JP2006092899A - Display element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To properly ensure flatness of a minute resonance layer, in a display element composed by forming the minute resonance layer on a glass substrate and by forming a light-emitting element thereon. <P>SOLUTION: This display element 100 is composed by forming the minute resonance layer 30 on the glass substrate 10 and by forming one or more luminescent layers 44 and electrodes 41 and 46 for emitting light therefrom on the minute resonance layer 30. The display element is so structured that the glass substrate 10 is formed of soda glass; a high-refraction material of the minute resonance layer 30 is formed of TiO<SB>2</SB>; processes such as a plasma treatment for removing an alkaline constituent on a surface of the glass substrate 10 are executed before forming the minute resonance layer 30; a passivation film 20 formed of SiO<SB>2</SB>or the like is formed on top of it; and the minute resonance layer 30 is formed on the top of it. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a display element in which a microresonance layer is formed on a glass substrate and a light emitting element is formed thereon, and can be applied to, for example, an organic EL (electroluminescence) display element.

  2. Description of the Related Art Conventionally, there is a structure in which a microresonance layer is inserted between a glass substrate and an element in order to improve light extraction efficiency in a self-luminous element such as a display element, particularly an organic EL element.

  The microresonance structure is a structure in which a plurality of layers having a large refractive index difference are inserted between a glass substrate and an element to cause multiple reflections in the element to resonate (for example, see Patent Document 1).

Generally, TiO ₂ (refractive index 2.2) and SiO ₂ (refractive index 1.5) are used as a microresonance layer between glass (refractive index 1.5) and transparent electrode ITO (refractive index 1.9). ).

In such a microresonant layer composed of a plurality of layers, each film thickness is adapted to the optical length of the wavelength to be resonated. In particular, the film thickness t of a highly refractive material made of TiO ₂ or the like is obtained by t = (2M−1) λ / 4n (where M is a natural number, λ is a resonance wavelength, and n is a refractive index).

  Here, when M, that is, the film thickness t becomes too large, the effect of resonance is reduced. Therefore, in general, M is 1 or 2, and the film thickness is about 100 nm.

  In addition, the microresonance structure in the organic EL element has a bottom emission structure in which glass substrate / microresonance layer / light emitting element layer are laminated in order, and a top emission structure in which glass substrate / light emitting element layer / microresonant layer is laminated in this order. However, since the microresonance layer is often formed by sputtering and there is a concern about damage to the light emitting layer in the light emitting element layer, the bottom emission structure is generally large.

  As described in Patent Document 2, there are many studies on alkali resonance using a bottom emission structure, but it is desirable to use a relatively inexpensive soda glass in order to reduce costs. .

In general, TiO ₂ itself constituting the microresonance layer is used as a passivation film for preventing precipitation of alkali components of soda glass in the same manner as SiO ₂ (see, for example, Patent Document 3).

In addition, as a method of uniformly forming a titanium oxide (TiO ₂ ) film, there is a method of depositing a fluorometal complex compound in an aqueous solution (see, for example, Patent Document 4).
Japanese Patent Laid-Open No. 10-177896 JP 2003-123987 A Japanese Patent Laid-Open No. 6-18908 JP 2003-191323 A

In a microresonance structure with a bottom emission structure, when soda glass is adopted as a glass substrate for cost reduction, as described above, it is conceivable to use TiO ₂ itself constituting the microresonance layer as a passivation film.

In this case, however, according to the study of the present inventors, in the structure in which TiO ₂ and SiO ₂ are formed on soda glass, as shown in FIG. 3, a TiO ₂ film is formed on the soda glass by sputtering. It has been found that when formed, the growth of the TiO ₂ film itself is hindered by the influence of the alkali component of the soda glass (for example, Na), resulting in unevenness and not a uniform film.

If the unevenness becomes large, it becomes difficult to obtain the desired resonance due to the influence of scattering or the like. Especially in an extremely thin element such as an organic EL element, it may cause leakage current and cause element destruction. It is necessary to form TiO _{2 in the} resonance layer as flat as possible.

  In addition, as described above, as a method for uniformly forming a titanium oxide film, it is conceivable to employ a method in which a fluorometal complex compound is precipitated in an aqueous solution. However, titanium oxide used in a microresonant layer has a low refractive index. Since a number of layers are alternately laminated together with the material, forming a film by the above method is a laborious operation. Further, since the film thickness needs to be controlled on the order of nanometers, the above method is not suitable for the production of a microresonant layer.

  The present invention has been made in view of the above problems, and in a display element in which a microresonance layer is formed on a glass substrate and a light emitting element is formed thereon, the flatness of the microresonance layer is appropriately adjusted. The purpose is to secure.

In order to achieve the above object, according to the first aspect of the present invention, a microresonant layer (30) is formed on a glass substrate (10), and at least one light emitting layer (30) is formed on the microresonant layer (30). 44) and electrodes (41, 46) for emitting light thereof, the glass substrate (10) is made of soda glass, and the high refractive material of the microresonant layer (30) is titanium oxide (TiO ₂ ). A passivation film (20) is formed on a glass substrate (10) subjected to the step of removing alkali components on the surface, and a microresonance layer (30) is formed thereon. It is said.

That is, the present invention removes the alkali component on the surface of the glass substrate (10) when the glass substrate (10) is made of soda glass and the high refractive material of the microresonant layer (30) is made of titanium oxide (TiO ₂ ). A display element is provided in which a process is performed, a passivation film (20) is formed thereon, and a microresonance layer (30) is formed thereon.

  According to the study of the present inventor, the configuration of the display element as in the present invention can suppress unevenness on the film surface of the microresonance layer (30) to form a uniform film and improve the flatness. It was confirmed experimentally that it was possible.

  This is considered to remove the alkali component on the surface of the glass substrate (10) hindering the flatness of the microresonant layer (30) and prevent the precipitation of a new alkali component by the passivation film (20).

  Therefore, according to the present invention, in the display element in which the microresonance layer (30) is formed on the glass substrate (10) and the light emitting element (40) is formed thereon, the microresonance layer (30) Flatness can be ensured appropriately.

  According to a second aspect of the present invention, in the display element according to the first aspect, the refractive index of the passivation film (20) is 1.4 to 1.6.

  If the refractive index of the passivation film (20) is 1.4 to 1.6, the refractive index of the passivation film (20) can be made close to glass. Thereby, the optical influence by providing the passivation film (20) which is a new layer between the glass substrate (10) and the microresonance layer (30) can be eliminated as much as possible.

Further, as in the invention described in claim 3, in the display element described in claim 1 or 2, the passivation film (20) can be characterized in that it is a film made of SiO _2. .

Since the SiO ₂ film is a general-purpose passivation film, it is advantageous in terms of cost.

  Further, as in the invention according to claim 4, in the display element according to any one of claims 1 to 3, the step of removing the alkali component is a plasma treatment. Can be a thing.

  In the invention according to claim 5, in the display element according to any one of claims 1 to 4, the passivation film (20) and the microresonant layer (30) are formed by sputtering. It is characterized by being.

  According to this, by continuously forming the passivation film (20) and the microresonant layer (30) in a vacuum atmosphere, contamination due to immersion in the atmosphere or liquid, and the back surface of the glass substrate (10). The influence of the alkali component can be suppressed.

  In addition, the code | symbol in the bracket | parenthesis of each said means is an example which shows a corresponding relationship with the specific means as described in embodiment mentioned later.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. A display element according to an embodiment of the present invention is an organic EL element or an inorganic EL element having a microresonance structure, wherein a microresonance layer is formed on a glass substrate, and at least one or more on the microresonance layer. It is a display element in which a light emitting layer and an electrode for emitting light are formed.

  Hereinafter, although it does not limit, it demonstrates taking the example which applied this invention to the organic EL element. FIG. 1 is a diagram showing a schematic cross-sectional configuration of an organic EL element 100 as a display element according to an embodiment of the present invention.

  In the organic EL element 100, a passivation film 20, a microresonance layer 30, and a light emitting element 40 are sequentially laminated on a glass substrate 10. Here, the microresonant layer 30 is formed by alternately stacking high refractive material layers 31 and low refractive material layers 32. The light emitting element 40 is an element part in the organic EL element, and includes at least one or more light emitting layers 44 and electrodes 41 and 46 that emit light.

  Specifically, as shown in FIG. 1, the light emitting element 40 includes an anode 41, a hole injection layer 42, a hole transport layer 43, a light emitting layer 44, an electron transport layer 45, a cathode from the microresonant layer 30 side. 46 are sequentially laminated. Each of the layers 41 to 46 forming the light emitting element 40 is made of a material applied to a general organic EL element.

  The light emitting layer 44 may be composed of a plurality of layers. Further, the light emitting layer 44 may be at least sandwiched between the anode and the cathode, and the hole injection layer 42, the hole transport layer 43, the electron transport layer 45, and the electron injection layer may be used as necessary. The configuration may be omitted or added as appropriate.

Here, in the organic EL element 100 of the present embodiment, as a unique constituent point, the glass substrate 10 is made of soda glass, and is subjected to a step of removing the alkaline component on the surface. Further, the high refractive material layer 31 of the microresonance layer 30 is made of a titanium oxide (TiO ₂ ) film, and the microresonance layer 30 is formed on the glass substrate 10 via the passivation film 20.

In the present embodiment, the refractive index of the passivation film 20 is preferably 1.4 to 1.6. For example, a film made of SiO ₂ can be adopted as the passivation film 20.

  Moreover, as a process of removing the alkali component on the surface of the glass substrate 10, plasma treatment can be employed. And it is preferable that the passivation film 20 and the microresonance layer 30 are formed by sputtering.

Next, in the present embodiment, the microresonance layer 30 in which the high refractive material layer 31 is made of a titanium oxide (TiO ₂ ) film is formed on the passivation film on the glass substrate 10 that has been subjected to the step of removing the alkali component on the surface. The reason for adopting the unique configuration of forming via 20 is based on the results of the following studies. An example of the study will be described.

[Examination example]
The soda glass as the glass substrate 10 was subjected to UV ozone treatment, brush cleaning with a neutral detergent, spin drying, and drying in a 120 ° C. oven before forming each film thereon.

  In this examination example, using the glass substrate 10, the following examples and comparative examples were performed, and changes due to the presence or absence of a plasma treatment and a passivation film as a process of removing the alkali component on the surface were examined.

As an example, plasma treatment was performed under the conditions of Ar: O ₂ = 7: 3, vacuum degree 3.3 × 10 ⁻³ Torr, 2.0 W / cm ² , 3 minutes before film formation, and the passivation film 20 was made of SiO. ₂ was deposited to a thickness of 30 nm.

A TiO ₂ film that is a highly refractive material layer 31 of the microresonant layer 30 was formed thereon. The film thickness of TiO ₂ needs to be controlled depending on the wavelength at which it is desired to resonate. Film formation is performed by RF sputtering, and the substrate temperature is 300.degree.

In the substrate 10 on which TiO ₂ as this example was fabricated, the surface of TiO ₂ was evaluated by an atomic force microscope (AFM). FIG. 2 is a diagram schematically showing the state of the surface of TiO ₂ in the present example and a comparative example described later based on the AFM image of the surface.

In FIG. 2, (a) is a plasma treatment, SiO ₂ film 30 nm, that of the embodiment described TiO ₂ film 100nm deposition, (b) is no plasma treatment, SiO ₂ film 50 nm, compared to the TiO ₂ film 100nm deposition In Example 2, (c) is that in Comparative Example 5 in which no plasma treatment, no SiO ₂ film, and a TiO ₂ film of 100 nm were formed.

In the substrate 10 of this example, as shown in FIG. 2A, the unevenness on the film surface of the TiO ₂ film is suppressed to form a uniform film. Specifically, in this AFM evaluation, the ten-point average roughness (Rz) was 30 nm, and no abnormal growth of TiO ₂ was observed. Note that this value of Rz 30 nm is almost the same as that of a transparent electrode generally used in a display element such as a liquid crystal or an organic EL, and is roughly enough to be used as a display element.

As a comparative example, with respect to the glass substrate 10, as compared to the aforementioned Example and Comparative Example 1: no plasma treatment, SiO ₂ film thickness 30 nm, Comparative Example 2: No plasma treatment, SiO ₂ film thickness 50 nm, compared Example 3 A sample was prepared under the conditions of no plasma treatment, SiO ₂ film thickness of 100 nm, comparative example 4: with plasma treatment, no SiO ₂ and comparative example 5: no plasma treatment, no SiO ₂ .

In these comparative examples, the TiO ₂ film thickness was 100 nm. Moreover, Rz of each comparative example was comparative example 1:85 nm, comparative example 2:88 nm, comparative example 3:70 nm, comparative example 4: 125 nm, comparative example 5: 118 nm.

Even if no plasma treatment is performed, when SiO ₂ as the passivation film 20 is formed, Rz is slightly reduced. However, even if the SiO ₂ film thickness is increased to 100 nm, the improvement is not greatly improved. This is presumably because the alkali component on the glass surface precipitates in SiO ₂ or on the surface layer during SiO ₂ film formation.

In the case of only the plasma treatment (in the case of the comparative example 4), there was almost no change from the case of nothing (in the case of the comparative example 5). This is considered that even if the alkali component on the surface of the soda glass as the glass substrate 10 was removed, the newly deposited alkali component had an effect on TiO ₂ .

From the above, the combination of the plasma treatment and the passivation film is affected by the alkali component in the TiO ₂ film formation because the plasma treatment removes the alkali component on the glass surface and traps the newly deposited alkali component. It is considered that a good film is formed.

Specifically, as shown in FIG. 2, abnormal growth of TiO ₂ can be reduced to some extent by forming SiO ₂ (see FIGS. 2B and 2C), but plasma treatment is performed and Compared with the above-described embodiment (see FIG. 2A) in which the SiO ₂ film thickness is 30 nm, the effect is insufficient.

  Based on the above results, in the configuration shown in FIG. 1, an organic EL element was produced under the conditions of the above example and the comparative example 5.

First, as in the above Example and Comparative Example 5, the glass substrate 10 made of soda glass is subjected to the above plasma treatment in the Example, and the SiO ₂ film thickness is 30 nm. In the above Comparative Example 5, the above plasma treatment and Neither SiO ₂ is formed. The microresonance layer 30 is formed on the glass substrate 10 thus prepared.

Here, the microresonant layer 30 is formed by alternately laminating TiO ₂ which is a high refractive material layer 31 and SiO ₂ which is a low refractive material layer 32, and the film thickness of the micro resonant layer 30 is the glass substrate 10. From the side, TiO ₂ / SiO ₂ / TiO ₂ / SiO ₂ = 60 nm / 360 nm / 60 nm / 160 nm.

  Next, 210 nm of ITO (indium tin oxide), which is a transparent electrode, was formed as the anode 41. In addition, here, the ITO surface after film formation was lapped to suppress destruction.

  Next, copper phthalocyanine (CuPc) is 15 nm as the hole injection layer 42, α-NPD (α-naphthylphenylbenzene) is 40 nm as the hole transport layer 43, and electron transporting Alq (Tris ( A layer in which 1% of coumarin as a fluorescent dye was added to 8-quinolyl) aluminum) was formed to 40 nm, and Alq was formed to 20 nm as an electron transport layer 45 by vacuum deposition.

  Next, the cathode 46 was prepared by forming 0.5 nm of LiF (lithium fluoride) on the electron transport layer 45 side in order to enhance the electron injection property and forming 100 nm of aluminum on this LiF.

  The organic EL element 100 as an example formed by the above method showed a good light emission state without dark spots. On the other hand, the organic EL device prepared under the conditions of Comparative Example 5 frequently had dark spots.

This is probably because in the element of Comparative Example 5, TiO ₂ has an abnormally grown portion of the film and the unevenness is large, and that portion was lost together with ITO during ITO polishing, so that it became a dark spot.

  From the examination examples as described above, in this embodiment, the above-described unique configuration is adopted.

Thus, according to the present embodiment, the microresonant layer 30 is formed on the glass substrate 10, and at least one light emitting layer 44 and the electrodes 41 and 46 that emit light are formed on the microresonant layer 30. In this display element, the glass substrate 10 is made of soda glass, the high refractive material of the microresonant layer 30 is made of titanium oxide (TiO ₂ ), and the glass substrate 10 subjected to the step of removing the alkali component on the surface is used. A display element 100 is provided in which a passivation film 20 is formed thereon and a microresonant layer 30 is formed thereon.

That is, in this embodiment, when the glass substrate 10 is made of soda glass and the high refractive material of the microresonance layer 30 is made of titanium oxide (TiO ₂ ), the surface of the glass substrate 10 is formed before the microresonance layer 30 is formed. A display element 100 is provided in which a step of removing an alkali component is performed, a passivation film 20 is formed thereon, and a microresonance layer 30 is formed on the passivation layer 20.

  As described above, according to the study of the present inventor, if the configuration of the display element 100 as in the present embodiment is adopted, the unevenness on the film surface of the microresonance layer 30 can be suppressed and a uniform film can be formed. Was experimentally confirmed (see FIG. 2 above).

  Therefore, according to this embodiment, in the display element in which the microresonant layer 30 is formed on the glass substrate 10 and the light emitting element 40 is formed thereon, the flatness of the microresonant layer 30 is appropriately ensured. be able to.

  In the present embodiment, in the display element 100, the refractive index of the passivation film 20 is preferably 1.4 to 1.6.

  If the refractive index of the passivation film 20 is 1.4 to 1.6, the refractive index of the passivation film 20 can be made close to glass. Thereby, the optical influence by providing the passivation film 20 which is a new layer between the glass substrate 10 and the microresonance layer 30 can be eliminated as much as possible.

In this embodiment, the display element 100 employs a film made of SiO ₂ as the passivation film 20. Since the SiO ₂ film is a general-purpose passivation film, it is advantageous in terms of cost.

  In the present embodiment, the step of removing the alkali component is plasma treatment, but other methods may be adopted.

  In the present embodiment, in the display element 100, the passivation film 20 and the microresonant layer 30 are preferably formed by sputtering.

  By continuously forming the passivation film 20 and the microresonant layer 30 in a vacuum atmosphere, it is possible to suppress contamination caused by immersion in the atmosphere or liquid and the influence of the alkali component on the back surface of the glass substrate 10. .

It is a figure which shows schematic sectional structure of the organic EL element as a display element which concerns on embodiment of this invention. The state of the TiO ₂ surface in the examples and comparative examples of the present invention, is a diagram showing schematically created based on AFM images of the surface, (a) shows the Yes plasma treatment, SiO ₂ film 30 nm, TiO those ₂ film 100nm deposition, (b) is no plasma treatment, the SiO ₂ film 50 nm, which was the TiO ₂ film 100nm deposition, (c) is no plasma treatment, no SiO ₂ film was TiO ₂ film 100nm deposition Is. Without surface treatment on the soda glass is a microscopic photograph showing a cross-section of the element forming a TiO _2, SiO _2.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Glass substrate, 20 ... Passivation film | membrane, 30 ... Micro resonance layer,
40 ... Light emitting element, 41 ... Anode, 42 ... Hole injection layer, 43 ... Hole transport layer,
44 ... Light emitting layer, 45 ... Electron transport layer, 46 ... Cathode.

Claims (5)

A microresonance layer (30) is formed on a glass substrate (10), and at least one light emitting layer (44) and electrodes (41, 46) for emitting light are formed on the microresonance layer (30). In the display element,
The glass substrate (10) is made of soda glass,
The highly refractive material of the microresonant layer (30) is made of titanium oxide (TiO ₂ ),
A passivation film (20) is formed on the glass substrate (10) subjected to the step of removing the alkali component on the surface, and the microresonance layer (30) is formed thereon. Display element to be used. The display element according to claim 1, wherein the refractive index of the passivation film (20) is 1.4 to 1.6. The display element according to claim 1, wherein the passivation film is a film made of SiO ₂ . The display element according to claim 1, wherein the step of removing the alkali component is a plasma treatment. The display element according to any one of claims 1 to 4, wherein the passivation film (20) and the microresonance layer (30) are formed by sputtering.

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