JP2006228496A - Droplet discharge apparatus and method as well as manufacturing method of organic electroluminescent apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a reliable droplet discharge apparatus by realizing stable discharge of dropletS with broad selections of materials and solvents after coping with the increase of viscosity of ink by ageing. <P>SOLUTION: The droplet discharge apparatus has a discharge head 100 which will discharge a liquid material on a specific area of the discharge object W, a storage means 500 for keeping the above mentioned liquid material temporarily, a transfer means 400 for transferring the liquid material to the discharge head, a heating means 320(330) placed either on the storage means 500 or the transfer means 400 to heat the liquid material, and a cooling means 340 placed nearer the discharge head 100 than the heating means 320(330). <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a droplet discharge device, a droplet discharge method, and a method for manufacturing an organic EL device (organic electroluminescence device).

In recent years, a technique for patterning various materials by an ink jet method (droplet discharge method) using an ink jet device (droplet discharge device) has attracted attention. In particular, an organic EL (electroluminescence) device manufacturing method for patterning a luminescent material by converting an organic luminescent material into an ink and selectively ejecting the ink (liquid material) onto a substrate by the above-described inkjet method is disclosed in, for example, Patent Document 1 or Patent Document 2.
Japanese Patent Laid-Open No. 11-54270 JP 2004-1227897 A

As an important parameter when patterning is performed by selective ejection using such an ink jet method, the viscosity of the ink can be cited. When discharging by the ink jet method, the discharge conditions such as power and time for driving the discharge head are optimized in accordance with characteristics such as viscosity and elastic modulus of the ink to be used. Here, if the ink viscosity changes, the ink droplet ejection weight may fluctuate, and a desired film thickness may not be obtained, or ejection itself may be impossible.
Further, in order to obtain a uniform film thickness, the drying conditions (temperature, pressure, etc.) of the ink ejected by the ink jet method are also optimized. However, when the viscosity of the ink changes, the distribution of film thickness at the time of drying is also affected, and it becomes difficult to stably obtain a uniform film thickness.
On the other hand, when the material used for the functional layer of the organic EL device is converted to ink, the viscosity changes with time after the ink preparation often occurs. Such a change in ink viscosity over time causes a change in the thickness of the formed organic functional layer, which makes it difficult to stably form an organic EL device by an ink jet method. Furthermore, depending on the combination of the material used (light emitting material, hole injection material, interlayer material, etc.) and the solvent, there is a significant change in ink viscosity over time, making it difficult to apply to film formation by the ink jet method.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to expand the selection range of materials and solvents by coping with the increase in viscosity over time as described above. It is another object of the present invention to provide a droplet discharge apparatus that realizes stable discharge and has high process reproducibility, and a droplet discharge method. Furthermore, it aims at providing the manufacturing method which can manufacture the organic EL apparatus of a favorable characteristic stably.

  In order to solve the above-described problems, a droplet discharge device of the present invention includes a discharge head that discharges a liquid material to a predetermined area of an object, a storage unit that stores the liquid material, and a liquid material that is stored in the storage unit. In at least one of the transfer means for transferring to the discharge head, the storage means or the transfer means, the heating means for heating the liquid material, the discharge head side or the discharge head from the heating means of the transfer means And cooling means for cooling the liquid state.

  According to such a droplet discharge device, even if thickening occurs during storage of the liquid material, the liquid material is heated before being discharged from the head by heating the liquid material by the heating means in the storage means or the transfer means. It is possible to return the viscosity of the liquid to the original state (the state at the start of storage), and furthermore, the heated liquid material is cooled before discharge, so that stable discharge can be performed. Specifically, when the liquid material is discharged while being heated, the solvent tends to dry near the discharge port (nozzle) provided in the discharge head, which may cause discharge failure. By cooling the body, drying of the solvent is suppressed, and the ejection failure is prevented or suppressed. Further, particularly by actively cooling, the path length of the transfer means can be shortened compared to the case of natural heat dissipation, and the amount of liquid material to be filled in the droplet discharge device is reduced. In addition, the frequency characteristic can be improved such that the resistance of the path is reduced and the supply capability of the liquid material is stabilized. Furthermore, in the present invention, even when a liquid material that thickens with time is discharged, the discharge stability of the liquid material can be suitably improved by providing the heating means and the cooling means.

  In order to solve the above problems, a droplet discharge method of the present invention includes a step of discharging a liquid material from a discharge head to a predetermined region of an object, a step of storing the liquid material in a storage unit, A step of transferring the liquid material from the storage means to the discharge head, and in the step of storing or transferring, the liquid material is cooled and then cooled before the step of discharging. Features.

  According to such a droplet discharge method, even if thickening occurs during storage of the liquid, the liquid is heated during storage or transfer, so that the viscosity of the liquid is restored to the original state ( It is possible to return to the state at the start of storage), and the heated liquid is cooled before discharge, so that stable discharge can be performed. In particular, even when a liquid material that thickens with time is discharged, the discharge stability of the liquid material can be suitably improved by heating during storage or transfer and cooling immediately before discharge.

  The heating temperature can be set to be equal to or lower than the glass transition temperature of the solute contained in the liquid. This is because if the heating is performed at a temperature exceeding the glass transition temperature, the material characteristics of the solute are changed, which may cause a problem that desired film characteristics cannot be obtained. In addition, it cannot be overemphasized that the lower limit of a heating is the temperature exceeding the storage temperature (for example, room temperature) of a liquid.

  The heating time may be 5 minutes to 30 minutes. If the heating time is less than 5 minutes, the effect of reducing the viscosity may not be sufficiently obtained. On the other hand, if the heating time exceeds 30 minutes, the heating will be more than necessary and the material will be altered. There is a case.

  Further, after the heating, the heated liquid material can be discharged from the discharge head within 24 hours. The viscosity and elastic modulus of the ink are stable with almost no change for about 24 hours after heating, and a uniform film can be stably formed by controlling discharge and drying during that time. it can.

  Next, in order to solve the above-described problem, a method for manufacturing an organic EL device according to the present invention is a method for manufacturing an organic EL device having an organic EL layer between a pair of electrodes. It includes a step of forming a film using the above-described droplet discharge method. With such a manufacturing method, a highly reliable organic EL layer can be constructed, and as a result, a high-quality organic EL device can be provided.

(Overall configuration of inkjet device (droplet discharge device))
FIG. 1 is a schematic perspective view showing the overall configuration of an ink jet apparatus which is an embodiment of a droplet discharge apparatus of the present invention.
As shown in FIG. 1, the inkjet apparatus 1 of the present embodiment includes an ejection head group 100, an X direction drive motor 2, an X direction drive shaft 4, a Y direction drive motor 3, a Y direction guide shaft 5, a control device 6, and a stage. 7, a cleaning mechanism 8, and a base 9.

  The discharge head group 100 includes a plurality of discharge heads, and ink supplied from a tank (storage means) 500 in which ink (liquid material) is stored via a supply pipe (transfer means) 400 is supplied from each discharge head. It is designed to discharge. The supply pipe 400 is a tubular member through which ink to be ejected can flow, and means a set of liquid supply paths corresponding to each ejection head. Here, in the inkjet apparatus 1 of the present embodiment, the tank 500 and the supply pipe 400 include a first heater 320 and a second heater 330 for heating ink inside the tank 500 and the supply pipe 400. Each is provided. Further, the supply pipe 400 is provided with a cooling device 340 closer to the discharge head group 100 than the second heater 330.

  The stage 7 is for placing a substrate (ejection target) W on which ink is ejected from the ejection head group 100, and has a mechanism for fixing the substrate W at a predetermined reference position.

  The X-direction drive shaft 4 is composed of a ball screw or the like, and the X-direction drive motor 2 is connected to the end portion. The X direction drive motor 2 is a stepping motor or the like, and rotates the X direction drive shaft 4 when a drive signal in the X axis direction is supplied from the control device 6. When the X-direction drive shaft 4 rotates, the ejection head group 100 moves on the X-direction drive shaft 4 in the X direction.

  The Y-direction guide shaft 5 is also composed of a ball screw or the like, but is arranged at a predetermined position on the base 9. A stage 7 is disposed on the Y-direction guide shaft 5, and the stage 7 includes a Y-direction drive motor 3. The Y-direction drive motor 3 is a stepping motor or the like. When a drive signal in the Y-axis direction is supplied from the control device 6, the stage 7 moves in the Y direction while being guided by the Y-direction guide shaft 5. Thus, the ejection head group 100 can be moved to an arbitrary location on the substrate W by performing driving in the X-axis direction and driving in the Y-axis direction.

  As shown in FIG. 2, the control device 6 includes a drive signal control device 31 that supplies a signal for controlling the ejection of ink to the ejection head group 100. The control device 6 also includes a head position control device 32 that supplies a signal for controlling the positional relationship between the ejection head group 100 and the stage 7 to the X-direction drive motor 2 and the Y-direction drive motor 3. Moreover, the control apparatus 6 is provided with the temperature control part 300 shown in below-mentioned FIG. Based on the control by these control devices, the ejection head group 100 and the substrate W move relative to each other, and predetermined drawing is realized based on the relative movement.

(Configuration for temperature control)
As described above, the heaters 320 and 330 are disposed in the tank 500 and the supply pipe 400, and further, the cooling device 340 is disposed in the middle of the supply pipe 400 and closer to the discharge head group 100 than the heater 330. ing. FIG. 3 is a block diagram illustrating a configuration for temperature control of the inkjet apparatus 1. As shown in FIG. 3, the tank 500 is provided with a first heater 320 and a first temperature sensor 325, and the supply pipe 400 is provided with a second heater 330 and a second temperature sensor 335. Further, a cooling device 340 including a constant temperature circulation device is provided. In addition, although a heat insulating material etc. are arrange | positioned at each site | part, illustration is abbreviate | omitted in FIG.

  The temperature control unit 300 is provided in the control device 6 shown in FIG. 1, and the first temperature sensor 325 and the second temperature sensor 335 output the temperature monitoring results for the tank 500 and the supply pipe 400 to the temperature control unit 300. Is configured to do. And based on the temperature monitoring result of these temperature sensors 325 and 335, the temperature control part 300 controls the 1st heater 320 and the 2nd heater 330 separately. For this reason, in this embodiment, the temperature of the tank 500 and the supply pipe 400 can be independently controlled to a predetermined temperature. Further, the temperature control unit 300 may be provided with a timer so that the ink is heated again after a predetermined time has elapsed since the previous ink heating process.

  The second heater 330 may be provided in the entire supply pipe 400 or may be provided only in the vicinity of the discharge head group 100 of the supply pipe 400. Further, if a self-control type heater that heats to a certain temperature only by energization is used as the heating means, the temperature sensors 325 and 335 and the temperature control unit 300 can be omitted. Furthermore, a constant temperature circulation device as shown in FIG. 4 can be used as the heating means.

  FIG. 4 is a block diagram showing a schematic configuration of an example of a constant temperature circulation device. The constant temperature circulation device (chiller device) 50 in this case is provided with a heat exchanger for circulating the refrigerant instead of the heaters 320 and 330 in FIG. The constant-temperature circulation device 50 performs temperature control by cooling a refrigerant (for example, brine) taken out from a heat exchanger disposed in a temperature control target (not shown) by a refrigerator 51 and then heating the refrigerant by a heater 52. The refrigerant is supplied to the buffer tank 54, and the refrigerant is supplied from the buffer tank 54 to the temperature control target. And the temperature of the refrigerant | coolant discharged from the buffer tank 54 is detected by the temperature sensor 55, PID control etc. are performed based on setting temperature and detected temperature, a control signal is output, and the refrigerator 51 and the heater 52 are controlled. It is. By using such a chiller device, precise temperature control can be performed. In particular, when heating is performed at a relatively low temperature of about 60 ° C. to 80 ° C., temperature control with higher accuracy than that of the heater can be performed.

  On the other hand, the cooling device 340 is a device that cools the ink heated by the heater 330. When the heated ink is ejected while being heated, it tends to increase in viscosity and solidify due to drying in the vicinity of the nozzle openings 621 provided in the ejection head group 100, thereby causing unstable ejection and ejection failure. May occur. Therefore, in the present embodiment, the ink heated immediately before ejection is cooled (heat radiation) to near room temperature (for example, 20 ° C.) of 15 ° C. to 25 ° C. As the cooling device 340, in addition to the constant temperature circulation device 50 shown in FIG. 4, a constant temperature circulation device (chiller device) 342 as shown in FIG. 7 can be used. In the example of FIG. The supply pipe 400 is cooled via a heat medium 341 such as oil. Further, for example, as the cooling device 340, a cooling device provided with the radiation fins 345 shown in FIG. In this case, the ink can be controlled to room temperature with a simple configuration. Further, such heat radiation fins 345 can be disposed on the back side of the ejection head group 100, thereby reliably cooling the ink before ejection.

The inkjet apparatus 1 according to the present embodiment having the above-described configuration is an apparatus specialized for ink whose viscosity changes with time. That is, even if the viscosity of the ink stored in the tank 500 increases with time, the operation of the heater 320 provided in the tank 500 causes a predetermined temperature (here, the glass transition of the solute constituting the ink). Since the ink is heated to a temperature below 60 ° C., specifically 60 ° C. to 120 ° C. (specifically 80 ° C.), the viscosity of the ink can be returned to the original storage state, and stable ejection is performed. Will be able to. When heating the ink supply pipe while discharging, it is preferable to heat the ink so that the actual ink heating time is about 5 to 30 minutes in consideration of the moving speed of the ink in the supply pipe. .
The heating of the ink can be returned to the original viscosity when the ink was prepared by a shorter time as the temperature is higher, but the polymer material (light emitting material, hole injection / transport material, etc.) used as the solute If the temperature is higher than the glass transition temperature, the polymer material may be deteriorated, and desired characteristics may not be obtained. Since many polymer light-emitting materials have a glass transition of 150 ° C. to 250 ° C., it is desirable that the temperature be 120 ° C. or less in consideration of a margin. In addition, if the temperature is lower than 60 ° C., the effect of returning the ink to the original viscosity cannot be obtained, or the processing time until the effect is obtained becomes long, and it becomes difficult to maintain the operation rate of the ink jet apparatus.

Furthermore, since the heated ink is cooled to near room temperature before ejection, there is no increase in viscosity or solidification due to drying of the ink near the nozzle openings 621 provided in the ejection head group 100. As a result, problems such as clogging of the nozzle opening 621 are prevented or suppressed.
Further, since the ink heating means can be disposed at a position close to the ejection head by having the means for forcibly cooling, the amount of ink between the heating means and the ejection head can be reduced. Can do. Accordingly, the heat-treated ink can be ejected in a shorter elapsed time, and the ejection stability is improved. Further, the cooling device 340 may be arranged to cool the ejection head group 100 as well. As a result, the amount of ink existing between the heating means and the ejection head can be further reduced, and the temperature of the ejection head group 100 can be stabilized.

  Next, the ink ejection procedure using the inkjet apparatus 1 will be described. First, the ink to be used is supplied into the tank 500 to store the ink. Here, an ink in which a polymer material having a fluorene skeleton is dissolved or dispersed in a benzene-based or biphenyl-based solvent (for example, isopropyl biphenyl, cyclohexylbenzene, dimethyldiphenyl ether) was used. In this ink, the viscosity changes with time as shown in FIG. FIG. 6 is a graph showing the change in viscosity over time, with the vertical axis indicating the viscosity and the horizontal axis indicating the change over time.

  Thereafter, by operating the control device 6, ink is supplied from the tank 500 to the ejection head via the supply pipe 400. Then, ink is ejected to a predetermined region of the substrate W based on the operation of the ejection head. In this case, if necessary, the tank 500 is heated by the first heater 320 to heat the ink, and the viscosity of the ink is restored to the initial viscosity. Further, the ink that is being supplied is heated by the second heater 330 to further improve the viscosity recovery. Then, the ink is returned to room temperature by the cooling device 340 immediately before ejection, thereby improving ejection stability.

(Manufacture of organic electroluminescence (EL) devices)
A method for manufacturing an organic EL device by the ejection method of the above embodiment will be described. The organic EL device to be manufactured has a configuration as shown in FIG. That is, the organic EL device 200 according to this embodiment includes a transparent substrate 2 made of glass or the like, and light emitting elements arranged in a matrix. Here, the light emitting element includes a pixel electrode 111, a functional layer (organic EL layer) 110, and a cathode 12. The pixel electrode 111 is composed of a light-transmitting conductive film such as ITO (indium tin oxide), and the cathode 12 is composed of a light-reflecting conductive film such as aluminum.

  On the base 2, a pixel electrode 111 and a bank part 122 that partitions the functional layer 110 are disposed. The bank 122 is configured by laminating an inorganic bank layer (first bank layer) 112a located on the base 2 side and an organic bank layer (second bank layer) 112b located on the cathode 12 side.

  Next, the functional layer 110 includes a hole injection / transport layer 110a stacked on the pixel electrode 111 and a light emitting layer 110b formed adjacent to the hole injection / transport layer 110a. The hole injection / transport layer 110a has a function of injecting holes into the light emitting layer 110b and a function of transporting holes inside the hole injection / transport layer 110a. In the light emitting layer 110b, the holes injected from the hole injection / transport layer 110a and the electrons injected from the cathode 12 are recombined in the light emitting layer, and light emission is obtained.

  The light emitting layer 110b has three types, a red light emitting layer 110b1 that emits red (R), a green light emitting layer 110b2 that emits green (G), and a blue light emitting layer 110b3 that emits blue (B). The light emitting layers 110b1 to 110b3 are arranged in stripes.

  Next, a method for manufacturing the organic EL device 200 will be described. The process of manufacturing the organic EL device of this embodiment is basically composed of a partition wall (bank part) forming process, a hole injection / transport layer forming process, a light emitting layer forming process, a cathode forming process, and a sealing process. Configured. Of these steps, the droplet discharge method using the inkjet device 1 of the above embodiment can be suitably applied to the hole injection / transport layer forming step and the light emitting layer forming step.

  In the partition wall forming step, a bank part (partition wall) 120 that separates the pixel regions is formed on the transparent electrode 111 made of ITO or the like formed on the substrate 2 on which TFTs or the like are provided in advance as necessary. Specifically, the inorganic bank layer 112a made of an inorganic material and the organic bank layer 112b made of an organic material are each formed by patterning using a photolithography technique.

Next, in the hole injection / transport layer forming step, a hole injection / transport layer forming material (hole injection / transport layer forming ink) is discharged to each pixel region using the above-described droplet discharge method. As the hole injection / transport layer forming material, for example, a composition obtained by dissolving a mixture of a polythiophene derivative such as polyethylenedioxythiophene (PEDOT) and polystyrene sulfonic acid (PSS) in a polar solvent can be used. Examples of the polar solvent include isopropyl alcohol (IPA), normal butanol, γ-butyrolactone, N-methylpyrrolidone (NMP), 1,3-dimethyl-2-imidazolidinone (DMI) and its derivatives, carbitol acetate And glycol ethers such as butyl carbitol acetate. The hole injection / transport layer forming material 110a is formed by drying the discharged hole injection / transport layer forming material and evaporating the polar solvent contained in the hole injection / transport layer forming material.
The ink composition prepared with the hole injection / transport layer forming material and the polar solvent is not large, but changes with time such as viscosity and elastic modulus of the ink are observed. For this reason, by providing a heating mechanism in the ink tank or the ink supply pipe and performing the heat treatment of the ink, a more stable discharge and a highly reproducible drying process can be performed. Therefore, the hole injection / transport layer 110a having a uniform film thickness can be stably formed.

  Next, in the light emitting layer forming step, the light emitting layer forming material (light emitting layer forming ink) is discharged onto the hole injection / transport layer in each pixel region using the discharging method of the above embodiment. The light emitting layer forming material is composed of a solute component such as an organic EL material corresponding to each color and a nonpolar solvent. As organic EL materials, fluorene polymer derivatives are used, and isopropyl biphenyl, cyclohexylbenzene, and dimethyldiphenyl ether are used as nonpolar solvents. The combination of these materials can form a light-emitting layer with good characteristics, but the viscosity of the light-emitting layer-forming ink tends to change, and stable ejection and film formation are difficult. However, by providing a heating mechanism in the ink tank or the ink supply pipe and performing the heat treatment of the ink, a stable discharge and a highly reproducible drying process can be performed. For this reason, it is possible to stably form the light emitting layer 110b having a uniform thickness. Organic EL materials that are soluble in (poly) paraphenylene vinylene derivatives, polyphenylene derivatives, polyfluorene derivatives, polyvinylcarbazole, polythiophene derivatives, perylene dyes, coumarin dyes, rhodamine dyes, and other benzene derivatives An EL material or the like can be used. As the nonpolar solvent, dihydrobenzofuran, trimethylbenzene, tetramethylbenzene and the like can be used. Even when a combination of these materials is used, a heating mechanism is provided in the ink tank or the ink supply pipe, and the ink is heat-treated, thereby enabling more stable ejection and film formation. The non-polar solvent contained in the light emitting layer forming material is evaporated by drying the light emitting layer forming material after discharging, and the light emitting layer 110b is formed.

  Next, in the cathode forming step, the cathode 12 is formed on the entire surface of the light emitting layer 110 b and the bank part 122. In the sealing step, a sealing material made of thermosetting resin or ultraviolet curable resin is applied to the entire surface of the cathode 12 to form a sealing layer. Further, a sealing substrate is laminated on the sealing layer. Through the above steps, the organic EL device shown in FIG. 5 can be manufactured.

  As mentioned above, although embodiment of this invention was shown, this invention is not limited to the said embodiment. For example, in the inkjet apparatus 1, the heater (heating means) is provided in both the supply pipe (transfer means) and the tank (storage means), but a heater may be provided in either one. Further, the cooling device 340 is not limited to a constant temperature circulation device, and may be configured such that heating / cooling can be controlled by a temperature control unit, similarly to a heater. Furthermore, although the example which manufactures an organic EL apparatus using the said inkjet apparatus 1 was shown, the said inkjet apparatus 1 can be used also in another wiring formation process, a color filter manufacturing process, etc.

It is a schematic perspective view which shows the structure of the inkjet apparatus to which this invention is applied. It is a block diagram which shows the structure of the control system with respect to discharge operation of the inkjet apparatus shown in FIG. It is a block diagram which shows the structure for temperature control of the inkjet apparatus shown in FIG. It is a block diagram which shows an example of the chiller apparatus as a heating means. It is a cross-sectional schematic diagram which shows the structure of the organic electroluminescent apparatus manufactured using the inkjet apparatus. It is a graph which shows a time-dependent change of a viscosity. It is a figure which shows an example of the constant temperature circulation apparatus as a cooling means. It is a figure which shows an example of the cooling device provided with the radiation fin as a cooling means.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Inkjet apparatus, 100 ... Discharge head group (discharge head), 200 ... Organic EL apparatus, 320, 330 ... Heater (heating means), 340 ... Cooling device (cooling means), 400 ... Supply pipe (transfer means), 500 ... tank (storage means), W ... substrate (discharge target)

Claims (8)

An ejection head for ejecting a liquid material to a predetermined area of the object;
Storage means for storing the liquid material;
Transfer means for transferring the liquid material from the storage means to the discharge head;
Heating means for heating the liquid material in at least one of the storage means and the transfer means;
A liquid droplet ejection apparatus comprising: a cooling unit disposed on at least one of the ejection head side or the ejection head from the heating unit of the transfer unit and configured to cool the liquid state.   The droplet discharge apparatus according to claim 1, wherein the liquid has a viscosity that increases with time. Discharging the liquid material from the discharge head to a predetermined region of the object;
Storing the liquid in a storage means;
Having the step of transferring the liquid from the storage means to a discharge head;
In the storing step or the transferring step, after heating the liquid material,
A liquid droplet discharging method, wherein the liquid material is cooled before the discharging step.   The droplet discharge method according to claim 3, wherein the liquid has a viscosity that increases with time.   The droplet discharge method according to claim 3 or 4, wherein the heating temperature is equal to or lower than a glass transition temperature of a solute contained in the liquid.   6. The droplet discharge method according to claim 3, wherein the heating time is 5 minutes to 30 minutes.   7. The droplet discharge method according to claim 3, wherein after the heating, the heated liquid material is discharged from the discharge head within 24 hours. A method of manufacturing an organic EL device having an organic EL layer between a pair of electrodes,
A method for manufacturing an organic EL device, comprising a step of forming a film of the organic EL layer using the droplet discharge method according to claim 3.

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