KR20050067947A - Organic electroluminescent device - Google Patents

Abstract

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to organic electroluminescent devices (hereinafter referred to as " organic EL devices ") and, more particularly, to increasing the uniformity of the anode surface when forming organic EL devices. The present invention relates to an organic EL device in which a positive electrode is formed, and then a thin insulating film is formed thereon to make the current density of the panel of the organic EL device uniform, thereby preventing short circuit between the positive electrode and the negative electrode.

Description

Organic EL device

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to organic electroluminescent devices (hereinafter referred to as " organic EL devices "), and more particularly, to increase the uniformity of the cathode surface when forming organic EL devices. In order to form a thin insulating film on the positive electrode, the present invention relates to an organic EL device which prevents short circuit between the positive electrode and the negative electrode by making the current density of the panel of the organic EL device uniform.

In general, an organic EL device is formed by sequentially forming a transparent anode, an organic light emitting layer, and a metal cathode on a glass substrate on a glass substrate, and then applying a voltage between the cathode and the cathode. When the injected electrons and holes are recombined and then excited, the light is generated in the process of energy transfer to the ground state. The light emission principle is faster than conventional liquid crystals. It is light in weight and very good in brightness, making it a popular next-generation display.

The basic structure of a general organic EL element is described below.

An anode is formed on a transparent substrate formed of a transparent material such as quartz, and a hole injection layer and a hole transporting layer are sequentially formed thereon.

In this case, the positive electrode is easy to inject holes due to the large work function, and metal oxide films such as indium tin oxide (ITO) and indium zinc oxide (IZO) having transparent characteristics in the visible light range. After forming using, a process of reducing roughness is performed.

After the ITO is formed on the substrate to a thickness of 1500 kPa, the polishing process and the oxygen plasma etching process are performed to remove about 10% of the deposition thickness. For example, the polishing process removes about 80 kPa of the thickness. It is desirable to improve the roughness by removing the thickness of about 50 μs by an oxygen plasma etching process.

The hole injection layer is a cooper phthalate which has a similar value between the work function of the ITO used as the positive electrode and the highest occupied molecular orbital (HOMO) while facilitating hole injection in the device. Cyanine (copper phthalocyanine (CuPC) or phenyl amine compounds such as 4,4,4-tri (3-methylphenyl-phenylamino) triphenylamine (4,4 ', 4 "-Tris (3-methylphenyl- phenylamino) -triphenylamine; m-MTDATA).

The hole transporting layer is α-NPD or N, N'-diphenyl-N, N'-bis (3-methylphenyl) -1,1'-diphenyl-4,4 'to transport holes injected from the positive electrode to the light emitting layer. -Diamine (N, N'-dipheny-N, N'-bis (3-methyl phenyl) -1,1'-diphenyl-4,4'-diamine; TPD) is used.

An organic emitting layer is formed on the hole transport layer.

In the organic light emitting layer, excitons are formed by holes injected from a positive electrode and electrons injected from a negative electrode, and in this case, an intrinsic wavelength of an organic material applied to the light emitting layer and a composition ratio of a host and a dopant are controlled. Thus, emission colors of various specific wavelengths can be realized from excitons.

The organic light-emitting layer forming material is used in the case of red (4-dicyanomethylene-6-cp-julolidinostyryl-2-tert-butyl-4H-pyran; DCJTB), and in the green (poly) (Phenylene vinylene) (PPV) and aluminum trinorol (8-hydroxyquinoline; Alq ₃ ); PPP, PF, PFV and Spiro-PF (blue) spiro-PF) and the like.

An electron transporting layer and an electron injection layer are sequentially formed on the organic emission layer.

The electron transport layer uses 1,2,3-triazole (1,2,4-triazole) or aluminum kinolinol having characteristics as an electron transporter to smoothly transport electrons supplied from the negative electrode.

In addition, a metal having a low work function, such as magnesium (Mg) or calcium (Ca), or a metal having a high work function but stable in the process and easy to deposit, such as aluminum (Al), is used on the ion insulating layer. To form a metal cathode.

As described above, in the manufacture of the organic EL device, to improve the surface uniformity of the ITO electrode by forming an ITO pattern, which is a positive electrode, and then performing a polishing process and an oxygen plasma etching process before forming the hole injection layer. The lower the roughness of the surface of the ITO, the more the current density inside the device does not rush to either side, so as to appear evenly.

However, in the oxygen plasma etching process as described above, there is a limit to improving the uniformity of the surface of the positive electrode, so that a certain uneven portion may be formed on the upper portion of the positive electrode. This problem causes a local current density difference, and this difference As a result, the electrode material migrates toward the opposite negative electrode, resulting in a short circuit between the positive electrode and the negative electrode.

The present invention is an organic EL device capable of preventing the short circuit between the positive electrode and the negative electrode by bringing uniformity of the surface of the positive electrode by forming a thin insulating film on top of the positive electrode after forming a positive electrode during the study to solve the above-mentioned brief problem The purpose is to provide.

Moreover, an object of this invention is to provide the method of manufacturing the said organic electroluminescent element.

In order to achieve the above object, the present invention provides an organic EL device having a thin insulating film formed on the positive electrode so that the current density is uniform.

Hereinafter, the present invention will be described in detail.

The present invention provides an organic EL device in which a positive electrode, an insulating film for planarizing a positive electrode surface, an organic light emitting layer, and a negative electrode are sequentially formed on a transparent substrate.

In this case, the insulating film is to make the surface of the positive electrode more uniform, and uses a parylene-based compound, for example, poly (2-chloro-1,4-dimethyl benzene) (poly (2- chloro-1,4-dimethyl benzene)), poly (1,4-dichloro-2,5-dimethylbenzene) (poly (1,4-dichloro-2,5-dimethylbenzene)) and poly (2-fluoro- 1,4-dimethylbenzene) (poly (2-fluoro-1,4-dimethylbenzene), preferably poly (para-xylene) (poly (para-xylene)) is used.

The insulating film may be formed using a chemical vapor deposition (CVD) method at a temperature condition in which a substance used as a dimer is decomposed into a monomer, and is preferably 1 to 50 kPa, preferably 1 to 30 kPa. It is deposited to a thickness.

In this case, the parylene refers to a polymer formed by a CVD process in a vacuum, such a parylene-based compound not only has a low dielectric constant and electrical insulating properties, but also high light transmittance, high reliability and uniformity regardless of the shape of the mother As a material capable of forming a coating film of one thickness, it is a material capable of coating all existing objects such as battery electronics, semiconductors, and medical optical devices.

The process of deposition of parylene is such that the dimer submerged in the sublimation unit by the temperature rise sublimes into gaseous dimer, and the sublimed dimer passes through the high temperature thermal decomposition zone and decomposes into gaseous monomers. The monomers are transferred to the deposition unit and are deposited while forming a polymer on the mother surface to be deposited.

In the present invention,

Forming a positive electrode on the organic substrate;

Forming an insulating film on the positive electrode;

Sequentially forming a hole injection layer and a hole transport layer on the insulating film;

Forming an organic emission layer on the electron transport layer;

Sequentially forming an electron transporting layer and an electron injection layer on the organic emission layer; And

It provides a method for manufacturing an organic EL device comprising the step of forming a negative electrode on the electron injection layer.

In this case, after the positive electrode forming step, the positive electrode surface may further comprise the step of polishing using a polisher.

DETAILED DESCRIPTION Hereinafter, the present invention will be described in detail with reference to the accompanying drawings, which is a schematic view for explaining the configuration of an organic EL element.

Referring to FIG. 3, a positive electrode 31 is formed on the substrate 30 to a thickness of 1500 μs, a polishing process is performed, and a thin insulating layer 32 is formed on the upper portion thereof to a thickness of about 15 μs. At this time, the positive electrode is formed using a metal oxide film such as ITO and IZO, and then, it is preferable to remove the thickness of about 80 kHz of the positive electrode formed by the polishing process.

In addition, the insulating film is formed by a CVD method using a thermal decomposition method of a dimer into monomers.

Thereafter, the hole injection layer 33, the hole transport layer 35, and the organic light emitting layer 37 are sequentially formed on the insulating film 32, and then the electron transport layer 38, the electron injection layer 39, The negative electrode 131 is formed.

At this time, the hole injection layer / hole transport layer, the light emitting layer, the electron transport layer / injection layer, and the negative electrode, which constitute the organic EL device of the present invention, are formed using a common one.

In the present invention, when the thin insulating film is formed on the surface of the positive electrode using the parylene-based compound as described above, since the positive electrode has a uniform surface, the work function of the positive electrode can be lowered. The current density of the EL element can be made uniform.

If the current density is uniformly formed as described above, since the current density is prevented from being locally increased, heat generation can be prevented from increasing. That is, when the heat generation of the organic EL device is large, the mobility of the electrode material is increased, but as the present invention uniformly reduces the heat generation by uniformizing the surface of the positive electrode, thus preventing the movement of the electrode material, thereby preventing a short circuit between the positive electrode and the negative electrode. The efficiency at the time of light emission can be improved by preventing the metal from moving to the light emitting layer.

As described above, the present invention improves the uniformity of the surface of the positive electrode, thereby increasing the electron injection effect, and uniformizing the current density to prevent the movement of the electrode material between the positive electrode and the negative electrode, thereby preventing short circuit of the organic EL element. The efficiency at the time of light emission can be improved by preventing the metal from moving to the light emitting layer.

BRIEF DESCRIPTION OF THE DRAWINGS The figure which shows the surface after formation of the positive electrode of the conventional organic electroluminescent element.

Fig. 2 is a view showing the surface after formation of the positive electrode on which the insulating film of the organic EL device of the present invention is formed.

3 is a schematic view for explaining the basic configuration of an organic EL device of the present invention.

<Brief description of the main parts of the drawing>

10, 20, 30: substrate 11, 21, 31: positive electrode

32, 23 insulating film 33: hole injection layer

35 hole transport layer 37 organic light emitting layer

38: electron injection layer 39: electron transport layer

131: negative electrode

Claims (4)

An organic EL device in which a positive electrode, an insulating film for planarizing a positive electrode surface, an organic light emitting layer, and a negative electrode are sequentially formed on a transparent substrate. The method of claim 1, The insulating film is an organic EL device, characterized in that formed using a parylene-based compound. The method of claim 2, The parylene-based compound is poly (2-chloro-1,4-dimethyl benzene) (poly (2-chloro-1,4-dimethyl benzene)), poly) 1,4-dichloro-2,5-dimethylbenzene) ( poly (1,4-dichloro-2,5-dimethylbenzene)), poly (2-fluoro-1,4-dimethylbenzene) (poly (2-fluoro-1,4-dimethylbenzene) and poly (para-xylene An organic EL device using one compound selected from the group consisting of (poly (para-xylene)). The method of claim 1, And the insulating film is formed at a thickness of 1 to 50 GPa.