JP6944689B2 - Luminescent particles, compositions, organic electroluminescent devices and methods for manufacturing them - Google Patents

Description

The present invention relates to luminescent particles capable of generating light by themselves and emitting light, and an organic electroluminescence device using the luminescent particles.

The electroluminescence element is an element that emits light by applying an electric field to the light emitting layer or supplying a carrier to the light emitting layer, and various types are used depending on the type of material, the form of the layer, the layer structure, and the like. Is proposed. For example, as an inorganic electroluminescence element using an inorganic material as a light emitting material, a dispersed element in which phosphor particles are dispersed in a matrix material such as a dielectric binder to form a light emitting layer is known, and this type of electro is used. Several luminescence elements using luminescent particles composed of a core material and a phosphor coating layer have been proposed.

For example, Patent Document 1 proposes a dispersed device using luminescent particles having a dielectric core and a phosphor coating layer made of a phosphor material. Here, the dielectric core is said to have a function of efficiently concentrating the voltage applied to the light emitting layer on the phosphor portion, and is an inorganic dielectric core such as _{BaTa 2} O ₆ , _{BaTIO 3} , Y ₂ O _3. The material is described as a specific example. Further, as the phosphor material, inorganic fluorescent materials such _{as ZnS: Mn, Zn 2} SiO ₄ : Mn, and BaAl ₂ S _{4: Eu are exemplified.}

Further, Patent Document 2 also describes a dispersed device in which particles in which a layer of ZnS: Mn, which is a phosphor, is formed on the surface of particles of _{Y 2} O _{3, which is a dielectric, are used as a light emitting layer.} According to the document, when an AC voltage is applied between a pair of electrodes provided on both sides of the light emitting layer, electrons are injected into the phosphor layer from traps in the phosphor layer of particles, and the electrons are accelerated. It is described that the hot electron is formed and Mn, which is the center of light emission, is collisionally excited to generate light.

Japanese Unexamined Patent Publication No. 2005-222801 Japanese Unexamined Patent Publication No. 2005-93358

As described above, Patent Documents 1 and 2 describe an electroluminescence element using luminescent particles in which a phosphor coating layer is formed on the surface of a dielectric core (particle). Here, in these documents, from the description of specific examples of the phosphor material and the light emission mechanism, the inorganic fluorescent material that is excited by the collision of accelerated electrons and emits light by the recombination of holes and electrons generated at that time. It is understood that it is premised on using. However, in inorganic fluorescent materials, the emission color is determined by the constituent elements and crystal structure, and other factors that control the characteristics, such as those found in organic materials, such as the type of skeletal structure and the number and position of heteroatoms contained in the skeleton, Since there is no variation such as the type of substituent, the emission color is limited to some extent. Therefore, it is difficult for the electroluminescence devices described in these documents to adjust the emission color of the luminescent particles to a desired hue.
On the other hand, in recent years, a luminescent material made of an organic compound (organic luminescent material) has been attracting attention because it can be given various luminescent properties by molecular design. Here, the organic light emitting material is excited by recombination of holes and electrons supplied from the outside and emits light. Therefore, an organic electroluminescent element using such an organic light emitting material generally has a light emitting layer containing the organic light emitting material and an anode and a cathode arranged on both sides of the light emitting layer, and carriers (holes) generated from the anode and the cathode are provided. , Electrons) are configured to be supplied to the light emitting layer. Of these, a conductive material having a relatively small work function, such as Mg and Ca, is used for the cathode in order to efficiently emit electrons. However, conductive materials with a small work function are prone to oxidative deterioration, which causes the durability of the device to be impaired, is not suitable for film formation in a wet process performed in the air, and oxidative deterioration of the cathode. There is an inconvenience that a sealing layer must be provided to prevent the above.

Under such circumstances, the present inventors have proceeded with research with the aim of finding a material that has a high degree of freedom in molecular design of a luminescent material and can emit light without supplying a carrier from the outside. Then, by using such a material, the emission color can be easily adjusted, and light is emitted without supplying carriers from the anode and the cathode to the light emitting layer, and the electrode material can be selected from a wide range. We have been diligently studying for the purpose of providing an organic electroluminescence element that can be used.

As a result of diligent studies to achieve the above object, the present inventors have placed luminescent particles composed of non-dielectric particles and luminescent particles bonded or adsorbed on the surface of the non-dielectric particles in an electric field. It was found that the generation of carriers was observed from the luminescent particles, and the luminescent particles emitted light at the same time. Then, it was clarified that by using such light emitting particles as a material of the light emitting layer, an organic electroluminescence device that emits light without injecting carriers from the anode and the cathode into the light emitting layer can be realized. The present invention has been proposed based on these findings, and specifically has the following configuration.

［１２］ 前記非誘電体粒子のフェルミ準位と前記発光体のＨＯＭＯ準位の差が、０．５ｅＶ以下である［１］に記載の発光粒子。
［１３］ 前記発光体は、該発光体が結合または吸着している非誘電体粒子が発生したキャリアに起因して発光する［１］に記載の発光粒子。
［１４］ 前記発光体の含有量が、前記発光粒子全体の質量に対して０．０１〜１０質量％である［１］に記載の発光粒子。
［１５］ さらに、前記非誘電体粒子の表面および前記発光体を覆うように設けられた保護被膜を有する［１］に記載の発光粒子。
［１６］ ［１］に記載の発光粒子と絶縁材料を含むことを特徴とする組成物。
［１７］ 前記発光粒子として、発光波長が異なる２種類以上の発光粒子を含む［１６］に記載の組成物。
［１８］ 前記２種類以上の発光粒子が放射する光の色相を合せた合成色が、白色である［１７］に記載の組成物。
［１９］ 前記絶縁材料が、ポリスチレン系高分子化合物を含む［１６］に記載の組成物。
［２０］ 前記発光粒子の含有量が、前記組成物の全質量に対して０．１〜５０質量％である［１６］に記載の組成物。
［２１］ ［１］に記載の発光粒子を含むことを特徴とする有機エレクトロルミネッセンス素子。
［２２］ 一対の電極と、該一対の電極間に設けられた発光層を有し、
前記発光層が、前記発光粒子を含む［２１］に記載の有機エレクトロルミネッセンス素子。
［２３］ 一対の電極と、該一対の電極間に設けられた発光層を有し、
前記発光層が、［１６］に記載の組成物からなることを特徴とする有機エレクトロルミネッセンス素子。
［２４］ 前記発光層の厚さが、２０〜５０００ｎｍである［２２］または［２３］に記載の有機エレクトロルミネッセンス素子。
［２５］ さらに、前記一対の電極と前記発光層との間の少なくとも一方に、絶縁層が設けられている［２２］または［２３］に記載の有機エレクトロルミネッセンス素子。
［２６］ 前記絶縁層が、ポリビニルフェノール系高分子化合物を含む［２５］に記載の有機エレクトロルミネッセンス素子。
［２７］ さらに、前記発光層の少なくとも一方の界面に接するように、前記発光層の形成に用いられる発光層形成用液に対して親液性を有する保護層が設けられている［２２］または［２３］に記載の有機エレクトロルミネッセンス素子。
［２８］ 前記保護層が、ポリビニルアルコール系高分子化合物を含む［２７］に記載の有機エレクトロルミネッセンス素子。
［２９］ 電圧変調発光型である［２１］に記載の有機エレクトロルミネッセンス素子。
［３０］ 交流発光型である［２９］に記載の有機エレクトロルミネッセンス素子。
［３１］ 駆動電圧の交流周波数が１０Ｈｚ〜１０ＭＨｚである［３０］に記載の有機エレクトロルミネッセンス素子。
［３２］ ［１］に記載の発光粒子を含む発光層形成用液を用い、湿式プロセスにより発光層を形成する工程を有することを特徴とする有機エレクトロルミネッセンス素子の製造方法。
［３３］ さらに、導電性ペーストまたは導電性高分子化合物を含む液状材料を用い、湿式プロセスにより電極を形成する工程を有する［３２］に記載の有機エレクトロルミネッセンス素子の製造方法。
［３４］ 全ての層形成工程を、湿式プロセスを用いて行う［３２］に記載の有機エレクトロルミネッセンス素子の製造方法。
［３５］ 前記湿式プロセスに際し、インクジェット法を用いる［３２］に記載の有機エレクトロルミネッセンス素子の製造方法。 [1] A luminescent particle having a non-dielectric particle and a luminescent material bonded or adsorbed on the surface of the non-dielectric particle.
[2] The luminescent particle according to [1], wherein the non-dielectric particle is a semiconductor particle.
[3] The luminescent particle according to claim 2, wherein the semiconductor particle is an oxide semiconductor particle.
[4] The luminescent particles according to [1], wherein the non-dielectric particles have a particle size of 100 nm or less.
[5] The luminescent particles according to [1], wherein the emission wavelength of the illuminant is 350 to 800 nm.
[6] The luminescent particle according to [1], wherein the number of molecules of the luminescent material bonded or adsorbed on the surface of the non-dielectric particle is 2 or more per the non-dielectric particle.
[7] The luminescent material is bonded or adsorbed on the surface of the non-dielectric particles by a chemical reaction or interaction on the surface of the non-dielectric particles of the functional group of the precursor [1]. The luminescent particles described in.
[8] The luminescent particle according to [7], wherein the precursor has at least one functional group selected from a carboxyl group, a phosphoric acid group and an amino group.
[9] Hydroxyl groups are present on the surface of the non-dielectric particles,
The luminescent particle according to [1], wherein the luminescent material is bonded or adsorbed on the surface of the non-dielectric particle by a chemical reaction or interaction between a functional group of the precursor and the hydroxyl group.
[10] The luminescent particles according to [1], wherein the luminescent material is a coumarin-based dye.
[11] The luminescent particles according to [10], wherein the coumarin-based dye has a skeletal structure represented by the following formula.

[12] The luminescent particle according to [1], wherein the difference between the Fermi level of the non-dielectric particle and the HOMO level of the luminescent material is 0.5 eV or less.
[13] The light emitting particle according to [1], wherein the light emitting body emits light due to a carrier in which non-dielectric particles to which the light emitting body is bonded or adsorbed are generated.
[14] The luminescent particles according to [1], wherein the content of the luminescent material is 0.01 to 10% by mass with respect to the total mass of the luminescent particles.
[15] The luminescent particle according to [1], further having a protective film provided so as to cover the surface of the non-dielectric particle and the luminescent material.
[16] A composition comprising the luminescent particles according to [1] and an insulating material.
[17] The composition according to [16], wherein the luminescent particles include two or more types of luminescent particles having different emission wavelengths.
[18] The composition according to [17], wherein the synthetic color obtained by combining the hues of the light emitted by the two or more types of luminescent particles is white.
[19] The composition according to [16], wherein the insulating material contains a polystyrene-based polymer compound.
[20] The composition according to [16], wherein the content of the luminescent particles is 0.1 to 50% by mass with respect to the total mass of the composition.
[21] An organic electroluminescence device comprising the luminescent particles according to [1].
[22] It has a pair of electrodes and a light emitting layer provided between the pair of electrodes.
The organic electroluminescence device according to [21], wherein the light emitting layer contains the light emitting particles.
[23] It has a pair of electrodes and a light emitting layer provided between the pair of electrodes.
An organic electroluminescence device, wherein the light emitting layer comprises the composition according to [16].
[24] The organic electroluminescence device according to [22] or [23], wherein the light emitting layer has a thickness of 20 to 5000 nm.
[25] The organic electroluminescence device according to [22] or [23], wherein an insulating layer is provided on at least one of the pair of electrodes and the light emitting layer.
[26] The organic electroluminescence element according to [25], wherein the insulating layer contains a polyvinylphenol-based polymer compound.
[27] Further, a protective layer having a liquid property with respect to the light emitting layer forming liquid used for forming the light emitting layer is provided so as to be in contact with at least one interface of the light emitting layer [22] or. The organic electroluminescence element according to [23].
[28] The organic electroluminescence device according to [27], wherein the protective layer contains a polyvinyl alcohol-based polymer compound.
[29] The organic electroluminescence device according to [21], which is a voltage-modulated light emitting type.
[30] The organic electroluminescence device according to [29], which is an alternating current light emitting type.
[31] The organic electroluminescence device according to [30], wherein the AC frequency of the drive voltage is 10 Hz to 10 MHz.
[32] A method for producing an organic electroluminescence device, which comprises a step of forming a light emitting layer by a wet process using the light emitting layer forming liquid containing the light emitting particles according to [1].
[33] The method for producing an organic electroluminescent element according to [32], further comprising a step of forming an electrode by a wet process using a liquid material containing a conductive paste or a conductive polymer compound.
[34] The method for producing an organic electroluminescent device according to [32], wherein all the layer forming steps are performed by using a wet process.
[35] The method for producing an organic electroluminescent device according to [32], which uses an inkjet method in the wet process.

The luminescent particles of the present invention have a high degree of freedom in molecular design of the illuminant, and emit light even without the supply of carriers from the outside. Since the organic electroluminescence element of the present invention contains such luminescent particles, the emission color can be easily adjusted, and light can be emitted without supplying carriers from the anode and the cathode to the light emitting layer, so that the electrode material can be used in a wide range. You can choose from.

It is a schematic diagram which shows the structural example of a light emitting particle. It is a schematic cross-sectional view which shows the layer structure example of the organic electroluminescence element. It is an emission spectrum of composition 1 and comparative composition 1. It is a graph which shows the luminance-voltage characteristic of element 1 and element 2. It is an emission spectrum of element 1 and element 2. It is a graph which shows the luminance-frequency characteristic of element 1. It is a graph which shows the luminance-frequency characteristic of element 2. It is a graph which shows the light emission waveform when the sine wave voltage of 1 kHz is applied to the element 1. It is a graph which shows the light emission waveform when the sine wave voltage of 10 kHz is applied to the element 1. It is a graph which shows the light emission waveform when the sine wave voltage of 100 kHz is applied to the element 1. It is a graph which shows the light emission waveform when the sine wave voltage of 1 kHz is applied to the element 2. It is a graph which shows the light emission waveform when the sine wave voltage of 10 kHz is applied to the element 2. It is a graph which shows the light emission waveform when the sine wave voltage of 100 kHz is applied to the element 2. It is a graph which shows the light emission waveform with respect to the triangular wave voltage of element 1. It is a graph which shows the light emission waveform with respect to the rectangular wave voltage of element 1. It is a graph which shows the light emission waveform with respect to the triangular wave voltage of element 2. It is a graph which shows the light emission waveform with respect to the rectangular wave voltage of element 2. It is a graph which shows the light emission waveform with respect to the bipolar trapezoidal pulse voltage of element 1. It is a graph which shows the change of the dielectric breakdown strength F when the bipolar trapezoidal pulse voltage is applied to the element 1. It is a graph which shows the change _{of the accumulated charge amount Q ext} when the bipolar trapezoidal pulse voltage is applied to the element 1. It is a graph which shows the change of the current density I when the bipolar trapezoidal pulse voltage is applied to the element 1. It is a graph which shows the light emission waveform with respect to the bipolar trapezoidal pulse voltage of element 2. It is a graph which shows the change of the dielectric breakdown strength F when the bipolar trapezoidal pulse voltage is applied to the element 2. It is a graph which shows the change _{of the accumulated charge amount Q ext} when the bipolar trapezoidal pulse voltage is applied to the element 2. It is a graph which shows the change of the current density I when the bipolar trapezoidal pulse voltage is applied to the element 2. It is a graph which shows the luminance-voltage characteristic of elements 3-6. It is an emission spectrum of elements 3 to 6. It is a graph which shows the luminance-frequency characteristic of element 3. It is a graph which shows the luminance-frequency characteristic of element 4. It is a graph which shows the luminance-frequency characteristic of element 5. It is a graph which shows the luminance-frequency characteristic of element 6. It is a graph which shows the light emission waveform when the sine wave voltage of 1 kHz is applied to the element 3. It is a graph which shows the light emission waveform when the sine wave voltage of 10 kHz is applied to the element 3. It is a graph which shows the light emission waveform when the sine wave voltage of 100 kHz is applied to the element 3. It is a graph which shows the light emission waveform when the sine wave voltage of 1 kHz is applied to the element 4. It is a graph which shows the light emission waveform when the sine wave voltage of 10 kHz is applied to the element 4. It is a graph which shows the light emission waveform when the sine wave voltage of 100 kHz is applied to the element 4. It is a graph which shows the light emission waveform when the sine wave voltage of 1 kHz is applied to the element 5. It is a graph which shows the light emission waveform when the sine wave voltage of 10 kHz is applied to the element 5. It is a graph which shows the light emission waveform when the sine wave voltage of 100 kHz is applied to the element 5. It is a graph which shows the light emission waveform when the sine wave voltage of 1 kHz is applied to the element 6. It is a graph which shows the light emission waveform when the sine wave voltage of 10 kHz is applied to the element 6. It is a graph which shows the light emission waveform when the sine wave voltage of 100 kHz is applied to the element 6. It is a graph which shows the light emission waveform with respect to the bipolar trapezoidal pulse voltage of element 3. It is a graph which shows the change of the dielectric breakdown strength F when the bipolar trapezoidal pulse voltage is applied to the element 3. It is a graph which shows the change _{of the accumulated charge amount Q ext} when the bipolar trapezoidal pulse voltage is applied to the element 3. It is a graph which shows the change of the current density I when the bipolar trapezoidal pulse voltage is applied to the element 3. It is a graph which shows the light emission waveform with respect to the bipolar trapezoidal pulse voltage of the element 4. It is a graph which shows the change of the dielectric breakdown strength F when the bipolar trapezoidal pulse voltage is applied to the element 4. It is a graph which shows the change _{of the accumulated charge amount Q ext} when the bipolar trapezoidal pulse voltage is applied to the element 4. It is a graph which shows the change of the current density I when the bipolar trapezoidal pulse voltage is applied to the element 4. It is a graph which shows the light emission waveform with respect to the bipolar trapezoidal pulse voltage of the element 5. It is a graph which shows the change of the dielectric breakdown strength F when the bipolar trapezoidal pulse voltage is applied to the element 5. It is a graph which shows the change _{of the accumulated charge amount Q ext} when the bipolar trapezoidal pulse voltage is applied to the element 5. It is a graph which shows the change of the current density I when the bipolar trapezoidal pulse voltage is applied to the element 5. It is a graph which shows the light emission waveform with respect to the bipolar trapezoidal pulse voltage of the element 6. It is a graph which shows the change of the dielectric breakdown strength F when the bipolar trapezoidal pulse voltage is applied to the element 6. It is a graph which shows the change _{of the accumulated charge amount Q ext} when the bipolar trapezoidal pulse voltage is applied to the element 6. It is a graph which shows the change of the current density I when the bipolar trapezoidal pulse voltage is applied to the element 6. It is a graph which shows the light emission waveform when the pulse voltage of a different sign is applied to the element 3 alternately. It is a graph which shows the light emission waveform when the pulse voltage of a different sign is applied to the element 4 alternately. It is a graph which shows the luminance-voltage characteristic of elements 7-1-7-4.

Hereinafter, the contents of the present invention will be described in detail. The description of the constituent elements described below may be based on typical embodiments and specific examples of the present invention, but the present invention is not limited to such embodiments and specific examples. The numerical range represented by using "~" in the present specification means a range including the numerical values before and after "~" as the lower limit value and the upper limit value. Further, the isotope species of hydrogen atoms existing in the molecule of the compound used in the present invention is not particularly limited, and for example, all the hydrogen atoms in the molecule ^{may be 1} H, and some or all of them may be ² H. (Duterium D) may be used.

[Luminous particles]
The light emitting particles of the present invention have non-dielectric particles and a light emitting body bonded or adsorbed on the surface of the non-dielectric particles.
In the luminescent particles of the present invention, holes and electrons are generated from the non-dielectric particles, and the luminescent material is excited by the recombination of the holes and electrons. The excited illuminant then emits (emits) light as it returns to the ground state. As described above, since the luminescent particles of the present invention generate holes and electrons by themselves, it is possible to obtain an excellent effect that the luminescent particles can emit light without supplying carriers from the outside. Here, the recombination of the electron and the hole generated from the luminescent particle may be the recombination of the electron and the hole generated from the same luminescent particle, or the electron and the other luminescent particle generated from one luminescent particle. It may be a recombination with a hole generated from.
Hereinafter, each part constituting the luminescent particles of the present invention will be described.

(Non-dielectric particles)
Non-dielectric particles are particles made of non-dielectric. In the present specification, "non-dielectric particles" may be referred to as "nanoparticles".
The non-dielectric material constituting the non-dielectric particles may be either a semiconductor or a conductor, but is preferably a semiconductor.
The semiconductor used for the non-dielectric particles may be an element semiconductor, a compound semiconductor, or an oxide semiconductor, but an oxide semiconductor is preferable. As oxide semiconductors, zinc oxide (ZnO), nickel oxide (NiO), tin oxide (SnO ₂ ), titanium oxide (TiO ₂ ), vanadium oxide (VO ₂ ), indium oxide (In ₂ O ₃ ), strontium titanate Examples thereof include (SrTiO ₃ ), In-Ga-Zn-O-based oxides, and dopant-added oxides obtained by adding dopants such as tin and fluorine to these oxides. Among these oxide semiconductors, tin-added indium oxide (ITO) and fluorine-added tin oxide (FTO) are preferably used, and tin-added indium oxide is more preferably used. In addition, cadmium selenide (CdSe), cadmium sulfide (CdS), cadmium telluride (CdTe), zinc sulfide (ZnS), lead iodide (PbI ₂ ), graphene, etc. are also used as materials for non-dielectric particles. be able to.
Examples of conductors that can be used for non-dielectric particles include gold, silver, copper, platinum, nickel, iron, and alloys thereof.
The non-dielectric particles may be composed of one type of non-dielectric material, or may be composed of a combination of two or more types of non-dielectric materials.

The particle size of the non-dielectric particles is preferably 100 nm or less, more preferably 50 nm or less, and more preferably 10 nm or less from the viewpoint of realizing high-definition light emission in a light emitting device using these light emitting particles. More preferred. Further, the particle size of the non-dielectric particles is preferably 1 nm or more, more preferably 2 nm or more, and more preferably 3 nm or more because the non-dielectric particles can be easily produced and obtained. More preferred.
In the present specification, the "particle size of non-dielectric particles" means the average particle size measured by an electron microscope observation method.

The non-dielectric particles may be obtained as a commercially available product, or may be produced by a sol-gel method.

(Luminous body)
The illuminant is supported on the non-dielectric particles by binding or adsorbing to the surface of the non-dielectric particles.
The illuminant is excited by the energy generated by the recombination of holes and electrons (recombination energy), and emits light when deactivated from the excited state. In the luminescent particles of the present invention, the non-dielectric particles generate electrons and holes, and the electrons and holes are present in the vicinity of the luminescent particles that are bonded or adsorbed to the non-dielectric particles, that is, the non-dielectric particles. The illuminant emits light by recombination on the illuminant.
The illuminant may be a fluorescent illuminant or a phosphorescent illuminant. Further, the light emitting body may be a light emitting body made of an inorganic compound or a light emitting body made of an organic compound, but a light emitting body made of an organic compound is preferable. Since organic compounds have a high degree of freedom in molecular design, various hues can be realized. The term "organic compound" as used herein refers to a compound having one or more carbon atoms covalently bonded to another atom, and is preferably a compound having one or more aromatic rings. The other atom covalently bonded to the carbon atom may be a carbon atom or an atom other than the carbon atom. The light emitted by the light emitter may be any of ultraviolet region light, visible region light, and infrared region light, and is preferably light having a diameter of 380 to 800 nm. Here, the "light emitting body" in the present invention and the light emitting material serving as the "precursor of the light emitting body" described later are concepts including a "dye" that emits visible region light.

As described above, the illuminant is bound or adsorbed on the surface of the non-dielectric particles. The light emitter may be bonded or adsorbed so as to cover the entire surface of the non-dielectric particles, or may be bonded or adsorbed so as to cover a part of the surface of the non-dielectric particles. The number of light emitting molecule molecules bonded or adsorbed on the surface of the non-dielectric particles may be one or more per one non-dielectric particle, but is preferably two or more.
The types of binding and adsorption are not particularly limited, and any light emitter may be supported on the surface of the non-dielectric particles. Specific examples include covalent bonds, coordination bonds, metal bonds, chemical bonds such as ionic bonds, hydrogen bonds, dipole-dipole interaction, van der Waals force, and adsorption by hydrophobic interaction. can. Bonding or adsorption of the luminescent material to the non-dielectric particles is realized by using a precursor of the luminescent material having a functional group and chemically reacting or interacting with the functional group on the surface of the non-dielectric particles. Can be done. Here, the "precursor of the luminescent material" has an atomic group having a structure common to that of the luminescent material, and a functional group is introduced into the atomic group, and when it comes into contact with non-dielectric particles, it is used. When the functional group reacts with or interacts with the surface of the non-dielectric particles, it binds or adsorbs to the surface of the non-dielectric particles to form a light emitter. The contact between the non-dielectric particles and the precursor can be performed, for example, by stirring the particles in a state where they coexist in the solvent.
As the precursor of the luminescent material, for example, a luminescent material having a functional group or a luminescent material modified by introducing a functional group can be used. Examples of the functional group of the precursor include a carboxy group, a phosphoric acid group, an amino group and the like, and a carboxyl group is preferable. For example, a large number of hydroxyl groups are present on the surface of oxide semiconductor particles, and a precursor of a luminescent material having these functional groups is an oxide semiconductor particle in which the functional groups chemically react or interact with the hydroxyl groups. It is presumed that it is carried on the surface of.
In the following, preferred materials that can be used as precursors of luminescent materials will be specifically exemplified. However, the materials that can be used in the present invention are not limitedly interpreted by the following exemplary compounds.

Among these, the precursor of the luminescent material is preferably one that binds or adsorbs to the surface of the non-dielectric particles to become a coumarin-based dye (luminous material), and has a skeletal structure represented by the following formula. It is more preferable that it becomes a coumarin-based dye, and it is particularly preferable that it is a particle 343.

FIG. 1 shows a schematic diagram of luminescent particles formed using Coumarin 343 as a precursor of a luminescent material. In FIG. 1, 1 represents a light emitting particle, 1a represents a non-dielectric particle, and 1b represents a light emitting body.

The content of the luminescent material in the luminescent particles is preferably 0.01% by mass or more, more preferably 0.1% by mass or more, and 0.5% by mass or more with respect to the total mass of the luminescent particles. It is more preferable to have. The content of the luminescent material is preferably 10% by mass or less, more preferably 5% by mass or less, and further preferably 1% by mass or less, based on the total mass of the luminescent particles.
The content of the luminescent material in the luminescent particles can be measured by the emission quantum yield.

(Combination of non-dielectric particles and illuminant)
In the light emitting particles of the present invention, it is preferable that the Fermi level of the non-dielectric particles and the HOMO level of the light emitting body are as close as possible. As a result, it is presumed that the holes generated in the non-dielectric particles are easily injected into the HOMO level of the illuminant. Specifically, the difference between the Fermi level of the non-dielectric particles and the HOMO level of the illuminant is preferably 1.0 eV or less, more preferably 0.5 eV or less, and 0.1 eV or less. It is more preferable to have. The HOMO level of the above Cumarin 343 is 5.55 eV, and the Fermi level of non-dielectric particles (ITONPs) made of ITO is 5.06 eV.
In the present specification, the "Fermi level" is a value measured by ultraviolet photoelectron spectroscopy, and the "HOMO level" is a value measured by a photoelectron yield analysis method.
Preferred combinations of non-dielectric particles and illuminants are ITO and Courain 343 combination, ZnO and Fluorescein combination, ITO and F8BT combination, ITO and MEH-PPV combination, FTO and Eu (ETC) combination, ZnO and IrPyC. Combinations can be mentioned. However, the combination of the non-dielectric particle and the illuminant that can be used in the present invention is not limitedly interpreted by these combinations.

(Protective coating)
The luminescent particles of the present invention may be further provided with a protective coating so as to cover the surface of the non-dielectric particles and the luminescent material. As a result, the entire luminescent particles can be stabilized.
Materials for the protective coating include polystyrene-based polymer compounds, polyacrylic acid ester-based polymer compounds, polymethacrylic acid ester-based polymer compounds, silicone-based polymer compounds, polyimide-based polymers, and polyethylene terephthalic acid-based polymer compounds. Examples thereof include alkylamines, alkylcarboxylic acids, and alkylsulfates.
One type of these protective coating materials may be used alone, or two or more types may be used in combination.
The proportion of the protective coating in the luminescent particles is preferably 1 to 1000% by mass, more preferably 1 to 100% by mass, and further preferably 1 to 10% by mass with respect to the total mass of the luminescent particles. preferable.
The proportion of protective coating on the luminescent particles can be measured by thermogravimetric analysis.
The protective film can be formed by an emulsion polymerization method, a surface graft polymerization method, or a specific adsorption method.

[Composition]
The composition of the present invention is characterized by containing the luminescent particles of the present invention and an insulating material.
For a description of the luminescent particles of the present invention and each part constituting the luminescent particles, a preferable range, and specific examples, the above column of (luminescent particles) can be referred to.

The luminescent particles contained in the composition may be all the same type of luminescent particles, or may be a mixture of different types of luminescent particles. For example, when the composition contains two or more types of luminescent particles having different emission wavelengths, it is possible to obtain colored light or white light in which the hues of the light emitted by the luminescent particles are combined.
Examples of the combination of luminescent particles (illuminants) that can obtain white light include a combination of ITO-Columin 354 (orange emission) and FTO-TFB (blue emission).

As the insulating material used in the composition, polystyrene-based polymer compound, polyphenol-based polymer compound, polyacrylic acid ester-based polymer compound, polymethacrylic acid ester-based polymer compound, silicone-based polymer compound, polyimide-based polymer, polyethylene Examples thereof include terephthalic acid-based polymer compounds and polycarbonate-based polymer compounds. Above all, it is preferable to use a polystyrene-based polymer compound.

The content of the luminescent particles in the composition is preferably 0.1% by mass or more, more preferably 1% by mass or more, and further preferably 10% by mass or more with respect to the total mass of the composition. It is preferably 50% by mass or more, and particularly preferably 50% by mass or more. The content of luminescent particles in the composition is preferably 80% by mass or less, more preferably 70% by mass or less, and further preferably 60% by mass or less, based on the total mass of the composition. It is preferably 50% by mass or less, and particularly preferably 50% by mass or less.

The composition of the present invention may be composed of only luminescent particles and an insulating material, or may contain other components. Other components include surfactants such as sodium dodecyl sulfate and stearyl phosphate for promoting dispersion of luminescent particles, anhydrous compounds such as phosphorus oxide as moisture getters, and metals such as copper and zirconium as oxygen getters. can.
The composition may also contain a solvent that dilutes the components. As the solvent, luminescent particles can be dispersed well, and a solvent having compatibility with the resin component can be used.
The composition of the present invention is formed into, for example, a film (film or layer) and is used as a light emitting layer of a light emitting element. The thickness and area of the film formed by the composition can be appropriately selected depending on the intended use.

[Organic electroluminescence element]
The organic electroluminescence device of the present invention is characterized by containing the luminescent particles of the present invention.
The organic electroluminescence element of the present invention has a pair of electrodes (first electrode and second electrode) and a light emitting layer provided between the pair of electrodes, and the light emitting layer contains the light emitting particles of the present invention. It is preferable, and it is more preferable that the light emitting layer is made of the composition of the present invention.
A specific structural example of the organic electroluminescence device is shown in FIG. In FIG. 2, 1 is a light emitting particle, 11 is a substrate, 12 is a first electrode, 13 is a first insulating layer, 14 is a protective layer, 15 is a light emitting layer, 16 is a second insulating layer, and 17 is a second electrode. .. As will be described later, the first insulating layer, the second insulating layer, and the protective layer are provided as needed and may be omitted.
Hereinafter, each part constituting the organic electroluminescence device will be described. However, the above (light emitting particles) column can be referred to for a description of the light emitting particles of the present invention and each part constituting the light emitting particles, a preferable range, and specific examples. In addition, the above column (composition) can be referred to for a description of the composition of the present invention and the components contained in the composition, a preferable range, and specific examples.

(Light emitting layer)
The light emitting layer is a layer that contains at least the light emitting particles of the present invention and emits light after the light emitting body is excited by recombination of holes and electrons generated from the light emitting particles.
The light emitting layer preferably contains light emitting particles and a matrix material that supports the light emitting particles. Examples of the matrix material include an insulating material, a carrier transporting material, a light emitting material, and a material in which a light emitting material and a carrier transporting material are combined. Among them, it is preferable to use an insulating material. The insulating material has high chemical stability, and the element using the insulating material as the matrix material of the light emitting layer exhibits the same characteristics as the element using the carrier transport material as the matrix material of the light emitting layer. Therefore, by using an insulating material for the matrix material of the light emitting layer, it is possible to obtain excellent device characteristics while suppressing oxidative deterioration during the wet process.
For specific examples of the insulating material, the specific examples of the insulating material described in the above [Composition] column can be referred to. The light emitting layer using the insulating material as the matrix material is preferably made of the composition of the present invention.
The carrier-transporting material may be composed of only the hole-transporting material, may be composed of only the electron-transporting material, or may contain both the hole-transporting material and the electron-transporting material. , It is preferable to include both a hole transporting material and an electron transporting material. The hole transporting material and the electron transporting material used for the carrier transporting material are not particularly limited, and can be appropriately selected from known materials. For example, as the hole transport material, PVK or the like used in the examples can be mentioned, and as the electron transport material, BND or the like used in the examples can be mentioned.
When the matrix material is composed of only the light emitting material, the light emitting material is preferably a polymer light emitting material. The polymer light emitting material is not particularly limited, and can be appropriately selected and used from known materials. For example, Green1304, MEH-PPV, F6P2 and the like used in the examples can be mentioned.
When a matrix material is formed by combining a light emitting material and a carrier transporting material, the light emitting material may be a low molecular weight light emitting material or a polymer light emitting material. For the description and specific examples of the polymer light emitting material, the description and specific examples of the polymer light emitting material in the case where the matrix material is composed of only the light emitting material can be referred to. The low-molecular-weight light-emitting material is also not particularly limited, and can be appropriately selected and used from known materials. For example, Coumin6 used in the examples can be mentioned.
When the matrix material contains a light emitting material, the light emitting material may constitute a light emitting body of the light emitting particles of the present invention. That is, the light emitting material of the matrix material may be bonded or adsorbed on the surface of the non-dielectric particles to form the light emitting particles.
In addition to the above materials, the matrix material may contain additives. For specific examples of additives, specific examples of "other components" described in the above [Composition] column can be referred to.

The content of the luminescent particles in the light emitting layer is preferably 0.5% by mass or more, more preferably 1% by mass or more, based on the total mass of the light emitting layer, from the viewpoint of obtaining high luminous efficiency. It is more preferably mass% or more. Further, the content of the light emitting particles in the light emitting layer is preferably 80% by mass or less, more preferably 70% by mass or less, based on the total mass of the light emitting layer, from the viewpoint of uniformly forming the light emitting layer. , 60% by mass or less is more preferable.
The thickness of the light emitting layer is preferably 5000 nm or less, more preferably 1000 nm or less, further preferably 700 nm or less, and particularly preferably 500 nm or less. By making the concentration of the luminescent particles in the light emitting layer higher than the above lower limit value and making the thickness of the light emitting layer thinner than the above upper limit value, it becomes possible to efficiently emit light. The thickness of the light emitting layer is preferably 10 nm or more, more preferably 20 nm or more, further preferably 50 nm or more, and particularly preferably 80 nm or more. As a result, dielectric breakdown in the light emitting layer can be suppressed.

(Insulation layer)
The organic electroluminescence element of the present invention further comprises at least one between the pair of electrodes and the light emitting layer, that is, at least one between the first electrode and the light emitting layer and between the second electrode and the light emitting layer. , An insulating layer may be arranged. As a result, when the matrix material of the light emitting layer is made of an insulating material, even if the concentration of light emitting particles in the light emitting layer is relatively high and the thickness of the light emitting layer is relatively thin, dielectric breakdown in the light emitting layer is caused. It can be suppressed, and both high luminous efficiency and stable driving can be achieved at the same time. The insulating layer may be arranged only between the first electrode and the light emitting layer and between the second electrode and the light emitting layer, or may be arranged in both, depending on the requirement for insulation. It can be appropriately selected accordingly. However, when the matrix material of the light emitting layer is a carrier transporting material, a light emitting material, or a combination of the light emitting material and the carrier transporting material, the space between the first electrode and the light emitting layer and the second electrode and the light emitting layer It is preferable to arrange insulating layers in both of them. As a result, carrier injection from each electrode to the matrix material is reliably blocked, and deterioration of the organic compound (light emitting material or carrier transport material) caused by a large amount of carriers passing through the light emitting layer can be avoided. As a result, both high luminous efficiency and stable driving can be achieved.
Materials for the insulating layer include polyvinylphenol-based polymer compounds, polystyrene-based polymer compounds, polyacrylic acid ester-based polymer compounds, polymethacrylic acid ester-based polymer compounds, silicone-based polymer compounds, polyimide-based polymers, and polyethylene. Examples thereof include terephthalic acid-based polymer compounds, polycarbonate-based polymer compounds, aluminum oxide, silicon oxide, and tantalum oxide. Above all, it is preferable to use a polyvinylphenol-based polymer compound.
The thickness of the insulating layer is preferably 10 nm or more, more preferably 50 nm or more, and further preferably 100 nm or more. The thickness of the insulating layer is preferably 3000 nm or less, more preferably 1000 nm or less, and even more preferably 200 nm or less.

(Protective layer)
Further, in the organic electroluminescence element of the present invention, the light emitting layer is in contact with at least one of the interfaces of the light emitting layer, that is, at least one of the interface on the anode side of the light emitting layer and the interface on the cathode side of the light emitting layer. A protective layer having a positivity with respect to the light emitting layer forming liquid used for the formation may be arranged. Here, "having a lipophilic property with respect to the light emitting layer forming liquid" means that it is difficult to repel the light emitting layer forming solution, and the wettability with respect to the light emitting layer forming solution is opposite to that of the light emitting layer of the protective layer. It is preferably higher than the layer in contact with the side interface. As a result, when the light emitting layer is formed by the wet process, the light emitting layer forming liquid can be applied evenly, and the light emitting layer having a uniform thickness can be formed. From the above points, the protective layer may be arranged on both the upper and lower sides of the light emitting layer, but it is sufficient to arrange the protective layer on only one side so as to form a surface to which the light emitting layer forming liquid is applied. Further, when the above-mentioned insulating layer and protective layer are used in combination, the protective layer is in contact with the interface on the insulating layer side of the light emitting layer and the interface on the light emitting layer side of the insulating layer between the light emitting layer and the insulating layer. Provided. As a result, it is possible to form a light emitting layer having a uniform thickness as compared with the case where the light emitting layer is directly formed on the insulating layer.
Examples of the material of the protective layer include polyvinyl alcohol-based polymer compounds, polyoxyethylene-based polymer compounds, sodium chloride, calcium carbonate and the like. Above all, it is preferable to use a polyvinyl alcohol-based polymer compound.
The appropriate thickness of the protective layer is about 1 to 100 nm.

(1st electrode and 2nd electrode)
The first electrode and the second electrode are not particularly limited as long as a voltage can be applied between the electrodes, but the electrode on the light emitting side is transparent or translucent in order to transmit the emitted light. It is preferably an electrode. In the organic electroluminescence device of the present invention, since the luminescent particles generate carriers by themselves, the electrode materials of the first electrode and the second electrode can be selected from a wide range without emphasizing the carrier injection efficiency.
As the electrode material, metals, alloys, conductive polymer compounds and mixtures thereof can be preferably used. Specific examples of the electrode material include metals such as Cr, Al, Ta, Mo, Nb, Cu, Ag, Au, Pd, In, Ni, Nd, and Co, or alloys and oxides containing these metals, CuI, and tin. Examples thereof include conductive transparent materials such as added indium oxide (ITO), SnO _{2, and ZnO.}
In addition to these, carbon materials such as carbon filaments, carbon nanotubes, graphene, and graphite, those obtained by doping them, conductive polymers such as polythiophene, polypyrrole, and polyethylenedioxythiophene, and those obtained by doping them, etc. The electrode material of can also be preferably used.
The thickness of the electrode is preferably 10 to 3000 nm, more preferably 50 to 500 nm.

(substrate)
The organic electroluminescence device of the present invention is preferably supported by a substrate. The substrate is not particularly limited as long as it is conventionally used for organic electroluminescence devices, and for example, one made of glass, transparent plastic, quartz, silicon, or the like can be used.

The thickness of each layer constituting the above organic electroluminescence device can be measured by using an atomic force microscope. For details of the measurement method, the description in the section of Examples can be referred to.

(Drive system)
The organic electroluminescence device of the present invention is preferably configured as a voltage-modulated light emitting type. The voltage modulation pattern may be a pattern in which voltage application is repeatedly turned on and off, or may be an AC light emitting type in which the sign of the drive voltage is alternately changed, but an AC light emitting type is preferable. The AC frequency in the AC light emitting type is preferably 10 Hz to 10 MHz, more preferably 50 Hz to 1 MHz, and even more preferably 50 Hz to 100 kHz.
In order to drive the organic electroluminescence device of the present invention, for example, a voltage is applied between the first electrode and the second electrode by the above-mentioned driving method to generate an electric field. As a result, holes and electrons are generated from the non-dielectric particles of the light emitting particles contained in the light emitting layer, and the energy generated by the recombination of the holes and electrons causes the light emitting body supported by the non-dielectric particles to emit light. do.

[Manufacturing method of organic electroluminescence device]
The method for producing an organic electroluminescence element of the present invention is characterized by having a step of forming a light emitting layer by a wet process using the liquid for forming a light emitting layer containing the light emitting particles of the present invention. The light emitting layer forming solution is preferably a solution obtained by diluting the composition of the present invention with a solvent.
Examples of the solvent include toluene, xylene, benzene, chlorobenzene, dichlorobenzene, tetrahydrofuran, chloroform, ethyl methyl ketone, acetone, phenyl ethyl ketone, diethyl ether, dimethyl formamide, ethyl acetate, butyl acetate and methyl propionate. ..
Examples of the coating method used in the wet process include a dipping method, a spin coating method, a casting method, a micro gravure coating method, a gravure coating method, a bar coating method, a roll coating method, a wire bar coating method, a dip coating method, and a spray coating method. , Screen printing method, flexographic printing method, offset printing method, inkjet method, microcontact printing method, and one or a combination of two or more of these can be used. Above all, it is preferable to use the inkjet method.
The light emitting layer can be formed by applying the light emitting layer forming liquid by the above coating method, solidifying by drying, and heat-treating if necessary.

The layer other than the light emitting layer of the organic electroluminescence device may be formed by either a wet process or a vapor phase process, but is preferably formed by a wet process, and is arranged between the pair of electrodes and the pair of electrodes. Most preferably, all layers are formed by a wet process. In the wet process, the film can be formed in a short time without using a large-scale film forming apparatus as used in the gas phase process. Therefore, by manufacturing the organic electroluminescence device by using a wet process, it is possible to contribute to the cost reduction of the organic electroluminescence device.

As the coating liquid used in the wet process, a liquid resin material obtained by diluting the material with a solvent can be used in the formation of the above-mentioned insulating layer and protective layer, and a conductive paste is used in the formation of the anode and the cathode. Or a liquid material containing a conductive polymer compound or the like can be used. Here, the conductive paste is a paste in which conductive particles such as Ag particles are dispersed in a resin or a solvent. Examples of the conductive particles include Ag particles and particles made of the above-mentioned metals, alloys, and metal oxides exemplified as electrode materials. In addition, carbon materials such as carbon filaments, carbon nanotubes, graphene, and graphite, those obtained by doping them, conductive polymers such as polythiophene, polypyrrole, and polyethylenedioxythiophene, and those obtained by doping them, etc. Conductive particles can also be preferably used.

The features of the present invention will be described in more detail with reference to Examples below. The materials, treatment contents, treatment procedures, etc. shown below can be appropriately changed as long as they do not deviate from the gist of the present invention. Therefore, the scope of the present invention should not be construed as limited by the specific examples shown below. The brightness is measured using a brightness meter (Topcon: BM-5A), and the emission spectrum is measured using a multi-channel spectroscope (Hamamatsu Photonics: PMA-11). The measurement of the emission waveform with respect to the pulse voltage was performed using a photomultiplier tube (manufactured by Hamamatsu Photonics Co., Ltd .: R649) and a digital oscilloscope (Tektro 620B). The thickness of each layer (thin film) constituting the element is determined by observing the glass surface and the thin film after partially scraping the thin film using an atomic force microscope (manufactured by Seiko Instruments Inc .: Nanopix 100). It was measured by performing an axial analysis.

[Non-inducing electroparticles used, organic materials and luminescent particles]
Table 1 shows the non-dielectric particles and organic compounds used in this example.

(Preparation Example 1) Preparation of luminescent particles 1 The luminescent particles 1 used in this example were prepared as follows.
To 0.1 mL of a slurry of ITO (Indium Tin Oxide) nanoparticles having an average particle size of 30 nm, 0.344 mL of a chloroform solution of 0.02 M Coumarin 343 was added, and the mixture was stirred overnight to chemically chemically Coumarin 343 on the surface of the ITO nanoparticles. It was adsorbed to obtain luminescent particles 1.

[Evaluation of photoluminescence characteristics of luminescent particles 1]
A toluene solution of PS (30 mg / mL) and a slurry of luminescent particles 1 prepared in Preparation Example 1 are mixed so that the content of the luminescent particles 1 is 10% by weight based on the weight of PS to prepare the composition 1. Prepared. This composition 1 was dropped onto a glass substrate, and the substrate was rotated at 500 rpm for 3 seconds, then spun coated at 3000 rpm for 30 seconds, spin-coated, and vacuum dried for 5 hours to obtain a layered composition 1.
Separately, 0.06 mL of Coumin 343 was added to a toluene solution of PS (30 mg / mL) to prepare Comparative Composition 1. A layered comparative composition 1 was obtained in the same manner as in the above steps except that the comparative composition 1 was used in place of the composition 1.
The results of measuring the emission spectra of the layered composition 1 and the comparative composition 1 with the excitation light of 425 nm are shown in FIG. 3, and the photoluminescence quantum yield and the emission maximum wavelength are shown in Table 2.

The emission spectrum of the composition 1 containing the luminescent particles 1 showed an increase in emission intensity near 560 nm as compared with the emission spectrum of the composition 2 to which Coumarin 343 was directly added. It is considered that this is due to the emission of Coumarin 343 chemically adsorbed on the ITO particles.

[Manufacture and evaluation of organic electroluminescence device using luminescent particles 1]
(Example 1)
A 2-propanol solution of PVP (30 mg / mL) was dropped onto a glass substrate on which a first electrode made of ITO (Indium Tin Oxide) having a film thickness of 150 nm was formed, spin-coated at 3000 rpm for 30 seconds, and then in the air. A first insulating layer having a thickness of 170 nm was formed by annealing at 80 ° C. for 30 minutes. Next, an aqueous solution of PVA (0.5% by weight) was dropped onto the first insulating layer, spin-coated at 4000 rpm for 90 seconds, and then annealed in the air at 110 ° C. for 30 minutes to achieve a thickness of 5 nm. Protective layer was formed.
Next, a toluene solution of PS (polystyrene) (30 mg / mL) and a slurry of luminescent particles 1 prepared in Preparation Example 1 are mixed so that the content of the luminescent particles 1 is 10% by weight based on the weight of PS. A liquid for forming a light emitting layer was prepared. This liquid for forming a light emitting layer was dropped onto the protective layer, rotated at 500 rpm for 3 seconds, then spun coated at 3000 rpm for 30 seconds, and vacuum dried for 5 hours to form a light emitting layer having a thickness of 170 nm. ..
Next, a 2-propanol solution of PVP (30 mg / mL) was added dropwise onto the light emitting layer, spin-coated at 3000 rpm for 30 seconds, and then annealed in the air at 80 ° C. for 30 minutes to obtain a thickness of 170 nm. A second insulating layer was formed. Next, Al was vapor-deposited on the second insulating layer to a thickness of 50 nm ^{at a vacuum degree of 3.0 × 10 -4 Pa or less by a vacuum vapor deposition method to form a second electrode.}
Through the above steps, the element 1 which is an organic electroluminescence element was produced.

(Example 2)
The device 2 was produced in the same manner as in Example 1 except that the light emitting layer was formed as follows.
A toluene solution (50 mg / mL) having a PVK: BND (weight ratio) of 65:35 and a slurry of luminescent particles 1 prepared in Preparation Example 1 were prepared, and the content of the luminescent particles 1 was based on the total weight of PVK and BND. A liquid for forming a light emitting layer mixed so as to be 10% by weight was prepared. This liquid for forming a light emitting layer was dropped onto the protective layer, spin coated at 8000 rpm for 30 seconds, and vacuum dried for 5 hours to form a light emitting layer having a thickness of 400 nm.
Table 3 shows the layer structure of the manufactured elements 1 and 2. The numbers in parentheses in Table 3 are layer thicknesses.

An AC voltage or a pulse voltage was applied to the elements 1 and 2, and the light emission characteristics and the electrical characteristics were evaluated. The luminance-voltage characteristics when an AC voltage of 100 kHz is applied to the elements 1 and 2, are shown in FIG. 4, the emission spectrum is shown in FIG. 5, and the threshold voltage V _th and the maximum luminance L _MAX are shown in Table 4. The brightness-frequency characteristics of the element 1 are shown in FIG. 6, and the brightness-frequency characteristics of the element 2 are shown in FIG. The emission waveforms when a sine wave voltage of 1 kHz, 10 kHz or 100 kHz is applied to the element 1 are shown in FIGS. 8 to 10, and the emission waveforms when a sine wave voltage of 1 kHz, 10 kHz or 100 kHz is applied to the element 2 are shown in FIGS. It is shown in 13. The emission waveform of the element 1 with respect to the triangular wave voltage is shown in FIG. 14, and the emission waveform with respect to the rectangular wave voltage is shown in FIG. The emission waveform of the element 2 with respect to the triangular wave voltage is shown in FIG. 16, and the emission waveform with respect to the rectangular wave voltage is shown in FIG. The emission waveforms and electrical characteristics of the element 1 with respect to the bipolar trapezoidal pulse voltage are shown in FIGS. 18 to 21, and the emission waveforms and electrical characteristics of the element 2 with respect to the bipolar trapezoidal pulse voltage are shown in FIGS. 22 to 25. Regarding the electrical characteristics, the electric field strength F, the accumulated charge amount Q _ext , and the current density I were measured.

From the results shown in FIGS. 4 to 25 and Table 4, it was confirmed that all of the elements 1 and 2 operated as a voltage-modulated light-emitting type organic electroluminescence device, and excellent light-emitting characteristics were obtained. Further, from this, it was found that sufficient light emission can be obtained if the light emitting body is present in the immediate vicinity of the non-dielectric particles even if the light emitting body is not present in the entire light emitting layer, and the light emitting particles of the present invention can be obtained. It was confirmed that the light emission was extremely efficient. Further, the element 1 in which the luminescent particles 1 are dispersed in the insulating material (PS) and the element 2 in which the luminescent particles 1 are dispersed in the mixture of the hole transporting material (PVK) and the electron transporting material (BND) are the same. These emission characteristics and electrical characteristics were obtained, suggesting that the carriers generated from the non-dielectric particles hardly move in the light emitting layer and are trapped in the vicinity of the light emitting particles. Further, when the characteristics of the device manufactured in the same manner as in Example 1 were evaluated except that the light emitting layer was formed by using PVP instead of PS, excellent light emitting characteristics were obtained as in the device 1. Was made.
In addition, the following were considered from the results shown in each figure.
First, in the luminance-frequency characteristics of the elements 1 and 2 shown in FIGS. 6 and 7, since the luminance increases as the frequency increases, the luminescent particles generate carriers at each AC voltage cycle and emit light. I found out that I was doing it.
Further, in the emission waveforms for the sine wave voltages of the elements 1 and 2 shown in FIGS. 8 to 13, since the emission peak corresponds to the voltage peak, it can be seen that the emission particles emit light following the voltage peak. rice field. Furthermore, since no deviation is observed in the position of the emission peak even if the frequency changes, the emission process of the emission particles (the process from carrier generation to emission recombination) follows even with an electric field change at 100 kHz. It turned out to be done. Further, in the emission waveforms for the triangular wave voltage and the rectangular wave voltage shown in FIGS. 14 to 17, the coincidence between the voltage peak and the emission peak was observed as seen in the case of the sine wave voltage. Here, since the generation of carriers is considered to be maximized where the electric field strength is maximum, the result showing the coincidence between these voltage peaks and the emission peaks is that the generation of carriers and the emission in the luminescent particles occur almost at the same time. It suggests.
Next, looking at the emission waveforms for the bipolar trapezoidal pulse voltage shown in FIGS. 18 and 22, the emission peaks of the elements 1 and 2 are recognized at the rising edge of the voltage. On the other hand, looking at FIGS. 21 and 25, it can be seen that the external current slightly increases at the rise of this voltage. It is considered that this external current is caused by the generation of carriers inside the light emitting layer, and since the peak position of the external current and the emission peak coincide with each other, it is supported that the light emission in the luminescent particles occurs at the time of carrier generation. Was done.

[Manufacture and evaluation of an organic electroluminescence element in which non-dielectric particles are dispersed in a matrix material made of a light emitting body to form a light emitting layer]
(Example 3)
A 2-propanol solution of PVP (75 mg / mL) was dropped onto a glass substrate on which a first electrode made of ITO (Indium Tin Oxide) having a film thickness of 150 nm was formed, spin-coated at 3000 rpm for 30 seconds, and then in the air. A first insulating layer having a thickness of 500 nm was formed by annealing at 80 ° C. for 30 minutes.
Next, a toluene solution (60 mg / mL) containing PVK, BND and Coumin6 was prepared. This toluene solution was prepared with a PVK: BND (weight ratio) of 65:35 and a concentration of Coumin6 of 0.5 mol% with respect to the total amount of PVK and BND. This toluene solution and an ITO nanoparticle slurry having an average particle size of 30 nm were mixed so that the content of ITO particles was 10% by weight based on the total weight of PVK and BND to prepare a liquid for forming a light emitting layer. This liquid for forming a light emitting layer was dropped onto the first insulating layer, spin coated at 3000 rpm for 30 seconds, and vacuum dried for 5 hours to form a light emitting layer having a thickness of 650 nm.
Next, a 2-propanol solution of PVP (75 mg / mL) was added dropwise onto the light emitting layer, spin-coated at 3000 rpm for 30 seconds, and then annealed in the air at 80 ° C. for 30 minutes to obtain a thickness of 500 nm. A second insulating layer was formed. Next, Al was vapor-deposited on the second insulating layer to a thickness of 50 nm ^{at a vacuum degree of 3.0 × 10 -4 Pa or less by a vacuum vapor deposition method to form a second electrode.}
Through the above steps, the element 3 which is an organic electroluminescence element was produced.

(Example 4)
Using a chloroform solution of Green1304 (15 mg / mL) instead of the toluene solution containing PVK, BND and Coumarin6, a liquid for forming a light emitting layer having an ITO particle content of 10% by weight based on the weight of Green1304 was prepared. Then, the element 4 was produced in the same manner as in Example 3 except that a light emitting layer having a thickness of 160 nm was formed by using this light emitting layer forming liquid.

(Example 5)
Using a toluene solution of MEH-PPV (6 mg / mL) instead of the toluene solution containing PVK, BND and Coumarin6, a light emitting layer having an ITO particle content of 10% by weight based on the weight of MEH-PPV was formed. An element 5 was produced in the same manner as in Example 3 except that a solution was prepared and a light emitting layer having a thickness of 60 nm was formed using the solution for forming a light emitting layer. However, the spin coating of the light emitting layer forming composition was performed at 500 rpm for 30 seconds.

(Example 6)
Using a toluene solution of F6P2 (40 mg / mL) instead of the toluene solution containing PVK, BND and Coumarin6, a liquid for forming a light emitting layer having an ITO particle content of 10% by weight based on the weight of F6P2 was prepared. Then, the element 6 was produced in the same manner as in Example 3 except that the light emitting layer having a thickness of 270 nm was formed by using the light emitting layer forming liquid. However, the spin coating of the light emitting layer forming composition was performed at 1000 rpm for 30 seconds.

Table 5 shows the layer structure of the manufactured elements 3 to 6. The numbers in parentheses in Table 5 are layer thicknesses.

An AC voltage or a pulse voltage was applied to the elements 3 to 6 to evaluate the light emission characteristics and the electrical characteristics. The luminance-voltage characteristics when an AC voltage of 100 kHz is applied to the elements 3 to 6, are shown in FIG. 26, the emission spectrum is shown in FIG. 27, and the threshold voltage V _th and the maximum luminance L _MAX are shown in Table 6. The brightness-frequency characteristics of the element 3 are shown in FIG. 28, the brightness-frequency characteristics of the element 4 are shown in FIG. 29, the brightness-frequency characteristics of the element 5 are shown in FIG. 30, and the brightness-frequency characteristics of the element 6 are shown in FIG. show. The emission waveforms when a sine wave voltage of 1 kHz, 10 kHz or 100 kHz is applied to the element 3 are shown in FIGS. 32 to 34, and the emission waveforms when a sine wave voltage of 1 kHz, 10 kHz or 100 kHz is applied to the element 4 are shown in FIGS. 35 to 35. Shown in FIG. 37, the emission waveforms when a sine wave voltage of 1 kHz, 10 kHz or 100 kHz is applied to the element 5, are shown in FIGS. 38 to 40, and the emission waveforms when a sine wave voltage of 1 kHz, 10 kHz or 100 kHz is applied to the element 6. Is shown in FIGS. 41 to 43. The emission waveforms and electrical characteristics of the element 3 with respect to the bipolar trapezoidal pulse voltage are shown in FIGS. 44 to 47, and the emission waveforms and electrical characteristics of the element 4 with respect to the bipolar trapezoidal pulse voltage are shown in FIGS. 48 to 51. The emission waveform and electrical characteristics are shown in FIGS. 52 to 55, and the emission waveform and electrical characteristics of the element 6 with respect to the bipolar trapezoidal pulse voltage are shown in FIGS. 56 to 59. Regarding the electrical characteristics, the electric field strength F, the accumulated charge amount Q _ext , and the current density I were measured. Further, FIG. 60 shows an emission waveform when pulse voltages having different codes at 1 Hz, 10 Hz, 100 Hz, 1 kHz or 10 kHz are alternately applied to the element 3, and the code is at 1 Hz, 10 Hz, 100 Hz, 1 kHz or 10 kHz on the element 4. The emission waveform when different pulse voltages are applied alternately is shown in FIG. The scale on the horizontal axis in FIGS. 60 and 61 is a scale when the frequency of the pulse voltage is 10 kHz. Since the emission waveforms in FIG. 61 match at all frequencies, the notation of the frequency for each emission waveform is omitted.

From the results shown in FIGS. 26 to 61 and Table 6, it was confirmed that all of the elements 3 to 6 operated as a voltage-modulated light emitting type organic electroluminescence device, and excellent light emitting characteristics could be obtained.
Furthermore, from the results shown in each figure, the following features were recognized in the elements 3 to 6.
First, looking at the luminance-voltage characteristics shown in FIG. 26, a large difference was observed in the driving voltage at the start of light emission between the elements 3 to 6, while a large difference was observed in the maximum luminance, and the element 4 showed. It showed the highest brightness (236.3 cd / m ^2).
Next, looking at the emission waveforms for the sine wave voltage shown in FIGS. 32 to 43, no deviation in the emission peak position due to the frequency change was observed in all the elements, and the emission process (carrier It was found that the process from generation to luminescence recombination) can be followed. However, while the emission peaks of the elements 3 and 6 coincide with the voltage peaks, the emission peaks of the elements 4 and 5 were observed at the moment when the positive and negative of the electric field were switched. Further, from the emission waveforms for the bipolar trapezoidal pulse voltage shown in FIGS. 44, 48, 52, and 56, the emission peaks of the elements 3 and 6 are recognized at the rising edge of the voltage, but the emission peaks of the elements 4 and 5 are observed at the falling edge of the voltage. Admitted. These facts indicate that the elements 3 and 6 and the elements 4 and 5 emit light by different drive mechanisms.
On the other hand, paying attention to the external currents in FIGS. 47, 51, 55 and 59, an increase in the current value was observed at the rise of the voltage in all the elements. This is considered to be due to the generation of carriers from ITO nanoparticles. Therefore, it is considered that the elements 3 and 6 in which the emission peak is observed at the rise of the voltage emit light when the carrier is generated. On the other hand, in the elements 4 and 5, a decrease in the current value was observed at the fall of the voltage. It is considered that this is because the carriers in the light emitting layer are reduced due to the light emission recombination. Therefore, it was suggested that in the elements 4 and 5 in which the emission peak was observed at the time of the voltage fall, the carriers accumulated at the time of the voltage rise were used for the light emission recombination at the time of the voltage fall.
Further, looking at the emission characteristics with respect to the periodic change of the bipolar pulse voltage shown in FIGS. 60 and 61, in the element 3, when the frequency of the bipolar pulse voltage was lowered (when the period was lengthened), the intensity of the first emission peak decreased. It is considered that this is because the carriers generated from the ITO nanoparticles are trapped and accumulated. When a reverse voltage is applied while the carriers are accumulated, it is considered that new carriers are generated from the ITO nanoparticles and luminescence recombination occurs with the accumulated carriers. On the other hand, in the element 4, such a decrease in the emission peak intensity was not observed. This indicates that the element 4 does not accumulate carriers due to the trap, and the carriers generated from the ITO nanoparticles are used for light emission when the voltage returns to zero.
From these results, it was found that when the light emitting layer was formed by dispersing the non-dielectric particles in the matrix material composed of the light emitting body, the driving mechanism changed depending on the difference in the light emitting body. It was suggested that this difference in the driving mechanism is caused by the difference in the trapped state of the carriers in the light emitting layer.

[Modification example of organic electroluminescence device using PS as matrix material of light emitting layer]
(Example 7)
To 1 mL of a slurry of ITO (Indium Tin Oxide) nanoparticles having an average particle size of 30 nm, 0.344 mL of a 0.02 M Coumarin 343 chloroform solution was added, and the mixture was stirred for 24 hours to obtain ITO particles chemically adsorbed on the surface of Coumarin 343. rice field. Further, ITO particles in which Coumarin 343 was chemically adsorbed on the surface were obtained in the same manner except that the amount of Coumarin 343 added to the chloroform solution was changed to 5 times, 7.5 times or 10 times. The slurry of these luminescent particles was mixed with a toluene solution of PS so that the content of the luminescent particles was 1% by weight based on the weight of PS to prepare a liquid for forming a light emitting layer.
Next, each light emitting layer forming solution was dropped onto a glass substrate on which a first electrode made of ITO (Indium Tin Oxide) having a film thickness of 150 nm was formed, and the substrate was rotated at 300 rpm for 3 seconds and then at 3000 rpm. A light emitting layer having a thickness of 650 nm was formed by spinning for 30 seconds, spin coating, and annealing at 80 ° C. for 1 hour.
Next, Al was vapor-deposited on the light-emitting layer to a thickness of 60 nm ^{at a vacuum degree of 3.0 × 10 -4 Pa or less by a vacuum vapor deposition method to form a second electrode.}
Through the above steps, four types of organic electroluminescence (elements 7-1 to 7-4) having different amounts of Coumarin 343 adsorbed on the luminescent particles were produced.
The luminance-voltage characteristics when an AC voltage of 100 kHz is applied to the elements 7-1 to 7-4 are shown in FIG. 62, and the threshold voltage V _th and the maximum luminance L _max are shown in Table 7.

From FIG. 62 and Table 7, it was found that the driving voltage became smaller as the amount of adsorption of Coumin 343 in the luminescent particles increased.

(Example 8)
An insulating layer made of lithium fluoride (LiF), polychloroparaxylene (PCPX), or polyvinylphenol (PVP) has a thickness of 170 nm between the first electrode and the light emitting layer and between the second electrode of the light emitting layer. An organic electroluminescence element (elements 8-1 to 8-3) was produced in the same manner as in the element 7-4 of Example 7 except that the element was formed in 1. Table 8 shows the material of the insulating layer used in each element.

When the insulation and brightness of the insulating layer were evaluated for the elements 8-1 to 8-3, the insulating property of the element 8-1 using lithium fluoride as the insulating layer was insufficient and no light emission was observed. In addition, in the element 8-2 using polychloroparaxylene as the insulating layer, although the insulating property was improved, no light emission was observed. On the other hand, in the element 8-3 in which polyvinylphenol was used as the insulating layer, the insulating property was improved and light emission was also observed.

The luminescent particles of the present invention can emit light without supplying carriers from the outside. Therefore, by using the luminescent particles of the present invention, it is not necessary to inject carriers from the anode and the cathode, and it is possible to realize an organic electroluminescence element that can surely avoid deterioration of the organic compound due to a high density current in the organic layer. Can be done. Therefore, the present invention has high industrial applicability.

1 Light emitting particles 1a Non-dielectric particles 1b Light emitting body 11 Substrate 12 First electrode 13 First insulating layer 14 Protective layer 15 Light emitting layer 16 Second insulating layer 17 Second electrode

Claims (14)

A non-dielectric particles, a light-emitting particles having a light emitter combined binding to the surface of the non-dielectric particles,
The luminescent material is bonded to the surface of the non-dielectric particles by a chemical reaction of the functional group of the precursor of the luminescent material on the surface of the non-dielectric particles.
The precursor of the luminescent material is a luminescent particle which is an organic compound containing a functional group selected from a carboxy group, a phosphoric acid group and an amino group. The luminescent particle according to claim 1, wherein the non-dielectric particle is an oxide semiconductor particle. The luminescent particles according to claim 1 or 2, wherein the non-dielectric particles have a particle size of 100 nm or less. A composition comprising the luminescent particles according to any one of claims 1 to 3 and an insulating material. The composition according to claim 4, wherein the light emitting particles include two or more types of light emitting particles having different emission wavelengths, and the synthetic color obtained by combining the hues of the light emitted by the two or more types of light emitting particles is white. An organic electroluminescence device comprising the luminescent particles according to any one of claims 1 to 3. It has a pair of electrodes and a light emitting layer provided between the pair of electrodes.
The organic electroluminescence device according to claim 6, wherein the light emitting layer contains the light emitting particles. It has a pair of electrodes and a light emitting layer provided between the pair of electrodes.
An organic electroluminescence device, wherein the light emitting layer comprises the composition according to claim 4 or 5. The organic electroluminescence device according to claim 7 or 8, wherein an insulating layer is provided on at least one of the pair of electrodes and the light emitting layer. The organic electroluminescence device according to any one of claims 6 to 9, which is a voltage-modulated light emitting type. The organic electroluminescence device according to claim 10, which is an AC light emitting type. A method for producing an organic electroluminescence element, which comprises a step of forming a light emitting layer by a wet process using the light emitting layer forming liquid containing the light emitting particles according to claim 1. The method for manufacturing an organic electroluminescent device according to claim 12, wherein all the layer forming steps are performed by using a wet process. The method for producing an organic electroluminescent device according to claim 12 or 13, which uses an inkjet method in the wet process.

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