JP4872263B2 - Method for manufacturing organic electroluminescence device - Google Patents

Description

  The present invention relates to a method for manufacturing an organic electroluminescence (hereinafter referred to as organic EL) element, and more particularly to a method for forming a light emitting layer.

  In recent years, the use of organic EL elements as light sources for display devices such as flat displays, electrophotographic copying machines, and printers has been studied.

  This organic EL element is a current-driven light-emitting element that emits light when a very thin thin film of a fluorescent organic compound is sandwiched between an anode and a cathode and a current is passed. Usually, the organic substance is an insulator, but by making the film thickness of the organic layer very thin, current can be injected and it can be driven as an organic EL element. It can be driven at a low voltage of 10 V or less, and it is possible to obtain highly efficient light emission.

  In particular, phosphorescent organic EL devices using excited triplets that far exceed the efficiency of conventional organic EL devices using excited singlets have been disclosed by S.C. R. Forrest et al. (See Non-Patent Document 1). Furthermore, C.I. As reported by Adachi et al. (See Non-Patent Document 2), such an element is expected to be applied to a display and illumination until it reaches a luminous efficiency as high as 60 lm / W.

  Currently, there are organic EL materials of low molecular weight and high molecular weight.

  In order to manufacture an EL element using a low molecular material, vapor deposition is performed in a high vacuum. Low molecular weight materials can be purified by sublimation, easy to purify, use high-purity organic EL materials, and make it easy to make a laminated structure. Yes.

However, since the vapor deposition is performed under a high vacuum condition of 10 ⁻⁴ Pa or less, the operation is complicated and the cost is high, which is not always preferable from the viewpoint of production. In particular, since it is necessary to form an element for a large area, it is difficult to manufacture by vapor deposition. In addition, phosphorescent dopants used in phosphorescent organic EL devices have a large area and are uniform, and it is difficult to introduce a plurality of dopants into the device by vapor deposition, which is difficult in terms of cost and technology. I must say.

  In contrast, polymer materials can employ wet processes such as spin coating, ink jetting, and printing for production. In other words, since it can be manufactured under atmospheric pressure, there is an advantage that the cost can be reduced. Furthermore, since it is prepared in a solution to form a thin film, it is easy to adjust dopants and the like, and it is difficult to cause unevenness even in a large area. It can be said that this is very advantageous in terms of cost and manufacturing technology for lighting applications of organic EL elements.

  However, in the current organic EL manufacturing method, the monocolor light-emitting layer and the full-color common layer are generally formed on the entire surface of the substrate regardless of the pixel region and the non-pixel region from the viewpoint of productivity. There are many situations. Here, since the material deposited on the non-pixel region naturally does not contribute to light emission, it is wasted. Since the material used for organic EL is very expensive, a manufacturing method with high material utilization efficiency and high production efficiency is desired. As a method capable of supplying material only to the pixel region, there is a droplet discharge method.

  As a conventional inkjet method, a piezo method that ejects ink droplets by deforming an ink flow path by vibration of a piezoelectric element, a heating element is provided in the ink flow path, and the heating element is heated to generate bubbles. There is a thermal method that discharges ink droplets according to pressure changes in the ink flow path due to air bubbles, and an electrostatic suction method that charges ink in the ink flow paths and discharges ink droplets by the electrostatic suction force of the ink. Are known.

  However, the above-described ink jet recording method has the following problems.

(1) Stability of micro droplet formation Since the nozzle diameter is large, the shape of the droplet discharged from the nozzle is not stable.

(2) Insufficient accuracy of landing of micro droplet The kinetic energy imparted to the droplet discharged from the nozzle decreases in proportion to the cube of the droplet radius. For this reason, micro droplets cannot secure sufficient kinetic energy to withstand air resistance, and are not expected to land accurately due to disturbance due to air convection. Furthermore, as the droplet becomes finer, the effect of surface tension increases, so the vapor pressure of the droplet increases and the amount of evaporation increases. For this reason, fine droplets cause a significant loss of mass during flight, and it is difficult to maintain the shape of the droplets upon landing. As described above, miniaturization and high accuracy of droplets are conflicting issues, and it has been difficult to realize both simultaneously.

  This poor landing position accuracy not only deteriorates the print image quality, but also becomes a serious problem when, for example, a circuit wiring pattern is drawn using a conductive ink by an inkjet technique. That is, the poor position accuracy can not only draw a wiring with a desired thickness, but can even cause a disconnection or a short circuit.

(3) High applied voltage According to the principle of the conventional electrostatic attraction method, electric charges are concentrated at the center of the meniscus to generate a bulge of the meniscus. The radius of curvature of this raised tailor cone tip is determined by the amount of charge concentration, and when the electrostatic force due to the amount of concentrated charge and the electric field strength exceeds the surface tension of the meniscus at that time, droplet separation begins.

  Since the maximum charge amount of the meniscus is determined by the physical property value of the ink and the radius of curvature of the meniscus, the minimum droplet size is determined by the physical property value of the ink (particularly the surface tension) and the electric field strength formed at the meniscus portion.

  In general, the surface tension of a liquid tends to be lower when it contains a solvent than a pure solvent, and since various inks are included in actual ink, increasing the surface tension is not possible. difficult. For this reason, the surface tension of the ink is considered to be constant, and a method of reducing the droplet size by increasing the electric field strength has been adopted.

  Therefore, in the conventional ink jet device, both of them as a discharge principle, a charge is concentrated at the center of the meniscus by forming a field with a strong electric field strength in a meniscus region having an area far larger than the projected area of the discharged droplet, Since ejection is performed by an electrostatic force composed of the concentrated electric charge and the electric field strength formed, it is necessary to apply a very high voltage close to 2000 [V], and it is difficult to control the drive and to operate the ink jet apparatus. There was also a problem in terms of safety.

(4) Discharge responsiveness In both conventional inkjet apparatuses, as a discharge principle, a charge field is formed at the center of the meniscus by forming a field having a strong electric field strength in a meniscus region having an area far larger than the projected area of the discharged droplet. Since the discharge is performed by electrostatic force composed of the concentrated electric charge and the electric field strength formed, the movement time of the electric charge for moving the electric charge to the center of the meniscus portion affects the discharge response and the printing speed. It has become a problem in improving.

  As described above, since the droplet ejection method has ejection defects such as flight bends, it can be said that it is at a level sufficient to directly draw a high-precision fine pattern required by an electronic device such as an organic EL. Absent.

  In order to solve such problems, attempts have been made to improve the following methods.

  There are some which make a substrate lyophilic and liquid repellent so as to cover the discharge accuracy of a droplet discharge method (for example, see Patent Document 1).

  However, this technique requires a partition wall to cover the discharge accuracy, and uses a photolithography method to make the partition wall. The photolithography process involves a complicated manufacturing process, and there is a concern that throughput may be reduced.

  In addition, there is a method of performing liquid repellency treatment on the substrate surface and regulating a droplet contact angle with respect to the substrate surface, thereby suppressing wetting spread on the substrate surface and retaining the droplet at a predetermined position (for example, (See Patent Document 2).

  However, the liquid repellency method of this technique performs plasma treatment or fluorinated alkylsilane coupling agent coating on the entire surface of the substrate, and is effective for those that have landed on the pixel area. There is no effect at all on the droplets that land on. In addition, it is estimated that only the pixel region can be made liquid repellent by using a mask or the like, but in that case, it is necessary to align the pixel region and the mask, and there is a concern that productivity may be lowered.

  A voltage is applied between the lower electrode and the auxiliary wiring on the partition wall and the nozzle, the attractive force and the repulsive force are adjusted by switching the applied voltage, and the charged droplet is guided onto the lower electrode (for example, Patent Documents). 3).

  However, this technique requires application of several types of voltages for each pixel, and there is a concern about a decrease in throughput.

  As described above, the conventional droplet discharge method requires various processes such as alignment, bank, surface treatment, and electric field control due to the problem of discharge accuracy, and has a problem in productivity.

The present invention provides an alignment-free and highly accurate droplet discharge method, and provides an organic EL manufacturing method that does not reduce production efficiency and significantly improves material utilization efficiency. By using the present invention, in a monochrome panel, it is possible to form a functional material or a light emitting layer only on the pixel electrode without switching the power source. Even in a full-color panel, although not applicable to the light emitting layer, a common material can be similarly formed only on the pixel portion, so that the manufacturing cost can be reduced.
JP 2002-334882 A JP 2002-124381 A JP 2003-59660 A Appl. Phys. Lett. (1999), 75 (1), 4-6 J. et al. Appl. Phys. , 90, 5048 (2001)

  An object of the present invention is to provide an organic EL manufacturing method in which production efficiency is not lowered and material utilization efficiency is remarkably improved by an alignment-free and highly accurate droplet discharge method.

  The above problem could be solved by the following configuration.

(1) In a method for manufacturing an organic electroluminescence element having at least a first pixel electrode, an organic functional layer formed on the first pixel electrode, and a second pixel electrode formed on the organic functional layer. ,
An organic substrate for forming the organic functional layer is formed on a substrate on which the first pixel electrode is formed and on which a partition wall for partitioning a pixel electrode region and forming a non-pixel electrode region is formed on the first pixel electrode. Supported on the lower electrode arranged opposite to the nozzle electrode of the electrostatic suction type droplet discharge device that discharges the functional layer coating liquid from the nozzle ,
In a state of applying a predetermined voltage between the lower electrode and the nozzle electrode, the Rukoto the substrate and the droplet discharge equipment are relatively moved so that the position of said substrate opposite to said nozzle moves,
I by the electric field intensity difference based on the presence or absence of the partition wall between the lower electrode and the nozzle electrode,
A method of manufacturing an organic electroluminescence element, wherein an organic functional layer coating solution is selectively discharged from the nozzle to the pixel electrode region.

(2) The organic electroluminescent element according to claim 1, wherein the organic functional layer formed by the organic functional layer coating solution is any one of a carrier injection layer, a carrier transport layer, and a light emitting layer. Production method.

  (3) The method for producing an organic electroluminescent element as described in 1 or 2 above, further comprising at least one charge removing step immediately before discharging the organic functional layer coating solution.

(4) the Bruno nozzle diameter of's Le is, the method of manufacturing the organic electroluminescence device according to any one of the above 1 to 3, wherein the at 20μm or less.

(5) the nozzle diameter of Nozzle method of manufacturing an organic electroluminescence device according to any one of the above 1 to 3, characterized in that a 8μm or less.

(6) the nozzle diameter of Nozzle method of manufacturing an organic electroluminescence device according to any one of the above 1 to 3, characterized in that a 4μm or less.

  Here, the organic functional layer coating solution is a layer having any one or more of various functional layers such as various carrier injection layers, carrier transport layers, and light emitting layers inserted as part of the element configuration of the organic EL element. If there is no particular limit.

  In addition, the “base material” refers to an object that receives the landing of the droplets of the discharged solution. More specifically, a conductive region and a non-conductive region are formed like a pixel electrode pattern substrate. The substrate is formed in a pattern.

  According to the first aspect of the present invention, the substrate tip is insulated from the substrate by moving the nozzle tip and the substrate relatively in a state where a bias voltage is applied to the nozzle tip within a range in which ejection can be performed only on the pixel electrode region. Since patterning is performed using the difference in electric field strength generated according to the conductive pattern, the pulse voltage required for ejection, which has been required in the past, can be dispensed with, and only the necessary part is ejected. Material costs can also be reduced.

  According to the invention described in 2 above, by removing the charge prior to patterning and removing the deposits on the substrate, the disturbance of the electric field formed by the lower electrode and the nozzle electrode can be reduced, and accurate patterning is possible. It becomes.

  In the method for manufacturing an organic EL element, the nozzle diameter of the nozzle is preferably 20 μm or less.

  In the method for manufacturing an organic EL element, it is preferable that the nozzle diameter of the nozzle is 8 μm or less.

  In the method for manufacturing an organic EL element, it is preferable that the nozzle diameter of the nozzle is 4 μm or less.

  In the present invention, the nozzle diameter refers to the internal diameter of the nozzle tip.

  By setting the nozzle diameter to 20 μm or less, the electric field strength distribution becomes narrow. As a result, the electric field can be concentrated. As a result, the formed droplets can be made minute and the shape can be stabilized, and the total applied voltage can be reduced. In addition, immediately after the droplet is ejected from the nozzle, the droplet is accelerated by an electrostatic force acting between the electric field and the electric charge. However, when the droplet is separated from the nozzle, the electric field rapidly decreases, and thereafter, the droplet is decelerated due to air resistance. However, a droplet that is a minute droplet and has a concentrated electric field is accelerated by mirror image force as it approaches the counter electrode. By balancing the deceleration by the air resistance and the acceleration by the mirror image force, it is possible to stably fly the fine droplets and improve the landing accuracy.

  The internal diameter of the nozzle is preferably 8 μm or less. By making the internal diameter of the nozzle 8 μm or less, it is possible to further concentrate the electric field, further reducing the size of the droplets and reducing the influence of fluctuations in the distance of the counter electrode on the electric field strength distribution during flight. Therefore, it is possible to reduce the influence of the position accuracy of the counter electrode, the characteristics of the base material, and the thickness on the droplet shape and the impact accuracy.

  Furthermore, by setting the internal diameter of the nozzle to 4 μm or less, a remarkable electric field concentration can be achieved, the maximum electric field strength can be increased, the shape of the droplet can be made extremely fine, The initial discharge speed can be increased. Thereby, by improving the flight stability, it is possible to further improve the landing accuracy and improve the ejection response.

  The inner diameter of the nozzle is preferably larger than 0.2 μm. By making the inner diameter of the nozzle larger than 0.2 μm, it is possible to improve the charging efficiency of the droplets, and thus it is possible to improve the droplet discharge stability.

Furthermore, in the configuration of each claim,
(1) Preferably, the nozzle is formed of an electrical insulating material, and an electrode is inserted into the nozzle or plated.

  (2) In the configuration of each of the above claims or the configuration of (1), it is preferable that the nozzle is formed of an electrical insulating material, the electrode is inserted or plated in the nozzle, and the electrode is provided outside the nozzle.

  According to (1) and (2), in addition to the effects of the above claims, the discharge force can be improved, so that the liquid can be discharged at a low voltage even if the nozzle diameter is further reduced.

  (3) In the configuration of each of the above claims and the configuration of (1) or (2), the base material is preferably formed of a conductive material or an insulating material.

  (4) In the configuration of each of the above claims and the configuration of (1), (2) or (3), the voltage V applied to the nozzle is

It is preferable to drive in the basin represented by

  However, γ: surface tension of liquid, ε0: dielectric constant of vacuum, r: nozzle radius, h: distance between nozzle and substrate, k: proportional constant (1.5 <k <8.5) depending on nozzle shape To do.

  (5) In the configurations of the above claims and the configurations of (1), (2), (3), or (4), it is preferable that the arbitrary waveform voltage to be applied is 1000 V or less.

  (6) In the configurations of the above claims and the configurations of (1), (2), (3), (4) or (5), it is preferable that the arbitrary waveform voltage to be applied is 500 V or less.

  It is preferable to place the substrate on a conductive or insulating substrate holder.

  (7) In the configuration of each of the above claims and the configuration of any of (1) to (6) above, the distance between the nozzle and the substrate is preferably 500 μm or less.

  (8) In the configuration of each of the above claims and the configuration of any one of (1) to (7), it is preferable that the pressure is applied to the solution in the nozzle.

  (9) In the configuration of each of the above claims and the configuration of any of the above (1) to (8), when discharging by a single pulse,

A configuration may be adopted in which a pulse width Δt having a time constant τ or more determined by is applied.

  Where ε is the dielectric constant of the fluid and σ is the conductivity.

  According to the present invention, it is possible to provide an organic EL manufacturing method in which production efficiency is not lowered and material utilization efficiency is remarkably improved by an alignment-free and highly accurate droplet discharge method.

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

  1A and 1B are diagrams for explaining an organic EL element. FIG. 1A is a top view of a main part of an organic functional layer, and FIG. 1B is a cross-sectional view of the main part taken along line AA in FIG. FIG.

  As shown in FIGS. 1A and 1B, an organic EL element 201 of the present invention has a light emitting layer 203 and a second pixel electrode as an organic functional layer on a substrate K, at least on the pattern of the first pixel electrode 202. 204 is formed, and the pattern of the light emitting layer 203 on the first pixel electrode is the electrostatic suction type droplet discharge device 20 (see FIG. 2) provided in the image recording device 101 (see FIGS. 2 and 3) described later. 3). A first pixel electrode 202 is formed in a stripe shape on the substrate K, a partition 205 is formed so as to be orthogonal to the first pixel electrode 202, and a light emitting layer is formed in a region sandwiched by the partition on the first pixel electrode. The second pixel electrode 204 is formed in a stripe shape so as to be orthogonal to the first pixel electrode 202. Here, a passive system and a single organic layer are simply shown, but an active system or a plurality of organic functional layers may be used. The partition wall 205 divides the pixel region and forms a later-described electric field strength difference.

  FIG. 4 is a diagram showing the positional relationship between the first pixel electrode 202 and the partition wall 205 formed on the substrate K and the nozzle 21 and the relative relationship between potentials in the pixel electrode region and the non-pixel electrode region.

That is, the light emitting layer 203 has a pattern in which the tip of the ultrafine nozzle 21 to which the organic functional layer coating solution is supplied is disposed close to the substrate, and the bias voltage V _A , back electrode is applied to the solution in the nozzle. By moving the nozzle and the substrate relative to each other with the bias voltage V _B applied thereto, the electric field on the pixel electrode region formed by V _A and V _B is V1, and the electric field on the non-pixel electrode is Assuming that V2 is satisfied, only the electric field V1 on the pixel electrode on the substrate satisfies the threshold voltage (Vth), that is, the ejection voltage necessary for ejection, so that the ultrafine droplets can be output without the ejection pulse signal to the first pixel electrode 202. The organic functional layer pattern is formed by being discharged onto the substrate and then dried by heating the substrate.

  As described above, according to the present invention, by using the liquid ejecting apparatus 20, (a) improvement in tact time by eliminating the need for alignment processing, and (b) unnecessary control of the pulse signal necessary for ejection. This makes it possible to reduce the device cost, and (c) reduce the material cost by forming an expensive functional organic material solution only on the pixel electrode. Further, by using an electrostatic suction type droplet discharge device having an ultrafine diameter nozzle, the pattern of the organic light emitting layer 203 can be accurately formed. As described above, in the production of the organic EL element 201, it is possible to achieve both reduction of productivity, material, and facility cost.

  In the present invention, it is preferable to have at least one charge removing step immediately before discharging the organic functional layer coating solution. By discharging the functional organic material solution in a state where the charge removal step is performed and the substrate surface potential is returned to neutral, it is possible to prevent discharge failure (position shift, discharge omission) and the like.

  The coating liquid according to the present invention is not particularly limited as long as it is a solution in which a material constituting a part of the organic EL element is dissolved or dispersed in water or an organic solvent.

In the case of a hole injection / transport layer, a polyethylenedioxythiophene / polystyrene sulfonate (PEDOT / PSS) aqueous dispersion is typically used. Further, in the case of a light emitting layer, polyvinyl carbazole (PVK) as a host and a dopant (red: BtpIr (acac), green: Ir (ppy) ₃ , blue: FIr (pic), etc.) are appropriately added at a predetermined concentration. Examples thereof include a solution dissolved in dichloroethane.

  Next, in the manufacturing method for manufacturing the organic EL element of the present invention, the configuration and operation of an image recording apparatus provided with a liquid ejection device will be described.

[Image recording device]
(Overall configuration of image recording device)
Hereinafter, the image recording apparatus will be described with reference to FIGS. FIG. 2 is a schematic configuration diagram of an image recording apparatus using a sheet-like substrate. FIG. 3 is a schematic configuration diagram of an image recording apparatus using a flexible substrate.

  In FIG. 2, an image recording apparatus 101 includes an image recording table 102 for supporting a substrate (hereinafter simply referred to as a substrate K), and an organic functional layer coating that is disposed above the image recording table 102 and can be charged. An upstream side in the transport direction of the substrate K of the image recording table 102 and a liquid discharge device 20 in which a super-fine nozzle 21 for discharging a liquid (hereinafter simply referred to as a coating solution) is directed to the image recording table 102 And conveyance rollers 103a and 103b arranged on the downstream side, and pressure contact rollers 104a and 104b sandwiched between these conveyance rollers 103a and 103b.

  The liquid ejection device 20 may be a scanning type liquid ejection device that can be scanned in a direction orthogonal to the transport direction of the substrate K (the left direction in FIG. 2) by a driving device (not shown). In this case, a plurality of nozzles 21 are arranged in the liquid ejection device 20.

  The liquid discharge device 20 may be a line-type liquid discharge device in which a large number of nozzles 21 are arranged in a direction orthogonal to the transport direction of the substrate K.

  Moreover, it is preferable to have at least one or more charge removing steps immediately before discharging the organic functional layer coating liquid, and 40 in FIG. 2 represents a charge removing device.

  Further, the droplets may be dried by providing a heating means (for example, a heater) for heating the substrate K in the vicinity of the substrate.

  In the image recording apparatus 101 illustrated in FIG. 3, the flexible substrate is transported from the original winding 51 of the flexible substrate K by the backup roll 50 and the transport roll 52. A bias voltage 30 is applied between the nozzle 21 of the liquid ejection device 20 and the backup roll 50, and a first pixel electrode is provided in advance on the flexible substrate to be transported.

  The present invention makes it possible to perform patterning by discharging droplets from a nozzle using the fact that the electric field strength differs between the conductive first pixel electrode portion and the non-pixel electrode portion.

[Liquid ejection device]
(Overall configuration of liquid ejection device)
FIG. 5 shows details of the liquid ejection device 20 applied to the image recording apparatus 101 shown in FIGS. 2 and 3, and FIG. 5 is a cross-sectional view of the liquid ejection device 20 along the nozzle 21.

  The liquid ejection device 20 has an ultra-fine nozzle 21 that ejects a droplet of a chargeable solution from its tip, a facing surface that faces the tip of the nozzle 21, and the landing of the droplet on the facing surface. The counter electrode 23 that supports the substrate K on which the first pixel electrode 202 is received, the solution supply means that supplies the solution to the flow path 22 in the nozzle 21, and the discharge voltage is applied to the solution in the nozzle 21. And an ejection voltage applying means 25. A part of the nozzle 21 and the solution supply means and a part of the discharge voltage applying means 25 are integrally formed by a nozzle plate 26.

(nozzle)
The nozzle 21 is integrally formed with an upper surface layer 26c of a nozzle plate 26 described later, and is erected vertically from a flat plate surface of the nozzle plate 26. Further, the nozzle 21 is formed with an in-nozzle flow path 22 penetrating from the tip portion along the center line.

  The nozzle 21 will be further described in detail. As described above, the nozzle 21 is formed with an ultrafine diameter. As an example of specific dimensions of each part, the internal diameter of the nozzle internal flow path 22 is 1 μm, the external diameter at the tip of the nozzle 21 is 2 μm, the root diameter of the nozzle 21 is 5 μm, and the height of the nozzle 21 is It is set to 100 μm, and its shape is formed in a truncated cone shape close to a conical shape. The entire nozzle 21 is formed of an insulating resin material together with the upper surface layer 26 c of the nozzle plate 26.

  In addition, each dimension of a nozzle is not limited to the said example. In particular, the inner diameter of the nozzle is within a range in which the discharge voltage that enables the discharge of liquid droplets by the effect of electric field concentration described below is less than 1000 V, for example, the nozzle diameter is 70 μm or less, and more preferably 20 μm or less. And the diameter which is a range which can form the through-hole which lets a solution pass with the present nozzle formation technique is made into the lower limit.

  The nozzle diameter of the liquid ejection device (inner diameter at the nozzle tip) is preferably 20 μm or less, more preferably 8 μm or less, and even more preferably 4 μm or less. The nozzle diameter is preferably larger than 0.2 μm.

(Solution supply means)
The solution supply means is provided inside the nozzle plate 26 at a position that is the root of the nozzle 21 and communicates the solution from the external solution tank (not shown) to the solution chamber 24. A supply path 27 that guides and a supply pump (not shown) that applies a supply pressure of the solution to the solution chamber 24 are provided.

  The supply pump supplies the solution to the tip of the nozzle 21 and supplies the solution while maintaining the supply pressure in a range that does not spill from the tip.

(Discharge voltage application means)
The discharge voltage applying means 25 includes a discharge electrode 28 for applying a discharge voltage provided in a boundary position between the solution chamber 24 and the nozzle flow path 22 inside the nozzle plate 26, and the discharge electrode 28 is always subjected to direct current. And a bias power supply 30 for applying a bias voltage of.

  The discharge electrode 28 is in direct contact with the solution inside the solution chamber 24 to charge the solution and apply a discharge voltage.

  The bias voltage by the bias power supply 30 is such that the solution is discharged on the pixel electrode region and the voltage is constantly applied in a range where the solution is not discharged outside the pixel electrode region, thereby eliminating the need for a pulse voltage at the time of discharge. Yes.

(Liquid discharge head)
The liquid discharge head 26 includes a base layer 26a positioned at the lowest level in FIG. 3, a flow path layer 26b that forms a solution supply path positioned above the base layer 26a, and an upper surface formed further above the flow path layer 26b. The nozzle plate 26c is a layer, and the application electrode 28 described above is interposed between the flow path layer 26b and the upper surface layer 26c.

  The base layer 26a is formed of a silicon substrate or a highly insulating resin or ceramic, forms a soluble resin layer on the base layer 26a, and removes only a portion that follows the pattern of the supply path 27 and the solution chamber 24, An insulating resin layer is formed on the removed portion. This insulating resin layer becomes the flow path layer 26b. A discharge electrode 28 is formed on the upper surface of the insulating resin layer by plating with a conductive material (for example, NiP), and an insulating resist resin layer is formed thereon. Since this resist resin layer becomes the upper surface layer 26 c, this resin layer is formed with a thickness in consideration of the height of the nozzle 21. Then, this insulating resist resin layer is exposed by an electron beam method or a femtosecond laser to form a nozzle shape. The nozzle internal flow path 22 is also formed by laser processing. Then, the dissolvable resin layer according to the pattern of the supply path 27 and the solution chamber 24 is removed, and the supply path 27 and the solution chamber 24 are opened to complete the liquid discharge head.

(Counter electrode)
The counter electrode 23 has a counter surface perpendicular to the nozzle 21 and supports the substrate K along the counter surface. As an example, the distance from the tip of the nozzle 21 to the opposing surface of the opposing electrode 23 is set to 100 μm.

  Further, since the counter electrode 23 is grounded, the ground potential is always maintained. Accordingly, the liquid droplets ejected by the electrostatic force generated by the electric field generated between the tip of the nozzle 21 and the opposing surface are guided to the opposing electrode 23 side.

  The liquid ejection device 20 ejects liquid droplets by increasing the electric field strength by concentrating the electric field at the tip of the nozzle 21 due to the ultra-miniaturization of the nozzle 21, so that the liquid ejection device 20 does not need to be guided by the counter electrode 23. Although it is possible to discharge droplets, it is desirable that induction by electrostatic force is performed between the nozzle 21 and the counter electrode 23. In addition, the charge of the charged droplet can be released by grounding the counter electrode 23.

(Image recording operation by image recording device)
Next, the operation of the image recording apparatus 101 will be described with reference to FIG.

  First, the conveyance roller 103a is rotationally driven to convey the substrate K to the image recording table 102 while being sandwiched between the conveyance roller 103a and the pressure roller 104a.

  In the scanning liquid ejection device 20 with respect to the substrate K, liquid is ejected onto the substrate K while scanning the liquid ejection device 20 in the transport direction of the substrate K, or a line type liquid ejection device 20 is used. In the liquid ejection device 20, liquid droplets are adhered to the substrate K by ejecting the liquid to the substrate K in a line shape. The substrate K after image recording is sandwiched between the transport roller 103b and the pressure roller 104b and removed from the image recording table 102.

(Discharge operation of micro droplets by liquid discharge device)
Next, the operation of the liquid ejection apparatus 20 in the image recording apparatus 101 will be described with reference to FIGS.

  The solution is supplied to the nozzle flow path 22 by the supply pump of the solution supply means, and in this state, a bias voltage is applied to the solution via the discharge electrode 28 by the bias power supply 30. In this state, the solution is charged, and a meniscus that is recessed in the solution is formed at the tip of the nozzle 21 (FIG. 6A).

  When a voltage that enables ejection is applied to the pixel electrode region on the substrate surface and the tip of the nozzle, the solution is guided to the tip of the nozzle 21 by electrostatic force due to the electric field strength of the concentrated electric field at the tip of the nozzle 21. As a result, a convex meniscus protruding to the outside is formed, and the electric field is concentrated by the apex of the convex meniscus, and finally a fine droplet is discharged to the counter electrode side against the surface tension of the solution (see FIG. 6 (B)).

  Since the liquid discharge device 20 discharges droplets with a nozzle 21 having a small diameter that has not been conventionally used, the electric field is concentrated by the charged solution in the flow path 22 in the nozzle, and the electric field strength is increased. For this reason, a nozzle having a structure in which electric field concentration is not performed (for example, an inner diameter of 100 μm) as in the prior art has been considered impossible to discharge because the voltage required for discharge becomes too high. Therefore, it is possible to discharge the solution at a lower voltage than in the prior art.

  And since it has a fine diameter, it is possible to easily perform control for reducing the discharge flow rate per unit time due to the low nozzle conductance, and sufficiently small droplet diameter without reducing the pulse width (see above). According to each condition, discharge of the solution by 0.8 μm) is realized.

  In addition, since the ejected droplets are charged, the vapor pressure is reduced even for very small droplets and the evaporation is suppressed, so the loss of droplet mass is reduced and the flight is stabilized. , Preventing a drop in droplet landing accuracy.

  In order to obtain an electrowetting effect on the nozzle 21, an electrode may be provided on the outer periphery of the nozzle 21, or an electrode may be provided on the inner surface of the nozzle internal flow path 22 and covered with an insulating film thereon. . By applying a voltage to this electrode, the wettability of the inner surface of the nozzle flow path 22 can be increased due to the electrowetting effect with respect to the solution to which the voltage is applied by the discharge electrode 28. It is possible to smoothly supply the solution to the flow path 22, to discharge well, and to improve the responsiveness of discharge.

  Hereinafter, a gas barrier layer, a first pixel electrode, a hole transport layer, a light emitting layer, an electron transport layer, a second pixel electrode, a sealing layer, and the like constituting the organic EL element according to the present invention will be described.

  The substrate having the pixel electrode region and the non-pixel electrode region used in the present invention may be a continuous flexible substrate or a sheet substrate.

  A transparent resin film is mentioned as a strip | belt-shaped flexible board | substrate. Examples of the resin film include polyesters such as polyethylene terephthalate (PET) and polyethylene naphthalate (PEN), polyethylene, polypropylene, cellophane, cellulose diacetate, cellulose triacetate, cellulose acetate butyrate, cellulose acetate propionate (CAP), Cellulose esters such as cellulose acetate phthalate (TAC) and cellulose nitrate or derivatives thereof, polyvinylidene chloride, polyvinyl alcohol, polyethylene vinyl alcohol, syndiotactic polystyrene, polycarbonate, norbornene resin, polymethylpentene, polyether ketone, polyimide , Polyethersulfone (PES), polyphenylene sulfide, polysulfones, Cycloolefin resins such as polyether imide, polyether ketone imide, polyamide, fluororesin, nylon, polymethyl methacrylate, acrylic or polyarylate, Arton (trade name, manufactured by JSR) or Appel (trade name, manufactured by Mitsui Chemicals) Is mentioned.

A gas barrier film is preferably formed on the surface of the resin film used as the belt-like flexible substrate, if necessary. Examples of the gas barrier film include an inorganic film, an organic film, or a hybrid film of both. As a characteristic of the gas barrier film, the water vapor permeability is preferably 0.01 g / m ² · day · atm or less. Furthermore, a high barrier film having an oxygen permeability of 10 ⁻³ ml / m ² · day or less and a water vapor permeability of 10 ⁻⁵ g / m ² · day or less is preferable.

  As a material for forming the barrier film, any material may be used as long as it has a function of suppressing intrusion of elements that cause deterioration of elements such as moisture and oxygen. For example, silicon oxide, silicon dioxide, silicon nitride, or the like can be used. Further, in order to improve the brittleness of the film, it is more preferable to have a laminated structure of these inorganic layers and layers made of organic materials. Although there is no restriction | limiting in particular about the lamination | stacking order of an inorganic layer and an organic layer, It is preferable to laminate | stack both alternately several times. The method for forming the barrier film is not particularly limited. For example, the vacuum deposition method, the sputtering method, the reactive sputtering method, the molecular beam epitaxy method, the cluster ion beam method, the ion plating method, the plasma polymerization method, the atmospheric pressure plasma weighting. A combination method, a plasma CVD method, a laser CVD method, a thermal CVD method, a coating method, and the like can be used, but an atmospheric pressure plasma polymerization method as described in JP-A-2004-68143 is particularly preferable.

As the first pixel electrode, an electrode material made of a metal, an alloy, an electrically conductive compound, or a mixture thereof having a high work function (4 eV or more) is preferably used. Specific examples of such an electrode substance include metals such as Au, and conductive transparent materials such as CuI, indium tin oxide (ITO), SnO ₂ , and ZnO. Alternatively, an amorphous material such as IDIXO (In ₂ O ₃ .ZnO) capable of forming a transparent conductive film may be used. For the anode, these electrode materials may be formed into a thin film by a method such as vapor deposition or sputtering, and a pattern having a desired shape may be formed by a photolithography method, or when the pattern accuracy is not required (about 100 μm or more) ), A pattern may be formed through a mask having a desired shape when the electrode material is deposited or sputtered. Or when using the substance which can be apply | coated like an organic electroconductivity compound, wet film-forming methods, such as a printing system and a coating system, can also be used. When light emission is taken out from the anode, it is desirable that the transmittance is greater than 10%, and the sheet resistance as the anode is preferably several hundred Ω / □ or less. Further, although the film thickness depends on the material, it is usually selected in the range of 10 to 1000 nm, preferably 10 to 200 nm.

  A hole injection layer (anode buffer layer) may be present between the first pixel electrode and the light emitting layer or the hole transport layer. The hole injection layer is a layer provided between the electrode and the organic layer in order to lower the driving voltage and improve the luminance of light emission. “The organic EL element and the forefront of industrialization (November 30, 1998, NTS) The details are described in the second volume, Chapter 2, “Electrode Materials” (pages 123 to 166) of “The Company”. The details of the anode buffer layer (hole injection layer) are described in JP-A-9-45479, JP-A-9-260062, JP-A-8-288069 and the like. As a specific example, copper phthalocyanine is used. Examples thereof include a phthalocyanine buffer layer represented by an oxide, an oxide buffer layer represented by vanadium oxide, an amorphous carbon buffer layer, and a polymer buffer layer using a conductive polymer such as polyaniline (emeraldine) or polythiophene.

  The hole transport layer is made of a hole transport material having a function of transporting holes, and in a broad sense, a hole injection layer and an electron blocking layer are also included in the hole transport layer. The hole transport layer can be provided as a single layer or a plurality of layers. The hole transport material has any one of hole injection or transport and electron barrier properties, and may be either organic or inorganic. For example, triazole derivatives, oxadiazole derivatives, imidazole derivatives, polyarylalkane derivatives, pyrazoline derivatives and pyrazolone derivatives, phenylenediamine derivatives, arylamine derivatives, amino-substituted chalcone derivatives, oxazole derivatives, styrylanthracene derivatives, fluorenone derivatives, hydrazone derivatives, Examples include stilbene derivatives, silazane derivatives, aniline copolymers, and conductive polymer oligomers, particularly thiophene oligomers.

  The above-mentioned materials can be used as the hole transport material, but it is preferable to use a porphyrin compound, an aromatic tertiary amine compound and a styrylamine compound, particularly an aromatic tertiary amine compound. Representative examples of aromatic tertiary amine compounds and styrylamine compounds include N, N, N ', N'-tetraphenyl-4,4'-diaminophenyl; N, N'-diphenyl-N, N'- Bis (3-methylphenyl)-[1,1′-biphenyl] -4,4′-diamine (TPD); 2,2-bis (4-di-p-tolylaminophenyl) propane; 1,1-bis (4-di-p-tolylaminophenyl) cyclohexane; N, N, N ′, N′-tetra-p-tolyl-4,4′-diaminobiphenyl; 1,1-bis (4-di-p-tolyl) Aminophenyl) -4-phenylcyclohexane; bis (4-dimethylamino-2-methylphenyl) phenylmethane; bis (4-di-p-tolylaminophenyl) phenylmethane; N, N'-diphenyl-N, N ' − (4-methoxyphenyl) -4,4'-diaminobiphenyl; N, N, N ', N'-tetraphenyl-4,4'-diaminodiphenyl ether; 4,4'-bis (diphenylamino) quadriphenyl; N, N, N-tri (p-tolyl) amine; 4- (di-p-tolylamino) -4 '-[4- (di-p-tolylamino) styryl] stilbene; 4-N, N-diphenylamino- (2-diphenylvinyl) benzene; 3-methoxy-4′-N, N-diphenylaminostilbenzene; N-phenylcarbazole, and also two of those described in US Pat. No. 5,061,569. Having a condensed aromatic ring in the molecule, for example, 4,4'-bis [N- (1-naphthyl) -N-phenylamino] biphenyl (NPD), JP-A-4-3086 4,4 ', 4 "-tris [N- (3-methylphenyl) -N-phenylamino] triphenylamine in which three triphenylamine units described in Japanese Patent No. 8 are linked in a starburst type ( MTDATA) and the like.

  Furthermore, a polymer material in which these materials are introduced into a polymer chain or these materials are used as a polymer main chain can also be used. In addition, inorganic compounds such as p-type-Si and p-type-SiC can also be used as the hole injection material and the hole transport material.

  JP-A-11-251067, J. Org. Huang et. al. A so-called p-type hole transport material described in a book (Applied Physics Letters 80 (2002), p. 139) can also be used. In the present invention, it is preferable to use these materials because a light-emitting element with higher efficiency can be obtained.

  Although there is no restriction | limiting in particular about the film thickness of a positive hole transport layer, Usually, 5 nm-about 5 micrometers, Preferably it is 5-200 nm. This hole transport layer may have a single layer structure composed of one or more of the above materials. A hole transport layer having a high p property doped with impurities can also be used. Examples thereof include JP-A-4-297076, JP-A-2000-196140, JP-A-2001-102175, J.A. Appl. Phys. 95, 5773 (2004), and the like. It is preferable to use such a hole transport layer having a high p property because an organic EL element with lower power consumption can be produced.

  In the present invention, the light emitting layer refers to a blue light emitting layer, a green light emitting layer, and a red light emitting layer. There is no restriction | limiting in particular as a lamination order in the case of laminating | stacking a light emitting layer, You may have a nonluminous intermediate | middle layer between each light emitting layer. In the present invention, it is preferable that at least one blue light emitting layer is provided at a position closest to the anode in all the light emitting layers. Also, when four or more light emitting layers are provided, for example, blue light emitting layer / green light emitting layer / red light emitting layer / blue light emitting layer, blue light emitting layer / green light emitting layer / red light emitting layer / blue light emitting from the order close to the anode. Layered / green light emitting layer, blue light emitting layer / green light emitting layer / red light emitting layer / blue light emitting layer / green light emitting layer / red light emitting layer, etc. It is preferable for improving luminance stability. A white element can be manufactured by forming a light emitting layer in multiple layers.

  The total thickness of the light emitting layer is not particularly limited, but is usually selected in the range of 2 nm to 5 μm, preferably 2 to 200 nm in consideration of the uniformity of the film and the voltage required for light emission. Furthermore, it is preferable that it exists in the range of 10-20 nm. A film thickness of 20 nm or less is preferable because it has the effect of improving the stability of the emission color with respect to the driving current as well as the voltage surface. The film thickness of each light emitting layer is preferably selected in the range of 2 to 100 nm, and more preferably in the range of 2 to 20 nm. Although there is no restriction | limiting in particular about the film thickness relationship of each light emitting layer of blue, green, and red, It is preferable that the blue light emitting layer (the sum total when there are two or more layers) is the thickest among three light emitting layers.

  The light emitting layer includes at least three layers having different emission spectra, each having an emission maximum wavelength in the range of 430 to 480 nm, 510 to 550 nm, and 600 to 640 nm. If it is three or more layers, there will be no restriction | limiting in particular. When there are more than four layers, there may be a plurality of layers having the same emission spectrum. A layer having an emission maximum wavelength in the range of 430 to 480 nm is referred to as a blue light emitting layer, a layer in the range of 510 to 550 nm is referred to as a green light emitting layer, and a layer in the range of 600 to 640 nm is referred to as a red light emitting layer. Moreover, in the range which maintains the said maximum wavelength, you may mix a several luminescent compound in each light emitting layer. For example, the blue light emitting layer may be used by mixing a blue light emitting compound having a maximum wavelength of 430 to 480 nm and a green light emitting compound having the same wavelength of 510 to 550 nm.

  The material used for the light emitting layer is not particularly limited, and examples thereof include the latest trends of Toray Research Center, Inc. flat panel displays, the current state of EL displays and the latest technological trends, and various materials as described on pages 228-332.

  The electron injection layer is made of a material having a function of transporting electrons and is included in the electron transport layer in a broad sense. The electron injection layer is a layer provided between the electrode and the organic layer for lowering the driving voltage and improving the luminance of the light emission. “Organic EL element and its forefront of industrialization (NST 30, November 30, 1998) Issue) ”, Chapter 2, Chapter 2,“ Electrode Materials ”(pages 123-166). The details of the electron injection layer (cathode buffer layer) are also described in JP-A-6-325871, JP-A-9-17574, JP-A-10-74586, and the like. Specifically, strontium, aluminum, etc. Metal buffer layer typified by lithium, alkali metal compound buffer layer typified by lithium fluoride, alkaline earth metal compound buffer layer typified by magnesium fluoride, oxide buffer layer typified by aluminum oxide, etc. . The buffer layer (injection layer) is preferably a very thin film, and the film thickness is preferably in the range of 0.1 nm to 5 μm although it depends on the material.

  In addition, as an electron transport material (also serving as a hole blocking material) used for the electron transport layer adjacent to the light emitting layer side, it is sufficient if it has a function of transmitting electrons injected from the cathode to the light emitting layer. As a material, any one of conventionally known compounds can be selected and used. For example, nitro-substituted fluorene derivatives, diphenylquinone derivatives, thiopyran dioxide derivatives, carbodiimides, fluorenylidenemethane derivatives, anthraquinodisides. Examples include methane and anthrone derivatives, oxadiazole derivatives and the like. Furthermore, in the above oxadiazole derivatives, thiadiazole derivatives in which the oxygen atom of the oxadiazole ring is substituted with a sulfur atom, and quinoxaline derivatives having a quinoxaline ring known as an electron-withdrawing group can also be used as the electron transport material. Furthermore, a polymer material in which these materials are introduced into a polymer chain or these materials are used as a polymer main chain can also be used.

  Also, metal complexes of 8-quinolinol derivatives such as tris (8-quinolinol) aluminum (Alq), tris (5,7-dichloro-8-quinolinol) aluminum, tris (5,7-dibromo-8-quinolinol) aluminum. Tris (2-methyl-8-quinolinol) aluminum, tris (5-methyl-8-quinolinol) aluminum, bis (8-quinolinol) zinc (Znq), and the like, and the central metals of these metal complexes are In, Mg, Metal complexes replaced with Cu, Ca, Sn, Ga or Pb can also be used as the electron transport material. In addition, metal-free or metal phthalocyanine, or those having terminal ends substituted with an alkyl group or a sulfonic acid group can be preferably used as the electron transporting material. Distyrylpyrazine derivatives can also be used as electron transport materials, and inorganic semiconductors such as n-type-Si and n-type-SiC are also used as electron transport materials in the same manner as the hole injection layer and hole transport layer. I can do it. Although there is no restriction | limiting in particular about the film thickness of an electron carrying layer, Usually, 5 nm-about 5 micrometers, Preferably it is 5-200 nm. The electron transport layer may have a single layer structure composed of one or more of the above materials.

  An electron transport layer having a high n property doped with impurities can also be used. Examples thereof include JP-A-4-297076, JP-A-10-270172, JP-A-2000-196140, JP-A-2001-102175, J. Pat. Appl. Phys. 95, 5773 (2004), and the like. It is preferable to use such an electron transport layer having a high n property because an element with lower power consumption can be manufactured. The electron transport layer can also be formed by thinning the electron transport material by a known method such as wet coating or vacuum deposition.

As the second pixel electrode, an electrode material made of a metal having a small work function (4 eV or less) (referred to as an electron injecting metal), an alloy, an electrically conductive compound, or a mixture thereof is used. Specific examples of such electrode materials include sodium, sodium-potassium alloy, magnesium, lithium, magnesium / copper mixture, magnesium / silver mixture, magnesium / aluminum mixture, magnesium / indium mixture, aluminum / aluminum oxide (Al ₂ O ₃ ) Mixtures, indium, lithium / aluminum mixtures, rare earth metals and the like. Among these, from the point of durability against electron injection and oxidation, etc., a mixture of an electron injecting metal and a second metal which is a stable metal having a larger work function than this, for example, a magnesium / silver mixture, Suitable are a magnesium / aluminum mixture, a magnesium / indium mixture, an aluminum / aluminum oxide (Al ₂ O ₃ ) mixture, a lithium / aluminum mixture, aluminum and the like. The cathode can be produced by forming a thin film of these electrode materials by a method such as vapor deposition or sputtering. The sheet resistance as the cathode is preferably several hundred Ω / □ or less, and the film thickness is usually selected in the range of 10 nm to 5 μm, preferably 50 to 200 nm. In order to transmit the emitted light, if either one of the first pixel electrode (anode) or the second pixel electrode (cathode) of the organic EL element is transparent or translucent, the emission luminance is improved, which is convenient. .

  In addition, after forming the metal with a thickness of 1 to 20 nm on the second pixel electrode, the conductive transparent material mentioned in the description of the first pixel electrode is formed thereon, so that a transparent or translucent second material is formed. A pixel electrode (cathode) can be manufactured, and by applying this, an element in which both the first pixel electrode (anode) and the second pixel electrode (cathode) are transmissive can be manufactured.

  The light emitting layer constituting the organic EL device of the present invention contains a known host compound and a known phosphorescent compound (also referred to as a phosphorescent compound) in order to increase the luminous efficiency of the light emitting layer. Is preferred.

  The host compound is a compound contained in the light-emitting layer, the mass ratio in the layer is 20% or more, and the phosphorescence quantum yield of phosphorescence emission is 0.1 at room temperature (25 ° C.). Is defined as less than a compound. The phosphorescence quantum yield is preferably less than 0.01. A plurality of host compounds may be used in combination. By using a plurality of types of host compounds, it is possible to adjust the movement of charges, and the organic EL element can be made highly efficient. In addition, by using a plurality of phosphorescent compounds, it is possible to mix different light emission, thereby obtaining an arbitrary emission color. White light emission is possible by adjusting the kind of phosphorescent compound and the amount of doping, and can also be applied to illumination and backlight.

  As these host compounds, compounds having a hole transporting ability and an electron transporting ability, preventing emission light from being increased in wavelength, and having a high Tg (glass transition temperature) are preferable. Known host compounds include, for example, JP-A Nos. 2001-257076, 2002-308855, 2001-313179, 2002-319491, 2001-357777, and 2002-334786. Gazette, 2002-8860, 2002-334787, 2002-15871, 2002-334788, 2002-43056, 2002-334789, 2002-75645 2002-338579, 2002-105445, 2002-343568, 2002-141173, 2002-352957, 2002-203683, 2002-363227 2002-231453, 2003-3165, 2002-234888, 2003-27048, 2002-255934, 2002-260861, 2002-280183, Examples thereof include compounds described in 2002-299060, 2002-302516, 2002-305083, 2002-305084, 2002-308837 and the like.

  In the case of having a plurality of light emitting layers, it is preferable that 50% by mass or more of the host compound in each layer is the same compound because it is easy to obtain a uniform film property over the entire organic layer. It is more preferable that the light emission energy is 2.9 eV or more because it is advantageous in efficiently suppressing energy transfer from the dopant and obtaining high luminance. Phosphorescence emission energy means the peak energy of the 0-0 band of phosphorescence emission when the photoluminescence of a deposited film of 100 nm is measured on a substrate with a host compound.

  The host compound has a phosphorescence emission energy of 2.9 eV or more and a Tg of 90 ° C. or more in consideration of deterioration of the organic EL device over time (decrease in luminance and film properties), market needs as a light source, and the like. Preferably there is. That is, in order to satisfy both luminance and durability, it is preferable that phosphorescence emission energy is 2.9 eV or more and Tg is 90 ° C. or more. Tg is more preferably 100 ° C. or higher.

  A phosphorescent compound (phosphorescent compound) is a compound in which light emission from an excited triplet is observed, is a compound that emits phosphorescence at room temperature (25 ° C.), and has a phosphorescence quantum yield of 25. The compound is 0.01 or more at ° C. When used in combination with the host compound described above, an organic EL device with higher luminous efficiency can be obtained.

  The phosphorescent compound according to the present invention preferably has a phosphorescence quantum yield of 0.1 or more. The phosphorescent quantum yield can be measured by the method described in Spectroscopic II, page 398 (1992 version, Maruzen) of Experimental Chemistry Course 4 of the 4th edition. Although the phosphorescence quantum yield in a solution can be measured using various solvents, the phosphorescence quantum yield used in the present invention only needs to achieve the phosphorescence quantum yield in any solvent.

  There are two types of light emission of the phosphorescent compound in principle. One is the recombination of the carrier on the host compound to which the carrier is transported to generate an excited state of the host compound, and this energy is transferred to the phosphorescent compound. The energy transfer type, in which light emission from the phosphorescent compound is obtained by moving to the phosphorescent compound, and the other is that the phosphorescent compound becomes a carrier trap, resulting in recombination of the carriers on the phosphorescent compound and from the phosphorescent compound. Although it is a carrier trap type in which light emission can be obtained, in any case, it is a condition that the excited state energy of the phosphorescent compound is lower than the excited state energy of the host compound.

  The phosphorescent compound can be appropriately selected from known compounds used for the light emitting layer of the organic EL device. The phosphorescent compound is preferably a complex compound containing a group 8-10 metal in the periodic table of elements, more preferably an iridium compound, an osmium compound, or a platinum compound (platinum complex compound), rare earth Of these, iridium compounds are the most preferred.

  In the present invention, the phosphorescence emission maximum wavelength of the phosphorescent compound is not particularly limited, and can be obtained in principle by selecting a central metal, a ligand, a ligand substituent, and the like. The emission wavelength can be changed.

  The light emission color of the organic EL device of the present invention and the compound according to the present invention is shown in FIG. 4.16 on page 108 of “New Color Science Handbook” (edited by the Japan Color Society, University of Tokyo Press, 1985). It is determined by the color when the result measured with the total CS-1000 (manufactured by Konica Minolta Sensing) is applied to the CIE chromaticity coordinates.

The white element referred to in the present invention means that the chromaticity in the CIE1931 color system at 1000 cd / m ² is X = 0.33 ± 0.07 when the front luminance at 2 ° C. viewing angle is measured by the above method. It is in the region of Y = 0.33 ± 0.07.

  The external extraction efficiency at room temperature of light emission of the organic EL device of the present invention is preferably 1% or more, more preferably 5% or more. Here, the external extraction quantum efficiency (%) = the number of photons emitted to the outside of the organic EL element / the number of electrons sent to the organic EL element × 100.

  In addition, a hue improvement filter such as a color filter may be used in combination, or a color conversion filter that converts the emission color from the organic EL element into multiple colors using a phosphor may be used in combination. In the case of using a color conversion filter, the λmax of light emission of the organic EL element is preferably 480 nm or less.

  The organic EL device of the present invention preferably uses the following method in combination in order to efficiently extract light generated in the light emitting layer. The organic EL element emits light inside a layer having a refractive index higher than that of air (refractive index is about 1.7 to 2.1), and only about 15% to 20% of the light generated in the light emitting layer can be extracted. It is generally said that there is no. This is because the light incident on the interface (interface between the transparent substrate and air) at an angle θ greater than the critical angle causes total reflection and cannot be taken out of the element, or the transparent electrode or light emitting layer and the transparent substrate This is because the light undergoes total reflection between them, the light is guided through the transparent electrode or the light emitting layer, and as a result, the light escapes in the direction of the side surface of the device.

  As a technique for improving the light extraction efficiency, for example, a method of forming irregularities on the surface of the transparent substrate to prevent total reflection at the interface between the transparent substrate and the air (US Pat. No. 4,774,435). A method for improving efficiency by providing a substrate with a light condensing property (JP-A-63-314795). A method of forming a reflective surface on the side surface of an element (Japanese Patent Laid-Open No. 1-220394). A method of forming an antireflection film by introducing a flat layer having an intermediate refractive index between a substrate and a light emitter (Japanese Patent Laid-Open No. 62-172691). A method of introducing a flat layer having a lower refractive index than the substrate between the substrate and the light emitter (Japanese Patent Laid-Open No. 2001-202827). There is a method of forming a diffraction grating between any one of the substrate, the transparent electrode layer, and the light emitting layer (including between the substrate and the outside) (Japanese Patent Laid-Open No. 11-283951).

  In the present invention, these methods can be used in combination with an organic EL element. However, a method of introducing a flat layer having a lower refractive index than the substrate between the substrate and the light emitter, or a substrate, a transparent electrode layer, A method of forming a diffraction grating between any layers of the light emitting layer (including between the substrate and the outside) can be suitably used. In the present invention, by combining these means, it is possible to obtain an element having higher luminance or durability.

  When a low refractive index medium is formed between the transparent electrode and the transparent substrate with a thickness longer than the wavelength of light, the light extracted from the transparent electrode has a higher extraction efficiency to the outside as the refractive index of the medium is lower. . Examples of the low refractive index layer include aerogel, porous silica, magnesium fluoride, and a fluorine-based polymer. Since the refractive index of the transparent substrate is generally about 1.5 to 1.7, the low refractive index layer preferably has a refractive index of about 1.5 or less. Further, it is preferably 1.35 or less. The thickness of the low refractive index medium is preferably at least twice the wavelength in the medium. This is because the effect of the low refractive index layer is diminished when the thickness of the low refractive index medium is about the wavelength of light and the electromagnetic wave that has exuded by evanescent enters the substrate. The method of introducing a diffraction grating into an interface or any medium that causes total reflection is characterized by a high effect of improving light extraction efficiency. This method is generated from the light emitting layer by utilizing the property that the diffraction grating can change the direction of light to a specific direction different from refraction by so-called Bragg diffraction such as first-order diffraction and second-order diffraction. Of the light, the light that cannot go out due to total reflection between layers, etc. is diffracted by introducing a diffraction grating into any layer or medium (inside a transparent substrate or transparent electrode) , Trying to extract light out. The introduced diffraction grating desirably has a two-dimensional periodic refractive index. This is because light emitted from the light-emitting layer is randomly generated in all directions, so in a general one-dimensional diffraction grating having a periodic refractive index distribution only in a certain direction, only light traveling in a specific direction is diffracted. The light extraction efficiency does not increase so much. However, by making the refractive index distribution a two-dimensional distribution, light traveling in all directions is diffracted, and light extraction efficiency is increased.

  As described above, the position where the diffraction grating is introduced may be in any of the layers or in the medium (in the transparent substrate or the transparent electrode), but is preferably in the vicinity of the organic light emitting layer where light is generated. At this time, the period of the diffraction grating is preferably about 1/2 to 3 times the wavelength of light in the medium. The arrangement of the diffraction grating is preferably two-dimensionally repeated, such as a square lattice, a triangular lattice, or a honeycomb lattice.

  Furthermore, the organic EL device of the present invention can be processed so as to provide, for example, a microlens array-like structure on the light extraction side of the substrate in order to efficiently extract light generated in the light emitting layer, or so-called condensing light. By combining with the sheet, the luminance in the specific direction can be increased by collecting light in a specific direction, for example, in the front direction with respect to the element light emitting surface. As an example of the microlens array, quadrangular pyramids having a side of 30 μm and an apex angle of 90 degrees are two-dimensionally arranged on the light extraction side of the substrate. One side is preferably 10 μm to 100 μm. If it becomes smaller than this, the effect of diffraction will generate | occur | produce and color, and if too large, thickness will become thick and is not preferable.

  As the condensing sheet, for example, a sheet that is put into practical use in an LED backlight of a liquid crystal display device can be used. As such a sheet, for example, a brightness enhancement film (BEF) manufactured by Sumitomo 3M Limited can be used. As the shape of the prism sheet, for example, a substrate may be formed with a Δ-shaped stripe having an apex angle of 90 degrees and a pitch of 50 μm, or the apex angle is rounded and the pitch is changed randomly. Other shapes may be used. Moreover, in order to control the light emission angle from a light emitting element, you may use a light-diffusion plate and a film together with a condensing sheet. For example, a diffusion film (light-up) manufactured by Kimoto Co., Ltd. can be used.

  As an example of a method for producing the organic EL element of the present invention, a method for producing an organic EL composed of a first pixel electrode / a light emitting layer / an electron transport layer / a second pixel electrode will be described. Although what was applied is shown, it is not limited to this range and may be used for various functional layers.

<Production of transparent gas barrier film substrate>
As a substrate, on a polyethylene terephthalate film having a thickness of 100 μm (a film made by Teijin-Dyupon Co., Ltd., hereinafter abbreviated as PET), a low-density layer, a medium-density layer, a high-density layer under the following atmospheric pressure plasma discharge treatment apparatus and discharge conditions A transparent gas barrier film in which three layers of a density layer and a medium density layer were laminated was produced.

(Atmospheric pressure plasma discharge treatment equipment)
FIG. 7 is a structural cross-sectional view of an atmospheric pressure plasma discharge treatment apparatus. The counter electrode includes a roll rotating electrode 35 and a plurality of rectangular tube electrodes 36, and further includes an electric field applying means 40, a gas supply means 50, an electrode temperature adjusting means 60, and the like.

  A set of a roll rotating electrode 35 and a plurality of rectangular tube electrodes 36 coated with a dielectric was prepared as follows.

  The roll rotating electrode 35 serving as the first electrode is coated with a high-density, high-adhesion alumina sprayed film by an atmospheric plasma method on a titanium alloy T64 jacket roll metal base material having cooling means by cooling water, The roll diameter was set to 1000 mmφ. On the other hand, the square electrode 36 of the second electrode is formed by coating a hollow rectangular tube titanium alloy T64 with a dielectric similar to the above with a thickness of 1 mm under the same conditions, and opposing square tube type fixed electrode groups. It was.

Twenty-four square tube electrodes 36 are arranged around the roll rotation electrode 35 with a counter electrode gap of 1 mm. The total discharge area of the square tube type fixed electrode group was 150 cm (length in the width direction) × 4 cm (length in the transport direction) × 24 (number of electrodes) = 14400 cm ² .

  During the plasma discharge, the first electrode (roll rotating electrode 35) and the second electrode (square tube fixed electrode 36 group) are adjusted and kept at 80 ° C., and the roll rotating electrode 35 is rotated by a drive to form a thin film. went. Of the 24 rectangular tube-shaped fixed electrodes 36, 4 from the upstream side are used for forming the following first layer (low density layer 1), and the following 6 are used for forming the following second layer (medium density layer 1). For film formation, the following 8 lines are used for film formation of the third layer (high density layer 1), and the remaining 6 lines are used for film formation of the fourth layer (medium density layer 2). And 4 layers were stacked in one pass. This condition was further repeated twice to produce a transparent gas barrier film.

(First layer: low density layer 1)
Plasma discharge was performed under the following conditions to form a low density layer 1 having a thickness of about 90 nm.

<Gas conditions>
Discharge gas: Nitrogen gas 94.8% by volume
Thin film forming gas: hexamethyldisiloxane (hereinafter abbreviated as HMDSO)
(Vaporized by mixing with nitrogen gas in a Lintec vaporizer) 0.2% by volume
Additive gas: Oxygen gas 5.0% by volume
<Power supply conditions: Only the power supply on the first electrode side was used>
1st electrode side Power supply type
Frequency 80kHz
Output density 10W / cm ²
The density of the formed first layer (low density layer) was 1.90 as a result of measurement by the X-ray reflectivity method using MXP21 manufactured by Mac Science.

(Second layer: Medium density layer 1)
Plasma discharge was performed under the following conditions to form a medium density layer 1 having a thickness of about 90 nm.

<Gas conditions>
Discharge gas: Nitrogen gas 94.9% by volume
Thin film forming gas: hexamethyldisiloxane (hereinafter abbreviated as HMDSO)
(Vaporized by mixing with nitrogen gas in a Lintec vaporizer) 0.1% by volume
Additive gas: Oxygen gas 5.0% by volume
<Power supply conditions: Only the power supply on the first electrode side was used>
1st electrode side Power supply type
Frequency 80kHz
Output density 10W / cm ²
The density of the formed second layer (medium density layer) was 2.05 as a result of measurement by the X-ray reflectivity method using MXP21 manufactured by MacScience.

(Third layer: High-density layer 1)
Plasma discharge was performed under the following conditions to form a high-density layer 1 having a thickness of about 90 nm.

<Gas conditions>
Discharge gas: Nitrogen gas 94.9% by volume
Thin film forming gas: hexamethyldisiloxane (hereinafter abbreviated as HMDSO)
(Vaporized by mixing with nitrogen gas in a Lintec vaporizer) 0.1% by volume
Additive gas: Oxygen gas 5.0% by volume
<Power supply conditions>
1st electrode side Power supply type
Frequency 80kHz
Output density 10W / cm ²
Second electrode side Power supply type High frequency power supply manufactured by Pearl Industrial Co., Ltd.
Frequency 13.56MHz
Output density 10W / cm ²
The density of the formed third layer (high density layer) was 2.20 as a result of measurement by the X-ray reflectivity method using MXP21 manufactured by MacScience.

(Fourth layer: Medium density layer 2)
The medium density layer 2 was formed under the same conditions as the second layer (medium density layer 1).

(5th to 12th layers)
This was repeated twice under the same conditions as the formation of the first to fourth layers (1 unit) to produce a transparent gas barrier film.

As a result of measuring the water vapor transmission rate by a method based on JISk7129B, it was 10 ⁻³ g / m ² / day or less.

The oxygen transmission rate was measured by a method based on JISk7126B. As a result, it was 10 ⁻³ g / m ² / day or less.

<Formation of first pixel electrode>
Next, on the gas barrier film substrate, ITO (indium tin oxide) is formed in a stripe shape having a film thickness of 120 nm, a width of 100 μm, and an interelectrode distance of 10 μm by a film forming method such as sputtering, vapor deposition, or ion plating through a mask. The first pixel electrode was patterned on the substrate K.

<Formation of partition wall layer>
As shown in FIG. 4, a non-photosensitive polyimide partition wall 205 (width 20 μm, thickness 2.0 μm) is ink-jetted on the film substrate K on which the first pixel electrode 202 is formed so as to be orthogonal to the striped ITO transparent electrode. Formed by the law.

<Charge removal treatment process>
A roll-shaped strip-shaped flexible sheet on which the first pixel electrode 202 and the partition wall 205 are formed is fed out and subjected to a charge removal process.

  The charge removal treatment is roughly classified into a light irradiation method and a corona discharge method, and the light irradiation method generates weak ions and the corona discharge method generates air ions by corona discharge. The air ions are attracted to the charged object to compensate for the opposite polarity charge and neutralize static electricity. A static eliminator using corona discharge or a static eliminator using soft X-rays can be used.

  In this embodiment, a static eliminator using weak X-rays was used. By this process, the substrate is removed from the charge, so that dust adhesion and dielectric breakdown are prevented, so that the yield of the elements can be improved.

<Formation of light emitting layer>
[Image forming apparatus]
Using the image forming apparatus 101 by the electrostatic attraction type droplet discharge method shown in FIG. 2, using the roll-like strip-shaped flexible sheet substrate on which the first pixel electrode 202 and the partition 205 of ITO shown in FIG. 4 are formed, The light emitting layer 203 was formed in a region sandwiched between the partition walls 205 on the first pixel electrode 202.

  The application conditions of the electrostatic attraction type droplet discharge device used are shown below.

Nozzle diameter of nozzle electrode: 4 μm
Bias voltage between nozzle electrode and counter electrode: 450V
Distance between nozzle tip and substrate surface: 100 μm
Gas type, pressure: atmospheric pressure in N ₂ atmosphere The light emitting layer is composed of 1% by mass of red dopant material Btp ₂ Ir (acac) and green dopant material Ir (ppy) _{3 with} respect to polyvinyl carbazole (PVK) as a host material. Is dissolved in 1.2-dichloroethane so that the total solid concentration of PVK and the three dopants is 1% by mass, respectively, and 2% by mass of blue dopant material FIr (pic) is 3% by mass. Solution. The surface tension of the light emitting layer forming coating solution was 32 mN / m (manufactured by Kyowa Interface Chemical Co., Ltd .: surface tension meter CBVP-A3).

  Using this solution as a coating solution, a film is formed on the first pixel electrode using an electrostatic suction type droplet discharge device so that the thickness after drying becomes 100 nm, and then dried at 60 ° C. using a drying furnace. Then, heat treatment was continuously performed at 120 ° C. to form a light emitting layer.

  The structural formula of the dopant material used is shown below.

<Formation of electron transport layer, cathode, sealing film>
As an example of a post-process after the light emitting layer forming step, a LiF layer having a thickness of 0.5 nm was deposited on the organic EL layer forming region under a vacuum of 5 × 10 ⁻⁴ Pa. Subsequently, an aluminum layer having a thickness of 100 nm is similarly deposited on the region including the organic EL layer region and the electrode lead-out region. After forming in this order, a sputtering method, a plasma CVD method, an ion plate are formed in regions other than the region to be the electrode. An inorganic film such as SiO _x , SiN _x, or a composite film was formed as a 300 nm sealing film using a ting method or the like and wound. Note that a stress relaxation layer may be formed by vapor deposition or vapor deposition polymerization before the inorganic film is formed, or a low stress inorganic film may be formed by plasma CVD or the like.

  Subsequently, the film substrate was coated with a UV curable epoxy resin (UV resin XNR5570-B1 manufactured by Nagase ChemteX Corp.) as a sealing adhesive in a portion other than the electrode terminal portion by die coating under an inert gas. Then, a resin film having gas barrier properties was pressure-bonded and bonded, and then a UV lamp was irradiated from the cathode side to adhere the resin film.

  The element manufactured in this example has white light emission, which can be used as a lighting device, and according to the present invention, a low-cost and high-productivity lighting production facility can be provided.

  About the obtained organic EL element, the voltage of 10V was applied to the organic EL element, and the light emission state of the light emission part was observed. As a result of visual observation, good light emission was observed on the entire surface of all the light emitting portions.

  The manufacturing method of the present invention enables patterning without wasting the organic functional layer coating solution.

FIGS. 1A and 1B are diagrams illustrating an organic EL element, in which FIG. 1A is a cross-sectional side view of a main part, and FIG. 1 is a schematic configuration diagram of an image recording apparatus using a sheet-like substrate. 1 is a schematic configuration diagram of an image recording apparatus using a flexible substrate. It is a figure which shows the positional relationship of the 1st pixel electrode 202 formed on the board | substrate, the partition 205, and the nozzle 21, and the relative relationship of the electric potential in a pixel electrode area | region and a non-pixel electrode area | region. FIG. 3 shows a cross-sectional view of the liquid ejection device along the nozzle. FIGS. 5A and 5B are explanatory diagrams showing a relationship between a solution ejection operation and a voltage applied to the solution, in which FIG. 5A shows a state in which ejection is not performed in the non-pixel electrode unit, and FIG. The discharge state in is shown. It is a composition sectional view of an atmospheric pressure plasma discharge treatment device.

Explanation of symbols

DESCRIPTION OF SYMBOLS 20 Electrostatic suction droplet discharge apparatus 21 Nozzle electrode 23 Counter electrode 101 Image recording apparatus 202 1st pixel electrode pattern 203 Organic light emitting layer 204 2nd pixel electrode 205 Partition K Substrate

Claims (6)

In a method of manufacturing an organic electroluminescence element having at least a first pixel electrode, an organic functional layer formed on the first pixel electrode, and a second pixel electrode formed on the organic functional layer,
An organic substrate for forming the organic functional layer is formed on a substrate on which the first pixel electrode is formed and on which a partition wall for partitioning a pixel electrode region and forming a non-pixel electrode region is formed on the first pixel electrode. Supported on the lower electrode arranged opposite to the nozzle electrode of the electrostatic suction type droplet discharge device that discharges the functional layer coating liquid from the nozzle,
By relatively moving the substrate and the droplet discharge device so that the position of the substrate facing the nozzle moves in a state where a predetermined voltage is applied between the nozzle electrode and the lower electrode,
By the electric field strength difference based on the presence or absence of the partition between the nozzle electrode and the lower electrode,
A method of manufacturing an organic electroluminescence element, wherein an organic functional layer coating solution is selectively discharged from the nozzle to the pixel electrode region.   2. The method of manufacturing an organic electroluminescent element according to claim 1, wherein the organic functional layer formed by the organic functional layer coating liquid is any one of a carrier injection layer, a carrier transport layer, and a light emitting layer. .   3. The method of manufacturing an organic electroluminescent element according to claim 1, further comprising at least one charge removing step immediately before discharging the organic functional layer coating solution.   The nozzle diameter of the said nozzle is 20 micrometers or less, The manufacturing method of the organic electroluminescent element in any one of Claims 1-3 characterized by the above-mentioned.   The nozzle diameter of the said nozzle is 8 micrometers or less, The manufacturing method of the organic electroluminescent element in any one of Claims 1-3 characterized by the above-mentioned. Method of manufacturing an organic electroluminescence device according to any one of claim 1 to 3, nozzle diameter of the nozzle, characterized in that it is 4μm or less.

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