KR20020027931A - Electro-Luminescence Device and the Manufacturing Method - Google Patents

Abstract

PURPOSE: An organic luminescence device having the luminescence structure and a manufacturing method thereof are provided to improve the aperture rate and brightness of the organic luminescence device by allowing the light to emit to the opposite direction to which a substrate is formed. CONSTITUTION: A reflecting plate(22) is formed on the upper surface of a substrate(21) and reflects the light to the direction opposite to the substrate(21). A first electrode(23) is formed on the upper surface of the reflecting plate(22). A luminescence layer(25) is formed on the upper portion of the first electrode(23). A second electrode(27) is formed on the upper side of the luminescence layer(25). The electrode(23) comprises an anode and the second electrode(27) comprises a cathode. Otherwise, the electrode(23) comprises the cathode and the second electrode(27) comprises the anode. The cathode is made up of Al(aluminium).

Description

Organic light emitting device having a front light emitting structure and its manufacturing method {Electro-Luminescence Device and the Manufacturing Method}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a structure and a manufacturing method of an organic light emitting device, and more particularly, to an organic light emitting device having a front light emitting structure for improving light aperture and luminance by emitting light toward an upper side (the opposite direction in which a substrate is formed) and a manufacturing method thereof. It is about.

In general, Electro-Luminescence (EL) means that electrons and holes form electron-hole pairs in a semiconductor or carriers are excited to a higher energy state. It is the phenomenon that light is generated by falling back to their equilibrium state.

1 is a cross-sectional view of a general EL device using the above-described EL phenomenon, and is a cross-sectional view showing an organic EL (Electro-Luminescence) using a semiconductor layer in which electrons and holes are formed as an organic material.

In the stacked structure of the organic EL device 10, an anode 13 is formed on the substrate 11 and the substrate 11, and a cathode 15 is formed on the anode 13. The light emitting layer 17 is formed between the cathode 15 and the anode 13.

That is, as shown in FIG. 1, the electrode / light emitting layer / electrode has a structure, and the cathode 15, which is an electron injection electrode, is a metal having a work function relatively smaller than that of the anode 13; Mg, Al, etc. are used.

The reason why the metal having the low work function is used as the electron injection electrode (that is, the cathode 15) is to lower the barrier formed between the cathode 15 and the light emitting layer 17 to increase the current in the electron injection. This is because the density can be obtained.

This can increase the luminous efficiency of the device. Therefore, calcium (Ca) having the lowest work function shows high efficiency, while Al has a relatively high work function and thus has low efficiency. However, Ca has a problem of being easily oxidized by oxygen or moisture in the air, and Al is useful as a material that is stable in air.

Meanwhile. The anode 13 has a high work function and uses a transparent metal oxide to emit emitted light out of the device. The most widely used hole injection electrode is ITO (Indium Tin Oxide). The thickness is about 30 nm.

While ITO has the advantage of being transparent to light, it has the disadvantage that the deposition process is not easy. Therefore, recently, chemicallly-doping conjugated polmers including polythiophene, which show advantages in ambient stability, have been considered for use as hole injection electrodes.

At this time, by using a metal having a high work function as the material of the anode 13, it is possible to prevent the reduction of the luminous efficiency through non-emitting recombination in the anode (13).

On the other hand, mostly transparent glass is used as the board | substrate 1, and Alq3. Monomolecular organic EL such as Anthracene, poly (p-phenylenevinylene), poly (thiophene) such as polyvinphene (PT), and derivatives thereof are used, and thin film (100 nm) of the light emitting layer is used for charge emission at low driving voltage. Research is ongoing.

The organic light emitting device described above includes a passive matrix (PM) driving method and an active matrix (AM) driving method, and it is preferable to use an AM driving method in order to match the resolution of current liquid crystal displays.

In the AM method, as illustrated in FIGS. 2 and 3, a separate switching element S is applied to one pixel, and the switching element S is a thin film transistor (TFT). Widely used

However, in the organic light emitting device using the PM driving method and the AM driving method configured as described above, the light emitted from the light emitting layer emits light toward the substrate. In particular, the organic light emitting device employing the AM driving method has a switching device (TFT). There is a problem that the formed portion is not transmitted and the aperture ratio of the area that is substantially emitted is considerably lowered. Further, the phenomenon of the aperture ratio decreases further increases as the high density image quality progresses.

The present invention has been made to solve the above problems, to provide an organic light emitting device having a front light emitting structure for improving the aperture ratio and brightness by improving the structure of the direction of light emission in a direction opposite to the substrate and a method of manufacturing the same have.

In order to achieve the above object, the present invention provides a substrate, a reflective plate formed on the upper surface of the substrate, a first electrode formed on the upper surface of the reflecting plate, a light emitting layer formed on the upper surface of the first electrode; It is a first feature to include a second electrode formed on the upper surface of the light emitting layer to transmit light.

In addition, a second feature of the reflecting plate is that a plurality of recesses are formed to collect incident light.

In addition, forming a reflecting plate on the upper surface of the substrate, forming a first electrode on the upper surface of the reflecting plate, forming a light emitting layer on the upper surface of the first electrode and forming a second electrode on the upper surface of the light emitting layer A third feature is to include the step of doing the following.

1 is a cross-sectional view of a general organic light emitting device;

2 is a cross-sectional view showing a cross section of an organic light emitting device of a conventional active matrix driving method;

3 is a perspective view showing the configuration of an organic light emitting device of a conventional active matrix driving method;

4 is a cross-sectional view of an organic light emitting diode according to a first embodiment of the present invention;

5 is a cross-sectional view of an organic light emitting diode according to a second embodiment of the present invention;

6 is an enlarged view of an enlarged view of the display unit A of FIG. 5;

7 is a cross-sectional view of an organic light emitting diode according to a third embodiment of the present invention;

8 is a process chart showing a manufacturing process of the organic light emitting device shown in FIG.

9 is a process chart showing a manufacturing process of the organic light emitting device shown in FIG.

10 is a process chart showing a process in which the concave portion of the organic light emitting device according to the present invention is formed by another method;

FIG. 11 is a process diagram illustrating a manufacturing process of the organic light emitting diode illustrated in FIG. 7.

<Explanation of symbols for main parts of the drawings>

20 organic light emitting device 21 substrate

22: reflector 23: first electrode

24: first transport layer 25: light emitting layer

26: second transport layer 27: second electrode

22a: concave

Hereinafter, with reference to the accompanying drawings 4 to 11 will be described in more detail the configuration and operation of the present invention.

As shown in FIG. 4, the organic light emitting device 20 according to the present invention includes a substrate 21, and a reflecting plate 22 reflecting light in a direction opposite to the substrate 21 is formed on an upper surface of the substrate 21. The first electrode 23 is formed on the upper surface of the reflector 22, the light emitting layer 25 is formed on the first electrode 23, and the second electrode is formed on the light emitting layer 25. 27 is formed.

The first electrode 23 is composed of an anode, the second electrode 27 is composed of a cathode (hereinafter referred to as "electron" for ease of explanation), or the first electrode 23 is composed of a cathode. Preferably, the second electrode 27 is composed of an anode (hereinafter referred to as "the latter" for ease of explanation), and the cathode constitutes an element using a material smaller than the work function of the anode.

The anode is preferably formed of a transparent material to allow light to pass through the reflecting plate 22. ITO is used as the material, and aluminum is used as the cathode.

In the former, the aluminum metal film forming the cathode may be thinly formed to a thickness of about 20 nm to 100 nm so that light reflected through the reflecting plate 22 can pass therethrough.

In the latter case, care must be taken when using the ITO as an anode since the light emitting layer 25 is sensitive to external impacts. That is, in the formation of the ITO layer, the deposition rate is initially reduced to minimize the impact on the light emitting layer 25, and then the deposition rate is increased to form the anode.

Next, as illustrated in FIGS. 5 and 6, a plurality of recesses 22a are further configured to collect the EL light incident on the reflecting plate 22, and the reflecting plate 22 may be formed. As a material, it is preferable to use an opaque metal material as a material having a property of reflecting light.

The metal material of the reflective plate 22 may be aluminum (Al), chromium (Cr), molybdenum (Mo), tungsten (W), titanium (Ti), tantalum (Ta), or an alloy thereof.

The substrate 21 may be made of a transparent material, but most preferably, the substrate 21 is made of an opaque material.

In addition, in the above-described structure, the first and second transport layers 24 and 26 may be additionally configured in the light emitting layer 25 as shown in FIG. 7.

In other words, the hole transport layer called HTL (Hole Transporting Layer) and the electron transport layer called ETL (Electron Transporting Layer) are formed to contact the anode and the cathode, respectively.

In the former case, the first transport layer 24 forms the HTL, the second transport layer 26 corresponds to the ETL, and in the latter case, the reverse structure is described above.

ETL uses Oxadiazole derivatives and HTL uses Diamine derivative TPD and photoconductive polymer poly (9-vinylcarbazole). Combinations of these transport layers provide the following effects:

First, it is possible to increase the quantum efficiency and to lower the driving voltage through the two-step injection process of passing through the first and second transport layers 24 and 26 without carriers being directly injected into the light emitting layer 25.

Second, when the electrons and holes injected into the light emitting layer 25 are moved to the opposite electrode, that is, the cathode and the anode, through the light emitting layer 25, the electrons and holes are blocked by the opposite transport layer, that is, HTL and ETL, to control recombination, thereby improving luminous efficiency. Can be.

Third, at the interface between the light emitting layer and the singlet exection electrode generated by recombination of electrons and holes, it prevents quenching.

Here, quenching refers to a phenomenon in which light emission of the material is slowed down as the light emitting molecules near each other.

Next, the manufacturing process of the organic light emitting device configured as described above will be described.

As shown in FIG. 8, first, any one of aluminum (Al), chromium (Cr), molybdenum (Mo), tungsten (W), titanium (Ti), and tantalum (Ta) may be disposed on an upper surface of the substrate 21. The reflective plate 22 is formed by depositing an alloyed metal. (S20)

The reflecting plate 22 is deposited by vacuum deposition or sputtering.

Next, after the deposition of the reflector 22 as described above, the first electrode 23 is formed on the upper surface of the reflector 22 (S30), the thin film of the organic light emitting material on the upper surface of the first electrode 23 To form a light emitting layer 25 (S40).

The thickness of the light emitting layer 25 is usually determined according to the material from several tens of nm to several hundred nm, and the thin film is formed by vacuum deposition, spin coating, ink jet printing, and dipping. By method

After forming the emission layer 25 as described above, the second electrode 27 is formed (S50).

The reflective plate 22 may be formed in a flat plate shape, but as shown in FIG. 9, a plurality of recesses 22a may be formed to collect light incident from the light emitting layer 25.

The concave portion 22a may be formed by applying a photosensitive resin PR such as a photoresist onto the upper surface of the substrate 21 before depositing the reflective plate 22 and then applying a pattern S21 to form a mask on which a pattern P is formed. (M) is aligned on the upper surface of the photosensitive resin (PR) to undergo an exposure process (S22), after which the photosensitive resin is developed using a developer, and put into a heating furnace to heat treatment at high temperature The upper side of the photosensitive resin PR forming the cylindrical is melted to form a recess (S23).

When the concave portion is formed by the heat treatment as described above, the overcoat film O is laminated on the upper surface thereof, and the reflecting plate 22 is formed on the upper surface thereof to form the reflecting plate 22 having the concave portion 22a. (S24 )

In the above description, the photosensitive resin (PR) and the overcoat film (O) is applied by a spin coating technique that is most suitable for strict thickness control, and the reflector plate 22 is sputtered by a sputtering technique. Is deposited.

In the above description, the formation of the concave portion 22a is not limited to the above-described method. As shown in FIG. 10, a plurality of concave portions 22a formed of silicon (Si) or plastic (Plastic) are formed on the upper surface of the substrate 21. It can form by the method of apply | coating the thermosetting resin (A) which disperse | distributed the beads (B).

The thermosetting resin (A) is made of acrylic (Acryl), BCB (Benzocyclobutene).

Next, as shown in FIG. 11, the process of stacking the first transport layer 24 on the upper surface of the first electrode 23 in the aforementioned stacking process (S60), and forming the second transport layer on the upper surface of the light emitting layer 25. It is preferable to further include the step (S70).

In addition, in the above-described structure, since the reflecting plate 22 is for the purpose of reflecting only the EL light, it is preferable to further configure an insulating film or a planarizing film between the reflecting plate 22 and the first electrode 23.

Although not shown in the above-described structure, the switching element is configured to be in contact with each anode.

In the organic light emitting device 20 configured as described above, as the metal film is deposited on the upper surface of the substrate 21 to form the reflector 22, the light emitted from the light emitting layer 25 is reflected through the reflector 22 and the substrate 21. In the conventional structure that is projected to the lower side of the substrate 21 by implementing the projection in the upward direction of), it is completely reflected in the upward direction of the substrate 21 that light has not transmitted through the area where the switching element S is formed. To improve the aperture ratio and luminance.

In addition, the reflective plate 22 is formed to have a plurality of recesses 22a to collect light incident from the light emitting layer 25 to increase luminance.

That is, since the concave portion 22a concentrates the EL light incident in the vertical direction or at an angle and reflects it upward, the brightness is improved and the power consumption is reduced as the brightness is improved (see FIG. 6).

By utilizing the advantage of increasing the brightness by the concave portion 22a as described above by applying to a personal terminal such as a mobile phone or PDA (Personal Digital Assistant) that does not matter the viewing angle used by one person watching the terminal from the front Its utilization can be maximized.

As described above, the present invention forms a reflecting plate on the upper surface of the substrate so that the light emitting layer does not pass through the substrate and implements a structure in which the light is reflected in the opposite direction of the substrate, so that the switching element is for each one pixel. In the formed active matrix driving method, light that has not passed by the switching element may be reflected upwards, thereby improving aperture ratio and luminance.

In addition, by forming a plurality of recesses for collecting the light in the reflecting plate to reflect the light in the vertical direction of the substrate after the emitted light is collected by the recessed portion can greatly improve the brightness and contrast, and thus consume It will reduce power.

Claims (17)

Board; A reflection plate formed on an upper surface of the substrate; A first electrode formed on an upper surface of the reflecting plate; An emission layer formed on an upper surface of the first electrode; An organic light emitting device, characterized in that it comprises a second electrode formed to transmit light on the upper surface of the light emitting layer. The method of claim 1, And the first electrode is an anode, and the second electrode is a cathode. The method of claim 1, The first electrode is a cathode, the second electrode is an organic light emitting device, characterized in that the anode. The method of claim 1, The reflective plate is characterized in that a plurality of recesses are formed to collect the incident light. The method of claim 1, The reflector may be made of any one of aluminum (Al), chromium (Cr), molybdenum (Mo), tungsten (W), titanium (Ti), tantalum (Ta), or a metal obtained by synthesizing them. Organic light emitting device. The method of claim 1, The substrate is an organic light emitting device, characterized in that the opaque material. The method of claim 2 or 3, The light emitting layer is an organic light emitting device, characterized in that the electron transport layer on the side in contact with the cathode, the hole transport layer is further configured on the side in contact with the anode. The method of claim 2 or 3, The anode is an organic light emitting device, characterized in that a material having a larger work function than the cathode is used. The method of claim 8, The anode is an organic light emitting device, characterized in that formed of ITO. The method of claim 8, The cathode is an organic light emitting device, characterized in that formed of aluminum. Forming a reflector on an upper surface of the substrate; Forming a first electrode on an upper surface of the reflecting plate; Forming a light emitting layer on an upper surface of the first electrode; And forming a second electrode on the upper surface of the light emitting layer. The method of claim 11, And forming a plurality of recesses in the forming step of the reflecting plate. The method of claim 11, And forming a first transport layer on the top surface of the first electrode, and forming a second transport layer on the top surface of the light emitting layer. The method of claim 12, The concave portion is coated with a photosensitive resin on the upper surface of the substrate, and exposed by aligning a mask having a pattern formed on the upper surface of the photosensitive resin, and then developing the photosensitive resin using a developer and heat treatment, and then over the heat treated upper surface A method of manufacturing an organic light emitting device, characterized in that formed through the process of forming a code film. The method of claim 12, The concave portion is formed by coating a thermosetting resin in which a plurality of beads are dispersed on the upper surface of the substrate. The method of claim 15, The thermosetting resin is a method of manufacturing an organic light emitting device, characterized in that acrylic or BCB. The method of claim 15, The bead is a method of manufacturing an organic light emitting device, characterized in that made of silicon or plastic.