herein in its broad-
est sense to mean a particle of such size that the surface
properties are dominant over the mass properties; for ex-
ample, where surface forces cause a particle to he sus-
pended in a liquid which has a lower density than does
the particle.
In sonic applications, extremely thin phosphor layers
arc desired. One type c.t cathode ray tube particularly
demanding in this respect uses a luminescent screen com-
posed of superimposed layers of different phosphors, each
layer of which emits light of a different color. in the
operation of such a tube, selective penetration of elec-
trons into the screen is obtained either by varying the
velocity of a single electron beam or by using a plurality
of different velocity beams to selectively excite the various
phosphor layers to produce color images. Since color
output is a function of screen penetration by the beam, the
superimposed phosphor layers should be thin in order that
screen penetration from one phosphor layer to another,
and hence color selection, can be effected with a practical
sw?itch;ng signal voltage. In addition to being thin, thc_
screen layers for such a tube should be of uniform thick-
ness and relatively nonporous in the sense that they should
be substantially free of interstices, holes therethrough, or
cavities therein. Where interstices, holes, or cavities do
exist, or where the layer has a thin spot, some electrons
of the beam may pass through one layer and excite the
next, when in fact, this should not occur. In some forms
of this screen, the phosphor layers are separated by inert
spacer layers which may have substantially identical char-
acteristics to the phosphor laycis except that they are non-
luminescent. Such spacer layers provide better color sep-
aration with less critical control requirements.
In addition to thin phosphor layers being useful in
cathode ray tubes operating on the .screen penetration
principle to provide color images, thin phosphor layers
are also useful it other tube applications. For example,
tube applications which require high resolution displays,
such as image tubes and certain oscillograph tubes, find
such than layers useful.
Evaporated pl iosphor layers have been proposed in an
effort to provide nonporous, thin phosphor layers. 'low.
ever. evaporated -'!,osphor layers are typically relatively
low ,n li+;l,t c,'...
rein 1,,
size p:atia e , ..,
particles through
face (substrate).
cause of the rcle
The large size -
than the desire,:
t ffici,ncy, On the other hand the
ot ens of a uirr,cnt. ry-
cef,l.Monty m .'e by ailing the
?:id cushion and onto a support sur-
not i'titable for such thin layers
be- large size of the phosphor particles.
.phor particles arc themselves larger
yer thickness. Moreover, such layers
:tides are inherently porous due to the
3,27:;,466
Patented Sept. 27? 1965
A
large interstices between particles, which are loosely
packed.
In addition to the layers described above, thin uniform
layers Of particles of other e!,ctrenica'.ly-active material
5 arc needed in a multitude of applications. For example,
layers of magnetic, photcconductive, ferroclectric, elec-
trically-insulating, c!cctric..lly-conducting, and electron-
cmissivc, particles may he desired. As with phosphor
particles, 'sedimentary-size particles may be too large,
while vapor-deposited layers may be lacking in some im-
pc;rtant characteristic.
An object of this invention is to provide a novel method
of adh'ning particles to a support surface.
Another object is to provide a novel method of prepar-
15 ing thin, uniform layers of particles upon a support sur-
face.
A further object is to provide a nova method for pre-
p,.ring thin, light-transmitting luminescent screens com-
prising one or more layers of phosphor particles, which
20 layers are characterized by relatively unifotrn thickness
or surface-ta-surface dimensions and nonporous texture,
and which have relatively high light output efficiency.
Another object is to provide a new method of making
luminescent screens which comprise one or more l..,ers of
25 tightly packed phosphor particles.
Generally, the novel method may be used to make a
structure including the elements of: (a) a suppor' surface
and (h) particles. The support surface may be an ex-
tended area of generally planar configuration or may be
30 the surfaces of particles which are many times larger than
the particles to be adhered to the support surface. The
support surface may be the surface of a structui.zt mem-
ber or may he the surface of a layer adhered, either di.
reedy or indirectly to a structural member, as in a mul-
tip!c layer embodiment. Any particles which are insol-
uble may be used in the novel method.
By the novel method, one only of the elements, either
(a) the support surface or (b) the particles, but not both,
is coated with a part icle-adsorptive material; for example,
gelatin. They., the coated element is washed in a solvent
for the coated material until substantially no coeting ma-
terial can be washed from the coated element, thus leav-
ing an adsorbed film of the material on the element.
Than, the support surface is contacted with a dispersion
45 of the particles in a quantity of liquid, the liquid of said
dispersion being substantially free from particle-adsorp-
tive material, whereby particles from the dispersion ad-
here to the support surface. The remaining dispersion
is then washed away.
50 The process may be repated as many times as desired
to build up the thickness of the particle layer, provided,
in each cycle of the process, an adsorbed film of material
is present on one, but not both, of the elements. In one
form of the process, the support surface is coated with
55 the particle adsorptive material, washed, and contacted
with a disp rsiou of uncoated particles, and then this se-
quence of steps is repeated. In another form of the proc-
ess, two dispersions are prepared; one a dispersion of par-
ticles that have been coated with the particle-adsorptive
60 material and washed until no further material can be
washed front the coated particles; and the other a disp er-
?aon of uncoated particles. The support surface is con-
tacted with the one dispersion, is rinsed, is contacted with
the other dispersion, i- rinsed, and then this sequence of
G3
`.f, invent 'n eta; be used as a method of laying C'ovvn
a layer of phosphor particles to provide a novel ii, limes-
ecnt screen by the use of particle-adsorbent films to which
phosphor particles will be attracted and adhere. Such a
film is in1crposed between a support surface and phosphor
particles which are to he formed into a layer on the sup-
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3,276, 4t3(3
,c ; :,chi. ies on r.hich the l;lie phor rarti-
f n c i. i;re .: ct J mays for exa:np'.c,
ether by formic; such a ti!m on :';c su;;,r.rt
farce and then b: thing it wide a liquid rlisper.ioa c.,n-
ainr the layer-formi;rg pho-rhor rart;clcs, or else the
{t may h.e formed r.,t the layer-forming phosphor par-
es Sher;tseives :1n.1 then the support surface bathed with
:quid dispersion of the filmed phosphor particles. In
;ref case phosphor particle, adhere to the support sur-
c in a layer-like deposition.
According to one embodiment of the method of my
ent:axt, a support surface such as a glass faceplate is
screw with such an adsorptive film. The film is then
vcrcj, such as by bathing, a ith a liquid dispersion of
o,phor particles. This results in particles adhering to
Vint. The excess dispcr,ion is tier, removed. These
ps may be repeated any number of times to build up a
icr of phosphor particles to any desired thickness.
Using the method of ;ny invention, a luruiaesccr,t screen
ay be p?c; ared ?.+hich comprises at least one layer built
r of on: or more &,po,itions of closely packed phosphor
rrticlcs. The particle, are ciu-eJ to adhere to each other
Id or to a support surface by extremely thin films, such
s rneiatin film'. interposed th:erebetsseen. The screen is
rbstantially free of interstices which are of the same
rder of size as, or larger than, the phosphor particles
rernselses, the layer being tightly packed and relatively
unporous. Moreover, because phosphor particles are
led, rather than an evaporated film good light output
Chcicecy is Obtained. Also, by using colloidal-size par-
c]cs, very thin layers which are light-transmitting can
made..
The method of the invention may be used to prepare
:;?inr:scent screens suitable for use is pentration type
tt'~ode ray tubes. Such screens may comprise a super-
npos,:d plurality of such phosphor particle layers in
-ither: (I) extended layer form, or (2) multiple coated
article form. In extended layer screens each of the
occrimposed phosphor layers extends completely over
he f:cceplate of the tube. in screens of multiple-coated
t+:rracles the superimposed Ire,*:.rs are formed as super-
imposcd phosphor coatings on etch of a multiplicity of
relatively large particles of, for example, glass or other
phosphor material, which panicles are subsequently de-
- welted in a layer over the faceplate.
The method of the m?ention and illustrative embodi-
ments thereof are described in detail below in conjunction
with the drawings in which:
FIG. I is a longitudinal section of a cathode ray tube
incorporating a luminescent screen;
=Ills. 2 and 3 are enlarged sections of single layer and
;,urltilayer screens, respectively, suitable for use in the
tube of FIG. 1.
FIG. 4 is an enlarged section of a modification of the
nuillilayer screen of FIG. 3.
FIG. 5 outlines a method of making the screens of
FIGS. 1, 2, 3, and 4;
FIG. 6 is a section of a multiple-coated panicle;
FIG. 7 is a modification of the multiple-coated particle
of FIG. fir
F1G. 8 is a section of a rnultilayer luminescent screen
gating FIG. 7 multiple-coated particles; and
Fie;. 9 is a greatly magnified section of a phosphor
layer.
In FIG. 1, a cathode ray tube 10 comprises an envelope
11 includir?c a neck 12, a faceplate 14, gnu an intercon-
rlectinr funnel 16. An electron pan 18 in the neck 12
i, : rf,p led to project a beam 20 of electrons toward the
f:!ee; laic 14. The neck 12 is cosc'I at one end with -
-,,tern structure 22 tltrcuct: -.which a ;rurality of lead-ins
24 are cealcd. Su rahle operating potentials are supplied
to the electron pun I`3 through the lead-ini 24. A cott-
ductisc cnat;nc 26 is provided on the internal surface of
the funnel 16 and serves as an a_e 1. r:,:ing electrode, -A
suitable high voltage p(,;tential is _upplied to the coating
'j
eh-ctrcde 26 uv a terminal means scaled through the
rcnre c:r;ed by the arrow 23.
A rn.,c .:tic de t c,ira ..;t ; 0. :"or eau;n; tea is prosid?:d
,,x dcfcctinc !be etcerron bonne 20 to scan a raster over
the faceplate 14.
A luminescent screen 32 on the internal surface of the
fac,!pla:e 14 comp ri one or more layers of phosphor
particles. The lrunine?cer:t sc-cen 32 may, for example,
comprise a single layer of particles for proJuc;ng either
a single color light output or white light output. Alter..
n:,t;vcly, the screen may comprise a plurality of sup^.rim-
posed layers of phosphor particles for producing light of
different colors.
The present invention may he used in making lumines-
cent screen, of a variety of tyres, including screens for
black and cathode ray tubes and also screens for
multicolor cathode ray tubes. The invention may, for
example, be used in making luminescent screens of the
iy;re prescribed in the cop ending application. Serial No.
108.565, of D. 11. Pritchard entitled "Electrical Devices
and Methods" filed 31.,y S, 1961.
Where a plural inert ;c:cen 32 is provided and is bonn-
barded by electrons of Jitlcrcnt velocities, means may be
provided for preventi::g rater size distortion. Such
means may take Era form of either a me-.h 34 disi o^,ed
transvercciy within the funnel 16 or of her suitable means.
Where the electrode 34 is used, it is connected to the
coating electrode 26 and the tube 10 is opereted accord-
ing to post accclc atian ; 'i- ciples. A separate lead-in
means as indicated schematically by the arrow 36 is pro-
vidcd for supplying suitable electric potentials to the
plural layer screen 32 for e:Tccting color selection. In
the case of a single phosphor layer screen 32, the electrode
34 may be either omitted or else included for the purpose
of obtaining post acceleration operation and its attendant
advantages.
.FIG. 2 illustrate a lunr.nc cent sercert 38 comprising
a single layer 40 of phosphor particles which ?;culd be
used in the tube 10. The layer 40 is characterized by
the particles, thus resulting in a rnultipartic'e thick layer
free of perforations. L'eca;:se the particles are, in this
example, of colloidal size, the layer 40 is very thin and
has zood light tea:a m; sicity. A light-reflective metal
layer 41 of, for example, aluminum, is deposited on the
phosphor layer 4th.
FIG. 3 illustrates a three-layer luminescent screen 48
which is suitable for use in the tube 10 for-producing
color images. The luminescent screen 43 comprises
three superimposed layers S0, 32, and 54 of colloidal
phosphor particles. The superimposed phosphor layers
50, 52, and 54 may be in contact with each other or alter-
nated, as shown, with inert (ncnluminesccat) separator
layers 56 ar.d 53. The separator layers z:6 and 58 may
comprise, for example, particles of mica, vermiculite, col-
loidal silica, bcntonite, kaolin, vanadium ; entoxide, or
talc. They, separator laycrs may be put down in the
manner hereinafter described for putting down the phos-
phor layers 50, 52, and 54. The separator layers 56 and
58 serve, among other things, to reduce color impurity of
the light output. The screen 48 also includes a light-
reflective metal backing layer 59 of, for example, alu-
minum.
A modification of the screen 48 is shown in FIG. 4
wherein like numbers are u'-ed 'o identify like parts of the
screen 43 of FIG. 3. In FIG. 4 a luminescent screen 6C
is shown disposed on the support member 14 and includes
one or rttore relatively thin and nonporous colloidal parti-
cle layers 50 and 52 superimposed c?n a relatively thick,
coarse particle, phosphor layer 62 eompri,cd of larger-
than-colloidal particles of. for example, sedimentary size.
As in the screen 4.13 of FIG. 3 inert separator layers 56
and 53 are provided hctwren adjacent phosphor layers,
and a light reflective metal layer 59 is provided on the
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;.e serer] G"r of FIC. 4 amen e;h r :. ??
of p% a choice of .,scat ;nr,
i,jing down of the frsl plho,rher la}cr 62. For exaul-
ple, the well-known settlin^ method can be used.
Because, in the c.^cration of the tucc 10, it is r.- nece-
sar}' shat th electron rc.1c'r. to thrown iha phos-
phor layer adjacent the faccpl.r;e, that layer rued not ho
extremely thin or nonporous. 7 he porosity of the coar. :
particle layer 62 may he - rcater than th st of the two
layers 50 and 52 nearest the electron gun of the the.
In a hln7ineccent screen of colloidal phosp l of particles.
good light output can be obtained from thin, yet ncn-
phroni, rho her layers. For example, good light out-
put has 1-?c._n obtained from a 3-layer screen 43 having a
total thickness of a few microns.
In laying do'.vn a phosphor particle layer, the novel
n:c:hod ryes films of particle-adsorptive materials havir-g
-11 of - r, i1 the ad_ttion of an acid. Various
a:i.fs can re u2.-d: c,lacial acetic acid h.:% been found to
he suitable.. The degree of ocidity, i.e., the pli, has not
G been found to br critical, except that loo strong an acidifi-
catien, c F., a s 'chop with a pII of much less than 3, may
be detrimental to sorie phosphor materials, The acid
arp c:.rs to increase the affinity of the adsorbent gelatin
film for the res, hor particles which arc subsequently
brought into contact therewith.
Alternatively to, or in combination with, the adding
of acid to the aeeccus gelatin solution, an adsorbent film.
can he given acid bath after it has been deposited on
the support surf:.ce (faceplate 14). The acid bath may
he performed by introducing a quantity of a suitable acid,
for example acetic acid, into the envelope It and slosh-
ing it over the a.!sorhs:7t film on the surface of the face-
plate 14. The excess acid is then poured off.
Following the acid bath, cr the acidified gelatin applica-
protective colloid properties. Some examples of protec-
tive o1!oid materials which have been successively used
are pclatin, polyvinyl alcohol, and certain nnoJifc'3
starches. such :s that sold by Ilercules Powder Company
;Ind de ign:rted by the trade name "Ccron-N." isl:anv
other rn:.te lass are known which have protective colloid
racticing this
be useful in
a
hi
h
p
y
m
c
properties and w
invention. 25 with its support surface. Also, the water bath acts to
The protective colloid, as employed in this invention, remove excess acid left on the adsorbent gelatin film.
when applied to either (but not both) the phosphcr'nnrti a-After pour-off of the water bath, the faceplate 14 is
Iles or the substrate on which the particles are o be de preferably spun to throw off all excess water. The ad-
posited, results in obtaining the desired degree o, af7inhhy sorhent film can be dried to set the gelatin if desired.
and adhesion between the particles and the substrate.. 30 However, this fs nut necessary.
Following tlse spinning off of the water, a dispersion of
CONTINUOUS EXTENDING LAYERS the desired ph. s^tior panicles in a suitable liquid, such
as water, is inrrc-a'uccd into the envelope 11 to bathe the
FIG. 5 outlines a method for making a thin phosphor .. gelatin filmed su`'t ote. If desired, the phosphor disper-
screen such as is illustrated in either of FIGS. 2, 3, cr 4? 3?S sion may be aci died as hereinafter described. A su8i-
In accord: nce with the outline of FR'. the ad-c;scent ' dent quantity of the dispersion is' used to insure good
film can be interposed between the-particle s and their covera _e of the fi mad surface of the faceplate 14. When
support surface either by; (l) the filmed substrate moth the files of the gelatin solution is covered with such a
od whereby a support surface is coated with an adsorbent phosphor-in-water dispersion, phosphor particles become
film and then bathed with a dispersion of unfllared parti- .frt attached to the ant in what is believed to be essentially
cle=, or (2) the filmed particle method .hereby each a monopaiticie :hi:k deposition. Inasmuch as settling is
particle is coated with an adsorbent film and an unfilmcd not the ptincine! action whereby the phosphor }'articles
sup por'. surface is then bathed with a dispersion of the are deposited on the substrate, no harm results from agi-
filmed particles.
FILMFD SUBSTRATE METHOD 45preferred procedu-c. The method of my invention is
gr) tion. as the case may-he, a water bath step is used. Water
is introduced into the envelope 11 and thoroughly sloshed
over the filmed faceplate W. The water is then poured
off. The water 'path step serves the purpose of removing
)~) n7ar:C it viii iC "Ill. at.llvl ,nyu ~] ?. -
strate method t'ch as the la}cr 40 of FIG. 2, an adsorb- still the phosphor di;{,crsion, whether agitated or not, is
tat (flan to v.hiclt phosphor .particles in a liquid dis,-cr- normally performed or a period of time, much less than
sion will become attached is first provided oil a support 5,0 Woould be requir-e for a useful number of phosphor par-
surface, 'itch as the glass faceplate 14. Such a film may tic)es to settle out of the dispersion, even in the complete
he rrcvidcc: by introducing a quantity of a so u{ion of a r