JP2008078039A - Optical functional thin film element, manufacturing method thereof, and article using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical functional thin film element in which the light emission performance of an optical functional thin film element is enhanced by suppressing loss as much as possible when light generated inside the element is radiated to the outside. An article using an optical functional thin film element that can be used as a display body or an illumination body is provided. Furthermore, the present invention provides a method for producing an optical functional thin film element that can easily provide an optical functional thin film element having excellent light emitting performance.
An optical functional thin film element (organic EL element 1) in which an optical functional thin film (light emitting layer 4) is sandwiched between a first electrode (anode 1) and a second electrode (cathode 5). , Between the first electrode (anode 1) and the optical functional thin film (light emitting layer 4), between the optical functional thin film (light emitting layer 4) and the second electrode (cathode 5). Refractive index adjustment layers 6, 7, formed by performing a refractive index matching process on at least one of the second interface and the third interface between the first electrode (anode 1) and air. 8 is provided.
[Selection] Figure 1

Description

  The present invention relates to an optical functional thin film element applied to various uses such as a display, an illuminator, and a light source for optical communication, a manufacturing method thereof, and an article using the same.

  Recent advances in information technology and IT technology have greatly accelerated the development of light emitting elements that emit light (eg, luminescence elements, lasers, etc.). In each element, it is important that the light generated inside the element is efficiently emitted to the outside and then emitted to the outside for a long period of time. Research is underway to increase the extraction efficiency (the rate at which the light generated inside the element is emitted outside without loss).

  The light-emitting element is applied to various displays, meters, signals, indicators, illumination bodies, light sources for optical communication, etc., taking flat TV as an example, a plasma display with high brightness and wide viewing angle, Methods such as organic electroluminescence (EL) displays and field emission displays are being actively studied. In addition to TV, it is also used as a display for personal computers, a flat panel display such as navigation for automobiles, or as a mobile phone, electronic paper and mobile personal computer with the progress of mobile.

  The light-emitting element basically has a sandwich type configuration in which an anode and a cathode are arranged on both sides of a light-emitting layer. In order to take out light generated inside the element, A light-transmitting electrode (transparent electrode) is used for either the anode or the cathode. In light-emitting elements, the movement of charge carriers (electrons and holes) at the bonding interface between the anode and the light-emitting layer and the bonding interface between the cathode and the light-emitting layer is actively used to develop an electronic or optical function. ing.

  As a typical example of a light emitting element, an organic electroluminescence (EL) element which has recently been attracting attention is given, and its basic configuration and operation will be described.

  An organic electroluminescence (EL) device has a transparent electrode (for example, ITO: Indium Tin Oxide) that serves as an anode on a transparent substrate (for example, glass or resin), and a light emitting layer (photo functional thin film) on the anode. And a multilayer laminated structure in which electrodes (Mg / Ag) serving as cathodes are respectively disposed, and light is emitted by connecting a power source between the anode and the cathode and applying a voltage. In addition, although it was set as the organic electroluminescent element in which a base material exists here, you may make it the structure without a base material.

  In the organic electroluminescence element, holes are injected from the anode side toward the light emitting layer by overcoming the height Δφ of the potential barrier at the junction interface by the voltage applied between the anode and the cathode by the power source, and the electrons are injected into the cathode. Injected from the side toward the light emitting layer, exceeding the height Δφ of the potential barrier at the junction interface. The injected holes and electrons recombine to emit light, and the emitted light is emitted from the anode (transparent electrode) side to extract light to the outside of the light emitting element.

  However, even if light is efficiently generated inside the light emitting layer of the organic electroluminescence element, there are cases where light loss occurs at each interface and light cannot be efficiently extracted outside through the substrate and the anode.

  Light loss occurs when light generated in the light emitting layer is guided or propagated and guided to the end portion of the element and leaks due to the total reflection effect inside the light emitting layer. Also in the electrodes (anode, cathode) and base material, light loss occurs due to waveguiding and leakage at the end of the element due to the total reflection effect, as in the light emitting layer. Furthermore, in addition to leakage of light from the end portion of the element, light may be absorbed during waveguide to cause light loss.

  The above-described total reflection effect is mainly caused by the refractive index difference Δn at the interface of each layer of the organic electroluminescence element. This refractive index difference Δn is caused by the difference in refractive index between the materials of two adjacent layers or electrodes. Arise.

Taking a typical material as an example, the difference in refractive index at each interface will be described. The refractive index n of the substrate (glass) is 1.5, the refractive index n of the anode as the first electrode (ITO) is 2.0, the refractive index n of the light emitting layer (Alq ₃ ) is 1.6, and the second The refractive index n of the electrode is 2.0, and the refractive index n of air is 1.0. The refractive index referred to here generally refers to the value at the D line (wavelength 589 nm) (hereinafter simply referred to as the refractive index). When the refractive index difference Δn is calculated, the refractive index difference Δn exists from about 0.4 to 0.5 at each interface (first interface to fourth interface).

  Thus, when there is a refractive index difference Δn at each interface, light loss occurs due to the total reflection effect described above, and the light emission efficiency is lowered. Therefore, it is desirable to reduce the light loss generated inside the light emitting layer. It was.

  In order to reduce the refractive index difference Δn, there has been proposed an organic EL element in which a low refractive index silica airgel layer (n = 1.1) is inserted between an anode and a substrate.

Further, an organic EL element is disclosed in which a mesa-shaped substrate layer and a buffer layer are disposed on a base material, and an anode, a light emitting layer, and a cathode are sequentially stacked on the substrate (see, for example, Non-Patent Document 1). . According to this organic EL element, the light extraction efficiency is maximized by setting the taper angle between the mesa-type substrate layer and the buffer layer to about 35 ° to 40 °.
"High-brightness, high-efficiency, and long-life technology for organic EL displays", pages 113-114, published by Technical Information Association

  However, in the case of an organic EL element in which a low refractive index layer is inserted into the interface on the light extraction side by the silica airgel described above, for example, the sol-gel method is used, so that the layer is formed only on a limited substrate such as glass. It had the problem that it could not be formed. Moreover, if it was difficult to form a uniform silica airgel layer uniformly, there was a possibility of coloring or light transmittance being lowered. In addition, when such a low refractive index layer is inserted at the interface, a potential barrier is formed, and smooth movement of electrons and holes is hindered, resulting in a decrease in luminous efficiency and a significant decrease in device lifetime. Had.

  Further, when the mesa-shaped substrate layer and the buffer layer are arranged on the base material, not only the manufacturing process steps are complicated, but also a high-precision processing step is required. Further, even if such a fine structure is formed, the surface of the fine structure becomes dirty or scratched, and there is a risk that the light extraction efficiency may be drastically reduced. Furthermore, when such a microstructure is formed on a relatively high strength and flat substrate such as glass, it does not matter so much, but when the substrate is a flexible resin, There was a risk that the dimensions of the microstructure itself would change due to changes in humidity.

  As explained above, organic EL devices with a low refractive index layer, or organic EL devices with a mesa-type microstructure on the substrate, are effective in increasing the light extraction efficiency, but have been put to practical use. In doing so, it had various problems as described above.

  The present invention has been made to solve the above-described problems. That is, the optical functional thin film element of the present invention has an optical function in which an optical functional thin film is sandwiched between a first electrode and a second electrode. A first interface between the first electrode and the optical functional thin film, a second interface between the optical functional thin film and the second electrode, and the first electrode The gist of the invention is to provide a refractive index adjustment layer formed by performing a refractive index matching process on at least one of the third interfaces between the air and the air.

  In the method for producing an optical functional thin film element of the present invention, at least one of the surfaces of the first electrode, the second electrode, and the optical functional thin film is immersed in an acid solution or an alkali solution, and the immersed surface is purified with pure water. The gist is to rinse and dry to form a refractive index adjusting layer, and to join the first electrode, the second electrode, and the optical functional thin film to form an optical functional thin film element.

  The gist of the article of the present invention is that the article is either a display body or an illuminating body using the above-described optical functional thin film element.

  According to the optical functional thin film element of the present invention, when light generated inside the element is radiated to the outside, loss can be suppressed as much as possible to improve light emitting performance.

  According to the method for producing an optical functional thin film element of the present invention, an optical functional thin film element having excellent light emitting performance can be easily obtained.

  According to the article of the present invention, it can also be used as a display body or a lighting body.

  Hereinafter, an optical functional thin film element according to an embodiment of the present invention, a manufacturing method thereof, and an article using the same will be described with reference to the accompanying drawings.

  FIG. 1 is a cross-sectional view of an organic EL element 1 which is an example of an optical functional thin film element according to an embodiment of the present invention. In the organic EL element 1, an anode 3 as a first electrode, a light emitting layer 4 as a functional thin film, and a cathode 5 as a second electrode are sequentially laminated on a substrate 2 to form a substrate 2 Refractive index adjusting layers 6, 7, and 8 are disposed on the surface, between the substrate 2 and the anode 3 and between the anode 3 and the light emitting layer 4, respectively. A power source 9 is connected to the anode 3 and the cathode 5 so that a voltage can be applied.

As the anode 3, it is preferable to use a material that is light transmissive and can easily inject holes when a voltage is applied. If hole injection is easy, SnO ₂ (other than ITO (indium tin oxide)) can be used. An inorganic oxide such as tin oxide), ZnO (zinc oxide), or FTO (F-doped tin oxide) may be used, or an inorganic-organic composite system or an organic transparent conductor described later may be used. As the cathode 5, it is preferable to use a so-called low work function material that reflects light and easily injects electrons. For example, Mg / Ag or Al may be used. In this way, after the light is incident from the anode 3 side, the light generated from the light emitting layer 4 is reflected from the cathode 5 side, whereby light can be emitted from the anode 3 side.

  In the organic EL element 1 shown in FIG. 1, the refractive index adjustment layers 6, 7, and 8 are formed at three locations. However, the refractive index adjustment layers 6, 7, and 8 may not be disposed at all three locations. In the case where the refractive index difference between two adjacent layers is large, the refractive index adjustment layers 6, 7, and 8 are preferably arranged at the interface between the two layers. By forming the refractive index adjustment layers 6, 7, and 8 in this way, the light generated inside the organic EL element is guided to the end by light confinement by total reflection at each interface located in the light extraction direction. Leakage and light loss due to absorption can be reduced as much as possible. Furthermore, since the refractive index adjustment layers 6, 7, and 8 are layers whose refractive index is adjusted by processing on any surface of the electrode (anode, cathode) or light emitting layer, a new layer is formed. No need to insert.

  Moreover, although the example which takes out light from the anode 3 side was shown in this figure, by using the transparent conductive film (for example, ITO (Indium Tin Oxide)) which has a light transmittance for the anode 3 and the cathode 5, both of them are used. Light can be extracted from the electrodes 3 and 5 side, and can be used for a transparent element or a transparent display.

  Next, a method for forming the refractive index adjustment layers 6, 7, 8 will be described. This forming method is roughly classified into two types.

  In the first method, the refractive index adjustment layers 6, 7, and 8 having different refractive indexes are formed by mixing two kinds of materials of adjacent layers forming an interface for arranging the refractive index adjustment layer in an appropriate ratio. It is a method to do.

Taking the organic EL device 1 shown in FIG. 1 as an example, ITO (refractive index n = 2.0 at a wavelength of 589 nm) as an anode 3 and Alq ₃ (refractive index n = at 589 nm as a light emitting layer 4). 1.6) is laminated, and vacuum heating is performed near the glass transition temperature (79 ° C.) of Alq ₃ , and high-energy UV light or an electron beam is irradiated to diffuse two types of materials present at the interface. When two kinds of materials are diffused, it is possible to change the refractive index at the interface from the single refractive index of each material according to the diffusion state of both. As described above, since the refractive index n of ITO is 2.0 and the refractive index n of Alq ₃ is 1.6, the refractive index n of the two is in the range of 1.6 to 2.0. The rate can be adjusted. In addition, due to mutual diffusion by heat, light, or electron beam, the diffusion layer apparently formed at the interface is extremely thin (about 0.1 to about several nm), and a voltage is applied between the anode 3 and the cathode 5. Even in this case, the formation of a new potential barrier or the movement of electrons and holes based thereon is not greatly affected. However, since the anode 3 or the light emitting layer 4 itself is also exposed to thermal or light / electron energy, the film quality (crystallinity, orientation, surface morphology) is also affected. It is necessary to pay sufficient attention to the physical property values of the light emitting layer 4 and the refractive index matching processing conditions.

  The second method is to immerse the layers on both sides that form the interface for forming the refractive index adjusting layer with an acid solution or an alkaline solution, rinse with pure water, and then dry, and then remove the contained water to adjust the refractive index adjusting layer. It is a method of forming. Taking the organic EL element 1 shown in FIG. 1 as an example, the refractive index adjustment layer with respect to the surface of the substrate 2, the interface between the substrate 2 and the anode 3, and the interface between the anode 3 and the light emitting layer 4. Refractive index adjustment processing for forming 6, 7, 8 is performed.

Here, the acid solution or the alkali solution is not particularly limited, and sulfuric acid (H ₂ SO ₄ ), hydrochloric acid (HCl), perchloric acid (HClO ₃ ), nitric acid (HNO ₃ ), acetic acid (Ch ₃ COOH) ) Or an alkaline solution such as sodium hydroxide (NaOH), ammonia (NH ₃ ), and potassium hydroxide (KOH) can be used.

  The degree of change in the value of the refractive index by the acid solution or the alkaline solution is determined by the refractive index matching processing conditions (type of processing solution, such as the type or thickness of the material to be the processing surface for adjusting the refractive index, the surface roughness, etc. , Concentration, temperature, immersion time, etc.) are closely related, but cannot be determined uniquely. However, the higher the concentration of the solution at room temperature, the shorter the refractive index in a shorter time than the untreated refractive index. I found that I can do it.

  Figure 2 shows the case where an inorganic transparent conductor (ITO) and an organic transparent conductor (PEDOT / PSS (= 1/6) film) used as the anode 3 are immersed in a sulfuric acid solution or not. The change in refractive index was examined by conducting a comparative experiment.

  ITO and PEDOT / PSS transparent conductor films are both coated on a quartz glass substrate, ITO is formed by sputtering, and PEDOT / PSS (= 1/6) film is formed by spin coating. The thicknesses of the ITO film and the PEDOT / PSS film were both adjusted to 200 nm.

When these transparent conductor films are immersed in a sulfuric acid solution, the sulfuric acid solution has a concentration of 1 N, a temperature of room temperature, an immersion time of 600 seconds, and is immersed in a sulfuric acid solution, followed by rinsing with pure water. Drying was performed for a minute.
Then, using an optical thin film measurement system (Film Tek3000, manufactured by Scientific Computing International), the transmission spectrum and reflection spectrum of the quartz glass alone and the transparent conductive film / quartz glass are measured simultaneously, respectively. The rate n was calculated.

  As is clear from FIG. 2, the refractive index n of the untreated ITO thin film at a wavelength of 589 nm was 2.0. However, when treated with a sulfuric acid solution, the refractive index n becomes 1.7 at the same wavelength, which can be reduced by 0.3. found. Furthermore, it was found that the untreated PEDOT / PSS thin film also has a refractive index n of 1.43 to 1.33, which is 0.1 smaller. The same experiment was conducted on the electrodes 3 and 5 or the light emitting layer 4 which are other types of transparent conductive films. In each case, when treated with an acid solution or an alkali solution, refraction was observed. It was found that the rate n was small.

The reason why the refractive index n of the transparent conductive film 3 or 5 or the light emitting layer 4 is reduced by the acid treatment or alkali treatment is not clear, but the anode 3 or the cathode 5 and the light emitting layer 4 On the other hand, when immersion treatment is performed with an acid solution or an alkali solution, for example, in an acid treatment (H ₂ SO ₄ , HCl, HNO _3, etc.), protons (H ₊ ) are replaced with a part of those constituent substances. Can be considered. Considering the case of treatment with H ₂ SO ₄ as the acid, the anode 3 is doped with SO _{4− and} the reaction of the following formula (1) proceeds to produce H ₂ O. It is thought that the amount decreases with heat treatment, and the amount of OH ^- ions decreases accordingly.

R-SO ₃ Na + H ₂ SO ₄ → (R-SO ₃ H + H ₂ O) + Na ₂ SO ₄ ... Formula (1)
As a basis for such an estimation, “time-of-flight type 2” is applied to the case where the electrode (PEDOT / PSS) formed on the quartz glass substrate is not treated and is acid-treated with H ₂ SO _4. Next-order ion mass spectrometry (TOF-SIMS analysis) "investigated the behavior of OH ^- ions. FIG. 3 (a) shows the results when untreated, and FIG. 3 (b) shows the results when acid treatment is performed with H ₂ SO ₄ . As is apparent from FIGS. 3 (a) and 3 (b), it has been found that the acid treatment with H ₂ SO ₄ significantly reduces the amount of OH ⁻ ions.

  As described above, it is considered that the refractive index is reduced by treatment with acid or alkali as compared with the refractive index in the untreated state due to the substitution action with the molecule or atom of the counterpart substance and the introduction action into the defect portion. It has been found that this tendency can be obtained not only when the acid treatment is performed but also when the alkali treatment is performed.

  Although the refractive index n at a wavelength of 589 nm has been described with reference to FIG. 2, the wavelength dependence of the refractive index of the surface that has been further acid-treated or alkali-treated, that is, the refractive index dispersion was examined in detail.

  FIG. 2 also shows the wavelength dependence of the refractive index for the three types of samples, the ITO thin film, quartz glass, and PEDOT: PSS thin film described above, and the change width of the refractive index n differs depending on the sample. It has been found that the refractive index n decreases as the wavelength λ increases. As described above, in general, the refractive index n is expressed at a wavelength called a so-called D-line having a wavelength of 589 nm, and when the wavelength dependence of the refractive index n is intensively studied, the following two characteristics are found to exist. did.

  The first characteristic is that the wavelength dependence of the refractive index n differs slightly depending on the type of material, that is, there is a difference in the decrease in the refractive index n even when the wavelength λ increases (in other words, the slope of the dispersion curve). Is different). For example, the wavelength dependence of the refractive index of quartz glass is reduced in the visible light region, but the dependence of the PEDOT: PSS thin film is increased.

The second characteristic is that the effect of acid treatment or alkali treatment varies greatly depending on the type of material. For example, in the ITO thin film, the refractive index n when not treated is 2.0, the refractive index n after acid (H ₂ SO ₄ ) treatment is 1.7, and the change width becomes large as Δn≈0.3, but PEDOT : The refractive index n of the unprocessed PSS thin film is 1.42, the refractive index n after the acid (H ₂ SO ₄ ) treatment is 1.31, and the change width is only a slight change of Δn≈0.11. I couldn't. Based on these examination results, it has been found that it is preferable to define as follows.

That is, at the first interface, at least one of the anode 3 or the light emitting layer 4 subjected to the refractive index matching treatment shows the wavelength dependency of the refractive index in the visible light region, and the anode 3 shows the wavelength dependency curve of the refractive index. And the refractive index of the light emitting layer 4 at a wavelength of 380 nm are n ₁ (380) and n _f (380), and the refractive index at a wavelength of 780 nm is n ₁ (780) and n _f (780), respectively. The difference {n ₁ (380) −n _f (380)} between the two at 380 nm and the difference {n ₁ (780) −n _f (780)} between the two at the wavelength of 780 nm are | {n ₁ (380) −n It is preferable to satisfy _f (380)} | ≦ 0.3 and | {n ₁ (780) −n _f (780)} | ≦ 0.3. Thereby, the refractive index difference Δn in the necessary wavelength region can be minimized, and the light loss at the interface can be reduced.

  Hereinafter, the description will be given focusing on the base material (quartz glass) and the anode (PEDOT: PSS thin film) shown in FIG. The wavelength dependence curve of the refractive index of quartz glass is almost constant. On the other hand, the same curve of the PEDOT: PSS thin film (untreated) shows a large wavelength dependence, with a refractive index n = 1.60 at a wavelength of 380 nm and a refractive index n = 1.30 at a wavelength of 780 nm. When the wavelength λ at which the wavelength dependence curves of the refractive indexes of the two intersect (refractive index Δn = 0) is read, the wavelength is 690 nm, and the color is a red region. The light emitted from the light emitting layer 4 has a refractive index difference Δn≈0 in the vicinity of the wavelength λ = 690 nm so that the light loss at the interface is small if the color is from red near this wavelength to the near infrared region. , It seems that it does not matter so much.

  However, in general, in order to enable three types of color development of red (R), green (G), and blue (B), a light emitting element provided with a light emitting layer 4 is desired. However, it is not preferable to consider the light loss at the interface only from the viewpoint of considering the light emission luminance balance of primary colors. For this reason, it is preferable that the wavelength dependence curves of the refractive indexes of the anode 3 and the light emitting layer 4 can be arbitrarily crossed in the visible light region (wavelength 380 nm to 780 nm).

FIG. 4 shows a wavelength dependence curve of the refractive index when the anode (untreated PEDOT: PSS thin film) is subjected to immersion treatment using a sulfuric acid solution (H ₂ SO ₄ ). At this time, the immersion treatment was performed by setting the concentration of the sulfuric acid solution to three levels of 0.01N, 0.1N, and 1N, the temperature at room temperature, and the treatment time at 600 seconds. As is clear from FIG. 4, when the anode is not treated with respect to the wavelength dependency curve of the base material (quartz glass), it intersects at the point (a) near the wavelength of 660 nm (red), but the sulfuric acid solution concentration Are changed from 0.01 N to 1 N at (b) near the wavelength of 590 nm (red), (c) near the wavelength of 530 nm (green), and (n) near the wavelength of 470 nm (blue) ( d) To the point, the intersection is shifted to the short wavelength side, and it has been found that the refractive index difference Δn between the two is as small as possible at these three wavelengths. This means that the refractive index difference Δn between the anode 3 and the light emitting layer 4 is reduced in the visible light region by changing the concentration of the sulfuric acid solution. In addition, although the example which changed the density | concentration of the acid solution was shown here as conditions for refractive index matching processing, even if other processing conditions (kind of a processing solution, temperature, time, etc.) are changed and refractive index is made small. good.

Further, based on the above result, as shown in FIG. 5, the refractive index matching-treated anode 3 and the wavelength dependence curve of the refractive index of the light emitting layer 4 intersect in the visible light region, and the wavelength of the intersection is λ _1, and when the spectrum peak wavelength of the emission emitted from the light-emitting layer shown in FIG. 6 and _{λ em, | λ 1 - λ} em | it is important to satisfy ≦ 100 nm. The basis for this will be described with reference to FIG.

FIG. 5 shows a wavelength dependence curve of quartz glass (base material) extracted from FIG. 4 and an anode (PEDOT: PSS thin film) treated with sulfuric acid at a treatment concentration of 0.1 N. Both curves intersect at a wavelength of about 530 nm. The refractive index difference Δn between the two is almost eliminated (Δn≈0). On the other hand, in the case of the organic El element having no substrate shown in FIG. 1, the light emission layer 4 has a spectral peak (wavelength λ _em ) at the wavelength λ _{1 from} which there is almost no difference in refractive index Δn as described above. By adjusting so as to become, it becomes possible to minimize the light loss at the interface between the anode 3 and the light emitting layer 4.

Incidentally, the anode 3 having a refractive index matching process has been performed, the wavelength lambda ₁ to wavelength dependency curve of the refractive index of the light-emitting layer 4 intersect, the difference between the wavelength lambda _em of the emission spectrum peak is emitted from the light-emitting layer 4 | lambda _{In 1} −λ _em |, the light interference effect based on the difference in refractive index Δn between the two becomes remarkable, and the aimed emission color cannot be obtained. For this reason, the difference between the two is preferably as small as possible, and preferably satisfies | λ ₁ −λ _em | ≦ 100 nm. This is shown in FIG. As shown in FIG. 7, when the magnitude of | λ ₁ −λ _em | exceeds 100 nm, the emission spectrum peak wavelength λ _{em on} the vertical axis shifts to the short wavelength side by 10 nm or more, and changes in color with human eyes. It becomes a perceived level and becomes unpreferable as a light emitting element. Therefore, by setting | λ ₁ −λ _em | in this range, the refractive index difference Δn at a certain wavelength at each interface is extremely small, and the spectral peak wavelength of light emitted from the light emitting layer in the vicinity of the wavelength is further reduced. λ _em is matched as much as possible.

  A CIE (International Commission on Illumination) chromaticity diagram can be used as a method for more quantitative evaluation of sensory evaluation by the human eye. By plotting the tristimulus data into a chromaticity diagram, it shows what kind of color it is, and it is quantified from the reflection spectrum data that is the color sense and physical quantity seen by human eyes. (For details, see, for example, Ohm: Lighting Handbook, page 60).

FIG. 8A shows a chromaticity diagram, and FIG. 8B shows an explanatory diagram. As is clear from the explanatory diagram of FIG. 8B, the outside of the horseshoe-shaped curve is the wavelength axis (λ _{em in} this application) representing “hue” which is one of the three attributes of color. In consideration of human visual sensitivity (recognition of color change), the wavelength increment is 20 nm. In FIG. 8 (a), λ _em = 520 nm and λ _em = 540 nm are plotted, but it was found that when Δλ _em = ± 10 nm (therefore, the change width is 20 nm), it is recognized as a color change. As described above, in a state where the change width Δλ _em = ± 10 nm is not satisfied, when the light emitting element is finally used as a display body, color unevenness or a color difference from the actual product becomes remarkable, and the merchantability is significantly impaired. It turned out that.

  Next, the constituent material of the optical functional thin film element typified by the organic EL element 1 will be described.

  The material for the functional thin film layer (light emitting layer 4) needs to be selected in consideration of processability (fibrosis) or various light emitting performance (desired emission color, emission luminance, emission lifetime, etc.). From the viewpoint of practicality, a π-conjugated material is preferable. Here, the π-conjugated material means a molecule in which a single bond and a double bond are connected repeatedly for a long time like benzene, and has the property that π electrons are easily taken out with relatively small energy and are easy to move. (Kasumi Yoshino, “The story of organic EL”, page 23, Nikkan Kogyo Shimbun). By forming the functional thin film layer (light emitting layer) from a π-conjugated material, not only functions as an element can be obtained, but also various types of wet processes including printing that enables low-temperature processes, large areas, and low costs. It becomes possible to make an element by the method. π-conjugated materials include quinolinol derivatives, fluorene derivatives, phthalocyanine derivatives, triphenyldiamine derivatives, polyparaphenylene derivatives, distyrysarylene derivatives, oxadiazole derivatives, pyrazoline derivatives, polythiophene derivatives, poly (N-alkylcarbazole) derivatives It is preferable to use one kind selected from the group of polyphenylacetylene derivatives, polyphenyleneethynylene derivatives and polyphenylenebutadinylene derivatives, or a mixture containing one kind selected from these.

  The first electrode (anode 3), the optical functional thin film, and the second electrode (cathode 5) are preferably materials that are soluble in water or a solvent. This is because it is generally difficult to heat-melt π-conjugated materials, so it is difficult to apply ordinary wet thin film formation techniques (eg spin coating, casting, dipping, LB film method, printing method, etc.) Because. For this reason, by using a material soluble in water or a solvent, which will be described later, the refractive index matching treatment at each interface and the film formation of each layer can be consistently handled by a wet process, and various wet thin film formation technologies As a result, a target optical functional thin film element can be obtained. As the solvent, in addition to aprotic solvents such as nitrobenzene, propylene carbonate, and acetic anhydride, proton solvents such as methanol and ethanol, or dilution solvents such as ethyl, toluene, and xylene can be used. The solvent is not limited to the above.

As a material of the first electrode (anode 3) and the second electrode (cathode 5), at least one of them is doped polypyrrole (doped Polypyrrole) from the viewpoint of ensuring conductivity and light transmittance as an electrode function. At least selected from doped polyaniline, doped polythiophene, doped polyacetylene, doped polyisothianaphtene and derivatives thereof One kind may be used. The doping material (also referred to as dopant) varies depending on the type of conductive polymer used, whether it aims for donor properties (electron-depriving property) or acceptor properties (electron-providing property), but conductive polymer polythiophene. B ₁₀ Cl _2-10 , Bu ₄ NBF ₄₋ , ClO _4−, etc. can be used to make the material acceptor, and Li ₊ , K _+, etc. can be used to make the material acceptor. By using these doping materials under appropriate conditions, the conductivity σ = 10 ₂ S / cm and the total light transmittance in the visible light region (see, for example, JIS K6911) has a light transmittance of about T = 78%. The electrodes (the anode 3 and the cathode 5) can be provided.

Furthermore, as the first electrode (anode 3) and the second electrode (cathode 5), at least one material selected from polyethylene dioxythiophene (PEDOT), polypropylene oxide (PO), and derivatives thereof is used. May be. These materials are particularly excellent in water dispersibility, and it is relatively easy to form a thin film while ensuring conductivity and total light transmittance. For example, a composite in which polyethylenedioxythiophene (PEDOT) and polystyrene sulfonic acid (PSS) are dispersed at an appropriate ratio (eg, 1/6) has a conductivity of σ = 10 ₃ S / cm and a total light transmittance. It is also possible to ensure T = 82%, which is more preferable as an electrode having optical transparency.

  The refractive index matching processing method has already been described above, but will be specifically described with reference to the organic EL element 1 shown in FIG.

Quartz glass as a light-transmitting substrate, polydioxythiophene (PEDOT) / polystyrene sulfonic acid (PSS) thin film as a first electrode (anode 3) and a second electrode (cathode 5) having light transmittance, light The configuration of the organic EL element 1 when a polyphenylene vinylene thin film (PPV) is used as the functional thin film (light emitting layer 4) will be described. In this configuration, when performing the refractive index matching process at each interface, a 0.1N concentration solution of sulfuric acid (H ₂ SO ₄ ) is used as the acid solution, the treatment temperature is room temperature, the treatment time is 600 seconds, and the immersion treatment is performed. To do. The procedure is as follows. (1) The quartz glass of the base material is immersed in a sulfuric acid solution to treat both surfaces of the quartz glass. Thereafter, it is rinsed with ultrapure water and dried at 80 ° C. (refractive index matching treatment). (2) A PEDOT / PSS (= 1/6) solution having a film thickness of 100 nm is formed on one surface of the sulfuric acid solution treated surface by spin coating. Thereafter, it is rinsed with ultrapure water and dried at 200 ° C. (3) Further, the PEDOT / PSS thin film surface is immersed in a sulfuric acid solution, rinsed with ultrapure water, and dried at 200 ° C. (refractive index matching treatment). (4) A PPV solution that emits light at a wavelength of 530 nm as a photofunctional thin film (light emitting layer 4) is formed on the surface subjected to refractive index matching treatment to a film thickness of 100 nm by spin coating, and then dried to 80 ° C. . (5) A PEDOT / PSS (= 1 / 1.6) solution having a film thickness of 100 nm was formed on the light emitting layer 4 by a spin coating method to form a second electrode (cathode 5).

  Using the above method, the organic EL element subjected to the refractive index matching process and the organic EL element not subjected to the refractive index matching process are sequentially installed in the cryostat, and the first electrode (anode 3) and the second electrode are disposed. The light emission characteristics were evaluated by varying the DC voltage from the power supply applied between (cathode 5) from 0V to 12V. In addition, as a light emission characteristic, the light emission spectrum and light emission luminance with respect to each voltage were measured.

Comparing the light emission luminance at an applied voltage of 12 V with and without the refractive index matching processing, the light emission luminance is 1500 cd / m ₂ when the refractive index matching processing is performed, and the light emission luminance is 980 cd when no processing is performed. / m ₂ , indicating that the light emission luminance is about 1.5 times that of the case where the refractive index matching process is not performed. In addition, when the refractive index matching process is performed on the element, light leakage from the end of the element is hardly observed, and the light emitted from the optical functional thin film (the light emitting layer 4) by the refractive index matching process is light. It was confirmed that the light was efficiently emitted to the outside through the first electrode (anode 3) having transparency and the substrate 11.

  In addition, although the organic EL element 1 shown in FIG. 1 was mentioned as an optical functional thin film element which concerns on embodiment of this invention, it is not limited to the structure of the laminated structure shown in FIG. 1, You may make it fibrous. 9 and 10 are perspective views of the fibrous optical functional thin film element, in which the cross section of FIG. 9 is circular and the cross section of FIG. 10 is rectangular.

  As shown in FIG. 9, the optical functional thin film element (organic EL element) 10 has a base material 11 as a core material, an anode 12 disposed on the outer periphery of the base material 11, and the outer periphery of the anode 12 is subjected to refractive index matching processing. Then, the refractive index adjusting layer 13 is formed, the optical functional thin film (light emitting layer) 14 and the cathode 15 are sequentially arranged on the outer periphery thereof, and the insulating layer 16 is formed on the outermost periphery. . By connecting the power source 17 to the anode 12 and the cathode 15 so that a voltage can be applied, light emission occurs from the light emitting layer 14 in accordance with the magnitude of the applied voltage. Further, the optical functional thin film element (organic EL element) 18 shown in FIG. 10 has a base material 19 as a core material, and the outer periphery of the base material 19 is subjected to refractive index matching processing to form a refractive index adjustment layer 20. The anode 21, the optical functional thin film (light emitting layer) 22, and the cathode 23 are sequentially arranged on the outer periphery of the refractive index adjusting layer 20, and the insulating layer 24 is formed on the outermost peripheral surface. By connecting a power source 25 to the anode 21 and the cathode 23 so that a voltage can be applied, the light emitting layer 22 emits light according to the magnitude of the applied voltage.

  Although FIG. 9 shows an example in which the base material is a core material, the anode is a core material, the outer periphery thereof is subjected to refractive index matching treatment, and the processing surface is coated with an optical functional thin film, a cathode, and the outermost surface. An insulating layer may be formed on the outer periphery. Similarly, FIG. 10 may be configured without a substrate.

  It becomes possible to make it into a fibrous form by setting it as the said structure, and it can be set as various woven / knitted fabrics by weaving or knitting similarly to a normal fiber. Here, “fibrous” does not mean a fiber (fiber) itself, but includes a fibrous long structure. In the case of a long structure, the cross-sectional shape may be circular, elliptical, rectangular, flat or polygonal, and the shape is not limited.

  Moreover, by using such a fibrous form, a flexible and highly functional optical functional thin film element can be obtained and applied to articles such as various display bodies, dimmers, lighting bodies, and solar cells. It becomes possible.

  In addition to the applications described above, unprecedented flexibility can be provided, so that twisted yarns, woven fabrics, knitted fabrics, non-woven fabrics, and three-dimensional woven knitted fabrics combined with ordinary fibers can also be provided.

  As described above, the optical functional thin film element, the manufacturing method thereof, and the article using the optical functional thin film element according to the present invention are obtained by subjecting at least one of the interfaces of each layer to a refractive index matching process. The light generated inside is prevented from being guided or leaked to the end of the element, and absorption by repeated reflection is reduced, so that it can be efficiently emitted to the outside.

  Hereinafter, although it demonstrates based on an Example more concretely, it is not limited to the illustrated Example.

[Example 1]
In Example 1, the following materials were selected for each layer in order to form a laminated structure type optical functional thin film element. Quartz glass as the light-transmitting substrate, and water-dispersed composite solution of polyethylenedioxythiophene (PEDOT) and polystyrenesulfonic acid (PSS) as the first electrode (cathode) that transmits light (PEDOT / PSS = 1 / 1.6), a polyphenylene vinylene (PPV) solution diluted with toluene as a solution for the light emitting layer, and an aqueous dispersion composite solution of polyethylene dioxythiophene (PEDOD) and polystyrene sulfonic acid (PSS) described above as the second electrode (anode). (PEDOT / PSS = 1 / 1.6) was prepared.

  Next, after immersing quartz glass as a base material in a 0.1N sulfuric acid solution under conditions of a processing temperature of room temperature and a processing time of 600 seconds, a rinse treatment with ultrapure water was performed, and then 80 ° C. And dried. After that, as the first electrode (cathode), a water-dispersed composite solution of polyethylenedioxythiophene (PEDOD) and polystyrene sulfonic acid (PSS) (PEDOT / PSS = 1 / 1.6) is formed to a thickness of 100 nm by spin coating. After forming a thin film, the film was dried at 200 ° C.

  Thereafter, a polyphenylene vinylene (PPV) solution diluted with toluene was formed into a film thickness of 100 nm by a spin coating method, and then dried at 80 ° C. and cured. The PPV thin film can emit light having a wavelength of 530 nm (green) by applying a DC voltage. Finally, as the second electrode (anode), a water-dispersed composite solution of polyethylenedioxythiophene (PEDOD) and polystyrene sulfonic acid (PSS) (PEDOT / PSS = 1 / 1.6) is formed to a thickness of 100 nm by spin coating. Formed.

[Example 2]
In Example 2, the following materials were selected for each layer in order to form a laminated structure type optical functional thin film element. Quartz glass as the light-transmitting substrate, and water-dispersed composite solution of polyethylenedioxythiophene (PEDOT) and polystyrenesulfonic acid (PSS) as the first electrode (cathode) that transmits light (PEDOT / PSS = 1 / 1.6), polyphenylene vinylene (PPV) solution diluted with toluene as the solution for the light emitting layer, and the above-mentioned aqueous dispersion complex solution (PEDOT) of polyethylene dioxythiophene (PEDOT) and polystyrene sulfonic acid (PSS) as the second electrode (anode) /PSS=1/1.6).

  Next, quartz glass serving as a base material was immersed in a 0.1N sulfuric acid solution at a treatment temperature of room temperature and a treatment time of 600 seconds, and then rinsed with ultrapure water and dried at 80 ° C. After that, as the first electrode, a thin film of polyethylenedioxythiophene (PEDOT) and polystyrene sulfonic acid (PSS) in water dispersion (PEDOT / PSS = 1 / 1.6) is formed to a thickness of 100 nm by spin coating. The thin film was dried at 200 ° C.

  After the first electrode is formed, the surface is immersed in a 1N sulfuric acid solution at a treatment temperature of room temperature and a treatment time of 600 seconds, rinsed with ultrapure water, and then dried at 80 ° C. did. Thereafter, a polyphenylene vinylene (PPV) solution diluted with toluene was formed into a film thickness of 100 nm by spin coating, and then dried and cured at 80 ° C. The PPV thin film can emit light having a wavelength of 530 nm (green) by applying a DC voltage. Finally, as the second electrode (anode), a water-dispersed composite solution of polyethylenedioxythiophene (PEDOT) and polystyrene sulfonic acid (PSS) (PEDOT / PSS = 1 / 1.6) is used, and spin coating is used. The film thickness was 100 nm.

Example 3
In Example 3, an optical functional thin film element was produced in the same manner as in Example 2 except that a 0.01N sulfuric acid solution was used during the refractive index matching process.

Example 4
In Example 4, an optical functional thin film element was produced in the same manner as in Example 2 except that a 1N sulfuric acid solution was used during the refractive index matching process.

Example 5
In Example 4, an optical functional device was produced in the same manner as in Example 2 except that a polyfluorene (PFO) solution diluted with toluene was used as the light emitting layer solution. It is possible to emit light having a wavelength of 470 nm (blue) by applying a DC voltage from the PFO thin film.

Example 6
In Example 6, an optical functional element was produced in the same manner as in Example 5 except that a 0.01N sulfuric acid solution was used during the refractive index matching process.

Example 7
In Example 7, an optical functional thin film element was fabricated in the same manner as in Example 2 except that a 1N hydrochloric acid solution was used during the refractive index matching process.

Example 8
In Example 8, an optical functional thin film element was produced in the same manner as in Example 2 except that 1N sodium hydroxide solution, the treatment temperature was room temperature, and the treatment time was 30 seconds during the refractive index matching treatment.

[Comparative Example 1]
In Comparative Example 1, the following materials were selected as the material of each layer in order to form a laminated structure type optical functional thin film element. Quartz glass as a light-transmitting substrate, water-dispersed composite solution of polyethylenedioxythiophene (PEDOT) and polystyrene sulfonic acid (PSS) as a light-transmitting electrode (PEDOT / PSS = 1 / 1.6), for light-emitting layer A polyphenylene vinylene (PPV) solution diluted with toluene was prepared as a solution, and an aqueous dispersion complex solution (PEDOT / PSS = 1 / 1.6) of polyethylene dioxythiophene (PEDOT) and polystyrene sulfonic acid (PSS) was prepared as an electrode. .

  Next, the quartz glass serving as the substrate was washed with ultrapure water and dried at 80 ° C. After that, water dispersion composite solution of polyethylenedioxythiophene (PEDOT) and polystyrene sulfonic acid (PSS) (PEDOT / PSS = 1 / 1.6) is used as the first electrode (cathode) to a film thickness of 100 nm by spin coating. A thin film was formed, and the thin film was further dried at 200 ° C.

  Thereafter, a polyphenylene vinylene (PPV) solution diluted with toluene was formed into a film thickness of 100 nm by spin coating, and then dried and cured at 80 ° C. Note that light having a wavelength of 530 nm (green) can be emitted from the PPV thin film by applying a DC voltage. Finally, as the second electrode (anode), a water-dispersed composite solution of polyethylenedioxythiophene (PEDOD) and polystyrene sulfonic acid (PSS) (PEDOT / PSS = 1 / 1.6) is formed to a thickness of 100 nm by spin coating. did.

[Comparative Example 2]
In Comparative Example 2, an optical functional thin film element was produced in the same manner as in Comparative Example 1, except that a polyfluorene (PFO) solution diluted with toluene was used as the light emitting layer solution. When a DC voltage is applied from the PFO thin film, it becomes possible to emit light having a wavelength of 4700 nm (blue).

Each optical functional thin film element obtained from Example 1 to Example 8 and Comparative Examples 1 and 2 was placed in a cryostat, and the light emission luminance was increased by applying a DC voltage of 12 V under the condition of a vacuum degree of 10 ₋₃ Torr. It was measured. Table 1 shows the measurement results.

  As shown in Table 1, the optical functional elements from Example 1 to Example 8 in which the refractive index matching process was performed to form the refractive index adjustment layer were all comparative examples 1 in which the refractive index adjustment layer was not formed. It was found that the luminance value was high and the light emission performance was improved as compared with the optical functional element 2. In each example, the refractive index matching process was performed by changing the sulfuric acid concentration, but in Example 2 where the sulfuric acid concentration was 0.1 N, the luminance value was the highest, and the sulfuric acid concentration was set to a predetermined value. It was found that the light emission performance is improved by setting the range.

FIG. 1 is a cross-sectional view of an organic EL element which is an example of an optical functional thin film element according to an embodiment of the present invention. Fig. 2 shows the case where an inorganic transparent conductor (ITO) and an organic transparent conductor (PEDOT / PSS (= 1/6) film) as an anode are immersed in a sulfuric acid solution or untreated. It is the result of investigating the change of the refractive index in the case. This is the result of investigating the behavior of OH ions by time-of-flight secondary ion mass spectrometry for an electrode (PEDOT / PSS) formed on a quartz glass substrate. (A) is untreated, (b) Is the result of acid treatment with H ₂ SO ₄ . FIG. 4 is a diagram showing a wavelength dependency curve of a refractive index when the anode (untreated PEDOT: PSS thin film) is immersed in a sulfuric acid solution (H ₂ SO ₄ ). FIG. 5 is a diagram showing wavelength dependence curves of the quartz glass (base material) shown in FIG. 4 and an anode (PEDOT: PSS thin film) treated with sulfuric acid at a treatment concentration of 0.1 N. FIG. 6 is an explanatory diagram of an emission spectrum emitted from the light emitting layer. FIG. 7 shows the difference | λ ₁ − between the wavelength λ _{1 at} which the wavelength dependence curves of the refractive index of the anode and the light emitting layer subjected to the refractive index matching process intersect, and the wavelength λ _em of the emission spectrum peak emitted from the light emitting layer. It is a figure explaining the relationship between (lambda) _em | and (lambda) _em . (a) is an xy chromaticity diagram, and (b) is an explanatory diagram of (a). FIG. 9 is a perspective view of a fibrous optical functional thin film element according to another embodiment of the present invention, which is an example in which the cross section is circular. FIG. 10 is a perspective view of a fibrous optical functional thin film element according to another embodiment of the present invention, which is an example in which the cross section is rectangular.

Explanation of symbols

1 ... Organic EL device,
2 ... base material,
3 ... Anode,
4 ... light emitting layer,
5 ... Cathode,
6, 7, 8 ... refractive index adjustment layer,
9 ... Power supply,

Claims (18)

   An optical functional thin film element having an optical functional thin film sandwiched between a first electrode and a second electrode, wherein the first interface between the first electrode and the optical functional thin film, Refractive index matching treatment is performed on at least one of the second interface between the optical functional thin film and the second electrode and the third interface between the first electrode and air. An optical functional thin film element comprising the adjusted refractive index adjusting layer.   The refractive index adjustment layer is formed by performing a refractive index matching process on at least one of the first electrode, the second electrode, and the optical functional thin film. 1. The optical functional thin film element according to 1.   The refractive index adjustment layer is formed by immersing at least one of the first electrode, the second electrode, and the optical functional thin film with an acid solution or an alkali solution, rinsing with pure water, and then drying. 3. The optical functional thin film element according to claim 1, wherein the optical functional thin film element is characterized.   3. The optical functional thin film element according to claim 1, wherein at least one of the first electrode and the second electrode has optical transparency.   5. The optical function according to claim 1, wherein the optical functional thin film is a light emitting layer that emits light by a voltage applied between the first electrode and the second electrode. 6. Thin film element. In the first interface, at least one of the first electrode and the optical functional thin film subjected to the refractive index matching treatment exhibits a wavelength dependency of a refractive index in a visible light region, and in a wavelength dependency curve of the refractive index. The refractive indexes of the first electrode and the optical functional thin film at a wavelength of 380 nm are n ₁ (380) and n _f (380), respectively, and the refractive indexes at a wavelength of 780 nm are respectively n ₁ (780) and n _f (780), the difference between the two at a wavelength of 380 nm {n ₁ (380) − n _f (380)} and the difference between the two at a wavelength of 780 nm {n ₁ (780) − n _f (780)} are 0.3 or less. The optical functional thin film element according to any one of claims 1 to 5, wherein The wavelength dependency curve of the refractive index of the first electrode subjected to the refractive index matching process and the light emitting layer intersects in the visible light region, the wavelength of the intersection is λ ₁ , and the emission spectrum emitted from the light emitting layer. 7. The optical functional thin film element according to claim ₁ , wherein | λ ₁ −λ _em | is 100 nm or less, where λ _em is a peak wavelength. In the third interface, at least one of the first electrode subjected to the refractive index matching process and the air exhibits the wavelength dependency of the refractive index in the visible light region. In the wavelength dependency curve of the refractive index, N ₁ (380) and n _air (380) for the refractive index of the electrode and air at 380 nm, respectively, and n ₁ (780) and n _air (780) for the same refractive index at the wavelength of 780 nm, respectively. The difference between the two at a wavelength of 380 nm {n ₁ (380) − n _air (380)} and the difference between the two at a wavelength of 780 nm {n ₁ (780) − n _air (780)} is 0.3 or less. The optical functional thin film element according to any one of claims 1 to 7. The first electrode subjected to the refractive index matching treatment and the wavelength dependence curve of the refractive index of air intersect in the visible light region, the wavelength of the intersection is λ ₂ , and the spectrum peak of light emitted from the light emitting layer. _9. The optical functional thin film element according to claim 1, wherein | λ ₂ −λ _em | ≦ 100 nm is satisfied, where λ _em is a wavelength.   The optical functional thin film element according to claim 1, wherein the optical functional thin film is made of a π-conjugated material.   The π-conjugated materials include quinolinol derivatives, fluorene derivatives, phthalocyanine derivatives, triphenyldiamine derivatives, polyparaphenylene derivatives, distyrysarylene derivatives, oxadiazole derivatives, pyrazoline derivatives, polythiophene derivatives, poly (N-alkylcarbazole) derivatives. The optical function according to claim 10, wherein the optical function is one selected from the group of polyphenylacetylene derivatives, polyphenylene ethynylene derivatives and polyphenylene butadienylene derivatives, or a mixture containing one selected from these groups. Thin film element.   The optical functionality according to any one of claims 1 to 11, wherein the first electrode, the optical functional thin film, and the second electrode are made of a material that is soluble in water or a solvent. Thin film element.   At least one of the first electrode or the second electrode may be selected from among doped polypyrrole, doped polyaniline, doped polythiophene, doped polyacetylene, doped polyisothianaphthene, and derivatives thereof. The optical functional thin film element according to claim 10, comprising at least one selected.   11. The optical functionality according to claim 10, wherein at least one of the first electrode or the second electrode contains at least one selected from polyethylene dioxythiophene, polypropylene oxide, and derivatives thereof. Thin film element.   The surface of at least one of the first electrode, the second electrode, and the optical functional thin film is immersed in an acid solution or an alkali solution, the immersed surface is rinsed with pure water, and dried to form a refractive index adjustment layer. A method for producing an optical functional thin film element, wherein the first electrode, the second electrode, and the optical functional thin film are joined to form an optical functional thin film.   The article | item of the display body or the illumination body using the optical functional thin film element of any one of Claims 1 thru | or 14.   The article | item of the display body or the illumination body using the optical functional thin film element of any one of Claims 1 thru | or 14.   An article for a solar cell using the optical functional thin film element according to any one of claims 1 to 14.

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