JP2007112831A - Light-emitting particle, method for producing the same and light-emitting device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide light-emitting particles capable of realizing a high moisture resistance and highly brightening property simultaneously. <P>SOLUTION: The light-emitting particles are provided by covering the surface of the particles with a covering membrane consisting mainly of an organic carbon and containing ≥1 kind of an element among H, N, O, Si and F. Another example of the light-emitting particles is provided by covering the surface of the particles with a covering membrane consisting mainly of an amorphous inorganic carbon. Also the covering membrane may further contain at least ≥1 kind of an element among H, N and F. Further the light-emitting device is equipped with a light-emitting material layer containing the light-emitting particles, a dielectric material layer installed on at least one of the surfaces of the light-emitting layer and a pair of electrodes for impressing an electric field, installed as nipping the light-emitting material layer and dielectric material layer. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a phosphor particle that emits electroluminescence by applying a voltage, a method for producing the phosphor particle, and a light-emitting device using the phosphor particle.

  Since the phosphor emits light when excited by an electric field, electron beam or ultraviolet ray, it is used in various products for displays, flat light sources, and cathode ray tube phosphors. Light-emitting elements using inorganic phosphors such as zinc sulfide are self-luminous, have excellent visibility, have a wide viewing angle, and have a fast response speed, making them suitable for display devices such as TV displays and PC displays. The application of is expected. Against this background, various proposals have been made with the aim of putting EL elements having high emission luminance and low cost into practical use. In addition, there is an electroluminescent (hereinafter referred to as EL lamp) lamp in which a phosphor is mixed and dispersed in an organic resin.

  However, in this EL lamp, there is a problem that the phosphor is weak in humidity, and luminance degradation and efficiency reduction are remarkably generated. For this reason, it is an important technical problem to improve the moisture resistance of the phosphor particles. On the other hand, in order to obtain high luminance with a low applied voltage, it is necessary to reduce the thickness of the coating film. Further, in order to make the phosphor coating layer thinner, it is necessary to reduce the particle diameter of the phosphor particles. There is a strong demand for a phosphor coated with a thin coating film having excellent moisture resistance to satisfy both high luminance and moisture resistance.

  In order to solve this problem, many proposals for covering the phosphor surface with a protective film have been made. For example, in order to improve the moisture resistance of the phosphor, a method of coating the surface of the phosphor particles with a metal oxide has been disclosed (see, for example, Patent Document 1). In this method, a metal oxide film is formed from a metal alkoxide oligomer on the surface of fluidized phosphor particles. In addition, a method has been proposed in which a salt of a metal compound is dissolved in a melt of an organic material that exhibits polarity by melting on the phosphor surface to form a coating layer on the phosphor particle surface (for example, Patent Document 2). reference.).

  Furthermore, a technique for forming an oxide on the surface of the phosphor particles in the gas phase has also been proposed. For example, a reactive gas is introduced between electrodes under a pressure of atmospheric pressure or near atmospheric pressure to generate plasma, and a phosphor is exposed to the reactive gas in the plasma state to form an oxide film on the surface. A method has been proposed (see, for example, Patent Document 3).

JP-A-9-263653 JP 2004-137482 A JP 2003-336046 A

  However, in all of the conventional methods, the coating film for coating the phosphor is a metal oxide, nitride, oxynitride, sulfide, oxysulfide, etc. There are problems such as holes. Moreover, these coating materials are essentially hard and brittle. For this reason, the above-described defects are likely to occur, and as a result, there is a problem in reliability such as moisture resistance. Furthermore, the smaller the particle size of the phosphor particles and the thinner the coating film, the higher the necessity of pinholes and degradation of film quality, and the compatibility between thin coating film and moisture resistance. There was a problem that could not be enough.

  An object of the present invention is to solve the conventional problems and to provide phosphor particles that can simultaneously realize high luminance and low price and an EL device using the same.

  The phosphor particles according to the present invention are characterized in that the particle surface is coated with a coating film mainly composed of organic carbon and containing one or more elements selected from H, N, O, Si, and F. “Organic carbon” means carbon constituting an organic substance.

The coating film may contain a [—CH ₂ —] component. Further, the coating film may include a network of [—CH ₂ —] components.

  The phosphor particles according to the present invention are characterized in that the particle surfaces are coated with a coating film mainly composed of amorphous inorganic carbon. “Inorganic carbon” means elemental carbon. In addition, “amorphous” means a material that does not show a clear crystal structure by X-ray diffraction.

  The coating film may further include at least one element selected from H, N, and F. Furthermore, the coating film may include a diamond-like carbon film.

  Furthermore, the film thickness of the coating film covering the particle surface may be 1 nm to 1000 nm.

A light-emitting device according to the present invention comprises a phosphor layer containing the phosphor particles,
A dielectric layer provided on at least one surface of the phosphor layer;
It is provided with a pair of electrodes which are provided with the light emitting layer and the dielectric layer interposed therebetween and which apply an electric field.

The method for producing phosphor particles according to the present invention introduces a raw material gas containing carbon as a main component and containing one or more elements from H, N, O, Si, and F into an apparatus having a predetermined degree of vacuum. And steps to
Generating a plasma discharge in the apparatus;
Phosphor particles are supplied into the apparatus that has generated plasma discharge, the surface of the phosphor particles mainly includes organic carbon, and one or more kinds of elements are selected from H, N, O, Si, and F. And a step of covering with a covering film.

The method for producing phosphor particles according to the present invention includes supplying phosphor particles in an apparatus;
Evacuating the apparatus to a predetermined degree of vacuum;
Introducing a source gas mainly containing carbon into the apparatus;
And generating a plasma discharge in the apparatus to coat the surface of the phosphor particles with a coating film mainly containing amorphous inorganic carbon.

  The source gas may contain one or more elements from H, N, O, Si, and F. Thus, the coating film contains one or more elements from H, N, O, Si, and F.

  According to the phosphor particles according to the present invention, since it is dense and has a high moisture-proof effect and a thin coating film is formed, it has high moisture resistance and high brightness applicable to displays such as EL lamps and televisions. Can be realized at the same time.

  A phosphor particle and a light emitting device using the phosphor particle according to an embodiment of the present invention will be described with reference to the accompanying drawings. In the drawings, substantially the same members are denoted by the same reference numerals.

(Embodiment 1)
FIG. 1 is a cross-sectional view schematically showing a cross-sectional structure of phosphor particles 10 according to Embodiment 1 of the present invention. In this phosphor particle 10, the particle surface of the phosphor core particle 1 is covered with the coating film 2. This coating film 2 contains organic carbon as a main component, and contains at least one element selected from H, N, O, Si, and F. Since the particle surface is coated with the coating film 2 containing organic carbon as a main component, high moisture resistance can be added even when using a light emitting body that easily deteriorates due to the influence of humidity.

The phosphor core particle 1 includes an electroluminescent phosphor, such as ZnS, SrS, BaAl ₂ S ₄ , and CaS, as a base material, a luminescent center, an activator, a coactivator, Cu, What added elements, such as Al, Ag, Mn, Cl, I, can be used. In addition, selenides such as ZnSe, tellurides such as ZnTe, and nitrides such as GaN, GaInN, and GaInAlN, which are light emitters of light emitting diodes, can also be used.

The coating film 2 formed on the surface of the phosphor particles 10 contains organic carbon as a main component as described above, and one or more kinds of H, N, O, Si, and F. It is made of a material containing elements. Since this coating film 2 is organic, it has flexibility. Further, the coating film 2 may include a [—CH ₂ —] component. Furthermore, [- CH ₂ -] may have a network of components. This [—CH ₂ —] component can be detected by Raman spectroscopy, an infrared absorption method such as FT-IR, or the amount measurement of hydrogen atoms by SIMS. Note that elemental components such as H, N, O, Si, and F may be bonded to an organic carbon atom or may be included in the network of the [—CH ₂ —] component. By including these element components, water repellency and moisture resistance are further improved. Moreover, as thickness of the coating film 2, the range of 1 nm-1000 nm is desirable. Even if the thickness of the coating film 2 is about 200 nm, high withstand voltage and moisture resistance can be obtained.

  As a method for forming the coating film 2, a method can be used in which the raw material gas is introduced into high-frequency plasma or microwave plasma, and an appropriate amount of light emitters are put in the plasma to form a coating on the surface.

FIG. 3 is a flowchart of the method for producing luminescent particles according to Embodiment 1 of the present invention.
(A) First, the inside of the apparatus for surface coating is evacuated (S01).
(B) When a predetermined degree of vacuum is reached, the raw material gas and the additive gas are introduced into the apparatus (S02). As a raw material for carbon C, hydrocarbon gases such as CH ₄ , C ₂ H ₄ , and C ₃ H ₈ , C ₂ H ₂ , parylene, and the like can be used. Examples of the additive gas include H ₂ , O ₂ , NH ₃ , N ₂ , NH ₃ , CO ₂ , NO, CF ₄ , fluorocarbon, H ₂ O, C ₂ H ₄ O, SiH ₄ , and SF ₆ . Raw materials can be used. In addition, the [—CH ₂ —] component can be included in the coating film 2 by increasing the hydrogen gas concentration in the source gas and the additive gas.
(C) Plasma discharge is generated in the apparatus (S03). Here, high-frequency power or microwave power with a frequency of 13.56 MHz is supplied to the plasma discharge. Here, the coating film 2 is formed by plasma discharge, but the method is not limited to this as described above.
(D) When plasma discharge occurs, luminescent particles are supplied into the apparatus (S04).
(E) The surface of the phosphor particles is coated with a coating film (S05).
(F) The phosphor particles coated with the particle surface are taken out from the apparatus (S06).
As described above, phosphor particles whose particle surfaces are coated with the coating film 2 mainly composed of organic carbon can be obtained.

When the coating film 2 of the obtained phosphor particles is subjected to compositional element analysis by XMA (X-ray microanalyzer) method, fluorescent X-ray method, Auger analysis, etc., organic carbon is the main component, and in addition, additional gases and materials Thus, each element such as H, N, O, Si, and F is observed. Further, when the hydrogen gas concentration in the source gas and the additive gas is high, the coating film 2 contains a [—CH ₂ —] component. The [—CH ₂ —] component contained in the coating film is also called a polymer component, and it is known that the resistivity of the coating film increases as the polymer component increases. This coating film 2 differs in composition and properties of the film depending on production conditions such as gas type, mixing ratio, gas flow rate, and plasma power. In addition, the coating film 2 contains 20 to 95 atomic% as the total carbon, and the content of one or more elements out of H, N, O, Si, and F is 1 atomic% or more. . This coating film has the mechanical strength of an inorganic material, withstand voltage, and the flexibility of an organic material. Furthermore, it is dense and has very few pinholes. Moreover, by adding additional elements such as H, N, O, Si, and F, the chemical stability of the coating film 2 can be improved and the permeation of moisture can be remarkably prevented, thereby obtaining excellent moisture resistance. Can do.

  The thickness of the coating film 12 can be measured by SEM (scanning electron microscope) observation or TEM (transmission electron microscope) observation of the cross section of the coated phosphor particles. As described above, since this coating film is dense and has high chemical stability, if it is very thin, for example, even if it has a thickness of 200 nm or less, the moisture-proof effect is great. The range of 1 nm to 1000 nm is desirable.

  As described above, this coating film has the mechanical strength of an inorganic material and the flexibility of an organic material, and can significantly improve moisture resistance by an additive element. Further, this coating film is thin and dense and has no pinhole. Therefore, it is possible to obtain phosphor particles having excellent moisture resistance by coating the phosphor particles with the above-described coating film.

FIG. 2 is a cross-sectional view showing the basic configuration of the light-emitting device 20 using the phosphor particles according to Embodiment 1 of the present invention. In the light emitting device 20, a back electrode 22 and a dielectric layer 23 are sequentially formed on a substrate 21, and a light emitter layer 24 including the light emitter particles 10 of the present invention is further provided on the dielectric layer 23. A front electrode 25 is provided on the layer 24. As the back electrode 22, any conductor such as Pt, Pd, Au, Ir, Rh, Ni can be applied. As the dielectric layer 23, any dielectric layer in which dielectric particles are mixed in a resin binder or a dielectric layer such as a dielectric film can be applied. The dielectric particles or dielectric film materials used for the dielectric layer 23 include barium titanate (BaTiO ₃ ), barium strontium titanate (BaSrTiO ₃ ), lead titanate (PbTiO ₃ ), lead zirconium titanate. (PbZrTiO ₃ ), bismuth titanate (BiTiO ₃ , Bi: Ti = 4: 3), strontium titanate (SrTiO ₃ ), bismuth lanthanum titanate (BiLaTiO ₃ , Bi: La: Ti = 3.35: 0.75: 3) is preferable in terms of excellent dielectric characteristics, dielectric strength characteristics, film formation characteristics, and the like. The dielectric layer 23 may be formed by a thin film formation method such as sputtering, sol-gel method, aerosol deposition method, CVD method (chemical vapor phase method), or MOCVD (metal organic chemical vapor phase method).

  The luminous body layer 24 is obtained by mixing luminous body particles in a binder made of a resin material. In this phosphor particle, ZnS: Cu, Cl is used as the phosphor core particle, and a coating film is formed by the method described in the first embodiment.

  The substrate 21 may be any substrate that is used for a normal EL element, such as a plastic substrate, a ceramic substrate, or a glass substrate.

Further, as the front electrode 25, any generally known light-transmitting transparent conductor such as ITO (In ₂ O ₃ doped with SnO ₂ ), InZnO, GaZnO, AlZnO, tin oxide or the like may be used. Applicable. Since the light emitting layer 24 emits light in all directions, the electrode materials described for the back electrode 22 and the front electrode 25 may be replaced when light is extracted from the substrate 21 side.

  On the other hand, in the light-emitting device 20 of the present invention, when the light-emitting diode particles for the light-emitting diode are used for the light-emitting core particles 1, electrons or holes are directly transferred from the electrode to the light-emitting layer 24 without providing the dielectric layer 23. Inject to emit light.

(Embodiment 2)
The phosphor particles according to the second embodiment of the present invention are different from the phosphor particles according to the first embodiment in that the coating film mainly includes an amorphous inorganic carbon film. This coating film may contain a diamond-like carbon film (DLC) as a main component. The covering film may be a tetrahedral amorphous carbon film (ta-C). In addition, the coating film may contain at least one element among the elements H, N, and F in its structure.

  As described above, since this coating film contains amorphous inorganic carbon as a main component, when it is very thin, for example, a high moisture-proof property can be obtained even with a thickness of 200 nm or less. The range of 1 nm to 1000 nm is desirable.

  Compared with the manufacturing method of the phosphor particles according to Embodiment 1, the manufacturing method of the phosphor particles according to Embodiment 2 of the present invention supplies the phosphor particles into the apparatus and introduces the source gas, The difference is that a plasma discharge is generated to form a coating film on the particle surface.

FIG. 4 is a flowchart of the method for producing luminescent particles according to Embodiment 2 of the present invention.
(A) The phosphor particles are supplied into the apparatus (S11).
(B) The inside of the apparatus is evacuated (S12).
(C) The raw material gas is introduced into the apparatus (S13). A hydrocarbon gas such as CH ₄ , C ₂ H ₄ , and C ₃ H ₈ can be used as the source gas. Note that H ₂ , NH ₃ , N ₂ , NH ₃ , CO ₂ , NO, CF ₄ , SiH _4, or the like may be used as the additive gas.
(D) Plasma discharge is generated in the apparatus (S14). The apparatus is rotated to generate plasma discharge such as high-frequency plasma or microwave plasma as in the first embodiment.
(E) The surface of the phosphor particles is coated with a coating film (S15). This coating film is mainly composed of amorphous inorganic carbon containing 60 atomic% or more of carbon.
(F) The phosphor particles are taken out from the apparatus (S16).
As described above, phosphor particles with the particle surface coated can be obtained.

This coating film was found to be a very dense coating film when analyzed by the same method and X-ray diffraction method as in the first embodiment. This coating film was an amorphous inorganic carbon film containing 60 atomic% or more of carbon C. The amorphous inorganic carbon film is a carbon film in which a diffraction pattern showing a clear crystal structure is not observed by an X-ray diffraction method, and includes a diamond-like carbon film. Furthermore, a tetrahedral amorphous carbon film may be included. Since this coating film is an amorphous inorganic carbon film, there is no crystal grain boundary and moisture does not enter. Therefore, the moisture resistance is high. Moreover, the hardness is high and the mechanical strength is also high. Further, when H ₂ , NH ₃ , N ₂ , NH ₃ , CO ₂ , NO, CF ₄ , SiH _4, or the like is used as the additive gas, the coating film becomes an amorphous carbon film with H, N, O, The film contains an additive element such as Si or F. The additive elements H, N, O, Si, and F improve the chemical stability of the film and remarkably prevent moisture permeation, and exhibit excellent moisture resistance.

This coating film can be observed by Raman spectroscopy, infrared absorption methods such as FT-IR, measurement of the amount of hydrogen atoms by SIMS, and the like. In particular, this coating film is characterized in that a peak near 1350 cm ⁻¹ (D-band) and a peak near 1570 cm ⁻¹ (G-band) are observed in the Raman spectrum. On the other hand, in the case of a tetrahedral amorphous carbon film (ta-C), the D-band peak is relatively small depending on the film forming conditions. As a reference, in the case of diamond, it shows a sharp peak around 1350 cm ^-1 in the Raman spectrum, not show a peak in the vicinity of 1570 cm ^-1. In graphite, a peak is observed in the vicinity of 1570 cm ⁻¹ , but no peak is observed in the vicinity of 1350 cm ⁻¹ .

  The phosphor particles according to the present invention are dense, have a high moisture-proof effect, and have a thin coating film, and thus are useful for displays such as EL lamps and televisions.

It is sectional drawing which shows typically the cross section of the light-emitting body particle which concerns on Embodiment 1 of this invention. It is a flowchart of the manufacturing method of the light-emitting body particle which concerns on Embodiment 1 of this invention. It is a perspective view which shows the structure of the light-emitting device which concerns on Embodiment 1 of this invention. It is a flowchart of the manufacturing method of the light-emitting body particle which concerns on Embodiment 2 of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Light-emitting body particle, 11 Light-emitting body core particle, 12 Coating film, 20 Light-emitting device, 21 Substrate, 22 Back electrode, 23 Dielectric layer, 24 Light-emitting body layer, 25 Front electrode

Claims (11)

  A phosphor particle characterized in that the particle surface is coated with a coating film containing organic carbon as a main component and containing one or more elements selected from H, N, O, Si, and F. The phosphor particles according to claim 1, wherein the coating film includes a [—CH ₂ —] component. The phosphor particles according to claim 1, wherein the coating film includes a network of [—CH ₂ —] components.   A phosphor particle, wherein the particle surface is coated with a coating film mainly composed of amorphous inorganic carbon.   The phosphor particles according to claim 4, wherein the coating film further includes at least one element of H, N, and F.   The phosphor particles according to claim 1, wherein the coating film includes a diamond-like carbon film.   The phosphor particle according to any one of claims 1 to 6, wherein the coating film covering the particle surface has a thickness of 1 nm to 1000 nm. A phosphor layer comprising the phosphor particles according to any one of claims 1 to 7,
A dielectric layer provided on at least one surface of the phosphor layer;
A light-emitting device, comprising: a pair of electrodes provided across the light-emitting body layer and the dielectric layer and applying an electric field. Introducing a source gas containing carbon as a main component and containing one or more elements from H, N, O, Si, and F into an apparatus having a predetermined degree of vacuum;
Generating a plasma discharge in the apparatus;
Phosphor particles are supplied into the device that has generated plasma discharge, and the surface of the phosphor particles contains organic carbon as a main component, and one or more elements selected from H, N, O, Si, and F And a step of coating with a coating film comprising: a method for producing phosphor particles coated with a particle surface. Supplying phosphor particles in the apparatus;
Evacuating the apparatus to a predetermined degree of vacuum;
Introducing a source gas mainly containing carbon into the apparatus;
And generating a plasma discharge in the apparatus to coat the surface of the phosphor particles with a coating film mainly containing amorphous inorganic carbon. A method for producing body particles. The source gas contains one or more elements from H, N, O, Si, and F, and the coating film contains one or more elements from H, N, O, Si, and F. The method for producing phosphor particles according to claim 10.

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