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June 9, 1964
J_ J_ STONE, JR
3,136,917
ELECTROSTATIC WRITING MEANS
Filed March 14. 1960
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287
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SIGNAL SOURCE
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INVENTOR.
Joseph James Sta/1M
United States Patent 0 "ice
1
3,136,917
.
ELECTROSTATIC WRITING MEANS
Joseph James Stone, Jr., Glenview, Ill., assignor to A. B.
Dick Company, Niles, Ill., a corporation of Illinois
Filed Mar. 14, 15960, Ser. No. 14,687
4 Claims. (Cl. 315—12)
3,136,917
Patented June 9, 1964
2
of the present invention, it will be seen that the tube in
dicated at 10 is similar to a conventional cathode ray tube.
It includes an evacuated envelope 12, which carries a
cathode 14, a control. grid 13 connected to a suitable sig
nal source 15, an anode or accelerating electrode 16, a
focus coil 18, and a de?ection coil 20. The cathode is
cimnected to the negative terminal of high voltage sup
This invention relates in general to an improved elec
p y 22.
trostatic printing arrangement, and more particularly to
The de?ection coil 20 is controlled from a suitable de
an arrangement for improving the resolution of images
?ection signal source 28, for controlling the beam pro
secured by means of electrostatic printing tubes.
duced at the cathode 14 while the beam is modulated by
In known electrostatic printing arrangements such as
vthe signals from source 15 for reproducing an image
that disclosed in an application by John S. Tregay, Jr.,
represented by those signals.
?led May 10, 1957, Serial No. 658,275, a conventional
In addition, the tube includes any well known type of
cathode ray tube is modi?ed by the provision of an array 15 face plate 32 of dielectric material in which the wires 34
are carried or embedded. Adjacent the terminations of
of wires in its face, which extend from the interior surface
of the face to the exterior surface. A high voltage beam
the wires, exterior of the ‘tube, a suitable dielectric mate
of electrons is varied in accordance with a desired image
rial 36 is provided for recording the image. It is moved
and traverses the interior terminations of the array of
in the direction indicated by the arrow and has associ
ated on its other side a conductor 38, at ground potential
wires embedded in the non-conductive face of the tube
to cause a discharge through a dielectric or printing paper
passing adjacent to the exterior wire terminations at a
whereby discharge from ‘the wires through the dielectric
is accomplished.
desired speed.
This arrangement although producing
On the inside of the tube 10 and adjacent the interior
satisfactory images does give rise to some di?iculties in
terminations of the wires 34 along the face plate 32 a di
resolution due to the capacitive effect of the wires in the 25 electric coating 40 is provided as may best be seen in
FIG. 2. The coating 40 may be formed by a deposit
matrix.
Thus the dielectric is located between the Wires and an
exterior electrode maintained at ground or anode poten
tial, while the respective wires are charged toward the
cathode potential. This creates a charged condition there 30
of aluminum which is ?red in a properly controlled at
mosphere to form an oxide. A thin conductive coating
44 is then deposited on the coating 40 and is extended to
dielectric, and on initiation of the discharge, it continues
In operation, the primary beam is of course directed to
the various wires 34, in accordance with the desired scan
between which is satis?ed only by discharge through the
until complete. If the discharge period is extended, it
a suitable bias source such as ground. The selection of
the bias is of course dependent on desired characteristics.
may result in poor de?nition of the discharge area
ning rate, while the image reproducing dielectric 36 passes
marked on the dielectric.
35 adjacent the external terminations of the wires.
In addition, the high beam currents produce consider
ably secondary emission which must be controlled in
order to secure good reliable image resolution.
It is, therefore, proposed by the present invention to
The control grid 13 is controlled in accordance with
the signals introduced thereto from signal source 15.
These signals represent the object to be reproduced and
modulate the beam emitted by 14 accordingly. The po
coat the interior surface of the tube with a dielectric coat 40 tential source 22 furnishes a voltage of sufficient magni
ing which prevents any secondary electrons from striking
or contacting the Wires, but at the same time permits the
passage of the high energy beam. In addition, by apply
ing a thin conductive layer to the dielectric coating and
tude to provide a primary beam which penetrates the
layers or coatings 40 and 44 to charge the Wires 34 in
accordance with the modulations introduced from signal
source 15.
Stray electrons which are being emitted from the vari
biasing the same, the secondary electrons emitted as a
result of beam passage through the dielectric are collected
ous components of the tube 10 are prevented from pene
to prevent them affecting image resolutions.
trating the layer 40 and therefore cannot affect image
Accordingly, it is an object of the present invention to
resolution. The secondary or stray electrons emitted as a
provide an electrostatic printing tube having improved
image resolution.
It is another object of the present invention to provide
an electrostatic printing tube in which secondary emis
sion is prevented from interfering with the image.
result of the beam striking the interior terminations of
wires 34 and the face plate 32 are collected along dielec
tric and conducted away by layer 44 to prevent a harm
ful charging effect of these electrons. Thus the effect of
stray and secondary electrons on image resolution is
The features of this invention include the coating of the
reduced to provide improved image resolution.
inner surface of the face plate with a dielectric which 55
In accordance with the above, there has been shown
is only penetrated by high beam current and the provi
and described herein a novel, useful and simple arrange
sion of a biased conductive layer on the coating to dis
ment for improving the operation of an electrostatic writ
sipate the secondary emission effects caused by the beam
ing tube, but the particular embodiments or forms of the
passage.
invention described herein are not limitations upon other
These and other objects, features and advantages of 60 manners of practicing the invention.
this invention will become apparent on reading the follow
ing speci?cation and claims in conjunction with the draw
ings of which:
FIG. 1 is a standard cathode ray tube of the type used
I claim:
1. An electrostatic printing tube in which a pluraltiy
of conductive elements are successively scanned by a
primary electron beam for recording on a dielectric, the
in electrostatic printing modi?ed in accordance with the 65 improvement comprising a dielectric face plate in which
said elements are carried in parallel and insulated one
invention.
from the other, and a dielectric coating covering one sur
FIG. 2 is a partial sectional view showing the manner
face of said face plate and which is penetrated only by
in which the coatings are related to a wire conductor in
said electron beam to charge said elements, in accord
the electrostatic printing tube.
Referring now to FIG. 1 showing a cross section of the 70 ance with desired input signals.
electrostatic printing tube incorporating the principles
2. The arrangement claimed in claim 1 in which a con
3,136,917
ductive coating is carried on the'inner surface of said di-.~ '
electric coating for collecting, secondary electrons caused
by said beam. I
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;
V
V
trable only'by'said beam, ahd a thin'condiictivecoating
over said oxide coating and connected to a suitable bias
’ source for collectingrsecond‘ary electrons emitted by; said a i ’
3. The arrangement claimedv in claim 2 in which said
fbeam striking said- plate, and conductors. ,_
conductive coating is thinner than said dielectric coating, 5
4. An electrostatic printing tube in'which a plurality of,
ReferenceslCited inrthe?le of this patent
conductors extend from the interior‘to the exterior sur
-
UNITED STATES PATENTS
face of the dielectric face of the tube and are charged
- 2,544,690 Koch _._r__’____'i__'__i___.i_rhiar. '13,:1951?
successively by a primary electron beam for ‘enabling a
discharge through a dielectric recording material for re-; 1-0 2,829,025' ‘ Clemens ; _______ _'__-_____ Apr.j'l, 1958
2,879,422
‘Borden. et a1. ____ _..'_.___ Mai‘. 24, 1959'
producing an image, the improvement comprising an alu:
‘ 2,958,002 7' V Cusano et al. _'_ ______ __ Oct. 25, 1960 7‘
minum oxide coating over the interior surface'of said face
Borden _____ _~_____<_____V Apr, 4, 1961' _
72,978,607
and the interior terminations of said conductors and pene~