WO2015012093A1

WO2015012093A1 - Organic electroluminescent element production method and coat solution

Info

Publication number: WO2015012093A1
Application number: PCT/JP2014/068021
Authority: WO
Inventors: 小林　康伸; 晃央前田
Original assignee: コニカミノルタ株式会社
Priority date: 2013-07-26
Filing date: 2014-07-07
Publication date: 2015-01-29
Also published as: JPWO2015012093A1

Abstract

An objective of the present invention is to provide a method for producing a flexible organic EL element whereby waveguide loss is reduced and light extraction efficiency is improved without loss of optical transparency. This organic EL element production method comprises a step of forming a light-scattering layer over a resin substrate and a step of forming a smoothing layer over the light-scattering layer, characterized by having in the step of forming the smoothing layer: a step of preparing a coat solution having a viscosity in the range of 3 to 30 mPa･s and containing high-refractive index nanosol particles, a binder and an organic solvent, a step of applying the coat solution by an inkjet coating method, a step of drying the applied coat solution by irradiating with a wavelength-controlled infrared radiation, and a step of curing the dried coat solution by irradiating with an excimer beam.

Description

Manufacturing method of organic electroluminescence device and coating liquid

The present invention relates to a method for producing an organic electroluminescence element and a coating solution. More specifically, the present invention relates to a method for manufacturing a flexible organic EL element that reduces waveguide loss and improves light extraction efficiency without impairing light transmittance, and a coating liquid used in the manufacturing method.

Organic electroluminescence elements (organic EL elements) that use organic electroluminescence (EL) are thin-film, completely solid elements that can emit light at a low voltage of several volts to several tens of volts, and have high brightness. It has many excellent features such as high luminous efficiency, thinness and light weight. For this reason, it has been attracting attention in recent years as surface light emitters such as backlights for various displays, display boards such as signboards and emergency lights, and illumination light sources. On the other hand, the light extraction efficiency of the organic EL element is about 20%, and it is known that the loss in the element is large.

FIG. 2 is a schematic cross-sectional view of a conventional organic EL element. The organic EL element 300 includes a metal electrode 302, an organic functional layer 304 having a refractive index of approximately 1.8, a transparent electrode 306 having a refractive index of approximately 1.8, and a refractive index of approximately 1.5 in order from the lower layer in the drawing. A transparent substrate 308 is laminated. Note that arrows represented by reference numerals 310a to 310e in the drawing indicate characteristic light among the light generated from the organic functional layer 304.

The light 310a is light perpendicular to the light emitting surface of the organic functional layer 304, and is transmitted through the transparent substrate 308 and extracted to the light extraction side (air side).
The light 310b is light that is incident on the interface between the transparent substrate 308 and air at a shallow angle less than the critical angle, and is refracted at the interface between the transparent substrate 308 and air and extracted to the light extraction side.
The light 310c is light that is incident on the interface between the transparent substrate 308 and air at an angle deeper than the critical angle, and is light that is totally reflected at the interface between the transparent substrate 308 and air and cannot be extracted to the light extraction side. The loss due to this is called substrate loss, and there is usually a loss of about 20%.
The light 310 d is light that satisfies the resonance condition among light incident on the interface between the transparent electrode 306 and the transparent substrate 308 at an angle deeper than the critical angle, and is totally reflected at the interface between the transparent electrode 306 and the transparent substrate 308. The light is generated in a guided mode and is confined in the organic functional layer 304 and the transparent electrode 306. The loss due to this is called waveguide loss, and there is usually a loss of about 20-25%.
The light 310 e is light that enters the metal electrode 302 and interacts with free electrons in the metal electrode 302 to generate a plasmon mode, which is a kind of waveguide mode, and is confined in the vicinity of the surface of the metal electrode 302. This loss is called plasmon loss, and there is usually a loss of about 30-40%.

Thus, in the conventional organic EL element 300, there are substrate loss, waveguide loss, and plasmon loss. Therefore, if these losses are reduced, more light can be extracted.

For the purpose of improving the light extraction efficiency, an organic EL element having a structure in which a light extraction layer for extracting light is laminated between a transparent electrode and a substrate is conventionally known.
As a conventional method for forming a light extraction layer, a method of using a thermosetting resin and curing the coating film by heating is common. This can be realized because it is a glass substrate. As a coating method, spin coating or slot die coating is generally used. This can also be said to be a coating method that can be used because it is a glass substrate having no problem in surface smoothness.

On the other hand, in recent years, organic EL elements have been required to have flexible characteristics that can bend the light source itself, which is not found in conventional lighting and LED lighting. Realization of such flexible characteristics is difficult as long as glass is used for the substrate. An ultra-thin glass substrate has been devised to give glass flexibility, but it is difficult to handle because it is easily broken, and there is a limit to use it for mass-produced products.

In contrast, resin materials are inherently flexible and do not break, and some materials are as transparent as glass. If a substrate containing these resins as a main component is used, an organic EL element having flexibility can be manufactured. However, since the resin material is organic, it is vulnerable to heat.

As described above, in order to give flexibility to the organic EL element, it is possible to produce a light extraction layer using a resin substrate and using a resin other than the thermosetting resin by using an inkjet coating method or the like. Necessary. Among these conditions, it was particularly difficult to apply and film a resin other than a thermosetting resin by an ink jet coating method.

Usually, an ultraviolet curable resin is mentioned as a resin other than the thermosetting resin, but the ultraviolet curable resin is generally made of a monomer. The coating solution containing this ultraviolet curable resin has a low viscosity for use in the inkjet coating method. In addition, a drying process is required to harden the film, but if a normal heating method is used for drying, the resin substrate is deformed by heat, and the performance and yield as an organic EL element are greatly reduced. End up. For this reason, in order to give an organic EL element flexibility, it has been necessary to devise materials and process conditions that have not existed in the past.

For example, Patent Document 1 discloses a technique for defining the viscosity of a particle dispersion coating liquid and forming a light extraction layer by spray coating or ink jet coating as a coating method.
By the way, as a structure of the light extraction layer, a light scattering layer, a smoothing layer having a high refractive index and requiring smoothness on the surface from the viewpoint of film forming properties of the electrode, which requires precise coating, However, the light extraction layer forming technique disclosed in Patent Document 1 is for a so-called light scattering layer and not for a smoothing layer.

For these reasons, a method for producing an organic EL element excellent in film formability and optical performance has been desired to realize flexibility.

European Patent No. 1947910

The present invention has been made in view of the above-described problems and circumstances, and a solution to the problem is a flexible organic EL that reduces waveguide loss and improves light extraction efficiency without impairing light transmittance. It is providing the coating liquid used for the manufacturing method of an element, and the said manufacturing method.

In order to solve the above-mentioned problems, the present inventor sequentially has a light scattering layer, a smoothing layer, a first electrode, an organic functional layer, and a second electrode on a resin substrate in a process of examining the cause of the above-described problem. In the method for producing a laminated organic EL device, in the step of forming a smoothing layer, it contains high-refractive-index nanosol particles, a binder, and an organic solvent, and has a viscosity in the range of 3 to 30 mPa · s. Excimer light is applied to the step of preparing a coating solution, the step of applying the coating solution by an ink jet coating method, the step of irradiating the coating solution after application with a wavelength-controlled infrared ray, and the coating solution after drying. And the step of curing by irradiation, it has been found that waveguide loss can be reduced and light extraction efficiency can be improved without impairing light transmittance while maintaining flexibility. It led to.

That is, the above-mentioned problem according to the present invention is solved by the following means.

1. A method for producing an organic electroluminescent element in which a light scattering layer, a smoothing layer, a first electrode, an organic functional layer, and a second electrode are sequentially laminated on a resin substrate,
Forming the light scattering layer on the resin substrate;
Forming the smoothing layer on the light scattering layer;
With
In the step of forming the smoothing layer,
A step of preparing a coating liquid containing high refractive index nanosol particles, a binder, and an organic solvent and having a viscosity in the range of 3 to 30 mPa · s;
Applying the coating solution by an ink jet coating method;
A step of irradiating the coating liquid after coating with a wavelength-controlled infrared ray and drying,
A step of irradiating and curing the coating liquid after drying with excimer light;
The manufacturing method of the organic electroluminescent element characterized by having.

2. 2. The method for producing an organic electroluminescent element according to item 1, wherein the viscosity of the organic solvent is in the range of 5 to 100 mPa · s.

3. 3. The method for producing an organic electroluminescent element according to item 1 or 2, wherein the vapor pressure of the organic solvent is in a range of 1.0 to 1000 Pa.

4. A coating liquid comprising nanosol particles having a high refractive index, a binder, and an organic solvent, and having a viscosity in the range of 3 to 30 mPa · s.

5. Item 5. The coating solution according to Item 4, wherein the organic solvent has a viscosity in the range of 5 to 100 mPa · s.

6. 6. The coating solution according to item 4 or 5, wherein the vapor pressure of the organic solvent is in the range of 1.0 to 1000 Pa.

By the above-described means of the present invention, a method for producing a flexible organic EL element having reduced waveguide loss and improved light extraction efficiency without impairing light transmittance, and a coating solution used in the production method Can be provided.

The expression mechanism / action mechanism of the effect of the present invention is not clear, but is presumed as follows.

That is, if a resin substrate is used as a support substrate of an organic EL element and a binder such as an ultraviolet curable resin can be applied and formed into a film by an ink jet coating method, flexibility as an organic EL element can be maintained. However, a coating solution containing a binder such as an ultraviolet curable resin has a problem of low viscosity when used in an inkjet coating method.
Therefore, it is considered that by incorporating an organic solvent in the coating solution, the viscosity of the coating solution can be adjusted within a predetermined range, and the light extraction efficiency of the organic EL element can be improved while maintaining flexibility.

Schematic sectional view showing an example of an organic EL device according to the present invention Schematic sectional view of a conventional organic EL device

The method for producing an organic EL element of the present invention comprises a step of forming a light scattering layer on a resin substrate, and a step of forming a smoothing layer on the light scattering layer, and a step of forming the smoothing layer. Then, a step of preparing a coating solution containing high refractive index nanosol particles, a binder, and an organic solvent and having a viscosity in the range of 3 to 30 mPa · s, and coating the coating solution by an inkjet coating method The method includes a step, a step of irradiating the coating liquid after application with a wavelength-controlled infrared ray and drying, and a step of irradiating the coating liquid after drying with an excimer light and curing. This feature is a technical feature common to the inventions according to claims 1 to 6.

As an embodiment of the present invention, the viscosity of the organic solvent is preferably in the range of 5 to 100 mPa · s from the viewpoint of ejection stability.

As an embodiment of the present invention, the vapor pressure of the organic solvent is preferably in the range of 1.0 to 1000 Pa from the viewpoint of preventing nozzle clogging.

The coating liquid of the present invention contains high refractive index nanosol particles, a binder, and an organic solvent, and has a viscosity in the range of 3 to 30 mPa · s.
In an embodiment of the present invention, the viscosity of the organic solvent is preferably in the range of 5 to 100 mPa · s from the viewpoint of ejection stability, and further, from the viewpoint of preventing nozzle clogging, the vapor pressure is 1. A range of 0 to 1000 Pa is preferable.

Hereinafter, the present invention, its components, and modes and modes for carrying out the present invention will be described in detail. In the present application, “˜” representing a numerical range is used in the sense that numerical values described before and after the numerical value range are included as a lower limit value and an upper limit value.

≪Configuration of organic EL element≫
FIG. 1 shows an example of the configuration of the organic EL element according to the present invention.
As shown in FIG. 1, the organic EL element 100 is configured by laminating a light extraction layer 20, a first electrode 30, an organic functional layer 40, and a second electrode 50 on a resin substrate 10 having flexibility. .
The light extraction layer 20 includes a light scattering layer 22 and a smoothing layer 24, and is laminated on the resin substrate 10 in this order.
The organic functional layer 40 includes a hole injection layer 41, a hole transport layer 42, a light emitting layer 43, an electron transport layer 44, and an electron injection layer 45, and is stacked on the first electrode 30 in this order.

Hereinafter, each layer constituting the organic EL element 100 according to the present invention will be described.

≪Light extraction layer (20) ≫
The light extraction layer is a layer provided between the resin substrate and the first electrode, and has a two-layer structure in which a light scattering layer and a smoothing layer are laminated in order from the resin substrate side.
The light extraction layer is provided to extract waveguide mode light confined in the light emitting layer of the organic EL element and plasmon mode light reflected from the second electrode.

<Smoothing layer (24)>
(1) Structure and characteristics of smoothing layer The smoothing layer according to the present invention has a structure in which nano-sol particles having a high refractive index are contained in a binder.
In the present invention, the nanosol particle is a fine particle (colloidal particle) having a particle size of nanometer order dispersed in a dispersion medium, and is defined as a particle having a particle size in the range of 1 to 300 nm. Is done. The particles include discrete particles (primary particles) and aggregated particles (secondary particles). In the present invention, the nanosol particles including the secondary particles Define.

As the binder used for the smoothing layer, the same light scattering layer as described later can be used, but an ultraviolet curable resin or an electron beam curable resin can be used. Among these, an ultraviolet curable resin is more preferable because the physical properties of the coating liquid can be adjusted with an organic solvent.
Because UV curable resin cures in just a few seconds with UV light energy, unlike thermosetting methods, it is less susceptible to damage and deformation due to heating, it can be manufactured efficiently, and there are no variations in quality. Can be mentioned. Thereby, since deformation of the substrate does not occur even when the resin substrate is used, no manufacturing trouble occurs, and the yield can be improved.

The highly refractive particles contained in the smoothing layer are preferably fine particle nanosols.
The lower limit of the refractive index of the highly refractive particles is preferably 1.7 or more in a bulk state, more preferably 1.85 or more, still more preferably 2.0 or more, and 2.5 The above is particularly preferable. In addition, the upper limit of the refractive index of the highly refractive particles is preferably 3.0 or less. If the refractive index of the highly refractive particles is 1.7 or more, the objective effect of the present invention can be sufficiently exhibited. When the refractive index of the highly refractive particles is 3.0 or less, multiple scattering in the layer is suppressed and transparency is not lowered.

The average particle size of the highly refractive particles is preferably in the range of 5 to 300 nm, more preferably in the range of 10 to 200 nm, and particularly preferably in the range of 20 to 100 nm. If the average particle diameter of the high refractive particles is 5 nm or more, the high refractive particles are prevented from aggregating and the transparency is not lowered. In addition, the surface area of the high refractive particles as a whole is not increased, and the catalytic activity is suppressed, so that deterioration of the smoothing layer and adjacent layers can be prevented. When the average particle diameter of the highly refractive particles is 300 nm or less, the transparency of the smoothing layer is not lowered. The average particle size distribution is not particularly limited as long as the effect of the present invention is not impaired, and may be wide or narrow, or may have a plurality of distributions.
The average particle diameter in the present invention can be measured by, for example, an apparatus using a dynamic light scattering method such as Nanotrack UPA-EX150 manufactured by Nikkiso Co., Ltd., or image processing of an electron micrograph.

The lower limit of the content of the highly refractive particles is preferably 50% by mass or more, more preferably 60% by mass or more, and further preferably 70% by mass or more with respect to the total mass. Further, the upper limit of the content of the highly refractive particles is preferably 97% by mass or less, and more preferably 95% by mass or less. If the content of the highly refractive particles is 50% by mass or more, it becomes easy to set the refractive index of the smoothing layer to 1.80 or more. When the content of the high refractive particles is 97% by mass or less, there is no hindrance to the production by the coating method of the smoothing layer, and the strength and bending resistance of the layer after drying are not lowered.

The high refractive index nanosol particles are not particularly limited and may be appropriately selected according to the purpose. The fine particles may be organic fine particles or inorganic fine particles. Preferably there is.
Examples of organic fine particles having a high refractive index include polymethyl methacrylate beads, acrylic-styrene copolymer beads, melamine beads, polycarbonate beads, styrene beads, crosslinked polystyrene beads, polyvinyl chloride beads, benzoguanamine-melamine formaldehyde beads, and the like. Can be mentioned.
Examples of the inorganic fine particles having a high refractive index include inorganic oxide particles made of at least one oxide selected from zirconium, titanium, aluminum, indium, zinc, tin, antimony and the like. Specific examples of the inorganic oxide particles include ZrO ₂ , TiO ₂ , BaTiO ₃ , Al ₂ O ₃ , In ₂ O ₃ , ZnO, SnO ₂ , Sb ₂ O ₃ , ITO (Indium Tin Oxide: indium tin oxide). _), SiO 2, ZrSiO _4, zeolite, and among _{_{_{them, TiO 2, BaTiO 3, ZrO}}} 2, ZnO, SnO 2 are preferred, TiO ₂ is most preferred. Further, among TiO ₂ , rutile type is preferable to anatase type because the weather resistance of the light scattering layer and the adjacent layer is high because the catalytic activity is low, and the refractive index is high.

These highly refractive particles may be subjected to a surface treatment on the particle surface from the viewpoint of improving the dispersibility and stability of the dispersion when dispersed in a binder.
Examples of the surface treatment material include different inorganic oxides such as silicon oxide and zirconium oxide, metal hydroxides such as aluminum hydroxide, organic acids such as organosiloxane and stearic acid, and the like. These surface treatment materials may be used individually by 1 type, and may be used in combination of multiple types. Among these, from the viewpoint of the stability of the dispersion, the surface treatment material is preferably a different inorganic oxide and / or metal hydroxide, more preferably a metal hydroxide.
When the inorganic oxide particles are surface-coated with a surface treatment material, the coating amount (in general, this coating amount is indicated by the mass ratio of the surface treatment material used on the surface of the particle to the mass of the particles). Is preferably in the range of 0.01 to 99% by mass. When the coating amount of the surface treatment material is 0.01% by mass or more, the effect of improving the dispersibility and stability by the surface treatment can be sufficiently obtained. Moreover, if the coating amount is 99% by mass or less, the refractive index of the high refractive index smoothing layer can be kept high.

In addition, as the highly refractive particles, quantum dots described in International Publication No. 2009/014707, US Pat. No. 6,608,439, etc. can be suitably used.

The smoothing layer is preferably a high refractive index layer having a refractive index in the range of 1.7 to 2.0. If the refractive index of the smoothing layer is 1.7 or more, the light can be guided to the resin substrate side without confining the waveguide mode light in the organic functional layer or the transparent electrode. If the refractive index of the smoothing layer is 2.0 or less, the film strength of the smoothing layer can be maintained high.
The smoothing layer may be formed of a single material having a refractive index in the range of 1.7 to 2.0, or two or more compounds may be mixed to form a layer. In the case of such a mixed system, the refractive index of the smoothing layer can be substituted by a calculated refractive index calculated by a total value obtained by multiplying the refractive index specific to each material by the mixing ratio. In this case, the refractive index of each material may be less than 1.7 or higher than 2.0, and the refractive index of the smoothing layer formed by mixing is in the range of 1.7 to 2.0. It only has to be.

It is important that the smoothing layer has a flatness that allows the first electrode to be satisfactorily formed thereon. The flatness is such that the surface roughness Ra is less than 100 nm, preferably less than 30 nm, more preferably less than 10 nm, and most preferably less than 5 nm.
In addition, in this invention, surface roughness Ra is arithmetic mean roughness and is surface roughness prescribed | regulated by JISB0601. The surface roughness Ra was measured using an AFM (Atomic Force Microscope) SPI3800N DFM manufactured by SII. The measurement range for one time was 10 μm × 10 μm, the measurement location was changed, and the measurement was performed three times. The average of the Ra values obtained in each measurement was taken as the measurement value.

The function of the smoothing layer is to smooth the surface of the light scattering layer to prevent the first electrode from being uneven, and to prevent the electrode from being short-circuited, so-called short-circuiting, so that the light-emitting layer does not shine. The other is that the light scattering layer mainly has the function of scattering, whereas the smoothing layer mainly passes the emitted light without reflecting it at the interface. Thus, by dividing the function between the two, the degree of freedom of the element configuration can be increased, and thereby the reliability of the organic EL element can be further improved.

(2) Method for producing smoothing layer The method for producing the smoothing layer of the present invention mainly comprises:
(I) a step of preparing a coating liquid containing high-refractive-index nanosol particles, a binder, and an organic solvent, and having a viscosity in the range of 3 to 30 mPa · s;
(Ii) a step of applying a coating liquid by an inkjet coating method;
(Iii) A step of irradiating the coating liquid after coating with a wavelength-controlled infrared ray and drying;
(Iv) a step of irradiating and curing the excimer light to the coating solution after drying;
have.
Hereinafter, each step will be described.

(I) Coating Solution Adjustment Step In the coating solution adjustment step, the coating solution is prepared so that the viscosity is in the range of 3 to 30 mPa · s.
More specifically, the viscosity of the coating solution is adjusted by adding an organic solvent in addition to the high refractive index nanosol particles and the binder.

The viscosity of the coating solution is adjusted within the range of 3 to 30 mPa · s. However, when the viscosity of the coating solution is smaller than 3 mPa · s, the coating solution cannot be held by the head nozzle when performing inkjet coating. It will flow out and will not be ejected accurately. When the viscosity of the coating solution is greater than 30 mPa · s, the fluidity of the coating solution is reduced, so that the emission property of the coating solution from the ink jet nozzle is lowered, and in the worst case, the coating solution cannot be emitted.
The viscosity of the coating solution is preferably in the range of 4 to 25 mPa · s, more preferably in the range of 5 to 15 mPa · s.
In the present invention, the viscosity is a value measured at 25 ° C. using a conical plate type rotational viscometer.

Examples of the organic solvent used in the smoothing layer coating solution include 1,2-butanediol, 1,2-pentanediol, 1,3-butanediol, 1,3-propanediol, 1,4-butanediol, 1-octanol, 2-amino-2-methyl-1-propanol, 2,2 '-(n-butyl) iminodiethanol, 2-octanol, 2-dibutylaminoethanol, 2-pyrrolidone, 2-phenoxyethanol, 2-butanol 2-propanol, 2-methyl-1,3-propanediol, 2-methyl-1-propanol, 2-methyl-2,4-pentanediol (PD), 2-methylcyclohexanone, 3,3,5-trimethyl Cyclohexanone, 3,4-dimethylcyclohexanone, isophorone, 4-methylcyclohexanone, n-undec Alcohol, n-nonyl alcohol, ethylene glycol, ethylene glycol monoisopropyl ether, ethylene glycol monobutyl ether, diethylene glycol, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, diethylene glycol monobutyl ether acetate, diethylene glycol monomethyl ether, dipropylene glycol, dipropylene glycol monoethyl Ether, dipropylene glycol monobutyl ether, dipropylene glycol monopropyl ether, dipropylene glycol monomethyl ether, dimethylaminoethanol, tetraethylene glycol, tetraethylene glycol dimethyl ether, tetraethylene glycol monobutyl ether, tet Hydrothiophene-1,1-dioxide, triethylene glycol, triethylene glycol monobutyl ether, triethylene glycol monomethyl ether, tridecyl alcohol, tripropylene glycol, tripropylene glycol monobutyl ether, tripropylene glycol monomethyl ether, butyl lactate, propylene glycol Benzyl alcohol, polypropylene glycol monomethyl ether, monoacetin, 2-aminoethanol, cyclohexanol, tetrahydrofurfuryl alcohol (THFA), 2- (isopropylamino) ethanol and the like.
These organic solvents may be used alone or in combination of two or more.

In the present invention, the viscosity of the organic solvent is preferably in the range of 5 to 100 mPa · s. If the viscosity of the organic solvent is 5 mPa · s or more, the viscosity of the coating solution can be adjusted. If the viscosity of the organic solvent is 100 mPa · s or less, the miscibility with the binder (resin) and nanosol particles of the smoothing layer can be ensured, and a uniform coating solution can be obtained. Can be kept in.

Furthermore, the vapor pressure of the organic solvent is preferably in the range of 1.0 to 1000 Pa. If the vapor pressure of the organic solvent is 1.0 Pa or more, it can be dried using a wavelength-controlled infrared heater, and the residual solvent can be reduced. When the vapor pressure of the organic solvent is 1000 Pa or less, the drying rate of the smoothing layer coating liquid is suppressed, and clogging of the nozzle due to drying at the inkjet nozzle portion is improved.
In addition, as a means for measuring the vapor pressure, there are various methods such as a static method, a boiling point method, an isoteniscope, a gas flow method, a DSC method, etc., depending on the property of the sample, the sample amount, and the magnitude of the vapor pressure. The method applied is different. In the present invention, the solvent vapor pressure at 25 ° C. was measured using the “static method” with the widest application range. The static method is a method in which the temperature is kept constant and the equilibrium vapor pressure at that temperature is directly measured using a pressure gauge.

Examples of the organic solvent having a preferable viscosity and vapor pressure used in the coating solution for the smoothing layer include 1,2-butanediol, 1,2-pentanediol, 1,3-butanediol, and 1,3-propanediol. 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1-octanol, 1-butanol, 1-propanol, 1-pentanol, 2-amino-2-methyl-1-propanol 2,2 '-(n-butyl) iminodiethanol, 2-octanol, 2-dibutylaminoethanol, 2-pyrrolidone, 2-phenoxyethanol, 2-butanol, 2-propanol, 2-methyl-1,3-propanediol 2-methyl-1-propanol, 2-methyl-2,4-pentanediol (PD), 2-methylcyclohexane Non, 3,3,5-trimethylcyclohexanone, 3,4-dimethylcyclohexanone, isophorone, 4-hydroxy-4-methyl-2-pentanone, 4-methylcyclohexanone, N, N-dimethylacetamide, N, N-dimethylformamide , N-undecyl alcohol, n-nonyl alcohol, γ-butyrolactone, ethylene glycol, ethylene glycol diethyl ether, ethylene glycol monoisopropyl ether, ethylene glycol monoethyl ether, ethylene glycol monoethyl ether acetate, ethylene glycol monobutyl ether, ethylene glycol Monomethyl ether, ethylene glycol monomethyl ether acetate, butyl lactate, diethanolamine, diethylene glycol dimethyl ether Ter, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, diethylene glycol monobutyl ether acetate, diethylene glycol monomethyl ether, cyclohexanone, dipropylene glycol monoethyl ether, dipropylene glycol monobutyl ether, dipropylene glycol monopropyl ether, dipropylene glycol monomethyl ether, dimethylamino Methanol, tetraethylene glycol dimethyl ether, tetraethylene glycol monobutyl ether, tetrahydrothiophene-1,1-dioxide, tridecyl alcohol, tripropylene glycol, tripropylene glycol monomonobutyl ether, tripropylene glycol monomethyl ether, propylene Glycol, propylene glycol monoethyl ether, propylene glycol monomethyl ether (PGME), propylene glycol monomethyl ether acetate, benzyl alcohol, polyethylene glycol monomethyl ether, monoacetin, 2-aminoethanol, cyclohexanol, tetrahydrofurfuryl alcohol (THFA), 2 -(Isopropylamino) ethanol and the like.
These organic solvents may be used alone or in combination of two or more. Moreover, even if it is a solvent other than these, if the conditions of a viscosity and vapor pressure are satisfy | filled by mixing 2 or more types, the combination can also be used.

By adding the organic solvent as described above to the coating liquid, drying of the coating liquid is suppressed, fluctuations in the physical properties of the coating liquid are reduced, the flying speed is reduced due to the ink jet coating method, and the emission is poor due to increased viscosity due to drying. Can be improved, and the yield can be improved.
In addition, the organic solvent which satisfy | fills the said viscosity or vapor pressure may be comprised from 1 type of organic solvents, and may be comprised from 2 or more types of organic solvents. For example, two organic solvents whose viscosity or vapor pressure is not within the above range may be mixed so that the viscosity or vapor pressure in the mixed organic solvent is within the above range, or the viscosity may be An organic solvent having a vapor pressure within the above range may be mixed with an organic solvent having a vapor pressure within the above range so as to satisfy both the viscosity and vapor pressure conditions.

(Ii) Coating step by inkjet coating method The coating method for the smoothing layer coating liquid is characterized by coating using an inkjet coating method.
As an inkjet head used in the inkjet coating method, an on-demand system or a continuous system may be used. Discharge methods include electro-mechanical conversion methods (eg, single cavity type, double cavity type, bender type, piston type, shear mode type, shared wall type, etc.), and electro-thermal conversion methods (eg, thermal Specific examples include an ink jet type, a bubble jet (registered trademark) type, an electrostatic suction type (for example, an electric field control type, a slit jet type, etc.), and a discharge type (for example, a spark jet type). However, any discharge method may be used. As a printing method, a serial head method, a line head method, or the like can be used without limitation.

(Iii) Drying step In the drying step, using a wavelength-controlled infrared heater that absorbs infrared rays, the coating solution after application is irradiated with infrared rays to dry the coating solution.

As infrared rays, infrared rays having a central wavelength in the region of 1 to 3.5 μm and 70% or more of the integrated value of all outputs are irradiated in the region.
In the infrared, “the central wavelength is in the region of 1 to 3.5 μm” means that the filament temperature is in the range of 450 to 2600 ° C., and such a temperature range is derived by the Wien displacement law.

The drying treatment conditions are not particularly limited, but the irradiation time can be adjusted by the surface temperature of the infrared filament and the wavelength control filter. For example, the filament temperature is in the range of 450 to 2600 ° C. (preferably 600 to 1200 ° C.), the wavelength control filter surface temperature is less than 200 ° C. (preferably less than 150 ° C.), and the irradiation time is in the range of 10 seconds to 30 minutes. Can be dried. Thereby, a smoothing layer having high uniformity of layer thickness distribution and high patterning accuracy can be obtained.

(Iv) Curing Step In the curing step, the dried smoothing layer is cured by irradiating with excimer light having a wavelength in the range of 150 to 230 nm.
Examples of the light source used for curing include a mercury lamp, a metal halide lamp, and an excimer lamp (wavelength 177 nm or wavelength 222 nm). Among these, an excimer lamp (wavelength 222 nm) is preferable.
The exposure amount is preferably in the range of 100 to 10000 mJ, more preferably in the range of 300 to 8000 mJ, and particularly preferably in the range of 400 to 6000 mJ. If the exposure amount is 100 mJ or more, the coating film can be effectively cured, and if the exposure amount is 10000 mJ or less, the organic matter on the coating film surface is not destroyed and the refractive index can be prevented from decreasing. it can.

An example of such an irradiation apparatus is a rare gas excimer lamp that emits vacuum ultraviolet rays within a range of 100 to 230 nm.

Noble gas atoms such as Xe, Kr, Ar, Ne, etc. are called inert gases because they are not chemically bonded to form molecules. However, rare gas atoms (excited atoms) that have gained energy by discharge or the like can be combined with other atoms to form molecules.
For example, in the case of Xe (xenon), excimer light having a wavelength of 172 nm is emitted when the excited excimer molecule Xe ₂ ^* transitions to the ground state, as shown in the following reaction formula.

e + Xe → Xe ^*
Xe ^* + 2Xe → Xe ₂ ^* + Xe
Xe ₂ ^* → Xe + Xe + hν (172 nm)

The excimer lamp is characterized by high light generation efficiency because radiation concentrates on one wavelength and almost no light other than necessary is emitted. As a result, it is possible to light up with low power input. Further, light having a long wavelength that causes a temperature rise is not emitted, and energy is irradiated at a single wavelength in the ultraviolet region, so that the temperature of the object can be kept relatively low. Furthermore, since no time is required for starting and restarting, instantaneous lighting and blinking are possible.

As a light source for efficiently irradiating excimer light, a dielectric barrier discharge lamp can be mentioned.
A dielectric barrier discharge lamp has a structure in which a discharge occurs between electrodes via a dielectric. In general, at least one electrode is disposed between a dielectric discharge vessel and the outside thereof. That's fine. As a dielectric barrier discharge lamp, for example, a rare gas such as Xe is sealed in a double cylindrical discharge vessel composed of a thick tube and a thin tube made of quartz glass, and a net-like second discharge vessel is formed outside the discharge vessel. There is one in which one electrode is provided and another electrode is provided inside the inner tube. A dielectric barrier discharge lamp generates a dielectric barrier discharge inside a discharge vessel by applying a high-frequency voltage or the like between electrodes, and generates excimer light when excimer molecules such as Xe generated by the discharge dissociate. .

<Light scattering layer (22)>
(1) Configuration and characteristics of light scattering layer The light scattering layer has a structure in which light scattering particles are dispersed in a binder. Although various materials can be applied to the binder, an organic-inorganic hybrid polymer having an organic polymer structure and a polysiloxane structure is preferable.
The refractive index of the organic-inorganic hybrid polymer without light scattering particles is about 1.5, but by dispersing the light scattering particles in an appropriate amount, the refractive index of the light scattering layer may be 1.5 or more. it can. Further, if the light scattering particles are almost transparent, light is hardly absorbed by the light scattering particles, so that the light extraction efficiency is not lowered. In addition, if light scattering particles having such a size that light is scattered are used, the light scattering effect of the waveguide mode can be obtained, and more light can be extracted.

The refractive index of the light scattering layer is preferably a high refractive index layer in the range of 1.7 to 2.0, like the smoothing layer.
The way of thinking of the refractive index when forming with the mixture is the same as in the case of the smoothing layer.

(1.1) Binder Examples of the binder of the light scattering layer according to the present invention are shown below.

(1.1.1) Organic polymer structure As the organic polymer structure of the organic-inorganic hybrid polymer, a known polymer can be used without particular limitation. For example, an alkyl group, an aryl group, an araalkyl group, a cycloalkyl group, an amino group. , Imino group, cyano group, nitro group, nitroso group, azo group, diazo group, azide group, carbonyl group, phenyl group, hydroxy group, peroxy group, acyl group, acetyl group, aldehyde group, carboxy group, amide group, imide Group, ester group, oxime group, thiol group, sulfo group, urea group, isonitrile group, allene group, acryloyl group, methacryloyl group, epoxy group, oxetane group, isocyanate group, polymer having structure, unsaturated polyester (terephthalic acid , Orthophthalic acid, isophthalic acid, bisphenol , Dicyclo, halogen-containing, halogen-containing bisphenol, etc.), polyethylene terephthalate (PET), polybutylene terephthalate, polyethylene naphthalate (PEN), polycarbonate (PC), polyarylate, polyvinyl chloride (PVC), polyethylene It is possible to use a polymer having a skeleton such as (PE), polypropylene (PP), polystyrene (PS), nylon (Ny), aromatic polyamide, polyether ether ketone, polysulfone, polyether sulfone, polyimide, and polyetherimide. it can.

It is also possible to use hydrophilic polymers, and examples of such hydrophilic polymers include water-soluble polymers, water-dispersible polymers, colloid-dispersible polymers, or mixtures thereof. Examples of these polymers include acrylic, polyester, polyamide, polyurethane, and fluorine polymers such as polyvinyl alcohol, gelatin, polyethylene oxide, polyvinyl pyrrolidone, casein, starch, agar, carrageenan, and polyacryl. Examples thereof include polymer components such as acid, polymethacrylic acid, polyacrylamide, polymethacrylamide, polystyrene sulfonic acid, cellulose, hydroxyl ethyl cellulose, carboxyl methyl cellulose, hydroxyl ethyl cellulose, dextran, dextrin, pullulan, and water-soluble polyvinyl butyral.
These polymers may be used independently and may have 2 or more types.

(1.1.2) Polysiloxane Structure Examples of the polysiloxane structure include polysiloxane (including polysilsesquioxane) having a Si—O—Si bond.
Specifically, the polysiloxane may contain [R ₃ SiO _1/2 ], [R ₂ SiO], [RSiO _3/2 ] and [SiO ₂ ] as general structural units. Here, R represents a hydrogen atom, an alkyl group having 1 to 20 carbon atoms (for example, a methyl group, an ethyl group, a propyl group, etc.), an aryl group (for example, a phenyl group), an unsaturated alkyl group (for example, a vinyl group). Etc.) are independently selected. Examples of specific polysiloxane structures include [PhSiO _3/2 ], [MeSiO _3/2 ], [HSiO _3/2 ], [MePhSiO], [Ph ₂ SiO], [PhViSiO], [ViSiO _3/2 ]. (Vi represents a vinyl group), [MeHSiO], [MeViSiO], [Me ₂ SiO], [Me ₃ SiO _1/2 ] and the like. Mixtures and copolymers of polysiloxanes can also be used.

(1.2) Light-scattering particles The light-scattering particles contained in the light-scattering layer are preferably transparent particles having an average particle size equal to or greater than the region that causes Mie scattering in the visible light region. The lower limit is preferably 0.2 μm or more.
On the other hand, the upper limit of the average particle diameter is not particularly limited as long as the effect of the present invention is not impaired.
The average particle diameter in the present invention can be measured by, for example, an apparatus using a dynamic light scattering method such as Nanotrack UPA-EX150 manufactured by Nikkiso Co., Ltd., or image processing of an electron micrograph.

The light scattering particle is not particularly limited and may be appropriately selected depending on the purpose. The light scattering particle may be an organic fine particle or an inorganic fine particle, and among them, an inorganic fine particle having a high refractive index may be used. preferable.
Examples of organic fine particles having a high refractive index include polymethyl methacrylate beads, acrylic-styrene copolymer beads, melamine beads, polycarbonate beads, styrene beads, crosslinked polystyrene beads, polyvinyl chloride beads, benzoguanamine-melamine formaldehyde beads, and the like. Can be mentioned.
Examples of the inorganic fine particles having a high refractive index include inorganic oxide particles made of at least one oxide selected from zirconium, titanium, aluminum, indium, zinc, tin, antimony and the like. Specific examples of the inorganic oxide particles include ZrO ₂ , TiO ₂ , BaTiO ₃ , Al ₂ O ₃ , In ₂ O ₃ , ZnO, SnO ₂ , Sb ₂ O ₃ , ITO, SiO ₂ , ZrSiO ₄ , zeolite. Among them, TiO ₂ , BaTiO ₃ , ZrO ₂ , ZnO and SnO ₂ are preferable, and TiO ₂ is most preferable. Further, among TiO ₂ , rutile type is preferable to anatase type because the weather resistance of the light scattering layer and the adjacent layer is high because the catalytic activity is low, and the refractive index is high.

Further, these light scattering particles may be subjected to a surface treatment on the particle surface from the viewpoint of improving the dispersibility and stability of the dispersion when dispersed in a binder.
Examples of the surface treatment material include different inorganic oxides such as silicon oxide and zirconium oxide, metal hydroxides such as aluminum hydroxide, organic acids such as organosiloxane and stearic acid, and the like. These surface treatment materials may be used individually by 1 type, and may be used in combination of multiple types. Among these, from the viewpoint of the stability of the dispersion, the surface treatment material is preferably a different inorganic oxide and / or metal hydroxide, more preferably a metal hydroxide.
When the inorganic oxide particles are surface-coated with a surface treatment material, the coating amount (in general, this coating amount is indicated by the mass ratio of the surface treatment material used on the surface of the particle to the mass of the particles). Is preferably in the range of 0.01 to 99% by mass. When the coating amount of the surface treatment material is 0.01% by mass or more, the effect of improving the dispersibility and stability by the surface treatment can be sufficiently obtained. Moreover, if the coating amount is 99% by mass or less, the refractive index of the light scattering layer having a high refractive index can be kept high.

In addition, as the light scattering particles, quantum dots described in International Publication No. 2009/014707, US Pat. No. 6,608,439, and the like can be suitably used.

The light scattering particles preferably have a refractive index of 1.7 or more, more preferably 1.85 or more, and particularly preferably 2.0 or more. If the refractive index is 1.7 or more, a sufficient difference in refractive index with respect to the binder can be obtained, and the effect of improving the light extraction efficiency can be obtained without reducing the amount of light scattering.
On the other hand, the upper limit of the refractive index of the light scattering particles is preferably less than 3.0. If the refractive index is less than 3.0, multiple scattering in the layer is suppressed, and transparency is not lowered.

Although light scattering particles are actually polydisperse particles and difficult to arrange regularly, they have a diffraction effect locally, but in many cases, the light extraction efficiency is changed by changing the direction of light by diffusion. To improve.

(2) Method for producing light scattering layer The method for producing a light scattering layer according to the present invention mainly comprises:
(I) applying a coating liquid in which light scattering particles are dispersed in a binder on a resin substrate to form a light scattering layer;
(Ii) heating the light scattering layer within a range of 100 to 280 ° C., or irradiating excimer light having a wavelength within a range of 150 to 230 nm;
However, the present invention is not particularly limited thereto.
Hereinafter, each step will be described.

(I) Step of forming light scattering layer The light scattering layer is formed by applying a coating liquid in which light scattering particles are dispersed in a binder serving as a medium on a resin substrate.
In addition to various printing methods such as gravure printing method, flexographic printing method, offset printing method, screen printing method, and ink jet printing method, the coating method of the coating liquid includes a roll coating method, a bar coating method, a casting method, a die coating method, Various coating methods such as a blade coating method, a curtain coating method, a spray coating method, and a doctor coating method can be used.

(Ii-1) Step of drying the light scattering layer The light scattering layer according to the present invention is preferably cured after drying. As a drying apparatus used for drying the light scattering layer, a commonly used drying apparatus can be used, and examples thereof include a contact hot plate and a non-contact IR heater. These apparatuses can be used without any particular limitation as long as they can heat the coating film.

(Ii-2) Step of curing light scattering layer The light scattering layer according to the present invention is cured by irradiating excimer light having a wavelength within the range of 150 to 230 nm described above, instead of the drying step. Is preferred.

≪Second electrode (50) ≫
The second electrode has a role as a cathode and a role as a mirror that reflects light toward the resin substrate.
As a constituent material of the second electrode, for example, a metal material having a reflectance of 60% or more such as aluminum, silver, nickel, titanium, sodium, calcium, or an alloy containing any of them can be used.

≪Organic functional layer (40) ≫
The organic functional layer is a single layer or a plurality of layers made of an organic compound or a complex including a light emitting layer. For example, a hole transport layer in contact with the anode (first electrode), a light emitting layer formed of a light emitting material, a cathode ( It has an electron transport layer in contact with the second electrode) and has a thickness of several nm to several hundred nm. Further, a lithium fluoride layer, an inorganic metal salt layer, a layer containing them, or the like may be formed at an arbitrary position. The light-emitting layer is made of at least one light-emitting material, and a fluorescent compound, a phosphorescent compound, or the like can be used as the light-emitting material.

As the configuration of the organic functional layer, for example, the following configurations (i) to (v) can be adopted including the above-described configuration.

(I) (anode) / light emitting layer / electron transport layer / (cathode)
(Ii) (anode) / hole transport layer / light emitting layer / electron transport layer / (cathode)
(Iii) (anode) / hole transport layer / light emitting layer / hole blocking layer / electron transport layer / (cathode)
(Iv) (anode) / hole transport layer / light emitting layer / hole blocking layer / electron transport layer / electron injection layer / (cathode) (v) (anode) / hole injection layer / hole transport layer / light emitting layer / Hole blocking layer / electron transport layer / electron injection layer / (cathode)

Also, a configuration in which two sets of organic functional layers are stacked or a configuration in which three sets of organic functional layers are stacked can be employed. With such a configuration, light can be emitted more efficiently.

The hole transport layer is made of a material having a function of transporting holes, and in a broad sense, a hole injection layer and an electron blocking layer are also included in the hole transport layer. The hole transport layer can be provided as a single layer or a plurality of layers.

The electron transport layer is made of a material having a function of transporting electrons, and in a broad sense, an electron injection layer and a hole blocking layer are also included in the electron transport layer. The electron transport layer can be provided as a single layer or a plurality of layers.

The hole blocking layer has a function of an electron transport layer in a broad sense, and is made of a hole blocking material having a function of transporting electrons but having a remarkably small ability to transport holes. By preventing this, the recombination probability between electrons and holes can be improved.

The hole injection layer and the electron injection layer are layers provided between the electrode and the light emitting layer in order to lower the driving voltage and improve the light emission luminance.

≪First electrode (30) ≫
The first electrode is an electrode opposite to the second electrode, and as a constituent material thereof, for example, a conductive transparent material having a transmittance of 40% or more such as CuI, ITO, SnO ₂ , ZnO, indium zinc oxide (IZO), etc. Can be used.

(Transparent electrode based on silver)
In the present invention, the first electrode may be a transparent electrode containing silver or an alloy containing silver as a main component.
The main component means a component having the highest component ratio among the components constituting the first electrode. The composition ratio is preferably 60% by mass or more, more preferably 90% by mass or more, and particularly preferably 98% by mass or more. Moreover, the transparency of the transparent electrode means that the light transmittance at a wavelength of 550 nm is 50% or more.

The first electrode may have a configuration in which silver or an alloy layer mainly containing silver is divided into a plurality of layers as necessary.
Furthermore, the first electrode preferably has a thickness in the range of 4 to 9 nm. When the thickness is less than 9 nm, the absorption component or reflection component of the layer is small, and the transmittance of the transparent electrode is increased. Further, when the thickness is thicker than 4 nm, sufficient conductivity of the layer can be ensured.

Examples of the alloy mainly composed of silver (Ag) constituting the first electrode include silver magnesium (AgMg), silver copper (AgCu), silver palladium (AgPd), silver palladium copper (AgPdCu), and silver indium (AgIn). ) And the like.

As a method for manufacturing such a first electrode, a method using a wet process such as a coating method, an ink jet method, a coating method, a dipping method, a vapor deposition method (resistance heating, EB method, etc.), a sputtering method, a CVD method, etc. Examples include a method using a dry process. Among these, the vapor deposition method is preferably applied.

≪Resin substrate (10) ≫
The resin substrate holds the entire organic EL element and transmits light.
As the resin substrate, for example, a transparent material such as a resin having a thickness in the range of 0.05 to 1 mm can be used. In the present invention, a resin substrate is preferably used. If a flexible film-like material such as a resin film is used as the substrate, continuous production is possible, and the production volume can be dramatically improved. In some cases, the surface light source can be curved and light can be emitted in various directions, so that an unprecedented light source can be created. Furthermore, the weight is light and the range of use is greatly expanded.

Examples of the resin film include polyesters such as polyethylene terephthalate (PET) and polyethylene naphthalate (PEN), polyethylene, polypropylene, cellophane, cellulose diacetate, cellulose triacetate (TAC), cellulose acetate butyrate, cellulose acetate propionate ( CAP), cellulose esters such as cellulose acetate phthalate, cellulose nitrate or derivatives thereof, polyvinylidene chloride, polyvinyl alcohol, polyethylene vinyl alcohol, syndiotactic polystyrene, polycarbonate, norbornene resin, polymethylpentene, polyether ketone, polyimide , Polyethersulfone (PES), polyphenylene sulfide, polysulfones Cycloolefin resins such as polyetherimide, polyetherketoneimide, polyamide, fluororesin, nylon, polymethylmethacrylate, acrylic or polyarylates, Arton (trade name, manufactured by JSR) or Appel (trade name, manufactured by Mitsui Chemicals) Etc. can be used.

As a resin substrate having flexibility, its tensile strength is in the range of 20 to 80 kg / mm ² , and the elastic modulus in an arbitrary direction parallel to the substrate surface is in the range of 1000 to 2500 kg / mm ² . It is preferable that the breaking elongation in an arbitrary direction parallel to the substrate surface is 5% or more.

A film made of an inorganic material, an organic material, or a hybrid thereof may be formed on the surface of the substrate. Such a film has a water vapor transmission rate (25 ± 0.5 ° C., relative humidity (90 ± 2)% RH) measured by a method according to JIS K 7129-1992 of 1 × 10 ⁻³ g / (M ² · 24h) The following is a gas barrier film, and the oxygen permeability measured by a method according to JIS K 7126-1987 is 1 × 10 ^-3 ml / (m ² · 24h · atm) or less, and water vapor permeability (25 ± 0.5 ° C., relative humidity (90 ± 2)% RH) is a high gas barrier film having 1 × 10 ⁻³ g / (m ² · 24 h) or less. Those are preferred.

As a material for forming a gas barrier film, any material having a function of suppressing the intrusion of moisture, oxygen, or the like that deteriorates the element may be used. For example, silicon oxide, silicon dioxide, silicon nitride, or the like can be used. . Furthermore, in order to improve the brittleness of the coating, it is more preferable to give the coating a laminated structure. The laminated structure can be formed, for example, by alternately laminating inorganic layers and organic layers a plurality of times.

Examples of a method for forming a gas barrier film include a vacuum deposition method, a sputtering method, a reactive sputtering method, a molecular beam epitaxy method, a cluster ion beam method, an ion plating method, a plasma polymerization method, and an atmospheric pressure plasma polymerization method. , Plasma CVD method, laser CVD method, thermal CVD method, coating method and the like.

The refractive index of the resin substrate is around 1.5.

≪Other composition≫
In order to efficiently extract light from the resin substrate into the air, a known lens sheet, prism sheet, or the like can be provided on the resin substrate.

≪Use of organic EL elements≫
As described above, the organic EL element is configured by laminating the first electrode, the organic functional layer, and the second electrode on the resin substrate. In the organic EL element, a part of the first electrode is exposed at one end, and a part of the second electrode is exposed at the other end to form an electrode part. By connecting to each power supply wiring (not shown) (not shown) and applying a predetermined DC voltage to the organic functional layer, light can be emitted.

Hereinafter, the present invention will be specifically described by way of examples, but the present invention is not limited thereto. In addition, although the display of "%" is used in an Example, unless otherwise indicated, "mass%" is represented.

[Example 1]
<< Production of organic EL elements >>
(1) Preparation of organic EL element 101 (1.1) Preparation of resin substrate As a substrate, a transparent PEN substrate of 60 mm × 80 mm × 0.125 mm was referred to Example 1 of JP2012-116101A, A gas barrier layer was formed.

Specifically, a UV curable organic product manufactured by JSR Corporation on one side of a polyethylene naphthalate film (made by Teijin DuPont Films Ltd., extremely low heat yield PEN Q83) having a width of 500 mm and a thickness of 125 μm that is easily bonded on both sides. / Inorganic hybrid hard coat material OPSTAR Z7535 was applied so that the layer thickness after application and drying was 4 μm, and then cured conditions: 1.0 J / cm ² , in an air atmosphere, using a high-pressure mercury lamp, drying conditions: 80 Curing was carried out at 3 ° C. for 3 minutes to form a bleed-out prevention layer.

Subsequently, a UV curable organic / inorganic hybrid hard coat material OPSTAR Z7501 manufactured by JSR Corporation is applied to the opposite surface of the resin substrate so that the layer thickness after application and drying is 4 μm, and then drying conditions; 80 After drying at 3 ° C. for 3 minutes, curing was carried out under an air atmosphere using a high-pressure mercury lamp, curing conditions: 1.0 J / cm ² to form a flat layer.
The maximum cross-sectional height Rt (p) of the obtained flat layer was 16 nm with a surface roughness specified by JIS B 0601.
The surface roughness was measured using an AFM (Atomic Force Microscope) SPI3800N DFM manufactured by SII. The measurement range for one time was 10 μm × 10 μm, the measurement location was changed, and the measurement was performed three times. The average of the Rt values obtained in each measurement was taken as the measurement value.

The thickness of the resin substrate produced as described above was 133 μm.

Next, the first gas barrier layer was applied to the surface of the flat layer of the resin substrate with a coating solution containing an inorganic precursor compound using a vacuum extrusion type coater so that the dry layer thickness was 150 nm. .
The coating solution containing the inorganic precursor compound is a non-catalytic perhydropolysilazane 20% by mass dibutyl ether solution (AZ Electronic Materials Co., Ltd. Aquamica NN120-20) and an amine catalyst containing 5% by mass solids. Hydropolysilazane 20% by weight dibutyl ether solution (Aquamica NAX120-20 manufactured by AZ Electronic Materials Co., Ltd.) was used in combination, and after adjusting the amine catalyst to 1% by weight of solid content, it was further diluted with dibutyl ether. This was prepared as a 5% by mass dibutyl ether solution.

After coating, the film was dried under conditions of a drying temperature of 80 ° C., a drying time of 300 seconds, and a dew point of 5 ° C. in a dry atmosphere.

After drying, the resin substrate was gradually cooled to 25 ° C., and the coating surface was subjected to modification treatment by irradiation with vacuum ultraviolet rays in a vacuum ultraviolet irradiation apparatus. As a light source of the vacuum ultraviolet irradiation device, an Xe excimer lamp having a double tube structure for irradiating vacuum ultraviolet rays of 172 nm was used.

<Modification processing equipment>
Excimer irradiation equipment MODEL: MECL-M-1-200, wavelength 172 nm, lamp filled gas Xe
<Reforming treatment conditions>
Excimer light intensity 3J / cm ² (172nm)
Stage heating temperature 100 ° C
Oxygen concentration in the irradiation device 1000ppm

After the modification treatment, the substrate on which the gas barrier layer was formed was dried in the same manner as described above, and further subjected to the second modification treatment under the same conditions to form a gas barrier layer having a dry layer thickness of 150 nm.

Subsequently, in the same manner as the first gas barrier layer, a second gas barrier layer was formed on the first gas barrier layer to produce a PEN substrate (film) having gas barrier properties.

The above PEN film with a gas barrier layer was cut to 60 mm × 80 mm, fixed to a Teflon (registered trademark) frame (equivalent to a tension of 100 N / m), and the following operation was performed.

(1.2) Production of first electrode The PEN substrate is fixed to a substrate holder of a commercially available vacuum deposition apparatus, the following compound 10 is placed in a resistance heating boat made of tantalum, and these substrate holder and heating boat are vacuum deposited. Attached to the first vacuum chamber of the apparatus. Moreover, silver (Ag) was put into the resistance heating boat made from tungsten, and it attached in the 2nd vacuum chamber.

In this state, first, the first vacuum chamber was depressurized to 4 × 10 ⁻⁴ Pa, and then heated by energizing the heating boat containing the compound 10, and the deposition rate was within the range of 0.1 to 0.2 nm / second. A base layer made of the compound 10 having a layer thickness of 25 nm was provided on the substrate.

Next, the substrate formed up to the base layer is transferred to the second vacuum chamber while being vacuumed, the second vacuum chamber is depressurized to 4 × 10 ⁻⁴ Pa, and then the heating boat containing silver is energized and heated, and the deposition rate is increased. An electrode layer made of silver having a thickness of 8 nm is formed on a substrate (underlying layer) within a range of 0.1 to 0.2 nm / second, and a first electrode having a laminated structure of the underlayer and the electrode layer is produced. did.

(1.3) Production of organic functional layer The resin substrate on which the first electrode was formed was fixed to a substrate holder of a commercially available vacuum deposition apparatus by overlapping with a mask having an opening with a width of 30 mm × 30 mm at the center. Moreover, each material which comprises an organic functional layer was filled with the optimal quantity for formation of each layer to each heating boat in a vacuum evaporation system.

The heating boat used was made of tungsten resistance heating material.

Next, the inside of the vapor deposition chamber of the vacuum vapor deposition apparatus was depressurized to a vacuum degree of 4 × 10 ⁻⁴ Pa, and each layer was formed as follows by sequentially energizing and heating the heating boat containing each material.

First, as a hole transport injecting material, a heating boat containing α-NPD represented by the following structural formula is energized and heated, and hole transport serving as both a hole injecting layer and a hole transporting layer made of α-NPD The injection layer was formed on the electrode layer constituting the first electrode. At this time, the deposition rate was 0.1 to 0.2 nm / second, and the layer thickness was 140 nm.

Next, each of the heating boat containing the host material H4 represented by the following structural formula and the heating boat containing the phosphorescent compound Ir-4 represented by the following structural formula were energized independently, respectively. A light emitting layer composed of the light emitting compound Ir-4 was formed on the hole transport injection layer. At this time, the energization of the heating boat was adjusted so that the deposition rate was the host material H4: phosphorescent compound Ir-4 = 100: 6. The layer thickness was 30 nm.

Next, a hole-blocking layer made of BAlq was formed on the light-emitting layer by heating by heating a heating boat containing BAlq represented by the following structural formula as a hole-blocking material. At this time, the deposition rate was 0.1 to 0.2 nm / second, and the layer thickness was 10 nm.

Thereafter, a heating boat containing tris (8-quinolinol) aluminum (Alq ₃ ) as an electron transporting material and a heating boat containing potassium fluoride are energized independently to each other, and consist of Alq ₃ and potassium fluoride. An electron transport layer was formed on the hole blocking layer. At this time, the energization of the heating boat was adjusted so that the deposition rate was Alq ₃ : potassium fluoride = 75: 25. The layer thickness was 30 nm.

Next, a heating boat containing potassium fluoride as an electron injection material was energized and heated to form an electron injection layer made of potassium fluoride on the electron transport layer. At this time, the deposition rate was 0.01 to 0.02 nm / second, and the layer thickness was 1 nm.

(1.4) Production and Sealing of Second Electrode Thereafter, the resin substrate formed up to the electron injection layer is placed in a vacuum state in a second vacuum chamber to which a resistance heating boat made of tungsten containing aluminum (Al) is attached. It was transferred while holding. It was fixed by overlapping with a mask having an opening with a width of 20 mm × 50 mm arranged so as to be orthogonal to the anode. Next, an organic EL element 101 was manufactured in the processing chamber by forming a reflective second electrode made of Al having a thickness of 100 nm at a film formation rate of 0.3 to 0.5 nm / second as a cathode.

Thereafter, the second electrode side of the organic EL element 101 was covered with an epoxy resin having a thickness of 300 μm, further covered with an aluminum foil having a thickness of 12 μm, and then cured and sealed. Sealing was performed in a glove box (in an atmosphere of high-purity nitrogen gas with a purity of 99.999% or more) in a nitrogen atmosphere without bringing the organic EL element 101 into contact with the atmosphere.

(2) Preparation of organic EL element 102 In the preparation of the organic EL element 101, an organic EL element was similarly formed except that a light scattering layer and a smoothing layer were formed between the substrate and the first electrode as follows. Element 102 was produced.

(2.1) Production of Light Scattering Layer TiO ₂ particles (JR600A manufactured by Teika Co., Ltd.) having a refractive index of 2.4 and an average particle size of 0.25 μm and a resin solution (ED230AL (organic / inorganic hybrid resin) manufactured by APM) The formulation was designed at a ratio of 10 ml so that the solid content ratio of the product was 70% by volume / 30% by volume and the solid content concentration in propylene glycol monomethyl ether (PGME) was 15% by mass.

Specifically, the above-mentioned TiO ₂ particles and a solvent are mixed and cooled at room temperature, and then the standard of the microchip step (SM-3 MSmm 3 mmφ) is applied to an ultrasonic disperser (SMH UH-50). Dispersion was added for 10 minutes under the conditions to prepare a TiO ₂ dispersion.
Next, while stirring the TiO ₂ dispersion at 100 rpm, the resin was mixed and added little by little. After the addition was completed, the stirring speed was increased to 500 rpm, and the mixture was mixed for 10 minutes, and then a hydrophobic PVDF 0.45 μm filter (manufactured by Whatman). The desired coating solution for light scattering layer was obtained.

After applying the coating solution on the PEN substrate by the ink jet coating method, it is simply dried (80 ° C., 2 minutes), and further subjected to a drying treatment for 5 minutes under an output condition of a substrate temperature of less than 80 ° C. by wavelength control IR described later. Executed.

Next, the curing reaction was promoted under the following modification treatment conditions to obtain a light scattering layer having a layer thickness of 0.3 μm.

<Modification processing equipment>
Excimer irradiation equipment MODEL: MEIRH-M-1-200-222-H-KM-G, wavelength 222 nm, lamp filled gas KrCl
<Reforming treatment conditions>
Excimer light intensity 2J / cm ² (222nm)
Stage heating temperature 60 ℃
Oxygen concentration in the irradiation device

(2.1) Preparation of smoothing layer Next, a high refractive index UV curable resin (manufactured by Toyo Ink Co., Ltd., Rioduras TYT90-01, nanosol particles: TiO ₂ ) was used as a smoothing layer coating solution. The solid content concentration in an organic solvent in which the solvent ratio of glycol monomethyl ether (PGME) and 2-methyl-2,4-pentanediol (PD) is 90% by mass / 10% by mass is 12% by mass. The formulation was designed at a ratio of 10 ml.

Specifically, the high refractive index UV curable resin and the solvent are mixed, mixed at 500 rpm for 1 minute, and then filtered through a hydrophobic PVDF 0.45 μm filter (manufactured by Whatman) for the intended smoothing layer. A coating solution was obtained.
After coating the coating solution on the light scattering layer by the inkjet coating method, simple drying (80 ° C., 2 minutes) was performed, and further, a drying process was performed for 5 minutes under an output condition with a substrate temperature of less than 80 ° C. by wavelength control IR. .

The drying process was performed by attaching two quartz glass plates that absorb infrared rays having a wavelength of 3.5 μm or more to an IR irradiation device (ultimate heater / carbon, manufactured by Meidyo Kogyo Co., Ltd.) using a wavelength-controlled infrared heater, and glass. Flowing cooling air between the plates).
At this time, the cooling air was set at 200 L / min, and the tube surface quartz glass temperature was suppressed to less than 120 ° C. The substrate temperature was measured by placing K thermocouples on the upper and lower surfaces of the substrate and 5 mm above the substrate and connecting them to NR2000 (manufactured by Keyence Corporation).

Next, the curing reaction was promoted under the following modification treatment conditions, a smoothing layer having a layer thickness of 0.7 μm was formed, and a light extraction layer having a two-layer structure of a light scattering layer and a smoothing layer was produced.

The refractive index of the smoothing layer single layer was 1.89.
The light extraction layer produced as described above had a transmittance T of 67% and a haze value Hz of 50%. In addition, a haze value is a haze value as a light extraction layer which laminated | stacked the smoothing layer on the light-scattering layer.
In addition, the refractive index at a wavelength of 550 nm of the entire light extraction layer was measured using a sopra ellipsometer based on D542, and found to be 1.88.

(3) Production of Organic EL Element 103 In production of the organic EL element 102, the solvent ratio of propylene glycol monomethyl ether and 2-methyl-2,4-pentanediol as the organic solvent of the smoothing layer coating solution is 70 mass. The organic EL element 103 was produced in the same manner except that an organic solvent of% / 30% by mass was used and the formulation was formulated at a ratio of 10 ml so that the solid content concentration was 12% by mass.

(4) Preparation of organic EL element 104 In the preparation of the organic EL element 102, the solvent ratio of propylene glycol monomethyl ether and 2-methyl-2,4-pentanediol as the organic solvent of the smoothing layer coating solution was 30 mass. The organic EL element 104 was produced in the same manner except that the organic solvent was% / 70% by mass and the formulation was designed in a ratio of 10 ml so that the solid content concentration was 12% by mass.

(5) Preparation of organic EL element 105 In the preparation of organic EL element 102, the organic solvent of the smoothing layer coating solution is only 2-methyl-2,4-pentanediol, so that the solid content concentration is 12% by mass. In addition, the organic EL element 105 was produced in the same manner except that the formulation was designed in a ratio of 10 ml.

(6) Preparation of organic EL element 106 In preparation of the organic EL element 102, the organic solvent of the smoothing layer coating solution is only 1,3-butanediol, and the amount of 10 ml is so that the solid content concentration is 12% by mass. The organic EL element 106 was produced in the same manner except that the prescription was designed at the ratio.

(7) Preparation of organic EL element 107 In preparation of organic EL element 102, the organic solvent of the coating solution for the smoothing layer is only 1,5-pentanediol, and the amount of 10 ml so that the solid content concentration is 12% by mass. The organic EL element 107 was produced in the same manner except that the prescription was designed at the ratio.

<< Evaluation of organic EL elements >>
(1) Discharge stability Using the inkjet drawing apparatus equipped with an inkjet head (“KM512L” manufactured by Konica Minolta Co., Ltd.), the prepared coating solution for the smoothing layer is formed on the substrate prepared by the inkjet coating method. The 3 cm × 3 cm pattern was continuously printed.
The drawing conditions of the ink jet coating method were an appropriate liquid amount of 40.0 ng by adjusting the applied voltage, a resolution of 360 dpi × 450 dpi, and single pass printing for each pattern film.
Prints up to 100 patterns in succession, observes the landed ink with an optical microscope (100 times), and the number of nozzles with missing nozzles and nozzle bending (landing position deviation) in all nozzles (512) Were evaluated according to the following evaluation criteria.
The evaluation results are shown in Table 1. In addition, the thing of the evaluation criteria 3 was set as the pass.

〔Evaluation criteria〕
3: No missing nozzle or bent nozzle.
2: No nozzle missing, but nozzle bending.
1: Nozzle missing.

(2) Density unevenness PEN film of 4cm x 8cm was cleaned with detergent and pure water using an ultrasonic cleaner, and then illuminated from a distance of 30mm using a UV-ozone cleaner with a low-pressure mercury lamp (UV wavelength: 254nm, 185nm). A substrate was obtained by performing UV irradiation at ² mW / cm ² for 10 minutes.
Using the inkjet drawing apparatus equipped with an inkjet head (“KM512L” manufactured by Konica Minolta Co., Ltd.), the prepared coating liquid for smoothing layer is ejected onto the prepared substrate by an inkjet application method, and evaluated. A pattern (3 cm × 3 cm, Wet film thickness 10 μm) was formed.
The drawing conditions of the ink jet coating method were an appropriate liquid amount of 40.0 ng by adjusting the applied voltage, a resolution of 360 dpi × 450 dpi, and single pass printing for each pattern film. The substrate temperature was maintained at 25 ° C. during printing. Immediately after printing by inkjet, it was dried for 10 minutes at an output of 100% (2 kW) using a wavelength control IR heater manufactured by NGK.
Density unevenness was visually evaluated according to the following evaluation criteria for the pattern recorded on the PEN film.
The evaluation results are shown in Table 1. In addition, the thing of the evaluation criteria 3 was set as the pass.

〔Evaluation criteria〕
3: Density unevenness is not visually confirmed, and has a high homogeneity.
2: Slight unevenness is seen in parallel with the scanning direction of the inkjet head.
1: Obvious stripes are seen, and repelling and pinholes are seen in some places.

(3) Film formability The film formability is an index representing the state when the coating liquid is applied on the substrate.
The coating film is preferably uniformly coated. When uneven coating, repelling, streaks, etc. occur, not only the original function of the light scattering layer is exhibited, but also the light emitting efficiency of the organic EL element itself decreases. May end up.
Then, about each produced organic EL element, the film-forming state of the smoothing layer was evaluated visually according to the following evaluation criteria.
The evaluation results are shown in Table 1. In addition, the thing of the evaluation criteria 3 was set as the pass.

〔Evaluation criteria〕
3: There is no coating failure such as uneven coating, repelling, and streaking.
2: There is a slight coating failure.
1: There is a coating failure that cannot withstand practical use.

(4) Luminous efficiency (power efficiency)
About each produced organic EL element, it lighted on the constant current density condition of ^2.5 mA / cm < ² > at room temperature (within the range of about 23-25 degreeC), and the spectral radiance meter CS-2000 (made by Konica Minolta) ) Was used to measure the light emission luminance of each element, and the light emission efficiency (power efficiency) at the current value was determined. The luminous efficiency is shown as a relative value where the luminous efficiency of the organic EL element 102 is 100.
The measurement results are shown in Table 1.

(5) Summary As is apparent from Table 1, the organic EL elements 103 to 106 of the present invention are more stable than the organic EL elements 101, 102, and 107 of the comparative examples in terms of ejection stability, density unevenness, It turns out that it is excellent in all of film forming property and the luminous efficiency of an organic EL element.
From the above, in the step of forming the smoothing layer, a step of preparing a coating liquid containing high refractive index nanosol particles, a binder, and an organic solvent and having a viscosity in the range of 3 to 30 mPa · s. A step of applying the coating solution by an inkjet coating method, a step of irradiating the coating solution after application with wavelength-control infrared rays and drying, and a step of irradiating the coating solution after drying with excimer light and curing. It has confirmed that the manufacturing method of the organic EL element which has was useful.

[Example 2]
<< Production of organic EL elements >>
(1) Preparation of organic EL element 201 In preparation of the organic EL element 102 of Example 1, a solvent is not added as a coating solution for the smoothing layer, and the solid content concentration remains at 20% by mass, and smoothing is performed by an inkjet coating method. An organic EL element 201 was produced in the same manner except that the layer coating solution was applied.

(2) Preparation of organic EL element 202 In preparation of the organic EL element 201, the organic solvent of the smoothing layer coating solution is only toluene, and the formulation is designed in a ratio of 10 ml so that the solid content concentration is 12% by mass. An organic EL element 202 was produced in the same manner except that.

(3) Preparation of organic EL element 203 In the preparation of the organic EL element 201, the organic solvent of the smoothing layer coating solution is only 2-butanol, and the solid content concentration is 12% by mass at a ratio of 10 ml. An organic EL device 203 was produced in the same manner except that the formulation was designed.

(4) Preparation of organic EL element 204 In preparation of the organic EL element 201, the organic solvent of the coating solution for the smoothing layer is only tetrahydrofurfuryl alcohol (THFA), and 10 ml so that the solid content concentration is 12% by mass. An organic EL element 204 was produced in the same manner except that the formulation was designed according to the ratio of the amounts.

(5) Preparation of organic EL element 205 In preparation of the organic EL element 201, the organic solvent of the smoothing layer coating solution is only 2-methyl-2,4-pentanediol (PD), and the solid content concentration is 12% by mass. Thus, an organic EL element 205 was produced in the same manner except that the formulation was designed at a ratio of 10 ml.

(6) Production of organic EL element 206 In production of the organic EL element 201, the organic solvent of the smoothing layer coating solution is only tetraethylene glycol, and the solid content concentration is 12% by mass in a ratio of 10 ml. An organic EL element 206 was produced in the same manner except that the formulation was designed.

(7) Preparation of organic EL element 207 In preparation of organic EL element 201, the organic solvent of the smoothing layer coating solution is only 1,3-butanediol, and the solid content concentration is 12% by mass. The organic EL element 207 was produced in the same manner except that the prescription was designed at the ratio.

(8) Production of organic EL element 208 In production of the organic EL element 201, the organic solvent of the smoothing layer coating solution is only 1,5-pentanediol, and the solid content concentration is 12% by mass. The organic EL element 208 was produced in the same manner except that the prescription was designed at the ratio.

(9) Production of Organic EL Element 209 In production of the organic EL element 201, the solvent ratio of propylene glycol monomethyl ether (PGME) and 1,5-pentanediol as the organic solvent of the smoothing layer coating solution is 50% by mass. An organic EL device 209 was produced in the same manner except that the organic solvent was / 50% by mass and the formulation was designed at a ratio of 10 ml so that the solid content concentration was 12% by mass.

<< Evaluation of organic EL elements >>
In the same manner as in Example 1, ejection stability in the smoothing layer, density unevenness, film formability, and light emission efficiency in the organic EL element were evaluated and measured.
The evaluation results are shown in Table 2.
The luminous efficiency is shown as a relative value where the luminous efficiency of the organic EL element 201 is 100.

(2) Summary As is clear from Table 2, the organic EL elements 204 to 207 and 209 of the present invention are more stable than the organic EL elements 201 to 203 and 208 of the comparative example in terms of ejection stability and concentration. It turns out that it is more excellent in all of nonuniformity, film-forming property, and the luminous efficiency of an organic EL element. In addition, the organic EL elements 204, 205, 207, and 209 have greatly improved luminous efficiency compared to the organic EL element 206.
From the above, it has been confirmed that the use of an organic solvent having a viscosity and vapor pressure within a certain range as the organic solvent contained in the smoothing layer is more useful for improving the light extraction efficiency.

The present invention provides a method for manufacturing a flexible organic EL element that reduces waveguide loss and improves light extraction efficiency without impairing light transmittance, and a coating liquid used in the manufacturing method. In particular, it can be suitably used.

DESCRIPTION OF SYMBOLS 10 Resin board | substrate 20 Light extraction layer 22 Light scattering layer 24 Smoothing layer 30 1st electrode 40 Organic functional layer 41 Hole injection layer 42 Hole transport layer 43 Light emitting layer 44 Electron transport layer 45 Electron injection layer 50 2nd electrode 100 Organic EL element 300 Organic EL element 302 Metal electrode 304 Organic functional layer 306 Transparent electrode 308

Transparent substrates

310a, 310b, 310c, 310d, 310e Light

Claims

A method for producing an organic electroluminescent element in which a light scattering layer, a smoothing layer, a first electrode, an organic functional layer, and a second electrode are sequentially laminated on a resin substrate,
Forming the light scattering layer on the resin substrate;
Forming the smoothing layer on the light scattering layer;
With
In the step of forming the smoothing layer,
A step of preparing a coating liquid containing high refractive index nanosol particles, a binder, and an organic solvent and having a viscosity in the range of 3 to 30 mPa · s;
Applying the coating solution by an ink jet coating method;
A step of irradiating the coating liquid after coating with a wavelength-controlled infrared ray and drying,
A step of irradiating and curing the coating liquid after drying with excimer light;
The manufacturing method of the organic electroluminescent element characterized by having.
2. The method for producing an organic electroluminescent element according to claim 1, wherein the viscosity of the organic solvent is in a range of 5 to 100 mPa · s.
3. The method of manufacturing an organic electroluminescent element according to claim 1, wherein the vapor pressure of the organic solvent is in a range of 1.0 to 1000 Pa.
A coating liquid comprising nanosol particles having a high refractive index, a binder, and an organic solvent, and having a viscosity in the range of 3 to 30 mPa · s.
The coating solution according to claim 4, wherein the viscosity of the organic solvent is in the range of 5 to 100 Pa · s.
6. The coating liquid according to claim 4, wherein the vapor pressure of the organic solvent is in a range of 1.0 to 1000 Pa.