CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a national phase entry under 35 U.S.C. § 371 of International Application No. PCT/KR2019/000841 filed Jan. 21, 2019, which claims priority from Korean Patent Application No. 10-2018-0008801 filed Jan. 24, 2018, all of which are incorporated herein by reference.

TECHNICAL FIELD

The present specification relates to a polymer, a coating composition including the polymer, and an organic light emitting device formed using the same.

This application claims priority to and the benefits of Korean Patent Application No. 10-2018-0008801, filed with the Korean Intellectual Property Office on Jan. 24, 2018, the entire contents of which are incorporated herein by reference.

BACKGROUND ART

An organic light emission phenomenon is one of examples converting a current to visible light by an internal process of specific organic molecules. A principle of an organic light emission phenomenon is as follows. When an organic material layer is placed between an anode and a cathode and a current is applied between the two electrodes, electrons and holes are injected to the organic material layer from the cathode and the anode, respectively. The holes and the electrons injected to the organic material layer recombine to form excitons, and light emits when these excitons fall back to the ground state. An organic light emitting device using such a principle may be generally formed with a cathode, an anode, and an organic material layer placed therebetween, for example, an organic material layer including a hole injection layer, a hole transfer layer, a light emitting layer and an electron transfer layer.

Materials used in an organic light emitting device are mostly pure organic materials or complex compounds in which organic materials and metals form complexes, and may be divided into hole injection materials, hole transfer materials, light emitting materials, electron transfer materials, electron injection materials and the like depending on the application. Herein, as the hole injection material or the hole transfer material, organic materials having a p-type property, that is, organic materials readily oxidized and having an electrochemically stable state when oxidized, are generally used. Meanwhile, as the electron injection material or the electron transfer material, organic materials having an n-type property, that is, organic materials readily reduced and having an electrochemically stable state when reduced, are generally used. As the light emitting layer material, materials having both a p-type property and an n-type property, that is, materials having a stable form in both oxidized and reduced states, are preferred, and materials having high light emission efficiency converting, when excitons are formed, the excitons to light are preferred.

In addition to the properties described above, it is preferred that materials used in an organic light emitting device additionally have properties as follows.

First, materials used in an organic light emitting device preferably have excellent thermal stability. This is due to joule heat produced by charge migration in the organic light emitting device. N,N′-di(1-naphthyl)-N,N′-diphenyl-(1,1′-biphenyl)-4,4′-diamine (NPB) normally used as a hole transfer layer material currently has a glass transition temperature of 100° C. or lower, and has a problem in that it is difficult to use in organic light emitting devices requiring a high current.

Second, in order to obtain a highly efficient organic light emitting device capable of low voltage driving, holes or electrons injected into the organic light emitting device need to be smoothly transferred to a light emitting layer, and at the same time, the injected holes and electrons need to be kept from escaping out of the light emitting layer. For this, materials used in the organic light emitting device need to have a proper band gap and a highest occupied molecular orbital (HOMO) or lowest unoccupied molecular orbital (LUMO) energy level. Poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) currently used as a hole transfer material in an organic light emitting device manufactured using a solution coating method has a lower LUMO energy level compared to a LUMO energy level of organic materials used as a light emitting layer material, and therefore, has a problem in manufacturing an organic light emitting device with high efficiency and long lifetime.

In addition thereto, materials used in an organic light emitting device need to have excellent chemical stability, charge mobility, and interface property with electrodes or adjacent layers. In other words, materials used in an organic light emitting device need to undergo less material deformation caused by moisture or oxygen. In addition, by having proper hole or electron mobility, the materials need to maximize exciton formation through balancing hole and electron density in a light emitting layer of the organic light emitting device. For device stability, the materials also need to improve an interface with electrodes including metals or metal oxides.

In addition to the properties described above, materials used in an organic light emitting device for a solution process additionally need to have properties as follows.

First, a storable homogeneous solution needs to be formed. Commercialized materials for a deposition process have favorable crystallinity, and are not well-dissolved in a solution, or crystals are readily caught when forming a solution. Therefore, a concentration gradient of the solution may change depending on the storage time or possibility of forming a defective device is high.

Second, layers going through a solution process need to have solvent and material tolerance for other layers. For this, materials capable of forming a self-crosslinked polymer on a substrate through heat treatment or ultraviolet (UV) irradiation after introducing a curing group and solution coating such as N4,N4′-di(naphthalen-1-yl)-N4,N4′-bis(4-vinylphenyl)biphenyl-4,4′-diamine (VNPB) or forming a polymer having sufficient tolerance for a next process are preferred, and materials capable of having solvent tolerance by itself such as hexaazatriphenylene hexacarbonitrile (HATCN) are also preferred. Arylamine-based monomers generally used in an organic light emitting device (OLED) do not have tolerance for a solvent of a next process by themselves, and therefore, arylamine-based monomer compounds usable in an OLED device for a solution process need to have a curing group introduced thereto.

Accordingly, development of organic materials fulfilling such requirements has been required in the art.

DISCLOSURE

Technical Problem

The present specification is directed to providing a polymer usable in an organic light emitting device for a solution process, a coating composition including the same, and an organic light emitting device formed using the same.

Technical Solution

One embodiment of the present specification provides a polymer including a unit represented by the following Chemical Formula 1; and a unit represented by the following Chemical Formula 2.



In Chemical Formulae 1 and 2,

Ar1 to Ar5 are the same as or different from each other, and each independently a substituted or unsubstituted aryl group,

Ar2 and Ar3 may bond to each other to form a substituted or unsubstituted heteroring,

Ar4 and Ar5 may bond to each other to form a substituted or unsubstituted heteroring,

L1 and L2 are the same as or different from each other, and each independently a direct bond; or a substituted or unsubstituted arylene group,

Y is —Y1- or —(Y2)i-Y3-, and Y1 and Y3 are the same as or different from each other, and each independently a substituted or unsubstituted arylene group; or a substituted or unsubstituted alkylene group,

Y2 is a substituted or unsubstituted arylene group; a substituted or unsubstituted alkylene group; or —O—,

i is an integer of 1 to 8, and when i is 2 or greater, Y2s are the same as or different from each other,

Y2 bonding to Y3 is different from Y3, and when there are two or more Y2s, adjacent Y2s are different from each other,

R1 to R8 are the same as or different from each other, and each independently hydrogen, or a substituted or unsubstituted alkyl group,

L3 is a direct bond; a substituted or unsubstituted arylene group; a substituted or unsubstituted alkylene group; a substituted or unsubstituted alkyleneoxy group; or a substituted or unsubstituted divalent arylamine group,

l and k are each an integer of 0 to 3, and when 1 is 2 or greater, R1s are the same as or different from each other, and when k is 2 or greater, R2s are the same as or different from each other,

j is an integer of 1 to 3, and when j is 2 or greater, L3s are the same as or different from each other,

X is a curing group,

n and m mean a molar ratio in the polymer, and

0<n<1, 0<m<1, and m+n≤1.

Another embodiment of the present specification provides a coating composition including the polymer described above.

Still another embodiment of the present specification provides an organic light emitting device including a first electrode; a second electrode provided opposite to the first electrode; and one or more organic material layers provided between the first electrode and the second electrode, wherein one or more layers of the organic material layers include a cured material of the coating composition described above.

Advantageous Effects

A polymer according to one embodiment of the present specification includes a functional group polymerized by heat or light, and when providing sufficient heat or light after forming a film, tolerance for a solvent for a process is developed, and the compound according to one embodiment of the present specification is not washed away or film properties are not changed, and a reproducible organic light emitting device can be manufactured.

An aryl group (Ar1) directly attached to number 9 carbon of fluorene and a proper spacer between a curing group and the fluorene are capable of controlling a glass transition temperature, a melting point and solubility by inhibiting interactions between molecules, and therefore, this derivative can be used as a material of an organic material layer of an organic light emitting device, and is capable of providing low driving voltage, high light emission efficiency and long lifetime properties. In addition, by using the fluorene derivative, solubility increases leading to advantages of widening a range of solvent selection when manufacturing an ink of a solution process, and lowering a melting point and a curing temperature.

