JP4183427B2 - Electroluminescence element - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an electroluminescence (hereinafter referred to as EL) element, and more particularly to a light extraction structure thereof.
[0002]
[Prior art]
In recent years, with the diversification of information equipment, there has been an increasing demand for flat display elements that consume less power than commonly used CRTs (cathode ray tubes). As one of the flat display elements, an EL element having features such as high efficiency, thinness, light weight, and low viewing angle dependency has been attracting attention, and a display using the EL element has been actively developed.
An EL element is a self-luminous element that emits light when an electric field is applied to a fluorescent compound. An inorganic EL element using an inorganic compound such as zinc sulfide as a light-emitting layer and an organic compound such as diamines as a light-emitting layer are used. The organic EL element is roughly classified.
In particular, organic EL elements are easy to be colored and are expected to be applied to display devices for portable terminals in recent years because of their advantages such as operating at a much lower DC current than inorganic EL elements.
[0003]
The organic EL element injects holes from the hole injection electrode toward the light emitting layer and injects electrons from the electron injection electrode toward the light emitting layer, and the injected holes and electrons are recombined. An organic molecule constituting the emission center is excited, and fluorescence is emitted when the excited organic molecule returns to the ground state.
Accordingly, since the organic EL element can change the emission color by selecting the fluorescent material constituting the light emitting layer, there is an increasing expectation for application to multi-color and full-color display devices.
In recent years, as shown in FIG. 8, a so-called top emission structure in which light is extracted from the element formation surface side, that is, the side opposite to the substrate 1, has been proposed for organic EL displays. In this structure, a switching circuit element composed of a thin film transistor (TFT) is formed in an amorphous silicon thin film layer 2 formed on the surface of a glass substrate 1, and a silicon oxide film as a planarizing film 3 formed on the upper layer. In the pixel region partitioned by the partition walls, a first electrode 4 made of an indium tin oxide (ITO) layer or the like, a luminescent material layer 5, and a lithium fluoride layer and aluminum formed on the luminescent material layer 5 are formed. A second electrode layer 6 having a two-layer structure with a layer, a protective film (not shown) made of a silicon oxide film having a thickness of 1 micron formed thereon by a photo-CVD method, and a sealing layer 7 It consists of and. This structure has an advantage that the light emission area can be increased without being affected by the arrangement of the drive circuit section 2 such as a thin film transistor (TFT) formed on the substrate.
[0004]
In order to realize this top emission structure, the characteristics of the cathode formed on the surface side facing the substrate on the emission surface side are important. Therefore, as this electron injection cathode, an electrode structure having a two-layer structure of an inner layer composed of a 0.2 to 2 nm lithium fluoride (LiF) layer and an outer layer composed of a 0.2 to 4.0 nm aluminum layer is used (special feature). This method can be realized by a method such as Japanese Laid-Open Patent Application No. 2001-52878).
[0005]
[Problems to be solved by the invention]
However, usually, a drive circuit such as a TFT is formed on the substrate side, and the pixels are often covered with a planarizing film 3 as shown in FIG.
[0006]
It is impossible to take out light emission in such a portion of the flattening film, and the flattening film portion is a non-light emitting region, and there is a limit to increase in the amount of light.
[0007]
The above problem is particularly serious in the top emission structure. However, even in the case of an organic EL display having a structure in which light is extracted to the substrate side, the wiring layer is caused to travel between the pixels and the non-light emitting region is used. Some areas have become.
[0008]
The present invention has been made in view of the above circumstances, and an object of the present invention is to efficiently extract the light emitted from the light emitting portion, increase the light amount, and provide an EL element with light emission efficiency.
[0009]
[Means for Solving the Problems]
Therefore, in the present invention, a light-emitting portion having a light-emitting substance layer sandwiched between an anode and a cathode is disposed on the surface of the substrate, and a micro-chip disposed on the light-emitting portion corresponding to the light-emitting portion. A sealing layer having a lens is provided, and light from the light emitting portion is extracted through the microlens.
[0010]
According to such a configuration, the light from the light emitting unit is extracted through the microlens, so that the light can be expanded to the non-light emitting unit, and the light emission efficiency can be increased. Accordingly, the amount of light can be increased, and a high-density display device without gaps can be formed.
[0011]
Preferably, the sealing layer is formed of a glass substrate attached on the light emitting unit, and a lens layer having a refractive index gradient formed at a predetermined depth by ion transfer from the glass substrate surface. It is characterized by comprising.
[0012]
According to this configuration, since the lens is integrally formed on the sealing layer, it is possible to obtain a highly efficient EL element with a small number of components and easy positioning.
[0013]
Preferably, the sealing layer is arranged such that the optical axis of the microlens is positioned at the center of each pixel surrounded by a partition wall.
[0014]
According to such a configuration, since the optical axis of the microlens is configured to be positioned at the center of each pixel, it is possible to efficiently extract light.
[0015]
Preferably, the surface of the sealing layer is covered with a light shielding film having an opening corresponding to the position where the light emitting unit is disposed.
[0016]
According to such a configuration, it is possible to ensure pixel separation.
[0017]
Preferably, the light shielding film is made of a Ti thin film and is a mask layer for forming the lens layer.
[0018]
According to such a configuration, the Ti thin film is formed, the refractive index gradient layer is formed by a method such as ion transfer using the Ti thin film as a mask, and the lens layer is formed, so that the alignment between the mask layer and the light shielding film is unnecessary. Thus, an EL element with high efficiency and high reliability can be formed with high productivity.
[0019]
Preferably, a color filter layer laminated on the surface of the sealing layer is provided.
[0020]
According to such a configuration, since the filter layer is integrally formed with the sealing layer, it is possible to reduce the thickness and improve productivity.
[0021]
Preferably, the color filter layer is formed by filling an opening of the mask layer by an ink jet method.
[0022]
According to such a configuration, the color filter layer is filled in the concave portion that is the opening of the mask layer, so that it is possible to mount with extremely high accuracy without color misregistration.
[0023]
Preferably, the substrate includes a lens layer having a refractive index gradient formed at a predetermined depth by ion transfer from the surface of the substrate on a surface facing the surface where the light emitting unit is formed. It is characterized by.
[0024]
According to such a configuration, the lens layer constituting the microlens is formed on the substrate in advance, and the light emitting portion may be formed on the side opposite to the surface on which the lens layer is formed. In addition, a highly reliable EL element can be formed with high productivity. In the case of a structure that extracts light to the substrate side, it is rare to be stacked on a glass substrate, such as by attaching a driving circuit such as a TFT externally, but when an inter-pixel region is used for wiring between pixels In this portion, although it is a non-light emitting area, the pixel area can be enlarged by a microlens.
[0025]
Desirably, the substrate is covered with a light shielding film having an opening corresponding to a position where the light emitting unit is disposed on a surface facing the surface where the light emitting unit is formed.
[0026]
Preferably, the light shielding film is made of a Ti thin film and is a mask layer for forming the lens layer.
[0027]
Preferably, a color filter layer laminated on the surface of the sealing layer is provided.
[0028]
Preferably, the color filter layer is formed by filling an opening of the mask layer by an ink jet method.
[0029]
Preferably, the light emitting material layer is an organic material layer.
[0030]
DETAILED DESCRIPTION OF THE INVENTION
Next, an embodiment of a method for producing an organic EL element of the present invention will be described in detail with reference to the drawings.
[0031]
(First embodiment)
FIG. 1 is a cross-sectional view showing the configuration of the organic EL device of the present invention, FIGS. 2A to 2C are cross-sectional views showing the manufacturing process, and FIGS. 3 to 5 show the manufacturing process of the microlens. FIG.
[0032]
As shown in FIG. 1, the organic EL element of the present invention forms a switching circuit element composed of a thin film transistor (TFT) in an amorphous silicon thin film layer 2 formed on the surface of a glass substrate 1, and is formed in this upper layer. A first electrode 4 made of an indium tin oxide (ITO) layer having a film thickness of 80 nm, a light emitting material layer 5, and a light emitting layer are formed in a pixel region partitioned by using the silicon oxide film 3 as the planarized film as a partition. 5, a second electrode layer 6 formed of a two-layer structure of a lithium fluoride layer having a thickness of 2 nm and an aluminum layer having a thickness of 40 nm, and a thickness formed by the photo-CVD method on the upper layer. A protective film (not shown) made of a 1 micron silicon oxide film and a 700 μm thick glass formed on the upper layer, and a lens layer 8 constituting a microlens corresponding to each pixel on the upper surface. It is composed of a sealing layer 7 was painting. The luminescent material layer 5 is coated in R, G, and B colors. An opening is formed on the surface of the sealing layer 7 corresponding to the lens layer 8, and a region between the openings is covered with a light shielding film 9 made of a Ti thin film. The opening surrounded by the light shielding film 9 forms a recess. When a layer that emits white light is used as the light emitting material layer 5, a red filter layer, a green filter layer, and a blue filter are formed in the recess. It is formed. Here, the pixel pitch is 106 μm, and the number of pixels is 640 × 480.
[0033]
The light emitting material layer that emits white light includes, for example, a hole transport layer made of an aromatic diamine having a thickness of 20 nm, a hole block layer made of a triazole derivative having a thickness of 3 nm, and a green light emitting layer made of an aluminum quinolinol complex having a thickness of 20 nm. And a red light emitting layer formed by doping a 20 nm thick aluminum quinolinol complex with Nile Red.
[0034]
According to such a configuration, since the microlens is formed integrally with the sealing layer and the microlens is formed corresponding to each pixel, each microlens defined by the partition formed by the planarization film 3 is formed. The light emitting region of the pixel can be enlarged and efficiently taken out to the sealing layer side. Here, an example of an element using a light emitting material layer 5 that emits white light and provided with a color filter will be described.
[0035]
Next, the manufacturing process of this organic EL element is demonstrated.
[0036]
First, as shown in FIG. 2 (a), the glass substrate 1 on which the thin film transistor is formed is mounted on a normal vacuum deposition apparatus, the degree of vacuum is 10 ⁻⁴ Pa or less, and the vacuum deposition method using a resistance heating boat is used. A first electrode 4 made of an indium tin oxide (ITO) layer having a thickness of 80 nm is formed on the surface of the glass substrate 1 using a metal mask. Thereafter, a silicon oxide film as a planarizing film 3 is formed.
[0037]
Subsequently, as shown in FIG. 3B, the evaporation source is switched without breaking the vacuum, a desired metal mask is mounted, a hole transport layer made of an aromatic diamine having a thickness of 20 nm, and a film having a thickness of 3 nm. A hole blocking layer made of a triazole derivative, a green light emitting layer made of an aluminum quinolinol complex with a thickness of 20 nm, and a red light emitting layer made by doping a 20 nm thick aluminum quinolinol complex with Nile Red are sequentially laminated.
[0038]
After that, as shown in FIG. 2C, the evaporation source is further switched without breaking the vacuum, and a desired metal mask is mounted, and the lithium fluoride layer 6a having a thickness of 2 nm and the aluminum layer 6b having a thickness of 40 nm are mounted. A second electrode layer 6 having a two-layer structure is formed.
[0039]
The glass substrate on which the layers up to the second electrode layer 6 are thus formed is irradiated with ultraviolet light L having a wavelength of 172 nm using, for example, a photo-CVD apparatus, and (CH ₃ ) ₃ SiOSi (CH ₃ ) A raw material gas is supplied to ₃ to form a protective film (not shown) made of a silicon oxide film having a thickness of 1 μm, and an organic EL element is formed.
[0040]
Then, the formation method of a sealing layer is demonstrated.
[0041]
First, a glass substrate 7 made by Schott, designated as B-270 having a thickness of 700 μm, is prepared, and openings O having an opening diameter of 90 μm are two-dimensionally arranged as shown in FIGS. 3 (a) and 3 (b). The titanium thin film 9 having a thickness of 50 μm and a width of 16 μm is pasted. Here, the minimum interval of the openings O is 16 μm.
[0042]
Then, as shown in a sectional view of the apparatus in FIG. 4, a small container 200 having the glass substrate 7 set at the bottom is filled with a mixed nitric acid molten salt 20 of zinc, potassium or thallium at 600 ° C. Is further immersed in a large container 100 filled with a mixed nitric acid molten salt 20 of potassium or thallium, and a voltage of 7 V is applied between the anode 103 immersed in the large container 100 and the cathode 104 immersed in the small container 100. Is applied to diffuse potassium ions in the molten salt into the glass.
[0043]
By soaking for about 8 hours in this way, a hemispherical lens layer 8 composed of a layer having a refractive index gradient is formed in the opening O having an opening diameter of 90 μm, as shown in FIGS. Is done. This refractive index gradient has the highest refractive index at the center on the surface of the hemisphere.
[0044]
Then, while leaving the titanium thin film 9 as a light-shielding film as it is, the filter layers 10R, 10G, and 10B are sequentially formed from the ink-jet heads 11R, 11G, and 11B of each color by an ink-jet method as shown in FIG. A sealing layer 7 including a color filter layer and a microlens is formed.
[0045]
The sealing layer 7 is positioned on the glass substrate 1 and bonded so that the optical axis of the sealing layer 7 comes to the center of the pixel of the organic EL element formed in the step of FIG.
[0046]
In this way, an organic EL element sealed with a sealing layer including a microlens array is efficiently formed.
[0047]
According to this organic EL element, the light from the light emitting layer can be enlarged by the microlens, and it can be seen as if the light is emitted from the non-light emitting portion, and the display area can be enlarged. In addition, since the microlens array and the color filter layer are integrated with the sealing layer, it is possible to form an extremely thin and highly efficient display device without any positional displacement.
[0048]
Although the silicon oxide film is formed as the protective film in the first embodiment, a two-layer film including a silicon nitride film as well as the silicon oxide film may be formed. In this case, it can be easily performed by supplying N ₂ gas or NH ₃ gas. However, when the silicon oxide film of the first layer is formed, high power light irradiation is performed, and when the silicon nitride film is formed, the light is small. By switching to power and forming a protective film while irradiating light, impurities at the interface between the light emitting material layer and the electrode layer are further removed, and a highly efficient organic EL element is formed.
[0049]
As described above, according to the first embodiment of the present invention, the organic EL element having the top emission structure in which light is extracted from the surface side facing the substrate, that is, the surface side has been described. Needless to say, the present invention can also be applied to the case of taking out.
[0050]
In addition, although the color filter was integrally formed, it cannot be overemphasized that it may form separately and may make it stick on a sealing layer.
[0051]
Moreover, although the titanium thin film as a mask used for forming the lens layer is used as it is as the light shielding film, the mask may be formed of a resin film such as polyimide without being limited thereto. In this case, it is necessary to form a light shielding film separately. Further, bumps such as polyimide may be formed for forming the color filter layer, and the color layer may be color-coded using this bump as a partition. The bumps may be formed to have a width of about 16 μm so as to form the same pattern shape as the titanium thin film.
[0052]
(Second Embodiment)
That is, this organic EL element is an element having a structure for extracting light from the substrate side, as shown in FIG. 7, and the lens layer 8 formed in the steps shown in FIGS. 3 to 5 in the first embodiment. In the same manner as in the first embodiment, on the back surface side of the glass substrate 7 on which the color filter layers 10R to 10B and the light shielding film 9 are formed, that is, on the surface opposite to the lens layer forming surface, as shown in FIG. The second electrode 16, the luminescent material layer 15, and the first electrode 14 are sequentially laminated on the back side of the glass substrate 7 in the same manner as shown in FIGS. .
[0053]
In this structure, since light is extracted to the substrate side, a driver circuit such as a TFT is formed outside the display region or formed externally.
[0054]
Other portions are formed in the same manner as in the first embodiment.
[0055]
According to such a configuration, since the lens layer and the color filter layer are integrally formed on the support substrate constituting the light emitting unit, it is possible to further reduce the thickness.
[0056]
Furthermore, although the organic EL element has been described in the first and second embodiments, the present invention can also be applied to an inorganic EL element in which a light emitting material layer is formed of an inorganic material layer.
[0057]
In the first and second embodiments, the lens layer is formed in the sealing film, but may be formed separately and attached.
[0058]
【The invention's effect】
As described above, according to the present invention, since the microlens is arranged in the sealing film, light can be extracted from the non-light emitting portion, and there is no high-density display area without a gap. Can be provided.
[Brief description of the drawings]
FIG. 1 is a diagram showing an organic EL element according to a first embodiment of the present invention.
FIG. 2 is a diagram showing a manufacturing process of the organic EL element according to the first embodiment of the present invention.
FIG. 3 is a diagram showing a manufacturing process of a sealing layer used in the organic EL element according to the first embodiment of the present invention.
FIG. 4 is a diagram showing a manufacturing process of a sealing layer used in the organic EL element according to the first embodiment of the present invention.
FIG. 5 is a diagram showing a manufacturing process of a sealing layer used in the organic EL element according to the first embodiment of the present invention.
FIG. 6 is a diagram showing a manufacturing process of a sealing layer used in the organic EL element according to the first embodiment of the present invention.
FIG. 7 is a diagram showing an organic EL element according to a second embodiment of the present invention.
FIG. 8 is a diagram showing a conventional organic EL element.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Organic EL element 2 Board | substrate 3 1st electrode 4 Luminescent substance layer 5 2nd electrode 6 Protective film

Claims (3)

A sealing unit having a light emitting part formed by sandwiching a light emitting material layer between an anode and a cathode on the surface of the substrate and having a microlens disposed on the light emitting part corresponding to the light emitting part. A lens layer having a refractive index gradient formed at a predetermined depth by ion transfer so that the light from the light emitting portion is extracted through the lens layer. An electroluminescence element configured as follows:
The surface of the sealing layer is covered with a light shielding film having an opening corresponding to the position where the light emitting unit is disposed, and the light shielding film is a mask layer for forming the lens layer ,
An electroluminescence element comprising a color filter filled in an opening of the light shielding film . A light emitting portion is formed on the substrate surface by sandwiching a light emitting material layer between an anode and a cathode, and ions are transferred from the substrate surface to the opposite surface side of the surface where the light emitting portion of the substrate is formed. An electroluminescent element comprising a lens layer having a refractive index gradient formed at a predetermined depth,
The substrate is covered with a light-shielding film having an opening corresponding to an arrangement position of the light-emitting part on the opposite surface side of the surface on which the light-emitting part is formed, and the light-shielding film is a mask for forming the lens layer It is a layer,
An electroluminescence element comprising a color filter filled in an opening of the light shielding film .   The electroluminescent element according to claim 1, wherein the light shielding film is made of a Ti thin film.

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