JP5029082B2 - Method for manufacturing organic electroluminescence device - Google Patents

Description

  The present invention relates to a method for manufacturing an organic electroluminescence device.

In recent years, an organic electroluminescence device using an organic electroluminescence element as a pixel has been developed. Organic electroluminescence elements are roughly classified into low molecular weight and high molecular weight. The low molecular organic electroluminescence element is mainly formed by a vacuum deposition method, and the high molecular organic electroluminescence element is mainly formed by a spin coating method or an ink jet method. In particular, the ink jet method is very effective as a means that allows simple and fine patterning without wasting materials (see, for example, Patent Documents 1 and 2).
JP 2002-231447 A Japanese Patent Laid-Open No. 2005-100954

  In the ink jet method, there is an optimum range for the viscosity of the solution to be ejected, and ejection within this range is important for stable and uniform film formation. For example, Patent Document 1 describes that the solution viscosity that can be stably discharged without causing clogging of the discharge nozzle of the inkjet head is preferably about 2 to 20 cps, and particularly preferably about 7 to 10 cps. However, when the solute is a polymer, the viscosity is often greater than 20 cps, making it difficult to select a polymer and a solvent. Although a method of decreasing the viscosity by reducing the concentration of the solute is conceivable, in that case, it is necessary to apply several times and the process becomes complicated.

  Patent Document 2 discloses a method in which EDOT, which is a monomer of PEDOT (a material for forming a hole injection layer), and a polymerization catalyst such as iron chloride III are discharged by a droplet discharge method and polymerized on a substrate. In this case, since the monomer and the polymerization catalyst are low molecules, the viscosity in the solution state is also low, and the above problem can be solved. However, in the organic electroluminescence device, the remaining polymerization catalyst deteriorates performance, which is not preferable.

  Note that Patent Document 2 describes an ink jet method using a piezo method, but the above-described problems are ink jet methods other than the piezo method, and droplets other than the ink jet method in which a film is formed by discharging a droplet. This is a common problem with the discharge method.

  The present invention has been made in view of such circumstances, and when forming a hole injection layer by a wet film formation method, the viscosity of the solution can be lowered to ensure stable ejection performance, and the light emission characteristics are deteriorated. Another object of the present invention is to provide a method of manufacturing an organic electroluminescence device that can prevent a decrease in service life. It is another object of the present invention to provide an electronic device with high reliability and excellent light emission characteristics by including such an organic electroluminescence device.

In order to solve the above problems, a method for producing an organic electroluminescence device of the present invention includes a functional layer composed of two or more layers including a hole injection layer and a light emitting layer, and a pair of electrodes sandwiching the functional layer. The hole injection layer forming step comprises: forming a vinyl group and a functional group having a hole injection function on one of the pair of electrodes. It comprises a step of disposing a prepared monomer or oligomer precursor by a droplet discharge method and polymerizing the precursor by heat treatment or ultraviolet irradiation treatment. As the precursor, for example, a precursor of an example described later is used. According to this method, since the hole injection layer is formed by a polymerization reaction of a monomer or oligomer having a low viscosity, even when a precursor containing each monomer or oligomer is discharged by a droplet discharge method, stable discharge performance is achieved. Can be secured. Further, since the hole injection layer is crosslinked without a polymerization catalyst by a radical reaction of a vinyl group, the deterioration of the light emission characteristics due to the catalyst impurities and the decrease in the lifetime of the organic electroluminescence element do not occur.

  In the present invention, the precursor preferably contains any one or two or more monomers or oligomers of the following formulas (1) to (12). According to this method, a hole injection layer with high hole injection efficiency can be formed. Formulas (1) to (4) are monofunctional monomers or oligomers containing one vinyl group, and formulas (5) to (8) are bifunctional monomers or two vinyl groups. It is an oligomer, and formulas (9) to (12) are trifunctional monomers or oligomers containing three vinyl groups.

  Embodiments of the present invention will be described below with reference to the drawings. Such an embodiment shows one aspect of the present invention and does not limit the present invention. In the following embodiments, various shapes, combinations, and the like of the constituent members are examples, and various modifications can be made based on design requirements and the like without departing from the gist of the present invention. Moreover, in the following drawings, in order to make each structure easy to understand, an actual structure and a scale, a number, and the like in each structure are different.

  FIG. 1 is a schematic configuration diagram of an organic EL device 1 which is an embodiment of the organic electroluminescence device of the present invention. The organic EL device 1 includes a first electrode 3, a functional layer 7, and a second electrode 8 on a substrate 2. The functional layer 7 includes two or more layers including the hole injection layer 4 and the light emitting layer 5, and the organic electroluminescent element 9, which is a light emitting element, is formed by the first electrode 3, the functional layer 7, and the second electrode 8. (Hereinafter, “electroluminescence” is abbreviated as “EL”). In the present embodiment, the first electrode 3 is an anode and the second electrode 8 is a cathode, but the first electrode 3 may be a cathode and the second electrode 8 may be an anode. In addition, ITO (indium tin oxide) is used as the first electrode 3, and an Al film is deposited on the co-deposited film of LiF (lithium fluoride) and Mag, Ca, or Ba as the second electrode 8. However, the material of the electrode is not limited to this.

  The hole injection layer 4 is formed by applying a precursor made of a monomer or oligomer having a vinyl group and a functional group having a hole injection function in the molecular skeleton onto the substrate 2 (more specifically, on the first electrode 3). And the precursor is polymerized by heat treatment or ultraviolet irradiation treatment. As the precursor, one containing any one or two or more monomers or oligomers of the following formulas (1) to (12) is used.

  The light emitting layer 5 includes a known light emitting material capable of emitting fluorescence or phosphorescence. Specifically, (poly) fluorene derivative (PF), (poly) paraphenylene vinylene derivative (PPV), polyphenylene derivative (PP), polyparaphenylene derivative (PPP), polyvinylcarbazole (PVK), polythiophene derivative, polymethyl Polysilanes such as phenylsilane (PMPS) are preferably used. In addition, these polymer materials include polymer materials such as perylene dyes, coumarin dyes, rhodamine dyes, rubrene, perylene, 9,10-diphenylanthracene, tetraphenylbutadiene, Nile red, coumarin 6, and quinacridone. It can also be used by doping a low molecular weight material such as. Alternatively, a low molecular material such as carbazole (CBP) can be doped with these low molecular dyes to form a light emitting layer. Tris-8-quinolinolato aluminum complex (Alq3) can also be added as an electron transporting layer as part of the light emitting layer.

  Next, a method for manufacturing the organic EL device 1 will be described with reference to FIG. First, as shown in FIG. 2A, a liquid material 4a containing a precursor of a hole injection material is disposed on the base 2 on which the first electrode 3 is formed. Then, the precursor is polymerized on the substrate 2 to form the hole injection layer 4 shown in FIG. The liquid material 4a is disposed on the substrate 2 (more specifically, on the first electrode 3) using a droplet discharge method. That is, the droplet discharge head of the droplet discharge apparatus is filled with the liquid material 4a, the nozzle of the droplet discharge head is opposed to the substrate 2, and the droplet discharge head and the substrate 2 are relatively moved while moving the droplet discharge head. The liquid material 4a in which the liquid amount per droplet is controlled is discharged onto the first electrode 3. Here, since the precursor of the hole injection material is a monomer or oligomer having a low molecular weight, the liquid material 4a in which the precursor is dissolved or dispersed is a liquid material having a low viscosity. Therefore, when discharging onto the substrate 2 by the droplet discharge head, the liquid material has good discharge performance.

  As a precursor of the hole injection material, not only an amine skeleton derivative such as triphenylamine but also a thiophene derivative, a pyrrole derivative, and a phenyl derivative can be used. Examples of these solvents include isopropyl alcohol (IPA), normal butanol, γ-butyrolactone, N-methylpyrrolidone (NMP), dimethylformamide (DMF), hexamethylphossolamide (HMPA), dimethyl sulfoxide (DMSO), Mention may be made of 1,3-dimethyl-2-imidazolidinone (DMI) and derivatives thereof, and glycol ethers such as carbitol acetate and butyl carbitol acetate.

  The polymerization reaction is caused by a radical reaction of a vinyl group contained in the precursor. When performing polymerization, the liquid material 4a is subjected to heat treatment or ultraviolet irradiation treatment as necessary. Thereby, the radical reaction (polymerization reaction) of a vinyl group is promoted. As a process for causing polymerization, an electron beam irradiation process or the like can be used in addition to the heat treatment and the ultraviolet irradiation process. However, heat treatment is preferable in view of the fact that the processing apparatus can be downsized and damage to the organic film is small. The heat treatment is desirably performed in an inert gas atmosphere. For example, the polymerization reaction can be promoted by performing a heat treatment at 200 ° C. for about 10 to 60 minutes in a nitrogen atmosphere.

  Next, as shown in FIG. 2C, the light emitting layer 5 is formed on the hole injection layer 4. As a method for forming the light emitting layer 5, a known wet film formation method represented by a spin coating method and a droplet discharge method can be used. Specifically, the polymer light-emitting material is dissolved or dispersed in an organic solvent, and disposed on the substrate 2 (more specifically, on the hole injection layer 4) by a spin coating method or a droplet discharge method. It can be formed by drying. Since the hole injection layer 4 has been polymerized by the previous polymerization reaction, it is a layer insoluble in organic solvents. Therefore, even if a solution of the polymer light emitting material is discharged onto the hole injection layer 4, the hole injection layer 4 is not redissolved by the solution.

  When the hole injection layer 4 and the light emitting layer 5 are formed by the above-described steps, the second electrode 8 is formed on the light emitting layer 5 as shown in FIG. An electron injecting and transporting layer or the like may be formed between the light emitting layer 5 and the second electrode 8 as necessary. Thus, the organic EL element 9 is completed.

  As described above, in this embodiment, the hole injection layer 4 is formed by a polymerization reaction of a monomer or oligomer having a low viscosity. Therefore, even when the precursor containing the monomer or oligomer is discharged by the droplet discharge method, stable discharge performance can be ensured. For example, in the case of this embodiment, it is easy to suppress the viscosity of the liquid material 4a within the range of 2 to 20 Ps, and stable ejection from the droplet ejection head is possible. Further, since the hole injection layer 4 is cross-linked without a polymerization catalyst by a radical reaction of a vinyl group, the light emission characteristics are not deteriorated due to catalyst impurities, and the lifetime of the organic EL element 9 is not reduced. Thereby, an organic EL device having excellent reliability can be provided.

[Example]
Next, examples of the present embodiment will be described. First, as a first example, a precursor of the following formula (13) was dissolved in DMF, and a film having a thickness of 50 nm to 60 nm was formed on a substrate on which a first electrode (anode) was formed by a droplet discharge method. . And the hole injection layer of the polymer film was formed by heat-treating the substrate in a nitrogen atmosphere at 200 ° C. for about 10 minutes to 60 minutes. The method for synthesizing the precursor of formula (13) is as shown in FIG. 3 (reference: Org. Lett. 2000, 2, 1423). In FIG. 3, the compound A was identified by mass spectrometry.

  Next, poly [(9,9-dioctylfluorenyl-2,7-diyl) -co- (1,4-benzo- {2,1 ′, 3} -thiadiazole)] is formed on the hole injection layer. A 1.8 wt% xylene solution (ADS133YE manufactured by ADS) was applied to a thickness of 60 nm to 80 nm by a spin coating method, and was subjected to a baking treatment at 130 ° C. for 30 minutes in a nitrogen atmosphere to form a light emitting layer.

Then, in a vacuum atmosphere with a degree of vacuum of 10 ⁻⁶ Torr (1.33 × 10 ⁻⁴ Pa), a 4 nm thick LiF layer, a 10 nm thick Ca layer, and a 200 nm thick Al layer are stacked by vacuum deposition. Then, the second electrode (cathode) was formed to complete the organic EL element.

  Next, as a second example, a precursor of the following formula (14) is dissolved in DMF, and formed into a film with a layer thickness of 50 nm to 60 nm on the substrate on which the first electrode (anode) is formed by a droplet discharge method. did. And the hole injection layer which consists of a polymer film was formed by heat-processing a base | substrate in 200 degreeC and about 10 minutes-60 minutes in nitrogen atmosphere. The method for synthesizing the precursor of formula (14) is as shown in FIG. 4 (reference: Org. Lett. 2000, 2, 1423). In FIG. 4, the compound B was identified by mass spectrometry.

  Next, poly [(9,9-dioctylfluorenyl-2,7-diyl) -co- (1,4-benzo- {2,1 ′, 3} -thiadiazole)] is formed on the hole injection layer. A 1.8 wt% xylene solution (ADS133YE manufactured by ADS) was applied to a thickness of 60 nm to 80 nm by a spin coating method, and was subjected to a baking treatment at 130 ° C. for 30 minutes in a nitrogen atmosphere to form a light emitting layer.

Then, in a vacuum atmosphere with a degree of vacuum of 10 ⁻⁶ Torr (1.33 × 10 ⁻⁴ Pa), a 4 nm thick LiF layer, a 10 nm thick Ca layer, and a 200 nm thick Al layer are stacked by vacuum deposition. Then, the second electrode (cathode) was formed to complete the organic EL element.

  Next, as a comparative example, a hole injection layer is not formed on the substrate on which the first electrode (anode) is formed, and poly [(9,9-dioctylfluorenyl-2,7-diyl) -co- (1.8-benzo- {2,1 ', 3} -thiadiazole)] (ADS133YE manufactured by ADS) was applied to a thickness of 60 nm to 80 nm by spin coating to a thickness of 60 nm to 80 nm, and in a nitrogen atmosphere. A baking process was performed at 130 ° C. for 30 minutes to form a light emitting layer.

Then, in a vacuum atmosphere with a degree of vacuum of 10 ⁻⁶ Torr (1.33 × 10 ⁻⁴ Pa), a 4 nm thick LiF layer, a 10 nm thick Ca layer, and a 200 nm thick Al layer are stacked by vacuum deposition. Then, the second electrode (cathode) was formed to complete the organic EL element.

  Next, the emission spectrum was measured about the organic EL element of Example 1, Example 2, and the comparative example which were manufactured in this way. As a result, an emission spectrum of about 560 nm was obtained in the organic EL elements of Example 1 and Example 2, and an emission spectrum of about 540 nm was obtained in the organic EL element of the comparative example.

Next, the organic EL elements of Examples 1, 2 and Comparative Example were driven at a constant current with an initial luminance of 800 cd / cm ² , and current efficiency and half-life of luminance were measured. As a result, the results shown in Table 1 were obtained. In Table 1, the comparative example is normalized as 1.

  From Table 1, it was found that the results superior to the comparative example were obtained in Example 1 and Example 2. In addition, Example 2 was superior to Example 1 in terms of current efficiency and life. This is presumably because the HOMO level of the side chain unit of the precursor used in Example 2 could be more easily injected from ITO as the anode than in Example 1.

[Image forming apparatus]
Next, an image forming apparatus which is a first embodiment of an electronic apparatus including the organic EL device of the present invention will be described. FIG. 5 is a schematic configuration diagram illustrating an image forming apparatus 100 including an organic EL device as a line head.

  The image forming apparatus 100 includes a photosensitive drum 16 as an image carrier in the vicinity of the travel path of the transfer medium 22. Around the photosensitive drum 16, an exposure device 15, a developing device 18, and a transfer roller 21 are sequentially arranged along the rotation direction of the photosensitive drum 16 (indicated by an arrow in the drawing). The photosensitive drum 16 is rotatably provided around the rotation shaft 17, and a photosensitive surface 16 </ b> A is formed on the outer peripheral surface of the photosensitive drum 16 at the central portion in the rotation axis direction. The exposure device 15 and the developing device 18 are arranged in a long axis shape along the rotation shaft 17 of the photosensitive drum 16, and the width in the long axis direction substantially coincides with the width of the photosensitive surface 16A.

  In this image forming apparatus 100, first, in the process of rotating the photosensitive drum 16, the surface of the photosensitive drum 16 (photosensitive surface 16 </ b> A) is positive (for example, positive) by a charging device (not shown) provided on the upstream side of the exposure device 15. Then, the exposure device 15 exposes the surface of the photosensitive drum 16 to form an electrostatic latent image LA on the surface. Further, the toner (developer) 20 is applied to the surface of the photosensitive drum 16 by the developing roller 19 of the developing device 18, and the toner image corresponding to the electrostatic latent image LA is formed by the electric attractive force of the electrostatic latent image LA. It is formed. The toner particles are positively (+) charged.

  After the toner image is formed by the developing device 18, the toner image comes into contact with the transfer medium 22 by further rotation of the photosensitive drum 16, and the transfer roller 21 reverses the polarity of the toner particles from the toner image from the back surface of the transfer medium 22. Charge (here, negative (−) charge) is applied, and accordingly, toner particles forming a toner image are attracted from the surface of the photosensitive drum 16 to the transfer medium 22, and the toner image is transferred to the surface of the transfer medium 22. Is transcribed.

  The exposure apparatus 15 includes a line head 1 having a plurality of organic EL elements 9 and an imaging optical element 12 having a plurality of lens elements 13 for imaging the light L emitted from the line head 1 at an erecting equal magnification. I have. The line head 1 and the imaging optical element 12 are held by a head case (not shown) while being aligned with each other, and are fixed on the photosensitive drum 16.

  The line head 1 includes a light emitting element array 10 in which a plurality of organic EL elements 9 are arranged along the rotation axis 17 of the photosensitive drum 16, and a drive element group including a drive element (not shown) that drives the organic EL elements 9. And a control circuit group 11 for controlling driving of these drive elements (drive element group). The organic EL element 9, the drive element group, and the control circuit group 11 are integrally formed on a long and thin element substrate (base) 2.

  The imaging optical element 12 is arranged (arranged) in a zigzag pattern in which the lens elements 13 having the same configuration as the SELFOC (registered trademark) lens element manufactured by Nippon Sheet Glass Co., Ltd. are arranged along the rotation axis 17 of the photosensitive drum 16. A lens element array 14 is provided.

  In this image forming apparatus 100, the organic EL element 9 formed on the line head 1 has the structure of the light emitting element of the present invention described above. Therefore, the image forming apparatus has high emission luminance and no exposure failure occurs.

[Organic EL display device]
Next, an organic EL display device that is a second embodiment of an electronic apparatus including the organic EL device of the present invention will be described. FIG. 6 is a schematic configuration diagram of an organic EL display device 200 including organic EL elements as pixels in a matrix.

  The organic EL display device 200 includes a circuit element unit 30 including a thin film transistor as a circuit element, a pixel electrode (first electrode) 3 serving as an anode, an organic functional layer 7 including a light emitting layer, and a counter electrode serving as a cathode. (Second electrode) 8, a sealing portion 32, and the like are provided.

  For example, a glass substrate is used as the substrate 2. As a substrate in the present invention, in addition to a glass substrate, various known substrates used for electro-optical devices and circuit substrates such as a silicon substrate, a quartz substrate, a ceramic substrate, a metal substrate, a plastic substrate, and a plastic film substrate are applied. The

  On the base 2, a plurality of pixel areas A as light emitting areas are arranged in a matrix, and when performing color display, for example, corresponding to each color of red (Red), green (Green), and blue (Blue). The pixel area A to be formed is formed in a predetermined arrangement. In each pixel region A, a pixel electrode 3 is arranged, and in the vicinity thereof, a signal line 42, a common power supply line 43, a scanning line 41, a scanning line for other pixel electrodes (not shown), and the like are arranged. As the planar shape of the pixel region A, an arbitrary shape such as a circle or an oval can be applied in addition to the rectangle shown in the figure.

  The sealing portion 32 prevents water and oxygen from entering and prevents the counter electrode 8 or the organic functional layer 7 from being oxidized, and includes a sealing substrate (or sealing can) 34 bonded to the base 2. The sealing substrate 34 is made of glass, metal, or the like, and the base 2 and the sealing substrate 34 are bonded together with a sealing agent. A desiccant is disposed inside the substrate 2, and an inert gas filling layer 33 filled with an inert gas is formed in a space formed between the substrates.

  In the pixel region A, a first thin film transistor 44 for switching in which a scanning signal is supplied to the gate electrode through the scanning line 41 and a holding for holding an image signal supplied from the signal line 42 through the thin film transistor 44. The capacitor cap, the driving second thin film transistor 45 to which the image signal held by the holding capacitor cap is supplied to the gate electrode, and the common supply line when electrically connected to the common power supply line 43 through the thin film transistor 45 A pixel electrode 3 into which a drive current flows from the electric wire 43 and an organic functional layer 7 sandwiched between the pixel electrode 3 and the counter electrode 8 are provided. The organic functional layer 7 includes a light emitting layer, and the organic EL element 9 which is a light emitting element includes the pixel electrode 3, the counter electrode 8, the organic functional layer 7, and the like.

  In the pixel area A, when the scanning line 41 is driven and the first thin film transistor 44 is turned on, the potential of the signal line 42 at that time is held in the holding capacitor cap, and the second capacitance is changed according to the state of the holding capacitor cap. The conductive state of the thin film transistor 45 is determined. In addition, a current flows from the common power supply line 43 to the pixel electrode 3 through the channel of the second thin film transistor 45, and further a current flows to the counter electrode 8 through the organic functional layer 7. And according to the electric current amount at this time, the organic functional layer 7 light-emits.

  In the organic EL display device 200, light emitted from the organic functional layer 7 to the base 2 side is transmitted through the circuit element unit 30 and the base 2 and emitted to the lower side (observer side) of the base 2. Light emitted from the functional layer 7 to the opposite side of the substrate 2 is reflected by the counter electrode 8, and the light passes through the circuit element unit 30 and the substrate 2 and is emitted to the lower side (observer side) of the substrate 2. (Bottom emission type). Note that light emitted from the counter electrode can be emitted by using a transparent material as the counter electrode 8 (top emission type). In this case, ITO, Pt, Ir, Ni, or Pd can be used as the transparent material for the counter electrode.

  In this organic EL display device 200, the organic EL element 9 formed in the pixel region A has the structure of the light emitting element of the present invention described above. Therefore, an organic EL display device with high emission luminance and capable of bright display is obtained.

It is a schematic structure figure showing one embodiment of an organic EL device. It is explanatory drawing of the manufacturing method of the same organic EL device. It is explanatory drawing of the synthesis | combining method of the precursor of hole injection material. It is explanatory drawing of the synthesis | combining method of the precursor of hole injection material. 1 is a schematic configuration diagram of an image forming apparatus that is a first embodiment of an electronic apparatus. It is a schematic block diagram of the organic electroluminescence display which is 2nd Embodiment of an electronic device.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Organic EL apparatus, 2 ... Base | substrate, 3 ... 1st electrode, 4 ... Hole injection layer, 4a ... Liquid material, 5 ... Light emitting layer, 7 ... Functional layer, 8 ... 2nd electrode, 100 ... Image forming apparatus ( Electronic device), 200 ... Organic EL display device (electronic device)

Claims (1)

A method for producing an organic electroluminescent device comprising a functional layer comprising two or more layers including a hole injection layer and a light emitting layer, and a pair of electrodes sandwiching the functional layer,
The step of forming the hole injection layer is a method in which a precursor made of a monomer or an oligomer having a vinyl group and a functional group having a hole injection function on one electrode of the pair of electrodes is a droplet discharge method. the place, look including the step of polymerizing by heat treatment or ultraviolet irradiation treatment of the precursor,
The manufacturing method of the organic electroluminescent apparatus characterized by using the precursor of a following formula as said precursor .

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