Flat type cathode ray tube

In a flat type cathode ray tube having a small depth relative to an image screen size, electron beams which are generated by heating vertically extending linear thermal cathodes are sequentially and vertically switched by a plurality of vertical scanning electrodes extending vertically and arranged perpendicularly to the linear thermal cathodes, are transmitted through an electron beam generating electrode having apertures formed therein corresponding to the linear thermal cathodes. The electron beams are horizontally deflected by horizontal deflection electrodes, and then directed to a phosphor layer on an image area of a faceplate. The electron beams are modulated by applying a modulation pulse voltage together with a heating D.C. voltage to the linear thermal cathodes, or by applying a modulation pulse signal to a modulation electrode arranged close to the electron beam generating electrode. A large image screen size is attained by the provision of the plurality of vertically extending linear thermal cathodes.

BACKGROUND OF THE INVENTION 
The present invention relates to a flat type cathode ray tube for use in a 
color television receiver set or a computer terminal display. 
A prior art flat type cathode ray tube includes a phosphor plane arranged 
on an inner surface of a vacuum enclosure, a plurality of vertical 
deflection electrodes arranged in parallel and facing relation to the 
phosphor plane and vertically divided at a predetermined pitch, and 
horizontally extending electron guns arranged in a direction of vertical 
scanning on the phosphor plane to emit electron beams. Each electron gun 
comprises a thermal electron source for generating thermal electrons, a 
grid electrode for generating thermal electrons as electron beams 
corresponding to horizontally arranged pixels and modulation electrodes 
for modulating respective beams in accordance with a picture signal. The 
electron beams modulated corresponding to the horizontally arranged pixels 
are directed to a space between the phosphor plane and the vertical 
deflection electrode and a deflection voltage to the vertical deflection 
electrode is sequentially changed so that the phosphor plane is vertically 
scanned by the electron beams. 
In such a flat type cathode ray tube, the electron gun for generating the 
electron beams should generate electron beams one for each of the 
horizontally arranged pixels. Since one pixel in a conventional color 
television image has a size of 0.1-0.2 mm, it is difficult from electrical 
and mechanical standpoints to generate the electron beams at such a pitch 
and modulate them individually. Even if it is possible, it is very 
difficult to keep the spot size of the electron beam constant and keep the 
incident position precision to the phosphor plane constant for all 
electron beams over an electron beam travel path between the electron gun 
and the phosphor plane. Since the voltage on the vertical deflection 
electrode switches from a voltage equal to that of the phosphor plane to a 
deflection voltage, switching takes place at a high voltage and a 
deflection power is fairly large. 
SUMMARY OF THE INVENTION 
It is an object of the present invention to provide a novel flat type 
cathode ray tube which resolves problems encountered in the prior art flat 
type cathode ray tube. 
It is another object of the present invention to provide a flat type 
cathode ray tube with improved electron beam spot size and uniformity, 
reduced deflection power, improved travel position precision of the 
electron beam, improved utilization efficiency of the electron beam and 
with a highly bright image. 
It is another object of the present invention to provide a flat type 
cathode ray tube having a simple structure. 
It is another object of the present invention to provide a flat type 
cathode ray tube which allows beam concentration on a shadow mask at a low 
voltage. 
The flat type cathode ray tube of the present invention comprises one or 
more linear thermal cathodes for generating electrons when heated, 
arranged in a vacuum enclosure in parallel with an image plane at the 
front of the vacuum enclosure, horizontally and spaced apart from each 
other and extending vertically, and a vertical scanning electrode for 
vertically switching electron beams, including a grid electrode having 
openings one for each linear thermal electrode, a horizontal deflection 
electrode for horizontally deflecting the electron beam and a light 
emitting layer made of phosphor which emits light by irradiation of the 
electron beam. The vertical scanning electrode is arranged on the front or 
rear (back) side of the linear thermal cathode. When it is arranged on the 
front side, it has electron beam transmission apertures and a back 
electrode is arranged on the rear side, and the electron beam is taken out 
by an electric field produced between the back electrode and the grid 
electrode. On the other hand, when the vertical scanning electrode is on 
the rear side of the linear thermal electrode, the electron beam is taken 
out by an electric field established between the vertical scanning 
electrode and the grid electrode. 
The electron beam is modulated by applying a modulation voltage to a 
modulation electrode arranged corresponding to the linear thermal cathode 
to be provided with an independent electric potential or applying a 
heating D.C. voltage and a modulating pulse voltage to the linear thermal 
cathode to produce the electron beam in accordance with the modulation 
signal. 
In another embodiment, three electron beams are horizontally deflected in a 
set and irradiated to red, green and blue phosphors on a face plate 
through a shadow mask.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
In order to aid the understanding of the present invention, a typical prior 
art flat type cathode ray tube is first explained. 
As a prior art flat type cathode ray tube, a structure as shown in Japanese 
patent application laid-open No. 46-2619 is shown in FIG. 1. A phosphor 2 
is formed on an inner surface of a vacuum enclosure 1, vertical deflection 
electrodes 3 are arranged extending horizontally, in parallel with and 
opposite to the phosphor 2 and vertically separated from each other by a 
predetermined pitch, and an electron gun for producing respective electron 
beams is arranged to extend horizontally and to be placed at a position of 
extension of the vertical scanning direction of the phosphor plane. In the 
operation of the flat type cathode ray tube of this structure, thermal 
electrons generated by heating an electron source 4 are taken out as 
electron beams 8 from apertures formed in a grid electrode 5 and those 
beams are modulated by a grid elecrtrode 6. The electron beams are 
modulated by electrically grouping the apertures and applying beam 
modulation voltages to the electrodes. The modulated electron beams pass 
through apertures formed in a shield electrode 7 and travel between the 
phosphor plane and the opposing vertical deflection electrode 3, 
straightly where the phosphor plane 2 and the vertical deflection 
electrode 3 are of the same potential V.sub.D and deflected toward the 
phosphor plane 2 where the vertical deflection electrode 3 has a potential 
(V.sub.D -V.sub.CC) lower than the potential (V.sub.D) of the phosphor 
plane 2. The deflection is sequentially performed by each of the vertical 
deflection electrodes 3 to vertically deflect the electron beam. In this 
manner, the conventional television image can be displayed on the phosphor 
plane. 
As described above, in the prior art flat type cathode ray tube, it is 
necessary to horizontally divide the electron beam into as many groups as 
the number of pixels and modulate them individually. Thus, the manufacture 
and control thereof are very difficult. It is also difficult to keep the 
electron beam spot size constant and keep the landing characteristic 
constant for all beams. In addition, a deflection power is high. 
Thus, the prior art flat type cathode ray tube is simple in construction 
but has many problems in the performance. 
The embodiments of the present invention will now be explained. 
FIG. 2 shows a structure of a flat type cathode ray tube in accordance with 
a first embodiment of the present invention. Actually, electrodes are 
contained in a vacuum enclosure (glass vessel), but the vacuum enclosure 
is omitted in FIG. 2 to clearly show the internal electrodes. Only, a 
portion of the face constituting the vacuum enclosure is shown. In order 
to define horizontal and vertical directions of a screen on which an image 
or character is displayed, the horizontal direction (H) and the vertical 
direction (V) are shown on the face plate. A plurality of linear thermal 
cathodes 10 made of tangusten wires having oxide cathodes formed on the 
surfaces thereof are arranged separately and horizontally at regular 
intervals, and appropriate tensions are vertically applied thereto. The 
number of linear thermal cathodes 10 and the space are of a design matter. 
For example, when the diagonal dimension of the display area is 10 inches, 
the horizontal space is approximately 10 mm and 20 linear thermal cathodes 
10 having a vertical length of approximately 160 mm are arranged. 
Electrically isolated and horizontally (H) extending vertical scanning 
electrodes 12 are arranged at a regular pitch in the vertical direction 
(V) on an insulator support 11 positioned close to the linear thermal 
cathodes 10 and opposite to its side of the face plate 9. The vertical 
scan electrodes 12 are metal films or oxide films of conductive material 
and formed by photo-etching, mask vapor-deposition or screen printing. In 
order to display the conventional television image, 490 vertical scan 
electrodes 12 are vertically arranged. Arranged between the linear thermal 
cathodes 10 and the face plate 9 are a first planar grid electrode 13 
having apertures formed at positions corresponding to the linear thermal 
cathodes 10 to focus and accelerate the electron beam, second modulation 
grid electrodes 14 one for each of the linear thermal cathode 10, 
electrically isolated and having electron beam transmission apertures, and 
a third grid electrode 15 having a similar shape to the first grid 
electrode 13. Horizontal deflection electrodes 16 for horizontally 
deflecting the electron beams transmitted through the electron beam 
transmission apertures formed in the electrodes 13, 14 and 15 are arranged 
being electrically isolated and facing the electron beams transmitted 
through the apertures of the electrodes. The horizontal deflection 
electrodes 16 have metal films formed to be electrically isolated on both 
surfaces of substrates such as insulating supports. A layer 17 which emits 
light upon stimulation by the electron beam is arranged on the inner 
surface of the face plate 9. It is formed by a phosphor or a metal-back 
layer. The phosphor may be of one layer for a monochromatic display, and 
red, green and blue stripes or dots are formed for a color display. 
Referring to FIGS. 3 and 4, the operation of the flat type cathode ray tube 
is described. FIG. 3 is a horizontal sectional view of the flat type 
cathode ray tube shown in FIG. 2. Electrons generated by heating the 
linear thermal cathodes 10 pass through the electron beam transmission 
apertures of the first grid electrode 13 opposing to the linear thermal 
cathodes 10, by an electric field established between the vertical 
scanning electrodes 12 on the back of the linear thermal cathodes 10 and 
the first grid electrode B. While the electron beams are not visible, loci 
18 of the electron beams are shown to facilitate understanding. The 
electron beams transmitted through the apertures of the first grid 
electrode 13 are modulated (e.g. on-off modulation) by the second 
modulation grid electrodes 14 each of which corresponds to each of the 
linear thermal cathodes 10 and each of which is electrically isolated from 
the other grid electrodes 14. If the tube is used for a color display, 
sequential modulation signals designated as red, green, blue, red, green, 
blue,--are applied. The electron beams produced by the linear thermal 
cathodes 10 are modulated by respective modulation signals. The third grid 
electrode 15, having a similar shape as the first grid electrode 13, 
presents a shield effect and horizontally focuses the electron beams. The 
horizontal deflection electrodes 16 are arranged one for each linear 
thermal cathode 10 to face the electron beam. A sawtooth or stepwise 
horizontal deflection voltage is applied to the horizontal deflection 
electrodes 16 through wires 161 and 162 so that the electron beams are 
horizontally deflected by a predetermined length. The horizontally 
deflected electron beams are then electrically accelerated and stimulate 
the light emitting layer 17 formed on the inner surface of the face plate 
9 so that the light emitting layer 17 emits lights. When a color display 
is required, the electron beams are horizontally deflected and modulation 
signals for the rspective colors are supplied to the second modulation 
grid electrodes 14 at predetermined positions for the respective colors so 
that a color image is displayed. 
The electron beams 18 produced by the linear thermal cathodes 10 are 
modulated by the modulation signals and horizontally focused and deflected 
so that selected areas of the phosphor 17 emit light as described above. 
The electron beams should also be switched in the vertical direction for 
each scanning line. When the television image is to be displayed, for 
example, as shown in FIG. 4, in order to effect vertical switching of the 
electron beams, 490 electrically separated vertical scanning electrodes 12 
are arranged at the back of the linear thermal cathodes 10. The electrodes 
are formed by metal films or a conductive material such as oxide films on 
the insulator 11 by a photo-etching technique. Alternatively, a metal 
plate may be photo-etched. A vertical scanning signal is applied to each 
of the separated vertical scanning electrodes 12. The applied signal 
effects an "ON" or "OFF" operation of the electron beams. In a first 
field, the electron beam is turned on only for a 1H-period by the signal 
applied to a terminal 12A. The signal for turning on the electron beam 
only for a next 1H-period is applied to a terminal 12C, and so on. Thus, 
similar signals each thereof turning on the electron beam for a 1H-period 
are applied to every other vertical scanning electrode. When the signal is 
applied to a terminal 12X at the bottom of the screen, the scan for the 
first field is completed, and then an interlace scan is initiated to 
vertically scan a second field. In the second field, signals each thereof 
turning on the electron beam only for a 1H-period are applied, starting 
from a terminal 12B to subsequent every other terminals. When the signal 
is applied to the lowermost terminal 12Y, the scan for one frame is 
completed. 
As described above, in the flat type cathode ray tube of this invention, 
the plurality of linear thermal cathodes 10 are arranged at the 
horizontally spaced positions in the vacuum vessel. The vertical scanning 
electrodes 12 of a number corresponding to that of the horizontal scanning 
lines are arranged perpendicularly to the linear thermal cathodes 10 at 
the back of the linear thermal cathodes 10 so that the vertically uniform 
electron beams produced by heating the linear thermal cathodes 10 are 
sequentially turned on and off. Then, the electron beams are modulated by 
the individual separated second modulation grid electrodes 14 which are 
arranged to correspond to the respective linear thermal cathodes 10, and 
then the electron beams are horizontally focused and deflected. Thus, 
light is emitted at predetermined areas on the phosphor plane 17 and a 
combined image, character, etc. is displayed on the screen. 
Referring to FIG. 5, a second embodiment of the present invention is 
explained. In the present embodiment, the second modulation grid 
electrodes 14 in the structure shown in FIG. 2 are omitted and the 
modulation is effected by the linear thermal cathodes 10. 
The operation of the present flat type cathode ray tube is now explained. 
Referring to FIG. 6A, the linear thermal cathodes 211 and 212 are 
continuously powered by a power supply 27 so that they are heated to 
approximately 700.degree. C. and are conditioned to emit electrons. 
However, since a negative voltage relative to the cathodes is applied to 
the counterelectrode (first grid electrode 13) which collect the electron 
beams, the electron beams cannot pass through the beam transmission 
apertures of the counterelectrode. By applying negative pulse voltages 
higher that the voltage of the opposing first grid electrode 13 to the 
linear thermal cathodes by pulse generation/modulation circuits 281 and 
282, the first grid electrode 13 is rendered positive relative to the 
cathodes to cause an electron current to flow so that electron beams 
proportional to the pulse voltage are obtained. Diodes 291 and 292 are 
reverse-biased under this condition so that no current flows to the linear 
thermal cathodes 211 and 212 and potential differences across both ends of 
the respective linear thermal cathodes 211 and 212 are substantially zero. 
Accordingly, all portions of the respective linear thermal cathodes 211 
and 212 possess the same potential and uniform electron currents are 
obtained in the cathodes. Here, pulse-width modulated signals modulated by 
the video signal may be applied to the linear thermal cathodes 211 and 
212. For example, as shown in FIGS. 6A and 6B, in addition to a D.C. 
voltage for heating the linear thermal cathodes, if a color display is 
needed, the pulse-width modulated signals corresponding respectively to 
red, green and blue colors are applied to the linear thermal cathodes 211 
and 212 during a horizontal scanning period so that the electron currents 
modulated by the video signals are obtained. 
Turning to FIG. 5, in the same manner as the first embodiment, pulse 
signals are applied to the vertical scanning electrodes 12 arranged close 
to the back of the linear thermal cathodes 10 so that the vertically 
uniform electron beams produced by the linear thermal cathodes 10 are 
vertically scanned. Then, the electron beams generated by the linear 
thermal cathodes 10 are horizontally focused by the first grid electrode 
13 and the third grid electrode 15, horizontally deflected by the 
horizontal deflection electrodes 16, and then accelerated. Then, the 
electron beams scan predetermined areas of the light emitting layer 17 
formed on the inner surface of the face plate 9, thereby obtaining an 
image. When the light emitting layer 17 is a color screen having red, 
green and blue phosphor stripes, it is a matter of course that the 
positions corresponding to the respective colors on which the horizontally 
deflected electron beams impinge are made to coincide with the timing of 
application of the pulse-width modulation signal to the linear thermal 
cathodes 10. 
As described above, in the second embodiment, the modulation signals such 
as video signals are applied to the linear thermal cathodes 10, so that 
the modulation electrodes 14 provided to correspond to the respective 
linear thermal cathodes 10 in the first embodiment can be omitted. This 
leads to reduction of cost. 
Referring to FIG. 7, a third embodiment is explained. Numeral 10 denotes 
linear thermal cathodes, numeral 12 denotes vertical scanning electrodes 
formed on an insulating support 11, and numeral 13 denotes a first grid 
electrode for forming electron beams. A light emitting layer 17 made of 
phosphor is formed on an inner surface of a face plate 9. While not shown 
in FIG. 7, electrodes for horizontally focusing the electron beams and 
horizontal deflection electrodes are arranged between the first grid 
electrode 13 and the light emitting layer 17, as they are arranged in the 
first and second embodiments. The operation is now explained. The electron 
beams generated by heating the linear thermal cathodes 10 are moved toward 
the light emitting layer 17 by potentials applied to the first grid 
electrode 13 and the vertical scanning electrodes 12. A pulse signal is 
applied to the vertical scanning electrodes 12 to turn on and off the 
electron beams so that the screen is sequentially scanned from the top to 
the bottom. In the first and second embodiments, as many vertical scanning 
electrodes as the number (490) of horizontal scanning lines in the 
conventional television system are provided. In the present embodiment, 
one half (245) of that number of vertical scanning electrodes are 
provided. Assuming that an electron beam is now generated at a position 
corresponding to V.sub.2, potentials V.sub.1 and V.sub.3 of the vertical 
scanning electrodes adjacent to the vertical scanning electrode for 
V.sub.2 are selected to be V.sub.1 &gt;V.sub.3 in the first field so that the 
electron beam from V.sub.2 is slightly deflected toward V.sub.1 as shown 
by a solid line 36a. In the second field, the potentials V.sub.1 and 
V.sub.3 are selected to be V.sub.1 &lt;V.sub.3 so that the electron beam is 
slighty deflected toward V.sub.3 as shown by a broken line 36b. By 
conducting the above operation for each of the vertical scanning 
electrodes, the interlaced scanning of the first field and the second 
field is attained. Since the number of vertical scanning electrodes is 
reduced to one half, the wiring is facilitated and the number of parts is 
reduced. 
Referring to FIG. 8, a fourth embodiment of the present invention is now 
explained. FIG. 8 shows a lateral sectional view of a flat type cathode 
ray tube similar to FIG. 7. Certain electrodes which are not pertinent to 
the present embodiment are omitted. Vertical deflection plates 401 and 402 
for vertically deflecting electron beams are arranged between linear 
thermal cathodes 10 and a face plate 9 which serves as a vacuum enclosure. 
Vertical sanning electrodes 12, which are arranged close to the back of 
the linear thermal cathodes 10 and are of half a number of horizontal 
scanning lines, are arranged being electrically isolated and vertically on 
an insulating support 11. The vertical deflection electrodes 401 and 402 
are planar metal electrodes having vertical bars arranged at double pitch 
with respect to that of the vertical scanning electrodes 12. The bars on 
the vertical deflection electrodes 401 and 402 have a phase difference of 
180.degree. from each other. A signal which turns on the electron beam 
only for one horizontal scanning period is applied to each of the vertical 
scanning electrodes 12 arranged close to the back of the linear thermal 
cathodes 10 so that the electron beams are sequentially and vertically 
switched (scanned) by the signal. For example, the electron beams 43B 
(actually invisible) from the vertical scanning electrode 12B is guided to 
the face plate 9 by a beam guide electrode (not shown) and vertically 
deflected slightly by the vertical deflection electrodes 401 and 402 in 
the first field. The deflection may be effected by making the potentials 
applied to the respective electrodes different. For example, the voltages 
V.sub.401 and V.sub.402 applied to the respective electrodes are selected 
to be V.sub.401 &gt;V.sub.402 so that the electron beam is deflected toward 
the electrode 402. In the second field, the potential relationship is 
reversed (V.sub.401 &lt;V.sub.402) so that the electron beam is deflected 
toward the electrode 401. In this manner, the electron beams in the first 
field and the second field are interlaced to attain the conventional 
television scanning. In the present embodiment, the vertical scanning 
electrodes 401 and 402 are two electrodes arranged in the direction of 
travel of electron beam. Alternatively, electrically divided coplanar 
electrodes may be used to attain the same effect. A single vertical 
deflection electrode having bars arranged at the same pitch as the 
vertical scanning electrodes and offset relative to the vertical scanning 
electrodes may be used with a potential applied to the vertical deflection 
electrode being changed to vertically deflect the electron beams. 
In the present embodiment, since the number of vertical scanning electrodes 
38 is one half of the number of horizontal scanning lines, the wiring is 
simplified, the number of circuit parts is reduced and power consumption 
and cost are also reduced. 
In the present embodiment, the number of grid electrodes, the number of 
linear thermal electrodes and the positions of the electrodes are of 
design matters. For example, the horizontal deflection electrodes may be 
of a plate shape or may be arranged between the first grid electrode and 
the second grid electrode. A single linear thermal cathode may be used. 
The electron beam transmission apertures of the grid electrodes may be 
complete slits or dot-shaped apertures which correspond to the vertical 
scanning electrodes. 
The embodiments of FIGS. 7 and 8 are applicable to the structure shown in 
FIG. 2 having independent modulation electrodes and also to the structure 
of FIG. 5 having no independent modulation electrode and applying the 
modulation signal to the linear thermal cathodes to effect the modulation. 
FIG. 9 shows a perspective view of a fifth embodiment of the present 
invention, and FIG. 10 shows a horizontal sectional view thereof. 
Actually, the respective electrodes are contained in a vacuum enclosure 
(glass vessel) but the vacuum enclosure is omitted in the drawings to 
clearly show the internal electrodes. A portion of a face which serves as 
the vacuum enclosure is shown. 
One or more linear thermal electrodes 10 are arranged at a predetermined 
horizontal pitch and with vertical tension being applied thereto. 
Horizontally extending and electrically separated vertical scanning 
electrodes 12 are arranged at a constant vertical pitch and 
perpendicularly to the linear thermal cathodes 10, on an insulating 
support 11 closely to the back of the linear thermal cathodes 10. To 
display the conventional television image, approximately 480 vertical 
scanning electrodes 12 are vertically arranged. Arranged between the 
linear thermal cathodes 10 and the face plate 9 are a first beam 
generating planar grid electrode 13, a shield electrode 25 and a third 
beam focusing grid 15. Horizontal deflection electrodes 16 for 
horizontally deflecting the electron beams transmitted through the 
apertures of the electrodes 13, 25 and 15 are arranged. The horizontal 
deflection electrodes 16 are formed on both sides of vertically extending 
insulating supports 27 and are arranged symmetrically with respect to the 
center axis of the election beam. A phosphor layer 30 which emits lights 
upon stimulation by the electron beams is formed on the inner surface of 
the face plate 9, spaced from the horizontal deflection electrodes 16, and 
a screen 32 having a metal-back layer 29 formed thereon is arranged. The 
phosphor layer 30 may be a single phosphor layer for monochromatic 
display, and phosphor stripes or dots which emit red, green and blue light 
beams are vertically arranged on the screen for color display. 
The operation of the flat type cathode ray tube is now explained. By 
applying a voltage higher than the potential of the linear thermal 
cathodes 10 to the first grid electrode 13, the electron beams generated 
by heating the linear thermal cathodes 10 pass through the apertures of 
the first grid electrode 13. A voltage equal to or slightly lower than the 
potential of the linear thermal cathodes 10 is applied to the vertical 
scanning electrodes 12, and a video signal is superimposed on the linear 
thermal cathodes 10 so that modulated beams are emitted therefrom. The 
electron beams transmitted through the apertures of the first grid 
electrode 13 pass through the apertures of the shield electrode 25. The 
shield electrode 25 serves to prevent the beam currents from being changed 
by the first grid electrode 13 under the influence of the voltage applied 
to the third grid 15. The electron beams transmitted through the apertures 
of the shield electrode 25 are focused by the third grid electrode 15 into 
small beam spots on the phosphor layer 30 on the screen 32. The election 
beams are horizontally deflected by a sawtooth or stepwise deflection 
voltage having the horizontal scanning period applied to the horizontal 
deflection electrodes 16, and scan the screen 32 to emit light from the 
phosphor layer 30. Since the electron beam emitted from each of the linear 
thermal cathodes 10 is horizontally scanned between the pair of horizontal 
deflection electrodes 16, it constructs a portion of the horizontal lines 
on the screen 32. 
Next, the vertical switching of the electron beams corresponding to 
respective horizontal scanning lines and the beam modulating operation are 
explained. 
As shown in FIGS. 11, 12A and 12B, horizontally extending vertical scanning 
electrodes 12 of a number equal to the number of scanning lines necessary 
for forming an effective screen, for example, 480 for a conventional 
television image, are vertically arranged close to the back of the linear 
thermal cathodes 10, and the vertical scanning signals are applied to 
those electrodes 12. The generation of the beams toward the first grid 
electrode 13 is controlled by changing the voltages of the vertical 
scanning electrodes 12 such that the potential of the space around the 
linear thermal cathodes 10 is positive or negative relative to the 
potential of the linear thermal cathodes 10. Referring to FIGS. 12A and 
12B showing a case of displaying a television image which adopts the 
interlaced system, a signal 12a which turns on the beam (allows the beam 
to be directed to the first grid electrode) only for one horizontal 
scanning period (1H-period) is applied to a terminal 12a in the first 
field, then a signal 12c which turns on the beam only for the next 
1H-period is applied to a terminal 12c and similar signals which turn on 
the beam only for IH-period are sequentially applied to every other 
vertical scanning electrodes, and when the signal is applied to a terminal 
12x at the bottom of the screen, the vertical scan in the first field is 
completed. In the second field, a signal 12b which turns on the beam only 
for IH-period is applied to a terminal 12b, and when a similar signal is 
finally applied to a terminal 12y, the vertical scan for one frame is 
completed. 
The signals applied to the terminals 12a, 12b, . . . 12y shown in FIG. 12A 
are illustrated in FIG. 12B with identical designations. 
Since the linear thermal cathodes 10 are connected to a heating power 
supply 45, there is a potential difference between an input terminal P and 
an output terminal Q of the current. This is shown by a waveform 52 in 
FIG. 12B. Thus, to control the generation of the beams from the linear 
thermal cathodes 10, the signal voltages 12a, 12b, . . . applied to the 
vertical scanning electrodes 12 should be changed such that the potential 
difference between the vertical scanning electrode and the corresponding 
linear thermal cathode 10 is constant, and other electrode voltages should 
also be controlled so that the potential difference from the potential of 
the beam generating linear thermal cathodes 10 is constant. Such 
correction renders the circuit complex and increases power consumption. In 
order to resolve this problem, a sawtooth wave (47 in FIG. 12B) or 
stepwise wave synchronized with the vertical scanning is generated by a 
sawtooth or stepwise wave signal generator 47 in accordance with a 
vertical synchronization signal 50 and it is applied to a linear thermal 
cathode potential correction power supply 46, and a linear thermal cathode 
heating power supply 45 is serially connected to the power supply 46 so 
that the potential of the beam generating area of the linear thermal 
cathodes 10 is always kept constant. By applying a video signal to a video 
signal input terminal 49 and applying a sum of this video signal and the 
output from the stepwise wave signal generator 47 to the linear thermal 
cathode potential correction power supply 46, the electron beams modulated 
by the video signal can be extracted from the linear thermal cathodes 10 
toward the first grid electrode 13. Accordingly, it is not necessary to 
extract the beams from the linear thermal cathodes and modulate them by 
individulally separated modulation electrodes as are done in the prior art 
structure shown in FIG. 1. Therefore, the modulation electrodes are not 
necessary. 
A sixth embodiment of the present embodiment is shown in FIGS. 13 and 14. 
FIG. 13 shows a perspective view and FIG. 14 shows a horizontal sectional 
view. Structual differences from the embodiment of FIG. 9 are that 3n 
linear thermal cathodes 10 are provided, where n is a positive integer, 
the horizontal deflection electrodes 16 are arranged for every third 
linear thermal cathode 10, and a shadow mask 69 is provided between the 
horizontal deflection electrodes 16 and the screen 32 in parallel and 
spaced relation to the screen 32. 
Referring to FIG. 14, the operation is now explained. The operations of the 
linear thermal cathodes 10 and the vertical scanning electrodes 12 are 
identical to those in the embodiment of FIG. 9. Of the three linear 
thermal cathodes, the cathode 10B receives a blue video signal, the 
cathode 10G receives a green video signal and the cathode 10R receives a 
red video signal, and the beams modulated by those signals are directed to 
the apertures of the beam extraction electrode 64. They pass through the 
apertures of the shield electrode 65 and are directed to the beam focusing 
electrode 66, which has an aperture 66G positioned on the center axis of 
the apertures of the beam extraction electrode 64 and the shield electrode 
65 and apertures 66R and 66B positioned on the opposite sides of the 
aperture 66G and having center axes thereof shifted toward the aperture 
66G by a predetermined distance. A plurality of such sets of three 
apertures 66R, 66G and 66B are horizontally arranged. 
Thus, the beam transmitted through the aperture 66G moves along the center 
axis toward the horizontal deflection area. The beams transmitted through 
the apertures 66B and 66R are deflected by the electric field between the 
shield electrodes 65 and the beam focusing electrode 66 so that three 
beams are concentrated to one point on the shadow mask 69. Color phosphors 
are deposited on the areas of the screen to which the beams transmitted 
through the apertures of the shadow mask 69 are directed so that light 
beams in desired colors are emitted. The horizontal deflection electrodes 
16 are formed on both sides of vertically extending insulating supports 27 
and are arranged at the same pitch as the sets of apertures of the beam 
focusing electrode 66 and symmetrically to the center axis of the aperture 
66G of the beam focusing electrode 66 located on the center axes of the 
apertures of the beam extraction electrode 64 and the shield electrode 65. 
FIGS. 15 and 16 show a seventh embodiment of the present invention. Instead 
of the shield electrode 65 in the structure shown in FIGS. 13 and 14, 
modulation electrodes 14 having electron beam transmission apertures one 
for each of the linear thermal cathodes 10 and electrically separated from 
each other are provided. Other electrodes are identical to those shown in 
FIG. 13. The modulation electrodes 14 are arranged such that the electron 
beam transmission apertures thereof coincide with the electron beam 
transmission apertures of the first grid electrode 64, as shown in FIG. 
16. On the other hand, the electrode 66 has an aperture 66G located on the 
common center axis of the aperture of the beam extraction electrode 64 and 
that of the modulation electrode 14 and apertures 66R and 66B located on 
the opposite sides of the aperture 66G and having centers thereof shifted 
toward the aperture 66G by a predetermined distance. A plurality of such 
sets of three apertures 66R, 66G and horizontally arranged. The electrode 
66 serves to focus electron beams and simultaneously to converge three 
electron beams onto one point on the shadow mask 69. 
The operation of the present flat type cathode ray tube is now explained. 
By applying a voltage to the beam extraction electrode 64 such that the 
potential of the beam extraction electrode is higher than the potential of 
the linear thermal cathodes 10, the beams generated by heating the linear 
thermal cathodes 10 are transmitted through the apertures of the beam 
extraction electrode 64. A voltage equal to or slightly lower than the 
potential of the linear thermal cathodes 10 is applied to the vertical 
scanning electrodes 12. The beams transmitted through the beam extraction 
electrode 64 are modulated by the modulation electrodes 14 electrically 
separated one for each linear thermal cathode 10. Looking at one channel 
shown in FIG. 16, red, green and blue modulation signals are applied to 
the modulation electrodes 14R, 14G and 14B. The modulated beams are 
forcused by the beam focusing electrode 66. Since the apertures 66R and 
66B of the beam focusing electrode 66 are offset from the center of the 
modulation electrode 14, the beams 54R and 54B transmitted through the 
apertures 66R and 66B are deflected toward the beam 54G and converged to 
one point on the shadow mask 69. The beams transmitted through the beam 
focusing electrode 66 are horizontally deflected by a predetermined width 
by applying a horizontal deflection voltage, which is a sawtooth or 
stepwise wave having a horizontal scanning period, to the horizontal 
scanning electrodes 16. The beam deflection voltage and the D.C. voltage 
equal to the voltage applied to the screen and the shadow mask are applied 
to the horizontal deflection electrode 16. The beam is focused by an 
electrostatic lens formed by the apertures of the electrode 66 by 
rendering the voltage of the beam focusing electrode 66 to be lower than 
the voltage of the screen voltage. Since the apertures 66R and 66B of the 
electrode 66 are horizontally deviated from the center of the aperture of 
the modulation electrode 14, the beams are deflected by the lens formed by 
the modulation electrode 14 and the beam focusing electrode 66 so that 
three beams are converged into one point on the shadow mask. 
Defocusing of the beam and the convergence error due to the horizontal 
deflection are corrected by applying a correction signal synchronized with 
the horizontal synchronization signal to the beam focusing electrode 66. 
The deflected electron beams pass through the apertures formed in the 
shadow mask 69. Phosphor 30R which emits red light is deposited at the 
position on the screen 32 to which the beam 54R is directed, green 
phosphor 30G is deposited at the position on the screen 32 to which the 
beam 54G is directed, and blue phosphor 30B is deposited at the position 
on the screen 32 to which the beam 54B is directed. Those phosphors emit 
light beams in accordance with the amount of beams directed thereto and 
those light beams are conbined to form a light of a desired color. 
The vertical scanning is identical to that shown in FIG. 4 and the 
explanation thereof is omitted. 
FIG. 17 shows an eighth embodiment of the present invention. A difference 
from the embodiment of FIG. 15 is that an auxiliary focusing electrode 55 
is arranged between the modulation electrodes 14 and the beam focusing 
electrode 66. The auxiliary focusing electrode 55 serves to correct the 
defocusing of the beam when the beam is horizontally deflected, to 
dynamically focus the beam. The dynamic beam focusing and convergence 
correction functions by the beam focusing electrode 66 in the embodiment 
of FIG. 15 are separated in the present embodiment so that the beam 
focusing and the beam convergence correction are facilitated. 
In the embodiment shown in FIG. 17, the beam extraction electrode 64 and 
the modulation electrodes 14 may be arranged in the opposite sequence. 
FIG. 18 shows a ninth embodiment of the present invention. In this 
embodiment, the positions of the vertical scanning electrodes 12 and the 
modulation electrodes 14 shown in FIGS. 15 and 16 are transposed. The 
structure from the horizontal deflection electrodes 27 to the screen 32 is 
identical to that shown in FIG. 15 and the explanation thereof is omitted. 
Video signals are applied to the modulation electrodes 14 and modulated 
beams are emitted from the linear thermal cathodes 10. The beams pass 
through the apertures of the beam extraction electrode 64 and are 
vertically scanned by the vertical scanning electrodes 22. The vertical 
scanning electrodes 22 are separated to be of a number same as that of the 
number of the horizontal scanning lines. Each of the vertical scanning 
electrodes 22 has a horizontally extending slit or a rectangular opening 
which is oposite to the aperture of the beam extracting electrode 64 and 
has a length at least equal to the horizontal length of the aperture. The 
operation is identical to that of the embodiment of FIG. 15, and hence the 
explanation thereof is omitted. The beams transmitted through the vertical 
scanning electrodes 22 are focused onto the shadow mask (not shown) by the 
beam focusing electrode 66 and three beams are converged. The rest of the 
operation is identical to that of the embodiment of FIG. 15. 
The embodiment shown in FIG. 18 can be applied to the embodiment shown in 
FIG. 17. In FIG. 17, the positions of the modulation electodes 14 and the 
vertical scanning electrodes 12 are transposed and apertures are formed in 
the vertical scanning electrodes 12 to attain a similar function. In FIG. 
17, the positions of the beam extraction electrode 64 and the vertical 
scanning electrodes 12 may also be transposed. 
FIG. 19 shows a tenth embodiment of the present invention. A plurality of 
linear thermal cathodes 10 comprising tangusten wires having a diameter of 
10 to 100 .mu.m and having oxide cathodes formed thereon are vertically 
arranged at a constant horizontal pitch, with appropriate tensions being 
applied thereto. The number of linear thermal cathodes 10 and the space 
therebetween are arbitrary. For example, for a television set having a 
display area having a diagonal dimension of 10 inches, approximately 20 
linear thermal cathodes having a length of approximately 160 mm are 
vertically arranged at a horizontal pitch of 10 mm. A back electrode 21 
made of a metal plate or an insulating plate having a conductive layer 
such as a metal layer or oxide formed thereon is arranged on a side of the 
linear thermal cathodes 10 opposite to a side thereof facing the face 
plate 9. Arranged between the linear thermal cathodes 10 and the face 
plate 9 is a first planar grid electrode 13 having apertures for focusing 
and accelerating election beams formed at positions corresponding to the 
linear thermal cathodes 10. Horizontally elongated and vertically arranged 
vertical scanning electrodes 22, which have electron beam transmission 
apertures formed therein and are divided electrically independently into a 
number corresponding to a number of horizontal scanning lines, are 
arranged to be spaced by a predetermined distance from the first grid 
electrode 13. Second modulation grid electrodes 14 each thereof having 
electron beam transmission apertures of a shape similar to that of the 
first grid electrode 13 formed therein and electrically separated from 
each other are arranged corresponding to the linear thermal cathodes 10 
and spaced by a predetermined distance from the vertical scanning 
electrodes 22. A third grid electrode 15 having a shape similar to that of 
the first grid electrode 13 is arranged in spaced relation with the second 
modulation grid electrodes 14. Vertically elongated horizontal deflection 
electrodes 16 for horizontally deflecting the election beams transmitted 
through the electron beam transmission apertures formed in the respective 
electrodes are electrically independently arranged facing each other with 
the electron beam transmission paths intervening therebetween. The 
horizontal deflection electrode 16 may be formed of metal films 
electrically independently disposed on a surface of an insulating support 
or two electrically independent metal plates. A light emitting layer 17 
which emits light upon stimulation by the election beams is formed on an 
inner surface of the face plate 9 by phosphor and a metal-back layer, in a 
spaced relation to the horizontal deflection electrodes 16. For 
monochromatic display, the phosphor may be a single layer, and for color 
display, red, green and blue phosphors are sequentially formed in stripe 
or dot, horizontally on the screen. 
Referring to FIGS. 20, 21A and 21B, the operation of the present flat type 
cathode ray tube is explained. FIG. 20 is a horizontal sectional view of 
the flat type cathode ray tube shown in FIG. 19. The elections generated 
by heating the linear thermal cathodes 10 pass through the electron beam 
transmission apertures of the first grid electrode 13 arranged to face the 
linear thermal cathodes 10, by being driven by an electric field generated 
between the first grid electrode 13 and the back electrode 21 which may be 
a metal plate arranged on the back of the linear thermal cathodes 10, a 
metal film formed on an insulating support 11, or a metal electrode which 
is uniformly coated by an electrically conductive material formed of an 
oxide. In FIG. 20, the election beams are actually invisible, but the loci 
18 thereof are shown to assist easier understanding. The electron beams 
uniformly generated lengthwise of the linear thermal cathodes 10 pass 
through the apertures of the first grid electrode 13 and are divided into 
individual electron beams corresponding to the respective vertical 
scanning lines by the electrically isolated vertical scanning electrodes 
22 which are of a number corresponding to that of the horizontal scanning 
lines of the television system (e.g. 525) and which are arranged 
vertically in the longitudinal direction of the linear thermal cathodes 
10. The operation of the vertical scanning electrodes 22 is now explained 
with reference to FIGS. 21A and 21B. 
Modulating signals for turning on and off the electron beams generated by 
the linear thermal cathodes 10 are sequentially applied to the vertical 
scanning electrodes 22. When the scanning is effected under the standard 
television system (NTSC), in a first field (1F), signals which turn on the 
election beams only for one horizontal scanning period (1H-period) are 
sequentially applied to every other vertical scanning electrodes 22A, 22C, 
. . . 22X, and the scan for the first field is terminated. In a second 
field which is to be interlaced with the first field, signals which turn 
on the electron beams only for 1H-period are sequentially applied to every 
other vertical scanning electrodes 22B, . . . 22Y. When the signal is 
applied to the electrode 22Y, the scan for one frame is completed, and an 
image, character, etc. is formed on the screen. Turning back to FIG. 20, 
the electron beams generated by the linear thermal cathodes 10 are divided 
into beams corresponding in number to the horizontal scaning lines by the 
vertical scanning electrodes 22, and the electron beams are modulated 
(e.g. pulse-width modulated) by the second modulation grid electrodes 14 
which are electrically separated and provided one for each linear thermal 
cathode. Actually, for color display, color sequential modulation signals 
of red, green, blue, red, green, blue, . . . for the image or characters 
to be displayed are applied to the respective ones of the second grid 
electrodes 14. The modulated electron beams are then shielded and 
horizontally focused by the third grid electrode 15 having the similar 
shape as the first grid electrode 13, and they are then horizontally 
deflected by a predetermined width by the horizontal deflection electrodes 
16 so that an opposed pair thereof face an electron beam emitted from each 
linear thermal cathode 10. Sawtooth or stepwise horizontal deflection 
signals are applied to the opposing electrodes of the horizontal 
deflection electrodes 16 through common lines 161 and 162. The 
horizontally deflected electron beams are then electrically accelerated 
and sequentially scan selected positions of the light emitting layer 17 
which is formed on the inner surface of the face plate 9 and comprises the 
phosphor 30 and the metal-back 29. For obtaining color display on the 
screen, the electron beams are horizontally deflected and the modulation 
signals are applied to the second grid electrodes 14 to cause the electron 
beams to impinge on respective predetermined color positions so that a 
color image or character is displayed on the screen. 
Next, an eleventh embodiment of the present invention will be described 
with reference to FIG. 22. A difference from the structure of FIG. 19 is 
that the second modulation grid electrodes 14 of FIG. 19 are omitted. 
Other electrode structures are identical. 
In the operation, the electron beams modulated by the linear thermal 
cathodes 10 are taken out in the same manner as that described in 
connection with FIG. 6. The electron beams generated and modulated by the 
linear thermal cathodes 10 pass through the electron beam transmission 
apertures of the first grid electrode 13 by the potentials applied to the 
back electrode 21 on the back of the linear thermal electrode 10 and the 
first grid electrode 13. Then, the vertically uniform electron beams are 
vertically switched (scanned) and interlaced by the vertically scanning 
electrodes 22 which are perpendicular to the linear thermal cathodes 10, 
correspond in number to the number of horizontal scanning lines and are 
electrically separated from each other. Then, the electron beams are 
focused and horizontally deflected by the third grid electrode 15 and the 
horizontal deflection electrodes 16, respectively so that they scan 
selected areas of the light emitting layer 17, which is formed on the 
inner surface of the face plate 9 and comprises the phosphor layer and the 
metal-back layer, to display the image or character on the screen. 
In the eleventh embodiment, the modulation electrodes 14 arranged one for 
each linear thermal cathode 10 in the tenth embodiment can be omitted by 
applying the modulation signals to the linear thermal cathodes 10. 
FIG. 23 shows a twelfth embodiment of the present invention. In this 
embodiment, the back electrode 21 in FIG. 22 is horizontally and 
electrically divided into sections, one for each linear thermal cathode 
10. Other electrode structures are identical with those in FIG. 22. In the 
present flat type cathode ray tube, pulse width modulation signals 
modulated by video signals are sequentially applied to the back electrodes 
21 arranged corresponding to the respective linear thermal cathodes 10 to 
control the amount of electrons emitted by the linear thermal cathodes 10 
thereby to modulate the electron beams. The subsequent operation is 
similar to that of the embodiment of FIG. 22. 
In the present embodiment, only the heating power supply need be connected 
to the linear thermal cathodes 10 and no special consideration is required 
for the modulation circuit. The modulation back electrodes 21 may be 
divided metal plates, while, they may be electrically isolated conductors 
formed on an insulating support because no provision of electron beam 
transmission apertures is necessary. In this case, it is possible to 
increase the strength of the electrodes and to facilitate the manufacture 
of the electrodes. 
FIG. 24 shows a thirteenth embodiment of the present invention. FIG. 24 is 
a sectional view viewed from a side of the flat type cathode ray tube. 
Certain portions which are not relevant to the present invention are 
omitted. Electron beams generated by heating linear thermal cathodes 10 
extending vertically in parallel to the screen pass through slit or 
dot-shaped apertures formed in a first grid electrode 13 to face the 
linear thermal cathodes 10, by a back electrode 21 arranged on the back of 
the linear thermal cathodes 10 and the first grid electrode 13 which is a 
beam extraction electrode. (Portions 407 and 408 of electron beam flows 
are shown by the continuous lines and broken lines respectively.) The 
electron beams are vertically scanned by turning on and off the electron 
beams by the vertically arranged electrically isolated vertical scanning 
electrodes 22 which are of a number half that of the horizontal scanning 
lines. Then, the electron beams are deflected by applying predetermined 
deflection voltages to the interlace electrodes 405 which are composed of 
two groups of electrode sections alternately supplied with two different 
potentials and which face the beam transmission apertures of the vertical 
scanning electrodes 22. The electron beams are vertically interlaced such 
that the electron beams do not cause the same area of the anode 406 to 
emit light during a scan of each field. The subsequent operation for the 
interlaced electron beams is similar to that in the embodiments of FIGS. 
19 and 22. 
In the present embodiment, the number of vertical scanning electrodes can 
be reduced to one half of the number of horizontal scanning lines. 
Accordingly, the manufacture of the electrodes and the wiring are simpler 
than those in the previous embodiments. 
FIGS. 25A and 25B show another embodiment of the vertical scanning of the 
flat type cathode ray tube of the present invention. 
For a television display, as many vertical scanning electrodes 12 as the 
number of horizontal scanning lines (490) are vertically and electrically 
independently arranged. As shown in FIG. 25A, electric potentials for 
turning off the electron beams generated by the linear thermal cathodes 10 
for a predetermined period are applied to the divided electrodes 12A, 12B, 
12C, . . . 12Z of the vertical scanning electrodes 12. In a first field 
(1V), signals having respective potentials for turning on the electron 
beams only for one horizontal scanning period (1H-period) are applied to 
respective electrically connected electrode pairs 12A, 12B; 12C, 12D; . . 
. ; 12X, 12Y of the vertical scanning electrodes 12 sequentially from 
terminals a.sub.1, b.sub.1, c.sub.1 . . . m.sub.1. Those signals are shown 
in FIG. 25B as waveforms a.sub.1, b.sub.1, c.sub.1, . . . m.sub.1. In a 
second field, the connection of the vertical scanning electrodes is 
changed so that 12B, 12C; 12D, 12E; . . . ; 12Y, 12Z are connected in 
pair. That is, each pair is vertically shifted by one pitch from that in 
the first field. Signals a.sub.2, b.sub.2, . . . m.sub.2 shown by broken 
lines in FIG. 25B and similar to those in the first field are applied to 
lines a.sub.2, b.sub.2, . . . m.sub.2. In this manner, two fields/frame 
scan is effected. In the present method, the interlace scanning is 
effected while the horizontal lines are constructed by using all of the 
vertical scanning electrodes 12 in each field. Because all vertical 
scanning electrodes are used in each field, the efficiency of utilization 
of beam currents is improved, light emitting brightness of the phosphor 
layer is improved accordingly, and a brighter image is obtained. 
In FIG. 25A, the vertical scanning electrodes 12A, 12B, . . . 12Z are 
paired by solid lines and broken lines. It does not mean that they are 
actually connected in this manner but it diagramatically shows the 
connection in the operation. The connection and switching may be readily 
attained by known switching means. 
The present vertical scanning method does not require a specific electrode 
arrangement and can be applicable to any electrode arrangement described 
and shown in the previous embodiments.