JP4989367B2 - Design method of organic electroluminescence device - Google Patents

Description

The present invention provides an organic electroluminescent device having a desired amount of light emitted from the organic electroluminescent device when the region where the reflection / refraction angle is disturbed is provided to improve the light extraction efficiency. about the design method of the organic electroluminescence element of designing the thickness of the organic luminescent layer.

  FIG. 2 shows an organic electroluminescence element (organic EL element) in which a light transmissive electrode 1, a hole transport layer 8, a light emitting layer 3, an electron transport layer 9, and a light reflective electrode 2 are sequentially formed on a light transmissive substrate 6. Element). A conventional organic EL element designing method will be described with reference to FIG.

  In Patent Document 1, when light is reflected at the interface between the light-reflective electrode 2 and the organic layer 4 adjacent thereto (here, the electron transport layer 9), the phase shift π before and after the reflection because it is an external reflection. On the assumption that the light is emitted from the light emitting layer 3 toward the substrate 6 and the light 21 from the light emitting layer 3 toward the light reflective electrode 2 and then reflected from the surface of the electrode 2 and then toward the substrate 6. The optical film thickness D derived by multiplying the film thickness d between the light-emitting source 10 and the surface of the light-reflective electrode 2 in the light-emitting layer 3 by the refractive index so as to interfere with each other. Is approximately equal to an odd multiple of ¼ of the wavelength λ of the light, so that the amount of light components emitted from the substrate 6 in the front direction to the outside can be maximized. ing.

However, as described in Patent Document 2, the phase shift generated on the surface of the light reflective electrode 2 is not π, but the refractive index n ₁ and the extinction coefficient k _{1 of the} organic layer 4 (electron transport layer 9). In addition, based on the refractive index n ₂ and extinction coefficient k ₂ of the light-reflective electrode 2, the phase shift φ is expressed by the following equation (1).

  In Patent Document 2, in consideration of this phase shift φ, the optical film thickness D from the light source 10 to the surface of the electrode 2 is set so that the amount of the component of light emitted from the substrate 6 to the outside becomes a maximum value. Satisfies the following formulas (2) to (4).

2π / 9 ≦ φ ≦ 15π / 18 (2)
F = φ × λ / 4π (3)
0.73F ≦ D ≦ 1.15F (4)
Here, the propagation of the light 23 emitted obliquely from the light source 10 of the light emitting layer 3 of the organic EL element in FIG. 2 will be described. Actually, there is light traveling from the light source 10 to the light-reflective electrode 2, but it is omitted here. When light propagates from a medium with a high refractive index to a medium with a low refractive index, the critical angle is determined from Snell's law by the refractive index between the medium at the interface, and light above the critical angle is totally reflected at the interface. Thus, it is trapped in a medium having a high refractive index and lost as guided light. For example, in the organic EL element of FIG. 2, when the refractive index of the substrate 6 is 1.5, the critical angle of light emitted from the substrate 6 to the atmosphere 11 having a refractive index of 1.0 is about 42 °. That is, when the light 23 emitted from the light source 10 is emitted from the substrate 6 to the atmosphere 11, the light having an incident angle θ to the atmosphere 11 larger than about 42 ° is confined in the substrate 6 and lost as guided light. Considering the solid angle, the proportion of the light propagating to the substrate 6 is about 26%, and the remaining about 74% is confined in the substrate 6 and lost as guided light. .

  As a method for extracting the guided light to the outside, for example, a region 7 that disturbs the reflection / refraction angle is formed between the substrate 6 and the atmosphere 11 as in the organic EL element of FIG. In this case, Snell's law can be broken to change the propagation angle of light of about 42 ° or more which is totally reflected as originally guided light, thereby changing the refraction angle of the light and changing the light under total reflection conditions. Can be reduced. As such a method, for example, a method of forming a light diffusion layer using a diffusion member in which single particle layers are arranged on a translucent substrate (Patent Document 3) can be mentioned.

  Patent Document 4 proposes a design method for efficiently extracting light guided in the substrate 6 when such a light diffusion layer is formed. This is so that the front luminance value of the emitted light emitted from the substrate 6 to the atmosphere 11 and the luminance value in the direction of 50 to 70 ° satisfy the relationship of the following equation (5), or further, the light emitting source 10 and the light reflecting property. The dimension between the surface of the electrode 2 is d, the peak wavelength of the fluorescence emission spectrum of the light emitting material used in the light emitting layer 3 is λ, and the refractive index of the organic layer 4 between the light emitting layer 3 and the reflective electrode is n. In this case, the relationship of the following formula (6) is satisfied.

(Front luminance value) <(Brightness value in the direction of 50 to 70 °) (5)
(3 / n) λ <d <(0.5 / n) λ (6)
According to this design method, the light in the front direction is weakened by interference, but light with a wide angle component that is normally confined in the element as guided light is strengthened, and this light is emitted to the outside by providing a light diffusion layer. This is to improve the overall light extraction efficiency.
JP 2000-243573 A JP 2004-165154 A JP 2001-356207 A JP 2004-296423 A

  However, in the method described in Patent Document 1, the phase shift at the time of reflection at the light reflective electrode 2 is not accurately taken into consideration, and the surface of the light reflective electrode 2 from the light emitting source 10 according to this method. Even if the dimensions up to are designed, the amount of the component of the light emitted from the substrate 6 to the outside in the front direction cannot be set to the maximum value.

  Further, in the method described in Patent Document 2, since the above phase shift is accurately taken into consideration, it is possible to design so that the amount of the light component emitted from the substrate 6 to the outside in the front direction becomes a maximum value. However, about 70% of the light component lost by being guided through the substrate 6 is not taken into consideration. Therefore, when a light diffusing layer is provided to extract the originally lost light, the light extraction efficiency is reduced. Is not necessarily the highest.

  In the method described in Patent Document 4, the light extraction efficiency can be improved when the lost light is guided through the substrate 6 by providing the light diffusion layer. However, the light that changes due to the interference effect can be improved. In the case where only one local maximum value of the component amount is derived and the dimension between the light emitting source 10 and the surface of the light-reflecting electrode 2 cannot be set to the local maximum value, for example, the light emitting layer 3 In the case where the dimension between the light emitting source 10 and the surface of the light-reflective electrode 2 has to exceed the dimension that can take the maximum value as in the case of providing a plurality of layers Met.

The present invention has been made in view of the above points, and by providing a region in which the reflection / refraction angle is disturbed between the substrate of the organic electroluminescence element and the atmosphere, the light originally guided through the substrate is externally transmitted. Providing a design method for organic electroluminescent devices that can improve the amount of light components emitted to the outside by setting the thickness of the organic light-emitting layer within a wide range to improve light extraction efficiency It is intended to do.

  The organic electroluminescent element design method according to claim 1 is provided with an organic light emitting layer 5 including a light emitting layer 3 and another organic layer 4 between a light transmissive electrode 1 and a light reflective electrode 2. A method for designing an organic electroluminescent element comprising a light-transmitting substrate 6 on the surface opposite to the organic light-emitting layer 5 of the light-transmitting electrode 1, wherein the substrate 6 has a light-transmitting property. Each thickness, refractive index and extinction coefficient of the electrode 1, the light emitting layer 3 and the other organic layer 4, and the refractive index and extinction coefficient of the light reflective electrode 2, and photoluminescence of the light emitting material in the light emitting layer 3 By performing an optical propagation analysis using the spectrum, the position of the light emitting point in the light emitting layer 3 and the light emission distribution as a factor, the amount of the light component guided inside the substrate 6 and the light reflecting property from the light emitting point are obtained. Up to the surface of electrode 2 Deriving a relationship between the law, on the basis of this relationship, characterized by designing the thickness of the organic light-emitting layer 5 in the case of providing the region 7 causes disturbance reflection and refraction angle to the substrate 6.

  The invention according to claim 2 is characterized in that, in claim 1, the amount of the light component is a light beam in consideration of visibility.

  The invention according to claim 3 is characterized in that, in claim 1, the amount of the light component is the number of photons.

  The invention according to claim 4 is characterized in that, in claim 1, the amount of the light component is energy.

Organic electroluminescent device is characterized in that it is designed by the method according to any one of claims 1-4.

  According to the first aspect of the present invention, the amount of the light component guided through the substrate 6 and the light reflection from the position of the light emitting point in the state where the region 7 for disturbing the reflection / refraction angle of light is not provided. When the region 7 for disturbing the reflection / refraction angle is provided in the substrate 6 of the organic electroluminescence element by determining the thickness of the organic light emitting layer 5 from the relationship with the dimension to the surface of the conductive electrode 2 The amount of the light component of the emitted light can be set to a desired level, and if the relationship is derived over a wide thickness range of the organic light emitting layer 5 at this time, a wide thickness range is obtained. Thus, the thickness of the organic light emitting layer 5 can be designed.

  According to the second aspect of the present invention, the light reflecting from the position of the luminous flux guided through the substrate 6 and the light emitting point without the region 7 that disturbs the reflection / refraction angle of light is provided. By determining the thickness of the organic light-emitting layer 5 from the relationship between the dimensions to the surface of the electrode 2, the emission light in the case where the region 7 for disturbing the reflection / refraction angle is provided on the substrate 6 of the organic electroluminescence element. In this case, if the above relationship is derived over a wide thickness range of the organic light emitting layer 5, the organic light emitting layer 5 can be obtained over a wide thickness range. The thickness can be designed.

  According to the invention of claim 3, the light reflectivity is determined from the number of photons guided in the substrate 6 and the position of the light emitting point in a state where the region 7 for disturbing the reflection / refraction angle of light is not provided. By determining the thickness of the organic light-emitting layer 5 from the relationship between the dimensions of the electrode 2 to the surface of the electrode 2, a region 7 in which the reflection / refraction angle is disturbed is provided in the substrate 6 of the organic electroluminescence element. The number of photons or the quantum efficiency of the incident light can be set to a desired level, and if the relationship is derived over a wide thickness range of the organic light emitting layer 5 at this time, a wide thickness range can be obtained. The thickness of the organic light emitting layer 5 can be designed over the entire length.

  According to the fourth aspect of the present invention, the energy of the light guided inside the substrate 6 and the light reflection from the position of the light emitting point without the region 7 that disturbs the reflection / refraction angle of light are provided. When the region 7 for disturbing the reflection / refraction angle is provided in the substrate 6 of the organic electroluminescence element by determining the thickness of the organic light emitting layer 5 from the relationship with the dimension to the surface of the conductive electrode 2 The energy of the emitted light can be set to a desired level, and if the above relationship is derived over a wide thickness range of the organic light emitting layer 5 at this time, the energy can be extended over a wide thickness range. Thus, the thickness of the organic light emitting layer 5 can be designed.

Further, the amount of components of light of the emitted light to obtain an organic electroluminescent device which is designed to be a desired degree obtained when a region 7 causes disturbance reflection and refraction angle to the substrate 6 of the organic electroluminescent device It is something that can be done.

  Hereinafter, the best mode for carrying out the present invention will be described.

  FIG. 2 shows an example of the configuration of an organic electroluminescence element (organic EL element).

  In this organic EL element, a light transmissive electrode 1, an organic light emitting layer 5, and a light reflective electrode 2 are sequentially laminated in this order on one surface side of a transparent substrate 6. The organic light emitting layer 5 is formed by laminating a suitable organic layer 4 such as an electron injection layer, an electron transport layer 9, a hole injection layer, a hole transport layer, or the like, as necessary, on the light emitting layer 3 containing a light emitting material. The In the illustrated example, an electron transport layer 9 is interposed between the light reflective electrode 2 and the light emitting layer 3, and a hole transport layer 8 is interposed between the light transmissive electrode 1 and the light emitting layer 3. .

  As a material of each layer constituting the organic EL element, an appropriate material applied to the organic EL element can be adopted and is not particularly limited.

  In designing such an organic EL element, in the present invention, by performing an optical propagation analysis, the amount of light component guided through the substrate 6 of the organic EL element (waveguide component amount) and the light emitting point are determined. The relationship between the dimension to the surface of the light-reflective electrode 2 (light emitting point position dimension) is obtained, and the thickness of the organic light emitting layer 5 is designed based on the relationship.

  Here, the light component is a component for evaluating the emission of organic electroluminescence. For example, the luminous flux considering the visibility, the number of photons for obtaining the quantum efficiency, or the light energy (radiant flux). For example, an appropriate one is selected as necessary.

  In performing the optical propagation analysis, when the substrate 6, the light transmissive electrode 1, the light emitting layer 3, and the organic layer 4 other than the light emitting layer 3, each thickness, refractive index and extinction coefficient of the organic layer 4 are provided. And the refractive index and extinction coefficient of the light-reflecting electrode 2, the photoluminescence spectrum (PL spectrum) of the light emitting material in the light emitting layer 3, the position of the light emitting point and the light emission distribution in the light emitting layer 3, and To do.

  As for the position of the light emitting point and the light emission distribution in the light emitting layer 3, one light emitting point is set in the light emitting layer 3, and the light emission distribution is a distribution of the light emitting sources 10 in the thickness direction in the light emitting layer 3 based on the light emitting point. Can be used. The position of the light emitting point can be set to a position where light is most intensely emitted in the light emitting layer 3 or a position corresponding thereto. Further, as the light emission distribution, for example, a delta distribution, a rectangular distribution, a Gaussian distribution, a distribution that decreases exponentially with a light emission point as a peak, or the like that reflects the distribution of the light source 10 depending on the configuration of the organic EL element. Can be set.

  For example, when the electron mobility in the light emitting layer 3 is much larger than the hole mobility as in the case of using Alq3 or the like as the light emitting material in the light emitting layer 3, the hole transport layer 8 and the light emitting layer 3 are mainly used. It is thought that the recombination of electrons and holes occurs at the interface and the strongest light emission occurs. In this case, the position of the light emitting point can be set at the interface between the hole transport layer 8 and the light emitting layer 3, and the light emission distribution can be set as a delta distribution.

  Further, when the thickness of the light emitting layer 3 is extremely thin as in the case of about 1 nm or less, a light emitting point is set at the center of the light emitting layer 3 in the thickness direction, and the light emission distribution is the thickness of the light emitting layer 3. Alternatively, the light emission distribution may be set to be distributed only at the light emitting points (no distribution).

  When the position of the light emitting point in the light emitting layer 3 and the light emission distribution are unknown, an organic EL element having a target configuration is prepared in advance, and the angular characteristics of the amount of light components extracted from this element are measured. On the other hand, the angle characteristic of the amount of the light component is obtained while changing the position of the light emitting point and the light emission distribution in the light emitting layer 3 for the organic EL element having the above configuration by optical propagation analysis described later, and the two are compared. The position of the light emitting point that coincides with the actual measurement and the light emission distribution may be set.

  Moreover, although a literature value may be used as the PL spectrum of the light emitting material in the light emitting layer 3, it is preferable to use a measured value. In the actual measurement, for example, only the light emitting layer 3 is formed on the glass substrate 6 to a thickness of several tens of nanometers by vapor deposition, and the light emitting layer 3 is irradiated with ultraviolet rays to emit light, and the light emission is integrated. The emission spectrum of the luminescent material can be measured by measuring using a sphere or the like.

  In addition, literature values may be used for the refractive index and extinction coefficient of the light transmissive electrode 1, the light emitting layer 3, the organic layer 4, and the light reflective electrode 2, but measured values should be used. Is preferred. In the actual measurement, for example, only a material for forming each layer is formed on the glass substrate 6 to a thickness of several tens of nanometers by vapor deposition or the like, and the spectroscopic method and the ellipsometer or normal incidence transmission reflection refraction are applied to this layer. The transmittance and the reflectance are measured using a ratio meter, the dielectric constant is determined from the Lorentz model, and the refractive index and the extinction coefficient can be obtained by calculating backward from the values. The refractive index and extinction coefficient are obtained for each wavelength.

  In the optical propagation analysis using these factors, the thickness of each layer of the organic EL element excluding the substrate 6 is about several nanometers to several hundred nanometers, which is about the same as the wavelength of visible light 380 to 780 nm. In this, multiple interference of light occurs.

  Therefore, by using the above factors, the light component considering the refractive index and extinction coefficient for each wavelength of the material of each layer of the organic EL element, the position of the light emitting point in the light emitting layer 3, the light emission distribution, and the PL spectrum. The optical propagation analysis is performed to analyze the angular characteristics of the amount of the above. In this optical propagation analysis, for example, theoretical calculation based on wave optics (Fresnel theory analysis) combining Fresnel theory and characteristic matrix calculation, numerical calculation (FDTD method) to solve Maxwell's equations by time domain difference method, etc. are applied. Can do.

  The relationship between the amount of the guided component and the light emitting point position size can be obtained by optical propagation analysis by information processing by a computer using a program for optical propagation analysis. An example of the flow of the procedure executed by the computer in this case will be described with reference to FIG.

  (S1) First, an operator starts an optical propagation analysis program on a computer.

  (S2) Next, when the operator inputs the layer configuration of the organic EL element to be designed and the values of the material, configuration, and film thickness of each layer, the input values are set as factors of the optical propagation analysis. At this time, regarding the thickness of the organic layer 4, the thickness of the organic layer 4 correlating with the light emitting point position dimension is a variable, and the thickness of the remaining organic layer 4 is set. For example, in the organic EL element having the configuration shown in FIG. 1, the thickness of the electron transport layer 9 interposed between the light emitting layer 3 and the light reflective electrode 2 is used as a variable, and a plurality of organic layers 4 are interposed. Uses the thickness of these organic layers 4 as a variable.

  (S3) Next, when the operator inputs the refractive index and extinction coefficient for each wavelength for the material of each layer, the input values are set as the factors of the optical propagation analysis. It should be noted that the refractive index and extinction coefficient for each wavelength of the material widely used for the organic EL element are stored in advance in a computer memory or an appropriate storage medium, and the material set at the time of setting the material is stored. The refractive index and extinction coefficient for each wavelength may be automatically read and set.

  (S4) Next, when the operator inputs the PL spectrum of the material used for the light emitting layer 3, these are set as the factors of the optical propagation analysis.

  (S5) Next, when the position of the light emission point and the light emission distribution are input by the operator, these are set as factors of the optical propagation analysis.

  (S6) Next, when the type of light component acquired by the operator is input, the type of light component is set.

  (S7) Next, when the light emitting point position size range (initial value and maximum value) and step size are input by the operator, the size range and step size are set. It should be noted that the input by the operator is unnecessary, and the dimension range and step size may be set in advance. For example, the initial value can be set to 40 nm, the maximum value can be set to 740 nm, and the step size can be set to 10 nm.

  (S8) Next, the light emitting point position dimension is set to the initial value set in S7, and the thickness of the organic layer 4 such as the electron transport layer 9 which is a variable in S2 is set as the light emitting point position dimension. Set to a value that matches the value. When the thickness of two or more organic layers 4 is a variable, for example, the ratio of the thicknesses of the two or more organic layers 4 is kept constant, or the thickness of one specific organic layer 4 is determined. The thickness of the organic layer 4 can be set by an appropriate method such as fixing the thickness of the other organic layer 4 by changing the above.

  The order of executing S2 to S8 is not limited to the above, and the order may be changed as appropriate.

  (S9) Next, optical propagation analysis such as Fresnel theory analysis is performed on the light in the organic EL element, and the amount of guided component is acquired. Here, Fresnel theory analysis is used as the optical propagation analysis.

  The process in S9 can be performed, for example, by executing the following steps T1 to T10. At this time, it is assumed that the light emitting source 10 in the light emitting layer 3 is a point light source distributed according to the position of the light emitting point and the light emission distribution, and emits light isotropically in all directions. Further, it is assumed that light from the same light source 10 is emitted in the same phase in all directions and multiple interference occurs in the light emitting layer 3, but light emitted from different light sources 10 does not interfere with each other. It is assumed that the interface between the layers is flat. Further, it is assumed that the amount of light component is an average value of s-polarized light and p-polarized light.

  Further, when deriving the amount of the guided component, the component of light emitted from the substrate 6 is assumed when the substrate 6 is in contact with a layer having the same refractive index and the same extinction coefficient as the substrate 6. The amount of light components emitted from the substrate 6 when the substrate 6 is assumed to be in direct contact with the atmosphere 11, and the value obtained by subtracting the latter value from the former value, Derived as the amount of guided component.

  (T1) First, the initial value of each value is set by using the emission angle of light from the light source 10 to the upper layer side and the lower layer side, the light emission wavelength, and the position of the light source 10 in the light emitting layer 3 as parameters.

  (T2) Next, the set value of the light emission angle, the emission wavelength, and the position of the light source 10 in the light emitting layer 3, the substrate 6, the light transmissive electrode 1, the light emitting layer 3, and the light emitting layer. The thickness, refractive index, and extinction coefficient of the organic layer 4 other than 3 (electron transport layer 9, hole transport layer 8, etc.) and the set values of the refractive index and extinction coefficient of the light-reflecting electrode 2 are set. Based on the assumption that a layer having the same refractive index and extinction coefficient as that of the substrate 6 is laminated outside the substrate 6, the multilayer films lower and upper than the light emitting layer 3 are optically equivalent to each other. By converting to a simple single layer film and executing the characteristic matrix calculation, the reflection coefficient and transmission coefficient of light at the interface between the light emitting layer 3 and its upper layer, and the light emitting layer 3 and its lower layer are obtained as effective Fresnel coefficients. The reflection coefficient at the interface is derived.

At this time, in deriving the effective Fresnel coefficient at the interface between the light emitting layer 3 and its upper layer, the jth multilayer film with the number of layers s up to the substrate 6 disposed on the upper layer side of the light emitting layer 3 is selected. The layer characteristic matrix M _j and the multilayer characteristic matrix M are derived from the following equations. In the equation, λ is a set value of the emission wavelength. d _j is a set value of the thickness of the j-th layer. n _j and k _j are set values of the refractive index and extinction coefficient of the j-th layer, respectively. θ _j is the incident angle of light from the j-th layer, and is derived from Snell's law for each layer based on the set value of the light emission angle.

Using this characteristic matrix M, the normalized amplitudes B and C of the electric and magnetic fields are derived from the following equations. In the equation, θ _s is an incident angle of light from the substrate 6.

Based on this result, a reflection coefficient ρ _A that is an effective Fresnel coefficient and a phase change φ _A at the interface between the light emitting layer 3 and a virtual single layer film above the light emitting layer 3 are calculated by the following equations. In the formula, n ₀ and k ₀ are set values of the refractive index and extinction coefficient of the light emitting layer 3, respectively. θ ₀ is the incident angle of light from the light emitting layer 3 and is derived based on the set value of the light emission angle.

Further, in deriving the effective Fresnel coefficient at the interface between the light emitting layer 3 and its lower layer, the multilayer film up to the light reflective electrode 2 disposed on the lower layer side than the light emitting layer 3 is the same as described above. A characteristic matrix calculation is performed for, and a reflection coefficient ρ _B and a phase change φ _B at the interface between the light emitting layer 3 and the hypothetical single layer film below it are calculated.

(T3) Next, based on the set wavelength, using the derived effective Fresnel coefficient as a boundary condition, for the light emitted from the light source 10 to the upper surface side and the lower surface side at the same angle, the multiplexing as shown in the following equation By executing the interference calculation, the energy transmittance T of light emitted from the light emitting source 10 to the outside of the organic EL element is calculated. The energy of light emitted from the organic EL element to the outside is calculated by integrating the energy of light at a set wavelength acquired from the photoluminescence spectrum of the light emitting material with the energy transmittance T of the light. In order to improve the accuracy of the energy of the light emitted from the organic EL element to the outside, the change in the solid angle due to the difference in refractive index between the light emitting layer 3 and the organic EL element is corrected, or the thick substrate 6 is used. You may correct | amend the transmittance | permeability of a part. N ₀ in the following formula is a set value of the refractive index of the light emitting layer 3. θ ₀ is the incident angle of light from the light emitting layer 3 and is derived based on the set value of the light emission angle. d ₀ is the thickness of the light emitting layer 3. Z is the distance from the light emitting source 10 to the interface from the electron transport layer 9 and is derived based on the set value of the position of the light emitting source 10.

  (T4) Next, by executing the characteristic matrix calculation in the same manner as T2 except that the atmosphere 1 is in direct contact with the outside of the substrate 6, the light emitting layer 3 and its upper layer are obtained as effective Fresnel coefficients. The reflection coefficient and transmission coefficient of light at the interface, and the reflection coefficient at the interface between the light emitting layer 3 and its lower layer are derived.

  (T5) Next, based on the energy of the light at the set wavelength obtained from the photoluminescence spectrum of the light emitting material, the effective Fresnel coefficient derived in T4 is used as a boundary condition, and the light source 10 is exposed to the upper surface side and the lower surface side, respectively. For the light emitted at the same angle, the energy of the light emitted from the organic EL element to the outside is calculated by executing multiple interference calculation as in T3.

  (T6) Next, the energy of light guided in the substrate is calculated by subtracting the energy of light calculated in T5 from the energy of light calculated in T3.

  The calculated amount of the light component may be corrected based on the angle characteristics of the region 7 that disturbs the reflection / refraction angle described later. In this case, the organic EL element can be designed more accurately. For example, in the case where only the region 7 is laminated on the substrate 6 in advance, the light is irradiated from the substrate 6 side while changing the incident angle, and the amount of the light component of the emitted light is measured for each incident angle, or the FDTD method, etc. The angle characteristic of the amount of the light component emitted from the region 7 can be derived by performing analysis based on the above, and the amount of the light component can be corrected based on this angle characteristic.

  (T7) Next, the set value of the position of the light emitting source 10 is changed, and the above steps T2 to T6 are repeated. This procedure is repeated until the positions of all the light sources 10 are sequentially set. Here, the position of the light emission source 10 is derived based on the set position of the light emission point and the light emission distribution.

  (T8) Next, the set value of the emission wavelength is changed, and the above steps T2 to T7 are repeated. At this time, the set value of the emission wavelength is sequentially changed, for example, in the range of the visible light wavelength of 380 to 780 nm.

  (T9) Next, the set value of the radiation angle from the light emitting source 10 is changed, and the above steps T2 to T8 are repeated. At this time, the setting value of the radiation angle is sequentially changed within a range of 0 ° to 90 °, for example.

  (T10) Next, the amount of guided component is derived and stored in a memory or various storage media. At this time, when the light energy is set as the amount of the light component in S6, the integral value of the light energy guided in the substrate sequentially calculated in T6 in the procedure of T2 to T9 is guided. Derived as component amount. When the number of photons is set as the amount of light component in S6, the light energy is divided by the value of chν (c: speed of light, h: Planck constant, ν: reciprocal of wavelength). To derive the amount of guided component. Further, when a light beam is set as the amount of light component in S6, the amount of guided component is calculated from the energy of light guided in the substrate sequentially calculated in T6 in the procedure from T2 to T9 based on the CIE standard. Derived based on specific visibility and maximum visibility.

  (S10) Next, the value of the light emitting point position dimension set at this time is compared with the maximum value of the light emitting point position dimension set in S8.

  (S11) If it is determined in S10 that the set value of the light emitting point position dimension is smaller than the maximum value, the set value is changed to a value increased by the step size set in S7, and the electron transport layer The setting value of the thickness of the organic layer 4 correlated with the emission point position dimension such as 9 is changed to a value that matches the set value of the emission point position dimension in the same manner as S8, and then the above S9 (T1 to T10). Repeat the process. As a result, the relationship between the amount of the guided component and the light emitting point position size within the set range of the light emitting point position size is recorded. In S11, in the vicinity of the maximum value of the waveguide component amount, the set value of the light emitting point position dimension is increased by a value smaller than the set step size, so that the amount of light component near the maximum value is detailed. May be derived.

  (S12) If it is determined in S10 that the set value has reached the maximum value, the relationship between the waveguide component amount and the light emitting point position dimension obtained as described above is stored in the memory. Or stored as electronic data in an appropriate storage medium or the like.

  In the process of S11, a combination of the maximum value of the waveguide component amount and the light emitting point position dimension corresponding to the maximum value is derived, and this is stored as electronic data in a memory or an appropriate storage medium. May be saved. At this time, when a plurality of maximum values appear within the set range of the film thickness of the organic light emitting layer 5 due to the light interference effect, for each maximum value, the maximum value and the corresponding light emitting point position dimension Save the combination. In addition, for each local maximum value, a range of the light emitting point position dimension having a constant width (for example, ± 40 nm) centered on the light emitting point position dimension corresponding to the local maximum value, or the amount of waveguide component in this range and the light emitting point position A relationship between dimensions may be derived and stored. These results may be output and displayed on a display device such as a display.

  The relationship between the amount of the waveguide component obtained as described above and the position of the light emitting point is as shown in FIG. 3 in which a region 7 for disturbing the reflection / refraction angle is provided on the substrate 6 of the organic EL element. This is used for designing the thickness of the organic light emitting layer 5 when the waveguide component is taken out. The region 7 for disturbing the reflection / refraction angle is originally reflected at the interface by diffusing light that has reached the interface between the substrate 6 and the outside from the substrate 6 and guided through the substrate 6. A light diffusing layer formed by dispersing translucent fine particles such as silica and alumina in a translucent binder, for example. Can do.

  Here, the amount of the waveguide component is not provided outside the region 7 where the reflection / refraction angle is disturbed, and the substrate 6 is directly exposed to the atmosphere 11. Although this corresponds to the amount of the lost light component, as described above, the amount of the guided component reaches approximately 74% of the amount of the light component reaching the substrate 6 from the light emitting layer 3. For this reason, the amount of light emitted from the organic EL element when the region 7 for disturbing the reflection / refraction angle is provided on the substrate 6 is the amount of light component emitted from the organic EL element when such a region 7 is not provided ( It is governed by the waveguide component amount rather than the output component amount).

  Therefore, if the thickness of the organic light emitting layer 5 is designed using the relationship between the amount of the waveguide component and the position of the light emitting point, the organic EL element can be used when the region 7 for disturbing the reflection / refraction angle is provided. The thickness of the organic light emitting layer 5 can be designed so that the amount of the emitted light component becomes a desired level.

  The thickness of the organic light emitting layer 5 can be designed by adjusting the position of the light emitting point so that the amount of the waveguide component becomes a desired value. The adjustment of the light emitting point position dimension is performed by adjusting the thickness of the organic layer 4 such as the electron transport layer 9 or the like correlated with the value of the light emitting point position dimension to a value corresponding to the desired light emitting point position dimension. Can do.

  Thus, when designing the thickness of the organic light emitting layer 5, the thickness of the organic light emitting layer 5 is designed so that the amount of the waveguide component takes a maximum value or a value in the vicinity thereof. When the region 7 to be disturbed is provided, the amount of light component emitted from the organic EL element can be remarkably improved.

  Here, if the setting range of the light emission point position dimension is wide at the time of optical propagation analysis, not only the first maximum value but also the second maximum value or the third and subsequent maximum values as the maximum value, The relationship with the light emitting point position dimension is also derived. For this reason, the thickness of the organic light emitting layer 5 can be designed so that the amount of the waveguide component takes any one of a plurality of maximum values or a value in the vicinity thereof.

  In addition, the thickness of the organic light emitting layer 5 can be designed so that the waveguide component amount takes a maximum value or its vicinity as described above, and this value takes an appropriate value. The component of light emitted from the organic EL element is designed by designing the thickness of the organic light emitting layer 5 so that the amount of the guided component is sufficiently large from the relationship between the amount of the guided component and the position of the light emitting point. The amount of can be improved.

  Moreover, the light emission point position dimension may be restrict | limited depending on the structure of an organic EL element. As a specific example, since the organic EL element includes a plurality of light emitting layers 3, the range of the light emitting point position dimension for each light emitting point in each light emitting layer 3 of the organic EL element is limited to a certain range. There are cases. Even in such a case, the thickness of the organic light emitting layer 5 can be designed in a wide range as described above. Therefore, each light emitting layer 3 is guided within the limit range of the light emitting point position size. The component amount takes a maximum value or its vicinity, or even if it is not such a value, the waveguide component amount takes a sufficiently large value such as taking the highest value within the limit range, The thickness of the organic light emitting layer 5 can be designed.

  Here, out of the light components emitted from the plurality of light emitting layers 3, if the thickness is designed so that the amount of waveguide components from all the light emitting layers 3 takes a maximum value, the light extraction efficiency is extremely increased. However, if the amount of the guided component from at least one light emitting layer 3 takes a maximum value, it can contribute to the improvement of the light extraction efficiency. Further, even when none of the waveguide component amounts can take the maximum value, the thickness of the organic light emitting layer 5 is set so that the amount of the component of light emitted from the organic electroluminescence becomes a desired one as described above. Can be designed.

  Below, the specific example of the design of an organic EL element is shown.

  As an organic EL element, on a glass substrate 6 having a thickness of 0.7 mm, a light-transmitting electrode 1 having a thickness of 150 nm made of ITO, a hole transport layer 8 having a thickness of 40 nm made of NPD, and 6 rubrenes. A light emitting layer 3 having a thickness of 30 nm made of Alq3 doped by weight%, an electron transport layer 9 made of TmPyPhB of the following [Chemical Formula 1] having a variable thickness, and a light reflective electrode 2 made of Al having a thickness of 80 nm are laminated. Assuming that

  At this time, when the PL spectrum of light energy (radiant flux) of Alq3 doped with 6% by weight of rubrene used for the light emitting layer 3 was measured, it was as shown in FIG. 4, and the peak wavelength of the spectrum was 559 nm. The vertical axis in FIG. 4 indicates the normalized intensity of light energy.

  In addition, the position and emission distribution of the light emitting points in the light emitting layer 3 are such that when Alq3 is used as in this example, the electron mobility in the light emitting layer 3 is about three orders of magnitude higher than the hole mobility. Can be set at the interface between the hole transport layer 8 and the light emitting layer 3, and the light emission distribution can be set as a delta distribution.

  FIG. 5 shows the amount of the guided component of the luminous flux and the light emitting point position dimensions when the light emitting point position dimensions are changed by changing the thickness of the electron transport layer 9 in the organic EL element having the above-described form. The results derived from the above-described Fresnel theory analysis are shown below. The vertical axis in FIG. 5 indicates the relative value of the luminous flux. In this Fresnel theoretical analysis, correction based on the angle characteristics of the region 7 that disturbs the reflection / refraction angle of light is not performed.

  FIG. 5 also shows the relationship between the luminous flux emitted from the organic EL element (emission component amount) and the light emitting point position dimension when the substrate 6 is not provided with the region 7 that disturbs the reflection / refraction angle, and the light guide point size. The relationship between the sum of the wave component amount and the emission component amount and the light emitting point position dimension is also shown.

  The relationship between the amount of the emitted component and the position of the light emitting point is determined based on the integrated value of the energy of light derived at T3 in T10 without performing steps T4 to T6 in the flow of optical propagation analysis. It is obtained by deriving.

  Further, the sum of the amount of the guided component and the amount of the emitted component is the amount of the component of the light emitted from the organic EL element when all the light reaching the substrate 6 from the light emitting layer 3 is emitted from the organic EL element. This corresponds to the maximum value of the amount of light components emitted from the organic EL element when the region 7 for disturbing the reflection / refraction angle is provided.

  As shown in the figure, both the amount of the guided component and the amount of the outgoing component change as the emission point position dimension increases, and each takes a plurality of local maximum values. There is a deviation in the value of the light emitting point position dimension taking

  That is, for the emission component amount, the first maximum value appears when the emission point position dimension is 70 nm, and the second maximum value appears at 250 nm. However, for the waveguide component amount, the first emission point position dimension is 100 nm. A second maximum appears at a maximum of 340 nm. For this reason, by designing the thickness of the organic light-emitting layer 5 so as to take the maximum value of the waveguide component amount based on the relationship between the waveguide component amount and the light emitting point position dimension, it is possible to perform the design based on the emission component amount. The luminous flux emitted from the organic EL element provided with the region 7 that disturbs the reflection / refraction angle of light can be increased. For example, when the thickness of the organic light emitting layer 5 is designed so that the waveguide component amount takes the second maximum value, the thickness of the organic light emitting layer 5 is designed so that the emission component amount takes the second maximum value. Compared with the case of the above, the sum of the waveguide component amount and the output component amount is increased 1.08 times. In addition, when the amount of guided component takes the second maximum value, the amount of outgoing component is greatly reduced. Therefore, when the thickness of the organic light emitting layer 4 is designed based on the amount of outgoing component, It is impossible to design the thickness of the organic light-emitting element layer 4 so that the amount of the guided component takes a maximum value, and the luminous flux emitted from the organic EL element provided with the region 7 that disturbs the reflection / refraction angle of light is used. It can be seen that it cannot be increased sufficiently.

  Although the case where a light beam is used as the amount of the light component is described here, the relationship between the amount of the waveguide component and the light emitting point position size is similarly applied when the number of photons is used as the amount of the light component. Is used to design the thickness of the organic light-emitting layer 5 so that the number of photons or quantum efficiency of the emitted light when the region 7 for disturbing the reflection / refraction angle is provided on the substrate 6 of the organic EL element is as desired. In this case, the thickness of the organic light emitting layer 5 can be designed over a wide thickness range of the organic light emitting layer 5. Similarly, when light energy (radiant flux) is adopted as the amount of light component, the relationship between the amount of waveguide component and the position of the light emitting point is similarly utilized to reflect on the substrate 6 of the organic EL element. The thickness of the organic light-emitting layer 5 can be designed so that the energy of the emitted light when the region 7 that disturbs the refraction angle is provided becomes a desired level. Thus, the thickness of the organic light emitting layer 5 can be designed.

  It will be verified below that the relationship between the waveguide component amount derived in this way and the light emitting point position size reflects the amount of light component emitted from the actual organic EL element.

  FIG. 7 shows a result of actually producing an organic EL element having the above-described configuration and measuring the amount of the waveguide component, the amount of the outgoing component, and the sum of the amount of the waveguide component and the amount of the outgoing component in this organic EL element. The vertical axis in FIG. 7 indicates the relative value of the luminous flux. This measurement was performed as follows.

  First, a plurality of organic electroluminescent elements having the same configuration as that assumed for deriving the relationship shown in FIG. 5 are manufactured by varying the thickness of the electron transport layer 9.

  For each organic EL element, a hemispherical lens 12 is provided on the surface of the substrate 6 as shown in FIG. The hemispherical lens 12 is formed of the same material as that of the substrate 6 and is a lens in which one surface side is a flat surface and the other surface side is a spherical surface. The hemispherical lens 12 is provided on the substrate 6 so that its plane is in close contact with the surface of the substrate 6.

  In this state, the organic EL element emits light, the light is emitted from the hemispherical lens 12, and the emitted light is measured using an integrating sphere. At this time, since the refractive index of the substrate 6 is about 1.5, when the hemispherical lens 12 is not provided, the critical angle of light emitted from the substrate 6 to the atmosphere 11 side is about 42 ° according to Snell's law. Light 23 with θ smaller than the critical angle is emitted to the atmosphere 11 side, but light 23 with incident angle θ larger than the critical angle is totally reflected at the interface between the substrate 6 and the atmosphere 11 and guided through the substrate 6. To do. However, the light 23 that should be totally reflected by providing the hemispherical lens 12 is also incident on the hemispherical lens 12. Since the light 23 incident on the hemispherical lens 12 is emitted from the spherical surface side, the incident angle from the hemispherical lens 12 to the atmosphere 11 is reduced, and most of the light 23 incident on the hemispherical lens 12 is emitted from the spherical surface side to the atmosphere 11. be able to. For this reason, the amount of the light component emitted from the hemispherical lens 12 corresponds to the sum of the waveguide component amount and the emission component amount.

  Similarly, the light emitted from the organic EL element was measured without the hemispherical lens 12 provided. The amount of the light component emitted at this time corresponds to the amount of the emitted component.

  Further, the waveguide component amount is calculated by subtracting the emission component amount from the sum of the waveguide component amount and the emission component amount measured as described above.

  5 and FIG. 7 are compared, the waveguide component amount, the outgoing component amount, and the sum of the guided component amount and the outgoing component amount shown in FIG. The relationship is very close to the actual measurement result shown in FIG. 7, and based on the relationship between the sum of the waveguide component amount and the emission component amount derived in the optical propagation analysis and the light emitting point position dimension, It can be confirmed that the EL element can be designed accurately.

It is a flowchart which shows an example of embodiment of this invention. It is sectional drawing which shows an example of the organic electroluminescent element in which the area | region which disturbs a reflection and a refraction angle is not provided. It is sectional drawing which shows an example of the organic electroluminescent element provided with the area | region which disturbs reflection and a refraction angle. It is a graph which shows the measurement result of the photoluminescence spectrum of Alq3 which doped 6 weight% of rubrenes. It is a graph which shows an example of the relationship between the light emission point position dimension derived | led-out by conducting an optical propagation analysis, and the sum of guided light quantity, the emitted light quantity, the sum of guided light quantity and emitted light quantity. It is sectional drawing which shows an example of the organic electroluminescent element provided with the hemispherical lens. It is a graph which shows an example of the relationship between the light emission point position dimension obtained by actual measurement, the sum of the light quantity of guided light, the quantity of outgoing light, the quantity of guided light and the quantity of outgoing light.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Light-transmissive electrode 2 Light-reflective electrode 3 Light emitting layer 4 Organic layer 5 Organic light emitting layer 6 Substrate 7 Area where reflection / refraction angle is disturbed

Claims (4)

An organic light emitting layer including a light emitting layer and another organic layer is provided between the light transmissive electrode and the light reflective electrode, and light is transmitted to the surface of the light transmissive electrode opposite to the organic light emitting layer. A method for designing an organic electroluminescent device comprising a conductive substrate,
Each thickness, refractive index and extinction coefficient of the substrate, light transmissive electrode, light emitting layer and other organic layers, and the refractive index and extinction coefficient of the light reflective electrode, and the light emitting material in the light emitting layer By performing the optical propagation analysis using the photoluminescence spectrum, the position of the light emitting point in the light emitting layer and the light emission distribution as factors,
The relationship between the amount of the light component guided inside the substrate and the dimension from the light emitting point to the surface of the light reflective electrode is derived, and based on this relationship, the reflection / refraction angle is given to the substrate. A design method of an organic electroluminescence element, wherein the thickness of an organic light emitting layer is designed when a region to be disturbed is provided.   2. The method of designing an organic electroluminescence element according to claim 1, wherein the amount of the light component is a light beam in consideration of visibility.   The method of designing an organic electroluminescent element according to claim 1, wherein the amount of the light component is the number of photons.   The method for designing an organic electroluminescent element according to claim 1, wherein the amount of the light component is energy.

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