JP2004022434A - Organic electroluminescent element and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an organic electroluminescent element having a luminescent layer with excellent emission efficiency and durability, and easy to manufacture. <P>SOLUTION: This organic electroluminescent element is composed by sequentially stacking, on a substrate 1, a positive electrode 2, an organic electroluminescent layer 8A having at least the luminescent layer 4A, and a negative electrode 5. The luminescent layer 4A is formed with: a polymer luminescent material; a low-molecular-weight luminescent material containing a phenylcarbazole group and having a second emission wavelength different from a first emission wavelength of the polymer luminescent material; and a low-molecular-weight luminescent material having a third emission wavelength longer than the first and second emission wavelengths. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an organic electroluminescent device and a method for manufacturing the same, and in particular, an organic electroluminescent light emitting layer is mainly composed of a light emitting polymer material, and the light emitting layer contains a plurality of light emitting low molecular materials. Further, the present invention relates to an organic electroluminescent device having a light emitting layer capable of emitting light with high efficiency even at low voltage driving, and a method of manufacturing an organic electroluminescent device suitable for fine patterning of the light emitting layer.
[0002]
[Prior art]
2. Description of the Related Art Organic electroluminescent elements (hereinafter, also simply referred to as organic EL elements) are expected as display elements that have high-speed response and emit self-luminous light independent of the viewing angle with low power consumption. Applications to displays and the like are being studied.
As an in-vehicle audio display panel, an organic EL device of an area color system in which a mono color is partially combined has been put to practical use. For mobile phones, color display organic EL elements in which RGB fine elements (sub-pixels) are formed by patterning using a mask evaporation method have been put to practical use.
[0003]
Since full-color display is possible by combining display elements corresponding to red, green, and blue (RGB), various studies have been made on high-performance organic EL elements that can be driven at a low voltage and emit light of high luminance. ing.
FIG. 2 is a schematic cross-sectional view showing a basic configuration of an organic EL device as shown in a report by Tang et al. (Applied Physics Letters, 51 (12), 913-915 (1987)).
As shown in FIG. 1, an organic EL device 10 is obtained by sequentially laminating an anode 2 having a predetermined shape, an organic electroluminescent layer (hereinafter, also simply referred to as an organic EL layer) 8 and a cathode 5 on a transparent substrate 1. It is composed of
[0004]
The substrate 1 is made of, for example, glass.
The anode 2 is made of a transparent material having a large work function, for example, indium-tin oxide (hereinafter, also simply referred to as ITO).
The organic EL layer 8 includes, for example, the hole transport layer 3 and the light emitting layer 4. The organic EL layer 8 has various configurations such as a single-layer type composed of a single layer and a laminated type in which a plurality of different materials are laminated according to functions such as charge injection properties, charge transport properties, and luminescence properties. .
[0005]
An example of the hole transport layer 3 is an arylamine compound.
The organic material constituting the light-emitting layer 4 is widely used from conjugated and non-conjugated polymer materials having a fluorescent property to low molecular materials, metal complexes, and heavy metal complexes having a phosphorescent property and emitting light with very high efficiency. You. Depending on the material, a wet method such as coating from a solution or a dry method such as vacuum deposition is selected as these forming methods. An example of the electron-transporting light-emitting layer 4 is a tris (8-quinolinate) aluminum organometallic complex (hereinafter, also simply referred to as Alq3).
[0006]
As the cathode 5, a metal electrode made of, for example, an aluminum-magnesium alloy is formed.
When a predetermined voltage is applied between the anode 2 and the cathode 5 by the power supply 6, the holes injected from the anode 2 are injected into the light emitting layer 4 through the hole transport layer 3, while the electrons injected from the cathode 5 are injected. Moves in the light-emitting layer 4, and electrons and holes are combined in the light-emitting layer 4 to emit light 7.
The emitted light 7 is extracted outside through the transparent anode 2 and the transparent substrate 1. The luminescent color at this time depends on the luminescent color of the luminescent layer 4 and is monochromatic luminescence, and in the case of Alq3, it is green luminescence.
The emission color is selected depending on the dye that is doped in the emission layer 4.
Recently, Baldo et al. Reported a highly efficient light-emitting device using a green phosphorescent Ir complex fac-tris (2-phenylpyridine) iridium Ir (ppy) 3 (Applied Physics Letters, 74 (1) ), 4-6 (1999)). Here, a low molecular weight compound having N-phenylcarbazole 4,4′-N, N′-dicarbazolebiphenyl (CBP) is used as a host material of a light emitting material.
A device in which this phosphorescent material Ir (ppy) 3 is dispersed in a polymer light-emitting layer is reported by Yang et al. (Japanese Journal of Applied Physics, 39, L828-L829 (2000)). A high-efficiency device similar to a low-molecular device has been obtained with a device formed by vacuum deposition of a diazole compound.
[0007]
[Problems to be solved by the invention]
By the way, in order to extract emitted light to the outside and form a full-color display, it is necessary to configure one pixel (pixel) by combining three kinds of fine elements (sub-pixels) of red, green, and blue light emission (RGB).
[0008]
When a low molecular material is used for the light emitting layer 4, the light emitting layer 4 is formed by a dry method, for example, a vapor deposition method. Here, since a photolithography technique cannot be used, an evaporation method using a mask is used. A deposition mask having a fine pixel shape is arranged on the substrate 1 on which the light-emitting layer 4 is formed, and is moved and positioned with high precision (sub-pixel size) so as not to be in contact with the substrate 1 and to form no gap. It is necessary. However, if the pixel area (size) is reduced in order to enable high-definition display, it is extremely difficult to realize these, and there is a problem that a reduction in productivity is inevitable.
[0009]
On the other hand, when a polymer material is used for the light emitting layer 4, the light emitting layer 4 is formed by a wet method. It is relatively easy to form the light emitting layer 4 by a wet method. However, many polymer materials exhibit a hole transporting property, and a single light emitting layer 4 cannot secure sufficient characteristics. Therefore, a structure in which two layers are combined with a layer of a low molecular material having an electron transporting property is required, but it is not easy to form two layers by a vapor deposition method and a wet method. Further, there is a problem that it is difficult to form a layer of a polymer material having an electron transporting property on the light emitting layer 4 by a wet method.
[0010]
On the other hand, a single-layer light-emitting layer made of a polymer material having a hole-transport property is formed, and a low-molecular material having an electron-transport property and / or a low-molecular material having a hole-transport property are formed in the light-emitting layer. A method of dispersing and adding molecular materials has been proposed by Mori et al. (Proceedings of the 38th Joint Lecture Meeting on Applied Physics, 1086 (1991)). By selecting low-molecular materials, which are these light-emitting materials (hereinafter, also referred to as dyes), according to the light-emitting color, blue, green, and red sub-pixels are formed to achieve full color. .
[0011]
Here, oxadiazole compounds and triazole compounds are known as materials having an electron transporting property. However, these materials have high electron-transport properties and can improve luminous efficiency.However, these materials tend to be recombination sites themselves, easily form exciplexes having a short lifetime with polymer materials, and have high durability. There was a problem that the property could not be obtained.
[0012]
On the other hand, as a method of adding a dye, JP-A-7-235378 discloses an ink jet method, a printing method, and the like. On the other hand, the present applicant has proposed a method suitable for miniaturization in JP-A-2001-313166.
When sub-pixels are further miniaturized by this method, there is a problem that sub-micron overlap occurs between sub-pixels, and this improvement has been demanded.
[0013]
Therefore, the present invention solves the above-mentioned problems, and as a first object, provides an organic electroluminescence element having a light-emitting layer that has good luminous efficiency and excellent durability and is easily manufactured. A second object is to provide a method of manufacturing an organic electroluminescence element which forms a fine pixel pattern of the light emitting layer with high productivity.
[0014]
[Means for Solving the Problems]
As a means for achieving the above object, a first aspect of the present invention is an organic electroluminescent device in which a first electrode, an organic electroluminescent layer having at least a light emitting layer, and a second electrode are sequentially laminated on a substrate. In the luminescence element, the light emitting layer includes a polymer light emitting material, and a first low molecular light emitting material containing a phenylcarbazole group having a second emission wavelength different from the first emission wavelength of the polymer light emitting material. And a second low-molecular-weight light-emitting material having a third emission wavelength longer than the first and second emission wavelengths. Further, the second invention includes a step of forming a photoresist layer having a reverse tapered pattern on the first substrate, and a step of forming a dye portion on the first substrate exposed from the reverse tapered pattern. Forming a pixel electrode and a light emitting layer sequentially on a second substrate, and placing the first substrate on the second substrate with the photoresist layer side facing the light emitting layer side. And a step of heating the first substrate and the second substrate, which are in close contact with each other, and diffusing the dye portion into the light emitting layer corresponding to the pixel electrode to form a dye layer. And forming a common electrode on the dye layer after separating the first substrate from the second substrate. A method for manufacturing an organic electroluminescence device, comprising: .
[0015]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings by way of preferred examples. For the sake of simplicity, the same reference numerals are given to the same components, and the description thereof is omitted.
FIG. 1 is a schematic sectional view showing the basic structure of one embodiment of the organic EL device of the present invention.
The organic electroluminescent device 10A of the present invention is an organic electroluminescent device in which a transparent anode 2, an organic electroluminescent layer 8A having at least a light emitting layer 4A, and a cathode 5 are sequentially laminated on a transparent substrate 1. The light emitting layer 4A comprises a polymer light emitting material; a low molecular light emitting material containing a phenylcarbazole group having a second light emission wavelength different from the first light emission wavelength of the polymer light emitting material; And a low-molecular light emitting material having a third emission wavelength longer than the emission wavelength of No. 2.
[0016]
Examples of the polymer material constituting the main component of the light emitting layer 4A include a polyfluorene compound, a polyphenylenevinylene compound, a polythiophene compound, a polyvinylcarbazole compound, a polyvinylphenylcarbazole compound, a polyphenylcarbazole compound, a polybiphenylcarbazole compound, and a polyterphenylcarbazole compound. And polymers such as polycarbonate compounds and polyacetylene compounds. In addition, copolymers of these polymers and molecular groups having a charge injection function, a charge transport function, and a chromaticity improving function can be used.
[0017]
In order to transfer energy to a dye (low-molecular material described later) that diffuses into these polymer materials, the emission wavelength of the polymer material is desirably a short wavelength between the blue region and the ultraviolet region, and the peak wavelength is 490 nm or less. It is desirable that the energy gap be 2.5 eV or more. More preferably, the energy gap is set to 2.8 eV or more.
[0018]
For forming the above-mentioned polymer material layer, a usual wet method, that is, a spin coating method, a casting method, a dipping method, a spray method, a die coating method, an extrusion method, a Langmuir-Blodgett method, or the like can be used. . The thickness of the polymer material layer may be in the range of 5 to 200 nm, preferably in the range of 20 to 100 nm.
[0019]
An electron transporting material is added to the polymer material layer. An electron transporting material is indispensable for a polymer material having a high hole transporting property to maintain carrier injection and balance. However, compounds with high electron transport properties, such as oxadiazole compounds and triazole compounds, improve luminous efficiency but tend to be recombination sites themselves, and are likely to form short-lived exciplexes with polymer materials. Durability cannot be obtained, and separation and aggregation tend to occur. Further, the phenanthroline compound and the bathocuproin compound are easily crystallized due to their planar structure, and therefore, it is difficult to obtain durability.
[0020]
In this case, a low molecular material containing an N-phenylcarbazole group having a bipolar property and a stable behavior with respect to oxidation and reduction having a slightly low electron transport property but also having a hole transport property is added. Is preferred. Such a compound preferably has N-phenylcarbazole bonded to both ends of a biphenyl group and a terphenyl group. In addition, these materials are preferable because they have a property of easily transmitting excitation energy to other materials because their emission range is from ultraviolet to blue.
[0021]
FIG. 3 is a chemical structural formula of an example of a low molecular weight material containing an N-phenylcarbazole group.
As shown in the figure, when n = 2, the carrier transporting property has a bipolar property.
When n = 2, it is N, N′-dicarbazole-biphenyl (emission wavelength λmax = 420 nm).
Next, low-molecular-weight light-emitting materials that determine the emission color include fluorescent dyes, phosphorescent dyes, and organometallic complexes that have fluorescence and phosphorescence and emit red-green-blue (RGB). If it is, it can be used.
[0022]
As a red (hereinafter, also simply referred to as R) dye, a dye such as a porphyrin compound, a chlorin compound, a perylene compound, a dicyanopyran compound, a squarylium compound, a distyryl compound, a eurolysine compound, a coumarin compound, or an organometallic complex compound may be used. I can do it.
As the green (hereinafter, also simply referred to as G) dye, a dye such as a coumarin compound, a quinacridone compound, a quinolinol metal complex compound, or an organic metal complex compound can be used.
As the blue (hereinafter, also simply referred to as B) dye, a dye such as a distyrylaryl compound, a diarylamine compound, a triarylamine compound, tetraphenylbutadiene, perylene, a quinolinol metal complex compound, or an organometallic complex compound is used. I can do it.
[0023]
The above-mentioned organometallic complex preferably has a central metal composed of a white metal, and is selected from Ru, Rh, Pd, Os, Ir, and Pt. The ligands each take from 2 to 6 coordination, depending on the central metal. The coordinating elements include C, O, N, S and the like. Known ligands include quinolinate derivatives, benzoquinolinate derivatives, phenylpyridinate derivatives, benzothienylpyridinate derivatives, porphine derivatives, and the like.The emission colors differ depending on the interaction between the central metal and the ligand. Is obtained. A blue to red light-emitting material may be appropriately selected.
[0024]
FIG. 4 shows an example of the metal organic complex.
FIG. 4 is a chemical structural formula of a dye composed of a metal organic complex.
FIG. 4A shows that, when M = Ir and m = 3, fac-tris (2-phenylpyridinate-N, C ^{2 '} ) Indicates iridium, and the maximum emission wavelength λmax is 510 nm.
FIG. 4B shows that when M = Ir, n = 2, bis (2- (2′-benzo [4,5-α] thienyl) pyridinate-N, C ^{3 '} ) Iridium (acetyl acetate), and the maximum emission wavelength λmax is 616 nm. When M = Pt and n = 1, bis (2- (2′-benzo [4,5-α] thienyl) pyridinate-N, C ^{3 '} ) Platinum (acetyl acetate), and the maximum emission wavelength λmax is 610 nm.
[0025]
FIG. 4C shows that when M = Ir, n = 2, bis (2-phenylpyridinate-N, C ^{2 '} ) Represents iridium (acetyl acetate), and has a maximum emission wavelength λmax of 516 nm.
FIG. 4D shows that when M = Ir, n = 2, bis (4,6-di-fluorophenyl) -pyridinate-N, C ^{2 '} ) Indicates iridium (picolinate), and the maximum emission wavelength λmax is 475 nm.
Here, as the organic EL layer 8A, the light emitting layer 4A mainly made of a polymer material is formed. However, in order to form a more efficient organic EL element, the electrodes 2 and 5 may be connected to the light emitting layer 5 if necessary. A charge injection layer or a charge transport layer is provided between the layers 4A.
[0026]
Between the anode 2 and the light emitting layer 4A, a hole injection layer such as a mixture of a polythiophene compound / polystyrene sulfonate compound, a polyaniline compound or a phthalocyanine compound, and a hole transporting property containing a plurality of triarylamine groups in the molecule. A polymer layer is formed as needed.
Between the cathode 5 and the light emitting layer 4A, an aluminum quinolinolato complex such as BAlq, a hole blocking layer such as a bathocuproine compound, a phenanthroline compound or a triazole compound, an electron transport layer such as a quinolinol metal complex or an oxazole compound, an alkali metal, an alkali An electron injection layer such as an earth metal fluoride or oxide is formed as necessary.
As the cathode, an electrode made of a metal having a low work function such as Al, Mg, Li, Ca, Cs or the like, or an alloy thereof, and a transparent electrode as necessary are formed.
[0027]
Next, the function of the luminescent dye will be described.
When a plurality of light-emitting dyes (materials) are added and dispersed in the light-emitting layer 4A, the energy transfer from the excitation energy of the light-emitting material on the short wavelength side to the light-emitting material on the long wavelength side is used for the light-emitting material on the long wavelength side. Luminous efficiency can be increased. In this case, the greater the overlap between the emission spectrum of the light emitting material on the short wavelength side and the absorption spectrum of the light emitting material on the long wavelength side, the higher the efficiency of energy transfer.
[0028]
When the emission wavelength of the light-emitting base material (main component) is in the ultraviolet to blue region and the light-emitting dopant (addition component) is a red dye, the above-mentioned spectrum overlap is small and the energy gap is too large, so that the energy is too large. Is often not efficient. In such a case, the efficiency of energy transfer from blue to red can be improved by using a material having an emission and absorption spectrum in the green to orange region that mediates energy transfer. This mediating material is also called an assist dopant, and this method is also called an energy assist method. If this assist dopant is a green light-emitting material, it is possible to give each of red, green and blue (RGB) a function of light emission and energy transfer.
[0029]
Therefore, a blue light-emitting material is used for a sub-pixel constituting a color pixel for blue (hereinafter also referred to as a blue pixel). The green sub-pixel (hereinafter also referred to as a green pixel) contains a blue light emitting material in addition to the green light emitting material. This further improves the energy transfer from blue to green. The red sub-pixel (hereinafter also referred to as a red pixel) contains green and blue light-emitting materials in addition to the red light-emitting material, and the green material also has an assist dopant function. As a result, energy on the short wavelength side efficiently moves to the red material, and the efficiency of the red material is improved.
[0030]
When the red, green, blue (RGB) luminescent dye is a fluorescent luminescent dye, the luminescent peak wavelength of the polymer luminescent material as a base material for diffusing the dye is in a high energy region from ultraviolet to blue, and phenylcarbazole It is desirable that the low molecular material having a group is dispersed. A blue fluorescent pixel may be dispersed in the blue sub-pixel, and a blue light-emitting material may be dispersed in the green sub-pixel, or may be diffused later. The green (G) and red (R) luminescent dyes are diffused. The diffusion order is preferably blue (B), green (G), and red (R). This is for efficiently transferring energy from the short-wavelength light-emitting material to a predetermined light-emitting dye.
[0031]
The diffusion of the blue light-emitting dye into the base material is performed for improving efficiency and color purity. The green light-emitting portion is a green light-emitting portion that diffuses at least a green light-emitting dye into a base material containing a blue (B) dye, facilitates energy transfer to the green light-emitting dye, and obtains green light with high luminous efficiency. The red light-emitting portion also contains a green (G) dye in a base material containing a blue (B) dye and facilitates energy transfer from the blue (B) base material to the red (R) dye. Here, if the green (G) dye is not present, the blue (B) energy does not completely transfer to the red (R) dye, leaving blue () B emission, and in extreme cases, the blue (B) Emission of red (R) light becomes white. In addition, the concentration management of the red (R) dye is more important than other dyes, and it is necessary to set the concentration so as to obtain the optimum luminous efficiency. Therefore, it is desirable to diffuse the red (R) pigment after the diffusion of the blue (B) pigment and the green (G) pigment is completed.
[0032]
On the other hand, in order for the luminescent dye to be composed entirely of a phosphorescent material, the phosphorescent material generally does not have a large absorption in the visible region and has a large absorption in the ultraviolet to blue region. Energy transfer from a high molecular material and a low molecular material having a phenylcarbazole group is used. Therefore, if a fluorescent material that emits light in the visible region is present in the same sub-pixel, energy from the ultraviolet region to the blue region flows into the fluorescent material and emits light at the same time, causing a decrease in chromaticity. is necessary.
[0033]
In summary, as a combination of the luminescent dyes contained in the sub-pixel, a combination as shown in FIG. 5 below can be considered.
FIG. 5 is a diagram showing an example of a combination of luminescent dyes diffused in the pixel.
In the figure, the left column shows the number of the combination, and each symbol is as follows. B indicates blue, G indicates green, R indicates red, p indicates a phosphorescent dye, and f indicates a fluorescent dye. That is, for example, Bp indicates a phosphorescent dye that emits blue light (blue phosphorescent dye).
Here, it is conceivable that the luminous efficiency of No. 2, No. 4, No. 8, and No. 11 is reduced due to the presence of the red fluorescent dye alone. Number 1, number 3, number 5, number 6, number 7, number 9, number 10, or number 12 are preferred.
[0034]
Hereinafter, Examples and Comparative Examples will be described.
<First embodiment>
As the substrate 1, a non-alkali glass substrate having a thickness of 0.7 mm and a square of 50 mm was used. On this substrate 1, the sheet resistance is 20Ω / cm ² The indium tin oxide (ITO) film (which is the anode 2) was formed. Next, after forming the ITO film, ultrasonic cleaning was sequentially performed for 10 minutes each in a neutral detergent, pure water, acetone, and IPA, and then surface treatment was performed in oxygen plasma for 2 minutes.
[0035]
Thereafter, a polyethylene dioxythiophene / polystyrene sulfonate (PEDT / PSS) (trade name: Baytron 4083, manufactured by Bayer) having a thickness of 60 nm was formed as a hole injection layer 3A on the ITO film.
Next, a 70 nm-thick light emitting layer 4A was formed on the hole injection layer 3A by spin coating. The light emitting layer 4A is composed of a polymer light emitting material, polyvinyl carbazole (PVK), as a low molecular light emitting material, 4,4'-bis (carbazol-9-yl) biphenyl (CBP) and fac-tris (2-phenyl). (Pyridinate) iridium (III) is dispersed in PVK at 30 wt% and 7 wt%, respectively.
[0036]
After the light emitting layer 4A was dried, the substrate 1 was set in a vacuum vapor deposition apparatus, and a Ca layer having a thickness of 30 nm and an Ag layer having a thickness of 300 nm were formed as the cathode 5 by vapor deposition.
Thereafter, in a nitrogen gas atmosphere having a dew point of -70 ° C., the adhesive is cured by irradiating ultraviolet rays for 1 minute using a glass cap and an ultraviolet curable resin, followed by sealing to complete the organic EL device of the first embodiment. Formed.
When the light emission characteristics of the obtained organic EL device were measured, the maximum luminance current efficiency was 19 cd / A.
[0037]
<First Comparative Example>
In the organic EL device of the first embodiment, 2- (4-biphenylyl) -5- (4-tert-butylphenyl) -1,3,3 is used instead of the low-molecular-weight light emitting material CBP dispersed in the light emitting layer 4A. An organic EL device of a first comparative example was obtained in the same manner as in the first example, except that 30 wt% of 4-oxadiazole (PBD) was used. When the light emission characteristics of the obtained organic EL device were measured, the maximum luminance current efficiency was 19 cd / A.
[0038]
<Second embodiment>
As the substrate 1, a non-alkali glass substrate having a thickness of 0.7 mm and a square of 50 mm was used. On this substrate 1, the sheet resistance is 20Ω / cm ² The indium tin oxide (ITO) film (which is the anode 2) was formed. Next, after forming the ITO film, ultrasonic cleaning was sequentially performed for 10 minutes each in a neutral detergent, pure water, acetone, and IPA, and then surface treatment was performed in oxygen plasma for 2 minutes.
Thereafter, a polyethylene dioxythiophene / polystyrene sulfonate (PEDT / PSS) (trade name: Baytron 4083, manufactured by Bayer) having a thickness of 60 nm was formed as a hole injection layer 3A on the ITO film.
[0039]
Next, a 70 nm-thick light emitting layer 4A was formed on the hole injection layer 3A by spin coating. The light emitting layer 4A is obtained by dispersing 4,4′-bis (carbazol-9-yl) biphenyl (CBP) as a low molecular light emitting material in polyvinyl carbazole (PVK) which is a polymer light emitting material. The composition ratio was PVK: CBP = 77 wt%: 23 wt%.
On the other hand, a 40 nm-thick green light-emitting dye fac-tris (2-phenylpyridinato) iridium (III) film (which is a green dye film) is coated with a 100 nm-thick Au layer for peeling.
And formed on a surface-processed silicon substrate.
[0040]
The substrate 1 and the silicon substrate were arranged so that the light emitting layer 4A and the green dye film faced each other, and were heated in a heating furnace at 195 ° C. for 10 minutes in a nitrogen gas atmosphere to diffuse the green dye into the light emitting layer 4A. After taking out from the heating furnace and separating the silicon substrate from the substrate 1, the substrate 1 was set in a vacuum deposition apparatus, and a Ca layer having a thickness of 30 nm and an Ag layer having a thickness of 300 nm were formed as the cathode 5 by vapor deposition.
Thereafter, sealing was performed using a glass cap and an ultraviolet curable resin in a nitrogen gas atmosphere at a dew point of -70 ° C., thereby forming an organic EL device of the second embodiment.
When current is passed between the anode 2 and the cathode 5 of the obtained organic EL device, green light emission is obtained and 100 cd / m ² The peak wavelength during light emission was 520 nm, the current efficiency was 16 cd / A, and the CIE chromaticity was (0.28, 0.58).
[0041]
<Second comparative example>
An organic EL device of a second comparative example was formed in the same manner as in the second example except that the composition of the light emitting layer 4A was changed to PVK: PBD = 77 wt%: 23 wt%.
When electricity was supplied between the anode 2 and the cathode 5, green light was emitted. 100 cd / m ² The peak wavelength at the time of light emission was 520 nm, the current efficiency was 10 cd / A, the CIE chromaticity was (0.26, 0.52), and the wavelengths were almost equal.
[0042]
Thus, in the first and second embodiments, highly efficient light emission was obtained.
In comparison with the first comparative example, it can be seen that as the carrier transporting material to be added to the polymer light emitting material of the base material constituting the light emitting layer 4A, both a diazole-based material having a high electron mobility and a phenylcarbazole-based material are similarly favorable. .
However, when compared with the second comparative example in which fine patterning is performed, there is a difference between the two characteristics when a heating step is performed when the green dye is diffused into the polymer base material (light emitting layer). . Looking at the melting points of the respective electron transporting materials, it is presumed that the CBP of the second embodiment is significantly different from 281 ° C. and the PBD of the second comparative example is significantly different from 136 ° C., thus causing a difference in device characteristics. That is, it is considered that the PBD melts in the base material and becomes a liquid state when the melting point is higher than the melting point, easily bleeds to the surface, and the charge transport balance in the light emitting layer is lost.
[0043]
Next, a method for manufacturing an organic EL element for forming sub-pixels corresponding to each color composed of the light emitting layer described above at high density will be described.
<Third embodiment>
FIG. 6 is a manufacturing process diagram of a first dye stamp according to the organic EL device of the present invention.
FIG. 9 is a manufacturing process diagram for manufacturing an organic EL element using the first dye stamp according to the present invention.
The dye stamp is formed by forming a dye layer pattern having a shape corresponding to the sub-pixel in order to diffuse a predetermined luminescent dye into the sub-pixel of the light-emitting layer.
[0044]
First, a method for manufacturing the first dye stamp shown in FIG. 6 will be described.
As shown in FIG. 6A, a novolak-based positive photoresist having a viscosity of 420 mPa · s is applied on a substrate 11 made of, for example, a 3-inch silicon wafer by a spin coating method to form a photoresist having a thickness of 20 μm. The layer 12 is formed. The photoresist layer 12 is pre-baked at 100 ° C. for 120 seconds.
Next, as shown in FIG. 6B, using a photomask 13A processed so as to have an opening 13C from which an exposed portion of a predetermined shape is removed, a light amount of 1000 mj / cm. ² Exposure. Here, one pattern size of the opening 13C of the photomask 13A is 10 μm × 20 μm (substantially the size of a subpixel).
[0045]
Next, as shown in FIG. 6C, the photomask 13A is removed and washed with an alkali developing solution 2.3% TMAH (tetramethylammonium hydroxide) in which the exposed portion of the exposed photoresist layer 12 is dissolved. Then, an opening 14 pattern is formed. The size of the bottom of the opening 14 (substrate 11 side) is 10 μm × 20 μm, the size of the entrance 14A is 6 μm × 16 μm, and the side surface of the opening 14 has an inverted tapered shape. This can be made into an inverse tapered shape by selecting exposure and development conditions.
[0046]
The photoresist (photosensitive resin material) that can obtain an inverted tapered shape after development may be either a negative type or a positive type. If the negative type is used, a difference in light absorption amount at the time of exposure must be provided. If so, it is necessary to produce a reverse tapered shape by further dissolving the vicinity of the substrate surface by utilizing the difference in solubility between the vicinity of the resin surface of the resin layer and the vicinity of the substrate surface during development. Since a relatively thick film can be formed and the edge of the pattern shape is sharp, it is preferable to use a novolak-based positive photosensitive resin.
[0047]
Next, as shown in FIG. 6D, a release layer (not shown) made of Au having a thickness of 100 nm and a dye layer 15 made of, for example, coumarin 6 having a thickness of 40 nm are sequentially formed by an evaporation method. .
Next, as shown in FIG. 6E, the dye layer 15 on the photoresist layer 12 is removed using, for example, an adhesive tape, and the dye layer 15 is formed on the substrate 11 in the opening 14 having a predetermined shape. The formed first dye stamp 20A is obtained.
[0048]
Next, a method of manufacturing the organic EL device according to the third embodiment will be described.
First, as shown in FIG. 9A, a pixel electrode 22 having a predetermined shape, a hole injection layer 23, and a light emitting layer 24 are sequentially formed on a transparent substrate 21. The hole injection layer 23 is made of PEDT / PSS having a thickness of 60 nm. The light emitting layer 24 is made of polyvinyl carbazole in which an electron transporting material PBD having a thickness of 80 nm is dispersed at 30 wt%.
[0049]
Next, as shown in FIG. 9B, in the first dye stamp described above with reference to FIGS. 6A to 6E, a green dye layer 15G is placed on the substrate 11 of the opening 14G. The formed first dye stamp for green 20AG is accurately aligned with the light emitting layer 24 and the dye layer 15G so as to correspond to the RGB sub-pixel pattern to be formed. Thereafter, the light emitting layer 24 and the photoresist layer 12 are brought into close contact with each other by uniformly pressing the substrate 11 against the substrate 21.
Next, as shown in FIG. 9C, heating is performed at 120 ° C. for 10 minutes in a nitrogen-purging oven to transfer and diffuse the dye layer 15G to the light emitting layer 24 side. Thereby, a green light emitting subpixel (light emitting layer) 24G is formed.
[0050]
Next, as shown in FIG. 9D, the first dye stamp 20AG for green is removed, and the first dye stamp for red in which the red dye layer 15R is formed on the substrate 11 in the opening 14R. The 20AR is accurately opposed to the RGB pattern to be formed. The light emitting layer 24 and the photoresist layer 12 are brought into close contact with each other by uniformly pressing the substrate 11 against the substrate 21.
Next, as shown in FIG. 9E, heating is performed at 120 ° C. for 10 minutes in a nitrogen substitution oven to transfer the dye layer 15R to the light emitting layer 24 side and diffuse it. As a result, a red light emitting subpixel (light emitting layer) 24R is formed.
Next, as shown in FIG. 9 (f), the first dye stamp 20AR for red is removed, and the electron injection / transport / hole element layer 25, the metal of an ultrathin film of a predetermined shape are formed on the light emitting layer 24. The organic EL element 30 is obtained by forming the electrode 26 and the transparent electrode 27.
[0051]
Here, the case where green and red are diffused as the dye layer has been described. This is because the light emission of the light emitting material forming the light emitting layer 24 for diffusing the dye is B, and the light emission peak wavelength is 400 nm or more and 500 nm or less. Applied in some cases. In this case, two types of R and G dyes may be diffused. When light is emitted at a shorter wavelength than this, it is necessary to diffuse the B light-emitting dye.
[0052]
In the above-described diffusion of the dye, the side walls of the openings 14G and 14R are inversely tapered with respect to the substrate 11, and when the dye stamps 20AG and 20AR are arranged on the light emitting layer 24, It has a forward taper. Therefore, the detachment of the dye attached to the side wall during diffusion can be suppressed, and the concentration of the dye can be easily controlled. In addition, since the edge of the photoresist 12 that comes into contact with the light emitting layer 24 is sharp and the adhesion is good, the bleeding of the dye in this portion can be suppressed. In other words, it becomes possible to diffuse extremely sharply at the boundary end. Therefore, a fine sub-pixel pattern of the light emitting layer 24 can be easily formed.
[0053]
<Fourth embodiment>
FIG. 7 is a manufacturing process diagram of a second dye stamp according to the organic EL device of the present invention.
FIG. 10 is a manufacturing process diagram for manufacturing an organic EL element using the second dye stamp according to the present invention.
First, a method for manufacturing the second dye stamp shown in FIG. 7 will be described.
As shown in FIG. 7A, a novolak-based positive photoresist having a viscosity of 420 mPa · s is applied on a substrate 11 made of, for example, a 3-inch silicon wafer by a spin coating method to form a photoresist having a thickness of 20 μm. The layer 12 is formed. The photoresist layer 12 is pre-baked at 100 ° C. for 120 seconds.
[0054]
Next, as shown in FIG. 7B, using a photomask 13B processed to have an opening 13D such that an exposed portion of a predetermined shape is removed, a light amount of 1000 mj / cm. ² Exposure. Here, one pattern size of the photomask 13B was 10 μm × 20 μm (substantially the size of a subpixel).
Next, as shown in FIG. 7C, the photomask 13B is removed, and the exposed portion of the exposed photoresist layer 12 is washed with an alkali developing solution 2.3% TMAH in which the exposed portion of the photoresist layer 12 is dissolved. Form. The size of the bottom surface (substrate 11 side) of the inverse tapered pattern 16 is 6 μm × 16 μm, and the size of the upper surface is 10 μm × 20 μm. The side surface of the reverse taper pattern 16 has a reverse taper shape.
[0055]
Next, as shown in FIG. 7D, a release layer (not shown) made of Au having a thickness of 100 nm and a dye layer 15 made of, for example, coumarin 6 having a thickness of 40 nm are sequentially formed by an evaporation method. Thus, a second dye stamp 20B is obtained.
Next, a method for manufacturing the organic EL device of the fourth embodiment will be described.
First, as shown in FIG. 10A, a pixel electrode 22 having a predetermined shape, a hole injection layer 23, and a light emitting layer 24 are sequentially formed on a transparent substrate 21.
Next, as shown in FIG. 10B, in the second dye stamp 20B described above with reference to FIGS. 7A to 7D, the green dye layer 15G is formed on the substrate 11 in reverse. The second dye stamp 20BG for green color formed on the taper pattern is precisely aligned with the dye layer 15G and the light emitting layer 24 so as to correspond to the RGB sub-pixel pattern to be formed. do. After that, the substrate 11 is uniformly pressed against the substrate 21 to bring the dye layer 15G into close contact with the light emitting layer 24.
[0056]
Next, as shown in FIG. 10C, heating is performed in a nitrogen replacement oven for a predetermined temperature time to diffuse the dye layer 15G into the light emitting layer 24. At this time, conditions are set so that the dye layer 14G on the substrate 11 does not evaporate. Thereby, a green light emitting subpixel (light emitting layer) 24G is formed.
Next, as shown in FIG. 10D, the green second dye stamp 20BG is removed, and the red dye layer 15R is formed on the reverse tapered pattern formed on the substrate 11 for the second red dye layer 15R. Of the dye stamps 20BR are accurately opposed to each other so as to correspond to the RGB pattern to be formed. The light emitting layer 24 and the dye layer 15R are brought into close contact with each other by uniformly pressing the substrate 11 against the substrate 21.
[0057]
Next, as shown in FIG. 10E, the dye layer 15R is diffused toward the light emitting layer 24 by heating at a predetermined temperature in a nitrogen substitution oven for a predetermined time. At this time, conditions are set so that the dye layer 15R on the substrate 11 does not evaporate. As a result, a red light emitting subpixel (light emitting layer) 24R is formed.
Next, as shown in FIG. 10F, after removing the second dye stamp 20BR for red, the electron injection / transport / hole element layer 25, the ultrathin film of a predetermined shape is formed on the light emitting layer 24. The organic EL element 30 is obtained by forming the metal electrode 26 and the transparent electrode 27 described above.
Here, since the dye layer is formed on the reverse tapered pattern, the sag at the boundary is small, and therefore, when the dye is diffused into the light emitting layer using this, the bleeding at the boundary is reduced. A fine sub-pixel pattern of the light emitting layer can be easily formed.
[0058]
<Fifth embodiment>
FIG. 8 is a manufacturing process diagram of a third dye stamp according to the organic EL device of the present invention.
FIG. 11 is a manufacturing process diagram for manufacturing an organic EL element using the third dye stamp according to the present invention.
First, a method for manufacturing the third dye stamp shown in FIG. 8 will be described.
First, as shown in FIG. 8A, a photoresist in which a coumarin 6 dye is dissolved in about 1 to 5 wt% in advance is applied on a silicon substrate 11 by a spin coating method, and a 20 μm-thick dye containing A photoresist layer 17 is formed. The photoresist layer 17 is pre-baked for a predetermined temperature and time.
[0059]
Next, as shown in FIG. 8B, using a photomask 13B processed so as to have an opening 13D such that an exposed portion of a predetermined shape is removed, a photoresist layer 17 is formed for a predetermined time. Is exposed. Here, one pattern size of the photomask 13B was 10 μm × 20 μm (substantially the size of a subpixel).
Next, as shown in FIG. 8C, the photomask 13B is removed, and the exposed portion of the exposed photoresist layer 17 is washed with a predetermined alkali developing solution 2.3% TMAH in which the exposed portion is dissolved. A taper pattern 18 is formed. The size of the bottom surface (the substrate 11 side) of the dye-containing reverse taper pattern 18 is 6 μm × 16 μm, and the size of the top surface is 10 μm × 20 μm. The side surface of the dye-containing reverse taper pattern 18 has a reverse taper shape. Thus, a third dye stamp 20C is obtained.
[0060]
This is the same as the second dye stamp described above, except that the dye layer 15 is replaced by the dye-containing reverse taper pattern 18, and the function of dye diffusion to the light emitting layer 24 is the same.
The manufacturing process of the organic EL device using the third dye pattern 20C is shown in FIG. 11, but the operation of the third dye stamp is the same as that of the second dye stamp, and therefore the description thereof is omitted.
In the obtained organic EL device 30, since the dye is formed on the dye-containing reverse taper pattern, the sag at the boundary is small. Therefore, when the dye is diffused into the light emitting layer by using this, the dye at the boundary is Less bleeding. A fine sub-pixel pattern of the light emitting layer can be easily formed.
FIG. 12 shows a cross-sectional configuration of the organic EL element 30 formed as described above.
[0061]
As described above, the shapes of the opening 14, the reverse taper pattern 16, and the dye-containing reverse taper pattern 18 formed in the photoresist layer 12 have been described as rectangular shapes of 10 μm × 20 μm, but these shapes are stripes or strips. In the case of a strip shape, the area is set to be a straight line or a step shape, and then the area is set to be substantially equal to the area of the sub-pixel in order to transfer and diffuse the dye on the pixel electrode. It is sufficient to prepare a photomask in which the positions of the openings and the like are different by one sub-pixel pitch for each color.
As the dye to be used, any dye can be used as long as it is stable to heating, can form a thin film by vapor deposition, and emits red or green blue (RGB) having fluorescence or phosphorescence.
[0062]
As the red (R) dye, a porphyrin compound, a chlorin compound, a perylene compound, a dicyanopyran compound, a squarylium compound, a distyryl compound, an eurolysine compound, a coumarin compound, or the like can be used.
As the green (G) dye, a coumarin compound, a quinacridone compound, a quinolinol metal complex compound, or the like can be used.
As the blue (B) dye, existing fluorescent dyes such as distyrylaryl compounds, diarylamine compounds, triarylamine compounds, tetraphenylbutadiene, and perylene can be used.
In addition, phosphorescent dyes of each RGB emission color, such as a metal complex in which Ir or Pt is used as a central metal and a ligand is arranged, can also be used.
[0063]
【The invention's effect】
As described above, according to the organic electroluminescence device of the present invention, according to the first aspect, the light emitting layer includes a polymer light emitting material and a second light emission wavelength different from the first light emission wavelength of the polymer light emitting material. Consisting of a first low molecular light emitting material containing a phenylcarbazole group having an emission wavelength, and a second low molecular light emitting material having a third emission wavelength longer than the first and second emission wavelengths. By doing so, there is an effect that an organic electroluminescent element having a light emitting layer which has good luminous efficiency and excellent durability and which is easily manufactured can be provided.
According to a second aspect of the present invention, there is provided a method for manufacturing an organic electroluminescent device, comprising: forming a photoresist layer having a reverse tapered pattern on a first substrate; Forming a dye portion on the first substrate, forming a pixel electrode and a light emitting layer on the second substrate sequentially, and setting the photoresist layer side to face the light emitting layer side; After the first substrate is placed on the second substrate, the step of adhering, and the step of heating the first substrate and the second substrate, which are in close contact with each other, in the light emitting layer corresponding to the pixel electrode A step of forming a dye layer by diffusing the dye portion, and a step of forming a common electrode on the dye layer after separating the first substrate from above the second substrate. By this, the fine pixel pattern of the light emitting layer Method for producing an organic electroluminescent device capable of producing good form there is an effect that it provides.
[Brief description of the drawings]
FIG. 1 is a schematic sectional view showing a basic structure of an embodiment of an organic EL device of the present invention.
FIG. 2 is a schematic sectional view illustrating a basic configuration of an organic EL element.
FIG. 3 is a chemical structural formula of an example of a low molecular weight material containing an N-phenylcarbazole group.
FIG. 4 is a chemical structural formula of a dye composed of a metal organic complex.
FIG. 5 is a diagram showing an example of a combination of luminescent dyes diffused in a pixel.
FIG. 6 is a manufacturing process diagram of a first dye stamp according to the organic EL device of the present invention.
FIG. 7 is a manufacturing process diagram of a second dye stamp according to the organic EL element of the present invention.
FIG. 8 is a manufacturing process diagram of a third dye stamp according to the organic EL device of the present invention.
FIG. 9 is a manufacturing process diagram for manufacturing an organic EL element using the first dye stamp according to the present invention.
FIG. 10 is a manufacturing process diagram for manufacturing an organic EL element using the second dye stamp according to the present invention.
FIG. 11 is a manufacturing process diagram for manufacturing an organic EL element using the third dye stamp according to the present invention.
FIG. 12 is a cross-sectional view illustrating a configuration example of the organic EL element of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Transparent substrate, 2 ... Anode, 3 ... Hole transport layer, 4, 4A ... Light emitting layer, 5 ... Cathode, 6 ... Power supply, 7 ... Light emission, 8, 8A ... Organic EL layer, 10, 10A ... Organic EL Element, 11: Substrate, 12: Photoresist layer, 13A, 13B: Photomask, 13C: Opening, 14, 14G, 14R: Opening, 15, 15G, 15R: Dye layer, 16, 16G, 16R: Reverse taper Pattern, 17: Dye-containing photoresist, 18, 18G, 18R: Dye-containing reverse taper pattern, 20A, 20AG, 20AR, 20B, 20BG, 20BR, 20C, 20CG, 20CR: Dye stamp, 21: Transparent substrate, 22: Pixel Electrodes, 23: hole injection layer, 24, 24G, 24R: light emitting layer, 25: electron injection / electron transport / hole blocking layer, 26: extremely thin metal electrode, 27: transparent electrode, 30: yes EL element.

Claims (2)

An organic electroluminescent element in which a first electrode, an organic electroluminescent layer having at least a light emitting layer, and a second electrode are sequentially stacked on a substrate.
The light emitting layer is a polymer light emitting material, a first low molecular light emitting material containing a phenylcarbazole group having a second emission wavelength different from the first emission wavelength of the polymer light emitting material, An organic electroluminescent device comprising: a second low-molecular light-emitting material having a third emission wavelength longer than the second emission wavelength. Forming a photoresist layer having a reverse taper pattern on the first substrate;
Forming a dye portion on the first substrate exposed from the reverse tapered pattern;
Sequentially forming a pixel electrode and a light emitting layer on the second substrate;
Placing the first substrate on the second substrate with the photoresist layer side facing the light emitting layer side, and then closely contacting the first substrate;
Heating the adhered first substrate and the second substrate to diffuse the dye portion into the light emitting layer corresponding to the pixel electrode, thereby forming a dye layer;
Forming a common electrode on the dye layer after separating the first substrate from the second substrate;
A method for manufacturing an organic electroluminescent device, comprising:

Images