Fluid applying apparatus Number:7,520,967 from the United States Patent and Trademark Office (PTO) owispatent A meniscus of applying fluid is controlled by applying a voltage to a discharge-nozzle side electrode and a counter electrode placed downstream of the discharge nozzle and by increasing or decreasing fluid pressure inside a pump chamber with use of a mechanism for rotational motion or rectilinear motion.<H apparatus, applying, Fluid, applying, , 7520967.html, Patent, pto, 7520967

Title: Fluid applying apparatus

Abstract: A meniscus of applying fluid is controlled by applying a voltage to a discharge-nozzle side electrode and a counter electrode placed downstream of the discharge nozzle and by increasing or decreasing fluid pressure inside a pump chamber with use of a mechanism for rotational motion or rectilinear motion.

Patent Number: 7,520,967 Issued on 04/21/2009 to Maruyama, et al.

Inventors: Maruyama; Teruo (Hirakata, JP), Sonoda; Takashi (Ritto, JP), Takii; Yoshimasa (Takatsuki, JP)
Assignee: Panasonic Corporation (Osaka, JP)

Appl. No.: 10/847,441

Filed: May 18, 2004

Foreign Application Priority Data


May 19, 2003 [JP]			2003-140302

Current U.S. Class: 204/212 ; 204/280; 222/322; 222/411

Current International Class: B05C 5/00 (20060101)

References Cited [Referenced By]

U.S. Patent Documents


4106032	August 1978	Miura et al.
4514742	April 1985	Suga et al.
4621268	November 1986	Keeling et al.
6770320	August 2004	Yamauchi et al.
6820973	November 2004	Ujita
6860976	March 2005	Andrews et al.
7059538	June 2006	Maruyama et al.

Foreign Patent Documents


54-134970	Oct., 1979	JP
57-021223	Aug., 1983	JP
58-139390	Aug., 1983	JP
10-027543	Jan., 1998	JP
2000-246887	Sep., 2000	JP
2001-137760	May., 2001	JP

Primary Examiner: Patel; Ashok
Attorney, Agent or Firm: Wenderoth, Lind & Ponack, L.L.P.

Claims

What is claimed is:

1. A fluid applying apparatus comprising: a housing having a suction port for sucking an applying fluid and a discharge nozzle at an end of the housing, the discharge nozzle defining a discharge port for discharging the applying fluid; a moving member which forms a pump chamber for the applying fluid in combination with the housing, the moving member being rotationally or rectilinearly movable relative to the housing; a moving-member driving device for driving the moving member to make the housing perform the rotational motion or rectilinear motion so that applying-fluid pressure inside the pump chamber is increased or reduced; a housing-side electrode provided at an outer peripheral portion of the discharge nozzle at the end of the housing; and a power supply for applying a voltage to the housing-side electrode.

2. The fluid applying apparatus according to claim 1, further comprising a counter electrode placed on a substrate or in proximity to the substrate, wherein the voltage can be applied from the power supply to between the housing-side electrode and the counter to thereby generate an electric field.

3. The fluid applying apparatus according to claim 2, wherein the counter electrode is placed between the housing-side electrode and the substrate.

4. The fluid applying apparatus according to claim 3, wherein the counter electrode is hollow and axisymmetric.

5. The fluid applying apparatus according to claim 2, further comprising: a cylindrical portion for storing therein the applying fluid having flowed out from the discharge port, which defines a discharge passage having a mean passage inner diameter larger than a passage inner diameter of the discharge port; and a lower housing which covers the cylindrical portion with a gap, thereby defining a flow passage which communicates with the discharge passage and which is used for a supply fluid other than the applying fluid, wherein the counter electrode is placed in proximity to the discharge passage.

6. The fluid applying apparatus according to claim 5, wherein the supply fluid is a gas.

7. The fluid applying apparatus according to claim 1, wherein a thread groove is provided on a relative movement surface of the moving member and the housing, and the applying fluid is sucked through the suction port into the thread groove and fed into the pump chamber by the rotational motion of the moving member.

8. The fluid applying apparatus according to claim 7, wherein the moving member and the housing constitute a thread groove pump.

9. The fluid applying apparatus according to claim 1, wherein the moving member is a piston, and the piston is inserted in the housing, and the moving-member driving device is a piston-axis-direction driving device for driving the piston into the rectilinear motion within the housing so as to increase or decrease the pump chamber defined between the piston and the housing, and thereby the fluid pressure inside the pump chamber is increased or decreased.

10. The fluid applying apparatus according to claim 1, wherein either one of the moving member or the housing is made of a nonconductive material.

11. The fluid applying apparatus according to claim 1, wherein the moving member is a piston, and the piston is inserted in the housing, and the moving-member driving device is an electro-magnetostriction device for putting the piston into rectilinear motion in its axial direction.

Description

BACKGROUND OF THE INVENTION

The present invention relates to very small-flow-range fluid applying apparatus and fluid applying method required in such fields as information/precision equipment, machine tools, and FA (Factory Automation); or in various production processes of semiconductors, liquid crystals, displays, surface mounting, and the like, and also relates to a plasma display panel formed by the fluid applying method and a pattern formation method therefor.

Issues related to conventional printing techniques are explained below by taking as an example a technique for forming the fluorescent substance layer of plasma display panels (hereinafter, referred to as PDPs).

A PDP that performs color display has, on its front-face plate/rear-face plate, a fluorescent substance layer composed of fluorescent substance materials that emit light in RGB (red, green, blue) colors, respectively. This fluorescent substance layer is so structured that three stripes which are filled with fluorescent substance materials of RGB colors, respectively, are formed between partition walls formed in parallel lines on a front-face plate/back-face plate (i.e., on an address electrode), and arrayed in a multiplicity with the three sets of the stripes parallelized in adjacency. This fluorescent substance layer is formed by a screen printing method, or photolithography method or the like.

With the conventional screen printing method, a large-scale screen makes it hard to achieve high-precision alignment of the screen printing plate, and in filling the fluorescent substance materials, the materials might be placed even on the top portions of the partition walls. As a result, it has been necessary to take measures such as introduction of a polishing process for removing the placed materials. Further, since the amount of filled fluorescent substance material varies depending on the difference in squeegee pressure, pressure control therefor is extremely subtle work, which largely depends on the degree of the skill of the operator. Thus, it is quite hard to obtain a constant filling amount over the entire front-face plate/back-face plate.

It is also possible to form the fluorescent substance layer by the photolithography method with the use of photosensitive fluorescent substance materials. However, this necessitates exposure and development steps, involving a number of steps larger than that of the screen printing method, giving rise to an issue of increased manufacturing cost.

Now, "direct patterning method" has recently been receiving attention in various fields in view of simplification, cost reduction, environmental load reduction, resources saving, energy saving, and the like of manufacturing processes. For example, there have been proposed engineering techniques taking advantages of individual methods including:

{circle around (1)} Dispenser method,

{circle around (2)} Ink jet method,

{circle around (3)} Electric-field jet method, etc.

A direct patterning method using a dispenser has already been proposed to solve the above-described issues in order to form the screen stripes in manufacturing processes of PDPs, CRTs, and the like in Japanese examined patent publication No. S57-21223 and Japanese unexamined patent publication No. H10-27543. According to this proposal, only setting numerical values of substrate specifications allows fluorescent substance to be discharged from a nozzle moving on the substrate and to be applied into grooves between ribs without the use of any conventional screen mask, so that the fluorescent substance layer can be formed with high precision for substrates of arbitrary sizes, while changes in substrate specifications can readily be managed. In the case of dispensers, the line width of drawing lines is restricted by the size of the inner diameter of the discharge nozzle. Since reducing the nozzle diameter to thin the line width would cause the clogging to more frequently occur, the line width would be limited to at most 70 to 100 .mu.m.

Meanwhile, it has been under development that the ink jet method developed for consumer printers is applied to applying apparatuses for industrial equipment. However, this method is, at the present stage, capable of treating only low-viscosity fluids of about 10 mPas and incapable of managing high-viscosity fluids from the driving method and structural constraints. Further, the powder diameter that can be prevented from clogging of the flow passage is limited to about 0.1 .mu.m, posing large constraints in terms of material. In addition, the fluid to be used as the applying material is, in many cases, a high-viscosity powder and granular material containing fine powder with its outer diameter ranging from 0.1 micron to tens of microns, such as electrode material, fluorescent substance material, solder, and electrically conductive capsules. With a view to draw fine electrode lines by using the ink jet method, there has been developed a nanopaste in which Ag particles having a mean particle size of about 5 nm are independently dispersed with the Ag particles covered with a dispersant.

However, also in this case, because the ink jet method is only capable of treating a low-viscosity nanopaste, the drawing lines would result in smaller thicknesses, causing the wiring resistance to become high. As a result, overstrikes would be required to ensure the thickness, posing an issue in terms of production cycle time.

In order to solve the above-described issues related to the dispenser method and the ink jet method, there have been proposed applying apparatuses for high-viscosity fluids called electric-field jet method (see Japanese unexamined patent publications No. 2000-246887 and No. 2001-137760). This method is based on the discharge method using electric field reported by Zeleny in 1917.

Referring to a principle view of FIG. 31, reference numeral 500 denotes a high-viscosity fluid, 501 denotes a control section, 502 denotes a container, 503 denotes an opening, 504 denotes an electrode, 505 denotes a power supply, 506 denotes an application-object base material (a substrate which is an object of application), 507 denotes an elongated portion of the applying fluid having flowed out from a nozzle, and 508 denotes a pressurization device. This applying apparatus has the opening 503 such as a circular or polygonal orifice or nozzle with a hole diameter of about 50 .mu.m to 1 mm .phi., at a lower portion of the container 502, and the electrode 504 is placed at a portion of this opening 503. Within the container 502 is filled the high-viscosity fluid 500 with a high-viscosity substance of 1,000 to 1,000,000 cps as a liquid applying material. In order to pressurize the high-viscosity fluid 500 filled in the container 502, the pressurization device 508 by high-pressure air is provided so as to be connected to the container 502. First, pressure is applied to the high-viscosity fluid 500 within the container 502, by which a meniscus of the high-viscosity fluid 500 is formed at the opening 503. Next, a first specified pulse voltage is applied to between the electrode 504 of the nozzle opening 503 and the application-object base material 506 that is the counter electrode so that the meniscus of the high-viscosity fluid 500 is elongated longitudinally at the opening 503, thereby forming the elongated portion 507, in which state the high-viscosity fluid 500 is let to drop from the tip end of this elongated portion. In this state, moving the nozzle and the application-object base material 506 relative to each other allows ultrafine lines of 10 .mu.m or less to be drawn because the tip end of the meniscus has become sufficiently thinner than the nozzle diameter.

Further, applying a second specified pulse voltage to between the opening 503 and the application-object base material 506 allows the elongated portion 507 to be partly separated from its tip end, by which the application of the high-viscosity fluid 500 can be interrupted. By this electric-field jet method, it becomes possible to draw ultrafine lines equivalent to those of the ink jet method by using high-viscosity fluids that could not be treated by the ink jet method.

However, this electric-field jet method has had the following issues. With the electric-field jet method, since a small rate of flow is transported from the container 502 to the nozzle tip end by the capillary phenomenon, the discharge of fluid can be achieved only by the electric field without using the pressurization device 508. Nevertheless, in the case where application lines of a fluorescent substance or electrode material are continuously applied onto a substrate (e.g., front-face plate or back-face plate of a PDP) placed, for example, on a stage (see, e.g., a mount plate 50 and an X-Y stage 50x in FIG. 26) that runs at high speed, it is necessary to apply both electric field and air pressure to ensure the flow rate. In this case, this method has two types of characteristics, those of the air type dispenser and those of the electric-field jet method, in combination at the same time. That is, the method bears the following shortcomings of the air type dispenser:

{circle around (1)} Poor stability of application flow rate; and

{circle around (2)} Incapability of forming starting and terminating ends of continuous lines at high grade.

The above {circle around (1)} is due to a reason that the discharge flow rate of the air type dispenser is inversely proportional to the viscosity of the applying fluid. Also, the viscosity of the fluid depends largely on temperature. For example, in the case of a standard calibration liquid, the viscosity changes to 50% due to a 5.degree. C. change of the fluid temperature. In the case of the air type dispenser, as great care is necessary to maintain the liquid temperature constant in order to reduce flow rate drifts, so similar care is necessary also for the electric-field jet method that uses air as an auxiliary pressure source.

The above {circle around (2)} is due to poor responsivity of the air type dispenser. This shortcoming can be attributed to the compressibility of air encapsulated in a cylinder and the nozzle resistance resulting when the air is let to pass through a narrow gap. That is, with the air method, because of a large time constant of the hydraulic circuit that depends on the cylinder capacity and the nozzle resistance, a time lag of 0.07 to 0.1 second has to be allowed for a time period which, after application of an input pulse, lasts from when the fluid starts to be discharged until when the fluid is transferred onto the substrate, or until when the fluid is interrupted during continuous application.

In the case of the electric-field jet method, as described before, the discharge can be interrupted only by electric field without the use of the pressurization device 508 using air pressure. However, with the use of the pressurization device 508 using air pressure for obtainment of larger application flow rates, starting and terminating ends of the continuous application line cannot be drawn at high grade because of the poor response of the air type. For example, at a starting end of a drawing line, even if an air pressure is applied simultaneously with application of a voltage at a start of application, the air pressure cannot be immediately increased to a specified pressure. As a result, there occurs `thinning` or `cut` at the starting point of the drawing line. Otherwise, at the terminating end of a drawing line, even if the air pressure is lowered simultaneously with turn-off of the voltage at a start of application, the air pressure cannot be immediately dropped to a specified pressure. As a result, there occurs `thickening` or `gathering` at the terminating end of the drawing line.

An object of the present invention is to provide fluid-applying apparatus and fluid-applying method as well as a plasma display panel and a pattern forming method therefor all of which are good at stability of application flow rate and capable of forming starting and terminating ends of application lines at high grade.

SUMMARY OF THE INVENTION

In order to accomplish the above object, the present invention has the following constitutions.

According to a first aspect of the present invention, there is provided a fluid applying apparatus comprising:

a housing having a suction port for sucking an applying fluid and a discharge port for discharging the applying fluid;

a moving member which forms a pump chamber for the applying fluid in combination with the housing and which is enabled to make rotational motion or rectilinear motion relative to the housing;

a moving-member driving device for driving the moving member to make the housing perform the rotational motion or the rectilinear motion so that applying-fluid pressure inside the pump chamber is increased or reduced;

a housing-side electrode placed in proximity to at least the discharge port of the housing; and

a power supply for applying a voltage to the housing-side electrode to form an electric field between the housing-side electrode and a substrate,

wherein the applying fluid is sucked through the suction port into the pump chamber, and discharged and applied through the discharge port onto the substrate which is an application object placed on an opposing surface of the discharge port by the rotational motion or the rectilinear motion of the moving member by the moving-member driving device, while a suction force for the applying fluid at the discharge port with a negative pressure generated by pressure-reducing the pump chamber by the rotational motion or the rectilinear motion, and a force of making the applying fluid projected at the discharge port by an electric field formed by applying the voltage to the housing-side electrode are controlled, whereby the application is stopped when the force of making the applying fluid projected for applying the applying fluid becomes smaller than the suction force for the applying fluid.

According to a second aspect of the present invention, there is provided the fluid applying apparatus according to the first aspect, further comprising a counter electrode placed on a substrate or in proximity to the substrate,

wherein the voltage is applied from the power supply to between the housing-side electrode and the counter electrode, whereby an electric field can be formed.

According to a third aspect of the present invention, there is provided the fluid applying apparatus according to the first aspect, wherein a thread groove is provided on a relative movement surface of the moving member and the housing, and the applying fluid is sucked through the suction port into the thread groove and fed into the pump chamber by the rotational motion of the moving member.

According to a fourth aspect of the present invention, there is provided the fluid applying apparatus according to the first aspect, wherein

the moving member is a piston, and the housing is capable of housing the piston, and

the moving-member driving device is a piston-axis-direction driving device for driving the piston into the rectilinear motion within the housing, thereby increasing and decreasing the pump chamber defined between the piston and the housing, whereby the fluid pressure inside the pump chamber is increased or decreased.

According to a fifth aspect of the present invention, there is provided the fluid applying apparatus according to the first aspect, wherein either one of the moving member or the housing is made of a nonconductive material.

According to a sixth aspect of the present invention, there is provided the fluid applying apparatus according to the first aspect, wherein

the moving member is a piston, and the housing is capable of housing the piston, and

the moving-member driving device is an electro-magnetostriction device for putting the piston into rectilinear motion in its axial direction.

According to a seventh aspect of the present invention, there is provided the fluid applying apparatus according to the second aspect, wherein the counter electrode is placed between the housing-side electrode and the substrate.

According to an eighth aspect of the present invention, there is provided the fluid applying apparatus according to the seventh aspect, wherein the counter electrode is hollow and axisymmetric.

According to a ninth aspect of the present invention, there is provided the fluid applying apparatus according to the second aspect, further comprising:

a cylindrical portion for storing therein the applying fluid having flowed out from the discharge port, which defines a discharge passage having a mean passage inner diameter larger than a passage inner diameter of the discharge port; and

a lower housing which covers the cylindrical portion with a gap, thereby defining a flow passage which communicates with the discharge passage and which is used for a supply fluid other than the applying fluid,

wherein the counter electrode is placed in proximity to the discharge passage.

According to a 10th aspect of the present invention, there is provided the fluid applying apparatus according to the ninth aspect, wherein the supply fluid is a gas.

According to a 11th aspect of the present invention, there is provided the fluid applying apparatus according to the third aspect, the moving member and the housing constitute a thread groove pump.

According to an 12th aspect of the present invention, there is provided a fluid applying method comprising:

driving a moving member which is capable of making rotational motion or rectilinear motion relative to a housing to put the moving member into rotational motion or rectilinear motion relative to the housing, and thus, increasing or decreasing an applying-fluid pressure inside an applying-fluid pump chamber defined between the housing and the moving member, whereby the applying fluid is sucked through a suction port of the housing into the pump chamber, and discharged and applied through a discharge port of the housing onto a substrate which is an application object placed on an opposing surface of the discharge port;

applying a voltage to a housing-side electrode placed in proximity to at least the discharge port of the housing to form an electric field between the housing-side electrode and the substrate; and

controlling a suction force for the applying fluid at the discharge port with a negative pressure generated by pressure-reducing the pump chamber by the rotational motion or rectilinear motion, and a force of making the applying fluid projected at the discharge port by an electric field formed by applying a voltage to the housing-side electrode, whereby the application is stopped when the force of making the applying fluid projected for applying the applying fluid becomes smaller than the suction force for the applying fluid.

According to a 13th aspect of the present invention, there is provided the fluid applying method according to the 12th aspect, wherein a voltage of the housing-side electrode is controlled by applying the voltage to the housing-side electrode, while discharge of the applying fluid is started or interrupted by increasing or decreasing the flow passage inside the pump chamber.

According to a 14th aspect of the present invention, there is provided the fluid applying method according to the 12th aspect, wherein the pump chamber is defined by two surfaces for moving relative to each other along a gap direction, and an internal pressure of the pump chamber is increased by contracting the pump chamber while the internal pressure is decreased by expanding the pump chamber.

According to a 15th aspect of the present invention, there is provided the fluid applying method according to the 14th aspect, wherein after the voltage is dropped, the pressure of the pump chamber is reduced by enlarging the pump chamber, whereby an application line is interrupted.

According to a 16th aspect of the present invention, there is provided the fluid applying method according to the 12th aspect, wherein meniscus is maintained generally identical in shape during intervals of application rest by giving both an action of making a meniscus of the applying fluid projected from the discharge port, and an action of reducing the fluid pressure of the pump chamber to suck the applying fluid through the discharge port into the pump chamber.

According to a 17th aspect of the present invention, there is provided the fluid applying method according to the 12th aspect, wherein the applying fluid is applied onto the substrate by giving both an action of making the meniscus of the applying fluid projected from the discharge port, and an action of reducing the fluid pressure of the pump chamber to suck the applying fluid through the discharge port into the pump chamber and by making the meniscus approach a substrate side, and thereafter, the application is interrupted by making the meniscus separated from the substrate side.

According to an 18th aspect of the present invention, there is provided the fluid applying method according to the 12th aspect, wherein after the applying fluid is flown from a discharge nozzle, a voltage is applied to between the housing-side electrode and a space electrode placed downstream of the discharge nozzle, whereby the fluid is applied onto the substrate.

According to a 19th aspect of the present invention, there is provided the fluid applying method according to the 16th aspect, wherein reduction in the fluid pressure inside the pump chamber is performed by a thrust dynamic seal formed by a discharge-side end face of the moving member and its opposing surface.

According to a 20th aspect of the present invention, there is provided a pattern formation method for plasma display panels, comprising:

driving a moving member capable of making rotational motion or rectilinear motion relative to a housing to put the moving member into rotational motion or rectilinear motion relative to the housing, and thus, increasing or decreasing a paste pressure in a pump chamber of a paste as an applying fluid defined between the housing and the moving member, whereby the paste is sucked through a suction port of the housing into the pump chamber, and discharged through the discharge port of the housing onto a PDP substrate, which is an application object, placed at an opposing surface of the discharge port, thereby applying and forming an application line, so that a paste layer is formed into a pattern;

performing the formation of this paste layer while applying a voltage to a housing-side electrode placed in proximity to at least the discharge port of the housing to form an electric field between the housing-side electrode and a PDP substrate, within an effective display area of the PDP substrate and/or within terminal portions neighboring the effective display area;

thereafter, controlling a suction force for the paste at the discharge port with a negative pressure generated by pressure-reducing the pump chamber by the rotational motion or rectilinear motion, and a force of making the paste projected at the discharge port by an electric field formed by applying a voltage to the housing-side electrode, whereby the application is stopped when the force of making the paste projected for applying the paste becomes smaller than the suction force for the paste.

According to a 21st aspect of the present invention, there is provided the pattern formation method for plasma display panels according to the 20th aspect, wherein after the voltage is dropped, the pressure of the pump chamber is reduced, whereby the application line is interrupted.

According to a 22nd aspect of the present invention, there is provided the pattern formation method for plasma display panels according to the 21st aspect, wherein given a time t=t.sub.ve at which the voltage drop is started, and a time t=t.sub.pe at which the pressure of the pump chamber is started to be reduced, it holds that 0<t.sub.pe-t.sub.ve<3 msec.

According to a 23rd aspect of the present invention, there is provided the pattern formation method for plasma display panels according to the 20th aspect, wherein a supply source for supplying the paste to the pump chamber is a pump which is driven by a motor, and rotation of the motor is stopped before the pressure of the pump chamber is reduced.

According to a 24th aspect of the present invention, there is provided the pattern formation method for plasma display panels according to the 20th aspect, wherein in the formation of the paste layer, terminal-portion electrode lines inclined with respect to a main electrode line are formed so as to cross the main electrode line in the terminal portion neighboring the effective display area of the PDP substrate.

According to a 25th aspect of the present invention, there is provided the pattern formation method for plasma display panels according to the 24th aspect, wherein by a dispenser having a plurality of nozzles each having the discharge port and disposed at an equal pitch, terminal-portion electrode lines having an identical inclination angle are selected from among the plurality of terminal portions and the selected terminal-portion electrode lines are simultaneously formed by application.

According to a 26th aspect of the present invention, there is provided a plasma display panel having main electrode lines formed in a plural number and parallel to one another in an effective display area of a PDP front-face plate, and terminal-portion electrode lines formed so as to be connected to the main electrode lines and inclined with respect to the main electrode lines in terminal portions neighboring this effective display area, wherein given a pitch P between the main electrode lines and a distance .DELTA.P of a portion of a terminal end of the terminal-portion electrode line projecting from the main electrode line, it holds that (.DELTA.P/P)<(1/3).

According to a 27th aspect of the present invention, there is provided a plasma display panel having main electrode lines formed in a plural number and parallel to one another in an effective display area of a PDP front-face plate, and terminal-portion electrode lines formed so as to be connected to the main electrode lines and inclined with respect to the main electrode lines in terminal portions neighboring this effective display area, wherein given a pitch P between the terminal-portion electrode lines and a distance .DELTA.P of a portion of a terminal end of the main electrode line projecting from the terminal-portion electrode line, it holds that (.DELTA.P/P)<(1/3).

BRIEF DESCRIPTION OF THE DRAWINGS

These and other aspects and features of the present invention will become clear from the following description taken in conjunction with the preferred embodiments thereof with reference to the accompanying drawings, in which:

FIG. 1 is a partial cross-sectional schematic view for explaining a fluid applying apparatus according to a first embodiment of the present invention;

FIG. 2 is a partial cross-sectional schematic view for explaining a fluid applying apparatus according to a second embodiment of the present invention, where part (A) shows a state of continuous application, (B) shows a state of application halt, and (C) shows a state of application interruption;

FIGS. 3A and 3B are partial cross-sectional views for explaining the fluid applying apparatus according to the second embodiment of the present invention and a partly enlarged view of the part (B) of FIG. 2, respectively;

FIG. 4A is a partial cross-sectional schematic view for explaining a fluid applying apparatus according to a third embodiment of the present invention, and FIG. 4B is a bottom view showing a thrust dynamic seal of the fluid applying apparatus according to the third embodiment;

FIGS. 5A and 5B are partial cross-sectional schematic views showing fluid applying apparatuses according to a fourth embodiment of the present invention and a modification thereof, respectively;

FIGS. 6A and 6B are views showing fluid menisci in a case where an electric field is not applied and another where an electric field is applied in the fluid applying apparatus according to the fourth embodiment, respectively;

FIG. 7 is a front sectional view showing a more specific structure of a discharge nozzle of the fluid applying apparatus according to the fourth embodiment;

FIG. 8 is a partial cross-sectional schematic view showing a fluid applying apparatus according to a fifth embodiment of the present invention;

FIG. 9 is a front sectional view showing a specific structure of the discharge nozzle of the fluid applying apparatus according to the fifth embodiment;

FIG. 10 is a front sectional view showing a dispenser having a structure of a two-degrees-of-freedom actuator as a modification of the second embodiment of the present invention;

FIGS. 11A and 11B are a top view and a front sectional view, respectively, showing a dispenser having a thread groove-and-piston separate structure as the fluid applying apparatus according to the second embodiment of the present invention;

FIG. 12 is a control block diagram in a case where release-and-interruption control over application lines is exerted by using a separate type dispenser with electric field control;

FIG. 13 is a structural view of a dispenser in a case where a separate type dispenser is used to provide electrical insulation between an electrode and each member;

FIG. 14 is a partial cross-sectional schematic view for explaining the principle of control of meniscus shape and position;

FIG. 15 is a chart showing a voltage waveform with time elapse;

FIG. 16 is a view showing an example of the PDP front-face plate;

FIG. 17 is a view showing an imaginary area for paste application on the PDP front-face plate;

FIG. 18 is a view showing a formation method of main electrode lines;

FIG. 19 is a view showing a formation method of electrode lines of a terminal portion;

FIG. 20 is a view showing time charts, where part (A) shows motor rotational speed versus time, (B) shows applied voltage for forming an electric field between nozzle and substrate versus time, and (C) shows piston displacement versus time;

FIG. 21 is a view showing state changes of a meniscus of the applying fluid at the nozzle tip end;

FIG. 22 is a view showing a state that a terminal-portion electrode line and main electrode lines cross each other;

FIG. 23 is a view showing a state that a terminal-portion electrode line and main electrode lines cross each other;

FIG. 24 is a view showing a state that terminal-portion electrode lines and a main electrode lines cross each other;

FIG. 25 is a view showing an effective display area and a non-effective display area for paste application on the PDP back-face plate;

FIG. 26 is a schematic perspective view in a case where the fluid applying apparatus according to the foregoing embodiment of the present invention is applied to a fluorescent substance-layer formation apparatus for PDP substrates;

FIG. 27 is a view showing a cross-sectional shape of an application line in a conventional printing technique;

FIG. 28 is a view showing a cross-sectional shape of an application line applied with a technique using a dispenser according to the foregoing embodiment of the present invention, i.e., in a fluid applying method using a dispenser;

FIG. 29 is an enlarged sectional view in a case where a throttle is formed on a flow passage in the vicinity of the piston portion in the fluid applying apparatus according to the second embodiment of the present invention of FIGS. 11A and 11B;

FIG. 30 is a view showing an example of the structure of the plasma display panel; and

FIG. 31 is a partial cross-sectional schematic view showing the conventional electric-field jet method.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Before the description of the present invention proceeds, it is to be noted that like parts are designated by like reference numerals throughout the accompanying drawings.

Hereinbelow, embodiments according to the present invention are described in detail based on the accompanying drawings.

I. Basic Applicative Examples

First Embodiment

FIG. 1 is a partial cross-sectional schematic view for explaining a fluid applying apparatus capable of embodying a fluid applying method according to a first embodiment of the present invention.

Reference numeral 1 denotes a piston, and 2 denotes a housing for housing this piston 1 therein. In the case where the applying material can be treated as a nonconductive one, the housing 2 may be made of either an insulative material or a conductive material. When a conductive material is used for the whole housing 2, the nozzle tip end, which is the closest to the substrate, is the highest in electric field strength, so that the function of electric field control has no obstacles. However, when it is not desirable to apply high voltage to the whole housing 2 in terms of safety, a concrete example is shown in FIG. 29, it is appropriate to use an insulative material only for a discharge portion (364 in FIG. 29) where the electrode is to be provided, and to use a conductive material for the other places. Further, the piston 1 may be made of either a conductive material or an insulative material.

The piston 1 is rotatably housed in the fixed-side housing 2. The piston 1 is driven into forward and reverse rotation in a rotational direction indicated by arrow 3 by a rotation transmission device 3A such as a motor.

Reference numeral 4 denotes a thread groove formed on a relative movement surface of either an outer peripheral surface of the piston 1 or an inner peripheral surface of the housing 2, e.g., on the outer peripheral surface of the piston 1, 5 denotes an inlet port of applying fluid, 6 denotes an end face of the piston 1, 7 denotes its fixed-side opposing surface, 8 denotes a discharge nozzle formed at a center portion of the fixed-side opposing surface 7, and 9 denotes a ring-plate shaped housing-side electrode (referred to also as nozzle-side electrode) provided at an outer peripheral portion of the discharge nozzle 8. Numeral 10 denotes an applying fluid which is fed to a space between the thread groove 4 of the piston 1 and the inner peripheral surface of the housing 2 and discharged from the discharge nozzle 8, and 11 denotes a pump chamber formed between the end face 6 of the piston 1 and the fixed-side opposing surface 7 of the housing 2. Numeral 12 denotes a control section for controlling fluid application operation of the fluid applying apparatus, 13 denotes a power supply which is controlled by the control section 12 to apply a voltage to the housing-side electrode 9, 14 denotes a grounded application-object base material (which is an object of application of the applying fluid 10; hereinafter, referred to as substrate as an example), and 15 denotes an elongated portion of the meniscus of the applying fluid 10 having flowed out from the discharge nozzle 8. Rotational motion by the rotation transmission device 3A and move operation of a later-described lateral movement device (e.g., X-Y robot) 92 are each controlled by the control section 12.

In the fluid applying apparatus and method according to the first embodiment of the present invention, the thread groove type is adopted as a pressurization method for the applying fluid 10. In the case of the thread groove type, a pumping pressure P.sub.p is generated by relative rotation between the piston 1, on which the thread groove 4 is formed, and the housing 2. In the case of the electric-field jet method, with a voltage applied to between the electrode 9 provided at the discharge nozzle 8 and the counter-electrode substrate 14, the applying fluid 10 forms a meniscus that projects out from the discharge nozzle 8. Therefore, the applying fluid 10 within the pump chamber 11 has an effect of being sucked (suction pressure P.sub.e) toward the discharge nozzle by the capillary phenomenon. The pumping pressure P.sub.p by the thread groove 4 can be made sufficiently larger than the suction pressure P.sub.e by electric field, so that the flow rate can be determined predominantly from use conditions of the thread groove 4. In the case of the thread groove type, the pumping pressure P.sub.p is proportional to the viscosity of the applying fluid 10, and fluid resistance R.sub.n of the discharge nozzle 8 is also proportional to the viscosity of the applying fluid 10. Because the flow rate Q's equation is Q=P.sub.p/R.sub.n, the viscosity is canceled by the denominator and the numerator of the flow rate's equation, thus the flow rate is independent of the viscosity.

Even in the case of the thread groove type dispenser, an auxiliary air pressure for introducing the applying fluid to the thread groove portion needs to be applied from an auxiliary-air-pressure feed device 5A under control of the control section 12 as shown in FIG. 1. However, the auxiliary air pressure in this case is sufficiently small relative to the pumping pressure of the thread groove. For example, if the pumping pressure is 1 to 3 MPa, then the auxiliary air pressure may be about 0.05 to 0.2 MPa, which does not result in a large effect.

Accordingly, a stable ultrafine-line application, in which the flow rate is less dependent on viscosity changes due to environmental temperature changes or the like, can be achieved by a combination of thread groove type and electric-field jet method dispensers thanks to the control of the rotation transmission device 3A and the power supply 13 by the control section 12.

Hereinbelow, an example of the fluid applying method, from the start of application to continuous application to be executed under the control of the control section 12, is explained.

At first, a specified voltage V is applied from the power supply 13 to between the housing-side electrode 9 and the counter-electrode substrate 14 under the control of the control section 12, by which an electric field is formed between the housing-side electrode 9 and the substrate 14. By using a conductive base plate 90 set at the lower face of the substrate 14, the substrate-side electrode may be grounded through this base plate 90. A high voltage (e.g., 0.5 to 3 kV) is applied to the housing-side electrode 9. When the rotation of the thread groove 4 is started by the rotation transmission device 3A under the control of the control section 12, the pumping pressure P.sub.p is generated by the thread groove 4, causing the applying fluid 10 to flow out from the opening of the nozzle 8 toward the substrate 14, by which a generally conical shaped meniscus 15 of the applying fluid 10 is formed so as to extend from near the nozzle opening toward the substrate 14. From this point on, the meniscus 15 of the applying fluid 10 promptly comes into a longitudinally and generally conically elongated state due to the effects of both the electric field, formed between the electrode 9 and the substrate 14, and the pumping pressure P.sub.p generated by the thread groove 4. By providing a state in which the applying fluid 10 is allowed to drop down from the tip end (lower end) of the elongated portion of the meniscus 15, since the tip end of the meniscus 15 is sufficiently thinner than the nozzle diameter, ultrafine lines that are sufficiently smaller than the nozzle diameter can be drawn by making the discharge nozzle 8 and the substrate 14 move relative to each other under the control of the control section 12 (for example, by making the housing 2 and the rotation transmission device 3A and the like integrally moved along the substrate surface and in two orthogonal directions by the drive of the lateral movement device 92 such as an X-Y robot under the control of the control section 12 against the fixed substrate 14).

Next, in the state in which a continuous application line of the applying fluid 10 is being drawn, the application line can be interrupted in the following way. The rotation of thread groove 4 is rapidly stopped by the rotation transmission device 3A while the voltage applied from the power supply 13 to between the electrode 9 and the substrate 14 is kept ON under the control of the control section 12 while the continuous application line is being drawn. Further, after the rapid stop, the piston 1, on which the thread groove 4 is formed, is reversely rotated a slight amount by the rotation transmission device 3A under the control of the control section 12. In this way, the meniscus 15 of the applying fluid 10 formed from the discharge nozzle tip end toward the substrate 14 can be separated and cut off from the substrate 14 side, so that the terminating end of the drawing line upon an end of application can be drawn at high grade. Conversely, the application can be started by exerting such control that the rotational speed of the thread groove 4 slightly overshoots its steady-state rotational speed immediately after a start of rotation, i.e., that the discharge pressure reaches a peak pressure immediately after the start. By doing so, the applying fluid 10 that has penetrated deep inside the discharge nozzle 8 by negative pressure can be rapidly discharged. In the case where a long time is taken from an end of application until a start of application, it is appropriate that while the voltage to be applied to the housing-side electrode 9 is turned OFF after an end of application, the voltage is turned ON simultaneously with the rotation of the thread groove 4 at the start of the application. Also, as is applicable to later-described other embodiments, the tip end of the discharge nozzle 8 may be set sufficiently closer to the substrate 14 at the start of application (e.g., the distance .delta. between the tip end of the discharge nozzle 8 and the substrate 14 is set to .delta.=50 to 100 .mu.m), and in this state, the distance .delta. may be returned to the steady state (e.g., .delta.=1.0 to 2.0 mm) immediately after the starting end of the application line has been drawn.

In this way, the starting end of a drawing line at the start of application can be drawn at high grade.

In the conventional example of the electric-field jet method, as described before, it has been necessary to apply a large air pressure (e.g., 1.5 to 3 MPa or more) to the pressurization device 508 (FIG. 31) when a sufficiently large flow rate is required. In this case, it has been difficult to draw starting and terminating ends of drawing lines at high grade because of the poor responsivity on account of the issues similar to those of the air type dispenser.

In contrast to this, when the starting and terminating ends of drawing lines are drawn by the thread groove type as in the fluid applying apparatus of the first embodiment, it becomes possible to adopt such methods as (1) interposing an electromagnetic clutch between a motor and a pump shaft to connect or release this electromagnetic clutch for turn-ON or -OFF of discharge, and (2) using a DC servomotor to perform a rapid rotation start or a rapid stop of a pump shaft, in which cases the control responsiveness for treating high-viscosity powder and granular materials becomes more advantageous as compared with the air type. In addition, under the control of the control section 12, when the application is interrupted, the voltage applied between the housing-side electrode 9 and the substrate 14 by the power supply 13 may be turned OFF simultaneously with the stop of the rotation of the motor 3A. Otherwise, the voltage may be turned OFF by the power supply 13 at a timing slightly delayed under the control of the control section 12, taking into consideration that the responsiveness of the motor rotational-speed control is slower than the electric field control.

FIG. 2 and FIGS. 3A and 3B are partial cross-sectional schematic views for explaining a fluid applying apparatus that can carry out a fluid applying method according to a second embodiment of the present invention, where (A), (B), and (C) of FIG. 2 show processes from a state of continuous application to a state of application interruption and further to a state of application start, respectively. The piston shaft of the dispenser used in the fluid applying apparatus and method according to the second embodiment is so structured as to be capable of making rotation and rectilinear motion at the same time by virtue of its two-degrees-of-freedom actuator as a concrete example is shown in FIG. 10.

Reference numeral 101 denotes a piston, and 102 denotes a housing for housing this piston 101 therein. The piston 101 is housed so as to be capable of making rotational motion and rectilinear motion independently of each other against the fixed-side housing 102. In the case where the applying material can be treated as a nonconductive one, the housing 102 may be made of either an insulative material or a conductive material. When a conductive material is used for the whole housing 102, the nozzle tip end, which is the closest to the substrate, is the highest in electric field strength, so that the function of electric field control has no obstacles. However, when it is undesirable to apply any high voltage to the whole housing 102 in terms of safety, as a concrete example is shown in FIG. 29, it is appropriate to use an insulative material only for the discharge portion (364 in FIG. 29) where the electrode is to be provided, and to use a conductive material for the other places. Further, the piston 101 may be made of either a conductive material or an insulative material. For the rotational motion, the piston 101 can be driven into rotational motion in a direction of arrow 103 by a rotation transmission device 103A such as a motor, and for the rectilinear motion, driven forward and backward in a direction of arrow 104 by an axial-direction movement device 104A such as an air cylinder. These rotational motion and rectilinear motion and the voltage application operation by a power supply 115 are controlled by a control section 116. That is, the control section 116 controls fluid application operation of the fluid applying apparatus.

Reference numeral 105 denotes a thread groove formed on a relative movement surface of either an outer peripheral surface of the piston 101 or an inner peripheral surface of the housing 102, e.g., on the outer peripheral surface of the piston 1, 106 denotes an inlet port of applying fluid, 107 denotes an end face of the piston 101, 108 denotes its fixed-side opposing surface, 109 denotes a discharge nozzle formed at a center portion of the fixed-side opposing surface 108, and 110 denotes a ring-plate shaped housing-side electrode (referred to also as nozzle-side electrode) provided at an outer peripheral portion of the discharge nozzle 109. Numeral 111 denotes an applying fluid which is fed to a space between the thread groove 105 of the piston 101 and the inner peripheral surface of the housing 102 and discharged from the discharge nozzle 109, 112 denotes a pump chamber formed between the end face 107 of the piston 101 and the fixed-side opposing surface 108 of the housing 102, 113 denotes an elongated portion of the applying fluid 111 having flowed out from the discharge nozzle 109, and 114 denotes a substrate (which is an example of the application object) placed on a grounded conductive base plate 93. To between the housing-side electrode 110 side and the substrate 114 side, a specified voltage V is applied by the power supply 115 (FIGS. 3A and 3B) controlled by the control section 116.

FIG. 2 (A) shows a state in which the applying fluid 111 is being continuously applied onto the substrate 114. In this state, under the control of the control section 116, the applying fluid 111 is allowed to flow out from the discharge nozzle 109 by a pumping pressure that is generated by the rotation of the piston 101, which is the thread groove shaft, in the direction of arrow 103 by the rotation transmission device 103A, whereas the meniscus 113 of the applying fluid 111, which is a dielectric applying material, is simultaneously formed into an increasingly-thinning and generally conical tapered shape by an effect of an electric field that has been generated between the electrode 110 and the substrate 114 by the power supply 115 under the control of the control section 116. Therefore, an application line whose line width is smaller than the inner diameter of the discharge nozzle 109 can be drawn on the substrate 114.

FIG. 2 (B) shows a case in which the continuous application line is interrupted. A detailed view of FIG. 2 (B) is shown in FIG. 3B. Under the control of the control section 116, when the piston 101 is rapidly moved up relative to the cylinder 102 along a direction of upward arrow 104 by the axial-direction movement device 104A with the rotation of the piston 101 in the direction of arrow 103 maintained, the pressure in the pump chamber 112, which is upstream of the discharge nozzle 109, rapidly drops, resulting in a negative pressure. In this case, since the thread groove pump composed of the thread groove 105 of the piston 101 and the inner circumferential surface of the housing 102 is used as the fluid supply source for the applying fluid 111, the fluid cannot be fed to the pump chamber 112 at flow rates more than a maximum flow rate Q.sub.max, which depends on the rotational speed and the thread groove shape. Therefore, given a volumetric increment Q.sub.p per unit time of a gap portion generated by a rapid up of the piston 101, setting the piston diameter and the piston speed so that Q.sub.p>Q.sub.max allows a sufficiently large negative pressure to be generated in the pump chamber 112. This negative pressure is referred to as "inverse squeeze pressure."

If a voltage is applied to between the electrode 110 and the substrate 114 by the power supply 115 under the control of the control section 116 while the piston 101 is moving up, then the applying fluid 111, which is present on the substrate side from the discharge nozzle 109 is subjected to a force f.sub.1 of such an action as to be projected toward the substrate side by an electric field. At the same time, the applying fluid 111 is subjected to such a suction force f.sub.2 as to tend to return to the inside of the discharge nozzle 109 by a negative pressure generated in the pump chamber 112. These projecting force f.sub.1 and suction force f.sub.2 are balanced with each other, by which the meniscus 113 of the applying fluid 111 is enabled to maintain a constant shape. The magnitude of the projecting force f.sub.1 of the applying fluid 111 and the shape of the meniscus 113 can be controlled by the control section 116 depending on the magnitude of the voltage or on frequency selection with the use of alternating current. The magnitude of the suction force f.sub.2 can be controlled by the control section 116 by setting the speed of rapid up of the piston 101 as described before. For example, after the piston 101 is rapidly moved up to make the tip end position of the meniscus 113 released from the substrate 114, the piston 101 may be moved up slowly. Using such a method makes it possible that a distance h between the substrate 114 and the tip end of the fluid meniscus 113 can be maintained at a constant value while the application is at interruption.

FIG. 2 (C) shows a case where the application is started from an interrupted state. In this case, converse to FIG. 2 (B), the piston 101 is moved down by the axial-direction movement device 104A under the control of the control section 116. When the piston 101 is moved down, a positive squeeze pressure is generated in the pump chamber 112. If the down speed of the piston 101 is too high, the squeeze pressure becomes too large, giving rise to a risk that a `thickening` may be formed at an application starting portion of a drawing line. Therefore, the down speed of the piston 101 may be set within such a range as not to cause this `thickening`. A continuous application or an intermittent application having short line lengths can be implemented by repeating the operations of the continuous application, the application interruption, and the application start of above FIG. 2 (A) to (C) in a short cycle. Now given a line width `b` of application lines and a length L of application lines, a relationship that L>b is defined as a continuous application, and a relationship that L.apprxeq.b or that L<b is defined as an intermittent application.

As a method other than above FIG. 2 (B) and (C), it is also possible to interlock the rapid up operation of the piston 101 by the axial-direction movement device 104A and the operation of nullifying the electric field (zeroing the voltage) by turn-off of the power supply 115 by means of the control section 116, in which case the applying fluid 111 projected from the discharge nozzle 109 can be sucked at once by the interior of the discharge nozzle 109 so that the application can be interrupted. For start of the application, the down operation of the piston 101 by the axial-direction movement device 104A and the operation of applying a voltage by turn-on of the power supply 115 may be interlocked by the control section 116.

Although the above description has been given on a case where starting and terminating ends of continuous drawing lines are applied for coating at high grade, yet effects of the present invention can be utilized also for ultrafast intermittent application. With the use of a two-degree-of-freedom actuator (more specifically, rotation transmission device 103A and axial-direction movement device 104A) such as shown FIGS. 2 to 3B, when the piston 101 is put into reciprocating motion at a high frequency, there occurs a positive squeeze pressure having a sharp peak pressure. The reason of this is as follows. When the piston 101 moves down at high speed, the applying fluid 111 that has no escape way in a confined gap portion, given a large fluid resistance of the discharge nozzle 109, flows back toward the thread groove pump. However, because of the high internal resistance of the thread groove pump, there is generated a pressure proportional to the amount of this back flow and the internal resistance. Now, forming an electric field between the nozzle-side electrode 110 and its counter-electrode substrate 114 enables the meniscus 113 at the nozzle tip end to maintain an axially symmetric shape at all times. Further, surfa