JP2010040323A - Liquid drop discharge device, liquid drop discharge method, and manufacturing method of organic el element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To enable to realize a liquid drop discharge by which unevenness of film thickness (coating unevenness) and line defect or the like can be reduced. <P>SOLUTION: The nozzle plate 12 has a row of nozzles 5 consisting of a plurality of liquid drop discharge ports 5a-5c with different hole diameters and forms a line pattern on a substrate 25 by discharging ink 17-20 from each liquid drop discharge port 5a-5c. The plurality of liquid drop discharge ports 5a-5c are arranged on a straight line to the line forming direction and enable to increase the liquid drop density in the formed line to suppress the film-thickness unevenness (coating unevenness), and to repair the line by coating on a defect such as a line disconnection. Further, by selecting the liquid drop discharge ports 5a-5c arranged in the line forming direction and changing the hole diameters thereof, the discharge resistance can be controlled. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a droplet discharge device for applying a liquid material to a coating target, a droplet discharge method, and a method for manufacturing an organic EL element using the device and method, and more particularly, a die coater for precision coating. The present invention is applied to a discharge method and a discharge apparatus using the above.

  In recent years, the progress of the advanced video information society centered on the Internet has been remarkable, and lifestyles are about to change drastically due to rapid technological innovation. Accordingly, there has been a demand for a thinner and lighter display with a finer screen that is easier to see, and various display methods corresponding to it have been proposed so far. Below, the representative example is demonstrated.

  One is a CRT (Cathode ray tube) method used in general televisions. The problem with this method is that the depth of the CRT increases as the screen size increases, and the entire display inevitably becomes larger and heavier. That is. An LCD (Liquid crystal display) is a method developed for the purpose of improving these disadvantages.

  The LCD uses a white backlight (CCFL) as a light source, a liquid crystal element has a function as an optical shutter, a color filter is provided in front of the liquid crystal element, and full color display is performed by controlling light transmission. Therefore, the color of the image is transmitted light from the filter and corresponds to the extra color. Furthermore, since the viewing angle of the liquid crystal element is narrow, there is a problem that visibility from both sides is poor. On the other hand, remarkable downsizing is possible as compared with CRT, and it is frequently used as a display for a wall-mounted television or a notebook PC.

  In addition, a system using a PDP (Plasma display panel) has been developed, and commercially available televisions are thin and light. The PDP uses a plasma discharge tube of the three primary colors of light as a light source, and a filter that shields electron beams and near infrared rays on the surface.

  As another method, there is an organic EL display (hereinafter referred to as OLED), and the OLED has a thickness of only 2 mm including the substrate and the sealing, and can be significantly downsized. Moreover, a wide viewing angle is obtained by causing the three primary colors of light to be self-luminous and surface-emitting, and a high contrast and high-speed response are provided, so that a clear image that is not found in conventional displays can be obtained.

  In addition, OLEDs do not require a backlight, operate on batteries with low voltage drive and low power consumption. At present, it is used for mobile phone displays or in-vehicle displays because of its technical ease, and is then considered to be gradually put into practical use in PCs and televisions.

  In addition, the device structure of the OLED is significantly different from the preceding CRT, LCD, PDP and the like. While all other systems have a cell structure, an OLED can function by simply laminating a solid thin film on a substrate. This means that it is superior in principle in thinness, light weight, impact resistance, and flexibility. In addition, there is no restriction on the enlargement of the screen, and it is expected that the manufacturing cost can be kept low.

  The organic EL element has a structure in which an organic light emitting layer is sandwiched between two electrodes, and causes the organic light emitting layer to emit light by passing a current between the electrodes. Although the organic light emitting layer includes one to a plurality of layers, the thickness of each layer is very important in order to emit light efficiently, and the entire organic light emitting layer needs to be a thin film of 1 μm or less. Furthermore, in order to make this a display, it is necessary to pattern the organic light emitting layer with high definition, and this patterning method becomes an important issue.

  Moreover, in order to take out the emitted light, it is necessary to make one of the electrodes transparent. It has been proposed to use a transparent conductive film made of indium / tin oxide (ITO) or the like as the transparent electrode (see, for example, Patent Document 1).

  FIG. 6 is a cross-sectional view showing a schematic configuration of the organic EL display described in Patent Document 1. 101 is a substrate, 102 is a TFT (thin film transistor), 103 is an anode (or cathode), 104 is an organic EL layer, and 105 is Transparent electrode (cathode or anode) such as ITO, 106 is a passivation layer, 107 is an adhesive layer, 108 is a stress relaxation layer, 109 is a black mask, 110 to 112 are color conversion filters, and 113 is a translucent support substrate.

  In the upper light extraction (top emission) type organic EL element having the above-described configuration, the electrode opposite to the substrate 101 is the transparent electrode 105. At this time, by forming a transparent conductive film on the metal thin film, It has been proposed to protect the cathode and reduce the wiring resistance.

  Further, in order to use the transparent conductive film as a cathode, it has been proposed to sandwich the stress relaxation layer 108 between the organic light emitting layer and the transparent conductive film for the purpose of protecting the underlying organic light emitting layer and reducing the electron injection barrier. . For the formation of transparent conductive films, conventional deposition methods and plasma / ion beam assisted deposition methods, ion plating methods, ion beam sputtering methods, etc., which have been used in recent optical communications, are mainly used. In other cases, a wet method such as a sol / gel method or a spray method may be used.

  On the other hand, there is a sputtering method as a method used in mass production apparatuses in thin film manufacturing processes such as semiconductors, flat panel displays, and electronic components. The sputtering method is widely used as a method suitable for mass production because the film formation rate, film composition, and the like are stable, and uniform film formation on a large-area substrate is possible. Furthermore, it has become mainstream because of its high uniformity of film thickness, conductivity and transparency, and excellent fine etching characteristics.

  The film formation method of the organic EL element is roughly classified into a dry method and a wet method. In the dry method, a low molecular material is vacuum-deposited to form a thin film. The low molecular weight hole injection material and the light emitting material are preferably compounds having a molecular weight (Mw) of about 350 or more in order to prevent re-evaporation from the substrate in vacuum. Moreover, in order to prevent decomposition and carbonization, a material having a Mw of about 1200 or less is usually used so that a sufficient vapor deposition rate can be obtained at a low evaporation source temperature of 500 ° C. or less.

  Many low molecular weight materials that can be deposited have a low intermolecular force. Since such materials are easy to move, have a small molecular weight, and have a simple molecular structure, an organic film formed using a solution obtained by dissolving in an organic solvent will be associated with each other over time. As a result, the film is crystallized, and the film tends to be uneven. Therefore, when an organic EL element is manufactured using such an organic film, there is a problem that a pinhole is generated in the film and a short circuit occurs during driving.

  In contrast, even low molecular weight materials can prevent crystallization by using an asymmetric three-dimensional amorphous molecular structure. It is conceivable to form a film.

  In the dry method (low molecular vapor deposition method), an organic EL material placed in a crucible is evaporated by resistance heating and a thin film is stacked on a substrate. When organic light emitting layers of three colors are juxtaposed, a wet method such as photolithography is not applicable because it damages the underlying organic layer. Therefore, it is necessary to form a film only in a necessary portion using a shadow mask. In order to increase the pattern accuracy, it is necessary to increase the distance between the crucible and the substrate, which increases the size of the apparatus. A vapor deposition tank for each organic material is required for continuous operation. For this reason, an apparatus becomes large and an initial investment becomes large. In addition, highly accurate mask alignment is required.

  In the wet method, a polymer material is dissolved or dispersed in a solvent, and a solution (ink) is applied onto a substrate by a spin coating method or a printing method (inkjet method, gravure printing method, offset printing method, etc.) and dried to form a thin film. Form. In addition, by using water-soluble poly (3,4-ethylenedioxythiophene) / polystyrene sulfonic acid (hereinafter referred to as PEDOT / PSS) as the hole injection layer, an organic solvent that is not mixed with water is used. It is possible to stack an interlayer (electronic blocking layer) or a light emitting layer. On the other hand, in the printing method, since the ink has fluidity, it is necessary to provide a bank (partition section), fill the ink in the bank, mix the ink (color mixing), and eliminate the dot shape collapse.

  The PEDOT / PSS film has a low electrical resistance, and can increase the ionization energy of the surface from about 4.8 eV, which is the ionization energy of ITO, to 5.1 to 5.3 eV to promote hole injection. In addition, there is an advantage that the unevenness on the surface of the ITO electrode is smoothed to prevent short circuit (planarization effect).

  However, the PEDOT / PSS film has a high acidity of about pH 1 due to the sulfonic acid group in the PSS, so it corrodes the metal part of the device, dissolves the ITO surface, and diffuses indium ions to the light emitting layer. There was a problem of causing deterioration (quenching) of the light emitting layer. In addition, since PEDOT / PSS is an aqueous dispersion, there is also a problem that it takes time to completely remove moisture in the film. Therefore, after forming a film using a highly volatile organic solvent instead of strong acidity, it is possible to insolubilize in an organic solvent by self-organization utilizing cross-linking by light or heat or formation of hydrogen bonds between substituents. Development of materials is desired.

  When the pixel area is filled with an organic EL element forming material (ink), in order to prevent the discharged ink from flowing out to the adjacent pixel area, a bank that partitions the pixel area is provided, and the pixels surrounded by the bank Fill the area with ink. The pixel area surrounded by the bank is filled with ink much larger than the volume after film formation.

  However, since the display device is generally required to be thin, the bank cannot be formed to be excessively high. For this reason, the behavior of the filled ink differs depending on the wettability (affinity) of the bank and the pixel region surrounded by the bank.

  Conventionally, coating methods such as a spin coater method, a roll coat method, and a die coat method are known as techniques for forming a relatively thin coating film on a semiconductor substrate, a liquid crystal display device, or a color filter substrate. ing. Of these coating methods, the spin coater method is generally suitable for forming a thin and uniform coating film on the order of μm.

  In this spin coater method, a substrate to be coated on which a coating film is to be formed is held by a spin chuck, and a liquid material to be coated, for example, a resist material, is dropped onto the center portion, and then the substrate is rotated at a high speed, This is a method of forming a coating film by diffusing the liquid material from the central part of the substrate toward the outer peripheral part by the generated centrifugal force.

  However, although the spin coater method has a smaller film thickness distribution than other coating methods and is suitable for forming a uniform coating film, about 90% or more of the dropped liquid material is removed from the substrate surface. Since leveling is performed by diffusing to the surroundings, there is a problem in that the liquid is wasted and is disadvantageous in terms of environment and economy.

  Examples of the roll coating method include various printing methods such as intaglio printing, planographic printing, screen printing, and relief printing. However, in an OLED using a glass substrate as a substrate to be printed, scratches and distortion of the substrate are not preferable, so a method of using a hard plate such as a metal printing plate such as a gravure printing method that is representative of intaglio printing is It is unsuitable.

  In addition, an ink in which an organic EL element forming material is dissolved or dispersed in a solvent generally has a low viscosity, and is not suitable for offset printing or screen printing, which is representative of lithographic printing. On the other hand, the relief printing method using a photosensitive resin plate mainly composed of rubber or other resin is suitable for low-viscosity organic light-emitting inks without damaging the glass substrate. Actually, the formation of an organic light emitting layer by a relief printing method has been proposed (see, for example, Patent Document 2).

  FIG. 7 is a schematic configuration diagram of a relief printing apparatus used for manufacturing a printed matter described in Patent Document 2, wherein 121 is an ink replenishing device, 122 is a doctor, 123 is an anilox roll, 124 is a printing relief plate, and 125 is a plate. A cylinder, 126 is a base material, 127 is a stage, 128 is ink, and 128a is an ink pattern.

  The relief printing method is a method in which a printing plate having a convex shape is used, that is, a relief printing plate, ink is supplied to the relief of the relief printing plate with an anilox roller, and the ink on the projection is transferred to the printing material. is there. However, when the ink is transferred to the substrate to be coated by this method, the ink solvent soaks into the resin plate (swells), and the resin plate component, such as a plasticizer, a crosslinking agent, and a photopolymerization initiator, serves as a monomer. When mixed in ink, there is a problem that causes deterioration of device characteristics such as life.

  In consideration of the occurrence of the inconvenience, it has been proposed to use a die coating method (see, for example, Patent Document 3).

FIG. 8 is an explanatory view showing the positional relationship between the fountain die and the backup roll in the die coater type coating apparatus described in Patent Document 3, wherein 131 is a coating film, 132 is a reference surface, and 133a is a downstream lip portion ( lip), 133b upstream lip, 134 ejection openings, h is the coating gap, _{P 1} is a central site, _{P 2} is quarter central site, _{P 0} is the downstream edge (the downstream edges), L is The thickness of the downstream lip, R is the radius of the backup roll, and x is the protruding amount.

  The die coating method has been widely used for applications where thick film coating or high viscosity coating solution is continuously applied. When forming a coating film using the die coating method, the curtain flow method, extrusion method, and bead method are used. Application methods such as are known.

  Among them, the bead method discharges coating liquid from a nozzle provided at the tip of a droplet discharge head of a die coater, and the material to be coated travels relatively at a certain distance (gap) from the tip of the droplet discharge head. In this state, a coating liquid reservoir called a coating liquid bead is formed, and a coating film is formed by drawing out the coating liquid as the material to be coated runs (see Non-Patent Document 1, for example).

In addition, if the bead method is used in which the coating film is continuously formed by supplying the same amount of coating liquid as consumed by the coating film formation from the nozzle, the film thickness uniformity of the formed coating film is high. To be accurate. Furthermore, since there is almost no waste of the coating liquid and the coating liquid feeding path is sealed until it is ejected from the nozzle, it is possible to prevent the coating liquid from deteriorating and mixing of foreign substances, and the quality of the obtained coating film is also improved. Can be kept high.
Japanese Patent No. 3501148, page 6, FIG. Japanese Patent Laying-Open No. 2007-253447, page 20, FIG. Japanese Patent Laid-Open No. 2003-24856, page 14 FIG. Atsuko Okuda FUJIFILM RESEARCH & DEVELOPMENT (No. 52-2007) “Effects of internal flow on upstream side of beads in die coating on downstream side meniscus” page 55 FIG. 1

  Conventionally, the die coating method has a problem that the variation of the formed line (stripe) width and thickness is large and control is difficult. Factors that cause fluctuations in line width and thickness include coating speed, pumping rate (liquid feeding amount), ink viscosity, pressure loss in the liquid flow path, and the gap between the substrate and nozzle (actually, variations in the thickness of the substrate film) Specific examples of ink viscosity include ink base and solvent content, coating liquid temperature fluctuation, ink bulk molecular weight fluctuation (hydrolysis, etc.), temperature difference between coating liquid and manifold (die body), etc. . The uniformity of the film quality (thickness, morphology) of the formed line has been impaired due to slight variations in these factors.

  It can be predicted that the inner wall area of the flow path relative to the cross-sectional area of the fluid is related to the pressure loss. Since the flow becomes easier when the flow path cross-sectional area is increased, the pressure loss is reduced, and when the tube wall surface area is increased, the friction with the tube wall is increased and the flow is difficult to flow, thereby increasing the pressure loss. Therefore, the ratio between the tube wall surface area and the flow path cross-sectional area is related to the pressure loss, and the pressure loss is also affected by physical conditions such as the tube wall roughness. For circular pipes with the same roughness, the pressure difference will vary depending on the pipe diameter, flow velocity, and the type of liquid. When the pressure difference is measured by changing only the flow rate under the same conditions, the pressure loss increases linearly as the flow rate increases.

  When low-viscosity ink is used as the coating liquid, the amount of liquid delivered per unit time will be too small if the liquid discharge pressure is low. In addition, since the liquid shape holding force is too low, a coating liquid bead cannot be formed between the tip of the droplet discharge head and a material to be coated that travels relatively at a constant interval (gap). In this case, droplets are intermittently formed on the material to be coated, and the line pattern is formed by wetting and spreading each other.

  However, when particles, oxide films, or the like that inhibit wetting and spreading are formed on the material to be coated, local discontinuous lines (discontinuities) occur in the line pattern. Further, even when the gap is enlarged, the interval between the droplets formed on the material to be coated is widened, so that wetting and spreading cannot follow and a discontinuous line is generated.

  On the other hand, when the liquid discharge pressure is large, a coating liquid bead is formed between the tip of the liquid droplet discharge head and the material to be coated. To discharge (fill ink) into the pixel area partitioned by the bank, a unit Since the amount of liquid fed per time is excessive, ink overflows from the pixel area and ink rises above the bank. As a result, luminance and chromaticity variations due to color mixing become apparent when the panel is driven. Therefore, in order to form an even line pattern (ink filling) over the entire length without causing ink overflow in the pixel area partitioned by the bank, the liquid discharge pressure (liquid feeding amount per unit time) is set. In addition to optimizing the discharge mechanism for realizing a small amount of discharge, and further improving the wettability followability when the gap is widened, the interval between droplets formed on the material to be coated is reduced (droplet density) Need to be increased).

  Note that the distance between the tip of the droplet discharge head and the substrate has an error of about 30 μm as a statistical addition value with respect to the set value due to variation factors such as substrate warpage, thickness variation, and morphology of the formed film. When the mother glass is larger than the 4th generation (730 mm x 920 mm), the coating error is suppressed over the entire surface of the substrate (inside and between lines), and a line pattern is formed. It is necessary to ensure a stable discharge state (gap margin) even at intervals of 100 μm or more.

  Furthermore, when a high-definition line pattern is formed in a bank using a droplet discharge head (plate) having a nozzle row composed of a plurality of nozzles, it is necessary to make the nozzle diameter and the pitch interval between adjacent nozzles fine. . Furthermore, when using an ink made of an organic solvent having a low boiling point, it is necessary to consider liquid clogging caused by concentration fluctuations due to solvent volatilization or a change in droplet discharge angle due to ink gelled material adhesion in the vicinity of each nozzle discharge port. These are important for reducing the formation of discontinuous lines (discontinuities) caused by the pitch deviation of the formed line pattern and the inability to match the pumping rate and stage feed speed of each nozzle.

  On the other hand, in the die coating method, lowering the pumping rate, that is, discharging a minute amount is effective for the above-described high-definition line patterning, and even when high concentration (high viscosity) ink is used for the coating solution. It is essential. When using high-density (high-viscosity) ink, the amount of ink discharged to fill the pixel area partitioned by the bank to obtain a predetermined dry film thickness is low (low-viscosity) by the amount of the increased active ingredient. This is because it is necessary to make the amount less than when using the ink.

  However, when discharging is performed from a small-diameter nozzle by pneumatic control using a dispenser or the like, there is a limit to discharging a very small amount due to the influence of liquid discharge resistance. Furthermore, it also acts disadvantageously from the viewpoint of ejection stability and film thickness stability.

  In general, as an ideal liquid feeding state in a closed system for stable discharge and quantitative discharge, it is necessary for the coating liquid bead to form a streamline in accordance with Bernoulli's theorem, and the streamline does not cause flow velocity turbulence Must be laminar. Further, as a condition that the streamline is a laminar flow, the Reynolds number defined by the correlation among the nozzle inner diameter, the flow velocity, the fluid density, and the fluid viscosity must be a critical Reynolds number (2310) or less. It is indispensable to create a state close to this in order to perform stable discharge and quantitative discharge.

  In order to perform line pattern formation by three-color coating by the die coating method, it is necessary to provide a unit (hereinafter referred to as a droplet discharge unit) composed of a manifold and a nozzle plate for each material. In addition, when a microcavity structure is used in which the film thickness is selected so that the optical path length between the cathode and anode matches the EL spectral peak wavelength of each color, the rheological properties and thixotropy that are different for each ink are taken into consideration, and A mechanism for ejecting ink while controlling the nozzle ejection resistance to obtain a predetermined dry film thickness is essential.

  The microcavity structure uses a semi-transmissive film for the cathode, and the externally emitted light by causing multiple reflection interference between the cathode semi-transmissive film and the anode (reflective film) with light having a wavelength matching the optical path length between the electrodes. In this structure, the EL spectrum is steep and the color purity is improved.

  An object of the present invention is to solve the above-mentioned problems of the prior art, and to reduce a film thickness unevenness (coating unevenness), a line defect, etc. An object of the present invention is to provide a method for manufacturing an organic EL element in which an element forming material is patterned by a droplet discharge method.

  In order to achieve the above object, according to a first aspect of the present invention, a plurality of nozzles are arranged in a first direction and on the same straight line to form a first nozzle group, and a first nozzle perpendicular to the first direction is formed. A plurality of first nozzle groups are juxtaposed in the direction of 2, and the hole diameters of the nozzles arranged in the second direction are set different from each other. By disposing a plurality of nozzles on a straight line instead of a single nozzle, when liquid droplets are ejected intermittently from the nozzles, liquid droplets are ejected from a plurality of nozzles having different hole diameters, so that the liquid in the line The droplet interval can be narrowed, and each droplet can be wetted and spread instantaneously in a wet state, and can be diffused, and does not cause an increase in concentration at the droplet junction, that is, film thickness unevenness (coating unevenness) or line Reduce the occurrence of defects Possible to become.

  According to a second aspect of the present invention, in the liquid droplet ejection device according to the first aspect, an edge is provided at a liquid droplet ejection port portion of each nozzle. Can be suppressed.

  According to a third aspect of the present invention, in the liquid droplet ejection apparatus according to the first or second aspect, a groove for preventing liquid droplet wetting and spreading is provided between adjacent nozzles.

  According to a fourth aspect of the present invention, in the liquid droplet ejection apparatus according to any one of the first to third aspects, a nozzle partition wall for controlling liquid feeding from each nozzle is provided in a manifold filled with a liquid material. It is characterized in that a nozzle having an appropriate hole diameter can be used according to the viscosity of the liquid material to be used. By using this configuration, a nozzle having a different hole diameter can be used to change the ejection resistance, thereby changing the ink viscosity. It is possible to form a stable line pattern on the application target without depending on the above.

  According to a fifth aspect of the present invention, in the liquid droplet ejection device according to any one of the first to fourth aspects, the liquid droplet ejection unit comprising a plate provided with a manifold and a nozzle is operated at a vibration frequency of 1 kHz or more and 10 kHz or less. With this configuration, by operating the droplet discharge unit at a constant vibration frequency, the discharge amount per unit time of the droplet can be controlled, and the droplet formed on the coating material It is also possible to make the interval uniform and reduce. Further, the propagation of external vibration to the ink can suppress gelation and aggregation (phase separation) caused by a change in local concentration in the ink. Thereby, the discharge behavior at each nozzle is not affected by the ink fluctuation factors, and as a result, the process margin (dense viscosity margin) capable of forming a line can be greatly expanded.

  According to a sixth aspect of the present invention, there is provided a liquid droplet ejection method in which a liquid material is ejected from the nozzles of a liquid droplet ejection head having a plurality of nozzles, and the liquid material is applied in a line shape to an application target. The plurality of nozzles are arranged on the same straight line with respect to the forming direction, and defects in line formation by the nozzle being applied are repaired by other nozzles. By arranging a plurality of nozzles on a straight line instead of one nozzle, it is possible to repair while discharging shape defects such as line breakage caused by wetting spread inhibition by the base form and imbalance between pumping rate and stage feed speed It becomes possible.

  According to a seventh aspect of the present invention, in the liquid droplet ejection method according to the sixth aspect, the liquid material ejection failure at the nozzle during coating is supplemented by ejection from another nozzle. The liquid clogging phenomenon (adhesion of the inner wall of the ink gelled product) accompanying the increase in the ink concentration due to the ink can be complemented by the ejection by other nozzles.

  According to an eighth aspect of the present invention, in the droplet discharge method according to the sixth or seventh aspect, the liquid material partition wall is provided in the manifold, and the different liquid materials partitioned by the liquid material partition wall are disposed in the plurality of nozzles 1. Continuous patterning is performed by repeated discharge, and this method enables continuous patterning by stable discharge of various liquid materials.

  According to a ninth aspect of the present invention, in the liquid droplet ejection method according to the eighth aspect, the different liquid materials are inks of RGB colors, and by this method, ejection amount control and stable ejection are performed for each color ink. Can be achieved.

  The invention according to claim 10 is characterized in that, in the droplet discharge method according to any one of claims 6 to 9, the viscosity of the liquid material used is 10 mPa · s or more and 100 mPa · s or less, In this range, it is possible to form a good line with an appropriate viscosity.

  The invention according to claim 11 includes a partition portion formed on the base material on which the first electrode is formed, and includes at least an organic light emitting layer and a second electrode in a region surrounded by the partition portion, and between the electrodes. In the manufacturing method of the organic EL element which makes the said organic light emitting layer light-emit by sending an electric current, the organic EL element formation material is a droplet discharge apparatus of any one of Claims 1-5, or any one of Claims 6-10. Line patterning is performed by the droplet discharge method according to claim 1, and by this method, the line patterning of the organic EL element forming material is improved by using the apparatus or the method capable of controlling discharge amount and stable discharge. Is possible.

  The invention according to claim 12 includes a partition part formed on a base material on which a reflective electrode is formed, and includes at least an organic light emitting layer and a transparent electrode in a region surrounded by the partition part, and a current is supplied between the two electrodes. In the manufacturing method of the top emission type organic EL element which makes the said organic light emitting layer light-emit by flowing, an organic EL element formation material is a droplet discharge device of any one of Claims 1-5, or Claims 6-10. Line patterning is performed by the droplet discharge method according to any one of the above, and by using the apparatus or the method capable of discharge amount control and stable discharge by this method, a top emission type organic EL element is formed. Good line patterning of the material becomes possible.

  The invention according to claim 13 is the method for producing an organic EL element according to claim 11 or 12, wherein the organic EL element forming material is dissolved or dispersed in a solvent to form an ink, and the ink is used. A step of forming an organic light emitting layer on a substrate by a droplet coating apparatus according to any one of claims 1 to 5 or a die coating method using the droplet ejection method according to any one of claims 6 to 10. This method makes it possible to form an organic light emitting layer without depending on the ink physical properties.

  According to the present invention, when a plurality of nozzles are arranged on the same straight line instead of one nozzle with respect to the line formation direction, a plurality of nozzles having different hole diameters are ejected when the droplets are ejected intermittently. By ejecting droplets from the nozzle, the interval between droplets in the line can be narrowed, and each droplet can be instantly wetted and spread in a wet state, and can be diffused, resulting in an increase in the concentration of the droplet junction. In other words, it is possible to reduce film thickness unevenness (coating unevenness) and line defect generation, and shape such as line breakage caused by wetting spread inhibition by the base form and imbalance between pumping rate and stage feed speed. It is also possible to repair while discharging defects.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1A is a schematic configuration diagram illustrating the entire bottom surface on the ejection side (lip side) of a droplet ejection head for ejecting ink to a pixel region surrounded by a bank according to an embodiment of the present invention. FIG. 2B is a sectional view taken along the line BB ′ in the droplet discharge head shown in FIG. 1A, FIG. 2 is a sectional view taken along the line AA ′ in the droplet discharge head shown in FIG. FIG. 4 is a schematic configuration diagram for explaining ink ejection onto a substrate in the droplet ejection head of this embodiment.

  In FIG. 1, 1 is an ink supply port for red light emitting polymer ink (R-LEP), 2 is an ink supply port for green light emitting polymer ink (G-LEP), and 3 is a blue light emitting polymer ink (B- LEP) ink supply port, 4 is an ink supply port (IL ink), and 5 is a nozzle row having a plurality of droplet discharge ports (nozzles) 5a to 5c (three nozzles are shown in this example). 5a is a droplet discharge port of a nozzle having a minimum hole diameter around which an edge 5a 'is formed, and 5b is a droplet discharge port of a nozzle having an intermediate hole diameter around which an edge 5b' is formed. This is a droplet discharge port of the nozzle having the maximum hole diameter in which the edge 5c ′ is formed. Further, 9 is an ink chamber partition wall, 10 is a nozzle partition wall, 11 is a groove provided for preventing droplet wetting and spreading (preventing discharge liquid interference), and 12 is a nozzle plate (droplet discharge head).

  In FIG. 1, Y is a first direction in which droplet discharge ports with the same hole diameter are formed in a straight line, and X is a direction perpendicular to the first direction Y (droplet discharge with different hole diameters). N1 is a first nozzle group (one line is shown by a broken line in the drawing), and NT is a plurality of first nozzles. A nozzle group (a set of first nozzle groups N1 formed in the second direction X) is shown.

  In the present embodiment, the droplet discharge ports 5a to 5c are changed in size so that the discharge resistance can be controlled according to the ink viscosity. In the die coating (die nozzle) method, the liquid discharge amount is generally inversely proportional to the fourth power of the hole diameter. Therefore, the hole diameter and the ink viscosity are set, and the bank as a partition portion in the organic EL element or the like to be manufactured is used. When ink is ejected to the pixel area partitioned by, it is necessary to perform ejection amount control according to the bank interval so that ink overflow and run-up do not occur. According to the configuration of the present embodiment, by appropriately selecting the droplet discharge ports 5a to 5c having different diameters, it is possible to change the discharge resistance as necessary, so that the ink viscosity is not affected. This is effective for controlling the discharge amount.

  An ink in which an organic EL element forming material is dissolved or dispersed in a solvent suppresses a change in ink thick viscosity due to solvent volatilization and improves the compatibility of the ink base material. Therefore, particularly in a wet method such as a die coating method. In general, a solvent having a high boiling point is employed.

  In addition, in coating, a coating film of about several μm is uniformly wetted and spread on the substrate, and after drying, a thin film of several nm is formed on the substrate to be coated. The viscosity of the ink using is about 10 to 100 mPa · s. When the ink viscosity is 10 mPa · s or less, the ejection resistance is low, and the wetting and spreading in the line width direction during droplet ejection is large. Therefore, when ink is ejected to a region partitioned by a bank such as an organic EL element, ink overflow occurs. In addition, when the ink viscosity is 100 mPa · s or more, the ejection resistance increases, and unless an extremely high pressure is applied, droplets are not ejected, and the ejection form becomes discontinuous, causing an increase in film thickness variation.

  On the other hand, such inks tend to adsorb moisture in the atmosphere, and further, due to hydrolysis of the ink base, molecular weight is lowered and viscosity changes are likely to occur. For this reason, the configuration of the present embodiment is effective for dealing with changes in ink viscosity.

  Further, a valley-shaped groove 11 for preventing droplet wetting and spreading (interference) as shown in FIG. 1B is provided between adjacent nozzle rows 5. The cross-sectional shape of the valley shape is an isosceles triangle having a bottom angle of 60 to 120 °, and the depth is 300 to 500 μm.

  In addition, the cross-sectional shape of the groove 11 for preventing droplet wetting and spreading (interference) is not only a valley shape as in this example, but also a round shape and a square shape because of an increase in contact area with ink and ease of processing. Also good. As a result, the droplets discharged from the nozzle holes do not interfere with each other, and the discharge direction (angle) can be made uniform.

  In FIG. 2, 13 is a liquid feeding direction, 14 is an upper manifold having a coat hanger structure, 15 is a pressure opening, 16 is a manifold joint, and 17 to 20 are ink (R-LEP) and ink ( G-LEP), ink (B-LEP), and ink (IL).

  In the nozzle plate 12, droplet discharge ports 5a to 5c, which are nozzles having different hole diameters, are arranged in parallel on the same straight line in order of decreasing hole diameter (5a <5b <5c) with respect to the stage feed direction. A plurality of nozzle rows 5 are arranged in parallel to the stage feed direction. As a result, after a droplet is ejected from a nozzle with a small hole diameter and before the next droplet is formed, the droplet is ejected from a nozzle with a larger hole diameter, thereby continuously from discontinuous. Transition to the proper discharge mode. In order to make it easy to control the liquid discharge amount, the nozzle arrangement order is set so that the first nozzle hole diameter is set small (discharge resistance is large) on the substrate, and the hole diameter is set in order of discharge from the second to the third. Is set to increase (discharge resistance is small).

  The interval (pitch) between the adjacent nozzle rows 5 corresponds to the bank interval of the organic EL elements, and the number of nozzle rows 5 arranged is the pixel of the panel manufactured by this droplet discharge method. It conforms to the format. Further, in order to suppress the liquid droplet wetting and spreading to the lip (discharge side bottom surface), each liquid droplet discharge port 5a to 5c has an angle of 45 ° with respect to the liquid flow path portion and an outer periphery that is twice the nozzle radius. Edges 5a ′ to 5c ′ of a size to be formed are provided.

  Further, the upper manifold 14 has a coat hanger structure for adjusting the ink viscosity, balancing pressure circulation inside the manifold, that is, suppressing the influence of Karman vortices (rows) generated in the dead water region inside the manifold. It has become. The coat hanger structure is an internal shape in which the upper and lower ends of the manifold (both end faces in the BB ′ direction) are formed with surfaces having an angle of 60 ° with respect to the vertical direction and an angle of 30 ° with respect to the horizontal direction. That is.

  Ink supply to the droplet discharge unit including the nozzle plate 12 and the upper manifold 14 is performed from the ink supply ports 1 to 4 shown in FIG. 1 provided in the lower part, and the supplied inks having different physical properties are mixed. The ink chamber partition walls 9 are separated so as not to match. Further, the upper part of each nozzle partition wall 10 is subjected to water repellent treatment such as fluororesin coating, and the ink is filled in the entire droplet discharge ports 5a to 5c through the ink supply ports 1 to 4 or independently. can do. Thereby, the nozzle hole diameter can be selected according to the viscosity of the ink used, and it becomes easy to match the ejection resistance and the fluid viscosity.

  As shown in FIG. 3, the upper part of the droplet discharge unit is covered with an upper plate 21 of the manifold, and a circular opening 15 for ink discharge pressurization is provided at the center of the droplet discharge unit so that the dispenser pneumatic pressure adjusting pipe 22 is provided. Connected and applies pressure in the pressing direction 23 indicated by the arrow. Further, the nozzle rows 5 are arranged inside the ink chamber partition wall 9 so that the nozzle rows 5 are arranged in parallel to the line forming direction.

  In FIG. 4, 24 is a substrate stage on which a substrate 25 is placed, 26 is an ink supply pipe, 27 is a micropore filter, 28 is a syringe, 29 is a dispenser pneumatic pipe fixing jig, and 30 is a pressure adjusting three-way. A valve, 31 is a pressure leak direction, and 32 is a dispenser controller.

  As shown in FIG. 4, the pressurization in the pressurizing direction 23 for ink ejection is performed by the pressure set by the dispenser controller 32 being propagated into the manifold via the dispenser pneumatic piping 22. Is called. In addition, a three-way valve 30 for pressurization adjustment is provided between the dispenser controller 32 and the droplet discharge unit. Even at a pressure outside the dispenser control range, a minute pressure is generated by leaking the pressure through the valve. It can be added.

  Ink supply is performed through the ink supply pipe 26 after removing impurities such as ink gelation by the micropore filter 27 with the syringe 28. Further, each of the organic EL element forming materials of RGB colors separated by the ink chamber partition wall 9 and the nozzle partition wall 10 with respect to the substrate 25 placed on the substrate stage 24 at a position facing the nozzle plate 12. Inks 17 to 19 are ejected intermittently or continuously to form a line pattern. This makes it possible to perform RGB continuous patterning without performing alignment by a single discharge, and other functional organic thin film materials such as a hole injection material can be filled without replacing the droplet discharge unit. Multi-layer film formation is also possible. Further, the droplet discharge unit can be operated at a constant vibration frequency. The vibration frequency can be controlled in the range of 1 to 10 kHz according to the stage feed speed.

  As a specific example, when the vibration frequency is 1 kHz and the stage feed speed is 150 mm / s, the stage moving distance per vibration, that is, the droplet length is 150 μm. This is, for example, a panel size of 5 inches and a pixel format VGA (640 It substantially matches the length of the pixel area (cell) surrounded by the bank at (× 480 dots).

  In addition, when the vibration frequency is 10 kHz and the stage feed speed is 150 mm / s, the stage moving distance per vibration is 15 μm, and it is possible to manufacture a higher-definition pixel format panel with the same panel size. As the pixel format of the panel becomes higher definition, it is necessary to reduce the cell length, and accordingly, it is necessary to finely control the droplet discharge amount, but by increasing the vibration frequency and stage feed speed This suggests that it is possible to deal with droplet discharge to cells in the pixel format FHD (1920 × 1084 dots).

  On the other hand, a large panel having a panel size of 40 inches or more is 42 inches, and a cell length of FHD is about 480 μm. Therefore, it is possible to control the discharge amount into the cell within the vibration frequency control range of this embodiment.

  As described above, in the present embodiment, the nozzle plate 12 constituting the droplet discharge head having a nozzle row composed of a plurality of nozzles has a plurality of nozzles (droplet discharge ports 5a) instead of one nozzle in the line formation direction. ˜5c) are arranged on the same straight line, the coating liquid bead is not formed between the tip of the droplet discharge head and the coating target, and the droplets are intermittently formed on the substrate which is the coating target at regular intervals. Even in the discharge form to be formed, the droplet density in the formation line can be increased.

  In addition, when the interval between the tip of the droplet discharge head and the substrate is enlarged, the film is formed in and between the formed line patterns by realizing intermittent discharge at intervals where the droplets can spread and spread each other. Defects such as uneven thickness (coating unevenness) and breaks can be suppressed.

  Furthermore, by arranging a plurality of nozzles on the same straight line, it is possible to repair shape defects such as line breakage caused by wetting spread inhibition due to the base form and imbalance between pumping rate and stage feed speed while discharging droplets. Thus, the clogging phenomenon (attachment of the inner wall of the ink gel product) accompanying the increase in the ink concentration due to the solvent volatilization can be complemented by the ejection by other nozzles.

  In addition, by operating the droplet discharge unit at a constant vibration frequency, the discharge amount of the droplet per unit time can be controlled, and the interval between droplets formed on the application target can be made uniform and reduced. . In addition, since external vibration is propagated to the ink, gelled product formation and aggregation (phase separation) caused by a local concentration change in the ink can be suppressed. Thereby, the discharge behavior at each nozzle is not affected by the ink fluctuation factors, and as a result, the process margin (dense viscosity margin) capable of forming a line can be greatly expanded.

  On the other hand, by changing the ejection resistance by changing the diameters of the nozzle rows, a stable line pattern can be formed on the application target without depending on the ink viscosity. Although the organic EL element forming material has a similar basic skeleton for each RGB, the glass transition point (Tg) is different because the structure of the spacer structure and the functional part connecting the main chain and the functional part (substituent) is different. The molecular weight of the drug substance varies depending on the monomer concentration and the amount of polymerization initiator. This changes the rheology and thixotropy of each color ink. Therefore, when a microcavity structure in which the film thickness of the light emitting layer in each color is controlled so as to match the optical path length between the electrodes is employed, according to the configuration of this embodiment, the ejection amount can be controlled and stabilized without depending on the ink physical properties. This is advantageous in that discharge can be achieved.

(Example)
As an example, a taper-shaped bank having a pitch of 60 μm, a bank width of 40 μm, and a bank height of 1 μm was formed by photolithography using a glass substrate having a thickness of 0.7 mm as a substrate and a polyimide material on the substrate.

  Next, a green organic EL element forming material made of polyfluorene (PF) was used, and this green organic EL element forming material was prepared in a ratio of 50:50, 90:10 with cyclohexylbenzene or methoxytoluene. The ink was dissolved in a mixed solvent to obtain an ink having a solid content ratio of 1.0, 1.5, and 2.0. The viscosity of each ink is 15 mPa · s when the solid content ratio is 1.0, 25 mPa · s when the solid content ratio is 1.5, and 40 mPa · s when the solid content ratio is 2.0.

  In the nozzle plate, each nozzle having a hole diameter of 30, 32, 34 μm and a liquid flow path portion length of 50 μm is arranged at a pitch of 0.3 mm in the line forming direction as one nozzle row. Using the 30-hole nozzle plate arranged side by side, ink was filled in the pixel area partitioned by the bank by the droplet discharge device and method of this embodiment, and an organic light emitting layer was formed in a striped line pattern.

  FIG. 5 is a cross-sectional view for explaining the structure of an example of a top emission type organic EL element manufactured by the droplet applying apparatus and method of the present embodiment, 33 is a glass substrate, 34 is a TFT, 35 is a planarizing film, 36 is an auxiliary wiring, 37 is a bank, 38 is a reflective anode (Ag-Alloy), 39 is a hole injection layer, 40 is an interlayer (electron blocking layer), 41 is an organic light emitting layer (RGB), and 42 is an electron injection layer. , 43 is a transparent electrode, 44 is a thin film sealing layer (SiNx), 45 is a resin sealing layer, 46 is a black matrix (CF), 47 is a color resist (RGB), and 48 is a glass substrate.

  Stripe lines formed between banks using the droplet discharge apparatus and discharge method of the present embodiment are provided between edges 5a ′ to 5c ′ provided in the droplet discharge ports 5a to 5c and between adjacent nozzle rows 5. The discharged liquid interference preventing grooves 11 formed in the bank do not interfere with each other and are formed at equal intervals in the bank. Therefore, each stripe line was measured using a stylus step meter. However, the film thickness variation obtained by scanning in the lateral direction at a pitch of 2 mm in the longitudinal direction is 5 with respect to the film thickness center value within the formation line (measurement number of 20 points) and between lines (measurement number of 30 points). % Or less. This is because the droplets formed on the object to be coated are formed between the banks intermittently with a fine and constant pitch, and the droplets are wet and spread instantly in a wet state, thereby obtaining uniform film quality. It is suggested that

  In addition, according to the present embodiment, line defects (discontinuities) that occur when the interval (coating gap) between the tip of the droplet discharge head and the application target is increased can also cause a plurality of nozzles to be aligned on the line forming direction. It was possible to repair it by placing it in a continuous discharge. As a result, the gap in which lines can be formed between banks has been greatly expanded.

  Specifically, when ink is ejected to the pixel area partitioned by the bank at a stage feed speed of 150 mm / s using the above-mentioned ink of each solid content ratio made of PF, stable application can be performed without line defects. The gap is about 35 μm for each ink, but by using this droplet discharge device and discharge method, the gap that can be stably applied is the largest (solid content ratio 1.5 ink) up to 60 μm. Enlarged. This suggests that stable coating is possible without being affected by variations in substrate thickness and underlying film morphology that become apparent as the substrate size increases.

  In addition, ink non-ejection occurred locally in the porous nozzle due to the adhesion of the ink gelled product to the nozzle tip ejection part due to solvent volatilization, but a plurality of nozzles linearly with respect to the line formation direction as in this embodiment. By providing the ink, it becomes possible to supplement the ink supply to the substrate by the ejection by other nozzles, and the ejection stability and reproducibility in forming the line pattern are greatly improved.

  The droplet discharge apparatus and the droplet discharge method of the present invention are not limited to organic EL device fabrication, but can be used for various display devices such as PDP and FED (Field Emission Display), It can also be applied to a color filter manufacturing apparatus. In addition to the case where a coating film is formed on a substrate for a display device, a liquid coating solution is supplied in a single-wafer method, for example, in the semiconductor manufacturing field such as resist coating, and in the optical filter manufacturing field such as UV absorption layer coating. It is effective when it is applied uniformly to the surface to be coated.

(A) is a schematic configuration diagram showing the entire bottom surface on the ejection side (lip side) of a droplet ejection head for ejecting ink to a pixel region surrounded by a bank according to an embodiment of the present invention; BB 'sectional drawing in the droplet discharge head shown to a) A-A 'sectional view of the droplet discharge head shown in FIG. The perspective view which shows the internal structure of the droplet discharge head of this embodiment. Schematic configuration diagram for explaining ink ejection onto a substrate in the droplet ejection head of the present embodiment Sectional drawing for structure description of an example of the top emission type organic EL element manufactured with the apparatus and method which concerns on this invention Sectional drawing which shows schematic structure of the conventional organic electroluminescent display Schematic configuration diagram of a relief printing apparatus used in the production of conventional printed matter Explanatory drawing which shows the positional relationship of the fountain die and the backup roll in the conventional die coater type coating device

Explanation of symbols

1 to 4 Ink supply port 5 Nozzle rows 5a to 5c Droplet ejection ports 5a 'to 5c' Edge 9 Ink chamber partition wall 10 Nozzle partition wall 11 Droplet wetting and spreading groove 12 Nozzle plate 13 Liquid feeding direction 14 Coat hanger structure Upper manifold 15 Pressure opening 16 Manifold joints 17 to 20 Ink 21 Manifold upper plate 22 Dispenser air pressure adjustment piping 23 Pressure direction 24 Substrate stage 25 Substrate 26 Ink supply piping 27 Micropore filter 28 Syringe 29 Dispenser air pressure Piping fixture 30 Three-way valve for pressure adjustment 31 Pressure leak direction 32 Dispenser controller 33 Glass substrate 34 TFT
35 Flattening film 36 Auxiliary wiring 37 Bank 38 Reflective anode 39 Hole injection layer 40 Interlayer 41 Organic light emitting layer 42 Electron injection layer 43 Transparent electrode 44 Thin film sealing layer 45 Resin sealing layer 46 Black matrix 47 Color resist 48 Glass substrate Y 1st direction X 2nd direction N1 1st nozzle group NT Several 1st nozzle group

Claims (13)

  A first nozzle group is formed by arranging a plurality of nozzles in a first direction and on the same straight line, and a plurality of first nozzle groups are arranged in parallel in a second direction perpendicular to the first direction, A droplet discharge device, wherein each nozzle diameter arranged in the second direction is set to be different.   2. The droplet discharge device according to claim 1, wherein an edge is provided at a droplet discharge port portion of each nozzle.   3. The droplet discharge device according to claim 1, wherein a groove for preventing droplet wetting and spreading is provided between the adjacent nozzles.   A nozzle partition wall for controlling liquid feeding from each nozzle is provided in the manifold filled with the liquid material, and the nozzle having an appropriate hole diameter can be used according to the viscosity of the liquid material to be used. The droplet discharge device according to claim 1.   5. The droplet discharge device according to claim 1, wherein a droplet discharge unit including a plate provided with the manifold and the nozzle is operable at a vibration frequency of 1 kHz or more and 10 kHz or less. In a droplet discharge method of discharging a liquid material from the nozzle of a droplet discharge head having a plurality of nozzles and applying the liquid material in a line shape to an application target,
A droplet discharge method comprising: arranging a plurality of nozzles on the same straight line in a line forming direction, and repairing a defect in line formation by a nozzle being applied by another nozzle.   7. The droplet discharge method according to claim 6, wherein the liquid discharge failure in the nozzle during application is complemented by discharge from another nozzle.   8. The liquid material partition wall is provided in the manifold, and different liquid materials partitioned by the liquid material partition wall are continuously patterned by one-time discharge of the plurality of nozzles. Droplet ejection method.   9. The droplet discharge method according to claim 8, wherein the different liquid materials are inks of RGB colors.   10. The droplet discharge method according to claim 6, wherein the liquid used has a viscosity of 10 mPa · s or more and 100 mPa · s or less. A partition is formed on the base material on which the first electrode is formed, and at least an organic light-emitting layer and a second electrode are provided in a region surrounded by the partition, and the organic light-emitting layer is caused to flow by passing a current between the electrodes. In the manufacturing method of the organic EL element that emits light,
The organic EL element forming material is line-patterned by the droplet discharge device according to any one of claims 1 to 5 or the droplet discharge method according to any one of claims 6 to 10. Manufacturing method. A partition is formed on the base material on which the reflective electrode is formed, and at least an organic light-emitting layer and a transparent electrode are provided in a region surrounded by the partition, and the organic light-emitting layer emits light by passing a current between the electrodes. In the manufacturing method of the top emission type organic EL element to be made,
A top emission type, wherein the organic EL element forming material is line-patterned by the droplet discharge device according to any one of claims 1 to 5 or the droplet discharge method according to any one of claims 6 to 10. The manufacturing method of organic EL element.   The step of dissolving or dispersing the organic EL element forming material in a solvent to obtain an ink, and using the ink, the droplet discharge device according to any one of claims 1 to 5, or the claim 6 to any one of claims 10 to 10. The method for producing an organic EL element according to claim 11, further comprising a step of forming an organic light emitting layer on a substrate by a die coating method using the droplet discharge method described in claim 11.

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