JP2014099272A - Electroluminescence element and method for manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an EL element capable of improving emission luminance and luminous efficiency without applying high electric field.SOLUTION: An EL element 1 has a first electrode layer 10, an emitter layer 30 and a second electrode layer 40, serially. The EL element 1 consists of a metal oxide positioned between the first electrode layer 10 and the emitter layer 30 and obtained by anodizing a part of a metal to be anodized, and has a plurality of acicular conductors 22 extending to a direction intersecting with a surface 30S of the first electrode layer 10 side of the emitter layer 30, and an acicular conductor layer 20 containing insulators 21 insulating between a plurality of acicular conductors 22. In a method for manufacturing the EL element 1, the metal to be anodized having a surface arithmetic average roughness before the anodizing, of equal to or less than 200 nm, is used.

Description

  The present invention relates to an electroluminescent device 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 host 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 Laid-Open No. 2004-131583

J. Electrochem. Soc., Vol.110, No.7, 733-748 (1963)

  In the conventional thin-film inorganic EL element described in Patent Document 1 or 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 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,
A plurality of metal oxide bodies obtained by anodizing at least a part of a metal body to be anodized, open on the surface of the light emitter layer side, and extend in a direction intersecting the surface of the light emitter layer side An electroluminescent device comprising a needle-like conductor layer including an insulator composed of a pore structure having needle-like pores and a plurality of needle-like conductors formed inside the plurality of needle-like pores A manufacturing method of
A step (A) of preparing the anodized metal body having an arithmetic average roughness Ra of the surface before anodization of 200 nm or less;
A step (B) for producing the metal oxide body by anodizing at least part of the anodized metal body;
And a step (C) of forming the plurality of needle-shaped conductors inside the plurality of needle-shaped pores of the metal oxide body to obtain the needle-shaped conductor layer.

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,
A plurality of metal oxide bodies obtained by anodizing at least a part of a metal body to be anodized, open on the surface of the light emitter layer side, and extend in a direction intersecting the surface of the light emitter layer side A needle-like conductor layer comprising an insulator composed of a pore structure having needle-like pores and a plurality of needle-like conductors formed inside the plurality of needle-like pores;
It is manufactured using the metal body to be anodized whose arithmetic average roughness Ra of the surface before anodization is 200 nm or less.

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. 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 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. 3 is a SEM image of an EL element obtained in Test Example 1. 4 is a SEM image of an EL element obtained in Test Example 2.

"EL element"
With reference to the drawings, a structure of an EL device according to an embodiment of the present invention and a manufacturing method thereof 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 a manufacturing process of the pore structure.
The left figure of FIG. 3 shows the EL element when the surface polishing of the acicular conductor layer is not performed, and the right figure of FIG. 3 shows the EL element when the surface polishing of the acicular conductor layer is performed ( It is a schematic cross section which shows the mode of the EL element of this embodiment.
4 and 5 are diagrams showing examples of design changes.
1, 4, and 5, 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 FIG. 2A-FIG. 2B, the manufacturing method and structure of the pore structure 21 are demonstrated.
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.

The manufacturing method of the EL element 1 of the present embodiment is as follows:
A step (A) of preparing an anodized metal body M having an arithmetic average roughness Ra of the surface before anodization of 200 nm or less;
A step (B) of producing a metal oxide body by anodizing at least a part of the anodized metal body M;
A step (C) of forming a plurality of needle-shaped conductors 22 inside the plurality of needle-shaped pores 21P of the metal oxide body to obtain the needle-shaped conductor layer 20;

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. 6). 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. 6 is schematic, and the actual direction of stress is a crossing direction such as a direction perpendicular to the direction of rolling bars.

FIG. 7 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 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 field lines become, and the density of the electric field lines is proportional to the 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 depending 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 needle-like conductors 22 inside the individual needle-like pores 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 acicular pore 21P is determined in consideration of the preferable length of the acicular conductor 22 and the filling rate of the acicular conductor 22 inside the acicular pore 21P.

The manufacturing method of the EL element 1 of the present embodiment is as follows:
It is preferable to have the process (D) of grind | polishing the surface of the acicular conductor layer 20, and making arithmetic mean roughness Ra of the surface small.

In the step (D), the arithmetic average roughness Ra of the surface of the acicular conductor layer 20 is preferably 10 nm or less.
The arithmetic average roughness Ra of the surface of the acicular conductor layer 20 on the light emitter layer 30 side is small, preferably 10 nm or less, so that the plural acicular conductors 22 inside the acicular pores 21P are formed. Variation in filling rate can be reduced.
Even if the surface of the needle-shaped conductor layer 20 is polished, if there are polishing scratches or the like on the surface, the surface roughness becomes large, the in-plane electric field stimulation is not uniform, and the luminous efficiency may decrease. There is. By setting the arithmetic average roughness Ra of the surface of the acicular conductor layer 20 on the light emitter layer 30 side to be small, preferably 10 nm or less, in-plane electric field stimulation can be made uniform.
Due to the above effects, the in-plane uniformity of light emission can be increased, and the light emission efficiency can be increased.
The left figure of FIG. 3 shows the EL element when the surface polishing of the acicular conductor layer 20 is not performed, and the right figure of FIG. 3 shows the EL when the surface polishing of the acicular conductor layer 20 is performed. It is a schematic cross section which shows the mode of an element (EL element 1 of this embodiment).

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 is 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 is 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 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. 5, 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. 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 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.

The phosphor layer 30 is a layer that emits light when excited in an electric field. The thickness of the luminous body layer 30 is preferably thinner from the viewpoint of concentrating the electric field near the tip of the needle-like conductor 22, and specifically, a range of 0.05 to 2 μm is preferable.
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 in the design modification example shown in FIGS. 4 and 5, 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 of the design modification example shown in FIGS. 4 and 5, 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.

  In the EL elements 2 and 3 of the design modification examples shown in FIGS. 4 and 5, there is shown an aspect in which both the insulator layer 50 functioning as a barrier layer and the insulator layer 60 functioning as a cap layer are provided. Only one of the body 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.

  The EL element 1 of this embodiment is manufactured using an anodized metal body M whose surface has an arithmetic average roughness Ra of 200 nm or less before anodic oxidation. Therefore, in the pore structure 21 which is a metal oxide body obtained by anodic oxidation, stress is suppressed in a specific direction, and the device withstand voltage is improved. Moreover, it leads to reduction of the surface roughness of the acicular conductor layer 20, and the improvement effect of light emission luminance is also acquired.

  In the present embodiment, the arithmetic average roughness Ra of the surface of the acicular conductor layer 20 on the light emitter layer 30 side is small, preferably 10 nm or less, and therefore a plurality of acicular shapes inside the acicular pores 21P. The variation in the filling rate of the conductor 22 can be reduced, the in-plane uniformity of light emission can be increased, and the light emission efficiency can be increased.

According to the present embodiment, combined with the above-described effects, it is possible to improve both the light emission luminance and the light emission efficiency without applying a high electric field, and to provide an EL element 1 with a high element withstand voltage. can do.
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 test examples, but the present invention is not limited thereto.

<Test Examples 1 and 2>
In each example, the arithmetic average roughness Ra was different, and the same aluminum plate was prepared under other conditions. In any example, the aluminum plate had a thickness of 3 mm and a size of 100 × 100 mm.
In Test Example 1, the rolling streaks of the aluminum plate were removed by chemical polishing in which a commercially available aluminum plate was immersed in an acidic aqueous solution mixed with 40% by mass phosphoric acid and 10% by mass nitric acid for 60 minutes. Next, in order to remove the oxide film on the surface, mechanical polishing was performed using a buff polishing apparatus (Diarup, manufactured by Marto, ML-150P). Surface polishing was carried out for 10 minutes using a polishing cloth having a small particle size (manufactured by Marto, Inc., hard polishing cloth MM414) and a liquid abrasive (manufactured by Fujimi, colloidal silica, average particle diameter of 70 nm). After the surface polishing, the abrasive grains remaining on the surface were removed by washing with water.
In Test Example 2, a commercially available aluminum plate was used as it was.
The arithmetic average roughness Ra of the aluminum plate was measured with a contact-type step gauge (Veeco, DEKTAK150).
Table 1 shows the arithmetic average roughness Ra of the aluminum plate.
The aluminum plate used is a rolled body, where Ra in the direction perpendicular to the rolling direction (lateral direction)> Ra in the direction parallel to the rolling direction (longitudinal direction).
Ra in Table 1 is data in the horizontal direction.

The aluminum plate was anodized under the following conditions to form an alumina layer having a plurality of needle-like pores.
-Counter electrode (cathode): Aluminum-Electrolyte: 0.3 M sulfuric acid-Bath temperature: 15-19 ° C
・ Voltage: DC 40V
・ Time: 100 minutes

About the obtained alumina layer, the surface and the cross section were observed using the scanning electron microscope (SEM, Hitachi Ltd. make, S-4800). 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, mixed solution of 0.1M ammonium sulfate and 0.5M boric acid Bath temperature: 22-25 ° C
-PH: 4.0-4.5
・ Voltage: AC 10V (50Hz)
・ Processing time: 30 minutes

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

After the formation of the acicular conductor layer, the surface is polished with a buffing device (Malto, Dialap, ML-150P), and the non-sealed portion remaining on the upper portion of the acicular pores during Ni electrolytic deposition 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.
In this example, the filling rate of the acicular conductors in all the acicular pores was 100%.
The average pore length after surface polishing was 8 μm.

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 the deposition was set to 5 × 10 ⁻⁴ Pa or less, the substrate temperature was set to 200 ° C., and the 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 pellet obtained by sintering ZnS powder added with 0.5 mass% Mn 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 20 nm / min to obtain a ZnS: Mn phosphor layer having a thickness of 800 nm.

  Next, silicon oxynitride SiON was formed by sputtering under the same conditions as the SiON barrier layer to obtain a SiON cap layer having a thickness of 100 nm.

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.

<Evaluation 1>
The EL element obtained in each example was applied with an AC voltage having a frequency of 1 kHz from an AC power source, and the light emission luminance at a voltage of 200 V was evaluated. The emission luminance was measured with a color luminance meter (BM7 manufactured by Topcon Corporation). In Test Example 2, light emission could not be obtained due to dielectric breakdown when 160 V was applied, so the light emission luminance at a voltage of 160 V was evaluated.
Further, the applied voltage was increased, and the voltage at which light emission could not be obtained due to dielectric breakdown was determined as the device withstand voltage.
The evaluation results are shown in Table 1.

  As shown in Table 1, in Test Example 1 using an aluminum plate having a surface arithmetic average roughness Ra of 200 nm or less, compared to Test Example 2 using an aluminum plate having a surface arithmetic average roughness Ra of more than 200 nm. An EL element with high luminance and high element withstand voltage was obtained.

<Evaluation 2>
About the EL element obtained in each example, after the said evaluation, surface observation with a scanning electron microscope (SEM, the product made by KEYENCE Inc., VE-9800) was implemented. Surface SEM images are shown in FIGS.
As shown in FIG. 8, no cracks in the element were observed in Test Example 1 using an aluminum plate having a surface arithmetic average roughness Ra of 200 nm or less.
As shown in FIG. 9, in Test Example 2 using an aluminum plate having a surface arithmetic average roughness Ra of more than 200 nm, cracks in the element were observed.

1-3 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)

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,
A plurality of metal oxide bodies obtained by anodizing at least a part of a metal body to be anodized, open on the surface of the light emitter layer side, and extend in a direction intersecting the surface of the light emitter layer side An electroluminescent device comprising a needle-like conductor layer including an insulator composed of a pore structure having needle-like pores and a plurality of needle-like conductors formed inside the plurality of needle-like pores A manufacturing method of
A step (A) of preparing the anodized metal body having an arithmetic average roughness Ra of the surface before anodization of 200 nm or less;
A step (B) for producing the metal oxide body by anodizing at least part of the anodized metal body;
And a step (C) of forming the plurality of needle-shaped conductors inside the plurality of needle-shaped pores of the metal oxide body to obtain the needle-shaped conductor layer. further,
The method for producing an electroluminescent element according to claim 1, further comprising a step (D) of polishing the surface of the acicular conductor layer to reduce the arithmetic average roughness Ra of the surface. 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,
A plurality of metal oxide bodies obtained by anodizing at least a part of a metal body to be anodized, open on the surface of the light emitter layer side, and extend in a direction intersecting the surface of the light emitter layer side A needle-like conductor layer comprising an insulator composed of a pore structure having needle-like pores and a plurality of needle-like conductors formed inside the plurality of needle-like pores;
An electroluminescent device manufactured using the metal body to be anodized, wherein the arithmetic average roughness Ra of the surface before anodization is 200 nm or less.   The electroluminescent element according to claim 3, wherein a conductor layer is not provided between the needle-like conductor layer and the light emitting layer. The pore structure is a metal oxide body obtained by anodizing a part of the anodized metal body,
5. The electroluminescent device according to claim 3, wherein the first electrode layer is a remaining part of the anodized metal body remaining after anodization.   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 3 or 4.   The said acicular conductor contains at least 1 sort (s) of metal selected from the group which consists of Ag, Au, Cd, Co, Cu, Fe, Ni, Sn, and Zn. Electroluminescence element. The electroluminescent element according to any one of claims 3 to 7, wherein a number density of the acicular conductors in the acicular conductor layer is 1 piece / µm ² or more.   The electroluminescent element according to any one of claims 3 to 8, wherein the length of the acicular conductor is 1 µm or more.   The electroluminescent element according to any one of claims 3 to 9, wherein the needle-like conductor has a diameter of 0.5 µm or less.   The length / diameter of the said acicular conductor is 100 or more, The electroluminescent element in any one of Claims 3-10.   The electroluminescent element according to any one of claims 3 to 11, further comprising an insulator layer between the acicular conductor layer and the light emitting layer.   The electroluminescent element according to claim 3, wherein a distance between the acicular conductor and the light emitting layer is 1 μm or less.   The electroluminescent element according to claim 3, further comprising an insulator layer between the light emitting layer and the second electrode layer.