JP2007273902A - Organic led element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an organic LED element in which a reduction of chromaticity change by an angle of field is achieved by a simple method. <P>SOLUTION: In an inside of one pixel, a first part 2a in which a film thickness of ITO2 is T<SB>1</SB>and a second part 2b in which the film thickness of ITO2 is T<SB>2</SB>are prepared by a predetermined area ratio. The values of the film thickness T<SB>1</SB>and the film thickness T<SB>2</SB>are the value which cancels out the chromaticity change due to the angle of field mutually. The thickness difference of the first part 2a and the second part 2b is 30-70 nm preferably. A level difference of the first part 2a and the second part 2b is preferably to be a gently-sloping shape. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an organic LED (Light-Emitting Diode) element.

  The organic LED element is also referred to as an organic EL (Electro Luminescence) element, and is an element that utilizes a phenomenon in which light is emitted by excitons generated by recombination of electrons and holes injected into an organic substance.

  In recent years, displays using this organic LED element have been actively developed. This is because the organic LED display has a wide viewing angle, a fast response speed, a high contrast, and the like as compared with the liquid crystal display.

  In general, an organic LED element has a structure in which an organic film is sandwiched between a transparent conductive film and a metal electrode, and light emitted inside the element is extracted outside the element through the transparent electrode. Here, the emitted light is emitted with an intensity equal to all directions inside the element. That is, light having the same intensity as the light emitted in front of the element is also emitted in the direction of the back surface of the element. Therefore, in order to increase the amount of light extracted to the outside, it is necessary to reflect the light radiated on the back surface forward and to extract it efficiently.

  However, the light traveling directly in front of the element and the light reflected back to the front interfere with each other. In addition, since there is a difference in refractive index between members constituting each layer, light is reflected also at the interface. This will be described with reference to FIG.

  FIG. 21 is a schematic cross-sectional view of an organic LED display device. As shown in the figure, an organic LED display device 91 is formed by laminating an ITO (Indium Tin Oxide) 93 as an anode, an organic film 94, and an aluminum film 95 as a cathode in this order on a glass substrate 92. The organic LED element 96 is provided. Here, the refractive index of the glass substrate 92 is about 1.55, the refractive index of the organic film 94 is about 1.8, and the refractive index of ITO 93 is about 1.9.

  The organic LED display 91 is provided with a sealing member 97 for sealing the organic LED element 96 on the glass substrate 92. In FIG. 21, reference numeral 98 schematically shows a power source that applies a driving voltage to the organic LED element 96.

  When a voltage is applied to the organic LED element 96, electrons are injected as carriers from the cathode and holes are injected from the anode, respectively. These carriers are recombined inside the organic film 94, and light is emitted by excitons generated thereby.

  The light emitted from the light emitting region is reflected by the aluminum film 95 after going to the back direction (upward in the drawing) in addition to the light 99 going to the front (downward in the drawing) of the organic LED display device 91. There is also light 100 that travels forward after being done.

  In addition, since there is a large refractive index step at the interface between the glass substrate 92 and the ITO 93, the light is reflected forward by the glass substrate 92 after going forward, and further reflected by the aluminum film 95 again. There is also light 101 going forward.

  Similarly, there is also light 102 that is reflected in the order of the aluminum film 95, the glass substrate 92, and the aluminum film 95 after going in the back direction.

  Since these lights (99, 100, 101, 102) interfere with each other, there is a problem that the chromaticity changes depending on the viewing angle.

  Conventionally, for such problems, the phase difference between the reflected light of the front radiated light and the back radiated light satisfies the conditions for strengthening optical interference with respect to the film thickness of each film constituting the organic LED element. Optimization is performed (for example, refer nonpatent literature 1).

For example, when the optical distance from the light emitting region to the cathode reflecting surface is L ₁ and the distance from the anode reflecting surface is L ₂ , the conditions for strengthening interference with light of wavelength λ are as follows:
L ₁ = {(2m + 1) / 4} λ
L ₂ = {(m + 1) / 2} λ
(However, m = 0, 1, ...)
It becomes. Therefore, the emission spectrum affected by the optical interference and L ₂ where the external quantum efficiency is optimal are obtained, and the film thickness balance between the organic film (hole injection layer and hole transport layer) constituting the L ₂ and ITO. By adjusting, the light extracted outside the organic LED element can be increased.

Satoshi Miyaguchi, 6 others, “Development of organic EL full-color display”, Pioneer R & D, Volume 11, No. 1, p. 21-28

  However, in the method of optimizing the film thickness so as to satisfy the conditions for strengthening optical interference, it is necessary to strictly control the film thickness according to the refractive index for each film. On the other hand, the demand for viewing angle dependency of chromaticity tends to increase, and there is a limit to deal with this by only optimizing the film thickness.

  The present invention has been made in view of such problems. That is, an object of the present invention is to provide an organic LED element in which a chromaticity change due to a viewing angle is reduced by a simple method.

  Other objects and advantages of the present invention will become apparent from the following description.

The present invention comprises an anode formed on a substrate;
An organic layer formed on the anode and including at least a light emitting layer;
In an organic LED element comprising a cathode formed on the organic layer,
In one pixel, portions having different distances from the substrate to the cathode are provided at a predetermined area ratio,
The distance is a value that cancels out chromaticity changes due to viewing angles.

In the present invention, the anode is ITO,
In one pixel has a first portion the thickness of the ITO is T _1, the thickness of the ITO is a second section which is T _2,
The first part and the second part are provided in a predetermined area ratio,
The values of T ₁ and T ₂ may be values that cancel out chromaticity changes due to viewing angles.
In this case, the step portion between the first portion and the second portion is preferably a gentle shape.
Alternatively, it is preferable that a forward taper-shaped insulating film is formed at a step portion between the first portion and the second portion.

In the present invention, the anode is made of a material that transmits light from the light emitting layer,
At a predetermined location on the substrate, a transparent film having a refractive index close to that of the anode is provided so as to be covered with the anode,
The transparent film, the laminated portion of the anode and the single layer portion consisting only of the anode are provided in a predetermined area ratio,
The film thickness T _{3 of the} laminated portion and the film thickness T ₄ of the single layer portion may be values that cancel each other out chromaticity changes due to viewing angles.

In the present invention, in one pixel has a first portion the thickness of the organic layer is a T _5, the film thickness of the organic layer and a second portion which is T _6,
The first part and the second part are provided in a predetermined area ratio,
Wherein T ₅ and the value of the T ₆ can be assumed that a value cancel each other chromaticity change due to viewing angle.

  According to the present invention, portions having different distances from the substrate to the cathode are provided in one pixel at a predetermined area ratio, and this distance is a value that cancels out chromaticity changes due to viewing angles. Therefore, an organic LED element having a small change in chromaticity depending on the viewing angle can be obtained.

  In the following description, the case where the light emitted from the organic layer is white light will be described as an example. This is because the chromaticity change in white light is generally recognized most sensitively by the observer.

  1 to 6 show the viewing angle dependence of chromaticity when the ITO film thickness is 130 nm, 140 nm, 150 nm, 160 nm, 170 nm, and 180 nm. The organic layer has a thickness of 142 nm in all cases. The viewing angle is changed to 0 degrees, 30 degrees, 45 degrees, and 60 degrees with respect to the normal direction of the panel.

  The chromaticity change in FIGS. 1 to 6 is obtained by simulation, and is obtained by obtaining an emission spectrum from a modulation spectrum. A specific method of simulation will be described with reference to FIG.

  The modulation spectrum was obtained as follows.

  In FIG. 21, only the interference between the lights 99, 100, 101, and 102 was considered, with the reflection at the aluminum film being limited to 2 times and the reflection of 3 or more times being ignored. Further, reflection on the back surface of the glass substrate 92 is not considered.

When considering the one light of the above four kinds of light (99,100,101,102), the transmitted intensity of the light at the wavelength lambda is, _{I 0} (lambda) of the original spectral intensity, a _{n i} i If the refractive index of the th transmissive layer, n _j is the refractive index of the j th transmissive layer,
I ₀ (λ) Π {1- (n _i −n _j ) ² / (n _i + n _j ) ² } (1)
It is represented by

In addition, the phase of this light is
exp {Σ2π (nd / λ)} (2)
It is represented by Here, n is the refractive index of the transmission layer, and d is the thickness of the transmission layer.

Using equations (1) and (2), the transmission intensity and phase for each wavelength are calculated for each of the four types of light, and the sum of these vectors is I (λ), the modulation spectrum is {I (λ ) / I ₀ (λ)}.

  Next, the emission spectrum is obtained by multiplying the spectrum (original spectrum) when it is assumed that only the light 99 is extracted to the outside in FIG. 21 by the modulation spectrum of the corresponding film thickness. Note that the original spectrum is the emission spectrum of the combined wave obtained by superimposing the four types of light (99, 100, 101, 102) that affect the chromaticity, and the emission spectrum when the observer actually looks at the display. Approximate equal and obtained by dividing by the corresponding modulation spectrum.

With the above calculation method, the emission spectrum observed from the front can be calculated for each film thickness of ITO. When the ITO film thickness is changed, the emission color draws a curve similar to a part of an ellipse on the chromaticity coordinates. When the ITO film thickness is increased, the chromaticity coordinates behave in such a manner as to move clockwise on the ellipse.
On the other hand, when the observation direction is tilted from the front (viewing angle 0 degree), the chromaticity coordinates of the emission color may move counterclockwise on the ellipse as if the film thickness of ITO is thin. It is found from actual measurements.
Therefore, in the simulation of the emission spectrum when the observation angle is changed, the calculation result of the emission spectrum in the front observation when the ITO film thickness is reduced is used according to the observation angle. When the observation angle is θ, the total film thickness of the organic film and the ITO film is reduced by a factor of cos θ, and when the decrease is calculated as a decrease in the ITO film thickness, the obtained value is the result of actual measurement. I found that it fits well. Here, θ is an observation angle when the ITO film is viewed from the glass substrate. Since light refraction occurs at the interface between the glass substrate and air according to Snell's law, θ is smaller than the angle at which the actual display is observed. For example, θ is 19.5 degrees when the viewing angle is 30 degrees, θ is 28.1 degrees when the viewing angle is 45 degrees, and θ is 35.3 degrees when the viewing angle is 60 degrees.
Changes in chromaticity depending on the viewing angle calculated in this way are shown in FIGS.
The case where the film thickness is increased and the viewing angle is increased will be further described with reference to FIGS.
In FIG. 1, the chromaticity coordinates when the viewing angles are 0 degree, 30 degrees, 45 degrees and 60 degrees are (0.301, 0.316), (0.318, 0.326) and (0, respectively). .334, 0.344) and (0.351, 0.370), where the origin is a viewing angle of 0 degrees, the chromaticity coordinates move counterclockwise as the viewing angle increases. This moving direction is the same in the film thickness of each ITO. For example, the chromaticity coordinates at each viewing angle in FIG. 6 are (0.300, 0.367) for 0 degrees and (0.310, 0.320) for 60 degrees.
Further, how the chromaticity coordinates move when each film thickness of ITO changes is indicated by a value of a viewing angle of 0 degrees for each film thickness, the film thicknesses are 130 nm, 140 nm, 150 nm, 160 nm, and 170 nm. And chromaticity coordinates at 180 nm are (0.310, 0.316), (0.294, 0.319), (0.291, 0.328), (0.292, 0.341), respectively. ), (0.296, 0.354), and (0.300, 0.367), and it can be seen that the chromaticity coordinates at a viewing angle of 0 degrees move clockwise as the ITO film thickness increases.

  Comparing FIGS. 1 to 6, when the ITO film thickness is 160 nm, the chromaticity change due to the viewing angle becomes the smallest (FIG. 4). When the thickness of ITO is made thinner than 160 nm, the above curve moves counterclockwise on the ellipse (FIGS. 1 to 3). On the other hand, when the film thickness of ITO is thicker than 160 nm, the above curve moves clockwise on the ellipse (FIGS. 5 to 6). As described above, the direction in which the chromaticity changes is opposite between the case where the film thickness is reduced from the reference value and the case where the film thickness is increased.

  From the above, the present inventor has thought that the change in chromaticity due to the viewing angle can be suppressed by using a combination of ITO having a film thickness that cancels the change in chromaticity.

  FIG. 7 shows the change in chromaticity depending on the viewing angle of the organic LED element in which the ITO film thickness is 130 nm and the ITO film thickness is 180 nm in a ratio of 4: 6. Is shown. The viewing angle dependence of chromaticity was determined by the same simulation as in FIGS. For comparison, a case where only ITO having a film thickness of 130 nm is used and a case where only ITO having a film thickness of 180 nm is used are also shown.

  As shown in FIG. 7, the chromaticity at each viewing angle when using ITO with different film thicknesses is the chromaticity at the corresponding viewing angle when the ITO film thickness is 130 nm and the ITO film thickness is 180 nm. Is the average value with the chromaticity at the corresponding viewing angle. Therefore, it can be seen that by using a combination of ITO having different film thicknesses, the change in chromaticity depending on the viewing angle can be reduced as compared to the case of using only a single film thickness of ITO.

  8 to 12 show changes in chromaticity depending on the viewing angle when the area ratio between the portion where the ITO film thickness is 130 nm and the portion where the ITO film thickness is 180 nm is changed. The viewing angle dependence of chromaticity was determined by the same simulation as in FIGS. The organic layer has a thickness of 142 nm in all cases. The viewing angle is changed to 0 degrees, 30 degrees, 45 degrees, and 60 degrees with respect to the normal direction of the panel.

  8 to 12, it can be seen that the chromaticity change due to the viewing angle can be further reduced by changing the area ratio. When these figures are compared, the change in chromaticity can be minimized when the area ratio is set to 4: 6 to 5: 5. As in this example, the area ratio is preferably approximately equal, but it is more preferable to set an optimal area ratio according to the element configuration, pattern, and the like.

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

Embodiment 1 FIG.
In the present embodiment, two types of ITO are used in one pixel, that is, one organic LED element. The film thickness is set to a value that cancels out chromaticity changes due to viewing angles. The thick ITO portion is circular when viewed in plan, and the other portions are made of thin ITO. However, the present invention is not limited to this. For example, the thin ITO part may be circular when viewed in plan, and the other part may be made of thick ITO.

  FIG. 13 is a plan view of the organic LED element in the present embodiment. In order to describe the shape of ITO, the organic layer and the cathode are omitted.

  14 is a cross-sectional view taken along the line AA ′ of FIG. FIG. 15 is a cross-sectional view taken along the line BB ′ of FIG.

  As shown in FIGS. 14 and 15, ITO 2 as an anode, an organic layer 3, and a cathode 4 are formed on a glass substrate 1, and an organic LED element 5 is constituted by these. Moreover, on the glass substrate 1 between each organic LED element 5, the insulating film 6 whose section is a forward taper shape is formed. Further, on the insulating film 6 in a direction orthogonal to the ITO 2 pattern, a partition wall 7 having a reverse tapered shape in cross section is formed. Here, the insulating film 6 is provided for the purpose of preventing a short circuit between the ITO 2 and the cathode 4. The partition wall 7 is provided for the purpose of separating the organic layer 3 and the cathode 4.

In the organic LED element 5, the thickness of the ITO 2 is not uniform, and is divided into a first portion 2a having a larger thickness and a second portion 2b having a smaller thickness than the first portion. The film thickness T1 of the _first portion 2a can be set to 180 nm, for example. On the other hand, the film thickness T2 of the _second portion 2b can be set to 130 nm, for example. In the present embodiment, the ITO 2 may further have one or more portions having different film thicknesses.

  As shown in FIG. 13, the first portion 2a has a circular shape when seen in a plan view. By changing the area ratio between the first portion 2a and the second portion 2b, the change in chromaticity depending on the viewing angle can be changed. Therefore, it is preferable that the area ratio is optimal in accordance with the configuration and pattern of the organic LED element. In the present embodiment, the area ratio between the first portion 2a and the second portion 2b can be set to, for example, about 4: 6 to 5: 5.

  The organic LED element 5 can be formed as follows.

  First, ITO 2 is provided in the light emitting region on the glass substrate 1.

Specifically, a first ITO film having a film thickness corresponding to the film thickness difference (T ₁ −T ₂ ) between the first portion 2 a and the second portion 2 b is formed on the glass substrate 1. Next, the first ITO is patterned into the shape of the first portion 2a. For example, after a first ITO film with a thickness of 50 nm is formed by an evaporation method, the first ITO is patterned into a circle by using a photolithography method. In FIG. 14 and FIG. 15, the patterned first ITO is indicated by a dotted line. Next, a second ITO (not shown) having a film thickness corresponding to the film thickness T2 of the _second portion 2b is formed on the glass substrate 1 so as to cover the first ITO. For example, the second ITO can be formed with a thickness of 130 nm by vapor deposition. Next, the second ITO is patterned into the shape of the display pixel by photolithography. Through the above steps, the ITO 2 composed of the first portion 2a and the second portion 2b can be formed.

The film thickness difference (T ₁ −T ₂ ) between the first portion 2a and the second portion 2b is preferably 30 nm to 70 nm. If the film thickness difference becomes too small, it is difficult to expect the effect of canceling out the chromaticity change due to the viewing angle. On the other hand, if the film thickness difference becomes too large, a large step is generated in the ITO 2 and the film thickness of the organic layer 3 in the step portion becomes thin. As a result, a short circuit easily occurs between the ITO 2 and the cathode 4.

  Therefore, in the present embodiment, it is preferable to polish the surface of the ITO 2 after forming the second ITO. Thereby, since the level | step difference between the 1st part 2a and the 2nd part 2b can be made smooth, it can prevent that a short circuit arises between ITO2 and the cathode 4 resulting from a level | step difference.

  After the ITO 2 is formed, the insulating film 6 is formed in the non-light emitting region on the glass substrate 1 according to a known method. Subsequently, after forming the partition 7 on the insulating film 6, the organic LED element 5 can be obtained by forming the organic layer 3 and the cathode 4 in order.

  As the glass substrate 1, for example, alkali glass, non-alkali glass, or quartz glass can be used. In the present embodiment, in addition to the glass substrate, another substrate having a high visible light transmittance can be used. For example, a substrate made of a transparent material such as polyester, polycarbonate, polyether, polysulfone, polyethersulfone, polyvinyl alcohol, or a fluorine-containing polymer such as polyvinylidene fluoride and polyvinyl fluoride can be used.

Any material other than ITO can be used for the anode as long as it is a transparent metal having a high work function, an alloy thereof, or another conductive compound. For example, SnO ₂ or ZnO can be used. Even when these films are used, they can be formed in accordance with the above-described steps, like ITO.

  The insulating film 6 has an opening at a position to be a display pixel, and separates and electrically insulates ITO2. Further, it also serves to prevent the ITO 2 and the cathode 4 from being short-circuited. As the insulating film 6, for example, a polyimide resin can be used, and it can be formed by a printing method or the like.

  The partition wall 7 is made of an insulating resin such as polyimide, and is provided for the purpose of separating the organic layer 3 and the cathode 4.

  In addition, although the partition wall 7 has a reverse tapered cross-sectional shape in FIG. 1, depending on the molecular weight of the organic layer 7 formed in the upper layer, the partition wall 7 may have a cross-sectional shape such as a forward taper shape or an arch shape. Good. That is, when the organic layer 3 is formed using a low molecular weight material, film formation by a vapor deposition method is common. Therefore, the organic layer 3 with high dimensional accuracy can be formed by making the cross-sectional shape of the partition wall 7 into a reverse taper shape and depositing the material vertically from the top of the ITO 2. On the other hand, in the case of a high molecular weight material, it is necessary to form a film using a coating method such as an inkjet method. Therefore, it is desirable that the cross-sectional shape of the partition wall 7 is a forward taper shape or an arch shape in order to flow the coating solution onto the ITO 2. The partition wall 7 can be formed using a resist composition suitable for forming a desired cross-sectional shape.

  The organic layer 3 includes at least a light emitting layer, and emits white light by excitons generated by recombination of electrons and holes. Specifically, a three-layer structure including a hole transport layer, a light emitting layer, and an electron transport layer can be employed. The organic layer 3 can also have a two-layer structure in which the light-emitting layer has both hole transport properties and electron transport properties. Furthermore, in order to lower the hole injection barrier from ITO2, a structure in which one hole injection layer having a small difference in ionization potential with ITO2 is provided between the hole transport layer and ITO2 may be used. it can. These films can be formed by an evaporation method, but at least one film may be formed by a wet coating method such as a spray method, an inkjet method, a spin coating method, or a transfer method.

  Examples of the hole transport layer include N, N′-bis (1-naphthyl) -N, N′-diphenyl-1,1′-biphenyl-4,4′-diamine (NPD), N, N′— Diphenyl-N, N′-bis [N-phenyl-N- (2-naphthyl) -4′-aminobiphenyl-4-yl] -1,1′-biphenyl-4,4′-diamine (NPTE), 1 , 1-bis [(di-4-tolylamino) phenyl] cyclohexane (HTM2) and N, N′-diphenyl-N, N′-bis (3-methylphenyl) -1,1′-diphenyl-4,4 ′ -Diamine (TPD) etc. are mentioned.

  Examples of the electron transport layer include 2,5-bis (1-naphthyl) -1,3,4-oxadiazole (BND) and 2- (4-t-butylphenyl) -5- (4-biphenyl). -1,3,4-oxadiazole (PBD) and the like.

The light emitting layer is made of a material that provides a field where injected electrons and holes can be recombined and has high light emission efficiency. Specifically, tris (8-quinolinolato) aluminum complex (Alq ₃ ), bis (8-hydroxy) quinaldine aluminum phenoxide (Alq ′ ₂ OPh), bis (8-hydroxy) quinaldine aluminum-2,5- Dimethylphenoxide (BAlq), mono (2,2,6,6-tetramethyl-3,5-heptanedionate) lithium complex (Liq), mono (8-quinolinolato) sodium complex (Naq), mono (2, 2,6,6-tetramethyl-3,5-heptanedionate) lithium complex, mono (2,2,6,6-tetramethyl-3,5-heptanedionate) sodium complex and bis (8-quinolinolate) metal complexes of quinoline derivatives such as calcium complex (CAQ _2), tetraphenyl butadiene, Feniruki Kudrin (QD), anthracene, and a fluorescent substance such as perylene and coronene.

  The fluorescent material is preferably used as a dopant in combination with a host material capable of emitting light by itself. As a result, the emission wavelength characteristic of the host material can be changed, light emission shifted to a long wavelength can be achieved, and the light emission efficiency and stability of the device can be improved.

  As the host substance, a quinolinolato complex is preferable, and an aluminum complex having 8-quinolinol and a derivative thereof as a ligand is particularly preferable.

  For the cathode 4, a metal having a small work function or an alloy thereof is used. Specific examples include alkali metals, alkaline earth metals, and metals of Group 3 of the periodic table. Of these, aluminum (Al), magnesium (Mg), or alloys thereof are preferably used because they are inexpensive and have good chemical stability. These films can be formed, for example, for the vapor deposition method, and can be the cathode 4 patterned by the partition walls 7. Moreover, it can also be set as the cathode 4 patterned using the photolithography method.

  After the cathode 4 is formed, the glass substrate 1 is overlapped with another glass substrate (not shown), and these are bonded via a sealing material (not shown), and then the outer peripheral portion of the overlapped substrate. Cut and remove unnecessary parts in the vicinity. Then, it can be set as an organic LED display by making required electrical connection. Here, the substrate opposed to the glass substrate 1 is not limited to the glass substrate. For example, substrates made of other transparent materials such as polyester, polycarbonate, polyether, polysulfone, polyethersulfone, polyvinyl alcohol or fluorine-containing polymers such as polyvinylidene fluoride and polyvinyl fluoride can be used, and aluminum can be used. A substrate made of any of the above metal materials can also be used.

As described above, in this embodiment, ITO having different film thicknesses is provided in one pixel at a predetermined area ratio, and these film thicknesses (T ₁ , T ₂ ) are changed in chromaticity depending on the viewing angle. The values cancel each other. As a result, light having a different chromaticity change direction depending on the viewing angle is simultaneously extracted from one pixel. Since the viewer recognizes these lights as a mixture, it is possible to reduce the change in chromaticity depending on the viewing angle compared to the case of using only a single ITO film. Become.

  In the examples of FIGS. 13 to 15, the structure in which the thick ITO portion is circular when viewed in plan and the other portions are made of thin ITO is described. However, the present embodiment is not limited to this. In this embodiment, ITO with different film thicknesses is provided in a single pixel at a predetermined area ratio, and if these film thicknesses are values that cancel each other out chromaticity changes due to viewing angles. Good. Therefore, the thick part (or the thin part) may have a shape other than a circle when viewed in a plan view.

  In FIG. 16, the thick ITO portion (first portion 201 a) has a rectangular shape in plan view, and the other portions are made of thin ITO (second portion 201 b). It is an example. In FIG. 16, the same reference numerals as those in FIG. 13 are the same.

  In FIG. 16, portions other than the shape of the ITO 201 can be the same as those in FIGS. The thin ITO part may have a rectangular shape when viewed in plan, and the other part may be made of thick ITO.

In FIG. 16, the film thickness difference (T ₁ −T ₂ ) between the first portion 201a and the second portion 201b is preferably 30 nm to 70 nm. Moreover, although these area ratios can be made into 4: 6-5: 5, for example, it is preferable to set to an optimal value according to a structure, a pattern, etc. of an organic LED element.

  Even with the structure of FIG. 16, the change in chromaticity due to the viewing angle can be reduced as compared with the case of using only a single film thickness of ITO.

  In this embodiment, one pixel may be divided into two or four, and ITO having different film thickness may be provided for each divided pixel unit. In this case as well, ITO having different film thicknesses is provided in one pixel at a predetermined area ratio, and if these film thicknesses are values that cancel out chromaticity changes due to viewing angles, The same effect as described above can be obtained. However, in this case, it is necessary to perform pixel alignment with higher accuracy than in the case of forming a circular or rectangular pattern.

  FIG. 17 shows an example in which one pixel 11 is divided into two, the thickness of ITO in one pixel unit 11a is increased, and the thickness of ITO in the other pixel unit 11b is decreased. In FIG. 17, the same reference numerals as those in FIG. 13 are the same.

In FIG. 17, the film thickness difference (T ₁ −T ₂ ) between the thick first portion 202 a and the thin second portion 202 b is preferably 30 nm to 70 nm. Moreover, although these area ratios can be made into 4: 6-5: 5, for example, it is preferable to set to an optimal value according to a structure, a pattern, etc. of an organic LED element.

  Even with the structure of FIG. 17, the change in chromaticity due to the viewing angle can be reduced as compared with the case of using only a single film thickness of ITO.

  By the way, as described above, in order to prevent a short circuit between the ITO and the cathode due to the difference in thickness of the ITO, it is preferable to smooth the step by polishing the ITO. However, it is possible to prevent a short circuit from occurring without polishing the ITO.

  18 is a cross-sectional view taken along the line CC ′ of FIG. In this example, the insulating film 12 having a forward tapered cross section is provided at the step portion of the ITO 202. According to this configuration, since the step of the ITO 202 is covered with the insulating film 12, the steep step of the ITO 202 can be changed to a gentle step of the insulating film 12. Therefore, it is possible to prevent a short circuit from occurring with the cathode 4 without polishing the ITO 202.

Embodiment 2. FIG.
In the first embodiment, an example in which ITOs having different film thicknesses are described with a predetermined area ratio has been described. In contrast, the present embodiment is characterized in that a patterned silicon nitride (SiN _x ) film is provided in the lower layer of ITO with the ITO film thickness being constant.

FIG. 19 is a cross-sectional view of the organic LED element in the present embodiment. As shown in the figure, a patterned SiN _x film 22, an ITO 23 as an anode, an organic layer 24 and a cathode 25 are formed on a glass substrate 21, and an organic LED element 26 is constituted by these. In addition, an insulating film 27 having a forward tapered cross section is formed on the support substrate 21 between the organic LED elements 26.

In the organic LED element 26, the ITO 23 is formed with a uniform film thickness. On the other hand, the SiN _x film 22 has a refractive index close to the refractive index (1.9) of the ITO 23 by adjusting the composition. By doing so, the laminated portion 28 of the SiN _x film 22 and the ITO 23 can be considered in the same manner as the thick ITO portion in the first embodiment.

That is, the thickness _{T 3} of the stacked portion 28, ITO23 formed portion on the glass substrate 21 (hereinafter, in this embodiment, referred to as a single-layer portion.) 29 and a thickness _{T 4,} By setting the film thickness so that the chromaticity change due to the viewing angle cancels each other, and by making these portions have a predetermined area ratio, light having a different chromaticity change direction due to the viewing angle can be simultaneously emitted from one pixel. It can be taken out. Then, since these lights are mixed and recognized by the viewer, it is possible to reduce the chromaticity change due to the viewing angle as compared with the case where the SiN _x film 22 is not formed.

In the example of FIG. 19, the shape of the SiN _x film 22 can be circular when viewed in plan. For example, the SiN _x film 22 can be formed in a shape similar to the circular portion of FIG. However, the present embodiment is not limited to this. For example, the SiN _x film 22 can be formed in a shape similar to the rectangular portion of FIG. Further, one pixel may be divided into two, one pixel unit may be a laminated film of a SiN _x film and ITO, and the other pixel unit may be a single layer film of ITO.

The film thickness difference (T ₃ −T ₄ ) between the laminated portion 28 and the single layer portion 29 is preferably 30 nm to 70 nm. In other words, the thickness of the SiN _x film 22 is preferably set to 30 nm to 70 nm. The area ratio between the laminated portion 28 and the single layer portion 29 can be set to, for example, about 4: 6 to 5: 5, but is set to an optimum value according to the configuration or pattern of the organic LED element. It is preferable.

  The organic LED element 26 can be formed as follows.

First, the SiN _x film 22 is formed on the glass substrate 21. For example, after a SiN _x film is formed by an evaporation method, it is patterned into a predetermined shape by dry etching. At this time, the etching conditions are adjusted so that the cross-sectional shape becomes a forward tapered shape. Thereby, even if it does not grind | polish after forming ITO23, since the level | step difference of the lamination | stacking part 28 and the single layer part 29 can be made smooth, it prevents that a short circuit arises between the ITO23 and the cathode 25. FIG. Can do.

After the SiN _x film 22 is formed, ITO 23 is provided in the light emitting region. Specifically, ITO may be formed on the glass substrate 21 so as to cover the SiN _x film 22, and then patterned using a photolithography method. Thereafter, the organic LED element 26 can be obtained in the same manner as in the first embodiment.

In the present embodiment, any transparent film having a refractive index close to that of ITO can be used instead of the SiN _x film 22.

Embodiment 3 FIG.
In the first embodiment, an example in which ITOs having different film thicknesses are described with a predetermined area ratio has been described. On the other hand, the present embodiment is characterized in that the film thickness of the organic layer is changed while the film thickness of ITO is constant.

  FIG. 20 is a cross-sectional view of the organic LED element in the present embodiment. As shown in the figure, an ITO 32 as an anode, an organic layer 33 and a cathode 34 are formed on a glass substrate 31, and an organic LED element 35 is constituted by these. In addition, an insulating film 36 having a forward tapered shape in cross section is formed on the support substrate 31 between the organic LED elements 35.

In the organic LED element 35, the ITO 32 is formed with a uniform film thickness. On the other hand, the thickness of the organic layer 33 is not uniform, and the first portion 33a (thickness T ₅ ) having a larger thickness and the second portion 33b (thickness T ₆ ) having a smaller thickness than the first portion. And divided. The film thickness difference (T ₅ −T ₆ ) between the first portion 33a and the second portion 33b is preferably 30 nm to 70 nm. Further, the area ratio between the first portion 33a and the second portion 33b can be, for example, about 4: 6 to 5: 5. However, it is preferable to set the optimal area ratio according to the configuration and pattern of the organic LED element. In the present embodiment, the organic layer 33 may further include one or more portions having different film thicknesses.

  According to the configuration of FIG. 20, the first portion 33a and the second portion 33b can be considered in the same manner as the thick and thin portions of ITO in the first embodiment, respectively.

That is, the thickness T ₅ of the first portion 33a of the film thickness T ₆ of the second portion 33b, respectively and the film thickness cancel each other chromaticity change due to viewing angle, further, the area ratio of these portions of predetermined By doing so, it is possible to simultaneously extract light having different chromaticity change directions depending on the viewing angle from one pixel. As a result, the viewer recognizes a mixture of these lights, so that the change in chromaticity due to the viewing angle can be reduced compared to the case where the organic layer is formed with a constant film thickness. It becomes.

  In the example of FIG. 20, the shape of the first portion 33a can be circular when viewed in plan. For example, the first portion 33a can be formed in a shape similar to the circular portion of FIG. However, the present embodiment is not limited to this, and for example, the first portion 33a can be formed in a shape similar to the rectangular portion of FIG. Furthermore, one pixel may be divided into two, one pixel unit may be the first portion 33a, and the other pixel unit may be the second portion 33b.

  The organic LED element 35 can be formed as follows.

  First, ITO 32 is provided in the light emitting region on the glass substrate 31. Specifically, ITO may be deposited on the glass substrate 31 by a vapor deposition method, and then patterned using a photolithography method.

  After the ITO 32 is formed, an insulating film 36 is formed in a non-light emitting region on the glass substrate 31 according to a known method. Next, after a partition 37 is formed on the insulating film 36, an organic layer 33 is further formed.

  The organic layer 33 can have a three-layer structure including a hole transport layer, a light emitting layer, and an electron transport layer. Further, a structure in which one hole injection layer having a small difference in ionization potential from the anode is further provided between the hole transport layer and the anode can be employed.

  In the present embodiment, it is preferable that at least one of the hole transport layer and the hole injection layer is partially thick. For example, after the hole transport layer is formed by vapor deposition, a hole transport layer is further formed in a state where the portion corresponding to the second portion 33b is covered with a metal mask. Thereby, the part of the hole transport layer not covered with the metal mask can be formed thick. Next, after removing the metal mask, a light emitting layer and an electron transport layer are sequentially formed by vapor deposition.

  In order to form the organic layer 33, it is preferable to partially change the film thickness of the hole transport layer or the hole injection layer instead of the electron transport layer. In general, it is more preferable to change these layers. This is because it is considered that the effect on the environment is small. That is, since the mobility of holes is higher than that of electrons, the increase in voltage by changing the film thickness is smaller when the film thickness of the hole transport layer or hole injection layer is increased. . In addition, since the distance from the light emitting position to the cathode affects the interference of the emitted light, changing the film thickness of the electron transport layer may change the light extraction efficiency. Furthermore, since the appropriate value of the distance from the light emitting position to the cathode varies depending on the light emission color, there is a possibility that the color of the light emission color may change by changing the film thickness of the electron transport layer.

  After the organic layer 33 is formed, the organic LED element 35 can be obtained in the same manner as in the first embodiment.

  As described above, according to the present invention, portions having different distances from the substrate to the cathode are provided in one pixel at a predetermined area ratio. Since the values cancel each other, an organic LED element having a small change in chromaticity depending on the viewing angle can be obtained.

  The present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the spirit of the present invention.

  That is, the present invention provides an organic LED comprising an anode formed on a substrate, an organic layer formed on the anode and including at least a light emitting layer, and a cathode formed on the organic layer. In the element, a portion having a different distance from the substrate to the cathode is provided in one pixel at a predetermined area ratio, and this distance cancels out chromaticity changes due to viewing angles. It is a feature. Therefore, in the first to third embodiments, light from the light emitting layer is extracted from the anode side, but may be extracted from the cathode side, and may be extracted from both the anode and cathode sides. It may be. In this case, a transparent electrode such as ITO is used for the cathode as in the anode.

It is a figure which shows the viewing angle dependence of chromaticity. It is a figure which shows the viewing angle dependence of chromaticity. It is a figure which shows the viewing angle dependence of chromaticity. It is a figure which shows the viewing angle dependence of chromaticity. It is a figure which shows the viewing angle dependence of chromaticity. It is a figure which shows the viewing angle dependence of chromaticity. It is a figure which shows the viewing angle dependence of chromaticity. It is a figure which shows the viewing angle dependence of chromaticity. It is a figure which shows the viewing angle dependence of chromaticity. It is a figure which shows the viewing angle dependence of chromaticity. It is a figure which shows the viewing angle dependence of chromaticity. It is a figure which shows the viewing angle dependence of chromaticity. 1 is an example of a plan view of an organic LED element in Embodiment 1. FIG. It is sectional drawing which follows the AA 'line of FIG. It is sectional drawing which follows the BB 'line of FIG. FIG. 6 is another example of a plan view of the organic LED element in the first embodiment. FIG. 6 is another example of a plan view of the organic LED element in the first embodiment. It is sectional drawing which follows the CC 'line of FIG. 6 is a plan view of an organic LED element according to Embodiment 2. FIG. 6 is a plan view of an organic LED element according to Embodiment 3. FIG. It is a cross-sectional schematic diagram of an organic LED display device.

Explanation of symbols

1,21,31 Glass substrate 2,201,202,23,32 ITO
3, 24, 33 Organic layer 4, 25, 34 Cathode 5, 26, 35 Organic LED element 6, 27, 36 Insulating film 7 Partition 22 SiN _x film

Claims (6)

An anode formed on the substrate;
An organic layer formed on the anode and including at least a light emitting layer;
In an organic LED element comprising a cathode formed on the organic layer,
In one pixel, portions having different distances from the substrate to the cathode are provided at a predetermined area ratio,
2. The organic LED element according to claim 1, wherein the distance is a value that cancels out chromaticity changes due to viewing angles. The anode is ITO,
In one pixel has a first portion the thickness of the ITO is T _1, the thickness of the ITO is a second section which is T _2,
The first part and the second part are provided in a predetermined area ratio,
_2. The organic LED element according to claim ₁ , wherein the values of T ₁ and T ₂ are values that cancel out chromaticity changes due to viewing angles.   The organic LED element according to claim 2, wherein a step portion between the first portion and the second portion has a gentle shape.   The organic LED element according to claim 2, wherein a forward tapered insulating film is formed at a step portion between the first portion and the second portion. The anode is made of a material that transmits light from the light emitting layer,
At a predetermined location on the substrate, a transparent film having a refractive index close to that of the anode is provided so as to be covered with the anode,
The transparent film, the laminated portion of the anode and the single layer portion consisting only of the anode are provided in a predetermined area ratio,
2. The organic LED according to claim 1, wherein the thickness T _{3 of the} laminated portion and the thickness T ₄ of the single-layer portion are values that cancel each other out chromaticity changes due to viewing angles. element. In one pixel has a first portion the thickness of the organic layer is a T _5, the film thickness of the organic layer and a second portion which is T _6,
The first part and the second part are provided in a predetermined area ratio,
2. The organic LED element according to claim 1, wherein the values of T ₅ and T ₆ are values that cancel each other out of chromaticity changes due to viewing angles.

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