Method of producing plasma addressed display device

To provide a method of producing a plasma addressed display device which can prevent a gap unevenness of the liquid crystal layer and cracking of a dielectric sheet due to intrusion of dust as much as possible, a method of production of a plasma addressed display device in which a plasma substrate glass 31 constituting a plasma cell 3 and a dielectric sheet 4 face each other via a plurality of partition walls 4 provided in parallel, wherein parts of the partition walls 5 are formed on the dielectric sheet 4 and, at the same time, parts of the partition walls 5 are formed on the plasma substrate glass 31, and these dielectric sheet 4 and plasma substrate glass 31 are bonded so as to complete the partition walls 6 by combining the parts of the partition walls 5 formed on them with each other.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to a method of producing a plasma addressed 
display device having a liquid crystal cell and a plasma cell superimposed 
on each other with a dielectric sheet therebetween. 
2. Description of the Related Art 
In recent years, a plasma addressed display device formed by superimposing 
a liquid crystal cell and a plasma cell via a dielectric sheet has been 
proposed. FIG. 3 shows an example of this plasma addressed display device. 
The plasma addressed display device of FIG. 3 has a flat panel structure 
wherein a liquid crystal cell 2 and a plasma cell 3 are superimposed via a 
dielectric sheet 4. 
In the liquid crystal cell 2, a color filter substrate 21 is bonded to the 
dielectric sheet 4 at a predetermined clearance via a sealing material 22. 
On the surface of the inner side of the color filter substrate 21, 
strip-shaped data electrodes made of a transparent electrically conductive 
material, which are not illustrated, but extend in the row direction, are 
formed in parallel in a column direction (a perpendicular direction to the 
plane of the figure). A liquid crystal material is filled in the 
clearance, or space, between the color filter substrate 21 and the 
dielectric sheet 4, to form a liquid crystal layer 23. Although not shown 
in FIG. 3, spacers are arranged in the liquid crystal layer 23 so as to 
make the dimensions of the liquid crystal clearance uniform. 
In the plasma cell 3, the plasma substrate glass 31 is spaced from the 
dielectric sheet 4 at a predetermined clearance. On the plasma substrate 
glass 31 on the dielectric sheet 4 side are formed strip-like display 
electrodes 32 made of nickel or the like which extend in the column 
direction and are formed in parallel to one another at a predetermined 
interval in the row direction. On these display electrodes 32, barrier 
ribs 33 made of an insulating ceramic or the like and having a narrower 
width than the display electrodes 32 are formed at an equal pitch to that 
of the display electrodes 32. The plasma substrate glass 31 faces the 
dielectric sheet 4 at a predetermined clearance via these display 
electrodes 32 and barrier ribs 33. These display electrodes 32 and barrier 
ribs 33 constitute the partition walls 5. The sealed spaces defined by 
these partition walls 5 constitute the plasma chambers 34. These plasma 
chambers 34 are formed so as to extend in the column direction at a 
predetermined interval in the row direction. An ionizable gas is sealed in 
the plasma chambers 34. The ionizable gas to be used is, for example, 
helium, neon, argon, a mixture of them, etc. In this way, the display 
electrodes 32 and the barrier ribs 33 serve as the partition walls 5 
defining the plasma chambers and, at the same time, also serve as the 
clearance spacers of the plasma chambers. Note that the display electrodes 
32 are connected to a driver circuit and are driven thereby so as to 
alternately serve as the anode display electrodes 32A and the cathode 
display electrodes 32K. A frit seal 35 of a low melting point glass or the 
like is arranged on the peripheral portions of the plasma substrate glass 
31. The plasma substrate glass 31 and the dielectric sheet 4 are tightly 
bonded by this frit seal 35. 
In the plasma addressed display device, the data electrodes and the plasma 
chambers 34 intersect with each other, the data electrodes serve as column 
driving units, the plasma chambers 34 serve as the row driving units, and 
pixels are defined at the intersections of the data electrodes and plasma 
chambers. 
In such a plasma addressed display device, when a predetermined voltage is 
applied between an anode display electrode 32A and a cathode display 
electrode 32K, part of the gas in that plasma chamber is selectively 
ionized, a plasma discharge is generated, and an internal portion of the 
plasma chamber is maintained at substantially an anode potential. When a 
data voltage is applied to the data electrode in this state, the data 
voltage is written in the liquid crystal layer 23 via the dielectric sheet 
4 at the pixels aligned in the column direction corresponding to the 
plasma chamber 34. When the plasma discharge is terminated, the plasma 
chamber 34 voltage floats, and the voltage written in the liquid crystal 
layer 23 at the corresponding pixel is held until the next write period 
(for example after one frame). At this time, the plasma chamber 34 acts as 
a sampling switch, and the liquid crystal layer 23 at the respective 
pixels acts as sampling capacitors. 
As a result of the operation of the liquid crystal by the data voltage that 
is written from the data electrode 15 to the liquid crystal layer 23 at 
the respective pixels, the display is carried out pixel by pixel. 
Accordingly, by generating a plasma discharge and sequentially scanning 
the plasma chambers 34 in the row direction, which writes the data voltage 
in the liquid crystal layers 23 at a plurality of pixels aligned in the 
column direction, the display of a two-dimensional image can be carried 
out. 
Briefly explaining the method of production of such a plasma addressed 
display device by referring to FIG. 4, first, as shown in FIG. 4(A), a 
display electrode pattern is printed on the plasma substrate glass 31 in 
the form of stripes by, for example, a screen printing method, then these 
stripes are dried or cured to form the display electrodes 32. 
Next, barrier ribs 33 are superimposed on the already formed display 
electrodes 32 by repeatedly screen printing stripes so as to stack the 
ribs on the electrodes as shown in FIG. 4(B). In this case, repeated 
coating is carried out by repeating the screen printing to obtain a height 
of about 200 .mu.m for the barrier ribs 33. After the barrier ribs have 
reached a predetermined height by the printing steps, the assembly is 
sintered and the tops of the barrier ribs are ground to unify the heights 
of the barrier ribs at a predetermined height. 
Then, as shown in FIG. 4(C), a frit seal 35 is formed on the peripheries of 
the plasma substrate glass 31 by a dispenser or the like, the dielectric 
sheet 4 made of glass is placed on the barrier ribs, the dielectric sheet 
is bonded to the plasma substrate glass via this frit seal 35, the plasma 
chambers 34 which are formed thereby are evacuated, and then a gas is 
injected into the chambers. 
Next, a not illustrated orientation processing is carried out. As shown in 
FIG. 4(D), spacers 24 for making the thickness of the liquid crystal layer 
uniform are applied about the dielectric sheet 4. As shown in FIG. 4(E), 
the color filter 21 is bonded to the dielectric sheet 4 via the sealing 
material 22 to form a liquid crystal chamber, and the liquid crystal is 
then injected into the space between the dielectric and the color filter 
to obtain a plasma addressed display device shown in FIG. 3. 
When the dielectric sheet 4 is placed on the barrier ribs 33 and bonded to 
the plasma substrate glass 31, as shown in FIG. 5, dust particles D of 
about 5 to 10 .mu.m or so in diameter is sometimes sandwiched between the 
joined surfaces of the barrier ribs 33 and the dielectric sheet 4. The 
dielectric sheet 4 is a thin glass plate having a thickness of about 50 
.mu.m, and the liquid crystal layer to be formed on the dielectric sheet 4 
has a thickness of about 7 .mu.m, and therefore if dust D having such a 
size is sandwiched between the barrier ribs 33 and the dielectric sheet 4, 
an unevenness of the gap of the liquid crystal layer 23 and as a result an 
unevenness of the liquid crystal display occurs. In addition to this, the 
dielectric sheet 4 which is constituted by the thin glass plate is pressed 
against the barrier ribs 33, and is caused to deform locally as it is 
pressed against the ribs in the parts over the dust particles D and 
sometimes the glass plate cracks. For this reason, a panel in which dust D 
has entered in this way is a sub-standard article and therefore causes an 
increase in manufacturing costs. 
SUMMARY OF THE INVENTION 
The present invention was made in consideration of the above circumstances 
and has as an object thereof to provide a method of producing a plasma 
addressed display device which can prevent unevenness in the gap of the 
liquid crystal layer and the cracking of the dielectric sheet due to the 
presence of dust as much as possible. 
So as to achieve this and other objects, the method of production of a 
plasma addressed display device of the present invention is a method of 
producing a plasma addressed display device wherein a liquid crystal cell 
and a plasma cell are superimposed via a dielectric sheet, a plasma 
substrate glass constituting the plasma cell and the dielectric sheet face 
each other and are spaced apart from each other via a plurality of 
partition walls provided in parallel, wherein parts of the partition walls 
are formed on the dielectric sheet and, at the same time, parts of the 
partition walls are formed on the plasma substrate glass, and the 
dielectric sheets and the plasma substrate glass are joined so as to join 
the parts of the partition walls formed thereon and thereby together form 
the partition walls. 
In this case, it is preferable that the completed partition walls be formed 
by display, or discharge, electrodes formed on the plasma substrate glass 
and by barrier ribs formed on the dielectric sheet. In other words, the 
ribs are on the electrodes so that the walls are made up of the ribs and 
the electrodes. 
Alternatively, it is preferable that the complete partition walls are 
formed by, on one hand, the display electrodes formed on the plasma 
substrate glass and a divided portion of the barrier ribs formed on the 
display electrodes, and, on the other hand, the other divided portion of 
the barrier ribs formed on the dielectric sheet. 
The method of production of the plasma addressed display device of the 
present invention improves the method of production of the partition walls 
constituting the plasma chambers and can reduce the effect of the 
intermixture of dust as much as possible. 
Conventionally, the display electrodes which make-up part of the partition 
walls and the barrier ribs formed on the electrodes were formed on the 
plasma substrate glass, but in the present invention, parts of the 
partition walls are formed on the plasma substrate glass and parts of the 
partition walls are formed on the dielectric sheet and these are joined to 
each other to complete the partition walls. 
According to such a method, the probability of dust invading the joined 
surfaces does not change from the conventional method, but even if the 
dust has invaded the joined surfaces, the dust does not directly come into 
contact with the dielectric sheet, but merely pushes the barrier ribs 
upward. If dust comes into direct contact with the dielectric sheet as in 
the prior art, one-point pressure is caused and the stress is locally 
concentrated in the dielectric sheet, but here the dielectric sheet gently 
deforms and the stress is dispersed and therefore the chance of cracking 
of the dielectric sheet becomes small, there is hardly any gap unevenness 
of the liquid crystal, and there is only a small chance of an adverse 
influence on the quality of the display device. Further, the joined 
surfaces of the barrier ribs are relatively rough and porous, and 
therefore even if dust is sandwiched between the joined surfaces, the dust 
sinks into the rough surface to a certain extent, and so the influence of 
the dust is reduced as a result.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Below, an explanation will be provided of embodiments of the present 
invention by referring to the drawings. FIG. 1 and FIG. 2 are 
cross-sectional views explaining the situation of bonding the dielectric 
sheet and the plasma substrate glass while completing the partition walls 
in the present invention. 
The method of the present example includes a step of, as shown in FIG. 
1(A), forming display electrodes 32 on a plasma substrate glass 31 and 
forming barrier ribs 33 on the dielectric sheet (a thin plate glass) 4 
corresponding to these display electrodes and a step of joining these 
display electrodes 32 and the barrier ribs 33 to complete the partition 
walls 5 when bonding the dielectric sheet 4 and the plasma substrate glass 
31 via the frit seal 35 as shown in FIG. 1(B). 
In this case, the display electrodes 32 can be formed by various methods 
such as a method of performing patterning by photolithography after 
forming a film by the screen printing method, a vapor deposition method 
such as CVD, PVD, or the like, and other methods. As the electrode 
material, a metal such as nickel or the like is preferred, but the 
invention is not restricted to this. 
Also, the barrier ribs 33 are formed at positions corresponding to the 
positions for the display electrodes 32, that is, on the dielectric sheet 
4 with an equal pitch as that for the display electrodes 32. The pitch 
interval is about 0.69 mm in actual circumstances. As the formation 
method, usually a screen printing method is adopted. The printing material 
of the barrier ribs is a paste made by lead, ceramic, a solvent, etc. 
which has an expansion property similar to glass. A sufficient height for 
the walls cannot be obtained by a single printing step, and therefore 
coating is usually carried out a number of times. After the barrier ribs 
are printed to the predetermined height, sintering is carried out. The 
sintering temperature is usually about 570.degree. C. 
In the present example, the barrier ribs 33 are all formed on the 
dielectric sheet 4, and therefore even if dust invades between the barrier 
ribs 33 and the display electrodes 32, the barrier ribs 33 are lifted by 
the amount of the height of the dust, but unlike the case where the dust 
between the barrier ribs 33 and the dielectric sheet 4 gives a localized 
stress to the dielectric sheet, the stress is not concentrated at one 
point, the dielectric sheet 4 (or thin plate glass) gently deforms, and 
therefore there is a little chance of cracking of the dielectric sheet 4, 
and also there is hardly any gap unevenness of the liquid crystal layer. 
In the conventional method in which the barrier ribs 33 are formed on the 
plasma substrate glass 31, after the sintering, usually the surfaces of 
the barrier ribs 33 are ground down. The object of this grinding is to 
make the for exposing the top surface of the ribs the same height for 
placement of the dielectric sheet 4 thereon. Therefore in the present 
example of forming the barrier ribs 33 on the dielectric sheet 4, grinding 
is not a particularly necessary step. Accordingly, in the present example, 
the grinding can be omitted, and therefore it becomes possible to lower 
the cost by reducing the number of the manufacturing steps. 
The steps of the production method of the present example are shown in FIG. 
2. This example has, as shown in FIG. 2(A) of the same figure, a step of 
providing the barrier ribs 33 divided into two portions, an upper and a 
lower portion including forming one of the portions of the barrier ribs 
33a on the dielectric sheet 4; forming the other portion of the barrier 
ribs 33b on the display electrodes 32 formed on the plasma substrate glass 
31; and a step of completing the partition walls 5 by joining these 
display electrodes 32 and portions of the barrier ribs 33a and 33b when 
bonding the dielectric sheet 4 and the plasma substrate glass 31 via the 
frit seal 35 as shown in FIG. 2(B). 
In this case, the formation of the display electrodes 32 and the divided 
barrier ribs 33a and 33b can be carried out in the same way as that 
described above. Also, the respective heights of the divided barrier ribs 
can be appropriately selected. 
In the present example, the rough top surfaces of the divided barrier ribs 
33a and 33b become the joined surfaces, and therefore even if dust 
intrudes between these joined surfaces, the dust is embedded in concave 
portions of the surfaces of the barrier ribs to a certain extent, and 
therefore the effect of reducing the influence of dust is greater than 
that of the first embodiment. Also, the influence by the dust exerted upon 
the dielectric sheet similarly becomes gentle and there is little chance 
of the cracking of the dielectric sheet. Further, the grinding of the 
barrier ribs can be omitted. 
After bonding the dielectric sheet 4 and the plasma substrate glass 31 and 
completing the step as shown in FIG. 4(C), a gas is injected into the 
formed plasma chambers 34. 
Next, a known but not illustrated orientation processing is carried out, 
then as shown in FIG. 4(D), spacers 24 for making the thickness of the 
liquid crystal layer uniform are applied, the color filter 21 is bonded to 
the dielectric sheet 4 via the sealing material 22 to form a liquid 
crystal chamber, and then the liquid crystal is injected between the 
dielectric sheet and the color filter so as to form a plasma addressed 
display device shown in FIG. 2. 
FIG. 6(A) shows an alternate embodiment of the present invention wherein 
upper portions 33a of the ribs are formed on the dielectric sheet 4 and 
lower portions 33b of the ribs are formed on the substrate 31, as in FIG. 
4, for example. However, the electrodes 32 are formed on the top of the 
lower rib portions 33b instead of on the substrate 31. In this way, the 
electrodes 32 are between the upper and lower rib portions 33a and 33b 
when the display is assembled, as shown in FIG. 6(B). As an alternate 
arrangement thereto, the electrodes 32 may be formed on the lower surfaces 
of the upper rib portions. The same structure as shown in FIG. 6(B) would 
result when the display is assembled. 
Yet a further alternative is to provide the entire ribs on dielectric layer 
4 as shown in FIG. 1(A), but to then form the electrodes 32 on the lower 
ends of the ribs. The electrodes on the lower ends of the ribs are pressed 
directly against the substrate 31 when the display is assembled so that 
the same structure as shown in FIG. 1(B) results. 
The present invention is not restricted to the above embodiments. For 
example, it is also possible to form the partition walls only by the 
barrier ribs without the electrodes disposed therebeneath, and other than 
this, change the same in various ways within the scope of the present 
invention. 
Although other modifications and changes may be suggested by those skilled 
in the art, it is the intention of the inventors to embody within the 
patent warranted hereon all changes and modifications as reasonably and 
properly come within the scope of their contribution to the art.