JP2010129381A - Method for manufacturing organic el element - Google Patents

Abstract

An organic EL device manufacturing method capable of reducing variation in chromaticity is provided.
A method of manufacturing an organic EL device 100 that emits white light, in which an anode 10 is formed on a substrate, and an anode 10 is formed before a hole transport layer 20 is formed on the anode 10. Based on the film thickness measurement step for measuring the thickness of the film, the total thickness of the design values of the film thickness of the anode 10 and the film thickness of the hole transport layer 20, and the film thickness of the anode 10 measured in the film thickness measurement process. A film thickness setting process for setting the film thickness of the hole transport layer 20 to be formed, and a transport layer film forming process for forming the hole transport layer 20 on the anode 10 with the film thickness set in the film thickness setting process. .
[Selection] Figure 1

Description

  The present invention relates to a method for producing an organic EL element. In particular, the present invention relates to a production method suitable for application to a white light emitting organic EL element.

  Conventionally, there has been an organic EL element that emits white light. This white light-emitting organic EL device reproduces white color by, for example, stacking a light-emitting layer (peak wavelength: 460 to 480 nm) and an orange light-emitting layer or a blue light-emitting layer (peak wavelength: 460 nm or less) and an orange light-emitting layer. .

As a design method of such a white light emitting organic EL element, there is one disclosed in Patent Document 1. In the design method shown in Patent Document 1, a hole transport layer and an organic host material capable of sustaining hole and electron injection each include a plurality of types of fluorescent materials that emit fluorescence having different emission color systems. A white organic electroluminescent element formed by providing a plurality of organic light emitting layers and an electron transport layer between an anode and a cathode is designed. A step of setting the film thickness of each organic light emitting layer and the ratio of the organic host material to the fluorescent material using the light emission efficiency and the chromaticity coordinate value of the light emission color as parameters, and the set film of each organic light emitting layer In accordance with the thickness, the above design is performed from the step of setting the film thickness of at least one of the hole transport layer and the electron transport layer using the chromaticity coordinate value of the emission extraction color as a parameter. In this way, by setting the thickness and material ratio of the plurality of organic light emitting layers and the film thickness of the hole transport layer and electron transport layer through each step, the light emission color becomes closest to the white color purity. Can be designed efficiently.
JP 2004-63349 A

  However, when an organic EL element is manufactured by laminating an anode, a hole transport layer, and the like, the film thickness of each layer may deviate from the set film thickness. Thus, when the film thickness of the layers constituting the organic EL element such as the anode and the hole transport layer deviates from the set film thickness, the light emission position within the light emitting layer changes, so that the emission spectrum peak caused by optical interference occurs. The position changes, and the chromaticity of white, which is the emission color of the organic EL element, changes.

  In particular, the anode may be formed to be the thickest among the layers constituting the organic EL element. For example, the total thickness of all layers (for example, 6 layers) is 100 nm to 200 nm, whereas the transparent electrode has a thickness of 100 nm to 200 nm alone. Therefore, the amount of deviation of the anode increases with respect to the set film thickness. In other words, the film thickness difference between the set film thickness at the anode and the actual film thickness where the deviation has occurred is compared with the film thickness difference between the set film thickness at each layer of the organic film and the actual film thickness at which the deviation has occurred. large. Therefore, there is a problem that the influence of the optical interference given by the deviation of the film thickness of the anode is large and the chromaticity variation is large.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a method for manufacturing an organic EL element that can reduce variations in chromaticity.

In order to achieve the above object, the method for producing an organic EL device according to claim 1 is a white layer comprising a transparent electrode, a hole transport layer, a plurality of light emitting layers emitting different colors, an electron transport layer, and a cathode. A method for producing an organic EL element that emits light,
An anode film forming step of forming a transparent electrode on the substrate;
Before forming the hole transport layer on the transparent electrode, a film thickness measuring step for measuring the film thickness of the transparent electrode,
The film thickness of the hole transport layer to be formed is set based on the total film thickness of the transparent electrode film thickness and the designed value of the hole transport layer film thickness and the film thickness of the transparent electrode measured in the film thickness measurement process. A film thickness setting process to be performed;
A transport layer film forming step of forming a hole transport layer on the transparent electrode at a film thickness set in the film thickness setting step;
It is characterized by providing.

  By doing this, the deviation of the film thickness of the transparent electrode from the design value can be corrected by the hole transport layer, so the total film thickness of the formed transparent electrode and hole transport layer is the sum of the design values. The film thickness can be approached. Therefore, an organic EL element that can reduce chromaticity variation can be manufactured.

  As the plurality of light emitting layers, as shown in claim 2, an orange light emitting layer and a light blue light emitting layer can be adopted.

  According to a third aspect of the present invention, the maximum peak wavelength of the light blue light emitting layer is 460 nm to 480 nm, and the optical distance from the interface between the substrate and the transparent electrode to the interface between the orange light emitting layer and the light blue light emitting layer is L1, orange When the optical distance from the interface between the light emitting layer and the light emitting layer to the cathode interface is L2, the design values of the film thickness of the organic EL element are L1 + L2 = (2m + 1) λ / 4, L2 = (2n−1) λ / 4, (m and n are natural numbers satisfying m ≧ n and λ is the light blue maximum peak wavelength) may be designed.

  Further, as shown in claim 4, in the film thickness setting step, the transparent electrode with respect to the film thickness of the design value is used so that the color difference is 5 or less with respect to the chromaticity of the organic EL element satisfying the film thickness of the design value. The film thickness of the hole transport layer may be set so that the deviation of the optical distance L1 is corrected by the film thickness of the hole transport layer.

  By doing in this way, it can be made almost the same as the chromaticity of the organic EL element satisfying the designed film thickness.

  Further, as shown in claim 5, in the film thickness setting step, the film thickness of the hole transport layer is set so that the deviation of the optical distance L1 by the transparent electrode with respect to the designed film thickness is ± 10 nm or less. May be.

  By doing in this way, it can be set as 5 or less color differences with respect to the organic EL element which satisfy | fills the film thickness of a design value.

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

  FIG. 1 is a front view showing a schematic configuration of an organic EL element in an embodiment of the present invention. FIG. 2 is a graph showing the relationship between the film thickness and chromaticity of the transparent electrode. FIG. 3 is a graph showing a range of a color difference within 5 from the chromaticity at the designed film thickness (in the case of 145 nm) of the transparent electrode.

  The organic EL element 100 according to the embodiment of the present invention emits white light. As shown in FIG. 1, the organic EL element 100 includes an anode 10 corresponding to a transparent electrode of the present invention, a hole transport layer 20, an orange light emitting layer 30, on a substrate transparent to visible light (not shown). The light emitting layer 40, the electron transport layer 50, and the cathode 60 are sequentially laminated. Further, if necessary, a hole injection layer may be provided between the anode 10 and the hole transport layer 20, or an electron injection layer may be provided between the electron transport layer 50 and the cathode 60.

  The substrate is a transparent electrically insulating substrate made of glass or resin. The anode 10 formed on the substrate has, for example, a film thickness of about 100 to 200 nm (145 nm in this embodiment), and the constituent materials include an indium-tin oxide (ITO) film and indium-zinc A transparent conductive film such as an oxide film can be used. The hole transport layer 20 has, for example, a film thickness of about 65 nm, and a constituent material such as triphenylamine tetramer can be used.

  The orange light emitting layer 30 has, for example, a film thickness of about 20 nm, and as a constituent material, triphenylamine tetramer + rubrene can be used. For example, the light emitting layer 40 has a film thickness of about 35 nm, and as a constituent material, triphenylamine tetramer + perylene 5% or the like can be used. The electron transport layer 50 has, for example, a film thickness of about 30 nm, and as a constituent material, tris (8-quinolinolato) aluminum (Alq3) or the like can be used. The cathode 60 has a film thickness of, for example, about 100 nm to 1 μm, and as a constituent material, a two-layer structure such as LiF / Al or LiO / Al, or a mixed layer of metal atoms such as Mg and Ag, Al and Li, or the like Can be used.

  In the present embodiment, an example in which two layers of the orange light emitting layer 30 and the light blue light emitting layer 40 are used as the light emitting layer is adopted, but the present invention is not limited to this. As long as the organic EL element 100 can emit white light, for example, two layers of an orange light emitting layer and a blue light emitting layer (peak wavelength of 460 nm or less) may be used, or three or more light emitting layers may be stacked.

  The film thickness of the organic EL element having the above-described configuration is set as follows. The light emission peak of the orange light emitting layer 30 and the light blue light emitting layer 40 is an interface between the orange light emitting layer 30 and the light blue light emitting layer 40, and the maximum peak wavelength of the light blue light emitting layer 40 is 460 nm to 480 nm. When the optical distance from the interface between the orange light emitting layer 30 and the light emitting layer 40 to L1 is L1, and the optical distance from the interface between the orange light emitting layer 30 and the light emitting layer 40 to the cathode 60 interface is L2, the organic EL element 100 The design values of the film thicknesses of L1 + L2 = (2m + 1) λ / 4, L2 = (2n−1) λ / 4, (m and n are natural numbers satisfying m ≧ n, and λ is the light blue maximum peak wavelength) are satisfied. Designed to.

  However, in the organic EL element 100, even if the film thickness is set in this way, the film thickness of the layers constituting the organic EL element 100 such as the anode 10 and the hole transport layer 20 may deviate from the set film thickness. . When the film thickness deviates from the set value, the light emission position inside the light emitting layer changes, so that the peak position of the emission spectrum caused by optical interference changes and the chromaticity changes. In particular, the total thickness of all layers (for example, six layers) is 100 nm to 200 nm, whereas the thickness of the anode 10 is often as thick as about 100 nm to 200 nm alone. . Accordingly, the anode 10 has a large amount of deviation with respect to the set film thickness, and has a great influence on chromaticity.

  FIG. 2 shows the change in chromaticity when the design value of the thickness of the anode 10 is 145 nm and the thickness of the anode 10 is 145 nm, 145 nm ± 1 to 5 nm, and 145 nm ± 5 to 10 nm. It is a figure which shows the result investigated as a change of chromaticity coordinate. As shown in FIG. 2, it can be seen that as the film thickness of the anode 10 deviates from the set value, the chromaticity also deviates. In other words, the film thickness of the anode 10 varies with respect to the set value, and the chromaticity also varies. The film thickness of the layers other than the anode is fixed.

The thick circle in FIG. 2 indicates the range where the color difference ΔEab with respect to the chromaticity at the designed film thickness is 5 or less. This color difference ΔEab can be obtained by the following equation.
ΔEab = [(ΔL) ² + (Δa) ² + (Δb) ² ] ^1/2
ΔL = L2-L1
Δa = a1-a2
Δb = b1−b2
L = 116 (Y / Yn) ^1/3 -16
a = 500 [(X / Xn) ¹ /3-(Y / Yn) ^1/3 ]
b = 200 [(Y / Yn) ¹ /3-(Z / Zn) ^1/3 ]
Chromaticity x = X / (X + Y + Z), y = Y / (X + Y + Z)
Y = Yn = 100
n: Standard light C
According to the classification of allowable color differences according to ASTM (American Society for Testing and Materials), when the color difference ΔEab is 5 or less, it can be recognized that they are substantially the same. Therefore, by setting the color difference ΔEab to 5 or less, the chromaticity of the organic EL element satisfying the designed film thickness can be made almost the same. On the contrary, when the film thickness of the anode 10 is shifted from the set value by 5 nm or more, the color difference ΔEab becomes 5 or more. In other words, the change is such that it can be visually recognized.

  Therefore, the film thickness of the anode 10 was evaluated before forming the hole transport layer 20, and the film thickness deviation was classified into 5 nm or less and 5 nm or more (optical distance 10 nm or more). The thickness of the anode 10 is 1.135 to 140 nm, 2.140 to 150 nm (within ± 5 nm), and 3.150 to 155 nm. And with respect to this classified anode 10, the film thickness of the hole transport layer 20 is 1. +5 nm, 2. ± 0 nm, 3. It was corrected to −5 nm (the refractive index of the hole transport layer 20 and that of the anode 10 at 470 nm are almost the same, so that the anode 10 + the hole transport layer 20 is fixed). As a result, the color difference ΔEab was 15 at maximum in the state without correction of the hole transport layer 20, whereas the color difference ΔEab was 5 or less in the state with correction. The film thickness of the anode 10 is 5 × 1.95 (refractive index @ 470 nm) ≈10 nm in terms of optical distance (film thickness × refractive index). Thus, by setting the film thickness of the hole transport layer 20 so that the deviation of the optical distance L1 by the anode 10 from the designed film thickness is ± 10 nm or less, the organic EL element that satisfies the designed film thickness In contrast, the color difference ΔEab can be set to 5 or less.

  As described above, the film thickness of the organic EL element is set by L1 and L2. However, the orange light emitting layer 30 and the like are thin with respect to the anode 10 and have a small deviation from the set value (setting). The film thickness deviated from the value is also thin). Further, it is known that the film thickness of the hole transport layer 20 does not significantly affect the chromaticity of the organic EL element. Therefore, the deviation from the set value of the optical distance L1 based on the deviation of the film thickness of the anode 10 can be corrected by the film thickness of the hole transport layer 20.

  Here, the manufacturing method of the organic EL element 100 in the present embodiment will be described.

  First, the anode 10 is formed on the substrate by a method such as vacuum deposition, sputtering, chemical vapor deposition (CVD), atomic layer epitaxy (ALE), coating, or dipping (anode film forming step). Next, the film thickness of the anode 10 is measured before the hole transport layer 20 is formed on the anode 10 by, for example, an ellipsometer (film thickness measurement step).

  Next, based on the total thickness of the design values of the thickness of the anode 10 and the thickness of the hole transport layer 20 and the thickness of the anode 10 measured in the thickness measurement step, the hole transport layer 20 to be deposited is formed. The film thickness is set (film thickness setting step). In other words, based on the total film thickness of the design value and the film thickness of the anode 10 measured in the film thickness measurement step, the total film thickness of the anode 10 and the hole transport layer 20 is the sum of the set values. The film thickness of the hole transport layer 20 to be formed is set so as to approach the film thickness. That is, the value obtained by subtracting the measured thickness of the anode 10 from the total set thickness is set as the thickness of the hole transport layer 20 to be formed. The total thickness of the design values of the thickness of the anode 10 and the hole transport layer 20 is the thickness obtained by subtracting the set thickness of the orange light emitting layer 30 from the set thickness of the optical distance L1. can do.

  Then, the hole transport layer 20 is formed on the anode 10 by a method such as vacuum deposition, sputtering, chemical vapor deposition (CVD), atomic layer epitaxy (ALE), coating, or dipping with the film thickness set in the film thickness setting step. Film (transport layer deposition step).

  After the transport layer forming step, the orange light emitting layer 30, the light blue light emitting layer 40, the electron transport layer 50, and the cathode 60 are sequentially formed.

  By doing so, since the deviation of the film thickness of the anode 10 from the design value can be corrected by the hole transport layer 20, the total film thickness of the film of the anode 10 and the hole transport layer 20 formed is determined as the design value. The total film thickness can be approached. Therefore, an organic EL element that can reduce chromaticity variation can be manufactured.

  In the above-described embodiment, the example in which the film thickness of the anode 10 is 145 nm is described. However, the relationship between the film thickness and chromaticity (x, y) of the transparent electrode in FIG. 4 and FIG. As can be seen from the relationship between the film thickness and chromaticity (y) of the transparent electrode, the present invention is not limited to this. FIG. 6 is a graph showing a range within 5 color differences from the design film thickness (in the case of 35 nm) of the anode 10. Further, as apparent from FIG. 6, even when the film thickness of the anode 10 is 35 nm, the range within the color difference of 5 is substantially the same as that when the film thickness of the anode 10 is 145 nm. If the deviation from the design value is corrected to 10 nm or less, the color difference ΔEab becomes 5 or less. In the relational expression of the optical distances L1 and L2 described above, m = 2 when 145 nm, n = 1, and m = n = 1 when 35 nm.

It is a front view which shows schematic structure of the organic EL element in embodiment of this invention. It is a graph which shows the relationship between the film thickness of a transparent electrode, and chromaticity. It is a graph which shows the range within 5 color differences from chromaticity in the film thickness (in the case of 145 nm) of the design value of a transparent electrode. It is a graph which shows the relationship between the film thickness of a transparent electrode, and chromaticity (x, y). It is a graph which shows the relationship between the film thickness of a transparent electrode, and chromaticity (y). It is a graph which shows the range within 5 color differences from chromaticity in the design film thickness (in the case of 35 nm) of a transparent electrode.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Anode (transparent electrode), 20 Hole transport layer, 30 Orange light emitting layer, 40 Light blue light emitting layer, 50 Electron transport layer, 60 Cathode, 100 Organic EL element

Claims (5)

A method for producing an organic EL device that emits white light by laminating a transparent electrode, a hole transport layer, a plurality of light emitting layers emitting different colors, an electron transport layer, and a cathode,
An anode film forming step of forming the transparent electrode on a substrate;
Before forming the hole transport layer on the transparent electrode, a film thickness measuring step for measuring the film thickness of the transparent electrode;
The hole transport layer to be formed on the basis of the total film thickness of the transparent electrode and the design value of the film thickness of the hole transport layer, and the film thickness of the transparent electrode measured in the film thickness measurement step. A film thickness setting step for setting the film thickness of
A transport layer forming step of forming the hole transport layer on the transparent electrode at a thickness set in the film thickness setting step;
The manufacturing method of the organic EL element characterized by the above-mentioned.   The method for producing an organic EL element according to claim 1, wherein the plurality of light emitting layers include an orange light emitting layer and a light blue light emitting layer.   The light emitting layer has a maximum peak wavelength of 460 nm to 480 nm, an optical distance from the interface between the substrate and the transparent electrode to the interface between the orange light emitting layer and the light emitting light layer is L1, and the orange light emitting layer and the When the optical distance from the interface with the blue light emitting layer to the cathode interface is L2, the design values of the film thickness of the organic EL element are L1 + L2 = (2m + 1) λ / 4, L2 = (2n−1) λ / 4 (M, n is a natural number satisfying m ≧ n, λ is a light blue maximum peak wavelength), and the organic EL device manufacturing method according to claim 2.   In the film thickness setting step, the deviation of the optical distance L1 by the transparent electrode with respect to the film thickness of the design value so that the color difference is 5 or less with respect to the chromaticity of the organic EL element satisfying the film thickness of the design value. The method of manufacturing an organic EL element according to claim 3, wherein the film thickness of the hole transport layer is set so as to be corrected by the film thickness of the hole transport layer. The film thickness setting step sets the film thickness of the hole transport layer so that a deviation of the optical distance L1 by the transparent electrode with respect to the designed film thickness is ± 10 nm or less. 3. A method for producing an organic EL device according to 3.

Images