Classifications

• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09D—COATING COMPOSITIONS, e.g. PAINTS, VARNISHES OR LACQUERS; FILLING PASTES; CHEMICAL PAINT OR INK REMOVERS; INKS; CORRECTING FLUIDS; WOODSTAINS; PASTES OR SOLIDS FOR COLOURING OR PRINTING; USE OF MATERIALS THEREFOR
  • C09D11/00—Inks
  • C09D11/02—Printing inks
  • C09D11/03—Printing inks characterised by features other than the chemical nature of the binder
  • C09D11/037—Printing inks characterised by features other than the chemical nature of the binder characterised by the pigment
• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09D—COATING COMPOSITIONS, e.g. PAINTS, VARNISHES OR LACQUERS; FILLING PASTES; CHEMICAL PAINT OR INK REMOVERS; INKS; CORRECTING FLUIDS; WOODSTAINS; PASTES OR SOLIDS FOR COLOURING OR PRINTING; USE OF MATERIALS THEREFOR
  • C09D11/00—Inks
  • C09D11/02—Printing inks
  • C09D11/03—Printing inks characterised by features other than the chemical nature of the binder
  • C09D11/033—Printing inks characterised by features other than the chemical nature of the binder characterised by the solvent
• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09D—COATING COMPOSITIONS, e.g. PAINTS, VARNISHES OR LACQUERS; FILLING PASTES; CHEMICAL PAINT OR INK REMOVERS; INKS; CORRECTING FLUIDS; WOODSTAINS; PASTES OR SOLIDS FOR COLOURING OR PRINTING; USE OF MATERIALS THEREFOR
  • C09D11/00—Inks
  • C09D11/30—Inkjet printing inks
  • C09D11/32—Inkjet printing inks characterised by colouring agents
  • C09D11/322—Pigment inks
• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09D—COATING COMPOSITIONS, e.g. PAINTS, VARNISHES OR LACQUERS; FILLING PASTES; CHEMICAL PAINT OR INK REMOVERS; INKS; CORRECTING FLUIDS; WOODSTAINS; PASTES OR SOLIDS FOR COLOURING OR PRINTING; USE OF MATERIALS THEREFOR
  • C09D11/00—Inks
  • C09D11/30—Inkjet printing inks
  • C09D11/36—Inkjet printing inks based on non-aqueous solvents
• • H—ELECTRICITY
  • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
  • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
  • H05B33/00—Electroluminescent light sources
  • H05B33/12—Light sources with substantially two-dimensional [2D] radiating surfaces
  • H05B33/14—Light sources with substantially two-dimensional [2D] radiating surfaces characterised by the chemical or physical composition or the arrangement of the electroluminescent material, or by the simultaneous addition of the electroluminescent material in or onto the light source
• • H—ELECTRICITY
  • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
  • H10K—ORGANIC ELECTRIC SOLID-STATE DEVICES
  • H10K50/00—Organic light-emitting devices
  • H10K50/10—OLEDs or polymer light-emitting diodes [PLED]
• • H—ELECTRICITY
  • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
  • H10K—ORGANIC ELECTRIC SOLID-STATE DEVICES
  • H10K50/00—Organic light-emitting devices
  • H10K50/10—OLEDs or polymer light-emitting diodes [PLED]
  • H10K50/11—OLEDs or polymer light-emitting diodes [PLED] characterised by the electroluminescent [EL] layers
  • H10K50/115—OLEDs or polymer light-emitting diodes [PLED] characterised by the electroluminescent [EL] layers comprising active inorganic nanostructures, e.g. luminescent quantum dots
• • H—ELECTRICITY
  • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
  • H10K—ORGANIC ELECTRIC SOLID-STATE DEVICES
  • H10K50/00—Organic light-emitting devices
  • H10K50/10—OLEDs or polymer light-emitting diodes [PLED]
  • H10K50/14—Carrier transporting layers
  • H10K50/16—Electron transporting layers
• • H—ELECTRICITY
  • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
  • H10K—ORGANIC ELECTRIC SOLID-STATE DEVICES
  • H10K71/00—Manufacture or treatment specially adapted for the organic devices covered by this subclass
  • H10K71/10—Deposition of organic active material
  • H10K71/12—Deposition of organic active material using liquid deposition, e.g. spin coating
• • H—ELECTRICITY
  • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
  • H10K—ORGANIC ELECTRIC SOLID-STATE DEVICES
  • H10K71/00—Manufacture or treatment specially adapted for the organic devices covered by this subclass
  • H10K71/10—Deposition of organic active material
  • H10K71/12—Deposition of organic active material using liquid deposition, e.g. spin coating
  • H10K71/13—Deposition of organic active material using liquid deposition, e.g. spin coating using printing techniques, e.g. ink-jet printing or screen printing
  • H10K71/135—Deposition of organic active material using liquid deposition, e.g. spin coating using printing techniques, e.g. ink-jet printing or screen printing using ink-jet printing

Definitions

• the present invention relates to a charge transport ink composition.
• OLED Organic electroluminescence
• advantages such as high contrast, energy saving, and flexibility, and are being put to practical use in fields such as displays and lighting.
• OLED elements use multiple functional thin films, one of which is the electron transport layer, which is responsible for the exchange of charges between the cathode and the light-emitting layer and plays an important role in achieving low-voltage operation and high brightness of OLED elements.
• the methods for manufacturing organic EL elements are broadly divided into dry processes, such as deposition methods, and wet processes, such as spin coating and inkjet methods.
• dry processes such as deposition methods
• wet processes such as spin coating and inkjet methods.
• quantum dot EL elements which use quantum dot materials as their light-emitting layer, have appeared and show the prospect of a wide range of applications.
• These quantum dot EL elements can be manufactured at low cost using wet processes, and due to their characteristics such as control of emission wavelength, high color purity, high luminous efficiency, and flexibility, they are attracting a lot of attention in fields such as display technology and lighting.
• Patent Documents 1 to 3 In such EL elements, it is necessary to laminate an electron transport layer containing metal oxide nanoparticles between the light-emitting layer and the cathode in order to efficiently inject electrons into the light-emitting layer, and to date, research has been conducted into the type and primary particle size of metal oxide nanoparticles in order to increase this efficiency (Patent Documents 1 to 3).
• metal oxide nanoparticles such as ZnO and SnO2 , which are commonly used in organic EL elements and quantum dot EL elements, have a small particle diameter (primary particle diameter: about several nm to several tens of nm), and therefore have a large specific surface area. Due to the resulting large surface energy, metal oxide nanoparticles are very unstable and prone to aggregation. When metal oxide nanoparticles aggregate, it affects the film-forming properties and the conductivity of the resulting thin film (Patent Document 4). When a functional layer such as an electron transport layer is formed by applying an ink in which metal oxide nanoparticles are aggregated, stable film formation cannot be performed, and the film becomes non-uniform and has poor flatness.
• Methods of suppressing the aggregation of metal oxide nanoparticles include surface treatment of the metal oxide nanoparticles (Patent Document 5) and addition of a binder (Patent Document 6), but further improvements are desired to improve the performance of the resulting EL elements.
• the present invention has been made in consideration of the above background, and aims to provide a charge transport ink composition that improves the dispersibility of metal oxide nanoparticles in organic solvents, and provides a film with excellent flatness while having charge transport properties.
• the present inventors have found that in a charge transporting ink composition containing metal oxide nanoparticles and an organic solvent, by using metal oxide-coated SnO2 nanoparticles in which SnO2 nanoparticles serve as nuclei and the surfaces of the nanoparticles are coated with a metal oxide as the metal oxide nanoparticles, the metal oxide-coated SnO2 nanoparticles are less likely to aggregate and have excellent dispersibility in an organic solvent, and have also found that a charge transporting thin film obtained from the charge transporting ink composition has practical conductivity and excellent flatness, thereby completing the present invention.
• An electronic device comprising the charge transport thin film of 7.
• the electronic device of 8, wherein the charge transporting thin film is an electron transporting layer.
• the electronic device of 9, wherein the electronic device is an organic EL device or a quantum dot EL device.
• a method for producing a charge-transporting thin film comprising applying the charge-transporting ink composition according to any one of 1 to 6 onto a substrate, and evaporating the solvent.
• charge transport ink composition of the present invention By using the charge transport ink composition of the present invention, a charge transport thin film with excellent flatness can be obtained.
• This charge transport thin film can be suitably used as a thin film for electronic devices, including organic EL devices and quantum dot EL devices.
• the charge transport ink composition of the present invention contains metal oxide-coated SnO2 nanoparticles, the surfaces of which are coated with metal oxide using SnO2 nanoparticles as nuclei, and an organic solvent.
• the "solid content" of the charge transport ink composition of the present invention means components other than the solvent contained in the composition.
• the charge transport property of the present invention is synonymous with electrical conductivity and electron transport property.
• the charge transport ink composition of the present invention may have charge transport property by itself, or may have charge transport property in a solid film obtained by using the composition.
• the reason why the SnO 2 nanoparticles used as the nuclei have electrical conductivity and can inject charges is considered to be as follows.
• Metal oxides are dielectrics themselves, but in the process of synthesizing nanoparticles, defect levels such as metal deficiency and oxygen deficiency may occur, resulting in an incomplete oxide state. In terms of electronic materials, metal oxides with an incomplete oxidation state produce excess holes and excess electrons, and are considered to be the cause of p-type and n-type semiconductors. It is known that SnO2 nanoparticles exhibit conductivity due to oxygen deficiency, and are also known to exhibit conductivity when doped with indium or antimony. When such SnO2 nanoparticles are made into a film, a layer containing a large amount of internal charge is formed. Then, by applying an electric field to this layer, the internal charge moves to the counter electrode and becomes a current.
• a charge transfer complex is formed at the interface. More specifically, a charge transfer complex (metal complex) is formed between the oxide on the SnO2 nanoparticles and the electrode, or between the metal on the SnO2 nanoparticles and the quantum dots. Therefore, it is believed that charge is injected into the light-emitting layer through this charge transfer complex, and charge injection occurs even if there is a band gap between the electrode and the SnO2 nanoparticles, or between the SnO2 nanoparticles and the quantum dots.
• metal complex metal complex
• the charge transport ink composition of the present invention contains metal oxide-coated SnO2 nanoparticles, which are SnO2 nanoparticles as cores and have their surfaces coated with metal oxide.
• Nanoparticles refer to fine particles whose primary particle average particle size is on the order of nanometers (typically 500 nm or less). The particle size can be measured by a method such as a transmission electron microscope method or a dynamic light scattering method (DLS).
• the primary particle diameter of the core SnO2 nanoparticles is not particularly limited as long as it is nano-sized. However, in order to obtain a thin film with good reproducibility and excellent flatness, the primary particle diameter is preferably 1 to 50 nm, and more preferably 2 to 30 nm.
• the metal oxide coating the surface of the SnO2 nanoparticles from the viewpoint of achieving both dispersibility in organic solvents and charge transport properties, at least one selected from the group consisting of In2O3 , Sb2O5 , SiO2 , SnO2 , TiO2 , WO3 , ZnO, ZrO2 and complexes of at least two of these is preferred, with Sb2O5 and SnO2 - SiO2 complexes being more preferred.
• the mass ratio of the SnO2 nanoparticles to the metal oxide is preferably 0.01 to 1.00, more preferably 0.03 to 0.30, from the viewpoint of achieving both dispersibility in an organic solvent and charge transportability.
• the above-mentioned metal oxide-coated SnO2 nanoparticles can be produced by coating the surface of colloidal SnO2 nanoparticles having a primary particle size within the above range with the desired metal oxide.
• the method for producing colloidal SnO2 nanoparticles and the method for coating the surface of the above-mentioned SnO2 nanoparticles with metal oxide can be referred to known methods. Examples of known methods include the methods described in Japanese Patent No. 4561955 and Japanese Patent No. 4730487.
• the metal oxide-coated SnO 2 nanoparticles are preferably hydrothermally treated metal oxide-coated SnO 2 nanoparticles that have been subjected to a hydrothermal treatment in the production process.
• examples of the hydrothermal treatment method include the following Method 1 and Method 2.
• Method 1 A method in which SnO2 nanoparticles before surface coating are subjected to hydrothermal treatment to obtain hydrothermally treated SnO2 nanoparticles, and a metal oxide is coated on the surface of the hydrothermally treated SnO2 nanoparticles.
• Method 2 A method in which the metal oxide-coated SnO2 nanoparticles obtained by coating the surface of SnO2 nanoparticles (not subjected to hydrothermal treatment) with a metal oxide are further subjected to hydrothermal treatment to obtain hydrothermally treated metal oxide-coated SnO2 nanoparticles.
• the temperature is preferably 100 to 350°C.
• the treatment time is preferably 0.1 to 50 hours.
• the metal oxide-coated SnO 2 nanoparticles contained in the charge transporting ink composition of the present invention may be of one type alone or two or more types.
• the metal oxide-coated SnO 2 nanoparticles contained in the charge transport ink composition of the present invention are preferably uniformly dispersed in the composition.
• the metal oxide-coated SnO2 nanoparticles may contain one or more organic capping groups.
• the organic capping groups may be reactive or non-reactive. Examples of reactive organic capping groups include organic capping groups that can be crosslinked by ultraviolet light or radical initiators.
• the primary particle diameter of the metal oxide-coated SnO2 nanoparticles is not particularly limited as long as it is nano-sized. However, in order to obtain a thin film having good reproducibility and excellent flatness, the primary particle diameter is preferably 2 to 60 nm, and more preferably 3 to 40 nm.
• the content of the metal oxide-coated SnO2 nanoparticles is not particularly limited, but from the viewpoint of suppressing particle aggregation in the charge transporting ink composition and obtaining a thin film with good reproducibility and excellent flatness, the content is preferably 10 to 100 mass %, more preferably 20 to 100 mass %, even more preferably 30 to 100 mass %, and most preferably 40 to 100 mass %.
• a composition in which the metal oxide-coated SnO2 nanoparticles are uniformly dispersed can be prepared with good reproducibility.
• a metal oxide-coated SnO 2 nanoparticle sol can be prepared by a known method using a solvent that may be contained in the charge transport ink composition of the present invention and the metal oxide-coated SnO 2 nanoparticles.
• metal oxide-coated SnO2 nanoparticle sol in which metal oxide-coated SnO2 nanoparticles are dispersed in a dispersion medium.
• the metal oxide-coated SnO2 nanoparticle sol is not particularly limited, and can be appropriately selected from known metal oxide-coated SnO2 nanoparticle sols.
• the metal oxide-coated SnO2 nanoparticle sol is usually in the form of a dispersion, which includes metal oxide-coated SnO2 nanoparticles dispersed in various solvents, such as alcohols, glycols, ketones, esters , ethers, amides, hydrocarbons, or mixtures thereof.
• solvents such as alcohols, glycols, ketones, esters , ethers, amides, hydrocarbons, or mixtures thereof.
• the alcohol include methanol, ethanol, n-propanol, i-propanol, n-butanol, 1-octanol, 1-nonanol, 1-decanol, tetrahydrofurfuryl alcohol, and terpineol.
• glycols examples include ethylene glycol, propylene glycol, 2-methyl-2,4-pentanediol, 1,3-octylene glycol, diethylene glycol, dipropylene glycol, triethylene glycol, tripropylene glycol, 1,3-butanediol, 2,3-butanediol, 1,4-butanediol, and 3-methyl-1,5-pentanediol.
• ketone examples include acetone, acetylacetone, methyl ethyl ketone, diethyl ketone, methyl n-propyl ketone, methyl n-butyl ketone, methyl isobutyl ketone, methyl n-amyl ketone, 4-hydroxy-4-methyl-2-pentanone, 2-heptanone, cyclohexanone, methylcyclopentanone, and isophorone.
• ester examples include dimethyl carbonate, diethyl carbonate, propylene carbonate, methyl formate, ethyl formate, propyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl acrylate, ethyl acrylate, propyl acrylate, dimethyl maleate, diethyl maleate, dipropyl maleate, dibutyl maleate, dimethyl adipate, diethyl adipate, dipropyl adipate, diisopropyl malonate, dimethyl sebacate, diethyl sebacate, and propylene glycol monomethyl ether acetate.
• ether examples include dimethyl ether, ethyl methyl ether, diethyl ether, tetrahydrofuran, 1,4-dioxane, ethylene glycol monopropyl ether, propylene glycol monomethyl ether, diethylene glycol monomethyl ether, diethylene glycol monobutyl ether, diethylene glycol mono-tert-butyl ether, triethylene glycol monomethyl ether, triethylene glycol monobutyl ether, tripropylene glycol monomethyl ether, and tripropylene glycol butyl ether.
• Examples of the amide include N,N-dimethylacetamide, N,N-dimethylformamide, N-methyl-2-pyrrolidone, N-ethylpyrrolidone, and 1,3-dimethyl-2-imidazolidinone.
• Examples of the hydrocarbon include n-hexane, n-heptane, n-octane, n-nonane, n-decane, i-octane, i-nonane, and i-decane.
• metal oxide-coated SnO2 nanoparticles in which the dispersion medium is an alcohol, glycol, ester or ether are preferred.
• the alcohol, glycol or ester methanol, ethanol, n-propanol, i-propanol, ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, tripropylene glycol, propylene carbonate, propylene glycol monomethyl ether acetate, diethylene glycol monobutyl ether, diethylene glycol mono-tert-butyl ether, tripropylene glycol monomethyl ether, and tripropylene glycol butyl ether are more preferred.
• the concentration of the metal oxide-coated SnO 2 nanoparticles in the ink composition is appropriately set taking into consideration the viscosity and surface tension of the ink composition, the thickness of the thin film to be produced, etc., but is usually about 0.1 to 30 mass %.
• concentration of the metal oxide-coated SnO 2 nanoparticles is high, the metal oxide-coated SnO 2 nanoparticles may aggregate depending on the type of solvent contained in the mixture, so this point should be taken into consideration when preparing the composition.
• the charge transporting ink composition of the present invention contains an organic solvent.
• organic solvent include alcohol solvents such as methanol, ethanol, n-propanol, i-propanol, n-butanol, 1-octanol, 1-nonanol, 1-decanol, tetrahydrofurfuryl alcohol, terpineol, cyclohexanol, diacetone alcohol, benzyl alcohol, 2-phenoxyethanol, and 2-benzyloxyethanol; ethylene glycol, propylene glycol, 2-methyl-2,4-pentanediol, 1,3-octylene glycol, diethylene glycol, diisopropyl alcohol, and the like.
• Glycol solvents such as propylene glycol, triethylene glycol, tripropylene glycol, 1,3-butanediol, 2,3-butanediol, 1,4-butanediol, and 3-methyl-1,5-pentanediol; acetone, acetylacetone, methyl ethyl ketone, diethyl ketone, methyl n-propyl ketone, methyl n-butyl ketone, methyl isobutyl ketone, methyl n-amyl ketone, 4-hydroxy-4-methyl-2-pentanone, 2-heptanone, cyclohexanone, methylcyclopentanone, iso Ketone solvents such as fluorine; dimethyl carbonate, diethyl carbonate, ethylene carbonate, propylene carbonate, methyl formate, ethyl formate, propyl formate, methyl acetate, ethyl acetate,
• alcohol-based solvents examples include butyl, ethanol, 1-octanol, 1-nonanol, 1-decanol, terpineol, ethylene glycol, 2-methyl-2,4-pentanediol, diethylene glycol, dipropylene glycol, triethylene glycol, tripropylene glycol, 3-methyl-1,5-pentanediol, propylene carbonate, dibutyl maleate, diethyl sebacate, diethylene glycol monomethyl ether, diethylene glycol monobutyl ether, diethylene glycol mono-tert-butyl ether, triethylene glycol monomethyl ether, triethylene glycol monobutyl ether, tripropylene glycol monomethyl ether and tripropylene glycol butyl ether are more preferred.
• These organic solvents may be used alone or in combination of two or more.
• a composition that will give a uniform film thickness is required.
• a composition containing only a low boiling point solvent may make it difficult to obtain a flat layer depending on the conditions of use.
• it is believed that the use of a high boiling point solvent can suppress the evaporation of the solvent and the rate of ink convection and viscosity increase, thereby obtaining a flat layer.
• the upper limit of the boiling point is not particularly limited, but is usually 330°C or lower.
• the content is not particularly limited, but it is preferable that the content is 20% by mass or more in the organic solvent.
• the charge transport ink composition of the present invention is best suited to use only organic solvents as the solvent.
• “only organic solvents” means that only organic solvents are used as the solvent, and does not exclude the presence of trace amounts of "water” contained in the organic solvent or solids used.
• the charge transporting ink composition of the present invention contains the above-mentioned metal oxide-coated SnO2 nanoparticles and an organic solvent.
• the ink composition may contain a binder resin, as described below, as necessary.
• the binder resin is not particularly limited as long as it disperses or dissolves in at least one solvent used in the charge transport ink composition, and a polymeric material can be used as the binder.
• a polymeric material can be used as the binder.
• materials that can be used include, but are not limited to, polystyrene, polyimide, polycarbonate, acrylic resin, and inactive resin.
• the binder resin may have charge transport properties, or a charge transport material may be mixed into the binder resin.
• the conductivity of the electron transport layer can be improved more than when the binder resin is insulating.
• the metal oxide-coated SnO 2 nanoparticles themselves have sufficient charge transport properties, when minute nanoparticles are uniformly and at a low concentration dispersed in the binder, the charge held by the nanoparticles may not be transported effectively. Therefore, by using a material having charge transport properties as a material constituting the electron transport layer other than the metal oxide-coated SnO 2 nanoparticles, the high charge transport properties of the metal oxide-coated SnO 2 nanoparticles can be more effectively brought out.
• the content is usually about 5 to 95% by mass of the solid content, but taking into consideration the balance between improving the flatness of the resulting thin film and preventing a decrease in charge transport properties, the content is preferably about 10 to 90% by mass, more preferably about 20 to 80% by mass, and even more preferably about 30 to 70% by mass.
• the charge transport ink composition of the present invention may contain an organic silane compound or a phosphate ester compound.
• an organic silane compound or a phosphate ester compound in the charge transport ink composition, when the charge transport thin film obtained from the ink composition is used as an electron transport layer of an organic EL device or a quantum dot EL device, the flatness of the obtained thin film can be improved, and the electron transport to the light-emitting layer provided in contact with the thin film can be improved.
• alkoxysilane is preferred, and trialkoxysilane and tetraalkoxysilane are more preferred.
• alkoxysilane include tetraethoxysilane, tetramethoxysilane, tetraisopropoxysilane, phenyltriethoxysilane, phenyltrimethoxysilane, methyltriethoxysilane, methyltrimethoxysilane, 3,3,3-trifluoropropyltrimethoxysilane, dimethyldiethoxysilane, and dimethyldimethoxysilane.
• tetraethoxysilane TEOS
• tetramethoxysilane tetramethoxysilane
• tetraisopropoxysilane tetraethoxysilane
• organic silane compounds can be used alone or in combination of two or more.
• these organic silane compounds can be used in combination with the phosphate ester compounds described below.
• the phosphate ester compound is preferably a compound represented by the following formulas (1) to (3), and more preferably a polyoxyethylene alkyl ether phosphate represented by the following formula (1).
• An example of the polyoxyethylene alkyl ether phosphate ester is a phosphate ester in which the terminal alkyl group (Y1) in the following formula (1) is an alkyl group having 6 to 15 carbon atoms.
• Examples of commercially available phosphate ester compounds include those manufactured by Toho Chemical Industry Co., Ltd., and sold under the trade names Phosphanol RA-600, RS-410, RS-610, and RS-710. These phosphate ester compounds can be used alone or in combination of two or more. These phosphate ester compounds can also be used in combination with an organic silane compound.
• X1 , X2 , and X3 each independently represent an alkylene group having 2 to 20 carbon atoms; f, h, and j each independently represent an integer from 1 to 100; e, g, and i each independently represent an integer from 1 to 3; and Y1 , Y2 , and Y3 each independently represent a hydrogen atom, an alkyl group having 1 to 20 carbon atoms, an alkenyl group having 2 to 20 carbon atoms, an aryl group having 6 to 30 carbon atoms, or a (meth)acrylic group.
• the alkylene group having 2 to 20 carbon atoms may be linear, branched, or cyclic, and specific examples include methylene, methylmethylene, dimethylmethylene, ethylene, 1,2-dimethylethylene, tetramethylethylene, trimethylene, propylene, tetramethylene, pentamethylene, hexamethylene, 1,2-cyclohexylene, 1,3-cyclohexylene, and 1,4-cyclohexylene.
• the alkyl group having 1 to 20 carbon atoms may be linear, branched, or cyclic, and specific examples include methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, s-butyl, t-butyl, n-pentyl, n-hexyl, n-heptyl, n-octyl, n-nonyl, n-decyl, n-undecyl, n-dodecyl, n-tridecyl, n-tetradecyl, n-pentadecyl, n-hexadecyl, n-hepta ...
• -C1-C20 linear or branched alkyl groups such as n-octadecyl, n-nonadecyl, and n-eicosanyl; and C3-C20 cyclic alkyl groups such as cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl, cyclooctyl, cyclononyl, cyclodecyl, bicyclobutyl, bicyclopentyl, bicyclohexyl, bicycloheptyl, bicyclooctyl, bicyclononyl, and bicyclodecyl.
• Alkenyl groups having 2 to 20 carbon atoms include ethenyl, n-1-propenyl, n-2-propenyl, 1-methylethenyl, n-1-butenyl, n-2-butenyl, n-3-butenyl, 2-methyl-1-propenyl, 2-methyl-2-propenyl, 1-ethylethenyl, 1-methyl-1-propenyl, 1-methyl-2-propenyl, n-1-pentenyl, n-1-decenyl, and n-1-eicosenyl.
• Aryl groups having 6 to 30 carbon atoms include phenyl, tolyl, 1-naphthyl, 2-naphthyl, 1-anthryl, 2-anthryl, 9-anthryl, 1-phenanthryl, 2-phenanthryl, 3-phenanthryl, 4-phenanthryl, 9-phenanthryl, biphenyl-2-yl, biphenyl-3-yl, and biphenyl-4-yl groups.
• the content is usually about 0.1 to 50 mass% of the solid content, but considering the balance between improving the flatness of the resulting thin film and suppressing the decrease in charge transportability, the content is preferably about 0.5 to 40 mass%, more preferably about 0.8 to 30 mass%, and even more preferably about 1 to 20 mass%.
• the viscosity of the charge transporting ink composition of the present invention is usually 1 to 50 mPa ⁇ s at 25° C., and the surface tension is usually 20 to 50 mN/m at 25° C.
• the viscosity and surface tension of the charge transporting ink composition of the present invention can be adjusted by changing the types of organic solvents used, their ratios, solids concentration, etc., taking into consideration various factors such as the dispersibility of the metal oxide-coated SnO 2 nanoparticles, the coating method used, and the desired film thickness.
• the solids concentration of the charge transporting ink composition of the present invention is appropriately set taking into consideration the viscosity and surface tension of the charge transporting ink composition and the thickness of the thin film to be produced, but is usually about 0.1 to 30% by mass. From the viewpoint of suppressing aggregation of the charge transporting substance and metal oxide-coated SnO nanoparticles in the ink composition, the solids concentration is preferably 20% by mass or less, more preferably 15% by mass or less, and even more preferably 10% by mass or less.
• the metal oxide-coated SnO2 nanoparticles and the organic solvent, and further, if necessary, the binder resin, the organic silane compound, the phosphate ester compound, etc. can be mixed in any order.
• the above-mentioned other components for example, a method of adding the other components or their solutions prepared in advance to the metal oxide-coated SnO2 nanoparticle sol dispersed in the solvent can be mentioned. The above-mentioned method can be adopted as long as the solid content is uniformly dissolved or dispersed in the solvent.
• the metal oxide-coated SnO2 nanoparticles may aggregate or precipitate when mixed, depending on the types and amounts of the components mixed together.
• heating may be performed appropriately within a range in which the components are not decomposed or altered.
• the charge transport ink composition may be filtered using a sub-micrometer filter during the production process of the charge transport ink composition or after all the components have been mixed, in order to reproducibly obtain a thin film with a higher flatness.
• the method for applying the ink composition is not particularly limited, and examples include dipping, spin coating, transfer printing, roll coating, brushing, inkjet, spraying, and slit coating. It is preferable to adjust the viscosity and surface tension of the ink composition depending on the application method.
• the baking atmosphere is not particularly limited, and a thin film having a uniform film surface and high charge transport properties can be obtained not only in the air but also in an inert gas such as nitrogen or in a vacuum.
• the baking temperature is appropriately set within a range of about 80 to 260°C, taking into consideration the use of the thin film obtained, the degree of charge transport properties to be imparted to the thin film obtained, the type and boiling point of the solvent, etc., but when the thin film obtained is used as an electron transport layer of an organic EL element or a quantum dot EL element, about 100 to 250°C is preferable.
• the temperature may be changed in two or more stages in order to achieve a more uniform film formation property or to promote a reaction on the substrate, and heating may be performed using an appropriate device such as a hot plate, oven, or vacuum oven.
• the thickness of the charge transporting thin film is not particularly limited, but when used as a functional layer provided between the cathode and the light emitting layer, such as the electron injection layer or electron transport layer of an organic EL element or quantum dot EL element, it is preferably 5 to 300 nm, and more preferably 20 to 200 nm.
• Methods for changing the film thickness include changing the solids concentration in the charge transporting ink composition and changing the amount of solution on the substrate during application.
• the organic EL element or quantum dot EL element of the present invention has a pair of electrodes and a charge transport layer made of the above-mentioned charge transport thin film of the present invention between the electrodes.
• Representative configurations of organic EL elements and quantum dot EL elements include, but are not limited to, the following (a) to (f).
• the charge transport ink composition of the present invention can be suitably used in elements having the configurations (a) to (d) among these.
• an electron blocking layer or the like can be provided between the light emitting layer and the anode, and a hole (positive hole) blocking layer or the like can be provided between the light emitting layer and the cathode, as necessary.
• the hole injection layer, the hole transport layer, or the hole injection transport layer may also function as an electron blocking layer, and the electron injection layer or the electron transport layer may also function as a hole (positive hole) blocking layer.
• an arbitrary functional layer can be provided between each layer as necessary.
• anode/hole injection layer/hole transport layer/light emitting layer/electron transport layer/electron injection layer/cathode (b) anode/hole injection layer/hole transport layer/light emitting layer/electron transport layer/cathode (c) anode/hole injection transport layer/light emitting layer/electron transport layer/electron injection layer/cathode (d) anode/hole injection transport layer/light emitting layer/electron transport layer/cathode (e) anode/hole injection layer/hole transport layer/light emitting layer/cathode (f) anode/hole injection transport layer/light emitting layer/cathode
• the "hole injection layer”, “hole transport layer” and “hole injection transport layer” are layers formed between the light-emitting layer and the anode, and have the function of transporting holes from the anode to the light-emitting layer.
• the hole injection transport layer When only one layer of a hole-transporting material is provided between the light-emitting layer and the anode, it is the “hole injection transport layer”.
• the layer closest to the anode is the “hole injection layer” and the other layers are “hole transport layers”.
• the hole injection (transport) layer is a thin film that is excellent not only in accepting holes from the anode, but also in injecting holes into the hole transport (light-emitting) layer.
• an “electron injection layer” and an “electron transport layer” are layers formed between a light-emitting layer and a cathode and have the function of transporting electrons from the cathode to the light-emitting layer. When only one layer of an electron transporting material is provided between the light-emitting layer and the cathode, it is the “electron transport layer”. When two or more layers of an electron transporting material are provided between the light-emitting layer and the cathode, the layer closest to the cathode is the “electron injection layer” and the other layers are “electron transport layers”.
• the "light-emitting layer” is a layer having a light-emitting function, and may be an organic light-emitting layer or a quantum dot light-emitting layer.
• the light-emitting layer is an organic light-emitting layer EL element, it is an organic EL element, and when the light-emitting layer is a quantum dot light-emitting layer EL element, it is a quantum dot EL element.
• the charge transporting thin film produced from the charge transporting ink composition of the present invention can be used as a functional layer formed between the cathode and the light emitting layer in an organic EL device or a quantum dot EL device, but is suitable as an electron injection layer or an electron transport layer, and is more suitable as an electron transport layer.
• the materials and production methods used include, but are not limited to, those listed below.
• An example of a method for producing an organic EL element or a quantum dot EL element having an electron transport layer made of a thin film obtained from the charge transport ink composition of the present invention is as follows. It is preferable to previously perform a surface treatment on the electrodes, such as cleaning with alcohol, pure water, or UV ozone treatment or oxygen plasma treatment, within a range that does not adversely affect the electrodes. A hole injection layer and a hole transport layer are sequentially laminated on an anode substrate by a wet process using a hole injection layer forming composition or a hole transport layer forming composition containing a hole transport polymer.
• a light emitting layer is laminated by a wet process using a light emitting layer forming composition containing a light emitting polymer or a quantum dot material.
• an electron transport layer is formed by a wet process using the charge transport ink composition of the present invention, and a cathode metal is vapor deposited thereon.
• these layers can also be formed by vapor deposition. If necessary, an electron blocking layer may be provided between the light emitting layer and the hole transport layer.
• an example (forward structure) in which an anode, a hole injection layer, a hole transport layer, a light emitting layer, an electron transport layer, and a cathode are laminated in this order has been described, but the present invention is not limited thereto, and a cathode, an electron transport layer, a light emitting layer, a hole transport layer, a hole injection layer, and an anode may be laminated in this order (reverse structure).
• anode material examples include transparent electrodes such as indium tin oxide (ITO) and indium zinc oxide (IZO), metal anodes such as aluminum, and metal anodes made of alloys thereof, and it is preferable to use those that have been subjected to a planarization treatment. Polythiophene derivatives and polyaniline derivatives having high charge transport properties can also be used. Other metals constituting the metal anode include, but are not limited to, gold, silver, copper, indium, and alloys thereof.
• Hole-transporting polymers include poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonic acid), poly[(9,9-dihexylfluorenyl-2,7-diyl)-co-(N,N'-bis ⁇ p-butylphenyl ⁇ -1,4-diaminophenylene)], poly[(9,9-dioctylfluorenyl-2,7-diyl)-co-(N,N'-bis ⁇ p-butylphenyl ⁇ -1,1'-biphenylene-4,4-diamine)], poly[(9,9-bis ⁇ 1'-pentene- 5'-yl ⁇ fluorenyl-2,7-diyl)-co-(N,N'-bis ⁇ p-butylphenyl ⁇ -1,4-diaminophenylene)], poly[N,N'-bis(4-butylphenyl)-N
• Light-emitting polymers include, but are not limited to, polyfluorene derivatives such as poly(9,9-dialkylfluorene) (PDAF), polyphenylenevinylene derivatives such as poly(p-phenylenevinylene) and poly[2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene] (MEH-PPV), polythiophene derivatives such as poly(3-alkylthiophene) (PAT), polyvinylcarbazole (PVCz), etc.
• polyfluorene derivatives such as poly(9,9-dialkylfluorene) (PDAF)
• polyphenylenevinylene derivatives such as poly(p-phenylenevinylene) and poly[2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene]
• MEH-PPV poly[2-methoxy-5-(2-ethylhexyloxy
• the quantum dot material may include at least one semiconductor material selected from the group consisting of II-VI group semiconductors, III-V group semiconductors, I-III-VI group semiconductors, IV group semiconductors, and I-II-IV-VI group semiconductors.
• Specific examples of the semiconductor material include CdS, CdSe, CdTe, ZnS, ZnSe, ZnTe, ZnO, HgS, HgSe, HgTe, CdSeS, CdSeTe, CdSTe, ZnSeS, ZnSeTe, ZnSTe, HgSeS, HgSeTe, HgSTe, CdZnS, CdZnSe, CdZnTe, CdHgS, CdHgSe, CdHgTe , HgZnS, HgZnSe, CdHgZnTe, CdZnSeS, CdZnSeTe, CdZnST
• Examples of materials for forming the hole injection layer include copper phthalocyanine, titanium oxide phthalocyanine, platinum phthalocyanine, pyrazino[2,3-f][1,10]phenanthroline-2,3-dicarbonitrile, N,N,N',N'-tetrakis(4-methoxyphenyl)benzidine, 2,7-bis[N,N-bis(4-methoxy-phenyl)amino]-9,9-spirobifluorene, 2,2'-bis[N,N-bis(4-methoxy-phenyl)amino]-9,9-spirobifluorene, N,N'-diphenyl-N,N'-di[4-(N,N-ditolylamino)phenyl]benzidine, N,N'-diphenyl-N,N'-di[4-(N,N-diphenylamino)phenyl]benzidine, N 4 ,N 4' -(
• Materials for forming the hole transport layer include, but are not limited to, triarylamines such as (triphenylamine) dimer derivatives, [(triphenylamine) dimer] spiro dimer, N,N'-bis(naphthalene-1-yl)-N,N'-bis(phenyl)-benzidine ( ⁇ -NPD), 4,4',4"-tris[3-methylphenyl(phenyl)amino]triphenylamine (m-MTDATA), 4,4',4"-tris[1-naphthyl(phenyl)amino]triphenylamine (1-TNATA), and oligothiophenes such as 5,5"-bis- ⁇ 4-[bis(4-methylphenyl)amino]phenyl ⁇ -2,2':5',2"-terthiophene (BMA-3T).
• triarylamines such as (triphenylamine) dimer derivatives, [(triphenylamine) dimer]
• Examples of materials for forming the light-emitting layer include, but are not limited to, low molecular weight light-emitting materials such as metal complexes such as aluminum complexes of 8-hydroxyquinoline, metal complexes of 10-hydroxybenzo[h]quinoline, bisstyrylbenzene derivatives, bisstyrylarylene derivatives, metal complexes of (2-hydroxyphenyl)benzothiazole, and silole derivatives; and systems in which a light-emitting material and an electron transfer material are mixed into a polymer compound such as poly(p-phenylenevinylene), poly[2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene], poly(3-alkylthiophene), or polyvinylcarbazole.
• low molecular weight light-emitting materials such as metal complexes such as aluminum complexes of 8-hydroxyquinoline, metal complexes of 10-hydroxybenzo[h]quinoline, bisst
• a light-emitting layer when forming a light-emitting layer by vapor deposition, it may be co-deposited with a light-emitting dopant.
• the light-emitting dopant include, but are not limited to, metal complexes such as tris(2-phenylpyridine)iridium(III) (Ir( ppy )), naphthacene derivatives such as rubrene, quinacridone derivatives, and condensed polycyclic aromatic rings such as perylene.
• Cathode materials include, but are not limited to, aluminum, magnesium-silver alloy, aluminum-lithium alloy, and the like.
• Examples of materials for forming the electron blocking layer include, but are not limited to, tris(phenylpyrazole)iridium.
• the materials constituting the anode, cathode and layers formed therebetween differ depending on whether an element having a bottom emission structure or a top emission structure is manufactured, and therefore, the materials are appropriately selected taking this into consideration.
• a transparent anode is used on the substrate side and light is extracted from the substrate side
• a reflective anode made of metal is used and light is extracted from the transparent electrode (cathode) side opposite the substrate.
• a transparent anode such as ITO
• a reflective anode such as an Ag alloy or Al alloy
• the organic EL element of the present invention may be sealed with a moisture scavenger or the like, if necessary, in accordance with standard procedures, to prevent deterioration of the characteristics.
• the charge transport ink composition of the present invention is preferably used for forming a functional layer formed between the cathode and light-emitting layer of an organic EL element or a quantum dot EL element, but it can also be used for forming a charge transport thin film in electronic elements such as organic photoelectric conversion elements, organic thin-film solar cells, organic perovskite photoelectric conversion elements, organic integrated circuits, organic field effect transistors, organic thin-film transistors, organic light-emitting transistors, organic optical inspection devices, organic photoreceptors, organic field quenching elements, light-emitting electrochemical cells, quantum lasers, organic laser diodes, and organic plasmon light-emitting elements. In particular, it can be preferably used in organic EL elements and quantum dot EL elements.
• the charge transport thin film formed on the substrate can be measured using a known micro-shape measuring instrument, for example, a Surfcorder ET-4000 manufactured by Kosaka Laboratory Co., Ltd.
• the average surface roughness Ra (nm) is usually 5.0 nm or less, in a preferred embodiment 3.0 nm or less, in a more preferred embodiment 2.0 nm or less, and in an even more preferred embodiment 1.0 nm or less.
• the obtained stannic oxide slurry was cooled to about 40°C, and then 2.7 kg of isopropylamine was added and peptized, after which the mixture was passed through a catalyst tower filled with about 15 L of platinum catalyst (N-220 (manufactured by Süd-Chemie Catalyst Co., Ltd.)) and circulated to decompose excess hydrogen peroxide.
• the liquid was passed through a column filled with an anion exchange resin at a flow rate of about 30 L/min. for 5 hours, and then concentrated by ultrafiltration membrane method.
• the obtained sol was a water-dispersed sol of stannic oxide colloidal particles (A), with an SnO2 concentration of 10.0% by mass and a primary particle diameter of 10 to 15 nm as observed with a transmission electron microscope.
• the resulting sol was an aqueous dispersion sol of silicon dioxide-stannic oxide composite oxide colloidal particles (B1), with a total metal oxide concentration ( SnO2 and SiO2 ) of 2.5% by mass, and a primary particle diameter of 1 to 4 nm as observed by a transmission electron microscope.
• the obtained sol was a water-dispersed sol of stannic oxide colloidal particles (C1) coated with silicon dioxide-stannic oxide composite oxide, with a total metal oxide ( SnO2 and SiO2 ) concentration of 30.5 mass% and an average particle diameter of 19 nm measured by dynamic light scattering (DLS).
• aqueous dispersion sol of stannic oxide colloidal particles (C1) coated with silicon dioxide-stannic oxide composite oxide 100 g was replaced with methanol using a rotary evaporator to obtain a methanol dispersion sol of stannic oxide colloidal particles (C2) coated with silicon dioxide-stannic oxide composite oxide.
• the resulting sol had a total metal oxide ( SnO2 and SiO2 ) concentration of 30.5 mass% and an average particle size of 21 nm as measured by dynamic light scattering (DLS).
• aqueous dispersion sol of stannic oxide colloidal particles (C3) coated with silicon dioxide-stannic oxide composite oxide was passed through a column packed with a hydrogen cation exchange resin.
• a water-dispersed sol 3.5 g of tri-n-pentylamine was added and concentrated by ultrafiltration membrane method.
• the obtained sol was a water-dispersed sol of stannic oxide colloidal particles (C3) coated with silicon dioxide-stannic oxide composite oxide, and had a total metal oxide ( SnO2 and SiO2 ) concentration of 30.5 mass% and an average particle size of 19 nm as measured by dynamic light scattering (DLS).
• DLS dynamic light scattering
• aqueous dispersion sol of stannic oxide colloidal particles (C3) coated with silicon dioxide-stannic oxide composite oxide 100 g was replaced with methanol using a rotary evaporator to obtain a methanol dispersion sol of stannic oxide colloidal particles (C4) coated with silicon dioxide-stannic oxide composite oxide.
• the resulting sol had a total metal oxide ( SnO2 and SiO2 ) concentration of 19.3 mass% and an average particle size of 19 nm as measured by dynamic light scattering (DLS).
• the obtained sol was a water-dispersed sol of stannic oxide colloidal particles (C5) coated with antimony pentoxide colloidal particles, had a total metal oxide ( SnO2 and Sb2O5 ) concentration of 30.2 mass%, and an average particle diameter of 16 nm as measured by dynamic light scattering (DLS).
• stannic oxide colloidal particles C5 coated with antimony pentoxide colloidal particles, had a total metal oxide ( SnO2 and Sb2O5 ) concentration of 30.2 mass%, and an average particle diameter of 16 nm as measured by dynamic light scattering (DLS).
• the resulting sol had a total metal oxide ( SnO2 and SiO2 ) concentration of 30.5 mass% and an average particle size of 21 nm as measured by dynamic light scattering (DLS).
• the mixture was then passed through a column packed with a hydrogen cation exchange resin.
• 3.8 g of tri-n-pentylamine was added to the aqueous dispersion sol obtained, and the mixture was concentrated by an ultrafiltration membrane method.
• the obtained sol had a total metal oxide (SnO 2 and Sb 2 O 5 ) concentration of 15.5% by mass, and an average particle size of 20 nm as determined by dynamic light scattering (DLS).
• 100 g of the water-dispersed sol of tin oxide-antimony oxide composite particles (C7) was replaced with methanol using a rotary evaporator to obtain a methanol-dispersed sol of stannic oxide colloidal particles (C8) coated with silicon dioxide-stannic oxide composite oxide.
• the resulting sol had a total metal oxide ( SnO2 and SiO2 ) concentration of 30.4 mass% and an average particle size of 106 nm as measured by dynamic light scattering (DLS).
• Examples 1-2 to 1-9 Charge transporting ink compositions were prepared in the same manner as in Example 1-1, except that dipropylene glycol, 2-methyl-2,4-pentanediol, 3-methyl-1,5-pentanediol, diethylene glycol monomethyl ether, triethylene glycol monomethyl ether, cyclohexanone, isophorone, and propylene carbonate were used instead of ethanol.
• Example 2-1 0.06 g of the sol of C4 prepared in Production Example 2 was added to 3.12 g of ethanol, stirred, and filtered through a PP syringe filter having a pore size of 0.2 ⁇ m to prepare a charge transporting ink composition.
• Examples 2-2 to 2-9 Charge transporting ink compositions were prepared in the same manner as in Example 2-1, except that dipropylene glycol, 2-methyl-2,4-pentanediol, 3-methyl-1,5-pentanediol, diethylene glycol monomethyl ether, triethylene glycol monomethyl ether, cyclohexanone, isophorone, and propylene carbonate were used instead of ethanol.
• Example 3-1 0.05 g of the sol of C6 prepared in Production Example 3 was added to 3.00 g of ethanol, stirred, and filtered through a PP syringe filter having a pore size of 0.2 ⁇ m to prepare a charge transporting ink composition.
• Examples 3-2 to 3-9 Charge transporting ink compositions were prepared in the same manner as in Example 3-1, except that dipropylene glycol, 2-methyl-2,4-pentanediol, 3-methyl-1,5-pentanediol, diethylene glycol monomethyl ether, triethylene glycol monomethyl ether, cyclohexanone, isophorone, and propylene carbonate were used instead of ethanol.
• Example 4-1 0.05 g of the sol of C8 prepared in Production Example 4 was added to 3.00 g of ethanol, stirred, and filtered through a PP syringe filter having a pore size of 0.2 ⁇ m to prepare a charge transporting ink composition.
• Examples 4-2 to 4-9 Charge transporting ink compositions were prepared in the same manner as in Example 4-1, except that dipropylene glycol, 2-methyl-2,4-pentanediol, 3-methyl-1,5-pentanediol, diethylene glycol monomethyl ether, triethylene glycol monomethyl ether, cyclohexanone, isophorone, and propylene carbonate were used instead of ethanol.
• the charge transport ink composition containing SnO2 nanoparticles with the surface of the SnO2 nanoparticles coated with a metal oxide as a core was a colorless and transparent liquid or a liquid with a slight colloidal color even after mixing with an organic solvent, and showed good dispersibility.
• the charge transport ink composition containing SnO2 nanoparticles with the surface not coated with a metal oxide showed white turbidity and precipitation after mixing with an organic solvent, and showed poor dispersibility. From the above, a charge transport ink composition with high dispersibility in an organic solvent was obtained from the present invention.
• Examples 5-2 to 5-9 Charge transporting ink compositions were prepared and charge transporting thin films were formed in the same manner as in Example 5-1, except that dipropylene glycol, 2-methyl-2,4-pentanediol, 3-methyl-1,5-pentanediol, diethylene glycol monomethyl ether, triethylene glycol monomethyl ether, cyclohexanone, isophorone, and propylene carbonate were used instead of ethanol.
• Example 6-1 0.50 g of the sol of C4 prepared in Production Example 2 was added to 2.10 g of ethanol, stirred, and filtered through a PP syringe filter with a pore size of 0.2 ⁇ m to prepare a charge transporting ink composition.
• the obtained charge transporting ink composition was applied onto an ITO-glass substrate using a spin coater, then dried at 120° C. for 1 minute, and the substrate was moved into a glove box and baked at 200° C. for 15 minutes under nitrogen to form a charge transporting thin film with a thickness of 50 nm on the substrate.
• the ITO-glass substrate was used after removing impurities on the surface using a plasma cleaning device (150 W, 30 seconds).
• Examples 6-2 to 6-9 Charge transporting ink compositions were prepared and charge transporting thin films were formed in the same manner as in Example 6-1, except that dipropylene glycol, 2-methyl-2,4-pentanediol, 3-methyl-1,5-pentanediol, diethylene glycol monomethyl ether, triethylene glycol monomethyl ether, cyclohexanone, isophorone, and propylene carbonate were used instead of ethanol.
• Example 7-1 0.50 g of the sol of C6 prepared in Production Example 3 was added to 2.50 g of ethanol, stirred, and filtered through a PP syringe filter with a pore size of 0.2 ⁇ m to prepare a charge transporting ink composition.
• the obtained charge transporting ink composition was applied onto an ITO-glass substrate using a spin coater, then dried at 120° C. for 1 minute, and the substrate was moved into a glove box and baked at 200° C. for 15 minutes under nitrogen to form a charge transporting thin film with a thickness of 50 nm on the substrate.
• the ITO-glass substrate was used after removing impurities on the surface using a plasma cleaning device (150 W, 30 seconds).
• Example 7-2 to 7-9 Charge transporting ink compositions were prepared and charge transporting thin films were formed in the same manner as in Example 7-1, except that dipropylene glycol, 2-methyl-2,4-pentanediol, 3-methyl-1,5-pentanediol, diethylene glycol monomethyl ether, triethylene glycol monomethyl ether, cyclohexanone, isophorone, and propylene carbonate were used instead of ethanol.
• Example 8-1 0.50 g of the C8 sol prepared in Production Example 4 was added to 2.50 g of ethanol, stirred, and filtered through a PP syringe filter with a pore size of 0.2 ⁇ m to prepare a charge transporting ink composition.
• the obtained charge transporting ink composition was applied onto an ITO-glass substrate using a spin coater, then dried at 120° C. for 1 minute, and the substrate was moved into a glove box and baked at 200° C. for 15 minutes under nitrogen to form a charge transporting thin film with a thickness of 50 nm on the substrate.
• the ITO-glass substrate was used after removing impurities on the surface using a plasma cleaning device (150 W, 30 seconds).
• Example 8-2 to 8-9 Charge transporting ink compositions were prepared and charge transporting thin films were formed in the same manner as in Example 8-1, except that dipropylene glycol, 2-methyl-2,4-pentanediol, 3-methyl-1,5-pentanediol, diethylene glycol monomethyl ether, triethylene glycol monomethyl ether, cyclohexanone, isophorone, and propylene carbonate were used instead of ethanol.
• the flatness of the charge transporting thin film was evaluated by the following method.
• the arithmetic mean surface roughness Ra of the charge transport thin film was evaluated using a micro-profile measuring instrument for the spin-coated films obtained in Examples 5-1 to 5-9, Examples 6-1 to 6-9, Examples 7-1 to 7-9, Examples 8-1 to 8-9, and Comparative Examples 3-1 to 3-9.
• the measurement range of the micro-profile measuring instrument was 0.2 mm. The results are shown in Table 2.
• the arithmetic average surface roughness Ra of the charge transporting thin film formed from the charge transporting ink composition containing SnO2 nanoparticles whose surfaces are coated with metal oxides using SnO2 nanoparticles as nuclei was small, showing good flatness.
• the charge transporting thin film formed from the charge transporting ink composition containing SnO2 nanoparticles whose surfaces are not coated with metal oxides showed significantly poor flatness, such as aggregation and film formation failure. From the above, it was found from the present invention that a charge transporting thin film with high flatness can be obtained by using a charge transporting ink composition with high dispersibility.
• the obtained charge transporting ink composition was applied to an ITO substrate (Foresight Co., Ltd., product name ITO (50 nm) Zebra substrate_ver2.0, a 25 mm x 25 mm x 0.7 mm glass substrate with a 50 nm thick ITO film patterned on the surface) with impurities removed from the substrate surface by an O 2 plasma cleaning device (150 W, 30 seconds) using a spin coater, and then pre-baked at 120° C. for 30 seconds in an air atmosphere. Next, the substrate was baked at 200° C. for 15 minutes in a nitrogen atmosphere to form a 50 nm thin film on the ITO substrate.
• ITO substrate Formsight Co., Ltd., product name ITO (50 nm) Zebra substrate_ver2.0, a 25 mm x 25 mm x 0.7 mm glass substrate with a 50 nm thick ITO film patterned on the surface
• An aluminum thin film with a thickness of 80 nm was formed on the surface of the obtained thin film using a vapor deposition device at a vacuum degree of 1.0 ⁇ 10 ⁇ 5 Pa and 0.2 nm/second. Thereafter, in order to prevent deterioration of characteristics due to the influence of oxygen, water, etc.
• the ITO substrate and a desiccant (manufactured by DYNIC Co., Ltd., product name HD-071010W-40) were placed between sealing substrates (manufactured by Premium Glass Co., Ltd., cell size 19 mm x 21 mm x 0.7 mm, excavation depth 0.4 mm or more) in a nitrogen atmosphere with an oxygen concentration of 2 ppm or less and a dew point of -76°C or less, and the sealing substrates were bonded together with an adhesive (manufactured by MORESCO Co., Ltd., product name MORESCO Moisture Cut WB90US(P)).
• sealing substrates manufactured by Premium Glass Co., Ltd., cell size 19 mm x 21 mm x 0.7 mm, excavation depth 0.4 mm or more
• an adhesive manufactured by MORESCO Co., Ltd., product name MORESCO Moisture Cut WB90US(P)
• the bonded sealing substrates were irradiated with UV light (wavelength: 365 nm, irradiation amount: 6,000 mJ/ cm2 ), and then annealed at 80°C for 1 hour to harden the adhesive, thereby obtaining an electron-only device (EOD).
• UV light wavelength: 365 nm, irradiation amount: 6,000 mJ/ cm2
• EOD electron-only device
• Example 9-2 to 9-8 Charge transporting ink compositions were prepared in the same manner as in Example 9-1, except that 2-methyl-2,4-pentanediol, 3-methyl-1,5-pentanediol, diethylene glycol monomethyl ether, triethylene glycol monomethyl ether, cyclohexanone, isophorone, and propylene carbonate were used instead of ethanol, and electron-only devices (EODs) were obtained.
• EODs electron-only devices
• the current density of the electron-only device (EOD) was measured and evaluated by the following method. A voltage of 1.0 V was applied for 0.01 seconds at room temperature and normal pressure to the electron-only devices (EOD) obtained in Examples 9-1 to 9-8 to measure the current density. The results are shown in Table 3.
• the charge transporting thin film formed from the charge transporting ink composition containing SnO2 nanoparticles whose surfaces are coated with metal oxides using SnO2 nanoparticles as cores exhibited charge transport properties. From the above, it was found that the charge transporting thin film formed from the charge transporting ink composition of the present invention has sufficient performance to function as an electron transport layer, etc.

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