JP2004174342A - Coating apparatus and coating method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for forming a uniform quantity and uniform concentration phosphor layer with high precision at a high speed in an apparatus and a method for forming a phosphor layer on a box type lib of a plasma display panel. <P>SOLUTION: The subject apparatus is composed of a moving part 5 for moving a dispenser 3 to an arrow X-X', a transporting part 6 for moving a substrate 4 to an arrow Y-Y', a moving part 7 for moving the dispenser 3 to an arrow Z-Z', a control box 8 for controlling the moving parts 5 and 7 and the transporting part 6, and an air pressure control part 9 for supplying a phosphor material. Phosphor paste is intermittently applied on the substrate 4 by the dispenser 3 after the clearance between the substrate 4 and a discharge port and the relative position are fixed. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a coating apparatus and a coating method for forming a phosphor layer of a plasma display panel (hereinafter, referred to as “PDP”).
[0002]
[Prior art]
As a method for forming a phosphor layer of a plasma display panel, there are a screen printing method, a dispenser method, an electrolytic jet method, an ink jet method, a photoresist method, and the like. Using these methods, R (red), G (green), and B (blue) phosphor layers are formed between the ribs on the back plate.
[0003]
In recent years, various rib shapes have been devised in order to cope with higher definition and higher luminance of a plasma display panel. Among them, a box-shaped rib as shown in FIG. 11 has attracted attention because of its advantages such as solving the crosstalk problem and improving the light emitting area.
[0004]
[Patent Document 1]
Japanese Patent No. 2679036 [Patent Document 2]
Japanese Patent Application Laid-Open No. 2002-021715 [Patent Document 3]
Japanese Patent Application Laid-Open No. 2001-015021
[Problems to be solved by the invention]
However, it is considered difficult to form a phosphor layer on a box-type rib accurately and at high speed by the above-described conventional method. The reason will be described below.
[0006]
For example, in the case of the screen printing method, the screen plate to be prepared due to the recent increase in screen size and definition has a considerably large size and a fine structure. Then, expansion and contraction of the screen plate and positioning errors are likely to occur, and it is inevitably difficult to apply with high accuracy.
[0007]
In addition, in the case of the ink jet system, it is possible to apply a very small amount with high precision, but the application amount per shot is small, which is disadvantageous in terms of production tact. In addition, in order to use the coating material as ink, the concentration of the phosphor, which is a solid content, must be reduced, and therefore, there is a problem that the brightness of the panel does not increase from a certain amount.
[0008]
In the case of the photoresist method, only the phosphor layer to be formed by embedding the photosensitive phosphor film between the ribs is exposed, and the unexposed portion is washed away, so that the phosphor layer can be formed with a high degree of accuracy. However, a series of operations of embedding, exposing, and cleaning phosphor films for each of three colors of R (red), G (green), and B (blue) is required, and the number of steps is increased, and the material cost is increased. Problems arise.
[0009]
Further, in the case of a dispenser method, it is possible to apply a small amount intermittently, but it is difficult to apply it at high speed with high accuracy. For example, in the case of a conventional air pulse type dispenser as shown in FIG. 11, there are problems such as variations in the discharge amount due to a difference in water head, variations in the discharge amount due to discharge pressure pulsation, and variations in the discharge amount due to a decrease in fluid viscosity. And cannot be applied accurately. In order to solve these problems, the effects of head difference, temperature change, etc. are programmed in advance in a computer and air pulses are controlled, but the control system is complicated, and the fundamental solution is is not.
[0010]
In the case of an air pulse type dispenser, a material is ejected from a nozzle in a state where the tip of the nozzle is close to a coating surface, and the material is transferred to a substrate to perform coating. Therefore, when applying to the box-shaped rib, if the tip of the nozzle is lower than the rib height, the material adheres to the tip of the nozzle after the application, which causes threading or sagging of the material, and cannot be applied accurately. Conversely, when applying with a height higher than the rib height, it is very difficult to adjust the amount of application so that extra material does not stick to the top of the rib.
[0011]
From these viewpoints, it has been difficult to apply a conventional air pulse type dispenser to the box type rib. That is, to apply the dispenser method to the box-type ribs at high speed, it can be said that a technique is required in which the material is ejected from the nozzle tip while the tip of the nozzle and the facing surface are sufficiently separated.
[0012]
If the dispenser disclosed in Patent Literature 1 is used to overcome the drawbacks of the conventional dispensers, it is considered that coating can be performed at high speed. However, in this dispenser, a method in which the paste material is intermittently applied to the box-shaped ribs from the start point to the end point with a uniform amount and concentration, and the distance between the discharge port and the substrate which is the opposing surface is maintained at a wide interval. However, it does not disclose a method of applying the material by flying it.
[0013]
SUMMARY OF THE INVENTION The present invention solves the above-mentioned conventional problems, and provides a coating apparatus and a coating method for applying a high-precision, uniform amount and a uniform concentration of a phosphor to a box-shaped rib of a plasma display panel by a dispenser method. It is.
[0014]
[Means for Solving the Problems]
In order to achieve the above object, a coating apparatus according to the first aspect of the present invention includes a first actuator that relatively moves a piston and a housing, and a space that accommodates at least a part of the piston and penetrates in an axial direction. A second actuator for moving the sleeve and the housing relative to each other, and a suction port and a discharge port for a fluid that communicates a pump chamber formed by the piston, the sleeve and the housing with the outside. T1> T2, where T1 is a time for moving the piston and the sleeve relatively in the opposite direction, T2 is a time for lowering the piston, and T3 is a time for raising the sleeve. T3> T2.
[0015]
At this time, it is preferable that the time relationship between T1, T2, and T3 is T1>T3> T2.
[0016]
In the coating apparatus according to the first aspect of the present invention, it is preferable that the fluid ejection time T2 is T2 <5 msec.
[0017]
In the coating apparatus according to the first aspect of the present invention, it is preferable that the distance δ from the glass substrate surface of the box-shaped rib to the discharge port is δ> 100 μm.
[0018]
In the coating apparatus according to the first aspect of the present invention, in the box-type rib, the vertical direction of one box is defined as a vertical rib and the horizontal direction is defined as a horizontal rib, and the shorter one of the vertical ribs is defined as L. When the discharge amount of one drop is V, the distance δ from the glass substrate surface of the box-shaped rib to the discharge port is preferably δ> 1.5 V / πL ² .
[0019]
In the coating apparatus according to the first aspect of the present invention, the displacement of the pump chamber is controlled by changing the relative displacement between the piston and the sleeve, and the fluid is intermittently ejected from the nozzles to thereby depend on the rib shape of the substrate. It is preferable to enable uncoated coating.
[0020]
In the coating apparatus according to the first aspect of the present invention, when coating the substrate, it is preferable to gradually change the relative displacement between the piston and the sleeve near the start point and the end point.
[0021]
Further, in the application device of the first invention of the present application, it is preferable that a minute vibration is applied to the displacement waveform including the displacement of the piston and the sleeve.
[0022]
Further, in the coating apparatus of the first invention of the present application, it is preferable to apply vibration by an ultrasonic oscillator to one section of the displacement waveform of the piston and the sleeve.
[0023]
Furthermore, in the coating apparatus of the first aspect of the present invention, when applying a fluid, it is preferable that the displacement of the coating apparatus in the Z-axis direction is zero.
[0024]
On the other hand, the coating method of the first invention of the present application relatively moves the sleeve and the housing having at least a part of the piston and having a space penetrating in the axial direction while relatively moving the piston and the housing. A coating method in which the fluid is discharged from a pump chamber formed by the piston, the sleeve, and the housing via a discharge port,
T1> T2 and T3> T2, where T1 is the time for moving the piston and the sleeve relatively in the opposite direction, T2 is the time for lowering the piston, and T3 is the time for raising the sleeve. And
[0025]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, the present embodiment will be described with reference to the drawings.
[0026]
FIG. 1 shows an outline of an example of a box-shaped rib substrate. As a method of forming such a rib shape, there are a thick film printing, a sand blast method and the like. For example, in the case of the sand blast method, a glass paste is applied to the glass substrate 1 by screen printing or the like, and then a photosensitive resist is applied thereon, exposed, and developed, and then a portion where the resist film is not formed is removed by sand blast. By doing so, the box-shaped rib 2 is formed. In the case of a 42-inch panel, for example, the width of the box-shaped rib is about 0.63 mm long and 0.26 mm wide.
[0027]
When applying the phosphor paste to such a box-shaped rib 2, an applicator shown in FIG. 2 is used. The main device configuration includes a moving unit 5 for moving the dispenser 3 in the direction of arrow XX ', a transporting unit 6 for moving the substrate 4 in the direction of arrow YY', and a moving unit for moving the dispenser 3 in the direction of arrow ZZ '. 7, a control box 8 for controlling the moving units 5 and 7 and the transporting unit 6, and an air pressure control unit 9 for supplying a phosphor material. Then, a clearance and a relative position between the substrate 4 and the discharge port are determined, and the phosphor paste is intermittently applied to the substrate 4 by the dispenser 3.
[0028]
The dispenser 3 shown in FIG. 2 includes a first actuator for relatively moving the piston and the housing, a sleeve for accommodating at least a part of the piston and having a space penetrating in the axial direction, And a fluid suction port and a discharge port for communicating a pump chamber formed by the piston, the sleeve, and the housing with the outside.
[0029]
The first and second actuators are composed of magnetostrictive elements such as giant magnetostrictive elements and piezoelectric elements, and can perform high-speed, minute displacement in the Z-axis direction. FIG. 3 shows a cross-sectional view of the tip of the dispenser.
[0030]
The flow of the paste material will be described with reference to FIG. 3. The phosphor paste is supplied to the nozzle tip from the material supply unit 10 through the space between the outer frame 11 and the sleeve 12. Then, the phosphor paste is intermittently discharged from the nozzle 14 by the interlocking operation of the sleeve 12 and the piston 13. An example of the operation of the sleeve 12 and the piston 13 is shown in FIG. 4, and a displacement waveform is shown in FIG.
[0031]
The ejection mechanism will be described with reference to FIGS.
[0032]
First, in the first section T1 in which the sleeve 12 and the piston 13 move in the upside-down direction, the sleeve 12 descends to form a pseudo-closed space or pump chamber 15 surrounded by the outer frame 11, the sleeve 12, and the piston 13. (Exchange process). Next, in the second section T2 in which the piston 13 descends, a certain amount of phosphor paste confined in the pseudo closed space is discharged from the pump chamber 15 through the discharge port 14 (discharge stroke). Further, in the third section T3, the phosphor 13 is supplied to the pump chamber 15 again by the rise of the sleeve 12 while the piston 13 is kept at a constant height (suction stroke). Then, the process shifts from the third section T3 to the first section T1, and by repeating this cycle, that is, the application cycle Tc, continuous discharge of the phosphor paste becomes possible.
[0033]
The first section T1 in the present coating apparatus is a material exchange step, the second section T2 is a material discharge step, and the third section T3 is a material suction step. The time required for each of the steps T1, T2, T3 is as follows.
[0034]
First, the suction stroke T3 requires a longer time than other strokes. The reason is that the pump chamber 15 is filled with the material due to the pressure difference, but if the filling time is short, the filling amount is insufficient and the pumping is performed. For this reason, a minimum filling time is required. The shorter the discharge stroke T2 is, the larger the peak pressure can be generated, and the more easily the fluid can fly. If an actuator such as a piezoelectric element is used, T2 <1 msec is possible. The exchange stroke T1 can be made sufficiently small because the fluid can be forced to flow into the pump chamber 15 by the lowering of the sleeve 12.
[0035]
From these facts, the time relationship between T1, T2 and T3 is T1> T2, T3> T2, and the more desirable relationship is T1>T3> T2. Further, in view of production tact, the discharge time T2 is desirably T2 <5 msec. Further, the use of a highly responsive element or power supply can shorten the application cycle Tc.
[0036]
Further, the intermittent coating is enabled by the coating apparatus of the present invention because a negative pressure and a positive pressure are generated alternately at the nozzle tip by the displacement waveform of the sleeve 12 and the piston 13 as shown in FIG. is there. FIG. 6 shows the pressure generated at the nozzle tip of the dispenser 3.
[0037]
First, a large negative pressure is generated in the third section T3 in which the sleeve 12 is raised, and the pressure gradually recovers in the first section T1 in which the sleeve 12 and the piston 13 operate in the opposite directions, and the second section in which the piston 13 is lowered. In the section T2, a large positive pressure is generated. As described above, since the negative pressure is generated only by the operation of the sleeve 12 and the piston 13, it is not necessary to lift the dispenser itself in the Z-axis direction immediately after the application in order to cause the liquid to run out unlike a conventional dispenser. Therefore, the displacement in the Z-axis direction becomes zero, so that the phosphor paste can be intermittently applied at a high speed.
[0038]
By selecting an appropriate nozzle diameter and nozzle length for the phosphor paste by the cycle of positive pressure and negative pressure occurring at the nozzle tip, the phosphor paste can fly from the nozzle 14. As a result, the dispenser 3 can fly the coating material like an ink jet, so that the coating can be performed not depending on the rib shape of the substrate surface as well as the box-shaped rib 2. Although the rib height of the box-shaped rib is usually 100 μm or more, the coating may be performed by increasing the distance δ between the discharge port (nozzle 14) of the present coating apparatus and the glass substrate surface by δ> 100 μm.
[0039]
In addition, when applying the material by flying it from the nozzle, if the droplet is considered to be a complete sphere, the diameter of the sphere that is put into the box-shaped rib at one time will be larger than the rib width. However, in practice, the droplets are considered to be applied in the form of a spheroid because of the weight of the droplets. Therefore, if the distance between the nozzle and the substrate is at least twice the major axis of the ellipsoid and the rib width is at least twice the minor axis of the ellipsoid, the paste will adhere to the top of the rib. It can be applied without.
[0040]
FIG. 7 shows this state. The volume per one drop V ^(mm 3), the rib width is L (mm), when the long axis of the spheroid a, the short axis to is b, the volume V is a V = 4πab ^2/3 . The height δ from the glass substrate to the nozzle needs δ> 2a, and if L = 2b, a relational expression of δ> 2a = 2 × (3V / 4πb ² ) = 1.5V / πL ² is derived. It is necessary to apply at least a distance between the nozzle 14 and the glass substrate so as to satisfy at least this relational expression.
[0041]
FIG. 8 shows the displacement waveform of the piston and the sleeve improved in order to improve the flying property of the paste material.
[0042]
In the second section T2 where the paste material is discharged, both the sleeve 12 and the piston 13 are lowered. Thereby, the discharge pressure can be increased from the displacement waveform of FIG. Then, immediately after the second section T2, the sleeve 12 and the piston 13 are simultaneously raised, so that a large negative pressure is generated in the pump chamber 15 according to the displacement waveform of FIG. As described above, by operating the sleeve 12 and the piston 13 simultaneously, a positive pressure and a negative pressure are generated in the pump chamber 15, so that even higher-viscosity materials can be intermittently ejected from the nozzles and discharged. It can be said that the coating apparatus in the present invention can freely change the ejection property by changing the displacement waveform, and thus can be applied to coating materials having a wide range of viscosity.
[0043]
On the other hand, by changing the displacement amount of the displacement waveform of the sleeve 12 and the piston 13 in this dispenser, it is possible to improve the uniformity of the application amount at the starting point where the conventional dispenser method and the electrolytic jet method are not good. .
[0044]
As a problem that occurs at the starting point of coating, there is a problem that the coating amount is smaller than that at the intermediate point. One of the causes is a problem of material properties. The phosphor paste often has a thixotropic property, and has a property that the viscosity decreases when a high shear force is applied. Therefore, when such a paste material is used, it is difficult for the applied amount to be constant from the start of discharge to the time when the paste enters a steady state. As a solution to this, in a conventional dispenser system or the like, an air pressure control unit is provided to stabilize the discharge amount. However, in this method, there are problems such as an increase in size of the apparatus, difficulty in multi-heading, and a complicated control system.
[0045]
As a method for solving this problem, in the present invention, the displacement is controlled by gradually changing the displacement of the sleeve 12 and the piston 13 of the dispenser 3. FIG. 9 shows the relationship between the displacement amounts.
[0046]
As shown in FIG. 9, immediately after the start of the application, the displacement of the piston 13 is increased to increase the amount of application per one shot, and after the steady state is reached, the displacement of the piston 13 is kept constant. That is, by temporarily increasing the coating amount per shot, the coating amount shortage due to the thixotropy is solved. This enables a constant amount of coating from the start point to the end point of the coating.
[0047]
Note that the discharge amount per shot can also be changed by keeping the displacement amount of the piston 13 constant and gradually changing the displacement amount of the sleeve 12, so that even with this method, the application amount non-uniformity at the starting point can be improved. Can be solved.
[0048]
As described above, by changing the displacement waveform and the displacement amount of the sleeve 12 and the piston 13, it is possible to apply it to panels of various sizes without depending on the rib shape. This can be said to be an excellent advantage because it is not necessary to prepare a screen plate for each size as in screen printing.
[0049]
Further, by changing the displacement waveform, it is possible not only to keep the application amount constant but also to apply a material of a constant concentration. For example, in order to prevent sedimentation of the particles contained in the phosphor paste, a waveform that gives a minute vibration in the first section T1 or the like is added to the displacement waveforms of the sleeve 12 and the piston 13 (FIGS. 5 and 8). This allows the paste material to have a high fluidity and prevent sedimentation, so that a uniform concentration can be applied.
[0050]
In addition, since a shear force is applied to the material by the minute vibration to temporarily lower the viscosity, an effect of improving the ejection property can be expected. It is considered that a method of applying a vibration that does not affect the ejection not only in T1 but also in the sections T2 and T3 is effective.
[0051]
In addition, in order to enhance the dischargeability of the material, not only a method of applying minute vibration to the displacement waveform of the sleeve 12 and the piston 13 but also a method of using an ultrasonic oscillator can be considered. For this, as shown in FIG. 10, the ultrasonic oscillator 16 is mounted in the material supply port of the dispenser or in the dispenser. An example using such an apparatus is disclosed in Patent Document 3, but in this case, it is considered to be an extremely natural apparatus for preventing the sedimentation of particles.
[0052]
The role of the ultrasonic oscillator 16 used in this device is not limited to this. That is, by synchronizing the movement of the sleeve 12 and the piston 13, the material supply can be made smooth, and the discharge performance can be improved. For example, in the third section T3 in which the piston 13 is lifted, vibration is applied by the ultrasonic oscillator 16 to apply a shear force to the material, thereby temporarily lowering the viscosity of the material. As a result, the material can be smoothly supplied to the pump chamber 15 in the third section T3 and the first section T1, and the piston 13 discharges the material immediately thereafter. As a matter of course, sedimentation of particles is also prevented, so that a material having a uniform concentration can be applied.
[0053]
On the other hand, the nozzle diameter must be smaller than the rib width in order to apply the phosphor paste intermittently to the box-shaped ribs with high accuracy. This causes a problem that nozzle clogging is likely to occur. However, by applying a small vibration to the displacement waveform of the sleeve 12 and the piston 13 or by applying a vibration by an ultrasonic oscillator, the fluidity of the paste can be increased, so that clogging at the nozzle does not occur. You can expect the effect of becoming.
[0054]
From this point of view, it is considered that applying minute vibration to the displacement waveform and applying vibration with the ultrasonic oscillator in synchronization with the displacement waveform are very useful means.
[0055]
This phosphor coating apparatus may be a single head, but a multi-head dispenser may be preferable in terms of production tact. Also in that case, a double piston structure including the sleeve 12 and the piston 13 can be used. That is, the nozzle portion may have multiple holes, or the sleeve and the piston may be downsized to a pencil size and a plurality of the sleeves and the piston may be arranged.
[0056]
In addition, it is considered that a mechanism having a recognition unit such as a CCD camera for recognizing ribs can be applied more accurately and uniformly between the ribs by applying a mechanism having a recognition unit such as a CCD camera for recognizing ribs.
[0057]
【The invention's effect】
ADVANTAGE OF THE INVENTION According to the coating device and coating method of this invention, the structure of a dispenser is made into the double piston structure called a sleeve and a piston, and by devising the displacement waveform of the sleeve and a piston, it is more accurate than screen printing or an inkjet method. It becomes possible to apply a uniform amount and uniform concentration of the paste material at a high speed.
[Brief description of the drawings]
FIG. 1 is a schematic diagram showing an example of a substrate of a box-type rib according to an embodiment of the present invention. FIG. 2 is a schematic diagram showing a configuration of a main coating apparatus according to an embodiment of the present invention. FIG. 4 is a cross-sectional view of a nozzle portion of the dispenser according to the embodiment. FIG. 4 is a view showing movement of a sleeve and a piston of the dispenser according to the embodiment of the present invention. FIG. 5 is a displacement waveform of the sleeve and piston of the dispenser according to the embodiment of the present invention. FIG. 6 is a diagram showing a pressure generated at a tip of a nozzle of a dispenser according to an embodiment of the present invention. 8 is a displacement waveform diagram of the sleeve and the piston of the dispenser according to the embodiment of the present invention. FIG. 9 is a diagram showing an example of gradually changing the displacement amount of the sleeve and the piston according to the embodiment of the present invention. Real Shows Figure 11 Conventional air-pulse dispenser illustrating the mounting of the ultrasonic oscillator according to Embodiment [Description of symbols]
1, 4 Glass substrate 2 Box type rib 3 Dispenser 5, 7 Moving unit 6 Transport unit 8 Control box 9 Air pressure supply unit 10 Material supply unit 11 Outer frame 12 Sleeve 13 Piston 14 Nozzle 15 Pump room 16 Ultrasonic oscillator

Claims (11)

A first actuator that relatively moves the piston and the housing, a sleeve that houses at least a part of the piston and has a space that penetrates in the axial direction, and a second actuator that relatively moves the sleeve and the housing And a coating device including a suction port and a discharge port of a fluid that communicates a pump chamber formed by the piston, the sleeve, and the housing with the outside,
T1> T2 and T3> T2, where T1 is the time for moving the piston and the sleeve relatively in the opposite direction, T2 is the time for lowering the piston, and T3 is the time for raising the sleeve. Coating device. 2. The coating apparatus according to claim 1, wherein the time relationship between T1, T2, and T3 is T1> T3> T2. 2. The coating apparatus according to claim 1, wherein the fluid ejection time T2 satisfies T2 <5 msec. 2. The coating apparatus according to claim 1, wherein a distance δ from the glass substrate surface of the box-shaped rib to the discharge port is δ> 100 μm. In the box type rib, when the vertical direction of one box is defined as a vertical rib and the horizontal direction is defined as a horizontal rib, and the shorter one of the vertical ribs is defined as L and the discharge amount of one drop is defined as V, , the distance from the glass substrate surface of the box-type rib to the discharge port [delta] is, [delta]> coating apparatus of claim 1, wherein it is 1.5V / πL ^2. The displacement of the pump chamber is controlled by changing the relative displacement of the piston and the sleeve, and the fluid is intermittently discharged from the nozzle to enable application independent of the rib shape of the substrate. Item 6. The coating device according to Item 1. 2. The coating apparatus according to claim 1, wherein, when coating the substrate, the relative displacement between the piston and the sleeve is gradually changed near the start point and the end point. 2. The coating apparatus according to claim 1, wherein a minute vibration is applied to the displacement waveform including the displacement of the piston and the sleeve. 2. The coating apparatus according to claim 1, wherein a vibration by an ultrasonic oscillator is applied to one section of the displacement waveform of the piston and the sleeve. 2. The coating apparatus according to claim 1, wherein when applying the fluid, the displacement of the coating apparatus in the Z-axis direction is zero. By relatively moving the housing and the sleeve having at least a part of the piston and having a space penetrating in the axial direction while relatively moving the piston and the housing, fluid is transferred to the piston, the sleeve and the sleeve. A coating method that is discharged from a pump chamber formed by a housing through a discharge port,
T1> T2 and T3> T2, where T1 is the time for moving the piston and the sleeve relatively in the opposite direction, T2 is the time for lowering the piston, and T3 is the time for raising the sleeve. Coating method.

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