Search

US-12622134-B2 - Organic electroluminescent device, and electronic apparatus

US12622134B2US 12622134 B2US12622134 B2US 12622134B2US-12622134-B2

Abstract

An object of the present invention is to provide a compound with a high refractive index and a low extinction coefficient at a wavelength in range of 450 nm to 750 nm in a capping layer to improve light extraction efficiency of an organic electroluminescent device. The present invention was achieved by focusing on the fact that a specific arylamine based compound has excellent thin film stability and durability and is able improve the refractive index by adjusting the molecular structures, and planning molecule, and an organic electroluminescent device having excellent luminous efficiency was obtained by using this compound as a material for constituting a capping layer.

Inventors

  • Takeshi Yamamoto
  • Kouki Kase
  • Eriko Chiba
  • Yuta HIRAYAMA
  • Shuichi Hayashi

Assignees

  • HODOGAYA CHEMICAL CO., LTD.

Dates

Publication Date
20260505
Application Date
20220309
Priority Date
20210312

Claims (20)

  1. 1 . An organic electroluminescent device in this order including at least an anode electrode, a hole transport layer, a light emitting layer, an electron transport layer, a cathode electrode, and a capping layer, and the organic electroluminescent device containing an amine compound as a material of the capping layer represented by the following general formula (1): wherein Ar 1 and Ar 2 may be the same or different, each has a structure represent by the following general formula (A), and represents a monovalent group having a bonding site at any one of R 5 and R 6 , Ar 3 has a structure represented by the following general formula (A), and represents a monovalent group having a bonding site at any one of R 5 and R 6 , a substituted or unsubstituted aromatic hydrocarbon group or a substituted or unsubstituted aromatic heterocyclic group, L 1 and L 2 may be the same or different, each represents a divalent group of a substituted or unsubstituted aromatic hydrocarbon group of 6 to 18 ring-forming carbon atoms, or a divalent group of a substituted or unsubstituted aromatic heterocyclic group of 6 to 18 ring-forming carbon atoms, L 3 represents a divalent group of a substituted or unsubstituted aromatic hydrocarbon group of 6 to 18 ring-forming carbon atoms, a divalent group of a substituted or unsubstituted aromatic heterocyclic group of 6 to 18 ring-forming carbon atoms, or a single bond, wherein X represents an oxygen atom, or a sulfur atom, R 1 to R 4 may be the same or different, each represents a hydrogen atom, a deuterium atom, a fluorine atom, a chlorine atom, a cyano group, a nitro group, a linear or branched alkyl group of 1 to 6 carbon atoms that may have a substituent, a cycloalkyl group of 5 to 10 carbon atoms that may have a substituent, a linear or branched alkenyl group of 2 to 6 carbon atoms that may have a substituent, a linear or branched alkyloxy group of 1 to 6 carbon atoms that may have a substituent, a cycloalkyloxy group of 5 to 10 carbon atoms that may have a substituent, a substituted or unsubstituted aromatic hydrocarbon group, a substituted or unsubstituted aromatic heterocyclic group, or a substituted or unsubstituted aryloxy group, R 1 to R 4 bonded to the same benzene ring may bind to each other via a single bond, a substituted or unsubstituted methylene group, an oxygen atom, or a sulfur atom to form a ring, One of R 5 and R 6 represents a linking group as a bonding site, a hydrogen atom, a deuterium atom, a fluorine atom, a chlorine atom, a cyano group, a nitro group, a linear or branched alkyl group of 1 to 6 carbon atoms that may have a substituent, a cycloalkyl group of 5 to 10 carbon atoms that may have a substituent, a linear or branched alkenyl group of 2 to 6 carbon atoms that may have a substituent, a linear or branched alkyloxy group of 1 to 6 carbon atoms that may have a substituent, a cycloalkyloxy group of 5 to 10 carbon atoms that may have a substituent, a substituted or unsubstituted aromatic hydrocarbon group, or a substituted or unsubstituted aromatic heterocyclic group.
  2. 2 . The organic electroluminescent device according to claim 1 , wherein the general formula (A) has a structure represented by the following general formula (A-1): wherein the dashed part is the binding site, X, R 1 to R 4 , and R 6 are the same as defined by the general formula (A).
  3. 3 . The organic electroluminescent device according to claim 1 , wherein the general formula (A) has a structure represented by the following general formula (A-2): wherein the dashed part is the binding site, X, and R 1 to R 5 R 6 are the same as defined by the general formula (A).
  4. 4 . The organic electroluminescent device according to claim 1 , wherein L 1 and L 2 in the general formula (1) are divalent groups that result from the removal of two hydrogen atoms from unsubstituted benzene, divalent groups that result from the removal of two hydrogen atoms from unsubstituted naphthalene, or divalent groups that result from the removal of two hydrogen atoms from unsubstituted biphenyl.
  5. 5 . The organic electroluminescent device according to claim 1 , wherein the amine compound represented by the general formula (1) is represented by the following general formula (1-a): wherein X, Ar 3 , L 3 , R 1 to R 4 , and R 6 are the same as defined by the general formula (1) and the general formula (A).
  6. 6 . The organic electroluminescent device according to claim 1 , wherein the amine compound represented by the general formula (1) is represented by the following general formula (1-b), wherein X, Ar 3 , L 3 , and R 1 to R 5 are the same as defined by the general formula (1) and the general formula (A).
  7. 7 . The organic electroluminescent device according to claim 1 , wherein the thickness of the capping layer is within a range of 30 nm to 120 nm.
  8. 8 . The organic electroluminescent device according to claim 1 , wherein the refractive index of the capping layer is 1.85 or more within a wavelength range of 450 nm or more and 750 nm or less.
  9. 9 . An electronic apparatus comprising the organic electroluminescent device according to claim 1 .
  10. 10 . The organic electroluminescent device according to claim 2 , wherein the thickness of the capping layer is within a range of 30 nm to 120 nm.
  11. 11 . The organic electroluminescent device according to claim 3 , wherein the thickness of the capping layer is within a range of 30 nm to 120 nm.
  12. 12 . The organic electroluminescent device according to claim 4 , wherein the thickness of the capping layer is within a range of 30 nm to 120 nm.
  13. 13 . The organic electroluminescent device according to claim 5 , wherein the thickness of the capping layer is within a range of 30 nm to 120 nm.
  14. 14 . The organic electroluminescent device according to claim 2 , wherein the refractive index of the capping layer is 1.85 or more within a wavelength range of 450 nm or more and 750 nm or less.
  15. 15 . The organic electroluminescent device according to claim 3 , wherein the refractive index of the capping layer is 1.85 or more within a wavelength range of 450 nm or more and 750 nm or less.
  16. 16 . The organic electroluminescent device according to claim 4 , wherein the refractive index of the capping layer is 1.85 or more within a wavelength range of 450 nm or more and 750 nm or less.
  17. 17 . The organic electroluminescent device according to claim 5 , wherein the refractive index of the capping layer is 1.85 or more within a wavelength range of 450 nm or more and 750 nm or less.
  18. 18 . An electronic apparatus comprising the organic electroluminescent device according to claim 2 .
  19. 19 . An electronic apparatus comprising the organic electroluminescent device according to claim 3 .
  20. 20 . An electronic apparatus comprising the organic electroluminescent device according to claim 4 .

Description

TECHNICAL FIELD The present invention relates to compounds and devices suitable for a preferred self-luminous electron device for various display devices, particularly an organic electroluminescent device (hereinafter referred to as organic EL device), which is and more specifically relates to an amine compound having a benzofuran structure or a benzothiophene structure and an organic EL device using the amine compound or an electronic apparatus. BACKGROUND ART In 1987, C. W. Tang and colleagues at Eastman Kodak developed a laminated structure device using materials assigned with different roles, realizing practical applications of an organic EL device with organic materials. These researchers laminated an electron-transporting phosphor and a hole-transporting organic substance and injected both charges into a phosphor layer to cause emission to obtain a high luminance of 1,000 cd/m 2 or more at a voltage of 10 V or less (see PTLs 1 and 2). To date, many improvements have been made for the practical application of organic EL devices. Various roles of the laminated structure have been further subdivided to provide a light emitting device that includes an anode, a hole injection layer, a hole transport layer, a light emitting layer, an electron transport layer, an electron injection layer, and a cathode sequentially on a substrate. In this light emitting device, high efficiency and durability have come to be achieved by providing thereto a bottom emission structure that emits light from the bottom (see, for example, NPL 1). Recently, a light emitting device with a top emission structure in which a metal having a high work function is used for an anode and light is emitted from the top is coming into use. In a light emitting device with a bottom-emission structure where light is taken out from the bottom having a pixel circuit, the area of the light emitting portion is limited, whereas in a light emitting device with a top-emission structure has the advantage that the light is taken out from the top and is not blocked by the pixel circuit, thus allowing a larger emission area. In the light emitting device with a top emission structure, translucent electrodes made of LiF/Al/Ag (see, for example, NPL 2), Ca/Mg (see, for example, NPL 3), LiF/MgAg, or the like are used for a cathode. In such light emitting device, when light emitted by a light emitting layer enters another layer at a certain angle or more, the light is totally reflected at an interface between the light emitting layer and the other layer. Thus, light that can be used has been limited to only a part of the emitted light. Recently, a light emitting device has been proposed in which a “capping layer” with a high refractive index is provided on the outside of a translucent electrode with a low refractive index, in order to improve the light extraction efficiency (see, for example, NPLs 2 and 3). Regarding the effect of the capping layer in a light emitting device with a top emission structure, while a light emitting device using Ir(ppy)3 as a light emitting material has a current efficiency of 38 cd/A in the case of not having a capping layer, the light emitting device has a current efficiency of 64 cd/A, in the case of using a ZnSe film with a thickness of 60 nm as a capping layer, which indicates that the efficiency is improved about 1.7 times. Furthermore, it is indicated that the maximum point of transmittance of the translucent electrode and capping layer does not necessarily coincide with the maximum point of efficiency, and that the maximum point of light extraction efficiency is determined by interference effects (see, for example, NPL 3). In the past, it has been proposed to use a metal mask with a high degree of definition to form the capping layer, but there is a problem that the metal mask is distorted by heat when used under high temperature conditions, resulting in a decrease in alignment accuracy. Therefore, ZnSe has a high melting point of 1100° C. or higher (see, for example, NPL 3), and a high definition metal mask cannot be used to deposit ZnSe at precise positions, which may affect the light emitting devices themselves. Furthermore, even deposition by the sputtering method affects the light emitting devices, inorganic materials are not suitable for use as components of the capping layer. In addition, when tris(8-hydroxyquinoline)aluminum (hereinafter referred to as Alq3) is used as a capping layer to adjust the refractive index (see, for example, NPL 2), Alq3 is known as an organic EL material commonly used as a green emitting material or electron transport material, it has a weak absorption around 450 nm, which is used for blue emitting materials, and has the problems of reducing the color purity and light extraction efficiency of blue emitting devices. Amine compounds introduced benzothiophene which is used for an organic EL device are disclosed, and these compounds are mainly used as hole transport layers (see, for example, NPLs