WO2014076939A1 - Electroluminescent element and method for producing same - Google Patents

Abstract

Provided is an EL element by which it is possible for both emission luminance and emission efficiency to be improved, without the need to apply a high electrical field. The EL element (1) is provided in succession with a first electrode layer (10), a light emission layer (30), and a second electrode layer (40) having translucence. Between the first electrode layer (10) and the light emission layer (30), the EL element (1) is provided with an acicular conductor layer (20) including a plurality of acicular conductors (22) extending in directions that intersect the surface (30S) at the first electrode layer (10) side of the light emission layer (30), and an insulator for insulating the plurality of acicular conductors (22) from one another. The EL element (1), at the element surface on the second electrode layer (40) side thereof, has average roughness Ra of 100 nm or less.

Description

Electroluminescent device and method for manufacturing the same

The present invention relates to an electroluminescent element and a method for manufacturing the same.

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, a dispersion-type inorganic EL element has 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 that sandwich the phosphor layer. It is an element provided with a board (refer claim 7 of patent document 2). Usually, the dispersion-type inorganic EL device 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 in order to obtain a high light emission luminance, and there is a tendency for the light emission efficiency to decrease due to the large amount of 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. In addition, since acicular conductors such as Cu 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, 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, and a method for manufacturing the same. It is.

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,
further,
Between the first electrode layer and the phosphor layer,
An insulator composed of a pore structure having a plurality of needle-like pores that are open in the surface on the light emitter layer side and extend in a crossing direction with respect to the surface on the light emitter layer side; A needle-like conductor layer including a plurality of needle-like conductors formed inside the hole,
It is an electroluminescent element whose arithmetic mean roughness Ra of the surface at the side of the said light-emitting body layer is 100 nm or less.

The manufacturing method of the electroluminescence (EL) element of the present invention is as follows:
A first electrode layer, a light emitter layer, and a second electrode layer having translucency are sequentially provided,
further,
Between the first electrode layer and the phosphor layer,
An insulator composed of a pore structure having a plurality of needle-like pores that are open in the surface on the light emitter layer side and extend in a crossing direction with respect to the surface on the light emitter layer side; A method of manufacturing an electroluminescent element comprising a needle-shaped conductor layer including a plurality of needle-shaped conductors formed inside a hole,
Preparing the insulator comprising a pore structure having the plurality of acicular pores (A);
Forming the plurality of needle-shaped conductors inside the plurality of needle-shaped pores of the insulator to obtain the needle-shaped conductor layer (B);
And (C) reducing the arithmetic average roughness Ra of the surface of the acicular conductor layer.

The manufacturing method of the electroluminescence (EL) element of the present invention is as follows:
After step (C)
A step (D) of forming an insulator layer serving as a barrier layer for preventing the acicular conductor component from diffusing into the light emitter layer;
A step (E) of performing a heat treatment at a temperature equal to or higher than a maximum temperature of the manufacturing process of the electroluminescent element after the step (D);
It is preferable to have a step (F) of reducing the arithmetic average roughness Ra of the surface of the insulator layer after the step (E).

In this specification, “needle” refers to a shape having a length / diameter of 2 or more.
In this specification, “the arithmetic average roughness Ra of the surface” is measured by a method based on JIS B 0601 (2001).

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

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. The left figure shows the EL element when the surface polishing of the acicular conductor layer is not performed, and the right figure is a schematic cross-sectional view showing the state of the EL element when the surface polishing of the acicular conductor layer is performed. It is. FIG. 6 is an explanatory diagram (schematic cross-sectional view) for explaining the effect of performing steps (D) to (F). FIG. 6 is an explanatory diagram (schematic cross-sectional view) for explaining the effect of performing steps (D) to (F). It is a figure which shows the example of a design change of the EL element of FIG. 2 is an optical microscope image of a needle-shaped conductor layer in Test Example 1 and Comparative Example 1. 2 is an optical microscope image showing a state of light emission of inorganic EL elements obtained in Test Example 1 and Comparative Example 1. FIG. 2 is a cross-sectional TEM image of an inorganic EL element obtained in Test Example 1. 3 is a surface SEM image (left figure) of the inorganic EL element obtained in Test Example 1 and a graph (right figure) showing the surface level difference measurement results. It is the graph (right figure) which shows the surface SEM image (left figure) and surface level | step difference measurement result of the inorganic EL element obtained in Test Example 4. It is an example of the optical microscope image of a commercially available Al plate. It is a graph which shows the example of a measurement of Ra of the vertical direction and Ra of a horizontal direction of a to-be-anodized metal body.

"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.
FIG. 5 is a diagram illustrating a design change example.
1 and 5, the same constituent elements 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. .

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 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 (%). Shall.
The filling rate of the acicular conductor 22 inside each acicular pore 21P is preferably 70 to 100%.

There may be some variation in the filling rate of the acicular conductors 22 inside each acicular pore 21P, but in this case, the separation distance between the acicular pores 21P and the phosphor layer 30 varies, There will be variations in the electric field concentration effect. 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 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 tris (8-quinolinolato) aluminum (Alq3) Can be mentioned. These can use 1 type or multiple types.

Although not necessarily essential, it is preferable to provide an insulator layer (lower insulator layer) 50 between the needle-like conductor layer 20 and the light emitter layer 30. 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, it is preferable to provide the insulator layer 50 between the needle-like conductor layer 20 and the light emitter layer 30, but the conductor layer is provided between the needle-like conductor layer 20 and the light emitter layer 30. 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.

Although not necessarily essential, it is preferable to provide an insulator layer (upper insulator layer) 60 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.

In the illustrated example, both the insulator layer 50 functioning as a barrier layer and the insulator layer 60 functioning as a cap layer are provided. However, only one of these insulator layers may be provided.

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.

When the surface roughness of the element is large, the in-plane electric field stimulation is not uniform, and the light emission characteristics such as in-plane uniformity of light emission, light emission luminance, and light emission efficiency tend to decrease. It is preferable that the surface roughness of the element is smaller because light emission characteristics such as in-plane uniformity of light emission, light emission luminance, and light emission efficiency are improved.
In this specification, the “surface roughness of the device” is defined by the arithmetic average roughness Ra of the device surface on the upper electrode layer 40 side.
By devising the manufacturing method, the arithmetic average roughness Ra of the element surface can be reduced.
The EL element 1 of the present embodiment is manufactured by a manufacturing method described later, and the arithmetic average roughness Ra of the element surface on the upper electrode layer 40 side is 100 nm or less, 70 nm or less, or 10 nm or less.
In addition, according to the manufacturing method described later, it is possible to reduce variation in the filling rate of the plurality of needle-shaped conductors 22 inside the plurality of needle-shaped pores 21P.
With these functions and effects, light emission characteristics such as in-plane uniformity of light emission, light emission luminance, and light emission efficiency can be enhanced.

According to the present 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 due to the combined effects of the above.

"Manufacturing method of EL element"
With reference to drawings, the manufacturing method of EL element 1 of one embodiment concerning the present invention is explained.
2A to 2B are schematic perspective views showing the manufacturing process of the pore structure.
The left figure of FIG. 3 shows the EL element (comparative example) when the surface roughness of the acicular conductor layer is not reduced, and the right figure of FIG. 3 reduces the surface roughness of the acicular conductor layer. It is a schematic cross section which shows the mode of the EL element (EL element of this embodiment) at the time of doing.
4A and 4B are explanatory views (schematic cross-sectional views) for explaining the effect of performing the steps (D) to (F).

Hereinafter, a method for manufacturing the EL element of this embodiment will be described.

(Process (A))
First, an insulator composed of a pore structure 21 having a plurality of needle-like pores 21P is prepared.
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.
As described above, 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 remainder 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.
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.

The electric field concentration becomes more effective as the extending direction of the needle-like conductor 22 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 remaining portion of the metal body M to be anodized remaining after the anodic oxidation is the lower electrode layer 10, but all of the metal body M to be anodized may be anodized.
Further, as shown in the EL element 2 in FIG. 5, at least 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. A plurality of needle-like pores 21P may be used as 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 metal to be anodized M is not left, it is necessary to provide the lower electrode layer 10 separately.
The lower electrode layer 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.

In the step (A), it is preferable to prepare a metal oxide body obtained by anodizing at least a part of an anodized metal body having an arithmetic average roughness Ra of 200 nm or less as the insulator. .
In the phosphor layer 30 formed by vapor deposition or the like, the emission center is activated by heat treatment, and the higher the temperature, the more the emission center is activated and the emission performance tends to be improved. Due to the difference in thermal expansion coefficient between the lower electrode layer 10 and the acicular conductor layer 20 during the heat treatment for activating the luminescent center of the luminescent layer 30, stress is generated between them.
In general, a commercially available anodized metal body M such as Al is a rolled body, and has a large number of stripes (rolling stripes) extending in the rolling direction (see FIG. 10). In the anodized metal body M, stress tends to concentrate in the crossing direction with respect to the rolling direction, so that there is a possibility that cracks may occur in the needle-like conductor layer 20.
The inventor suppresses stress applied in a specific direction in a metal oxide body obtained by anodization by using an anodized metal body M having an arithmetic average roughness Ra of 200 nm or less on the surface before anodization. And found that the generation of cracks can be suppressed. As a result, it has been found that the device withstand voltage can be improved in the acicular conductor layer 20 during the heat treatment when activating the luminescent center of the luminescent layer 30.

When the anodized metal body M is a rolled body, Ra in the direction parallel to the rolling direction (longitudinal direction) and the direction perpendicular to the rolling direction (transverse direction) is 200 nm or less. .
Usually, since Ra in the horizontal direction> Ra in the vertical direction, the Ra in the horizontal direction may be set to 200 nm or less.

In a commercially available anodized metal body M such as Al, the Ra in both the direction parallel to the rolling direction (longitudinal direction) and the direction perpendicular to the rolling direction (lateral direction) is usually more than 200 nm. Therefore, it is preferable to perform anodic oxidation after polishing the surface of the commercially available anodized metal body M and setting the Ra in either the vertical direction or the horizontal direction to 200 nm or less.
Surface polishing can be performed by a known method.
For example, chemical polishing in which the anodized metal body M such as Al is immersed in an acid solution containing phosphoric acid, nitric acid, or a combination thereof is preferable.

An example of an optical micrograph of a commercially available Al plate is shown in FIG. This figure shows a number of rolling rebars and stress directions.
The direction of stress in FIG. 10 is schematic, and the actual direction of stress is a crossing direction such as a direction perpendicular to the direction of rolling bars.

FIG. 11 shows an example of measurement of Ra in the vertical direction and Ra in the horizontal direction for a commercially available Al plate and its surface polished product.
In the figure, the data on the upper right with the largest Ra is data without surface polishing, and the other two data are data with surface polishing.

The present inventor has also found that the light emission luminance of the EL element 1 is improved by using the anodized metal body M having an arithmetic average roughness Ra of 200 nm or less before anodic oxidation.
This is considered to be because the surface roughness of the acicular conductor layer 20 is reduced, and the in-plane electric field stimulation becomes uniform.

In step (A), as the insulator, a metal oxide body obtained by anodizing at least a part of an anodized metal body having a purity of the main component metal element of 99.9% by mass (3N) or more Is preferably prepared. The purity of the main component metal element of the metal to be anodized is particularly preferably 99.99% by mass (4N) or more.

Hereinafter, unless otherwise specified, in this specification, “%” indicates “mass%”.

When the purity of the metal to be anodized M is low, there is a possibility that defects such as unnecessary voids different from the needle-shaped pores may occur in the metal oxide obtained by anodization due to impurities. Further, the acicular pores may grow in an oblique direction shifted from the vertical direction with respect to the surface of the original anodized metal body M due to impurities. These defects hinder electric field concentration, leading to a decrease in light emission luminance and light emission efficiency.
Hereinafter, unless otherwise specified, in this specification, “void” refers to an unnecessary void different from the acicular pores.
By setting the purity of the main component metal element of the anodized metal body M to 99.9% (3N) or more, preferably 99.99% (4N) or more, the metal oxide body obtained by anodization has voids and the like. The occurrence of defects is suppressed, and the acicular pores 21P can be grown in a direction substantially perpendicular to the surface of the original anodized metal body M. As a result, light emission luminance and light emission efficiency can be increased.

(Process (B))
Next, a plurality of needle-like conductors 22 are formed inside the plurality of needle-like pores 21 </ b> P of the pore structure 21 to obtain the needle-like conductor layer 20.
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.

(Process (C))
Next, the arithmetic average roughness Ra of the surface of the acicular conductor layer 20 is reduced.
The method for reducing the surface roughness of the acicular conductor layer 20 is not particularly limited, and surface polishing or the like is preferable.
The arithmetic average roughness Ra of the surface of the acicular conductor layer 20 obtained after the formation of the plural acicular conductors 22 is usually more than 10 nm. It is preferable that the arithmetic average roughness Ra of the surface of the acicular conductor layer 20 is 10 nm or less by surface polishing or the like.
When the surface roughness of the acicular conductor layer 20 is reduced by surface polishing or the like, when there is variation in the filling rate of the plural acicular conductors 22 inside the plural acicular pores 21P, a plurality of acicular shapes The filling rate of the plurality of needle-like conductors 22 inside the pores 21P can be increased as a whole, and the variation in the filling rate of the plurality of needle-like conductors 22 inside the plurality of needle-like pores 21P can be reduced. . Even when there is a variation in the filling rate of the plurality of needle-like conductors 22 inside the plurality of needle-like pores 21P, the filling rate of the plurality of needle-like conductors 22 inside the plurality of needle-like pores 21P is set to 100. % Or close to it.
At this time, the surface roughness is reduced, and preferably the surface roughness of the element finally obtained can be reduced by setting the arithmetic average roughness Ra of the surface to 10 nm or less. For example, the arithmetic average roughness Ra of the surface of the finally obtained device can be 100 nm or less, or 70 nm or less.
Combined with the above effects, the EL element 1 with improved light emission characteristics such as in-plane uniformity of light emission, light emission luminance, and light emission efficiency can be provided.

The left figure of FIG. 3 shows the EL element when the surface roughness of the acicular conductor layer 20 is not reduced, and the right figure of FIG. 3 shows the case where the surface roughness of the acicular conductor layer 20 is reduced. It is a schematic cross section which shows the mode of this EL element.

(Process (D) to (F))
Next, preferably, an insulator layer 50 serving as a barrier layer for preventing the components of the acicular conductor 22 from diffusing into the light emitter layer 30 is formed (step (D)).
Next, preferably, heat treatment is performed at a temperature equal to or higher than the maximum temperature of the EL element manufacturing process after step (D) (step (E)).
Next, preferably, the arithmetic average roughness Ra of the surface of the insulator layer 50 after the step (E) is reduced (step (F)).

As a result of investigation by the present inventor, even if the surface roughness of the acicular conductor layer 20 is reduced in the step (C), some acicular pores 21P of the acicular conductor layer 20 in the subsequent high temperature process. It has been found that the needle-like conductor 22 may protrude from the needle and a convex portion may be formed on the surface of the needle-like conductor layer 20. For example, it has been found that the above phenomenon occurs in a high-temperature process such as heat treatment for activating the luminescent center element of the phosphor layer 30.
The inventor
When a convex portion is formed on the surface of the acicular conductor layer 20,
As shown in FIG. 4A,
The surface of each upper layer of the acicular conductor layer 20 has a circular arc-shaped convex portion in cross-sectional view derived from the convex portion of the acicular conductor layer 20 described above,
The surface of the convex portion of each upper layer has an arc shape that spreads at the same angle in a sectional view,
And as it goes to the upper layer, the radius of the circular arc in cross section of the surface of the convex portion increases, so that the width and height of the convex portion increase and the surface unevenness increases as it goes to the upper layer (test example described later) 1, see FIG. 8A).

After forming the insulator layer 50 to be a barrier layer, before the light emitting layer 30 is formed, the needle (30) is formed by performing a heat treatment (E) at a temperature equal to or higher than the maximum temperature of the subsequent EL element manufacturing process. Protrusion of the needle-like conductor 22 from a part of the needle-like pores 21P of the needle-like conductor layer 20 can be forced.
Thereafter, when the step (F) of reducing the arithmetic average roughness Ra of the surface of the insulator layer 50 after the step (E) is performed, as shown in FIG. 4B, in the subsequent high-temperature process, the acicular conductor layer is again formed. The protrusion of the needle-like conductor 22 from some of the needle-like pores 21P of 20 does not occur, and the flatness of the surface can be maintained.
The method for reducing the surface roughness of the insulator layer 50 is not particularly limited, and an etching process such as a reverse sputtering process is preferable.
Here, “reverse sputtering treatment” means that plasma is generated on the substrate side by reversing the bias voltage applied to the substrate and the evaporation source during sputtering, and the material on the substrate surface is evaporated by ion collision in the plasma. It is a process to make. In this process, since ion collision is likely to occur in a relatively convex portion, it preferentially evaporates and the substrate becomes flat.

When the arithmetic average roughness Ra of the surface of the insulating layer 50 after the step (E) is more than 10 nm, the arithmetic average roughness Ra of the surface of the insulating layer 50 may be 10 nm or less in the step (F). preferable.

By performing the steps (A) to (F), the arithmetic average roughness Ra of the surface of the finally obtained device can be made 100 nm or less, 70 nm or less, or 10 nm or less.
By carrying out steps (A) to (F), the surface roughness of the finally obtained device can be reduced, improving the light emission characteristics such as in-plane uniformity of light emission, light emission luminance, and light emission efficiency. The EL element 1 can be provided.
In addition, since the insulator layer 50 serving as a barrier layer prevents an electric field from being applied to the light emitter layer 30, the components of the needle-like conductor 22 formed inside the needle-like pores 21P are added to the light emitter layer 30. The thinner one is preferable as long as it is possible to prevent diffusion and inactivation of light emission. By reducing the surface roughness of the insulator layer 50 that becomes a barrier layer by etching or the like, the insulator layer 50 can be made thinner than that at the time of film formation, which is preferable.

(Subsequent processes)
After the step (F), the EL element 1 is manufactured by forming the upper electrode layer 40 after forming the insulator layer 60 which is preferably a cap layer by a known method.

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.

Regardless of which structure and method is adopted, after the needle-like conductor layer 20 is formed, the surface roughness is reduced by surface polishing or the like, so that a plurality of needles inside the plurality of needle-like pores 21P. The variation in the filling rate of the conductors 22 can be reduced, and the surface roughness of the element finally obtained can be reduced. As a result, it is possible to provide the EL element 1 with improved light emission characteristics such as in-plane uniformity of light emission, light emission luminance, and light emission efficiency.

Whichever structure and method is employed, the needle-like conductor layer 20 is formed, the insulator layer 50 is formed as a barrier layer, and the temperature is equal to or higher than the maximum temperature of the EL element manufacturing process after this step. After the heat treatment, the surface roughness of the finally obtained element can be reduced by reducing the surface roughness of the insulator layer 50 by etching or the like. As a result, it is possible to provide the EL element 1 with improved light emission characteristics such as in-plane uniformity of light emission, light emission luminance, and light emission efficiency. This method also provides an effect that the insulator layer 50 serving as a barrier layer can be made thinner than that during film formation.

The present invention can be applied to both inorganic EL elements and organic EL elements, and can be preferably applied to inorganic EL elements.

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

<Test Example 1>
A 100 × 100 mm aluminum plate with a purity of 99.99% (4N) and a thickness of 3 mm manufactured by Nippon Light Metal Co., Ltd. electropolished with a perchloric acid and ethanol mixed solution was subjected to anodization treatment under the following conditions, An alumina layer having acicular pores was formed.
The arithmetic average roughness Ra of the aluminum plate was 113 nm as a result of measurement with a contact-type step gauge (Veeco, DEKTAK150).
-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%.

After formation of the acicular conductor layer, surface polishing is performed with a buffing device (Malto, Dialap, ML-150P), and the non-sealed portion remaining on the upper portion of the acicular pores during the electrolytic deposition of Ni Was removed.
Surface polishing was performed in two steps. Using a water-resistant abrasive paper with a large particle size (Sankyo Rikagaku Co., Ltd., average particle size 7.9 μm, No. 2000) and a liquid abrasive (Malto Co., Ltd., diamond slurry, average particle size 0.5 μm) Conducted for 30 minutes. Thereafter, a second polishing was carried out 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, average particle diameter: 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.
By the above surface polishing, the filling rate of the acicular conductors in all the acicular pores was set to 100%.

Next, a silicon oxynitride SiON film was formed by oxygen-added sputtering using a silicon nitride Si ₃ N ₄ pellet as a target. The degree of vacuum during 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 2 nm / min to obtain a SiON barrier layer having a thickness of 100 nm.

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 during 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 to obtain a ZnS: Mn phosphor layer having a thickness of 800 nm. 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, silicon oxynitride SiON was formed by sputtering under the same conditions as the SiON barrier layer to obtain a 100 nm thick SiON cap layer.

Next, heat treatment was performed 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.

The surface of the acicular conductor layer after surface polishing was observed with an optical microscope (manufactured by Nakaden Co., Ltd., digital microscope MX-1200II). A photomicrograph is shown in the right figure of FIG.
The arithmetic average roughness Ra of the needle-like conductor layer after surface polishing was measured with a contact-type step gauge (Veeco, DEKTAK150), and it was 1.5 nm.

With respect to the obtained inorganic EL element, the state of light emission was observed using an optical microscope (manufactured by Nakaden Co., Ltd., digital microscope MX-1200II) when 200 V AC voltage with a frequency of 1 kHz was applied. A photomicrograph is shown in the right figure of FIG. The black shadow in the photograph is an electrode probe for applying voltage.
In Test Example 1 in which the surface of the needle-shaped conductor layer was polished, the obtained inorganic EL element had no light emission unevenness and high in-plane light emission uniformity.

About the obtained inorganic EL element, the alternating voltage of frequency 1kHz was applied with alternating current power supply, and the luminance and luminous efficiency in voltage 200V were evaluated. The emission luminance was measured with a color luminance meter (BM7 manufactured by Topcon Corporation).
The light emission luminance was 1516 [cd / m ² ], and the light emission efficiency was 1.0 [lm / W].

About the obtained element, cross-sectional TEM (transmission electron microscope) observation and surface SEM (scanning electron microscope) observation were implemented.
A cross-sectional TEM image is shown in FIG. 8A, and a surface SEM image is shown in the left figure of FIG. 8B. In the cross-sectional TEM image, the same components as those in FIG.
It was observed that the needle-like conductor protruded from a part of the needle-like pores of the needle-like conductor layer and a convex portion was formed on the surface of the needle-like conductor layer. The surface of each of the barrier layer, the light emitter layer, the cap layer, and the upper electrode layer, which are upper layers of the acicular conductor layer, has an arcuate cross-sectional view derived from the convex portion of the acicular conductor layer. Convex parts were seen. The surface of the convex portion of each layer had an arc shape spreading at the same angle in cross-sectional view. Since the radius of the circular arc in a sectional view of the surface of the convex portion increases toward the upper layer, the width and height of the convex portion increase and the surface unevenness increases as it moves toward the upper layer.
Using a contact-type step meter (DEKTAK150, manufactured by Veeco), the surface step measurement in one direction of the obtained element was performed. The measurement results are shown in the right figure of FIG. 8B. The resulting device had a surface step of 50 to 70 nm and an arithmetic average roughness Ra of 62 nm.

In Test Example 1, as compared with Comparative Example 1 described later, the surface roughness of the obtained element was reduced, and the light emission characteristics were good. However, the needle-like conductor protrudes from a part of the needle-like pores of the needle-like conductor layer to form a convex portion on the surface of the needle-like conductor layer, and the surface of the obtained element is observed to be uneven although it is minute. It was.

Table 1 shows the main manufacturing conditions and evaluation results of Test Example 1.

<Test Example 2>
For the needle-shaped conductor layer, only polishing using a polishing cloth having a small particle size (manufactured by Maruto, hard polishing cloth MM414) and a liquid abrasive (manufactured by Fujimi, colloidal silica, average particle size of 70 nm) is performed for 30 minutes. An inorganic EL element was produced under the same conditions as in Test Example 1 except that.
Also in this example, the filling rate of the acicular conductors in all the acicular pores was 100%.
Similar to Test Example 1, the arithmetic average roughness Ra of the needle-shaped conductor layer after surface polishing, the arithmetic average roughness Ra of the element, the presence or absence of light emission unevenness using an optical microscope, and the light emission luminance and light emission efficiency of the element Evaluated. Table 1 shows main production conditions and evaluation results of Test Example 2.

<Test Example 3>
For the acicular conductor layer, a polishing cloth having a large particle size (manufactured by Sankyo Rikagaku Co., Ltd., average particle size of 16 μm, No. 1000) and a liquid abrasive (manufactured by Marto, Inc., diamond slurry, average particle size of 3.0 μm) were used. An inorganic EL element was produced under the same conditions as in Test Example 1 except that only polishing was performed for 30 minutes.
Also in this example, the filling rate of the acicular conductors in all the acicular pores was 100%.
Similar to Test Example 1, the arithmetic average roughness Ra of the needle-shaped conductor layer after surface polishing, the arithmetic average roughness Ra of the element, the presence or absence of light emission unevenness using an optical microscope, and the light emission luminance and light emission efficiency of the element Evaluated. Table 1 shows main production conditions and evaluation results of Test Example 3.

<Test Example 4>
In the same manner as in Test Example 1, formation of an alumina layer having a plurality of needle-shaped pores, formation of a plurality of needle-shaped conductors inside the plurality of needle-shaped pores of the alumina layer, and the obtained needle-shaped conductor Surface polishing of the layer and formation of the barrier layer were performed.
Next, heat treatment was performed at 500 ° C. for 1 hour in a nitrogen atmosphere.
Next, the barrier layer was planarized by reverse sputtering treatment. In this step, in the sputtering apparatus, the bias voltage applied to the substrate and the evaporation source was reversed to the normal state to generate plasma on the substrate side, and the material on the substrate surface was evaporated by ion collision in the plasma. The degree of vacuum was set to 5 × 10 ⁻⁴ Pa or less and the sputtering rate was 4 nm / min, and the surface layer (50 nm thickness) of the SiO ₂ barrier layer was removed to flatten the surface.
After planarization of the barrier layer, a light emitting layer, a cap layer, and an upper electrode were formed in the same manner as in Example 1 to obtain an inorganic EL element.

In Test Example 4, the same evaluation as in Test Example 1 was performed.
The surface SEM image of the obtained element and the result of the surface step measurement in one direction of the element surface are shown in the left and right diagrams of FIG. In Test Example 1, minute protrusions were found on the element surface, but in Test Example 4, no protrusions were found on the element surface, and an element with high surface flatness was obtained.
The main production conditions of Test Example 4, the arithmetic average roughness Ra of the needle-shaped conductor layer after surface polishing, the arithmetic average roughness Ra of the element, the presence or absence of light emission unevenness using an optical microscope, and the light emission luminance of the element The evaluation results of luminous efficiency are shown in Table 1.

<Comparative Example 1>
An inorganic EL element was produced under the same conditions as in Test Example 1 except that the surface polishing of the acicular conductor layer was not performed. In this example, the filling rate of the acicular conductor inside the acicular pores was 70 to 100%.

In Comparative Example 1, the same evaluation as in Test Example 1 was performed.
An optical micrograph of the acicular conductor layer of Comparative Example 1 is shown in FIG.
About the element obtained in the comparative example 1, the mode of light emission when 200V of alternating voltage of frequency 1kHz was applied was observed using the optical microscope. A photomicrograph is shown in FIG. The black shadow in the photograph is an electrode probe for applying voltage.
In Comparative Example 1 where the surface polishing of the needle-shaped conductor layer was not performed, the surface roughness of the needle-shaped conductor layer was large, and light emission unevenness was observed in the obtained inorganic EL element.
The main production conditions of Comparative Example 1, the arithmetic average roughness Ra of the acicular conductor layer, the arithmetic average roughness Ra of the element, the presence or absence of light emission unevenness using an optical microscope, and the evaluation of the light emission luminance and light emission efficiency of the element The results are shown in Table 1.

<Summary of results>
As shown in Table 1, in the test examples 1 and 2 in which the needle-like conductor layer was formed and the surface on the light-emitting body layer side was polished so that the arithmetic average roughness Ra was 10 nm or less, the needle-like conductor was used. An inorganic EL element having higher light emission luminance and light emission efficiency than Test Example 3 and Comparative Example 1 in which the arithmetic average roughness Ra of the surface of the body layer on the light emitter layer side was more than 10 nm was obtained.
After forming the acicular conductor layer, the surface on the light emitter layer side is polished so that the arithmetic average roughness Ra is 10 nm or less. Further, after forming the barrier layer, heat treatment and surface flattening treatment are performed. In Test Example 4 that was performed, an inorganic EL element having a small surface roughness and high light emission luminance and light emission efficiency was obtained.

This application is Japanese Patent Application No. 2012-249293 filed on November 13, 2012, Japanese Patent Application No. 2012-249294 filed on November 13, 2012, and filed on November 13, 2012 Claiming priority based on Japanese Patent Application No. 2012-249295 filed in Japan and Japanese Patent Application No. 2013-107797 filed on May 22, 2013, the entire disclosure of which is incorporated herein.

1, 2 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 (21)

1. An electroluminescent device comprising a first electrode layer, a light emitter layer, and a second electrode layer having translucency in order,
   further,
   Between the first electrode layer and the phosphor layer,
   An insulator composed of a pore structure having a plurality of needle-like pores that are open in the surface on the light emitter layer side and extend in a crossing direction with respect to the surface on the light emitter layer side; A needle-like conductor layer including a plurality of needle-like conductors formed inside the hole,
   The electroluminescent element whose arithmetic mean roughness Ra of the element surface by the side of said 2nd electrode layer is 100 nm or less.
2. The electroluminescent device according to claim 1, wherein the arithmetic mean roughness Ra of the device surface is 70 nm or less.
3. The electroluminescent device according to claim 1, wherein the arithmetic mean roughness Ra of the device surface is 10 nm or less.
4. The electroluminescent device according to any one of claims 1 to 3, wherein a conductor layer is not provided between the acicular conductor layer and the light emitting layer.
5. The electroluminescent device according to any one of claims 1 to 4, wherein the pore structure is a metal oxide obtained by anodizing at least a part of the metal to be anodized.
6. The pore structure is a metal oxide body obtained by anodizing a part of the anodized metal body,
   The electroluminescent element according to claim 5, wherein the first electrode layer is a remaining part of the metal to be anodized remaining after anodization.
7. 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 6. The electroluminescent device according to Item 5.
8. 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.
9. The electroluminescent device according to any one of claims 1 to 8, wherein the needle-like conductor has a length of 1 µm or more.
10. 10. The electroluminescent device according to claim 1, wherein the needle-like conductor has a diameter of 0.5 μm or less.
11. The electroluminescent device according to any one of claims 1 to 10, wherein the length / diameter of the acicular conductor is 100 or more.
12. 12. The electroluminescent device according to claim 1, wherein the number density of the needle-like conductors in the needle-like conductor layer is 1 piece / μm ² or more.
13. The electroluminescent device according to any one of claims 1 to 12, further comprising an insulator layer between the acicular conductor layer and the light emitting layer.
14. The electroluminescent device according to any one of claims 1 to 13, wherein a distance between the acicular conductor and the light emitting layer is 1 µm or less.
15. The electroluminescent device according to any one of claims 1 to 14, further comprising an insulator layer between the phosphor layer and the second electrode layer.
16. A first electrode layer, a light emitter layer, and a second electrode layer having translucency are sequentially provided,
    further,
    Between the first electrode layer and the phosphor layer,
    An insulator composed of a pore structure having a plurality of needle-like pores that are open in the surface on the light emitter layer side and extend in a crossing direction with respect to the surface on the light emitter layer side; A method of manufacturing an electroluminescent element comprising a needle-shaped conductor layer including a plurality of needle-shaped conductors formed inside a hole,
    Preparing the insulator comprising a pore structure having the plurality of acicular pores (A);
    Forming the plurality of needle-shaped conductors inside the plurality of needle-shaped pores of the insulator to obtain the needle-shaped conductor layer (B);
    And a step (C) of reducing the arithmetic average roughness Ra of the surface of the acicular conductor layer.
17. The arithmetic average roughness Ra of the surface of the acicular conductor layer obtained after the step (B) is more than 10 nm,
    The method of manufacturing an electroluminescent element according to claim 16, wherein in the step (C), the arithmetic average roughness Ra of the surface of the acicular conductor layer is 10 nm or less.
18. After step (C)
    A step (D) of forming an insulator layer serving as a barrier layer for preventing the acicular conductor component from diffusing into the light emitter layer;
    A step (E) of performing a heat treatment at a temperature equal to or higher than a maximum temperature of the manufacturing process of the electroluminescent element after the step (D);
    The method for producing an electroluminescent element according to claim 16, further comprising a step (F) of reducing the arithmetic average roughness Ra of the surface of the insulator layer after the step (E).
19. The arithmetic average roughness Ra of the surface of the insulator layer after the step (E) is more than 10 nm,
    The method of manufacturing an electroluminescent element according to claim 18, wherein in the step (F), the arithmetic average roughness Ra of the surface of the insulator layer is 10 nm or less.
20. In the step (A), a metal oxide body obtained by anodizing at least a part of a metal body to be anodized having a surface arithmetic average roughness Ra of 200 nm or less is prepared as the insulator. 20. The method for producing an electroluminescent device according to any one of items 19 to 19.
21. In the step (A), as the insulator, a metal oxide body obtained by anodizing at least a part of an anodized metal body having a purity of a main component metal element of 99.9% by mass or more is prepared. The method for producing an electroluminescent element according to any one of claims 16 to 20.

Images