WO2013190797A1 - Electroluminescent element - Google Patents

Abstract

Provided is an EL element which can have both improved luminance and improved luminous efficiency without application of high electric field. An EL element (1) is sequentially provided with a first electrode layer (10), a light-emitting body layer (30), and a light-transmitting second electrode layer (40). The EL element (1) is provided with, between the first electrode layer (10) and the light-emitting body layer (30), a needle-like conductor layer (20) which comprises a plurality of needle-like conductors (22) and an insulating body (21) that insulates the plurality of needle-like conductors (22) from each other, said needle-like conductors (22) extending in a direction that intersects with a first electrode layer (10)-side surface (30S) of the light-emitting body layer (30).

Description

Electroluminescence element

The present invention relates to an electroluminescence element.

An inorganic electroluminescent (hereinafter, abbreviated as “EL”) element is a self-luminous element having features such as a large area and a long lifetime.
Conventionally, as an inorganic EL element, a thin film type inorganic EL element and a dispersion type inorganic EL element are known.

A thin-film inorganic EL element is an element in which a light-transmitting lower electrode layer, a light-emitting body layer, and an upper electrode layer are sequentially stacked on a light-transmitting insulating substrate (FIG. 4 of Patent Document 1). reference).
An insulator layer may be provided between the lower electrode layer and the light emitter layer and / or between the light emitter layer and the upper electrode layer.

In the thin-film inorganic EL element, as the luminescent layer material, a material obtained by adding at least one luminescent center element to the base compound is preferably used.
Known parent compounds include II-VI binary compounds such as ZnS, SrS, and CaS, and II-III-VI group ternary compounds such as CaGa ₂ S ₄ , SrGaS ₄ , and BaAl ₂ S _4. ing. Further, examples of the luminescent center element include metal elements such as Mn, Cu, Au, and rare earth.
Examples of the phosphor layer material include ZnS: Mn that exhibits an orange emission color, ZnS: Tb that exhibits a green emission color, and BaAl ₂ S ₄ : Eu that exhibits a blue emission color (paragraph of Patent Document 1). 0004).

When electrons flowing in the luminescent layer collide with the luminescent center element in an electric field, the luminescent center element is excited to emit light. The higher the electron collision energy, the easier the excitation of the luminescent center element. Therefore, a high luminance can be obtained by applying a high electric field. For example, in ZnS: Mn, excitation occurs in an electric field of 1 × 10 ⁶ V / cm or more, and the emission luminance rapidly increases.

On the other hand, the dispersion-type inorganic EL element includes a phosphor layer in which phosphor particles are dispersed in a binder made of a high dielectric resin such as a fluorine-based resin or a cyano group-containing resin, and a pair of electrodes sandwiching the phosphor layer. It is an element provided with a board (refer claim 7 of patent document 2). Usually, the dispersion-type inorganic EL element further includes a dielectric layer in which a dielectric material such as barium titanate is dispersed in a high dielectric resin in order to prevent dielectric breakdown.

Patent Document 2 discloses an EL phosphor powder in which zinc sulfide (ZnS) is used as a base compound and an activator such as Cu and a coactivator such as Cl are added, and an EL element using the same. (Claim 1).
When Cu is used as the activator, excess Cu that is not dissolved in the ZnS crystal is deposited in the gap between the stacking faults to form a needle-like conductor. When an AC voltage is applied to the phosphor particles containing the needle-like conductor, an electric field concentrates on the tip of the needle-like conductor, and a current contributing to light emission flows intensively, thereby 1 × 10 ⁴ V. EL emission can be obtained even at a relatively low electric field of about / cm (see Non-Patent Document 1). As the acicular conductor is perpendicular to the electrode surface, the electric field is more likely to be concentrated, so that high emission luminance is easily obtained. By orienting the (111) crystal plane on which the acicular conductor is deposited, the acicular conductor oriented perpendicular to the electrode surface increases, electric field concentration is likely to occur, and the light emission luminance is improved (Patent Document 2). Paragraph 0005).

JP 2008-251336 A (Patent No. 4928329) Japanese Patent Application Laid-Open No. 2004-131583

In the conventional thin-film inorganic EL element described in Patent Document 1 and the like, attempts have been made to improve light emission characteristics such as light emission luminance and light emission efficiency. However, a high electric field is required to obtain a high light emission luminance, and there is a tendency for the light emission efficiency to decrease because of the large amount of electric power that does not contribute to light emission and becomes heat.

On the other hand, in the conventional dispersion-type inorganic EL element described in Patent Document 2 and the like, a concentrated electric field is generated in the vicinity of the tip of a needle-like conductor such as Cu, so that high emission luminance can be obtained with a relatively low electric field. . However, since the phosphor layer includes phosphor particles and a binder, the electric field applied to the phosphor layer is distributed to both the phosphor particles and the binder. As a result, the power consumed by the binder is large, and the light emission efficiency tends to decrease. Moreover, since acicular conductors such as Cu in the phosphor particles precipitate in multiple directions (random directions) in the crystal plane, the proportion of acicular conductors oriented perpendicular to the electrode surface is small, The electric field is difficult to concentrate.

For the above reasons, it is difficult for both the conventional thin film type inorganic EL element and the dispersion type inorganic EL element to sufficiently improve the light emission luminance and the light emission efficiency.
The above is a problem particularly in the inorganic EL element, but it is preferable that the organic EL element can sufficiently improve the light emission luminance and the light emission efficiency.

The present invention has been made in view of the above circumstances, and an object thereof is to provide an EL element capable of improving both light emission luminance and light emission efficiency without applying a high electric field.

The electroluminescence (EL) element of the present invention is
An electroluminescent device comprising a first electrode layer, a light emitter layer, and a second electrode layer having translucency in order,
Between the first electrode layer and the phosphor layer,
Needle-like conductivity including a plurality of needle-like conductors extending in a crossing direction with respect to the surface on the first electrode layer side of the phosphor layer, and an insulator that insulates between the plurality of needle-like conductors. It has a body layer.

In this specification, “needle” refers to a shape having a length / diameter of 2 or more.

According to the present invention, it is possible to provide an EL element capable of improving both the light emission luminance and the light emission efficiency without applying a high electric field.

1 is an overall schematic cross-sectional view of an EL element according to an embodiment of the present invention. It is a perspective view which shows the manufacturing process of a pore structure. It is a perspective view which shows the manufacturing process of a pore structure. It is a figure which shows the example of a design change of the EL element of FIG. It is a figure which shows the example of a design change of the EL element of FIG. It is an optical microscope image (2000 times) which shows the mode of light emission of the EL element obtained in Example 1. FIG. It is an optical microscope image (2000 times) which shows the mode of light emission of the EL element obtained by the comparative example 1.

"EL element"
With reference to the drawings, the structure of an EL device according to an embodiment of the present invention will be described.
FIG. 1 is an overall schematic cross-sectional view of the EL element of the present embodiment.
2A to 2B are schematic perspective views showing the manufacturing process of the pore structure.
3 and 4 are diagrams showing examples of design changes.
1, 3, and 4, the same components are denoted by the same reference numerals.

As shown in FIG. 1, the EL element 1 of the present embodiment includes a lower electrode layer (first electrode layer) 10, a light emitter layer 30, and a translucent upper electrode layer (second electrode layer) 40. Are sequentially provided.
The EL element 1 further includes a plurality of needle-like conductors 22 extending between the lower electrode layer 10 and the light emitter layer 30 in a direction intersecting the surface 30S of the light emitter layer 30 on the lower electrode layer 10 side. The needle-shaped conductor layer 20 including an insulator that insulates between the plurality of needle-shaped conductors 22 is provided.

In the present embodiment, the insulator forming the acicular conductor layer 20 is open on the surface on the light emitter layer 30 side, and has a plurality of acicular pores 21P extending in the intersecting direction with respect to the surface on the light emitter layer 30 side. It is the pore structure 21 which has. A plurality of needle-like conductors 22 are formed inside the plurality of needle-like pores 21P.

In the present embodiment, the pore structure 21 is a metal oxide body obtained by anodizing a part of the anodized metal body, and the lower electrode layer 10 is the remaining portion of the anodized metal body remaining after anodization. .

The main component of the metal to be anodized is not particularly limited, and examples thereof include Al, Ti, Ta, Hf, Zr, Si, In, and Zn. The anodized metal body may contain one or more of these.
As the main component of the anodized metal body, Al or the like is particularly preferable.
In this specification, the “main component of the metal to be anodized” is defined as a component of 99% by mass or more.

With reference to FIGS. 2A to 2B, the manufacturing method and structure of the pore structure 21 will be described.
2A and 2B are schematic perspective views.

First, as shown in FIG. 2A, an anodized metal body M having an anodized metal such as Al as a main component is prepared.
The shape of the anodized metal body M is not limited, and examples thereof include a plate shape. Further, it may be used in a form with a support such as a layer in which the metal anodized M is formed on the support.

As shown in FIG. 2B, when a part of the anodized metal body M is anodized, a pore structure 21 made of a metal oxide is generated. For example, when the anodized metal body M has Al as a main component, a pore structure 21 having Al ₂ O ₃ as a main component is generated.
Usually, the pore structure 21 is a metal oxide layer, and the generated pore structure 21 is thin with respect to the remainder of the anodized metal body M. The structure 21 is greatly illustrated.

Anodizing is, for example, using an anodized metal body M as an anode, carbon or aluminum as a cathode (counter electrode), immersing them in an anodizing electrolyte, and applying a voltage between the anode and the cathode. Can be implemented.
The electrolytic solution is not limited, and an acidic electrolytic solution containing one or more acids such as sulfuric acid, phosphoric acid, chromic acid, oxalic acid, sulfamic acid, benzenesulfonic acid, and amidosulfonic acid is preferably used.

When the anodized metal body M is anodized, as shown in FIG. 2B, an oxidation reaction proceeds from the surface (upper surface in the figure) in a direction substantially perpendicular to this surface, and a metal oxide body is generated.
The metal oxide body generated by anodization has a structure in which a plurality of substantially regular hexagonal columnar bodies 21C are arranged adjacent to each other without a gap. Needle-like pores 21P extending in the depth direction from the surface are opened at substantially the center of each columnar body 21C. Between the bottom surface of the acicular pore 21P and the bottom surface of the metal oxide body, a barrier layer 21B without the acicular pore 21P is generated.
As shown in the figure, the needle-like pores 21P are opened in a direction substantially perpendicular to the surface of the anodized metal body M, but may be opened in a slightly oblique direction.
In the present embodiment, the remaining portion of the anodized metal body M remaining after the anodic oxidation becomes the lower electrode layer 10.

In the present embodiment, a plurality of needle-like conductors 22 are formed inside a plurality of needle-like pores 21P opened in a pore structure 21 made of a metal oxide body.

In the EL element 1 of the present embodiment, when a voltage is applied to the needle-like conductor layer 20, the needle-like conductor 22 has a high dielectric constant, so that the tip of the needle-like conductor 22 on the light emitter layer 30 side. The charge density becomes higher.
Hereinafter, unless otherwise specified, the tip of the needle-like conductor 22 means “tip of the needle-like conductor 22 on the light emitter layer 30 side”.
The closer to the electric charge, the higher the electric lines of force, and the density of the electric lines of force is proportional to the electric field strength. Therefore, the vicinity of the tip of the acicular conductor 22 has a high electric field strength. That is, electric field concentration occurs near the tip of the needle-like conductor 22.
The longer the needle-like conductor 22 is in the voltage application direction, the higher the charge density at the tip, and the electric field strength near the tip tends to increase. Further, the smaller the diameter of the needle-like conductor 22, the higher the charge density at the tip, and the electric field strength near the tip tends to increase.
From Non-Patent Document 1 listed in the section “Background Art”, it is considered that the concentrated electric field strength is expressed by the following equation.
(Concentrated electric field strength) = (coefficient) × (needle conductor length / needle conductor cross-sectional area) ² × (average applied electric field)

In the present embodiment, the cross-sectional areas of the acicular pores 21P and the acicular conductor 22 are approximately proportional to the square of the pore diameter. Further, since the luminance is proportional to the square of the concentrated electric field strength, it is proportional to the fourth power of the pore length and inversely proportional to the fourth power of the pore diameter. That is, as the pore length is longer and the pore diameter is smaller, the concentrated electric field strength tends to increase and the emission intensity tends to increase.
In addition, when the cross-sectional shape of the acicular pore 21P and the acicular conductor 22 deviates from a perfect circle, the diameter shall be defined by the diameter of a perfect circle which has an equivalent cross-sectional area.

The method for forming the plurality of needle-shaped conductors 22 inside the plurality of needle-shaped pores 21P is not particularly limited, and for example, electrolytic deposition such as electrolytic plating using the lower electrode layer 10 as an electrode is preferable.

The composition of the acicular conductor 22 is not particularly limited, and the higher the conductivity, the higher the concentrated electric field strength, which is preferable.
The acicular conductor 22 preferably contains at least one metal selected from the group consisting of Ag, Au, Cd, Co, Cu, Fe, Ni, Sn, and Zn.
In consideration of conductivity and ease of sealing, the acicular conductor 22 preferably contains Cu and / or Ni.
In consideration of suppression of diffusion to the light emitting layer 30, the acicular conductor 22 preferably contains Au.

As defined in the section “Means for Solving the Problems”, in this specification, “needle” refers to a shape having a length / diameter of 2 or more.
The length of the acicular conductor in the phosphor particles used in the conventional dispersion-type inorganic EL element is usually in the range of 1 to 20 μm, although it depends on the particle diameter, and the diameter of the acicular conductor is usually 0.00. 01 to 0.5 μm. The same length and diameter are preferable for the needle-like conductor 22 in the present embodiment.
Since the electric field concentration effect is enhanced, the length of the needle-like conductor 22 is preferably 1 μm or more, and particularly preferably 5 μm or more.
Since the electric field concentration effect is enhanced, the diameter of the needle-like conductor 22 is preferably 0.5 μm or less, more preferably 0.1 μm or less, and particularly preferably 0.05 μm or less.
Considering the ease of formation, the diameter of the needle-like conductor 22 is preferably 0.02 μm or more.
The length / diameter of the acicular conductor 22 is preferably 100 or more because the electric field concentration effect is enhanced.

In the present embodiment, the plurality of acicular conductors 22 are formed inside the plurality of acicular pores 21P.
Considering the preferable size of the acicular conductor 22, the length of the acicular pore 21P is preferably 1 μm or more, and particularly preferably 5 μm or more.
The diameter of the acicular pores 21P is preferably 0.5 μm or less, more preferably 0.1 μm or less, and particularly preferably 0.05 μm or less. The diameter of the acicular pores 21P is preferably 0.02 μm or more.
The length / diameter of the acicular pores 21P is preferably 100 or more.

In the drawing, the needle-shaped conductor 22 is completely filled in all the needle-shaped pores 21P, and the tip of the needle-shaped conductor 22 and the light emitting layer 30 are shown in close contact with each other. However, the filling rate of the acicular conductors 22 in the individual acicular pores 21P may not be 100%.
That is, the tip of the needle-like conductor 22 and the light emitting layer 30 do not need to be in close contact with each other. However, since the concentrated electric field strength is high, it is preferable that the tip of the needle-like conductor 22 and the light emitting layer 30 are closer. Considering this point, it is preferable that the filling rate of the acicular conductors 22 in each acicular pore 21P is higher.
In this specification, the filling rate of the acicular conductor 22 in each acicular pore 21P is defined by the length of the acicular conductor 22 / the length of the acicular pore 21P × 100 (%). The filling rate of the acicular conductor 22 in each acicular pore 21P is preferably 70 to 100%.

There may be variations in the filling rate of the needle-shaped conductors 22 inside the individual needle-shaped pores 21P. In this case, however, the separation distance between the needle-shaped pores 21P and the light emitter layer 30 varies, resulting in an electric field. The concentration effect will vary. Considering the in-plane uniformity of light emission, it is preferable that the variation in the filling rate is small.

The length of the needle-shaped pore 21P is determined in consideration of a preferable length of the needle-shaped conductor 22 and a filling rate of the needle-shaped conductor 22 inside the needle-shaped pore 21P.

The higher the number density of the needle-like conductors 22, the more light emitting portions due to the concentrated electric field increase, so that high light emission luminance can be obtained and the in-plane uniformity of the light emission luminance is also preferable. However, if the distance between the adjacent needle-shaped conductors 22 becomes too short, the lines of electric force concentrated on the respective needle-shaped conductors 22 become low in density, which may reduce the electric field strength. In order to suppress such a decrease in electric field strength, it is preferable that the distance between the needle-like conductors 22 adjacent to each other is 0.02 μm or more.
In the present embodiment, the number density of the acicular conductors 22 corresponds to the number density of the acicular pores 21P.
The number density of the acicular pores 21P and the acicular conductors 22 is preferably 1 piece / μm ² or more.
The number density of the acicular pores 21P and the acicular conductors 22 is preferably 400 pieces / μm ² or less.
The number density of the acicular pores 21P and the acicular conductors 22 is more preferably 10 to 300 / μm ² .

The electric field concentration becomes more effective as the direction in which the needle-like conductor 22 extends is closer to the voltage application direction. According to the anodic oxidation method, the pore structure 21 in which a plurality of needle-like pores 21P extending in a direction parallel to or close to the voltage application direction is regularly arrayed can be formed by a simple process. According to the anodizing method, it is easy to control the size (length and diameter) and number density of the needle-shaped pores 21P, and it is easy to increase the area. The anodizing method is a low cost method.

According to the anodic oxidation method, the remainder of the anodized metal body M remaining after the anodic oxidation can be made the lower electrode layer 10.
Therefore, the lower electrode layer 10 and the acicular conductor layer 20 can be integrally formed by the same process. In this method, since the lower electrode layer 10 and the acicular conductor layer 20 are generated from one anodized metal body M, their adhesion is high and preferable.
The composition of the lower electrode layer 10 is the same as that of the used anodized metal body M.

Since the process becomes simple, it is preferable that the remainder of the anodized metal body M remaining after the anodization is the conductor 10, but the entire anodized metal body M may be anodized.
Further, as shown in the EL element 3 in FIG. 4, at least a part of the anodized metal body M is anodized, and if there is, the remaining part of the anodized metal body M and the barrier layer 21B of the metal oxide body are removed. The plurality of needle-like pores 21P may be through holes. In this case, since the barrier layer 21B is removed, a higher electric field concentration effect is obtained, which is preferable.
For example, the remainder of the anodized metal body M and the barrier layer 21B can be physically removed by cutting or the like.
Further, the remainder of the anodized metal body M and the barrier layer 21B can be removed by immersing in an acidic liquid such as phosphoric acid.

When the remainder of the anodized metal body M is not left, it is necessary to provide the conductor 10 separately.
The conductor 10 may be a conductive substrate or a conductor film.
For example, a conductor film such as an Au film can be formed on the pore structure from which the barrier layer has been removed. In this case, if necessary, an insulating base material such as an alumina base material and a pore structure with a conductor film are bonded to each other through an adhesive component such as a silver paste and heat-treated to adhere them. Can do.
Thereafter, similarly to the present embodiment, a plurality of needle-shaped conductors 22 are formed inside the plurality of needle-shaped pores 21P, preferably by electrolytic deposition such as electrolytic plating using the conductor 10 as an electrode, The acicular conductor layer 20 can be manufactured.

In the present embodiment, the case where the pore structure 21 is made of an anodized metal body has been described. However, the present invention is not limited to such an embodiment, and the pore structure 21 opens on the surface of the light emitter layer 30 side. What is necessary is just to have the some acicular pore 21P extended in the crossing direction with respect to the surface at the side of the light-emitting body layer 30. FIG.
As the pore structure 21 other than the anodized metal body, a pore structure such as mesoporous silica described in Non-Patent Document 2, etc., a pore structure obtained by utilizing the self-organization of a polymer, And a pore structure obtained by utilizing etching using a lithography technique.

After obtaining the pore structure 21 having the plurality of needle-shaped pores 21P, instead of forming the plurality of needle-shaped conductors 22 inside the plurality of needle-shaped pores 21P, the plurality of needle-shaped conductors 22 are After the provision, an insulator may be provided so as to embed the plurality of needle-like conductors 22.
In this case, examples of the acicular conductor 22 include those obtained by growing acicular crystals of metal such as Ag and Cu or carbon nanotubes from the surface of the lower electrode layer 10. Examples of the insulator that embeds the needle-like conductor 22 include a ceramic body and a polymer. The insulator embedding the acicular conductor 22 can be formed by a known method such as a wet coating method or a vacuum deposition method.

The phosphor layer 30 is a layer that emits light when excited in an electric field. The thickness of the luminescent layer 30 is preferably thinner from the viewpoint of concentrating the electric field near the tip of the acicular conductor 22, and specifically, it is preferably in the range of 0.05 to 2 μm.
The material of the light emitter layer 30 is not particularly limited, and a known light emitter material for an EL element can be used.
The EL element 1 may be an array in which a plurality of types of light emitter layers 30 that emit light of different wavelengths in a plan view.
As a material of the light emitting layer 30, ZnS: Mn, ZnS: Tb, F, ZnS: Pr, F, ZnS: Ag, Cl, ZnS: Cu, Cl, Y ₂ O ₃ : Eu, ZnSiO ₄ : Eu, SrS : Ce, BaAl ₂ S ₄ : Eu, BaMgAl ₁₀ O ₁₇ : Inorganic compounds such as Eu, MgWO ₄ , CaWO ₄ , RbVO ₃ , and CsVO ₃ , or organic compounds such as Alq3. These can use 1 type or multiple types.

As shown in EL elements 2 and 3 of the design modification example shown in FIGS. 3 and 4, an insulator layer (lower insulator layer) 50 is provided between the needle-like conductor layer 20 and the light emitter layer 30. Also good. The insulator layer 50 may have a single layer structure or a laminated structure.
The insulator layer 50 functions as a barrier layer, and it is possible to prevent the components of the needle-like conductor 22 formed inside the needle-like pores 21P from diffusing into the light-emitting body layer 30 and inactivating light emission.
Examples of the material for the insulator layer 50 include oxides such as SiO ₂ , Ta ₂ O ₅ , TiO ₂ , BaTiO ₃ , and Al ₂ O ₃ , nitrides such as Si ₃ N ₄ , AlN, and TiN, SiON, and AlON. Examples thereof include oxynitrides and combinations thereof.

It has been described that the closer the tip of the acicular conductor 22 and the light emitting layer 30 are, the higher the electric field concentration effect becomes.
Regardless of the presence or absence of the insulator layer 50, the distance between the acicular conductor 22 and the light emitter layer 30 is preferably 1 μm or less.
The thickness of the insulator layer 50 is preferably thinner from the viewpoint of concentrating the electric field on the acicular conductor 22, and specifically, it is preferably 0.2 μm or less.
If the thickness of the insulator layer 50 is too small, the function as a barrier layer cannot be obtained effectively.
The film thickness of the insulator layer 50 is preferably 0.05 μm or more.

As described above, the insulator layer 50 may be provided between the acicular conductor layer 20 and the light emitter layer 30, but the conductor layer between the acicular conductor layer 20 and the light emitter layer 30 is Not provided. When a conductor layer is provided between the acicular conductor layer 20 and the light emitting layer 30, the conductor layer substantially functions as a lower electrode layer, and an electric field concentration effect by the plurality of acicular conductors 22 is obtained. Disappear.

As shown in the EL elements 2 and 3 in the design modification examples shown in FIGS. 3 and 4, an insulator layer (upper insulator layer) 60 may be provided between the light emitter layer 30 and the upper electrode layer 40. . The insulator layer 60 may have a single layer structure or a laminated structure.
The insulator layer 60 functions as a cap layer, suppresses desorption of materials on the surface of the light emitter layer 30, makes the composition of the light emitter layer 30 uniform, and improves the light emission characteristics.
Examples of the material of the insulator layer 60 include oxides such as SiO ₂ , Ta ₂ O ₅ , TiO ₂ , BaTiO ₃ , and Al ₂ O ₃ , nitrides such as Si ₃ N ₄ , AlN, and TiN, SiON, and Examples thereof include oxynitrides such as AlON and combinations thereof.
The thickness of the insulator layer 60 is preferably thinner from the viewpoint of concentrating the electric field on the acicular conductor 22, and specifically, it is preferably 0.2 μm or less.
If the thickness of the insulator layer 60 is too small, the function as a cap layer cannot be obtained effectively.
The thickness of the insulator layer 60 is preferably 0.05 μm or more.

3 and 4 show an embodiment in which both the insulator layer 50 functioning as a barrier layer and the insulator layer 60 functioning as a cap layer are provided, but only one of these insulator layers is shown. It is good also as a structure which provides.

The material of the upper electrode layer 40 may be any conductive material having translucency, such as ITO (indium tin oxide), FTO (fluorine-added tin oxide), SnO ₂ , PEDOT (polyethylenedioxythiophene), and CNT ( Carbon nanotubes) are preferably used.

The film formation method of the light emitting layer 30, the upper electrode layer 40, and the insulator layers 50 and 60 is not particularly limited, and a known method can be adopted.
As a film forming method, a sputtering method or a physical vapor deposition method under vacuum such as an electron beam evaporation method, and a solution or dispersion containing a component or precursor of a layer to be formed into a film, a spin coating method, Examples thereof include a liquid phase method such as a coating method applied by a dip coating method, a bar coating method, a spray coating method, or the like.
The light emitter layer 30 and the insulator layers 50 and 60 may include a non-conductive polymer as a binder.

The EL element 1 of the present embodiment includes a plurality of needle-like conductors extending in a direction intersecting the surface 30S of the light emitter layer 30 on the lower electrode layer 10 side between the lower electrode layer 10 and the light emitter layer 30. 22 and an acicular conductor layer 20 including an insulator (in this embodiment, a pore structure 21) that insulates the acicular conductors 22 from each other.

As described in the section “Problems to be Solved by the Invention”, the conventional thin-film inorganic EL elements described in Patent Document 1 and the like have attempted to improve the light emission characteristics such as light emission luminance and light emission efficiency. However, in order to obtain sufficient light emission luminance, a high electric field is required, and the light emission efficiency tends to decrease.
In the configuration of the present embodiment, a concentrated electric field is generated in the vicinity of the tip of the needle-like conductor 22, so that high emission luminance can be obtained even with a relatively low electric field.

As described in the section “Problems to be Solved by the Invention”, the conventional dispersion-type inorganic EL element described in Patent Document 2 and the like generates a high electric field in the vicinity of the tip of the acicular conductor, High luminance can be obtained with a relatively low electric field. However, the electric power consumed by the binder contained in the light emitting layer is large, and the light emission efficiency tends to decrease. In addition, since the acicular conductors in the phosphor particles are deposited in multiple directions (random directions) in the crystal plane, the proportion of acicular conductors oriented perpendicular to the electrode surface is small and the electric field is concentrated. Hard to do.
In the present embodiment, since no binder is required for the needle-like conductor layer 20, the light emission efficiency is not reduced by the power consumed by the binder. In the present embodiment, the needle-like conductor 22 can be easily oriented in the voltage application direction or a direction close thereto, and electric field concentration can be effectively caused.

According to this embodiment, it is possible to provide the EL element 1 that can improve both the light emission luminance and the light emission efficiency without applying a high electric field by combining the above-described effects.
The present invention is applicable to both inorganic EL elements and organic EL elements, and is preferably applicable to inorganic EL elements.

Hereinafter, the present invention will be further described with reference to examples and comparative examples, but the present invention is not limited thereto.

<Example 1>
An anodizing process was performed on a 100 × 100 mm aluminum plate having a thickness of 3 mm under the following conditions to form an alumina layer having a plurality of acicular pores.
-Counter electrode (cathode): Aluminum-Electrolyte: 0.3 M sulfuric acid-Bath temperature: 15-19 ° C
・ Voltage: DC 40V
・ Time: 100 minutes

The surface and the cross section of the obtained alumina layer were observed using a scanning electron microscope (SEM, “S-4800” manufactured by Hitachi, Ltd.). In the surface SEM image (80,000 times), the average pore diameter was determined from the pore area of 100 pores. Further, the pore density was determined from the number of pores in the same surface SEM image. In the cross-sectional SEM image (10,000 times), the average pore length was determined from the pore length of 100 pores.
The obtained alumina layer had a plurality of needle-like pores opened almost regularly, and had an average pore diameter of 0.02 μm, an average pore length of 8 μm, and an average pore density of 300 / μm ² .

Next, Ni was electrolytically deposited inside the plurality of needle-shaped pores of the alumina layer under the following conditions to form a plurality of needle-shaped conductors.
Electrolytic bath: 0.3M nickel sulfate hexahydrate, 0.1M ammonium sulfate, and 0.5M boric acid mixed solution Bath temperature: 22-25 ° C
・ PH: 4.0 to 4.5
・ Voltage: AC 10V (50Hz)
・ Processing time: 30 minutes

When SEM cross-section observation of the obtained acicular conductor layer was performed, the filling rate of the acicular conductor inside the acicular pores was 70 to 100%.

Next, a phosphor layer was formed by sputtering using a sintered body obtained by sintering ZnS powder added with 0.5 mass% Mn by hot pressing at 900 ° C. and 50 MPa for 1 hour. The degree of vacuum at the time of vapor deposition was set to 5 × 10 ⁻⁴ Pa or less, the substrate temperature was set to 200 ° C., and the vapor deposition rate was set to 20 nm / min. The obtained phosphor layer was heat-treated at 500 ° C. for 1 hour in a nitrogen atmosphere to activate Mn at the emission center.

Next, ITO was deposited to a thickness of 100 nm on the phosphor layer by sputtering to form an upper electrode layer.
As described above, an inorganic EL element was obtained.

<Example 2>
Except that a silicon oxynitride (SiON) layer functioning as a barrier layer was formed by sputtering at a thickness of 100 nm between the acicular conductor layer and the ZnS: Mn phosphor layer, the same conditions as in Example 1 were used. An inorganic EL element was produced.

<Example 3>
A silicon oxynitride (SiON) layer functioning as a barrier layer between the acicular conductor layer and the ZnS: Mn phosphor layer is formed by sputtering at a thickness of 100 nm, and between the ZnS: Mn phosphor layer and the upper electrode layer. A double-insulated inorganic EL element was produced under the same conditions as in Example 1 except that a silicon oxynitride (SiON) layer functioning as a cap layer was formed by sputtering to a thickness of 100 nm.

<Example 4>
After the formation of the acicular conductor layer, surface polishing was performed with a polishing machine (Diawrap ML-150P manufactured by Marto) to remove the non-sealed portion remaining on the upper portion of the acicular pores during the electrolytic deposition of Ni Except for this, an inorganic EL element was produced under the same conditions as in Example 3.
The surface polishing of the acicular conductor layer was performed in two steps. Using a water-resistant abrasive paper having a large particle size (manufactured by Sankyo Rikagaku Co., Ltd., average particle size of 7.9 μm, No. 2000) and a liquid abrasive (manufactured by Marto Co., Ltd., average particle size of 0.5 μm diamond slurry) Conducted for a minute. Thereafter, a second polishing was performed for 30 minutes using a polishing cloth having a small particle size (manufactured by Marto, hard polishing cloth MM414) and a liquid abrasive (manufactured by Fujimi, colloidal silica having an average particle size of 70 nm). After these two times of surface polishing, in order to remove the abrasive grains remaining on the surface, the surface was washed with a mixed acid of 0.6% by mass phosphoric acid and 0.18% by mass chromic acid.
In this example, the filling rate of the acicular conductors in all the acicular pores was 100%.

<Example 5>
0.4 g of cyanoethylated polyvinyl alcohol (manufactured by Shin-Etsu Chemical Co., Ltd.) as a binder is dispersed in 15 ml of N, N-dimethylformamide as a solvent, and 1 g of ZnS: Mn particles having a particle diameter D50 = 1.0 μm is ultrasonically dispersed. A dispersion was prepared. Example 1 except that the obtained dispersion was applied onto the acicular conductor layer by spin coating, and the solvent was dried and removed at 90 ° C. for 1 hour to form a 1.5 μm-thick phosphor layer. An inorganic EL element was manufactured under the same conditions as those described above.

<Example 6>
Except that the treatment time for anodization was increased to 8 hours, the conditions were the same as in Example 1, and a part of the aluminum plate was anodized to form an alumina layer having a plurality of needle-shaped pores. Next, the remaining part of the aluminum substrate and the alumina layer having a plurality of acicular pores are immersed in phosphoric acid to dissolve the remaining part of the aluminum substrate, the barrier layer of the alumina layer and the vicinity thereof, and penetrate the plurality of acicular pores. It was a hole.
The obtained alumina layer was subjected to SEM observation and pore evaluation in the same manner as in Example 1. As a result, a plurality of needle-like pores were opened almost regularly, with an average pore diameter of 0.03 μm and an average pore length. It was 40 μm and the average pore density was 300 / μm ² .

On the side of the alumina layer from which the barrier layer was removed, Au was formed by sputtering to a thickness of 100 nm.
Separately, a commercially available alumina substrate (A476T manufactured by Kyocera) was prepared, and a silver paste was screen-printed thereon, and the above-mentioned alumina layer with the Au film was placed thereon with the Au film side down. Then, it heat-processed in air | atmosphere at 500 degreeC for 1 hour, and the alumina substrate and the alumina layer with Au film | membrane were adhere | attached.

Next, Ni was electrolytically deposited inside the plurality of needle-shaped pores of the alumina layer under the following conditions to form a plurality of needle-shaped conductors.
Electrolytic bath: 1.4M Ni sulfamate and 0.7M boric acid mixture Bath temperature: 22-25 ° C
・ PH: 4.0 to 4.5
・ Voltage: DC 2V
・ Processing time: 30 minutes

When the SEM cross-section observation of the obtained acicular conductor layer was carried out, the filling rate of the acicular conductor inside the acicular pores was 80 to 100%.
Thereafter, similarly to Example 3, a barrier layer, a light emitting layer, a cap layer, and an upper electrode layer were formed.
As described above, an inorganic EL element was obtained.

<Comparative Example 1>
Example 1 except that an ITO film was sputtered to a thickness of 300 nm as a lower electrode layer on an alkali-free glass substrate, and a phosphor layer was formed on the lower electrode layer without providing a needle-like conductor layer. Under the same conditions, a conventional thin-film inorganic EL element having no electric field concentration was produced.

<Comparative example 2>
Example 3 except that an ITO film as a lower electrode layer was formed by sputtering on an alkali-free glass substrate with a thickness of 300 nm, and a phosphor layer was formed on the lower electrode layer without providing a needle-like conductor layer. Under the same conditions, a conventional thin-film inorganic EL element having no electric field concentration was produced.

<Comparative Example 3>
Example 5 is the same as Example 5 except that an ITO film as a lower electrode layer was sputtered to a thickness of 300 nm on an alkali-free glass substrate, and a phosphor layer was formed on the lower electrode layer without providing a needle-like conductor layer. Under the same conditions, a conventional thin-film inorganic EL element having no electric field concentration was produced.

<Evaluation 1>
About the EL element obtained in each example, the alternating voltage of frequency 1kHz was applied with alternating current power supply, and the light-emitting luminance and luminous efficiency in voltage 200V were evaluated. The light emission luminance was measured with a color luminance meter (manufactured by Topcon Corporation, BM7).
Further, the voltage at which the light emission luminance of 1 cd / m ² was obtained was obtained as the light emission start voltage.
Table 1 shows the laminated structure and evaluation results of each example.

As shown in Table 1, in Examples 1 to 6 in which the needle-shaped conductor layer was provided, both the luminance and the luminous efficiency were improved compared to Comparative Examples 1 to 3 in which the needle-shaped conductor layer was not provided. Thus obtained inorganic EL device was obtained.
In particular, in Example 4 in which the surface polishing of the needle-shaped conductor layer and Example 6 in which the barrier layer of the alumina layer was removed, high emission luminance and luminous efficiency were obtained.
When Examples and Comparative Examples having the same laminated configuration except for the presence or absence of the acicular conductor layer are compared (specifically, Example 1 and Comparative Example 1, Example 3 and Comparative Example 2, Example 5) And Comparative Example 3), the emission start voltage was at the same level.
From the above results, it was shown that by providing the acicular conductor layer, it is possible to provide an inorganic EL element capable of improving both the light emission luminance and the light emission efficiency without applying a high electric field.

<Evaluation 2>
About the inorganic EL element obtained in Example 1 and Comparative Example 1, using an optical microscope (manufactured by Nakaden Co., Ltd., digital microscope MX-1200II), the state of light emission when 200 V AC voltage with a frequency of 1 kHz was applied. Observed.
As shown in the micrograph in FIG. 5, in the inorganic EL element of Example 1, countless point-like light emission due to electric field concentration in the vicinity of the tip of the needle-like conductor was observed. On the other hand, as shown in the micrograph in FIG. 6, the inorganic EL element of Comparative Example 1 exhibited uniform planar light emission as a whole.

This application claims priority based on Japanese Patent Application No. 2012-141160 filed on June 22, 2012 and Japanese Patent Application No. 2012-249292 filed on November 13, 2012. , The entire disclosure of which is incorporated herein.

The EL element of the present invention can be used for display devices, lighting devices, and the like.

1 to 3 EL element 10 Lower electrode layer (first electrode layer)
20 Needle-like conductor layer 21 Porous structure 21B Barrier layer 21C Columnar body 21P Needle-like pore 22 Needle-like conductor 30 Light emitter layer 30S Surface 40 of the light emitter layer on the lower electrode layer side Upper electrode layer (second Electrode layer)
50, 60 Insulator layer M Metal object to be anodized

Claims (14)

1. An electroluminescent device comprising a first electrode layer, a light emitter layer, and a second electrode layer having translucency in order,
   Between the first electrode layer and the phosphor layer,
   Needle-like conductivity including a plurality of needle-like conductors extending in a crossing direction with respect to the surface on the first electrode layer side of the phosphor layer, and an insulator that insulates between the plurality of needle-like conductors. An electroluminescent device comprising a body layer.
2. The electroluminescent device according to claim 1, wherein a conductor layer is not provided between the needle-like conductor layer and the light emitting layer.
3. The insulator of the acicular conductor layer has a pore structure having a plurality of acicular pores that open in the surface on the light emitter layer side and extend in a direction intersecting the surface on the light emitter layer side The electroluminescent element according to claim 1, wherein the plurality of needle-like conductors are formed inside the plurality of needle-like pores of the pore structure.
4. The electroluminescent device according to claim 3, wherein the pore structure is a metal oxide body obtained by anodizing at least a part of an anodized metal body.
5. The pore structure is a metal oxide body obtained by anodizing a part of the anodized metal body,
   The electroluminescent element according to claim 4, wherein the first electrode layer is a remaining part of the metal to be anodized remaining after anodization.
6. The pore structure is obtained by removing a barrier layer of a metal oxide body obtained by anodizing at least a part of the anodized metal body, and forming the plurality of needle-like pores as through holes. Item 5. The electroluminescent device according to Item 4.
7. The acicular conductor includes at least one metal selected from the group consisting of Ag, Au, Cd, Co, Cu, Fe, Ni, Sn, and Zn. Electroluminescence element.
8. The electroluminescent device according to any one of claims 1 to 7, wherein the needle-like conductor has a length of 1 µm or more.
9. The electroluminescent device according to any one of claims 1 to 8, wherein the needle-like conductor has a diameter of 0.5 µm or less.
10. 10. The electroluminescent device according to claim 1, wherein the length / diameter of the acicular conductor is 100 or more.
11. The electroluminescent device according to any one of claims 1 to 10, wherein the number density of the needle-like conductors in the needle-like conductor layer is 1 piece / µm ² or more.
12. 12. The electroluminescent device according to claim 1, further comprising an insulator layer between the needle-like conductor layer and the light emitter layer.
13. The electroluminescent device according to any one of claims 1 to 12, wherein a distance between the acicular conductor and the light emitting layer is 1 µm or less.
14. The electroluminescent device according to any one of claims 1 to 13, further comprising an insulator layer between the light emitter layer and the second electrode layer.

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