JP2011031175A - Coating apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a coating apparatus capable of surely detecting a bubble. <P>SOLUTION: A capacity sensor 91 is stuck onto an inner wall of a head cylinder 81. The capacity sensor 91 includes a flexible substrate 92 whereon electrode patterns 93 are disposed to form a narrow gap area present therebetween functioning as a capacity measurer C1. A bubble detector judges the condition of bubbles based on the frequency of a pulse signal whose cycle varies according to the time constant determined by the capacity and the resistance of the capacity measurer C1. Since the frequency increases if bubbles are contained in ink in a greater number, the bubble detector determines that the bubbles present therein exceeds an allowable limit when the frequency exceeds a predetermined frequency threshold. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a coating apparatus.

  An organic electroluminescence element (organic EL element) is formed of a fluorescent organic compound that emits light when an electric field is applied, and an organic light emitting diode (hereinafter referred to as OLED) using the organic light emitting diode. A display device including a display panel having an element in each pixel has attracted attention as a next-generation display device.

  The organic EL element includes an anode electrode, a cathode electrode, and an organic EL layer formed between the pair of electrodes and having, for example, a light emitting layer, a hole injection layer, and the like. In the organic EL element, light is emitted by energy generated by recombination of holes and electrons in the light emitting layer.

  The light emitting layer, the hole injection layer, and the like of such an organic EL element are formed by applying a solution to a region partitioned by a partition and drying the solvent. For application of the solution, for example, a coating apparatus such as a nozzle printing method is used.

  This coating apparatus includes a head portion, and one nozzle for discharging a solution to be coated is provided at the tip of the head portion. Then, by applying pressure, the solution to be discharged is applied as a liquid column.

  For example, in Patent Document 1, a groove corresponding to a predetermined pattern shape to which the organic EL material is to be applied is formed on the substrate, and the substrate and the nozzle are relatively moved so that the nozzle is along the groove. Thus, there is disclosed a method for manufacturing an organic EL display device comprising a step of pouring and applying an organic EL material discharged from the nozzle into the groove.

JP 2002-75640 A

  In the method described in Patent Document 1, bubbles are accumulated in the discharge nozzle for some reason as shown in FIG. 16 while the discharge nozzle is continuously discharging the organic EL material (an example of ink). There was a case. When bubbles are accumulated in the discharge nozzle, the discharge amount of the organic EL material discharged from the discharge nozzle changes unintentionally, and the discharge amount of the organic EL material becomes unstable. Discharging may stop.

  This bubble is not detected. For this reason, the nozzles must be inspected regularly or when the discharge amount becomes unstable, and workability is reduced.

  The present invention has been made in view of such a conventional problem, and an object thereof is to provide a coating apparatus capable of accurately detecting bubbles.

In order to achieve this object, a coating apparatus according to the first aspect of the present invention includes:
A solution tank for storing the solution;
A head portion for supplying the solution from the solution tank, filling the supplied solution into a head cylinder and applying the solution to a substrate;
A capacitance sensor disposed in the head cylinder of the head portion and having a capacitance measuring unit;
A bubble detection unit configured to detect a state of bubbles contained in the solution based on the volume acquired by the volume measurement unit of the volume sensor;

A nozzle plate that is disposed in a lower portion of the head cylinder and has a nozzle from which the solution is discharged;
The capacitance measuring unit of the capacitance sensor may be disposed in the vicinity of the nozzle plate.

  The capacity measuring unit of the capacity sensor may be arranged on an upper part of the head cylinder.

The capacitive sensor is arranged in the head cylinder by forming a plurality of electrode patterns on a flexible substrate, and the substrate is attached to the inner wall of the head cylinder,
The capacitance measuring unit may be formed by narrowing an interval between the plurality of electrode patterns.

The head portion includes a filter disposed in an intermediate portion in the head cylinder,
The capacitance measuring unit of the capacitance sensor may be formed using the filter.

The bubble detection unit
An oscillation circuit that generates a pulse signal having a frequency determined by a time constant between the capacitance measurement unit and the resistor of the capacitance sensor;
A bubble determination unit that determines the state of bubbles contained in the solution by comparing the frequency of the pulse signal generated by the oscillation circuit with a preset frequency threshold value. Good.

  The solution may be an organic EL material.

  According to the present invention, bubbles can be accurately detected.

It is a figure which shows the electronic device (digital camera) in which the light-emitting device manufactured using the coating device which concerns on Embodiment 1 of this invention is integrated. It is a figure which shows the electronic device (computer) in which the light-emitting device manufactured using the coating device is integrated. It is a figure which shows the electronic device (cellular phone) in which the light-emitting device manufactured using the coating device is integrated. It is a figure which shows the structure of a light-emitting device. FIG. 5 is a circuit diagram illustrating a configuration of each pixel circuit illustrated in FIG. 4. It is sectional drawing of the pixel circuit shown in FIG. It is a figure which shows the manufacturing method of a light-emitting device. It is a figure which shows the nozzle printing method. It is a figure which shows the structure of a coating device. It is a figure which shows the structure of the head part shown in FIG. It is sectional drawing of the head part shown in FIG. It is a figure which shows a capacity | capacitance sensor. It is the circuit diagram which shows a bubble detection part, and the wave form diagram of a pulse signal. It is a figure which shows the relationship information for determining whether a bubble exceeds allowable amount. It is a figure which shows determination of whether a bubble exceeds the allowance. It is a figure which shows the conventional subject.

Hereinafter, an electronic apparatus, a light-emitting device, a method for manufacturing the light-emitting device, and a coating apparatus used for manufacturing the light-emitting device according to embodiments of the present invention will be described with reference to the drawings.
In the present embodiment, an active drive type light emitting device using a bottom emission type organic EL (electroluminescence) element will be described as an example. The bottom emission type organic EL element has a structure in which light of the organic EL element is emitted to the outside through a substrate on which the organic EL element is formed. Note that the light-emitting device of this embodiment is also used as a display device.
(Embodiment 1)
The light emitting device is incorporated in an electronic device such as a digital camera 200 as shown in FIG. 1, a computer 210 as shown in FIG. 2, and a mobile phone 220 as shown in FIG.

  As shown in FIGS. 1A and 1B, the digital camera 200 includes a lens unit 201, an operation unit 202, a display unit 203, and a viewfinder 204. A light emitting device is used for the display unit 203.

  A computer 210 illustrated in FIG. 2 includes a display unit 211 and an operation unit 212, and a light emitting device is used for the display unit 211.

  A mobile phone 220 shown in FIG. 3 includes a display unit 221, an operation unit 222, a receiver unit 223, and a transmitter unit 224. A light emitting device is used for the display unit 221.

  As shown in FIG. 4, such a light emitting device includes a TFT panel 11, a display signal generation circuit 12, a system controller 13, a select driver 14, a power supply driver 15, and a data driver 16. .

  The TFT panel 11 includes a plurality of pixel circuits 11 (i, j) (i = 1 to m, j = 1 to n, m, n: natural numbers).

  Each pixel circuit 11 (i, j) is a display pixel corresponding to one pixel of the image, and is arranged in a matrix. As shown in FIG. 5, each pixel circuit 11 (i, j) includes an organic EL element E, transistors T1 and T2, and a capacitor Cs. Here, the transistors T1 and T2 and the capacitor Cs form a pixel drive circuit DC.

  The organic EL element E is a current-controlled light-emitting element (display element) that emits light by utilizing a phenomenon that light is emitted by excitons generated by recombination of electrons and holes injected into an organic compound. It emits light with a luminance corresponding to the current value of the current.

  Transistors T1 and T2 in the pixel drive circuit DC are TFTs (Thin Film Transistors) configured by n-channel FETs (Field Effect Transistors).

  The transistor T1 is a driving transistor for the organic EL element E, and has a drain connected to the anode line La (j) and a source connected to the anode electrode of the organic EL element E.

  The transistor T2 is a transistor that functions as a switch for selecting the organic EL element E, and has a drain connected to the data line Ld (i), a source connected to the gate of the transistor T1, and a gate connected to the select line Ls (j). Connected to.

  The capacitor Cs is for holding the voltage between the gate and the source of the transistor T1, and is connected between the gate and the source of the transistor T1.

In the case of three colors of red (R), blue (B), and green (G), the light emitting device includes such a pixel circuit 11 (i, j) for each color.
Further, the pixel circuit 11 (i, j) may include three transistors.

  For example, the display signal generation circuit 12 is supplied with a video signal Image such as a composite video signal and a component video signal from the outside, and acquires display data Pic and a synchronization signal Sync such as a luminance signal from the supplied video signal Image. Is. The display signal generation circuit 12 supplies the acquired display data Pic and synchronization signal Sync to the system controller 13.

  The system controller 13 controls the correction processing, writing operation, and light emission operation of the display data Pic based on the display data Pic and the synchronization signal Sync supplied from the display signal generation circuit 12.

  The correction processing of the display data Pic is based on the display data Pic supplied from the display signal generation circuit 12 based on the threshold voltage Vth of the drive transistor (transistor T1) of each pixel circuit 11 (i, j) and the current amplification factor β. Is a process of generating a corrected gradation signal.

  The writing operation is an operation of writing a voltage corresponding to the gradation signal generated in the capacitor Cs of each pixel circuit 11 (i, j), and the light emitting operation is a current corresponding to the voltage held in the capacitor Cs. Is supplied to the organic EL element E to cause the organic EL element E to emit light.

  In order to perform such control, the system controller 13 generates various control signals and supplies them to the select driver 14, the power supply driver 15, and the data driver 16, and supplies the generated gradation signals to the data driver 16.

  The select driver 14 is a driver that sequentially selects rows of the TFT panel 11, and is configured by, for example, a shift register. The select driver 14 is connected to the gates of the transistors T1 and T2 of each pixel circuit 11 (i, j) via a select line Ls (j) (j = 1 to n).

  Based on the control signal supplied from the system controller 13, the select driver 14 sequentially selects the pixel circuits 11 (1,1) to 11 (m, 1),. By outputting the Hi level select signal Vselect (j) to the pixel circuits 11 (1, n) to 11 (m, n), the rows of the TFT panel 11 are sequentially selected.

  The power supply driver 15 is a driver that outputs signals Vsource (1) to Vsource (n) of the voltage VL or VH to the anode lines La (1) to La (n), respectively. The power supply driver 15 is connected to the drain of the transistor T1 of each pixel circuit 11 (i, j) via the anode lines La (1) to La (n), respectively.

  The data driver 16 is a driver that applies the voltage signals Sv (1) to Sv (m) to the data lines Ld (1) to Ld (m) based on the gradation signal supplied from the system controller 13.

  Note that the light-emitting device is not limited to a configuration in which an even number of light-emitting elements are fixed and used as a set of pixels, and a configuration in which one light-emitting element is shared among a plurality of logical pixels can be employed.

  For example, one light emitting element is used to form five types of logic pixels. Specifically, one light emitting element is used as the center of a logical pixel, and the rest is used as a part of a logical pixel centered on a peripheral pixel. In this way, by using one light emitting element a plurality of times, the resolution can be increased more than the configuration in which a set of pixels is fixed to emit light.

  FIG. 6 is a cross-sectional view of the pixel circuit 11 (i, j) of the light-emitting device. As shown in FIG. 6, the light-emitting device is opposed to the pixel electrode (anode electrode) 42, the light-emitting layer 45, and the pixel circuit 11 (i, j). An electrode (cathode electrode) 46.

  Note that 30R indicates a red light emitting element (organic EL element E), and 45G1 and 45G2 indicate green light emitting layers. In the present embodiment, a configuration including only the light emitting layer 45 as an organic EL layer (organic layer) contributing to light emission is described as an example. However, the present invention is not limited thereto, and the organic EL layer includes a hole injection layer, a light emitting layer, and the like. Or a hole injection layer, an interlayer, and a light emitting layer.

  On the substrate 31 of each light emitting pixel, a transistor T1 formed by patterning a gate conductive layer and a gate electrode T1g of the transistor T1 are formed. A data line Ld (i) extending in the column direction is formed on the substrate 31 adjacent to each light emitting pixel by patterning the gate conductive layer.

  The pixel electrode 42 is made of a conductive material having translucency, such as ITO (Indium Tin Oxide), ZnO, or the like. Each pixel electrode 42 is insulated from the pixel electrode 42 of another adjacent light emitting pixel by an interlayer insulating film 47.

  The interlayer insulating film 47 is formed of an insulating material, for example, a silicon nitride film, is formed between the two pixel electrodes 42, and insulates and protects the transistors T1 and T2, the select line Ls (j), and the anode line La (j). . A substantially square opening 47a is formed in the interlayer insulating film 47, and a light emitting region of the light emitting pixel is defined by the opening 47a. Further, a groove-like opening 48a extending in the main scanning direction X is formed in the partition wall 48 on the interlayer insulating film 47 over a plurality of light emitting pixels.

  The partition wall 48 is formed by curing an insulating material, for example, a photosensitive resin such as polyimide, and is formed on the interlayer insulating film 47. The partition wall 48 is formed in a stripe shape so as to open the pixel electrodes 42 of a plurality of light emitting pixels along the main scanning direction X together. The planar shape of the partition wall 48 is not limited to this, and may be a lattice shape having an opening for each pixel electrode 42.

  Note that the surface of the partition wall 48 and the surface of the interlayer insulating film 47 may be subjected to a liquid repellent treatment. Here, the liquid repellency indicates the property of repelling both aqueous solvents and organic solvents.

  The light emitting layer 45 is formed on the pixel electrode 42. The light emitting layer 45 has a function of generating light by applying a voltage between the pixel electrode 42 and the counter electrode 46.

  The light emitting layer 45 is made of a known polymer light emitting material capable of emitting fluorescence or phosphorescence, for example, a light emitting material containing a conjugated double bond polymer such as polyparaphenylene vinylene or polyfluorene. In addition, these luminescent materials are appropriately coated with a solution (dispersion) dissolved (or dispersed) in an aqueous solvent or an organic solvent such as tetralin, tetramethylbenzene, mesitylene, and xylene by a nozzle coating method, an inkjet method, or the like. It is formed by volatilizing.

  Here, when a hole injection layer is provided as the organic EL layer, the hole injection layer is provided between the pixel electrode 42 and the light emitting layer 45. The hole injection layer has a function of supplying holes to the light emitting layer 45. The hole injection layer is composed of an organic polymer material that can inject and transport holes, for example, polyethylenedioxythiophene (PEDOT) as a conductive polymer and polystyrene sulfonic acid (PSS) as a dopant. .

  Further, when an interlayer is provided, the interlayer is provided between the hole injection layer and the light emitting layer 45. The interlayer has a function of suppressing electron injection from the light emitting layer 45 to the hole injection layer and facilitating recombination of electrons and holes in the light emitting layer 45, and increases the light emission efficiency of the light emitting layer 45.

  Further, in the case of the bottom emission type, the counter electrode 46 is provided on the light emitting layer 45 side, an electron-injecting lower layer made of a conductive material, for example, a material having a low work function such as Li, Mg, Ca, Ba, Al, etc. This is a laminated structure having an upper layer made of a metal having a high light reflectance.

  In the present embodiment, the counter electrode 46 is composed of a single electrode layer formed across a plurality of light emitting pixels, and for example, a common voltage Vss which is a ground potential is applied. When the organic EL element E is a top emission type, the counter electrode 46 is provided on the light emitting layer 45 side and is a very thin material having a film thickness of about 10 nm, such as Li, Mg, Ca, Ba, etc. A transparent laminated structure having a light transmissive low work function layer made of and a light transmissive conductive layer such as ITO having a thickness of about 100 nm to 200 nm.

  Next, a method for manufacturing the light emitting device according to this embodiment will be described with reference to FIGS. Here, since the transistor T2 illustrated in FIG. 5 is formed in the same process as the transistor T1, a part of the description of the formation of the transistor T2 is omitted.

  First, a substrate 31 made of a glass substrate or the like is prepared. Next, on the substrate 31, for example, a gate conduction made of a Mo film, a Cr film, an Al film, a Cr / Al laminated film, an AlTi alloy film or an AlNdTi alloy film, a MoNb alloy film, or the like by sputtering, vacuum deposition, or the like. A film is formed and patterned into the shape of the gate electrode T1g of the transistor T1 as shown in FIG.

  At this time, although not shown, the gate electrode T2g of the transistor T2 and the data line Ld (i) are also formed. Subsequently, an insulating film 32 is formed on the gate electrode T1g and the data line Ld (i) by a CVD (Chemical Vapor Deposition) method or the like.

  Next, a semiconductor layer made of amorphous silicon or the like is formed on the insulating film 32 by a CVD method or the like. Next, an insulating film made of, for example, SiN is formed on the semiconductor layer by a CVD method or the like.

  Subsequently, the insulating film is patterned by photolithography or the like to form the stopper film 115. Further, a film made of amorphous silicon or the like containing n-type impurities is formed on the semiconductor layer and the stopper film 115 by a CVD method or the like, and this film and the semiconductor layer are patterned by photolithography or the like. As shown in FIG. 7B, the semiconductor layer 114 and the ohmic contact layers 116 and 117 are formed.

  Next, after forming a transparent conductive film such as ITO on the insulating film 32 by a sputtering method, a vacuum deposition method, or the like, the pixel electrode 42 is formed by patterning by photolithography.

  Subsequently, a contact hole which is a through hole (not shown) is formed in the insulating film 32, and then, for example, a Mo film, a Cr film, an Al film, a Cr / Al laminated film, an AlTi alloy film or an AlNdTi alloy film, A source-drain conductive film made of a MoNb alloy film or the like is formed by sputtering, vacuum deposition, or the like, and patterned by photolithography to form a drain electrode T1d and a source electrode T1s as shown in FIG. 7B. . At the same time, the anode line La (j) is formed. At this time, the source electrode T1s of the transistor T1 is formed so as to overlap a part of the pixel electrode 42, respectively.

  Subsequently, an interlayer insulating film 47 made of a silicon nitride film is formed by CVD or the like so as to cover the transistor T1 and the like, and then an opening 47a is formed by photolithography as shown in FIG. 7C.

  Next, photosensitive polyimide is applied so as to cover the interlayer insulating film 47, and is patterned by exposure and development through a mask corresponding to the shape of the partition wall 48. As shown in FIG. A partition wall 48 is formed.

  Next, a pixel provided between the partition walls 48 and surrounded by an opening 47a using a nozzle printing device that continuously flows an organic compound-containing liquid containing a light emitting polymer material (R, G, B) from the nozzle. It is applied on the electrode 42. The application is performed in the main scanning direction X along the partition wall 48.

  Next, an organic compound-containing liquid containing the light emitting polymer material (R, G, B) is applied onto the pixel electrode 42 using a coating apparatus. The application is performed in the main scanning direction X along the partition wall 48.

  A nozzle printer is used as the coating device. The nozzle printer is an on-demand printer that does not require a plate. As shown in FIGS. 8A and 8B, this coating apparatus generally includes a head portion 78 having a nozzle that continuously discharges a solution 51 made of an organic compound-containing liquid, and the head portion 78 is attached to the substrate 31. The solution 51 is applied to the application region on the substrate 31 by moving along the upper application region.

  8A shows a configuration in the case where only one head portion 78 is provided, and FIG. 8B shows a configuration in the case where two head portions 78 are provided. Here, FIG. 8B shows a case where the coating apparatus has two head portions 78, but the present invention is not limited to this, and the coating device may have three or more head portions 78.

  The solution for forming the light emitting layer 45 contains the above-described polymer light emitting material. As the solvent of this solution, an aqueous solvent or an organic solvent such as tetralin, tetramethylbenzene, mesitylene, and xylene is used. In the solution (dispersion), the polymer light emitting material is dissolved (or dispersed) in this organic solvent. ing.

  As shown in FIGS. 8A and 8B, the solution 51 is discharged from the nozzle of the head unit 78 and applied onto the substrate 31. The head portion 78 moves along the main scanning direction X (the left-right direction in FIGS. 8A and 8B) in which the partition walls 48 are formed while discharging the solution 51 between the partition walls 48. In addition, when performing application | coating to each row | line | column continuously, as shown to Fig.8 (a), (b), while the head part 78 was outside the board | substrate 31, the partition 48 was formed in the board | substrate 31. FIG. It is moved by a predetermined distance in the sub-scanning direction Y (vertical direction in FIGS. 8A and 8B) perpendicular to the direction.

  By repeating this, the solution 51 is applied to a predetermined row. It should be noted that while the head unit 78 is outside the substrate 31, the solution 51 may remain discharged or the discharge may be temporarily stopped.

  Here, as shown in FIG. 8A, when the coating apparatus has only one head part 78, the application is performed by alternately changing the moving direction of the head part 78 for each row.

  As shown in FIG. 8B, when the coating apparatus has two head portions 78, the coating is performed by alternately changing the moving direction of the head portions 78 every two rows. Instead of moving the substrate 31, the head portion 78 may be moved by a predetermined distance in a direction orthogonal to the direction in which the partition wall 48 is formed.

  In this way, the organic compound-containing liquid is poured between the partition walls 48 and the solvent is volatilized, whereby the light emitting layer 45 is formed. When the light emitting layer 45 is formed, the counter electrode 46 is formed thereon.

  When forming the hole injection layer, before forming the light emitting layer 45, the organic compound-containing liquid containing the hole injection material is discharged as a coating device that continuously flows or as a plurality of individual droplets. The ink is selectively applied onto the pixel electrode 42 surrounded by the opening 47a by an inkjet apparatus. Subsequently, the substrate 31 is heated in an air atmosphere to volatilize the solvent of the organic compound-containing liquid, thereby forming a hole injection layer. The organic compound-containing liquid may be applied in a heated atmosphere.

  Moreover, when forming an interlayer further, the organic compound containing liquid containing the material used as an interlayer is apply | coated on a positive hole injection layer using an application | coating apparatus. Heat drying in a nitrogen atmosphere or heat drying in a vacuum is performed to remove residual solvent and form an interlayer. The organic compound-containing liquid may be applied in a heated atmosphere.

  Subsequently, two layers including a layer made of a material having a low work function such as Li, Mg, Ca, Ba and a metal layer having a high light reflectance such as Al are formed on the substrate 31 formed up to the light emitting layer 45 by vacuum deposition or sputtering. A counter electrode 46 having a structure is formed.

  Next, a sealing resin made of an ultraviolet curable resin or a thermosetting resin is applied on the substrate 31 outside the light emitting region where the plurality of light emitting pixels are formed, and is bonded to the sealing substrate (not shown) and the substrate 31. Next, the sealing resin is cured by ultraviolet rays or heat, and the substrate 31 and the sealing substrate are bonded. The sealing resin may be applied to the sealing substrate and bonded to the substrate 31. Further, a counterbore portion having a certain depth may be provided on the sealing substrate, and a desiccant may be attached.

  In order to apply such a solution of each layer of the organic EL element E (hereinafter referred to as “ink”), a coating apparatus as shown in FIG. 9 is used. This coating apparatus is an on-demand printer that does not require a plate called a nozzle printer.

  The coating apparatus includes an ink tank 71, an ink supply pipe 72, a pressurizing unit 73, a flow rate detection / control unit 74, a linear drive unit 75, a stage 76, a control unit 77, a head unit 78, Is provided.

The ink tank 71 is for storing ink.
The ink supply pipe 72 guides ink to the head portion 78 and is formed of a flexible material.

The pressurizing unit 73 is for applying pressure to the ink.
The flow rate detection / control unit 74 controls the pressure and flow rate of the ink so that a fixed amount of ink is ejected from the head unit 78, and is attached around the ink supply pipe 72.

The linear drive unit 75 is for scanning the head unit 78 in the main scanning direction X.
The stage 76 fixes the substrate 31 and is movable in the sub-scanning direction Y.

  The control unit 77 applies the ink to the substrate 31 by controlling the entire coating apparatus. The control unit 77 operates the linear drive unit 75 with respect to the substrate 31 in the main scanning direction X, applies one line of ink in the main scanning direction X, and then performs a step operation of the stage 76 in the sub-scanning direction Y. The control unit 77 sequentially performs such control and applies ink to all the lines of the substrate 31.

  The head unit 78 is a mechanism unit that ejects ink, and is attached to the linear drive unit 75. As shown in FIGS. 10 and 11, the head portion 78 includes a head cylinder 81, a cylinder flange 82, a connecting unit 83, a filter 84, a nozzle plate Np, and a nozzle cap Nc.

  The head cylinder 81 is a main body portion of the head portion 78 and is filled with ink guided by the ink supply pipe 72.

  The cylinder flange 82 has a flange shape and is provided on the outer peripheral portion of the head cylinder 81. The cylinder flange 82 is processed integrally with the head cylinder 81 or joined to the head cylinder 81.

  The base unit 75a is a component that constitutes a scanning unit of the linear drive unit 75 of the coating apparatus main body, and is provided with an opening (not shown) for attaching the head unit 78. The head cylinder 81 is inserted into this opening, and the cylinder flange 82 is screwed to the base unit 75a.

  The connection unit 83 connects the tip of the ink supply pipe 72 and the head cylinder 81.

  The filter 84 is for filtering the ink supplied to the head portion 78, and is disposed and fixed at an intermediate portion inside the head cylinder 81.

  The nozzle plate Np is for ejecting ink, and is provided with a nozzle for ejecting ink. When the pressurizing unit 73 applies pressure to the pipe, the ink ejected from the nozzles of the nozzle plate Np becomes the liquid column Lp.

  The nozzle cap Nc is for fixing the nozzle plate Np to the head cylinder 81.

  In addition, the coating apparatus includes a capacitance sensor 91. The capacity sensor 91 detects the capacity of the ink and is provided to determine the presence or absence of bubbles in the head cylinder 81. The capacitance sensor 91 is affixed to a part of the inner wall in the head cylinder 81 as shown in FIG.

  The capacitance sensor 91 includes two capacitance measurement units C1 and C2 as shown in FIG. The capacitance sensor 91 is affixed to the inner wall of the head cylinder 81 so that the capacitance measurement unit C1 is disposed in the vicinity of the nozzle plate Np and the capacitance measurement unit C2 is disposed above the head cylinder 81.

  The reason why the two capacity measuring units C1 and C2 are provided in this way is to enable the air bubbles to be reliably detected in the vicinity of the entrance of the head cylinder 81 into which the ink flows and in the vicinity of the nozzle plate where the air bubbles easily collect.

  The capacitance sensor 91 is formed by wiring an electrode pattern 93 on the flexible substrate 92. The portion where the space between the two electrode patterns 93 is narrow becomes the capacitance measuring units C1 and C2. A protective film (not shown) is formed on the flexible substrate 92 and the electrode pattern 93 so as not to come into direct contact with the ink.

  Since the dielectric constant ε of gas (bubbles) is smaller than the dielectric constant ε of liquid (ink), the dielectric constant ε is small when bubbles are included in the ink. Since the capacitances of the capacitance measuring units C1 and C2 are proportional to the dielectric constant ε, when the bubbles are close to the capacitance measuring units C1 and C2, the capacitances of the capacitance measuring units C1 and C2 are reduced. The coating device detects bubbles by detecting this change.

  Note that the tip of the lead wire lead wire is connected to the electrode pattern 93 in order to extract signals from the capacitance measuring units C1 and C2. Note that the tip of the lead wire may be plated with silver, gold or the like so as to facilitate welding.

  A hole is provided in the side wall of the head cylinder 81, and the lead wire is drawn out from the electrode pattern 93 to the outside through the hole in the side wall. Frit glass is used for sealing the holes.

  Since the coefficient of expansion of frit glass changes depending on the glass transition temperature, an iron-nickel-cobalt alloy having an expansion coefficient approximate to that of frit glass is used for the head cylinder 81.

  The coating apparatus includes a bubble detection unit 94-1 including a capacity measurement unit C1 and a bubble detection unit 94-2 (not shown) including a capacity measurement unit C2 in order to detect bubbles. As shown in FIG. 13A, the bubble detection unit 94-1 includes an oscillation circuit 311, a pulse counter 312, and a bubble determination unit 313 that determines an allowable value of bubbles contained in ink. The The oscillation circuit 311 outputs a pulse signal P1 as shown in FIG. In FIG. 13A, the capacitance measuring unit C1 is represented as a capacitor.

  The pulse counter 312 counts the number of pulses of the pulse signal P1 output from the oscillation circuit 311 and supplies the counted number of pulses to the bubble determination unit 313.

  The bubble determination unit 313 acquires the frequency f of the pulse signal P1 based on the count value supplied from the pulse counter 312, and the state where the bubbles in the ink are present exceeds the allowable value based on the acquired frequency f. It is determined whether or not there is.

  When the bubble is contained in the ink and the dielectric constant ε changes, the capacitance c changes with the capacitance of the measurement unit C1 as c and the resistance value of the resistor R1 as r, and the time constant expressed by the product of the resistance r also changes. To do.

The period T of the pulse signal P1 is proportional to the time constant, that is, T∝c · r. The frequency f of the pulse signal P1 is represented by the following formula (1).
f = 1 / T = 1 / (c · r) (1)

  When bubbles are included in the ink, the relationship between the dielectric constant ε and the frequency f when the bubbles are not included is obtained in advance by experiments or the like. FIG. 14 is an example showing this relationship. If bubbles are included in the ink, the capacity c decreases, and the frequency f increases as shown in Equation (1). In accordance with this relationship, the bubble determination unit 313 determines whether or not a state where bubbles in the ink are allowed is allowed.

  In order to perform this bubble determination, a capacity threshold c_th as shown in FIG. 14 is set in advance. The frequency threshold value f_th corresponding to the capacitance threshold value c_th is obtained by Expression (1) with the resistance value r being constant.

  The bubble determination unit 313 determines that it is acceptable when the frequency f of the acquired pulse signal P1 is equal to or less than the frequency threshold f_th, and determines that it is not acceptable when the frequency exceeds the frequency threshold f_th.

  The bubble determination unit 313 includes a storage unit (not shown), and the storage unit stores relation information as shown in FIG. 14 including the dielectric constant threshold value ε_th and the frequency threshold value f_th.

  Similarly, the bubble detection unit 94-2 includes an oscillation circuit 321, a pulse counter 322, and a bubble determination unit 323 (not shown). The oscillation circuit 321 includes a capacitance measuring unit C2 shown in FIG.

Next, the operation of the bubble detectors 94-1 and 94-2 according to the first embodiment will be described.
As shown in FIG. 15A, if the amount of bubbles 301 in the head cylinder 81 is less than the allowable amount, the capacity c of the capacity measuring unit C1 exceeds the capacity threshold c_th, and the oscillation circuit shown in FIG. The frequency f output by 311 is equal to or lower than the frequency threshold f_th. Further, the capacitance c of the capacitance measuring unit C2 also exceeds the capacitance threshold c_th, and the frequency f is equal to or lower than the frequency threshold f_th.

  For this reason, the bubble determination unit 313 of the bubble detection unit 94-1 and the bubble determination unit 323 of the bubble detection unit 94-2 both determine that the bubble 301 is acceptable.

  As shown in FIG. 15B, when a bubble 301 enters the vicinity of the capacity measuring unit C2 in the head cylinder 81, the capacity c of the capacity measuring unit C2 decreases. When the capacity of the capacity measuring unit C2 becomes equal to or less than the capacity threshold c_th, the frequency f exceeds the frequency threshold f_th, so the bubble determination unit 323 of the bubble detection unit 94-2 determines that the bubble 301 is not allowed.

  As shown in FIG. 15C, when the bubble 301 is lowered to the vicinity of the nozzle plate Np in the head cylinder 81, the capacity c of the capacity measuring unit C1 decreases. When the capacity of the capacity measuring unit C1 becomes equal to or less than the capacity threshold c_th, the frequency f exceeds the frequency threshold f_th, so the bubble determination unit 313 of the bubble detection unit 94-1 determines that the bubble 301 is not acceptable.

  As described above, according to the first embodiment, the coating apparatus includes the capacitance sensor 91 in the head cylinder 81, and the bubble detection units 94-1 and 94-2 are respectively the capacitance measurement units of the capacitance sensor 91. The state of the bubble is detected based on the frequency f that changes according to the time constant between the capacitance c and the resistance value r of C1 and C2.

  Therefore, the coating device can accurately detect bubbles. For this reason, when it is detected that the state of bubbles is unacceptable, the head unit 78 may be inspected, and the workability is improved.

In carrying out the present invention, various forms are conceivable and the present invention is not limited to the above embodiment.
For example, in the above embodiment, the capacitance sensor 91 includes two capacitance measuring units C1 and C2. However, the capacitance sensor 91 may be only one of the capacitance measuring unit C1. Conversely, three or more may be provided.

  In the above embodiment, the capacitance sensor 91 is attached to a part of the inner wall of the head cylinder 81. However, the capacitance sensor 91 may be attached to the entire inner wall of the head cylinder 81.

  In the above embodiment, the capacitance sensor 91 is attached to the inner wall of the head cylinder 81. However, the capacitance sensor 91 may be provided on the nozzle plate Np.

  Moreover, the capacity | capacitance measurement part of the capacity | capacitance sensor 91 may be formed using the filter 84 shown in FIG. Since a resinous material is usually used for the filter 84, electrodes are formed at both ends of the filter, and a capacitance measuring unit is formed using the filter 84 as a dielectric.

  However, PEDOT used when forming the hole injection layer has a low hydrogen ion index, and a metal material is used for the filter 84. In this case, a dielectric is formed on the filter 84, and the capacitance measurement unit of the capacitance sensor 91 is formed using the dielectric as a capacitance measurement unit.

  91 ... Capacitance sensor, 92 ... Flexible substrate, 93 ... Electrode pattern, 94-1, 94-2 ... Bubble detector, 311,321 ... Oscillator circuit, 312,322 ... Pulse counter, 313, 323 ... Bubble determination unit, C1, C2 ... Capacity measurement unit, R1, R2 ... Resistance

Claims (7)

A solution tank for storing the solution;
A head portion for supplying the solution from the solution tank, filling the supplied solution into a head cylinder and applying the solution to a substrate;
A capacitance sensor disposed in the head cylinder of the head portion and having a capacitance measuring unit;
A bubble detection unit that detects a state of bubbles contained in the solution based on the volume acquired by the volume measurement unit of the volume sensor;
An applicator characterized by that. A nozzle plate that is disposed in a lower portion of the head cylinder and has a nozzle from which the solution is discharged;
The coating apparatus according to claim 1, wherein the capacitance measuring unit of the capacitance sensor is disposed in the vicinity of the nozzle plate.   The coating apparatus according to claim 2, wherein the capacitance measuring unit of the capacitance sensor is disposed on an upper portion of the head cylinder. The capacitive sensor is arranged in the head cylinder by forming a plurality of electrode patterns on a flexible substrate, and the substrate is attached to the inner wall of the head cylinder,
The coating apparatus according to claim 1, wherein the capacitance measuring unit is formed by narrowing an interval between the plurality of electrode patterns. The head portion includes a filter disposed in an intermediate portion in the head cylinder,
The coating apparatus according to claim 1, wherein the capacitance measuring unit of the capacitance sensor is formed using the filter. The bubble detection unit
An oscillation circuit that generates a pulse signal having a frequency determined by a time constant between the capacitance measurement unit and the resistor of the capacitance sensor;
A bubble determination unit that determines the state of bubbles contained in the solution by comparing the frequency of the pulse signal generated by the oscillation circuit with a preset frequency threshold value. The coating apparatus according to claim 1, wherein the coating apparatus is characterized in that:   The coating apparatus according to claim 1, wherein the solution is an organic EL material.

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