JPH11317289A - Organic el element simulation method, simulation device, and organic el element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To correctly estimate a spectrum emitted to the outside in optional structure, and make element design for obtaining a desirable spectrum possible by constituting with a luminescent source having a metal surface on one surface and a plurality of optical film thicknesses, and performing the structure design for taking out light based on a luminescent spectrum obtained from a simulation model represented by the numerical formula. SOLUTION: Numerical expression I shows a layer having different refractive index of (q) kind on the metal surface side of a luminescent source and (p) kind on the opposite side and the whole associated wave ϕ[λ] comprising a reflecting wave ϕnm in incoming from an (n) layer to an (m) layer. [In formula I, λ is the wave length, p>1, q>=1, amplitude of each light ϕis represented by the specified expression.] Normalized modulation spectrum ρ[λ] obtained from the composite wave of each light is represented by a specified expression, and when a luminescent source spectrum is IPL[λ], spectrum IEL[λ] emitted to the outside from a (p) layer is represented by an expression II. Spectrum estimation with a simulation model is quantitative and precise, calculation of element constitution such as film thickness is made possible, and the dispersion of spectroscopic characteristics is reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an organic EL device using an organic compound, and more particularly, to an organic EL device capable of effectively extracting light emission and having little variation in light emission luminance.
The present invention relates to a simulation method and apparatus for providing an L element and an organic EL element.

[0002]

2. Description of the Related Art In recent years, organic EL devices have been actively studied. This is because a hole transporting material such as triphenyldiamine (TPD) is deposited on the hole injecting electrode to form a thin film, and a phosphor such as an aluminum quinolinol complex (Alq3) is laminated as a light emitting layer. It is an element having a basic structure in which a small metal electrode (electron injection electrode) is formed, and is attracting attention because a very high luminance of several hundreds to several 10,000 cd / m ² can be obtained at a voltage of about 10 V.

As described above, an organic EL device is an organic EL device having an electron injection electrode, an organic layer, a hole injection electrode, etc. on a substrate.
It has a basic structure in which an L structure is formed, and normally, emitted light is extracted from the substrate side via a hole injection electrode.

By the way, it is generally known that, in an organic EL device, the emission spectrum of a light-emitting species causes optical interference inside the device while being emitted, and is modulated. Therefore, even if the organic EL elements have the same light emitting material,
Different optical systems change the spectrum emitted to the outside and the intensity thereof.

[0005] The largest type of the optical modulation is as follows.
As disclosed in Japanese Patent Application Laid-Open No. 4-328295, interference is caused by light emitted forward and light emitted backward and reflected by a metal surface (electron injection electrode).
Since this effect can be expressed by a function determined by the distance between the light emitting point and the metal surface, an optical configuration for obtaining a desired modulation spectrum can be understood. However, when making more precise predictions, the error is large, which is still insufficient, and further requires parameters to be considered.

Further, Japanese Patent Application Laid-Open No. Hei 7-240277 has revealed a problem that reflected light at the glass / transparent electrode interface interferes to modulate light emitted from the organic EL element. However, in the same publication, in order to increase the emission intensity of a specific wavelength in a certain narrow range using optical modulation, the optical film thickness from the glass / transparent conductive film interface to the metal surface sandwiching the organic multilayer portion is required. It merely states that a specific value is required.

[0007] If there is a certain arbitrary optical system, it is difficult to examine in detail the spectral modulation unless it is possible to predict how much the signal will be modulated by interference other than the above-mentioned parameters. Optical design was difficult. Further, in the case of further complexity, for example, the influence of the case where more reflective interfaces exist other than the organic multilayer portion and the transparent conductive film is not considered, and there is no study on its use.

As described above, when the constituent film thickness of the organic EL element changes, the spectrum and luminance of light emitted to the outside change. In order to use it as a display device such as a display, it is desirable that variations in characteristics due to the display device be small. However, there has been no discussion as to how far the optical film thickness should be controlled. Therefore, it is difficult to reduce the variation, and it has been difficult to supply a uniform product.

[0009]

SUMMARY OF THE INVENTION An object of the present invention is to simply approximate reflected light other than those conventionally studied.
By providing a simulation method and apparatus of an organic EL element that accurately predicts a spectrum emitted from an organic EL element having a general arbitrary structure to the outside and enables element design to obtain a desired spectrum. is there.

It is another object of the present invention to provide a method and an apparatus for simulating an organic EL device capable of realizing a structure capable of extracting light efficiently even with a structure having many reflecting surfaces.

It is another object of the present invention to provide a method and an apparatus for simulating an organic EL device capable of realizing a device configuration capable of reducing optical variations.

Another object of the present invention is to provide an organic EL device having a device configuration capable of reducing optical variations based on the results of simulation.

[0013]

The present inventors have conducted various studies to establish an accurate simulation model.
As a technique for this, (1) the reflected light on the surface other than the metal surface is quantitatively considered. (2) Since the target device is a laminate having a difference in the refractive index of less than twice, only one reflection on a portion other than the metal surface is considered, and reflections of two or more times are ignored. (3) The light emitting surface is assumed to be localized, and then extended to a non-localized model.

That is, the present invention is achieved by the following constitutions. (1) A method of simulating an organic EL element having a metal surface on one surface, a light emitting source and a plurality of optical film thicknesses, the simulation model represented by the following (I) and the simulation model (I A) a method of simulating an organic EL element for designing a structure for extracting light from an emission spectrum obtained in the above step. (I) In an organic EL device having a q-type layer on the metal surface side of a light emitting source and a p-type layer having a different refractive index on the opposite side, a total synthetic wave Φ [λ] composed of a reflected wave Φnm at each interface To

[0015]

(Equation 23)

(Where λ is the wavelength, Φ nm is the reflected wave from the n-th layer to the m-th layer, p> 1, q ≧ 1. However, the p-layer is sufficient to not contribute to interference. When q = 1, the third term on the right side is set to 0. In addition, the inversion symbol attached to the subscript—that is, the invert symbol is a quantity related to the layer on the metal surface side from the light emitting point. The same applies to the following.) The light emitted forward from the light source and emitted without being reflected at the interface, and the light emitted backward from the light source, included in the total synthetic wave Φ [λ] And the combined wave Φ1 with the light emitted forward without being reflected at the other interface reflected by the metal surface and facing forward,

[0017]

(Equation 24)

(Where n _m : refractive index of m layer, Δ _m : m
Layer optical path length, r _mn : Amplitude reflectance when light wave is incident from m layer to n layer, Φ: Light wave amplitude, ρ: Square of light wave amplitude (energy), L: Optical path length, λ: Wavelength , D: film thickness,
n: represents a refractive index. The same shall apply hereinafter), which is included in the total synthetic wave Φ [λ], is emitted forward from the light-emitting source, is reflected at the interface of the t-th layer, and is then reflected by the metal surface to face the other interface. Light emitted without being reflected by

[0019]

(Equation 25)

And is included in the total synthetic wave Φ [λ].
Light emitted backward from the light emitting source, reflected at the interface of the t-th layer, and then emitted forward without being reflected at the other interface,

[0021]

(Equation 26)

Which is included in the total synthetic wave Φ [λ].
The light is emitted backward from the light source, reflected forward on the metal surface, and reflected at the t-th layer interface, and then further reflected on the metal surface forward toward the front without being reflected at other interfaces. Light

[0023]

[Equation 27]

Where, assuming that the amplitude reflectance on the metal surface is -k, the standardized modulation spectrum ρ [λ] obtained from the composite wave of each light is

[0025]

[Equation 28]

(Where * represents a complex number; the same applies hereinafter), and when the spectrum of the light emitting source is represented by IPL [λ], the light is emitted to the outside through the p-layer (glass substrate) under optical modulation. Spectrum IEL [λ]

[0027]

(Equation 29)

Simulation model represented by (2) The method for simulating an organic EL device according to the above (1), wherein in the simulation model (I), a luminosity coefficient is represented by θ [λ].

[0029]

[Equation 30]

A simulation method for an organic EL device for designing a structure for extracting light from the emission luminance obtained in the above. (3) The method for simulating an organic EL device according to the above (1) or (2), wherein in the simulation model (I), the light emission is a light emission layer having a constant thickness of de. Let η [x] be the recombination amount at point x, which is an arbitrary point in the graph, and let the intensity due to interference be ρ
When [x, λ] is used, the amount of recombination η [x] is replaced by the emission intensity distribution φ [x] to obtain an interference spectrum,

[0031]

(Equation 31)

The spectrum IEL [λ] emitted from the outside is expressed as

[0033]

(Equation 32)

And the luminance L is

[0035]

[Equation 33]

The organic EL according to the above (1) or (2)
Element simulation method. (4) A simulation device for an organic EL device having a metal surface on one surface and having a light emitting species and a plurality of optical film thicknesses, wherein a simulation model (I) represented by the following (I) is developed. An apparatus for simulating an organic EL device, comprising: a control program to be used; and an arithmetic unit controlled by the control program to calculate a light emission spectrum. (I) In an organic EL device having a q-type layer on the metal surface side and a p-type layer having a different refractive index on the opposite side, a total combined wave Φ [λ] composed of a reflected wave Φnm at each interface is

[0037]

(Equation 34)

(Where λ is the wavelength, Φ nm is the reflected wave from the n-th layer to the m-th layer, p> 1, q ≧ 1. However, the p-layer is sufficiently large so as not to contribute to interference. When q = 1, the third term on the right side is set to 0. In addition, the inversion symbol attached to the subscript—that is, the invert symbol is a quantity related to the layer on the metal surface side from the light emitting point. The same applies to the following.) The light emitted forward from the light source and emitted without being reflected at the interface, and the light emitted backward from the light source, included in the total synthetic wave Φ [λ] And the combined wave Φ1 with the light emitted forward without being reflected at the other interface reflected by the metal surface and facing forward,

[0039]

(Equation 35)

(Where, n _m : refractive index of m layer, Δ _m : m
Layer optical path length, r _mn : Amplitude reflectance when light wave is incident from m layer to n layer, Φ: Light wave amplitude, ρ: Square of light wave amplitude (energy), L: Optical path length, λ: Wavelength , D: film thickness,
n: represents a refractive index. The same shall apply hereinafter), which is included in the total synthetic wave Φ [λ], is emitted forward from the light-emitting source, is reflected at the interface of the t-th layer, and is then reflected by the metal surface to face the other interface. Light emitted without being reflected by

[0041]

[Equation 36]

Which is included in the total synthetic wave Φ [λ].
Light emitted backward from the light emitting source, reflected at the interface of the t-th layer, and then emitted forward without being reflected at the other interface,

[0043]

(37)

Which is included in the total synthetic wave Φ [λ].
The light is emitted backward from the light source, reflected forward on the metal surface, and reflected at the t-th layer interface, and then further reflected on the metal surface forward toward the front without being reflected at other interfaces. Light

[0045]

(38)

And the modulation spectrum ρ [λ] obtained from the combined wave of each light is

[0047]

[Equation 39]

(Where * represents a complex number; the same shall apply hereinafter), and when the spectrum of the light emitting source is represented by IPL [λ], the light is emitted to the outside through the p-layer (glass substrate) under optical modulation. Spectrum IEL [λ]

[0049]

(Equation 40)

Simulation model represented by (In the formula, n _m: refractive index of the m layers, delta _m: optical path length of m layers, r _mn:
Amplitude reflectance when a light wave enters the m-layer to the n-layer, Φ: amplitude of light wave, square of amplitude of ρ light wave (energy), L: optical path length, λ: wavelength, d: film thickness, n: refraction Represents the rate. (5) The simulation apparatus for an organic EL device according to (4), wherein in the simulation model (I), the visibility coefficient is represented by θ [λ].

[0051]

[Equation 41]

An organic EL element simulation apparatus for calculating the light emission luminance. (6) The simulation device for an organic EL device according to the above (4) or (5), wherein in the simulation model (I), the light emission is a light emission layer having a constant thickness of de. Let η [x] be the recombination amount at point x, which is an arbitrary point in the graph, and let the intensity due to interference be ρ
When [x, λ] is used, the amount of recombination η [x] is replaced by the emission intensity distribution φ [x] to obtain an interference spectrum,

[0053]

(Equation 42)

The spectrum IEL [λ] emitted from the outside is expressed as

[0055]

[Equation 43]

And the brightness L is

[0057]

[Equation 44]

A simulation device for an organic EL element represented by (7) Glass substrate (refractive index: n = 1.5 or less), hole injection electrode (refractive index: n = 1.8 to 2.1), and organic layer (refractive index: n = 1.7 to 2) .1) and the electron injection electrode (3
Reflectance in the wavelength range of 100 to 700 nm) and the optical thickness (nx thickness) of the hole injecting electrode and the organic layer is set to 1.9 x 200 nm or less, and the variation in brightness is set. An organic EL device having a value within ± 5%. (8) A glass substrate (refractive index: n = 1.5 or less), a buffer layer (refractive index: n = 1.8 to 2.1), and a hole injection electrode (refractive index: n = 1.8 to 2) .1), an organic layer (refractive index: n = 1.7 to 2.1), and an electron injection electrode (300).
(A reflectance of 50% or more in a wavelength range of 700 to 700 nm), and the total of the optical thicknesses (nx thickness) of the hole injection electrode, the buffer layer, and the organic layer is 1.9 x 700 nm or more. An organic EL device having a luminance variation within ± 5%.

[0059]

The logical expression, which is a simulation model of the present invention, is applied to an organic EL device having Alq ₃ as described later and compared with experimental values. As a result, both the emission spectrum and the luminance agree well with the experimental values. Thus, it has become possible to predict the spectrum quantitatively and precisely. Further, even in a complicated case where there are many reflecting surfaces, an efficient light extraction structure can be determined.

Further, based on the simulation results obtained above, an element configuration for suppressing the dispersion of spectroscopic characteristics due to the film thickness of the element was calculated. For example, in the case of an organic EL device, a layer having a sufficiently long optical path (500 nm or more) is provided between the glass and the metal surface,
It has been found that it is sufficient to keep the thickness within about 10 nm.

[0061]

BEST MODE FOR CARRYING OUT THE INVENTION The method for simulating an organic EL device according to the present invention is a method for simulating an organic EL device having a metal surface on one surface and having a light emitting source and a plurality of optical film thicknesses. The structure design for efficient light extraction is performed from the simulation model represented by I) and the emission spectrum obtained from the simulation model (I).

(I) For example, as shown in FIG. 1, in an organic EL device having a q-type layer on the metal surface side and a p-type layer having a different refractive index on the metal surface side, reflected waves at each interface are

[0063]

[Equation 45]

(Where λ is the wavelength, Φ nm is the reflected wave from the n-th layer to the m-th layer, p> 1, q ≧ 1. However, the p-layer is sufficiently large so as not to contribute to the interference. When q = 1, the third term on the right side is set to 0. In addition, the inversion symbol attached to the subscript—that is, the invert symbol is a quantity related to the layer on the metal surface side from the light emitting point. The light emitted from the light emitting source forward and emitted without being reflected at the interface, and the light emitted from the light emitting source backward, reflected by the metal surface, and directed forward. Light emitted without being reflected at the interface,

[0065]

[Equation 46]

(Where, n _m : refractive index of m layer, Δ _m : m
Layer optical path length, r _mn : Amplitude reflectance when light wave is incident from m layer to n layer, Φ: Light wave amplitude, ρ: Square of light wave amplitude (energy), L: Optical path length, λ: Wavelength , D: film thickness,
n: represents a refractive index. Hereinafter, the same applies), light emitted forward from the light emitting source, reflected at the interface of the t-th layer, then reflected forward on the metal surface and emitted without being reflected at the other interface,

[0067]

[Equation 47]

The light emitted backward from the light emitting source, reflected at the interface of the t-th layer, and then emitted forward without being reflected at the other interface,

[0069]

[Equation 48]

The light is emitted backward from the light-emitting source, reflected on the metal surface, and travels forward. After being reflected on the interface of the t-th layer, it is further reflected on the metal surface and travels forward and reflected on another interface. The light emitted without being

[0071]

[Equation 49]

Where the amplitude reflectance on the metal surface is -k, and the modulation spectrum ρ obtained from the composite wave of each light is
[λ]

[0073]

[Equation 50]

(Where * represents a complex number; the same applies hereinafter), and when the spectrum of the light emitting source is represented by IPL [λ], p
The spectrum IEL [λ] emitted outside through the layer (glass substrate)

[0075]

(Equation 51)

This is a simulation model expressed as follows.

Using such a simulation model, the direct emission light from the light emitting source, which has been considered so far,
In addition to the reflected light emitted through the metal surface, a simulation can be performed in consideration of reflection at a plurality of interfaces having different refractive indices, and the modulation spectrum intensity can be obtained relatively easily. Further, in the above simulation model, only the reflected light once is considered, and the combined light wave Φ [λ] considering the reflected light at all interfaces is obtained by simply superimposing them. As a result, the model is simplified, and an accurate approximate model can be obtained relatively easily without performing complicated calculations. Therefore, in the above simulation model, terms including the second or higher order of r are sufficiently smaller than 1 and are ignored, and a conversion formula between an exponential function and a trigonometric function is also used.

Further, when the visibility coefficient is represented by θ [λ],

[0079]

(Equation 52)

The structure design for efficient light extraction can be performed from the emission luminance obtained as described above.

In the above simulation model,
The luminescent source was treated as a point source without spread. Therefore, for further generalization, consider a case where the light emitting region has a distribution. In an organic EL element, generally, a light emitting source can be regarded as a set of point light sources that are not related to each other.
Therefore, it is understood that the above localization models may be simply superimposed.

[0082] However, in order to extend the model naturally, for example as shown in FIG. 2, considering the light-emitting layer having a constant thickness d _e, emitting up and down across the localized emission a region d1 + d1 (In this paragraph, -1 represents an invert in which-is added above 1). Assuming that both refractive indices are n1 = n-1, d1 or d-1 (either has an arbitrary spread from 0 to de)
Can be considered that localized light emission of 0 to de is superimposed.

Here, it is assumed that the light emission intensity of the point light source changes at a place, but its spectrum (such as a fluorescence spectrum in the case of an organic EL element) is the same at the light emission point. For example, in the case of an organic EL device, the emission intensity is proportional to the amount of recombination of electrons and holes. Although the amount of recombination has a distribution in the device, the spectrum itself is the same as the fluorescence spectrum of the material or the like and does not depend on the location. In order to obtain an interference spectrum under such conditions, the recombination amount η [x] at an arbitrary point x in the device must be known. Since the light emitted from the point x has an intensity of ρ [x, λ] due to interference, the interference spectrum Γ [λ] can be obtained by multiplying η [x] by ρ [x, λ] and integrating over x over the emission region. ] Will be obtained. Since the amount of recombination of electrons and holes is proportional to the emission intensity as described above, the amount of recombination η [x] is replaced by the emission intensity distribution φ [x] here.

[0084]

(Equation 53)

As described above, since n1 = n−1 (in this paragraph, −1 represents an invert with a − above 1), and d1 + d−1 = de, the end of the light emitting layer Is set to 0, the integral becomes d-1 = 0 to de.

[0086]

(Equation 54)

Therefore, the spectrum emitted to the outside is

[0088]

[Equation 55]

The emission luminance is

[0090]

[Equation 56]

Is obtained.

In the above examination, the spectrum of the light emitting point source (fluorescent spectrum of the organic EL) is the same at the light emitting point. However, if the light emitting point is different, the above equation is modified.

The emission intensity of the organic EL element at a distance of d-1 from the end of the light emitting region (electron injection electrode side = 0) is represented by IPL [d
−1, λ], IEL [λ] becomes the following integral expression (in this paragraph, −1 represents an invert in which − is added to 1).

[0094]

[Equation 57]

Further, assuming that the visibility coefficient is θ, the luminance L
Is as follows.

[0096]

[Equation 58]

Further, the simulation model (1) used in the method of the present invention is developed on a program as a part of a control algorithm, and the calculation means executes the simulation model, thereby obtaining a light emission spectrum and light emission luminance. It may be.

A program for developing the above simulation model is available in any high-level or low-level language such as assembler, C language, Fortran, or BASIC.
Any language can be used as long as the simulation model can be developed. The expanding means may apply a commonly used method for expanding mathematical formulas.

As a medium for storing the program, in addition to a semiconductor memory such as a ROM, a RAM and a flash memory, a magnetic recording medium such as an FD and an HD, a CD and a C
An optical recording medium such as a DROM can be used.

Examples of the operation means include a microprocessor capable of directly accessing and operating a semiconductor memory or the like in which a program is stored, and a personal computer to which the operation is applied. Can be displayed on a display or a printer. Input of parameters and the like may be input via a keyboard, an external connection bus, communication means, or the like. Therefore,
For example, the apparatus of the present invention can be realized by inputting a program in which the above simulation model is developed into a general-purpose personal computer, workstation, or the like.

Next, the organic EL element analyzed by the simulation of the present invention will be described. The organic EL device used in the present invention has, for example, a hole injection electrode, an electron injection electrode, and one or more organic layers provided between these electrodes on a substrate. The organic layer may have at least one hole transport layer and at least one light emitting layer, an electron injection electrode thereon, and a protective electrode as the uppermost layer. Note that the hole transport layer can be omitted. The electron injection electrode is made of a metal, a compound or an alloy having a small work function, which is preferably formed by vapor deposition, sputtering, or the like, preferably by sputtering. Further, a so-called reverse lamination in which the electron injection electrode is formed on the substrate side may be employed.

The hole injecting electrode usually has a structure in which light emitted from the substrate side is taken out. Therefore, a transparent electrode is preferable, and ITO (tin-doped indium oxide), IZO
(Zinc-doped indium oxide), ZnO, SnO ₂ , I
Examples include n ₂ O ₃ , and preferably ITO (tin-doped indium oxide) and IZO (zinc-doped indium oxide). The mixing ratio of SnO ₂ with respect to In ₂ O ₃ is preferably 1 to 20 wt%, more preferably 5~12wt%. The mixing ratio of ZnO to In ₂ O ₃ is 12 to
32 wt% is preferred. In addition, Sn, Ti, Pb, and the like may be contained in the form of oxides in an amount of 1% by weight or less in terms of oxides.

The hole injection electrode can be formed by a vapor deposition method or the like, but is preferably formed by a sputtering method. When a sputtering method is used for forming the ITO or IZO electrode, a target in which Sn ₂ or ZnO is doped into In ₂ O ₃ is preferably used. IT by sputtering method
When the O-transparent electrode is formed, the change in emission luminance with time is less than that of the film formed by vapor deposition. The sputtering method is D
C sputtering is preferred, and the input power is preferably in the range of 0.1 to 4 W / cm ² . In particular, the power of the DC sputtering apparatus is preferably 0.1 to 10 W
/ Cm ² , especially in the range of 0.2 to 5 W / cm ² . The deposition rate is 2 to 100 nm / min, especially 5 to 50 nm / min.
Is preferable.

The sputtering gas is not particularly limited, and an inert gas such as Ar, He, Ne, Kr, and Xe, or a mixed gas thereof may be used. As the pressure at the time of sputtering such a sputtering gas,
Usually, it may be about 0.1 to 20 Pa.

The thickness of the hole injecting electrode may be a certain thickness or more for sufficiently injecting holes.
0 nm, preferably in the range of 10 to 300 nm.

As a constituent material of the electron injecting electrode to be formed, a material having a low work function for effectively injecting electrons is preferable. Therefore, such a metal or alloy constituting an electron injection electrode is usually used as a sputter target. These work functions are 4.5 eV or less, and metals and alloys having a work function of 4.0 eV or less are particularly preferable.

The pressure of the sputtering gas at the time of sputtering is preferably in the range of 0.1 to 5 Pa. By adjusting the pressure of the sputtering gas in this range, the Li gas in the above range can be obtained.
A high concentration of AlLi alloy can be easily obtained. Also,
By changing the pressure of the sputtering gas within the above range during the film formation, an electron injection electrode having the above-mentioned Li concentration gradient can be easily obtained. Further, it is preferable that the film formation conditions satisfy a product of the film formation gas pressure and the distance between the substrate targets that satisfies 20 to 65 Pa · cm.

The sputter gas may be an inert gas used in a normal sputtering apparatus or a reactive gas such as N ₂ , H ₂ , O ₂ , C ₂ H ₄ , NH _{3 in the case} of reactive sputtering. Can be used.

As the sputtering method, a high-frequency sputtering method using an RF power supply or the like is possible. However, the DC sputtering method is used in order to easily control the film formation rate and to reduce damage to the organic EL element structure. Preferably, it is used. D
The power of the C sputtering apparatus is preferably 0.1 to 1
0 W / cm ^2, in particular from 0.5~7W / cm ^2. The film formation rate is 5 to 100 nm / min, especially 10 to 50 nm.
The range of nm / min is preferred.

The thickness of the electron-injection electrode thin film may be a certain thickness or more for sufficiently injecting electrons, and may be 1 nm or more, preferably 3 nm or more. The upper limit is not particularly limited, but the thickness may be generally about 3 to 500 nm.

In the organic EL device used in the present invention, a protective electrode may be provided on the electron injection electrode, that is, on the side opposite to the organic layer. By providing the protective electrode, the electron injection electrode is protected from the outside air, moisture, and the like, the deterioration of the constituent thin film is prevented, the electron injection efficiency is stabilized, and the element life is dramatically improved. The protection electrode has a very low resistance, and also has a function as a wiring electrode when the resistance of the electron injection electrode is high. The protective electrode preferably contains one or more of Al, Al and a transition metal (excluding Ti), Ti or titanium nitride (TiN).

The thickness of the protective electrode may be a certain thickness or more, preferably 50 nm or more, more preferably 100 nm or more, especially 100 nm, in order to secure electron injection efficiency and prevent entry of moisture, oxygen or an organic solvent. A range of ~ 1000 nm is preferred. If the protective electrode layer is too thin, the effect of the present invention cannot be obtained, and the step coverage of the protective electrode layer will be low, and the connection with the terminal electrode will not be sufficient. On the other hand, if the thickness of the protective electrode layer is too large, the stress of the protective electrode layer increases, and the dark spot growth rate increases. The thickness when functioning as a wiring electrode is
Since the thickness of the electron injection electrode is small, the film resistance is high. To compensate for this, the thickness is usually about 100 to 500 nm, and when it functions as another wiring electrode, it is about 100 to 300 nm.

The total thickness of the electron injecting electrode and the protective electrode is not particularly limited, but is usually 100 to 100.
It may be about 0 nm.

After forming the electrode, in addition to the protective electrode, S
inorganic materials iO _X such as Teflon, a protective film may be formed using an organic material such as fluorocarbon polymers containing chlorine. The protective film may be transparent or opaque, and the thickness of the protective film is about 50 to 1200 nm. The protective film may be formed by a general sputtering method, a vapor deposition method, a PECVD method or the like in addition to the reactive sputtering method described above.

Next, the organic layer provided in the EL device of the present invention will be described.

The light emitting layer has a function of injecting holes (holes) and electrons, a function of transporting them, and a function of generating excitons by recombination of holes and electrons. It is preferable to use a relatively electronically neutral compound for the light emitting layer.

The hole injecting / transporting layer has a function of facilitating the injection of holes from the hole injecting electrode, a function of stably transporting holes, and a function of hindering electrons. These layers have the function of facilitating the injection of electrons, the function of stably transporting electrons, and the function of hindering holes. These layers increase and confine holes and electrons injected into the light emitting layer, and reduce the recombination region. Optimize and improve luminous efficiency.

The thickness of the light emitting layer, the thickness of the hole injecting and transporting layer, and the thickness of the electron injecting and transporting layer are not particularly limited, and vary depending on the forming method.
The thickness is preferably from 0 to 300 nm.

The thickness of the hole injecting / transporting layer and the thickness of the electron injecting / transporting layer depend on the design of the recombination / light emitting region, but may be about the same as the thickness of the light emitting layer or about 1/10 to 10 times. When the injection layer and the transport layer for holes or electrons are separated from each other, it is preferable that the injection layer has a thickness of 1 nm or more and the transport layer has a thickness of 1 nm or more. At this time, the upper limit of the thickness of the injection layer and the transport layer is usually about 500 nm for the injection layer and 50 nm for the transport layer.
It is about 0 nm. Such a film thickness is the same when two injection / transport layers are provided.

The light emitting layer of the organic EL device of the present invention contains a fluorescent substance which is a compound having a light emitting function. Examples of such a fluorescent substance include, for example, JP-A-63-26.
No. 4,692, for example, at least one compound selected from compounds such as quinacridone, rubrene, styryl dyes and the like. Also, quinoline derivatives such as metal complex dyes having 8-quinolinol or a derivative thereof as a ligand, such as tris (8-quinolinolato) aluminum, tetraphenylbutadiene, anthracene, perylene, coronene, and 12-phthaloperinone derivatives. Further, Japanese Patent Application Laid-Open No. 8-12600
Phenylanthracene derivative disclosed in Japanese Patent Application Laid-open No. Hei 8-110569 (Japanese Patent Application No. Hei 6-110569).
No. 114456) can be used.

Further, it is preferable to use in combination with a host substance capable of emitting light by itself, and it is preferable to use it as a dopant. In such a case, the content of the compound in the light emitting layer is 0.01 to 10% by weight, and more preferably 0.1 to 10% by weight.
It is preferably 1 to 5% by weight. When used in combination with a host substance, the emission wavelength characteristics of the host substance can be changed, light emission shifted to a longer wavelength becomes possible, and the luminous efficiency and stability of the device are improved.

As the host substance, a quinolinolato complex is preferable, and an aluminum complex having 8-quinolinol or a derivative thereof as a ligand is preferable. Such an aluminum complex is disclosed in JP-A-63-26469.
No. 2, JP-A-3-255190, JP-A-5-7073
3, JP-A-5-258859, JP-A-6-2158
No. 74 and the like.

Specifically, first, tris (8-quinolinolato) aluminum, bis (8-quinolinolato) magnesium, bis (benzo {f} -8-quinolinolato) zinc, bis (2-methyl-8-quinolinolato) aluminum Oxide, tris (8-quinolinolato) indium,
Tris (5-methyl-8-quinolinolato) aluminum, 8-quinolinolatolithium, tris (5-chloro-
8-quinolinolato) gallium, bis (5-chloro-8-
Quinolinolato) calcium, 5,7-dichloro-8-quinolinolatoaluminum, tris (5,7-dibromo-
8-hydroxyquinolinolato) aluminum, poly [zinc (II) -bis (8-hydroxy-5-quinolinyl) methane], and the like.

Further, in addition to 8-quinolinol or its derivative, an aluminum complex having another ligand may be used, such as bis (2-methyl-
8-quinolinolato) (phenolato) aluminum (III)
, Bis (2-methyl-8-quinolinolato) (ortho-
Cresolato) aluminum (III), bis (2-methyl-
8-quinolinolato) (meth-cresolate) aluminum
(III), bis (2-methyl-8-quinolinolato) (para-cresolato) aluminum (III), bis (2-methyl-8-quinolinolato) (ortho-phenylphenolate)
Aluminum (III), bis (2-methyl-8-quinolinolato) (meth-phenylphenolato) aluminum (II
I), bis (2-methyl-8-quinolinolato) (para-
Phenylphenolato) aluminum (III), bis (2-
Methyl-8-quinolinolato) (2,3-dimethylphenolato) aluminum (III), bis (2-methyl-8-quinolinolato) (2,6-dimethylphenolato) aluminum (III), bis (2-methyl- 8-quinolinolato)
(3,4-dimethylphenolato) aluminum (III),
Bis (2-methyl-8-quinolinolato) (3,5-dimethylphenolato) aluminum (III), bis (2-methyl-8-quinolinolato) (3,5-di-tert-butylphenolato) aluminum (III) ), Bis (2-methyl-8)
-Quinolinolato) (2,6-diphenylphenolato) aluminum (III), bis (2-methyl-8-quinolinolato) (2,4,6-triphenylphenolato) aluminum (III), bis (2-methyl- 8-quinolinolato)
(2,3,6-trimethylphenolato) aluminum (I
II), bis (2-methyl-8-quinolinolato) (2,
3,5,6-tetramethylphenolato) aluminum (I
II), bis (2-methyl-8-quinolinolato) (1-naphthrat) aluminum (III), bis (2-methyl-8
-Quinolinolato) (2-naphthrat) aluminum (II
I), bis (2,4-dimethyl-8-quinolinolato)
(Ortho-phenylphenolato) aluminum (III),
Bis (2,4-dimethyl-8-quinolinolato) (para-
Phenylphenolato) aluminum (III), bis (2,
4-dimethyl-8-quinolinolato) (meta-phenylphenolato) aluminum (III), bis (2,4-dimethyl-8-quinolinolato) (3,5-dimethylphenolato) aluminum (III), bis (2 4-dimethyl-8
-Quinolinolato) (3,5-di-tert-butylphenolato) aluminum (III), bis (2-methyl-4-ethyl-8-quinolinolato) (para-cresolato) aluminum (III), bis (2-methyl) -4-methoxy-8-quinolinolato) (para-phenylphenolato) aluminum (III), bis (2-methyl-5-cyano-8-quinolinolato) (ortho-cresolato) aluminum (III),
Bis (2-methyl-6-trifluoromethyl-8-quinolinolato) (2-naphthrat) aluminum (III);

In addition, bis (2-methyl-8-quinolinolato) aluminum (III) -μ-oxo-bis (2-
Methyl-8-quinolinolato) aluminum (III), bis (2,4-dimethyl-8-quinolinolato) aluminum
(III) -μ-oxo-bis (2,4-dimethyl-8-quinolinolato) aluminum (III), bis (4-ethyl-
2-methyl-8-quinolinolato) aluminum (III)-
μ-oxo-bis (4-ethyl-2-methyl-8-quinolinolato) aluminum (III), bis (2-methyl-4
-Methoxyquinolinolato) aluminum (III) -μ-oxo-bis (2-methyl-4-methoxyquinolinolato)
Aluminum (III), bis (5-cyano-2-methyl-
8-quinolinolato) aluminum (III) -μ-oxo-
Bis (5-cyano-2-methyl-8-quinolinolato) aluminum (III), bis (2-methyl-5-trifluoromethyl-8-quinolinolato) aluminum (III) -μ
-Oxo-bis (2-methyl-5-trifluoromethyl-8-quinolinolato) aluminum (III) and the like.

Other host materials include those disclosed in
Phenylanthracene derivative described in JP-A-12600 (Japanese Patent Application No. 6-110569) and JP-A-8-1296
No. 9 (Japanese Patent Application No. 6-114456) is also preferable.

The light emitting layer may also serve as an electron injection / transport layer. In such a case, it is preferable to use tris (8-quinolinolato) aluminum or the like. These fluorescent substances may be deposited.

Further, if necessary, the light emitting layer is preferably a mixed layer of at least one or more hole injecting and transporting compounds and at least one or more electron injecting and transporting compounds. It is preferable to include them. The content of the compound in such a mixed layer is
It is preferably 0.01 to 20% by weight, more preferably 0.1 to 15% by weight.

In the mixed layer, a hopping conduction path of carriers is formed, so that each carrier moves in a material having a polarity predominant, carrier injection of the opposite polarity is less likely to occur, and organic compounds are less likely to be damaged. There is an advantage that the device life is extended, but by including the above-mentioned dopant in such a mixed layer, the emission wavelength characteristic of the mixed layer itself can be changed, and the emission wavelength can be shifted to a longer wavelength. In addition, the emission intensity can be increased and the stability of the element can be improved.

The hole injecting / transporting compound and the electron injecting / transporting compound used in the mixed layer may be selected from a compound for a hole injecting / transporting layer and a compound for an electron injecting / transporting layer, respectively, which will be described later. Among them, compounds for the hole injection transport layer include amine derivatives having strong fluorescence,
For example, it is preferable to use a triphenyldiamine derivative which is a hole transport material, a styrylamine derivative, or an amine derivative having an aromatic condensed ring.

As the compound capable of injecting and transporting electrons, it is preferable to use a quinoline derivative, furthermore a metal complex having 8-quinolinol or a derivative thereof as a ligand, particularly tris (8-quinolinolato) aluminum (Alq3). It is also preferable to use the above-mentioned phenylanthracene derivatives and tetraarylethene derivatives.

As the compound for the hole injecting and transporting layer, an amine derivative having strong fluorescence, for example, a triphenyldiamine derivative as the above hole transporting material, a styrylamine derivative, or an amine derivative having an aromatic condensed ring is used. Is preferred.

The mixing ratio in this case is determined by considering the respective carrier mobilities and carrier concentrations. In general, the weight ratio of the compound of the hole injecting / transporting compound to the compound having the electron injecting / transporting function is used. But 1 / 99-99 /
1, further from 10/90 to 90/10, especially 20/8
It is preferable to set it to about 0 to 80/20.

Further, the thickness of the mixed layer is preferably smaller than the thickness of the organic compound layer from the thickness corresponding to one molecular layer, more preferably 1 to 85 nm.
Further, the thickness is preferably 5 to 60 nm, particularly preferably 5 to 50 nm.

As a method for forming the mixed layer, co-evaporation in which evaporation is performed from different evaporation sources is preferable. However, when the vapor pressures (evaporation temperatures) are approximately the same or very close, they are mixed in advance in the same evaporation board. Alternatively, it can be deposited. In the mixed layer, it is preferable that the compounds are uniformly mixed, but in some cases, the compounds may exist in an island shape. The light-emitting layer is generally formed to a predetermined thickness by vapor-depositing an organic fluorescent substance or by dispersing and coating the resin in a resin binder.

The hole injecting and transporting layer is described in, for example, JP-A-63-295695 and JP-A-2-19169.
4, JP-A-3-792, JP-A-5-234
681, JP-A-5-239455, JP-A-5-299174, JP-A-7-126225, JP-A-7-126226, JP-A-8-100
Various organic compounds described in JP-A-172, EP0650955A1, and the like can be used. For example, a tetraarylbendicine compound (triaryldiamine or triphenyldiamine: TPD), an aromatic tertiary amine, a hydrazone derivative, a carbazole derivative, a triazole derivative, an imidazole derivative, an oxadiazole derivative having an amino group, polythiophene, etc. . Two or more of these compounds may be used in combination, and when they are used in combination, they may be stacked as separate layers or mixed.

When the hole injecting and transporting layer is provided separately as a hole injecting and transporting layer, a preferred combination can be selected from the compounds for the hole injecting and transporting layer. At this time, it is preferable to stack the layers of the compound having the smaller ionization potential in order from the hole injection electrode (ITO or the like) side. It is preferable to use a compound having a good thin film property on the surface of the positive electrode. Such a stacking order is the same when two or more hole injection transport layers are provided. With such a stacking order, the driving voltage is reduced, and the occurrence of current leakage and the occurrence and growth of dark spots can be prevented. In the case of deviceization, a thin film of about 1 to 10 nm is used because evaporation is used,
Even if a compound with low ionization potential and absorption in the visible region is used for the hole injection layer because it can be made uniform and pinhole-free, it is possible to prevent a change in color tone of the emission color and a decrease in efficiency due to reabsorption. Can be. The hole injecting and transporting layer can be formed by vapor deposition of the above compound in the same manner as the light emitting layer and the like.

The electron injecting and transporting layer, which is provided as necessary, is provided with a quinoline derivative such as an organometallic complex having 8-quinolinol or a derivative thereof such as tris (8-quinolinolato) aluminum (Alq3) as a ligand. Oxadiazole derivatives, perylene derivatives, pyridine derivatives, pyrimidine derivatives, quinoxaline derivatives, diphenylquinone derivatives, nitro-substituted fluorene derivatives, and the like. The electron injection / transport layer may also serve as the light emitting layer. In such a case, it is preferable to use tris (8-quinolinolato) aluminum or the like. The electron injecting and transporting layer may be formed by vapor deposition or the like, similarly to the light emitting layer.

When the electron injecting and transporting layer is divided into an electron injecting layer and an electron transporting layer, a preferable combination can be selected from the compounds for the electron injecting and transporting layer. At this time, it is preferable to stack the compounds in descending order of the electron affinity value from the electron injection electrode side. This stacking order is the same when two or more electron injection / transport layers are provided.

The luminescent color may be controlled by using a color filter film, a color conversion film containing a fluorescent substance, or a dielectric reflection film on the substrate.

As the color filter film, a color filter used in a liquid crystal display or the like may be used.
The characteristics of the color filter may be adjusted in accordance with the light emitted from the organic EL to optimize the extraction efficiency and the color purity.

When a color filter capable of cutting off short-wavelength external light that is absorbed by the EL element material or the fluorescent conversion layer is used, the light resistance of the element and the display contrast are improved.

In addition, an optical thin film such as a dielectric multilayer film may be used instead of the color filter.

The fluorescence conversion filter film absorbs EL light and emits light from the phosphor in the fluorescence conversion film, thereby performing color conversion of emission color. It is formed from a fluorescent material and a light absorbing material.

As the fluorescent material, basically, a material having a high fluorescence quantum yield may be used, and it is desirable that the fluorescent material has strong absorption in the EL emission wavelength region. Actually, laser dyes are suitable, and rhodamine compounds, perylene compounds, cyanine compounds, phthalocyanine compounds (including subphthalo, etc.) naphthaloimide compounds, condensed ring hydrocarbon compounds, condensed heterocyclic compounds, A styryl compound, a coumarin compound, or the like may be used.

As the binder, basically, a material which does not extinguish the fluorescence may be selected, and a binder which can be finely patterned by photolithography, printing or the like is preferable.
Further, a material that does not suffer damage during the formation of ITO or IZO is preferable.

The light absorbing material is used when the light absorption of the fluorescent material is insufficient, but may be omitted when unnecessary. As the light absorbing material, a material that does not quench the fluorescence of the fluorescent material may be selected.

For forming the hole injecting and transporting layer, the light emitting layer and the electron injecting and transporting layer, it is preferable to use a vacuum evaporation method since a uniform thin film can be formed. When the vacuum deposition method is used, the amorphous state or the crystal grain size is 0.2 μm,
In particular, a homogeneous thin film of 0.1 μm or less can be obtained. If the crystal grain size exceeds 0.2 μm, especially 0.1 μm, the light emission becomes non-uniform, the driving voltage of the device must be increased, and the charge injection efficiency is significantly reduced.

The conditions for vacuum deposition are not particularly limited.
The degree of vacuum is 0 ^-4 Pa or less, and the deposition rate is 0.01 to 1 nm /
It is preferable to set it to about sec. Further, it is preferable to form each layer continuously in a vacuum. If they are formed continuously in a vacuum, impurities can be prevented from adsorbing at the interface between the layers, so that high characteristics can be obtained. Further, the driving voltage of the element can be reduced, and the growth and generation of dark spots can be suppressed.

In the case where a plurality of compounds are contained in one layer when a vacuum evaporation method is used for forming each of these layers, it is preferable to co-deposit each boat containing the compounds by individually controlling the temperature.

The organic EL device used in the present invention is usually used as a DC drive type EL device, but it can be AC drive or pulse drive. The applied voltage is
Usually, it is about 2 to 20V.

[0152]

Next, the present invention will be described more specifically with reference to examples. Here, as an example of the simplest organic EL element,
It has a structure of an electron injection electrode (metal thin film) / organic layer 1 / organic layer 2 / hole injection electrode (transparent electrode) / glass substrate, and light emission is performed at the interface between the organic layer 1 and the organic layer 2.
With respect to such an organic EL element, the conventional simulation model and the simulation model of the present invention were respectively operated (the above simulation model was developed using a numerical calculation program (Mathematica) on a commercially available personal computer), and the obtained results were obtained. Was compared with experimental data (actual value).

As an element structure, an organic EL having the above basic structure is used.
The device had the following contents (measurement was performed by ellipsometry). Amplitude reflectance on metal surface: k = 1 Organic layer 1 = Alq3: Refractive index n1 = 1.7, thickness d1 = 70 nm Organic layer 2 = TPD: Refractive index n2 = 1.7, thickness d2 = 60 nm Hole Injection electrode = ITO: refractive index n3 = 1.9, glass substrate with changed thickness d3: refractive index n4 = 1.5 Fluorescence spectrum of luminescent material: shown in FIG. Visibility coefficient spectrum: shown in FIG.

[Emission Spectrum] <Example: Invention Model> The simulation model according to the present invention is as follows.

[0155]

[Equation 59]

<Comparative Example: Conventional Model> A conventional simulation model is as follows.

[0157]

[Equation 60]

In each of the above simulation models,
The calculation was performed when the thickness of the hole injection electrode (ITO) was changed to 50 to 200 nm. The results obtained are shown in FIG.
As shown in FIG. In the figure, a broken line indicates a conventional example, a solid line indicates an embodiment, and a vertical axis indicates an arbitrary amount.

<Comparative Example: Actual Measurement Model> An organic EL device having the above-described structure and the thickness d3 of the ITO electrode was actually manufactured by a vapor deposition method. The emission spectrum of each of the obtained organic EL devices was measured using a spectral luminance meter. The obtained results are shown in FIGS.

As apparent from FIGS. 12 to 18, IT
The spectrum of the measured model changes depending on the thickness of O, and the change is in good agreement with the model of the present invention. Since ITO is an electrode, there is little electrical change even if its film thickness changes, so that in principle, a change in emission spectrum is an optical modulation effect.

[Emission Luminance] <Example: Invention Model> A simulation model according to the present invention is as follows.

[0162]

[Equation 61]

<Comparative Example: Conventional Model> A conventional simulation model is as follows.

[0164]

(Equation 62)

In each of the above simulation models,
The calculation was performed when the thickness of the hole injection electrode (ITO) was changed between 0 and 200 nm and between 0 and 1000 nm. The obtained results are shown in FIGS. In the figure, a broken line indicates a conventional example, and a solid line indicates an embodiment.

<Comparative Example: Actual Measurement Model> An organic EL device having the above-mentioned structure and the thickness d3 of the ITO electrode changed to 50 to 200 nm was manufactured by a vapor deposition method. The emission luminance of each of the obtained organic EL devices was measured using a spectral luminance meter. FIG. 21 shows the obtained result.

As is apparent from FIG. 21, the luminance of the measured model changes depending on the thickness of the ITO, and the change is in good agreement with the model of the present invention. Since ITO is an electrode, there is little electrical change even if its film thickness changes, and in principle, the change in light emission luminance is an optical modulation effect.

From the results of the comparison between the simulation model and the actually measured values, it can be seen that the model of the present invention is considerably more accurate than the conventional model. And
Accurate simulation can be performed by quantitatively considering the reflected light other than the metal surface, and when optically modulating the emission spectrum of the organic EL light emitting element, the optical configuration of the element that obtains the desired modulation is determined. can do. On the other hand, in the conventional simple approximation formula, since the modulation by the reflected light other than the metal surface is neglected, an error in that portion is included. Further, only the conventional qualitative study cannot quantitatively predict a change in spectrum, and cannot be applied to a case where various wavelengths such as white light are mixed.

In the above example, a simulation was performed for a simple structure of an organic EL element using Alq3, but it goes without saying that the present invention can be applied to other systems. The light emission point was examined in the case of localized light emission. If the light emission point has a distribution (it is assumed that light emission in different light emission regions has no correlation), simply integrating the contribution from each minute light emission region Good. Subsequent handling is the same.

Next, a description will be given of the points found by the simulation result of this time.

The brightness changes in accordance with the thickness d3 of the hole injection electrode and gradually converges. This indicates that reflection at this interface is dominant because the difference between the refractive indices of n3 and n4 is large. However, for example, when the reflection at the other interface is large, it can be easily inferred that the reflection also depends on the optical distance.

The above simulation is not limited to the configuration as described above, but can be applied to, for example, an element having a configuration of substrate / electron injection electrode / organic layer / transparent electrode / optical layer.

From the above results, it was found that the relationship between the optical configuration of the organic EL device and the light emission characteristics could be calculated. Therefore, the relationship between the variation in the optical characteristics and the variation in the optical film thickness can be understood. The above simulation model determines the required value of the film thickness variation in the element configuration in order to achieve the desired optical variation.

For example, in the above configuration example, d3 = 100 nm
(ITO film thickness), ± 5%
It can be seen that it is necessary to suppress the variation of the film thickness to within ± 20% in order to keep the thickness within ± 20%. D3 = 70n
m, 200 nm, ± 5% variation in luminance
It can be seen that it is necessary to suppress the variation of the film thickness to within ± 10% in order to keep the thickness within ± 10%. When converted to film thickness variation, d
3 = ± 13% at 70 nm and ± 5% at 200 nm, the thinner the film, the more advantageous. In general, the variation in the film thickness in the film forming apparatus is about ± 5% with respect to the film thickness.
= 70 nm is preferable, and the variation in luminance is ± 5%.
It can be seen that the total optical thickness of the ITO transparent electrode and the organic layer needs to be 1.9 × 200 nm or less in order to keep the thickness within this range.

The above calculation example is merely an example. Therefore, when the other constituent film thickness changes, the value becomes a value corresponding to the change. Generally, the smaller the film thickness, the smaller the variation in the absolute value of the film thickness. Therefore, it is important to reduce the variation in the configuration with the thin film thickness.

The above-mentioned simulation and its feedback can be extended even if the system is made of a different material or optical system, by constructing an equation corresponding to the system and calculating it.
For example, in the above configuration example, the case where the ITO transparent conductive film / organic layer is formed on the glass substrate was examined,
It is also possible to examine the variation in brightness in the case where a buffer layer Nr coated with a polyimide, a resist or the like is provided on a glass substrate and an ITO transparent conductive film / organic layer / electron injection electrode is further formed thereon.

In general, the refractive indices of the buffer layer Nr and the transparent conductive film are close to each other, and are about 1.8 to 2.0, but glass is usually about 1.5. Therefore, light reflected at the interface between the glass and the buffer layer Nr causes modulation. In order to suppress the luminance variation, the thickness variation of the buffer layer Nr is an important factor, and it is necessary to accurately suppress the variation within several tens of nm. However, it is extremely difficult with a general resist or polyimide. By the way, from the result of this study, it is known that the change in luminance due to modulation converges as d3 increases. Therefore, in this case, it can be seen that a result can be obtained in which the thickness of the buffer layer Nr can be sufficiently increased. And from the above simulation result,
In the case of this example, it is understood that the thickness of the buffer layer should be 700 nm or more. It can be seen that the total optical thickness of the ITO transparent electrode, the buffer layer, and the organic layer needs to be 1.9 × 200 nm or less in order to suppress the variation in luminance to within ± 5%.

[0178]

As described above, according to the present invention, by simply approximating the reflected light other than those conventionally studied, the light is emitted to the outside from an organic EL element having a general arbitrary structure. It is possible to provide a method and an apparatus for simulating an organic EL device, which can accurately predict a spectrum and design a device for obtaining a desired spectrum.

Further, it is possible to provide a method and apparatus for simulating an organic EL element capable of realizing a structure capable of efficiently extracting light even with a structure having many reflecting surfaces.

Further, it is possible to provide a method and apparatus for simulating an organic EL device capable of realizing a device configuration capable of reducing optical variations.

Further, from the results of the simulation, it is possible to provide an organic EL device having a device configuration capable of reducing optical variations.

[Brief description of the drawings]

FIG. 1 is a simulation model of an organic E according to the present invention.
It is a conceptual diagram of an L element.

FIG. 2 is a conceptual diagram showing a case where a light emitting region of the organic EL element of FIG. 1 has a certain width.

FIG. 3 is a diagram showing a fluorescence spectrum of a luminescent substance of the organic EL device used in the example.

FIG. 4 is a diagram showing a spectrum of a visibility coefficient used in the example.

FIG. 5 is a diagram showing emission spectra of an example and a comparative example when the film thickness of ITO is 50 nm.

FIG. 6 is a diagram showing emission spectra of an example and a comparative example when the thickness of ITO is 75 nm.

FIG. 7 is a diagram showing emission spectra of an example and a comparative example when the film thickness of ITO is 100 nm.

FIG. 8 is a diagram showing emission spectra of an example and a comparative example when the thickness of ITO is 125 nm.

FIG. 9 is a diagram showing emission spectra of an example and a comparative example when the film thickness of ITO is 150 nm.

FIG. 10 is a diagram showing emission spectra of an example and a comparative example when the film thickness of ITO is 175 nm.

FIG. 11 is a diagram showing emission spectra of an example and a comparative example when the film thickness of ITO is 200 nm.

FIG. 12 is a view showing an emission spectrum of an actually measured value when the film thickness of ITO is 50 nm.

FIG. 13 is a diagram showing an emission spectrum of an actually measured value when the film thickness of ITO is 75 nm.

FIG. 14 is a diagram showing an emission spectrum of an actually measured value when the thickness of ITO is 100 nm.

FIG. 15 is a diagram showing emission spectra of actually measured values when the thickness of ITO is 125 nm.

FIG. 16 is a view showing an emission spectrum of an actually measured value when the film thickness of ITO is 150 nm.

FIG. 17 is a view showing an emission spectrum of an actually measured value when the film thickness of ITO is 175 nm.

FIG. 18 is a diagram showing an emission spectrum of an actually measured value when the film thickness of ITO is 200 nm.

FIG. 19 is a diagram showing light emission luminances of an example and a comparative example when the thickness of ITO was changed from 0 to 200 nm.

FIG. 20 is a diagram showing light emission luminances of an example and a comparative example when the thickness of ITO is changed from 0 to 1000 nm.

FIG. 21 is a diagram showing measured light emission luminance when the film thickness of ITO is changed from 50 to 200 nm.

Claims (8)

[Claims] 1. A method for simulating an organic EL device having a metal surface on one surface, a light emitting source and a plurality of optical thicknesses, comprising: a simulation model represented by the following (I): (I) A method for simulating an organic EL element for designing a structure for extracting light from the emission spectrum obtained from (I). (I) In an organic EL device having q kinds of layers on the metal surface side of a light emitting source and p kinds of layers with different refractive indices on the opposite side, a total synthetic wave Φ [λ] composed of a reflected wave Φ nm at each interface
Is given by (Where λ is the wavelength, Φ nm is the reflected wave from the n-layer to the m-layer, and p> 1, q ≧ 1. However, the p-layer is made of a sufficiently thick glass or glass that does not contribute to interference. In the case of q = 1, the third term on the right side is 0 when q = 1, and the subscript-, that is, the invert symbol is a quantity related to the layer on the metal surface side from the light emitting point. And the same is included in the total combined wave Φ [λ], the light emitted from the light emitting source forward and emitted without being reflected at the interface, and the light emitted backward from the light emitting source and The combined wave Φ1 with the light reflected from the surface and emitted forward without being reflected at the other interface is expressed as follows: (Where n _m : refractive index of m layer, Δ _m : optical path length of m layer,
r _mn : the amplitude reflectance when a light wave enters the n-layer from the m-layer,
Φ: amplitude of light wave, ρ: square of light wave amplitude (energy), L: optical path length, λ: wavelength, d: film thickness, n: refractive index. Hereinafter, the same shall apply), which is included in the total synthetic wave Φ [λ], is emitted forward from the light emitting source, is reflected at the interface of the t-th layer, is reflected by the metal surface, and is directed forward. The light emitted without being reflected by the And is emitted backward from the light-emitting source and reflected at the interface of the t-th layer, and then emitted forward without being reflected at the other interface, which is included in the total synthetic wave Φ [λ]. The light, The light is emitted backward from the light-emitting source, reflected on the metal surface, travels forward, is reflected at the interface of the t-th layer, and is further reflected on the metal surface, which is included in the total synthetic wave Φ [λ]. Then, the light emitted forward without being reflected at the other interface is given by And the normalized reflectance spectrum ρ obtained from the composite wave of each of the above lights, where -k is the amplitude reflectance on the metal surface.
[λ] is given by (Where * represents a complex number; the same applies hereinafter), and when the spectrum of the light-emitting source is represented by IPL [λ], the spectrum IEL emitted to the outside through the p-layer (glass substrate) under optical modulation. [λ] is given by Simulation model represented by 2. The method for simulating an organic EL device according to claim 1, wherein said simulation model (I) further comprises:
When the visibility coefficient is represented by θ [λ], A simulation method of an organic EL element for designing a structure for extracting light from the emission luminance obtained in the above. 3. The method for simulating an organic EL device according to claim 1, wherein in the simulation model (I), light emission is a light emitting layer having a constant thickness of a thickness de. Let η [x] be the amount of recombination at point x, which is an arbitrary point in
When the intensity due to interference is ρ [x, λ], the amount of recombination η [x] is replaced with the emission intensity distribution φ [x] to obtain the interference spectrum as And the spectrum IEL [λ] emitted from the outside
Is given by And the luminance L is given by The method for simulating an organic EL device according to claim 1, wherein: 4. An apparatus for simulating an organic EL device having a metal surface on one surface, a light-emitting species and a plurality of optical film thicknesses, wherein a simulation model (I) represented by the following (I) is developed. An apparatus for simulating an organic EL element, comprising: a control program, which is controlled by the control program, and an arithmetic unit that calculates a light emission spectrum. (I) In an organic EL device having a q-type layer on the metal surface side and a p-type layer having a different refractive index on the opposite side, a total synthetic wave Φ composed of a reflected wave Φnm at each interface.
[λ] is given by (Where λ is the wavelength, Φ nm is the reflected wave from the n-layer to the m-layer, and p> 1, q ≧ 1. However, the p-layer is made of a sufficiently thick glass or glass that does not contribute to interference. In the case of q = 1, the third term on the right side is 0 when q = 1, and the subscript-, that is, the invert symbol is a quantity related to the layer on the metal surface side from the light emitting point. And the same is included in the total combined wave Φ [λ], the light emitted forward from the light emitting source and emitted without being reflected at the interface, and the light emitted backward from the light emitting source and The combined wave Φ1 with the light emitted forward without being reflected by the other surface and reflected by the surface is expressed as follows: (Where n _m : refractive index of m layer, Δ _m : optical path length of m layer,
r _mn : the amplitude reflectance when a light wave enters the n-layer from the m-layer,
Φ: amplitude of light wave, ρ: square of light wave amplitude (energy), L: optical path length, λ: wavelength, d: film thickness, n: refractive index. The same shall apply hereinafter), which is included in the total synthetic wave Φ [λ], is emitted forward from the light-emitting source, is reflected at the interface of the t-th layer, and is then reflected by the metal surface to face the other interface. The light emitted without being reflected by the And is emitted backward from the light emitting source included in the total synthetic wave Φ [λ], reflected at the interface of the t-th layer, and then emitted forward without being reflected at the other interface. The light, The light is emitted backward from the light-emitting source, reflected in the metal surface, goes forward, is reflected in the interface of the t-th layer, and is further reflected in the metal surface, which is included in the total synthetic wave Φ [λ]. Then, the light emitted forward without being reflected at another interface is given by And the modulation spectrum ρ [λ] obtained from the composite wave of each light is represented by the following equation. (Where * represents a complex number; the same applies hereinafter), and when the spectrum of the light-emitting source is represented by IPL [λ], the spectrum IEL emitted to the outside through the p-layer (glass substrate) under optical modulation. [λ] is given by Simulation model represented by (Where n _m : m
Refractive index of layer, Δ _m : optical path length of m layer, r _mn : amplitude reflectance when light wave enters from m layer to n layer, Φ: amplitude of light wave, ρ
The square of the amplitude of the light wave (energy), L: optical path length, λ: wavelength, d: film thickness, n: refractive index. ) 5. The simulation device for an organic EL device according to claim 4, wherein, in the simulation model (I), when a visibility coefficient is represented by θ [λ], A simulation device for an organic EL element that calculates the light emission luminance as an example. 6. The simulation device for an organic EL device according to claim 4, wherein in the simulation model (I), the light emission is a light emission layer having a constant thickness of de, wherein Let η [x] be the amount of recombination at point x, which is an arbitrary point in
When the intensity due to interference is ρ [x, λ], the amount of recombination η [x] is replaced by the emission intensity distribution φ [x] to obtain the interference spectrum as And the spectrum IEL [λ] emitted from the outside
Is given by And the luminance L is Simulation device for an organic EL element represented by 7. A glass substrate (refractive index: n = 1.5 or less)
And a hole injection electrode (refractive index: n = 1.8 to 2.1)
And an organic layer (refractive index: n = 1.7 to 2.1) and an electron injection electrode (reflectance of 50% or more in a wavelength region of 300 to 700 nm). An organic EL device in which the total optical film thickness (n × film thickness) is 1.9 × 200 nm or less and the variation in luminance is within ± 5%. 8. A glass substrate (refractive index: n = 1.5 or less)
And a buffer layer (refractive index: n = 1.8 to 2.1);
A hole injection electrode (refractive index: n = 1.8 to 2.1), an organic layer (refractive index: n = 1.7 to 2.1), and an electron injection electrode (reflection in a wavelength range of 300 to 700 nm) Rate of 50% or more), and the total of the optical thicknesses (n × thickness) of the hole injection electrode, the buffer layer, and the organic layer is 1.9 × 700 nm or more, and the variation in luminance is ± 5. % Organic EL device.