Information
-
Patent Grant
-
6503116
-
Patent Number
6,503,116
-
Date Filed
Tuesday, October 9, 200122 years ago
-
Date Issued
Tuesday, January 7, 200321 years ago
-
Inventors
-
Original Assignees
-
Examiners
-
CPC
-
US Classifications
Field of Search
-
International Classifications
-
Abstract
The object of the present invention is to provide a phosphor ink applying device that can apply phosphor ink in a plurality of lines to an intricately-shaped surface of a back panel of a PDP while preventing phosphor colors mixing.A valve is provided for the aperture of each nozzle of the phosphor ink applying device and the opening and closing of each valve is controlled according to the shape of the portion of the surface to which ink is to be applied. In this way, mixing of colors can be prevented on an intricately-shaped back panel such as that with auxiliary barrier ribs.
Description
TECHNICAL FIELD
The present invention relates to a color display device used in televisions or computers for image display, and in particular a plasma display panel having phosphor films, a method of manufacturing therefor, and a phosphor ink applying device for use when applying the phosphor film.
BACKGROUND ART
Among various types of color display devices used for displaying images on computers or televisions, Plasma Display Panels (PDPS) have become a focus of attention as color display devices that enable large-size, slimline panels to be produced.
PDPs display in full color according to an additive process of the so-called three primary colors (red, green, and blue). In order to perform this full color display, a PDP is composed of stripe-shaped barrier ribs interposed between a front panel and a back panel, and a phosphor film between each barrier rib that emits light in one of the colors red (R), green (G), and blue (B). Images are displayed by phosphor particles which form the phosphor film being excited by ultra violet rays generated in discharge cells of the PDP. This produces visible light in the colors.
Japanese Laid Open Patent Application H10-27543 discloses a method for forming such phosphor film. In this method, a phosphor ink applying device is used, and ink is continuously discharged from a plurality of nozzle apertures which are provided in a row with a distance therebetween of three times the pitch between each barrier rib. By moving the nozzle over the PDP platform, a plurality of lines of phosphor are applied simultaneously to the grooves between the barrier ribs.
According to this method, phosphor ink is continuously applied to the grooves, resulting in phosphor particles being formed evenly in the lines. Furthermore, applying a plurality of lines simultaneously means that not only can variations between the amount of ink applied to each line be controlled, but also that the amount of time required to apply the phosphor is reduced and work efficiency is improved.
TECHNICAL PROBLEM
In recent years techniques have been developed to improve brightness of PDPs by making the barrier ribs meandering rather than straight lines, or by providing auxiliary barrier ribs at predetermined intervals in the grooves between the barrier ribs (for example, see Japanese Laid-Open Patent Application H10-321148). Here, the auxiliary barrier ribs are lower than the barrier ribs.
FIG. 9
is a perspective view of barrier ribs and auxiliary barrier ribs. As shown in this figure, barrier ribs
1
a
,
1
b
, and
1
c
are formed in striped shapes with intervals therebetween, and auxiliary barrier ribs
2
a
and
2
b
, and
2
c
and
2
d
are formed in the grooves in the intervals between the barrier ribs
1
a
and
1
b
, and
1
b
and
1
c
respectively. Discharge spaces
3
a
and
3
b
are formed in the spaces between each barrier rib and auxiliary barrier rib.
Taking the discharge space
3
a
as an example, phosphor film is formed on side walls
4
and
5
(the side wall
5
is not visible in the diagram) of the auxiliary barrier ribs
2
a
and
2
b
, respectively. As a result, the light emitting area is larger than when auxiliary barrier ribs are not provided, because of the extra area of the side walls, meaning that the brightness of the PDP is improved.
However, when phosphor ink is applied to a back panel which has such auxiliary barrier ribs using the conventional phosphor ink application described earlier, the phosphor ink discharged through the nozzle apertures is applied successively parallel to the barrier ribs by moving the PDP in relation to the phosphor ink applying device. However, this gives rise to a problem in which, for instance, ink applied to the top portion
6
of the auxiliary barrier rib
2
a
flows over the barrier ribs
1
a
and
1
b
into the adjacent discharge spaces which emit light of a different color, causing the colors to mix. This problem can also occur in portions between barrier ribs where the gap is narrow in back panels which have meandering barrier ribs. A PDP cannot perform full color display if such color mixing occurs.
DISCLOSURE OF THE INVENTION
In view of the above-described problem, the object of the present invention is to provide a phosphor ink applying device and a method for manufacturing a PDP for applying phosphor ink in a plurality of lines to an intricately-shaped surface of a back panel of a PDP while preventing phosphor colors mixing, and a PDP formed using the phosphor ink applying device and the method of manufacturing.
In order to achieve the object, the present invention is a phosphor ink applying device for applying phosphor ink in a plurality of parallel line-shapes to a surface of a work according to movement in relation to the work, including a plurality of tanks for storing fed-in phosphor ink, a plurality of nozzle members, each nozzle member having one nozzle aperture which is linked to a storage chamber of one of the tanks, a moving unit for moving the nozzle members in relation to the surface, a pressuring unit for applying pressure to the phosphor ink stored in the tanks so as to discharge the phosphor ink through the nozzle apertures, and a control unit for individually controlling a discharge quantity of phosphor ink discharged through each nozzle aperture, according to a shape of a portion of the surface to which the phosphor ink is to be applied.
According to this structure the discharge quantity of phosphor ink which each nozzle aperture discharges can be controlled individually, even when the portion to which phosphor ink is to be applied is intricately-shaped, therefore phosphor ink can be applied in a plurality of line-shapes simultaneously. This means that when phosphor ink is applied to a substrate of a plasma display panel which has auxiliary barrier ribs, the amount of ink which is applied to the top of the auxiliary barrier ribs can be controlled to be less than that applied to other places. As a result, color mixing due to phosphor ink flowing over barrier ribs can be prevented. Furthermore, the discharge quantity from each nozzle can be controlled, so phosphor ink is only applied where necessary, even if the positions of the nozzles are misaligned in the movement direction relative to the surface. In other words, there is much freedom in the positioning of the nozzles.
Furthermore, if each nozzle member includes a discharge quantity varying unit for varying the discharge quantity through each nozzle aperture, and the control unit controls the discharge quantity of the phosphor ink through each nozzle aperture according to the shape of the portion of the surface to which the phosphor ink is to be applied by driving each discharge quantity varying unit individually, an appropriate quantity of phosphor ink can be applied where necessary even to an intricately-shaped surface.
Furthermore, the pressuring unit may include an applied pressure varying unit for each tank for varying the pressure applied to the phosphor ink, and the control unit may control the discharge quantity of the phosphor ink through each nozzle aperture according to the shape of the portion of the surface to which the phosphor ink is to be applied, by driving each applied pressure varying unit individually.
Furthermore, the phosphor ink applying device of the present invention is for applying phosphor ink in a plurality of parallel line-shapes to a surface of a work, including one or more tanks for storing fed-in phosphor ink, a plurality of nozzle members, each nozzle member having one nozzle aperture linked to a storage chamber of one of the tanks, a moving unit for moving the nozzle members in relation to the surface, a pressuring unit for applying pressure to the phosphor ink stored in the tanks so as to discharge the phosphor ink through the nozzle apertures, a discharge quantity varying unit being provided for each nozzle aperture and varying a discharge quantity of phosphor ink to which pressure is applied, and the control unit controlling the discharge quantity of the phosphor ink through each nozzle aperture according to the shape of the portion of the surface to which the phosphor ink is to be applied, by driving each discharge quantity varying unit individually.
According to this structure, when phosphor ink is applied to a substrate of a plasma display panel in the same manner as described above, mixing of colors can be prevented. In addition, a plurality of nozzle apertures are provided for one tank, meaning that the number of tanks can be reduced and the phosphor ink applying apparatus can be made compactly.
Here, if the nozzles are positioned misaligned in the direction of relative movement, phosphor ink can be applied with the distance between adjacent line-shaped phosphor ink shortened.
Furthermore, the discharge quantity varying unit can be used as a flow path resistance unit for varying the discharge quantity by varying the flow path resistance of the phosphor ink through the nozzles. Specifically, a valve can be used as the discharge quantity varying unit.
A specific example of the object to which phosphor ink is applied is a substrate for a plasma display panel.
Furthermore, the moving unit includes a slideable table for carrying a substrate of a plasma display panel that has the barrier ribs provided in a row, and each nozzle is provided above the grooves formed between the barrier ribs of the substrate for the plasma display panel carried by the moving table. Therefore, phosphor ink can be applied in the grooves of the substrate carried by the table, in parallel, in accordance with the movement of the moving table.
Furthermore, he method of the present invention for manufacturing a plasma display panel, is a method including an ink application process for applying to a substrate for a plasma display panel which has (a) a plurality of first barrier ribs provided so grooves are formed therebetween, and (b) second barrier ribs which are provided at a predetermined interval in the grooves and which have a height lower than the first barrier ribs, phosphor ink in a line shape parallel to the first barrier ribs in each groove successively, and including, in the ink application process, the quantity of phosphor ink applied to walls of the second barrier ribs being less that the quantity of phosphor ink applied to areas between the second barrier ribs. According to this structure, flow of the phosphor ink applied to the gaps between the second barrier ribs over the first barrier ribs can be suppressed, meaning that color mixing on the substrate can be suppressed.
Furthermore, the method of the present invention for manufacturing a plasma display panel, is a method including an ink application process for applying to a substrate for a plasma display panel which has (a) a plurality of first barrier ribs provided so grooves are formed therebetween, and (b) second barrier ribs which are provided at a predetermined interval in the grooves and which have a height lower than the first barrier ribs, phosphor ink in a line shape parallel to the first barrier ribs in each groove successively, and including, in the ink application process, the quantity of phosphor ink applied to walls of the second barrier ribs being less than the quantity of phosphor ink applied to areas between the second barrier ribs. According to this structure, flow of the phosphor ink applied to the gaps between the second barrier ribs over the first barrier ribs can be suppressed, meaning that color mixing on the substrate can be suppressed.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1
is a plan view of a PDP from which a front glass substrate has been removed;
FIG. 2
is a partial perspective and sectional view of the PDP;
FIG. 3
is a partial perspective and sectional view of the PDP to show the structure of the barrier ribs and the auxiliary barrier ribs;
FIG. 4
is a perspective view of the phosphor ink applying device;
FIG. 5
is a front view of a phosphor ink discharge device;
FIG. 6
is a time chart showing the control method of an ink discharge quantity of the phosphor ink discharge device;
FIG. 7
is an outline view showing the arrangement of the ink discharge devices in a variation of the first embodiment;
FIG. 8
is a partial perspective and sectional view of the structure of the nozzle member of the phosphor ink discharge device of the second embodiment; and
FIG. 9
is a partial perspective and sectional view of barrier ribs and auxiliary barrier ribs of a PDP.
BEST MODE FOR CARRYING OUT THE INVENTION
(First Embodiment)
The following explains an embodiment of a phosphor ink applying device to which the present invention is applied, with reference to the drawings.
<Structure of a PDP>
The following explains the structure of a PDP
100
, during the manufacturing of which phosphor ink is applied by a phosphor ink applying device.
FIG. 1
is a plan view of a the PDP
100
from which a front glass substrate
101
has been removed, while
FIG. 2
is a partial perspective and sectional view of the PDP
100
. Note that in
FIG. 1
some display electrodes
103
, display scan electrodes
104
, and address electrodes
107
are omitted for simplicity's sake. The construction of the PDP
100
is explained using these diagrams.
In
FIG. 1
, the PDP
100
is made up of a front glass substrate
101
(not illustrated), a back glass substrate
102
, N display electrodes
103
, N display scan electrodes
104
(please note that a number is extra to ‘N’ to express the ‘Nth’ electrode), M address electrodes
107
(please note that a number is extra to ‘M’ to express the ‘Mth’ electrode), and a hermetic sealing layer
121
which is shown by diagonal lines. The electrodes
103
,
104
, and
107
together form a matrix of a three-electrode structure. The areas where the display scan electrodes
104
intersect with the address electrodes
107
are cells.
In the PDP
100
, as shown in
FIG. 2
, a front panel and a back panel are placed parallel to each other with a gap therebetween. The front panel is composed of a front glass substrate
101
on which the display electrodes
103
, the display scan electrodes
104
, a dielectric glass layer
105
, and an MgO protective layer
106
are arranged on one main surface. The back panel is composed of a back glass substrate
102
on which the address electrodes
107
, a dielectric layer
108
, barrier ribs
109
, auxiliary barrier ribs
111
, and phosphor films
110
R, G, and B are arranged on a main surface. The gap between the panels is divided by stripe-shaped barrier ribs
109
, and gaps between the barrier ribs are further divided by trapezoid auxiliary barrier ribs
111
which are formed in the groove between each barrier rib
109
. In the groove between each barrier rib
109
, a discharge space
122
which includes the wall surfaces of the auxiliary barrier ribs
111
and in which red, green, and blue phosphor film is formed, and discharge gas is sealed therein.
FIG. 3
is a partial perspective and sectional view of a PDP from which the front panel has been removed to show the structure of the barrier ribs
109
and the auxiliary barrier ribs
111
. As shown in the figure, discharge cells
122
are formed between the adjacent stripe-shaped barrier ribs
109
and the auxiliary barrier ribs
111
therebetween. These areas are unit cells, and each cell is separated.
The auxiliary barrier ribs
111
are formed so as to have a height Hh from the back glass substrate
102
(including the dielectric layer
108
) that is lower than a height Hs of the barrier ribs
109
from the back glass substrate
102
. A phosphor film is also formed on the top portion
111
a
and the side surface portion
111
b
of each auxiliary barrier rib
111
. As a result, the light emitting area is larger than when auxiliary barrier ribs are not provided, because of the extra area of the side walls, meaning that the brightness of the PDP
100
is superior to a PDP which does not have auxiliary barrier ribs.
The PDP
100
is connected to and driven by a PDP driving device which is not illustrated. When the PDP
100
is being driven, a driver circuit, a display scan driver circuit, and an address driver circuit which are not illustrated are connected. In order to illuminate the PDP
100
, pulse voltage is applied to the display scan electrodes
104
and the address electrodes
107
, and after address discharge is performed therebetween, pulse voltage is applied between the display scan electrodes
104
and sustained discharge is performed. According to the sustained discharge, ultra-violet rays are generated in the appropriate cells, and the phosphor particles excited by these ultra-violet rays emit light. This causes the cell to be illuminated, and images are displayed by combinations of each cell either being illuminated or not.
<Method for Manufacturing the PDP
100
>
Next, a method for manufacturing the above-described PDP
100
will be explained with reference to FIG.
1
and FIG.
2
.
1. Manufacturing of the Front Panel
The front panel is manufactured by first forming n display electrodes
103
and display scan electrodes
104
(in
FIG. 2
only two of each are shown) alternatively so as to be parallel in stripe shapes, covering the result with a dielectric glass layer
104
, and then forming an MgO protective layer
106
.
The display electrodes
103
and the display scan electrodes
104
are made of silver, and are formed by applying electrode silver paste by screen printing and then firing the result.
The dielectric layer
105
is made to a predetermined thickness (approximately 20 μm) by applying a paste which includes lead glass by screen printing, then baking the result for a predetermined amount of time at a predetermined temperature (for example, 20 minutes at 560° C.). As an example of the paste which includes lead, a mixture of, for instance, PbO (70 wt %), B
2
O
3
(15 wt %), SiO
2
(10 wt %), Al
2
O
3
(5 wt %), and an organic binder (10% of ethyl cellulose dissolved in α-terpineol) is used. The organic binder is a substance obtained by dissolving a resin in an organic solvent. A resin such as an acrylic resin and an organic solvent such as butyl carbitol may be used instead of etyle cellulose and α-terpineol. Also, a dispersant (for example glycertrioleate) maybe mixed into the organic binder.
The MgO protective layer
106
is made from magnesium oxide (MgO), and is formed to a predetermined thickness (approximately 0.5 μm) by, for instance, sputtering, or CVD (chemical-vapor deposition).
2. Manufacturing of the Back Panel
First, a silver paste is applied to the surface of the back glass substrate
102
by screen printing, and then the result is fired to form the m address electrodes
107
in alignment. Then, a paste containing lead glass is applied to the surface of the back glass substrate
102
to form the dielectric layer
108
. Next, a paste containing the same kind of lead glass substance is repeatedly applied in a predetermined pitch to the surface of the dielectric layer
108
by screen printing, and the result is fired to form the barrier ribs
109
and the auxiliary barrier ribs
111
.
Once the barrier ribs
109
and the auxiliary barrier ribs
111
have been formed, each color of phosphor ink is applied by a phosphor ink applying device (explained later) as the green phosphor ink in
FIG. 3
is applied in a direction of an arrow A in a predetermined cell. The phosphor ink is a paste adjusted to an appropriate viscosity (for example, 0.1 to 100 Pa·s (100 to 100000 CP)) and is composed from red (R), green (G), or blue (B) phosphor particles, an organic binder, a dispersant, a solvent, and so on. The phosphor particles can be those used generally in PDP phosphor films.
The following is a specific example:
Red phosphor: (YxGd
1−x
)BO
3
:Eu
3+
or YBO
3
:Eu
3+
Green phosphor: BaAl
12
O
19
:Mn or Zn
2
SiO
4
:Mn
Blue phosphor: BaMgAL
10
O
17
:Eu
2+
Phosphor ink which uses this kind of phosphor particles is applied to the top portions and the side wall portions of the auxiliary barrier ribs
111
, but the amount of ink applied to these portions is set according to an application method, which will be described later, to be relatively less than that applied to other portions. This prevents mixing of inks of different color cells.
Next, the result is fired at 400 to 590° C., and the organic binder is burnt away, resulting in the phoshor particles being fixed to the substrate and the phosphor films
110
R,
110
G, and
110
B being formed.
3. Manufacturing of the PDP by Sealing the Panels Together
The front panel and back panel manufactured as described above are laminated so that the electrodes of the front panel intersect at right angles with the address electrodes of the back panel. Sealing glass is interposed between the front and back panels along their edges, and the result is fired at a temperature of around 450° C. for 10 to 20 minutes to form the airtight hermetic sealing layer
121
(FIG.
1
). As a result, the front and back panels are sealed together. Once the inside of the discharge spaces
122
has been exhausted to form a high vacuum (for example, 1.1×
10−4
Pa), a discharge gas (for example and inert gas of He—Xe or Ne—Xe) is enclosed in the discharge spaces
122
at a certain pressure. This completes the PDP
100
.
<Structure of the Phosphor Ink Applying Device>
Next, the phosphor ink applying device used when applying phosphor paste to the back panel will be explained.
FIG. 4
is a perspective view of the overall structure of a phosphor ink applying device
10
. Please note that the angles at which phosphor ink discharge devices
721
a, b
, and
c
are arranged along the y-axis are exaggerated to aid understanding.
As shown in the drawing, the phosphor application device
10
is composed of a moving table unit
30
which moves over a base
20
, an ink discharging unit
70
which is fixed by a discharge device moving unit
50
, and a controller
90
. The phosphor application device
10
applies ink which is discharged by the ink discharging unit
70
by moving the moving table unit
30
at a constant speed over the PDP back panel.
<Moving Table Unit
30
>
The moving table unit
30
carries the back panel P on which barrier ribs and auxiliary barrier ribs are formed (These barrier ribs and auxiliary ribs are not illustrated in
FIG. 4
however, the barrier ribs
109
are formed in an along the y-axis.), and holds the back panel P moveably along the y-axis for applying the phosphor. The moving table unit
30
is composed of a base
300
, a platform
320
and a driver
340
.
The base
300
has opposing rails
301
, and is positioned so as to move along the y-axis. The rails
301
fit together with guides
322
of the platform
320
to hold the platform
320
slideably along the y-axis.
The platform
320
carries the back panel P, and is composed of a moving table
321
, and guides
322
. The moving table
321
is a flat plate. The guides
322
have C-channel-shaped cross sections, and are provided on either side of the moving table
321
along the x-axis. The platform
320
slides back and forth along the y-axis according to the working of the belt of the driver by being partly linked to the belt.
The driver
340
is composed of pulleys
341
, a belt
342
, and a driving motor
343
. The belt
342
is strung around the opposing pulleys
341
(only one of which is visible in the figure), and at least one of the pulleys is rotatably supported by the driving motor
343
. A pulse motor is an example of the type of motor used. The platform
320
, which is linked to the belt
342
, moves back and forth along the y-axis according to the rotations of the motor being precisely controlled.
<Discharge Device Moving Unit
50
>
The discharge device moving unit
50
holds the ink discharging unit
70
to be moveable back and forth along the x-axis, and is composed of a supporter
500
and a discharge device driving unit
520
.
The supporter
500
is composed of a support base
501
, and a discharge unit supporter
502
. The support base
501
fixes the discharge unit supporter
502
and is itself fixed to the base
20
. The discharge unit supporter
502
is a guide which has a C-channel-shaped cross section and the hollow thereof and the support base
701
of the ink discharging unit
70
fit together to hold the ink discharging unit
70
to be moveable back and forth along the x-axis.
The discharge device driving unit
520
holds the ink discharge unit
70
to be moveable back and forth in the x-axis, and is composed of a rotating rod
521
, a holder
522
, pulleys
523
and
524
, a belt
525
, and a driving motor
526
. The rotating rod
521
is provided with a screw groove. The holder
522
holds the rotation rod
521
rotatably. The pulleys
523
and
534
are provided at one end of the rotating rod
521
and on the rotating axis of the driving motor
526
, respectively, to transfer rotation. The driving motor
526
drives the pulley
524
, and the belt
525
which is strung between the pulleys
523
and
524
.
The rotating rod
521
is rotated via the pulley
524
, the belt
525
, and the pulley
523
according to the driving of the driving motor
526
. The male groove of the revolving rod
521
screws together with a female thread portion (not illustrated) provided on the supporter
701
, and screwing action which occurs due to the revolutions of the driving motor
526
allows mobility of the ink discharging unit
70
back and forth along the x-axis. Here, when the driving of the driving source of the driving motor
526
can be accurately controlled, such as with a pulse motor, the position of the driving source on the x-axis can be measured from the driving amount, by providing a basic position sensor such as a optical position sensor (for example a CCD camera), which detects when the motor passes a basic position on the x-axis.
<Ink Discharge Unit
70
>
The ink discharge unit
70
discharges phosphor ink between each barrier rib
109
of the back panel P, and is composed of a supporter
700
and an ink discharge device
720
.
The supporter
700
is composed of support bases
701
and
702
. The support base
701
supports the ink discharge unit
70
overall, while the support base
702
is fixed by the support base
701
and supports the ink discharge device
720
.
The support base
701
is a flat plate which has a protruding portion
703
on one end. The protruding portion
703
fits together with the discharge unit supporter
502
described earlier, holding the support base
701
moveably along the x-axis.
The support base
702
is stepped-shaped, having three linked steps, each of which has a different length on the y-axis. Each of the steps supports one of the phosphor ink discharge devices
721
a, b
, and
c
. According to this structure, the phosphor ink discharge devices
721
a, b
, and
c
are fixed at a predetermined angle and so as to line up diagonally in relation to the y-axis (misaligned in the movement direction of the moving table
321
). The distance along the x-axis between the phosphor ink discharged by each phosphor ink discharge device is three times the distance between barrier ribs (about 160μ to 360 μm). The reason for the distance being three times is that the same color of phosphor ink is applied at three times the pitch between the barrier ribs. By placing the phosphor discharge devices misaligned along the y-axis, the apparaus can be designed so that the distance between the barrier ribs is adjustable and can be set to be closer.
The ink discharge device
720
is composed of phosphor ink discharge devices
721
a, b
, and
c
, a pressuring device
760
for applying pressure to discharge ink, and a delivery pump
770
for delivering phosphor ink to the phosphor ink discharge devices. Phosphor ink that is delivered by the delivery pump is stored in the phosphor ink discharge devices
721
a, b
, and
c
, and is forced out by pressure from the pressuring device
760
.
Air compressors and so on are used in the pressuring device
760
to supply air at a constant pressure. In addition, a pump such as a plunger pump or a gear pump which can deliver viscous paste is used as the delivery pump
770
.
Please note that the driving motor
343
of the moving table unit
30
, the driving motor
526
of the supporter
500
, and a valve driver
754
(which will be explained later) of the ink discharge device
70
are controlled by operations of the controller
90
. The controller
90
is composed of CPU, a memory, and an operator input unit (a keyboard for instance), which are not illustrated. Phosphor ink applying operations, which will be explained later, are executed based on a control program stored in the memory according to the driving of the driving motors
343
and
526
, and the valve driving unit
754
.
<Structure of the Phosphor Ink Discharge Devices
721
a, b
, and
c>
The following is an explanation of the phosphor ink discharge devices
721
a, b
, and
c
which have a structure which characterizes the present invention. Please note that as each of the devices have the same structure, the phosphor ink discharge device
721
a
will be used as an example.
FIG. 5
is a front view of the overall structure of the phosphor ink discharge device
721
a
. In order to explain the internal structure some ordinarily non-visible portions are shown by broken lines.
In the figure, the phosphor ink discharge device
721
a
is composed of a lid member
730
, a tank member
740
, and a nozzle member
750
.
The lid member
730
is composed of a stainless steel plate member
731
, and an induction mouth
732
is provided in the center of the main surface thereof for compressed air which is sent from the pressuring device
760
. The phosphor ink discharge device
721
a
is linked the pressuring device
760
by a line L
1
which brings the compressed air to the induction mouth
732
. Please note that the plate member
731
is sealed and fastened with screws by packing, which are not illustrated.
The tank member
740
is composed of a tank
741
which is manufactured by grinding processing of stainless steel material. An induction mouth
742
is provided on the top of one side of the tank
741
. The induction mouth
742
and the delivery pump
770
are connected by a line L
2
. Phosphor ink that is sent from the delivery pump
770
is stored in the tank
741
through the line L
2
which is connected to the induction mouth
742
. Please note that an outlet
743
is provided at the other end of the tank
741
. Phosphor ink stored in the tank
741
is successively delivered to the nozzle member
750
according to the pressure of the compressed air via the outlet
743
.
The nozzle member
750
discharges, in a predetermined narrowness, phosphor ink that is sent from the tank member
740
, and is composed of a square member
751
, a nozzle aperture
752
, a valve
753
, and a valve driver
754
. The nozzle aperture
752
is formed in along the z-axis by making an opening through the square member
751
. The valve
753
is provided partway along the nozzle aperture
752
and is for varying the discharge quantity of the phosphor ink. The valve driver
754
drives the opening and closing of the valve
753
.
The square member
751
has a space for disposing the nozzle aperture
752
, and the valve
753
partway along the nozzle aperture
752
. In addition, the valve
753
is mounted in the square member
751
so as to be linked with the nozzle aperture
751
.
The nozzle aperture
752
is a stainless steel material (for instance SUS304) which is shaved on a lathe so as to make a cylindrical aperture, and is subjected to a mirror surface processing according to electrolytic polishing so that friction resistance of phosphor ink that flows through is reduced to a minimum. The diameter of the nozzle aperture
752
is normally set at about 45μ to 150 μm which is narrower than the distance between barrier ribs
109
(approximately 160μ to 360 μm).
The valve
753
uses, for example, a needle valve and an air pressure control valve (both manufactured by SMC Corporation), and these valves are opened and closed by the driving of the valve driver
754
. By controlling the opening and closing subtly, the flow path resistance of the phosphor ink which passes through the nozzle aperture
752
varies, meaning that the discharge quantity can be controlled.
The valve driver
754
controls the valve
753
subtly to open and close the valve
753
.
According to the above-described construction, pressure is applied by compressed air being provided through the line L
1
to phosphor ink provided through the line L
2
, the phosphor ink is discharged through the nozzle aperture
751
, and the discharge quantity can be varied according to the opening and closing of the valve.
Please note that here that lines branch out to each of the phosphor ink discharge devices
721
a, b
, and
c
from one pressuring device
760
and one delivery pump
770
to supply phosphor ink, but a pressuring device
760
and a delivery pump
770
may be provided for each of the phosphor ink discharge devices
721
a, b
, and
c
, in which case branching out of lines would be unnecessary.
<Method of Applying Phosphor Ink>
Next, a detailed explanation will be given of a process of applying phosphor ink to the back panel using a phosphor ink applying device having the above-described structure.
1. Settings of the Phosphor Ink Applying Device
Returning to
FIG. 4
, various settings of the phosphor ink applying device will be described.
First, in order to carry the back panel, the driving motor
343
is controlled, so that the moving table
321
is put in a position in which its end is aligned with the ends of the rails
301
(in a direction towards the front of the drawing).
Then, the back panel on which barrier ribs
109
and auxiliary barrier ribs
111
have been already formed is mounted horizontally on the moving table
321
so as to be in a predetermined position and so that the barrier ribs
109
are parallel to the y-axis. The back panel is industrially produced and has barrier ribs and auxiliary barrier ribs formed in predetermined positions, therefore it is considered that when the back panel is mounted on the moving table
321
that there will be barrier ribs and auxiliary barrier ribs in the predetermined positions. In other words, information about such things as the positions and shapes of the barrier ribs and the auxiliary barrier ribs is input beforehand through the operator input unit of the controller, so the positions of the barrier ribs and auxiliary barrier ribs when on the moving table
321
are already set.
Here, the positions of the barrier ribs and auxiliary barrier ribs can measured and revised if the surface of the back panel is formed having one or more positioning marks and the phosphor ink discharge device has an optical sensor to detect the marks. Alternatively, the optical sensor can be made to detect the barrier ribs and the auxiliary barrier ribs themselves, rather than the marks. The optical sensor can be, for example, a CCD camera or a laser displacement gauge.
Next, the discharge quantity from the nozzles of the phosphor ink discharge devices
721
a, b
, and
c
is made to be constant by adjusting the pressure of the pressuring device
760
and the quantity delivered by the discharge pump
770
, through the operator input unit. Here, there is a danger that variations will occur in the discharge quantity from the phosphor ink discharge devices due to errors when the device is started up. In such cases, the quantity of phosphor ink discharged from the phosphor ink discharge devices is measured over a set period of time and the variations are calibrated by adjusting the opening and and closing of the valves.
Next, the speed conditions of the application process, in other words, conditions such as the speed at which the moving table
321
moves (the rotating speed of the driving motor
343
) and the color of the phosphor to be applied (between which barrier ribs the phosphor will be applied) are set. This completes the various settings of the phosphor ink applying device.
2. Beginning Application of Phosphor Ink
After the various settings of the phosphor ink applying device are completed, the operator inputs an operation through the operator input unit to start the work, and the application of the phosphor ink starts automatically.
FIG. 4
will be used in the following explanation. The moving table
321
progresses at a fixed speed in an indicated by an arrow B, according to the driving motor
343
rotating at a fixed speed. Then, when the position on the back panel where phosphor ink is to be applied is directly below the nozzle of the phosphor ink discharge device
721
a
, the valve
753
of the phosphor in discharge device
721
a
is opened, and application of phosphor ink starts. As the position of the barrier ribs and auxiliary barrier ribs of the back panel are input beforehand, the timing at which the valve is opened can be determined by corresponding these positions to the position of the moving table
321
(the number of rotations of the driving motor
343
).
Application of phosphor ink by the phosphor ink discharge devices
721
b
and
721
c
begins in the same manner. Furthermore, the timing of the start of discharge of the phosphor ink discharge devices
721
a
,
721
b
, and
721
c
is staggered because of their differing positions along the y-axis.
3. Control of Phosphor Ink Discharge Quantity
If the set discharge quantity used when application of phosphor ink begins is maintained in the same way as described above, there is a possibility that phosphor ink applied on the tops of the auxiliary barrier ribs may flow over the barrier ribs into adjacent different colored cells, and cause mixing of colors. Consequently, the discharge quantity of phosphor ink is controlled.
FIG. 6
explains a method of controlling the phosphor ink discharge quantity over time when phosphor ink is applied as shown by the arrow A in FIG.
3
. FIG.
6
(
a
) shows the correspondence between application time (the distance the back panel moves) and the undulations made by the auxiliary barrier ribs
111
in the direction of arrow A in FIG.
3
. FIG.
6
(
b
) shows the relationship between the application time and the discharge quantity from the phosphor ink discharge device.
As shown by the figures, there is no auxiliary barrier rib in the area to which phosphor ink is being applied during the time t
0
to t
1
. In this section the valve
753
is fully open and a predetermined discharge quantity of phosphor ink Q
1
is consistently maintained and applied.
Next, during the time t
1
to t
2
, application of phosphor ink to a side wall of the auxiliary barrier rib begins. At this time, the discharge quantity of phosphor ink is gradually reduced to a quantity Q
2
.
During time t
2
to t
3
, phosphor ink is applied to the top portion of an auxiliary barrier rib. The discharge quantity is already reduced to Q
2
at t
2
, and Q
2
consistently maintained while application takes place. In this way, flow into the adjacent cells of phosphor ink which has been applied over the barrier ribs
109
is prevented. The discharge quantity Q
2
is set within a range that will not overflow, taking the height Hs of the barrier ribs
109
and the height Hh of the auxiliary barrier ribs
111
into consideration.
Next, phosphor ink is again applied to a side wall of the auxiliary barrier rib during time t
3
to time t
4
. Here, the discharge quantity is gradually increased from Q
2
to Q
1
. This means that at time t
4
the discharge quantity has returned to Q
1
, and phosphor ink can be applied consistently maintaining the discharge quantity Q
1
to the ensuing area in which there is no auxiliary rib.
This kind of operation is repeated for areas which have barrier ribs from t
5
onwards, and is finished when phosphor ink has been applied to a length equal to that of one barrier rib. When application finishes the valve
753
is closed, stopping discharge. By having the three phosphor ink discharge devices
721
a
,
721
b
, and
721
c
perform identical operations three lines of phosphor ink can be formed by scanning once.
Next, the moving table
321
is moved in the opposite direction to arrow B (see
FIG. 4
) so as to be in line with the rails
301
, and the driving motor
526
is driven and moves the support base
701
along the x-axis a distance that is nine times the pitch of each barrier rib
109
(that is, the pitch of neighboring same phosphor colors (three times the pitch of the barrier ribs) multiplied by the number of phosphor ink discharge devices (three)).
By repeating the above-described application of phosphor ink, the application of one color of phosphor ink is completed. Other colors are applied to the back panel in the same manner.
According to the above-described method, color mixing that occurs when applied phosphor ink flows over into adjacent cells can be prevented because the discharge quantity of phosphor ink to auxiliary barrier ribs is reduced. Furthermore, as described above, by providing a valve in each nozzle aperture of the phosphor ink discharge devices and a driving device to drive the valves, it is possible to control the phosphor ink discharge amount by controlling the driving device. Therefore, phosphor ink can be applied without mixing colors, even in a back panel which is intricately shaped such as that having auxiliary ribs, and a plurality of lines of phosphor ink can be applied simultaneously. As a result work efficiency is improved. Furthermore, as described above, the placements of the phosphor ink applying devices
721
a
,
721
b
, and
721
c
are staggered in the y-axis, but the discharge timing can be controlled for each nozzle, so a result, phosphor ink can be applied only where necessary.
Please note that in a PDP formed through such an application process, phosphor films are formed thinly of surfaces of the auxiliary barrier ribs (the tops and side walls), and thickly in other places (the areas between auxiliary barrier ribs in the grooves formed by the barrier ribs).
<Variations of the Present Embodiment>
The above-described phosphor ink applying device is described as having a group of three ink discharge devices. However, if there are as many ink discharge devices positioned in a line as there are lines of a color to be applied to a PDP, one color can be applied by scanning only once, further improving work efficiency.
FIG. 7
shows an outline of an arrangement of ink discharge devices when the phosphor ink applying device is seen along the a z-axis. For example, a plurality of ink discharge devices
7210
such as that described above may be arranged in groups of three in an x-axis, such as in FIG.
7
(
a
), or all ink discharge devices
7211
may be positioned in a row diagonal in relation to the y-axis, such as in FIG.
7
(
b
).
Furthermore, in the embodiment, an example of a back panel which has auxiliary barrier ribs was explained, but the phosphor ink applying device of the present invention can be applied to a back panel which does not have auxiliary barrier ribs, but rather has meandering barrier ribs, the distance between which varies relatively. In such a back panel, overflow may occur in narrow sections between barrier ribs if phosphor ink is applied at a constant discharge quantity, meaning that colors may mix. Such color mixing can be controlled if the present invention is used to reduce the discharge quantity when the distance between barrier ribs is short, and increase the discharge quantity when the distance between barrier ribs in long.
In the above described embodiment, valves are used as the means for changing the discharge quantity of phosphor ink. However, it is possible to provide a device such as a regulator which controls output pressure, for example partway along the line L
2
which is connected to each ink discharge device from the pressuring device
760
shown in
FIG. 5
, provide a driving device to drive the regulator, and have the driving device controlled by the control unit. The result is that by adjusting the output pressure, in other words the pressure applied to the ink discharge devices, the discharge quantity from each nozzle aperture is controlled for each ink discharge device. In addition, a heating and cooling device may be provided in the nozzle member instead of a valve. The temperature of the nozzle member varies according to the driving of the ink discharge device, meaning that the viscosity of phosphor ink passing through the nozzle aperture also changes, changing the discharge quantity.
(Second Embodiment)
Next, a second embodiment of the phosphor ink applying device to which the present invention is applied will be explained. Please note that the phosphor ink application device of the present embodiment has substantially the same structure as that shown in FIG.
4
and
FIG. 5
, except for the nozzle member
750
of the first embodiment shown in FIG.
5
. Therefore, the following will focus on the differences.
FIG. 8
is a partial perspective and sectional view of the structure of a nozzle member
750
of the phosphor ink applying device of the second embodiment.
As shown in the figure, the nozzle member
780
is composed of a lid member
781
, and a discharge member
782
, and these two members are aligned and hermetically sealed together. The lid member
781
is formed of plate-shaped stainless steel, and has an opening in the center which is an induction mouth
783
for inducing phosphor ink.
The discharge member
782
is composed of an ink space
784
cut out section in the middle, three nozzle apertures
785
a, b
, and
c
opened in the bottom of the ink space, valves
786
a, b, c
partway along the nozzle apertures for changing the ink quantity and driving motors
787
a, b, c
for driving the valves. Here, the ink space, the nozzle apertures, and the space for storing the valves
786
a, b, c
are subjected to a mirror surface processing according to electrolytic polishing so that friction resistance of phosphor ink that flows through is reduced to a minimum.
A distance W along the x-axis between the nozzle apertures
785
a
and
785
b
, and the nozzle apertures
785
b
and
785
c
is formed to maintain a distance which is three times the distance between barrier ribs on the back panel. By maintaining such a distance, a plurality of blue lines for example, can be applied.
The valves
786
a, b
, and
c
are driven independently by the driving motors
787
a, b
, and
c
respectively, and the driving motors are controlled in the same manner as those in the first embodiment by the controller. Accordingly, as with the first embodiment, a plurality of phosphor inks can be applied in line-shapes and mixing of colors can be avoided even in a back panel which is intricately shaped such as that formed by auxiliary barrier ribs. In addition, a plurality of nozzle apertures are provided in one phosphor ink discharge device, therefore a more compact structure can be provided as less tanks are required.
When a plurality of nozzles are provided in this way, however, it is possible for there to be deviations of approximately 5% between the discharge quantities of the nozzle apertures, due to the precision of the processing of the nozzle aperture. However, as valves and driving devices are provided in the second embodiment, it is possible to discover the degree to which the valves should be open by experiment beforehand so that the discharge flow of each nozzle aperture is even, and if the opening of the valves is controlled so as to correct the deviations, deviations in discharge flow can be prevented.
Please note that it is possible to use only one of this kind of phosphor ink discharge device, but by providing three as in the first embodiment, the number of phosphor ink lines that can be formed simultaneously is increased while color mixing is prevented, resulting in improved work efficiency.
Industrial Application
PDPs manufactured according the phosphor application device of the present invention are effective as display devices used in computers and televisions, and in particular display devices which demand high brightness.
Claims
- 1. A method for manufacturing a plasma display panel including a phosphor ink application process for applying phosphor ink to a substrate for a plasma display panel which has(a) a plurality of first barrier ribs provided so that grooves are formed therebetween, and (b) second barrier ribs which are provided between the grooves and which have a height lower than the first barrier ribs, the phosphor ink being applied along the first barrier ribs in each groove, the method comprising: varying the quantity of phosphor ink applied to the second barrier ribs so that the quantity of phosphor ink is less than the quantity of phosphor ink applied to the grooves on the substrate between the second barrier ribs.
- 2. The method of claim 1 further including applying a pressure to a source of phosphor ink wherein the pressure is varied to vary the quantity of phosphor ink applied.
- 3. The method of claim 1 further including a control valve for controlling the flow of the phosphor ink and varying an opening of the control valve to vary the quantity of phosphor ink applied.
- 4. The method of claim 1 wherein the second barrier ribs extend transversely between respective first barrier ribs and have a first inclined side wall, a flat top portion, and a second inclined side wall and the quantity of phosphor ink is applied at a first rate of flow along the grooves, at a second rate of flow along the respective inclined side walls and at a third rate of flow along the flat top portion.
- 5. The method of claim 4 wherein the second rate of flow varies from a maximum rate of flow equal to the first rate of flow to a minimum rate of flow equal to the third rate of flow.
- 6. A plasma display panel formed with a substrate which has(a) a plurality of first barrier ribs provided so grooves are formed therebetween, (b) second barrier ribs which are provided at a predetermined interval in the grooves and which have a height lower than the first barrier ribs, and (c) line-shaped phosphor film along the first barrier ribs in each groove successively formed by the method comprising: the phosphor film being applied more thinly to a top portion of the second barrier ribs than to the areas on the substrate therebetween.
Priority Claims (1)
Number |
Date |
Country |
Kind |
11-296314 |
Oct 1999 |
JP |
|
PCT Information
Filing Document |
Filing Date |
Country |
Kind |
PCT/JP00/07223 |
|
WO |
00 |
Publishing Document |
Publishing Date |
Country |
Kind |
WO01/29860 |
4/26/2001 |
WO |
A |
US Referenced Citations (8)
Number |
Name |
Date |
Kind |
4433571 |
Snow, Jr. |
Feb 1984 |
A |
5331565 |
Hattori et al. |
Jul 1994 |
A |
5620519 |
Affeldt et al. |
Apr 1997 |
A |
5921836 |
Nanto et al. |
Jul 1999 |
A |
5951350 |
Aoki et al. |
Sep 1999 |
A |
6124676 |
Salavin et al. |
Sep 2000 |
A |
6153253 |
Affeldt et al. |
Nov 2000 |
A |
6369501 |
Aoki et al. |
Apr 2002 |
B1 |
Foreign Referenced Citations (7)
Number |
Date |
Country |
63155527 |
Jun 1988 |
JP |
8257466 |
Oct 1996 |
JP |
10223138 |
Aug 1998 |
JP |
10228863 |
Aug 1998 |
JP |
11-213896 |
Aug 1999 |
JP |
11213896 |
Aug 1999 |
JP |
11239748 |
Sep 1999 |
JP |