JP6642581B2 - Method of manufacturing organic light emitting diode and organic light emitting diode - Google Patents

Description

The present invention relates to a manufacturing method and an organic light emitting diode of organic light emitting diodes. Priority is claimed on Japanese Patent Application No. 2015-178324 filed on September 10, 2015, the content of which is incorporated herein by reference.

  An organic light emitting diode is a light emitting element using organic electroluminescence. An organic light emitting diode generally has a configuration in which an anode and a cathode are provided on both surfaces of an organic semiconductor layer including a light emitting layer containing an organic light emitting material. The organic semiconductor layer has an electron injection layer, an electron transport layer, a hole transport layer, a hole injection layer, and the like, as necessary, in addition to the light emitting layer. Organic light-emitting diodes have advantages such as low viewing angle dependence, low power consumption, and the ability to be extremely thin.

On the other hand, organic light emitting diodes do not always have sufficient light extraction efficiency. The light extraction efficiency is the ratio of the light energy emitted from the light extraction surface (for example, the base surface in the case of a bottom emission type) to the air with respect to the light energy generated in the light emitting layer.
One of the factors that lower the light extraction efficiency is the effect of surface plasmons. In an organic light emitting diode, the distance between a light emitting layer and a metal cathode is short. Therefore, part of the near-field light generated in the light-emitting layer is converted to surface plasmon on the surface of the cathode and is lost, and the light extraction efficiency of the organic light-emitting diode decreases. The light extraction efficiency is an index that affects the brightness of a display including an organic light emitting diode, lighting, and the like, and various methods for improving the efficiency are being studied.

  In order to increase the light extraction efficiency, Patent Document 1 discloses a structure in which a two-dimensional lattice structure including convex portions or concave portions is provided on the surface of a metal layer (cathode). The two-dimensional lattice structure on the surface of the metal layer converts surface plasmon energy into light, and the converted light is extracted outside the device. In Patent Literature 1, the two-dimensional lattice structure on the surface of the metal layer is obtained by reflecting the two-dimensional lattice structure provided on the base. Specifically, by laminating a first electrode, an organic semiconductor layer including a light emitting layer, and a second electrode on a substrate provided with a two-dimensional lattice structure, a substrate is formed on the surface of the second electrode on the light emitting layer side. It reflects an equivalent two-dimensional lattice structure.

  Generally, the organic semiconductor layer and the first and second electrodes are formed by a vacuum film forming method using a sputtering method or an evaporation method. On the other hand, Patent Document 2 discloses that an organic semiconductor layer in an organic thin-film solar cell is formed by a coating method such as a spin coating method, an inkjet method, and a slit coating method. The organic thin-film solar cell has the same configuration as the organic light-emitting diode, and the organic semiconductor layer of the organic light-emitting diode can also be formed by a coating method.

International Publication No. WO 2012/60404 International Publication No. WO 2014/208713

  However, a method of processing a two-dimensional lattice structure on a substrate, such as the method described in Patent Document 1, has a problem in that the processing cost of the substrate increases. In addition, when the two-dimensional lattice structure is manufactured by processing the base, there is a problem that the organic semiconductor layer formed on the base cannot be formed using the coating method described in Patent Document 2. Since the coating method uses a liquid phase material at the time of coating, the uneven shape (two-dimensional lattice structure) is easily filled. Therefore, the reflectivity of the irregularities on the surface of the substrate is lower on the surface of the metal layer than in the vacuum film forming method. If the reflectivity of the shape is low, it is difficult to provide the second electrode with a desired shape necessary for extracting surface plasmons.

On the other hand, forming an organic semiconductor layer or the like by coating has advantages such as a reduction in manufacturing cost due to simplification of manufacturing equipment and an improvement in throughput by shortening time for evacuation and the like. Therefore, there is a strong demand for forming an organic semiconductor layer using a coating method.

  Therefore, the present inventors have adopted a method of manufacturing an organic light-emitting diode by sequentially performing a coating step, a stamper step for forming an uneven shape, and a vacuum film forming step. In this method, at least a part of the organic semiconductor layer is formed by a coating method in a coating step. Next, a mold having a shape opposite to the desired unevenness is pressed against the outermost surface of the coating layer obtained in the coating step, and the desired unevenness is formed on the outermost layer of the coating layer. Finally, the remaining layers not formed in the coating step are formed by a vacuum film forming method. This method has the advantage of reducing the processing cost of the substrate because there is no need to process the substrate, the advantage that the number of layers to be formed by vacuum film formation can be reduced, the advantage that the production throughput can be improved, and the uneven shape. After the formation, since the vacuum film formation method is used, there is an advantage that a desired uneven shape can be reflected on the second electrode.

  However, as a result of further studies, the inventors have found that an organic light-emitting diode manufactured by combining the coating step, the stamper step, and the vacuum film-forming step cannot obtain a sufficient luminous intensity compared to an assumed luminous intensity. I noticed a problem.

  The present invention has been made in view of the above circumstances. It is an object to provide a mold for manufacturing an organic light emitting diode that can exhibit sufficient light emitting characteristics even when a method combining an application step, a stamper step, and a vacuum film forming step is used.

The present inventors have intensively studied to solve the above problems.
As a result, by setting the shape of the mold to a predetermined shape, even when the organic light emitting diode is manufactured by combining the coating step, the stamper step, and the vacuum film forming step, the organic light emitting diode can exhibit sufficient light emitting characteristics. I found what I could do.

The present invention includes the following inventions.
(1) A mold according to one aspect of the present invention has a flat surface on a main surface and a plurality of protrusions, an average pitch of the plurality of protrusions is 50 nm to 5 μm, and the plurality of protrusions is Has an average aspect ratio of 0.01 to 1, and at least 80% of the plurality of projections have a predetermined curved surface. A second tangent plane contacting the second point with respect to a first tangent plane contacting the first point when a point is shifted from the first point by 1/10 of the average pitch as a second point; Is within 60 °.

(2) In the mold according to (1), an area ratio of the flat surface to the main surface may be 5 to 50%.

(3) In the mold according to any one of (1) and (2), the flat surface and the convex portion having the predetermined curved surface are connected so as to satisfy a condition of the predetermined curved surface. May be.

(4) In the mold according to any one of the above (1) to (3), the predetermined curved portion constituting the plurality of convex portions has at least one or more inflection portions, The closest distance from the first inflection portion closest to the flat surface to the flat surface among the inflection portions may be 1/10 or more of the average pitch of the plurality of projections.

(5) The mold according to any one of (1) to (4), wherein the plurality of protrusions form a honeycomb lattice, and the tops of the plurality of protrusions are on the flat surface. In a plan view from a direction perpendicular to the honeycomb lattice, the honeycomb lattice may be located at a vertex of a hexagon constituting the honeycomb lattice.

(6) The mold according to (5), wherein the convex portion located at the apex of the hexagon has a ridge line portion between the convex portion located at the apex adjacent to the hexagon, At least a part of the ridge may be located closer to the flat surface than a protrusion connecting the ridge.

(7) In the mold according to (6), a height of a portion of the ridge portion closest to the flat surface from the flat surface is a height of a convex portion connecting the ridge portion from the flat surface. The height may be 50% to 90%.

(8) In the method for manufacturing an organic light-emitting diode according to one embodiment of the present invention, an organic semiconductor layer including a light-emitting layer is formed on a surface of the substrate with an electrode having a transparent first electrode on the substrate on which the first electrode is formed And a second electrode are formed by an application step and a subsequent vacuum film formation step, wherein the method comprises the steps of (1) to ( 7) A stamper which presses the mold according to any one of the above to the outermost surface of the coating layer formed in the coating step, and forms an inverted shape of the shape of the main surface of the die on the outermost surface of the coating layer. Having a process.

(9) An organic light-emitting diode according to one embodiment of the present invention includes a base, a transparent first electrode, an organic semiconductor layer including a light-emitting layer, and a second electrode in this order. The surface on the semiconductor layer side has a flat surface, and a plurality of protrusions protruding from the flat surface toward the base, an average pitch of the plurality of protrusions is 50 nm to 5 μm, and the plurality of protrusions is The average aspect ratio of the portion is 0.01 to 1, and 80% or more of the plurality of convex portions have a predetermined curved surface, and the predetermined curved surface corresponds to an arbitrary point on the predetermined curved surface. When a point shifted from the first point by 1/10 of the average pitch toward the center point of the convex portion from the first point is defined as a second point, a point corresponding to a first tangent plane contacting the first point is determined. The inclination angle of the second tangent plane contacting the second point is within 60 °.

(10) In the organic light-emitting diode according to (9), an area ratio of the flat surface to a surface of the second electrode on the organic semiconductor layer side may be 5 to 50%.

  In the mold according to one embodiment of the present invention, even when an organic light-emitting diode is manufactured by combining an application step, a stamper step, and a vacuum film formation step, the organic light-emitting diode can exhibit sufficient light-emitting characteristics.

  The organic light-emitting diode according to one embodiment of the present invention has desired light-emitting characteristics and can efficiently extract generated surface plasmons.

  According to the method for manufacturing an organic light-emitting diode of one embodiment of the present invention, an organic light-emitting diode that can efficiently extract surface plasmons can be manufactured at low cost.

1 is a schematic perspective view of a mold according to one embodiment of the present invention. FIG. 3 is a schematic cross-sectional view of the mold according to one embodiment of the present invention, which is cut along a plane passing through a center point of a convex portion formed on the mold and a center point of a flat surface. 1 is a schematic plan view of a mold according to one embodiment of the present invention. It is the figure which cut | disconnected the metal mold | die which concerns on one aspect of this invention in the plane which passes through the center point of the convex part formed in the metal mold, and is sectional drawing to which one convex part was expanded. FIG. 3 is a schematic cross-sectional view when a mold according to one embodiment of the present invention is pressed against a surface of a laminate formed by coating. FIG. 3 is a schematic cross-sectional view when a mold having no predetermined curved surface is pressed against the surface of a laminate formed by coating. FIG. 4 is a schematic cross-sectional view when a mold according to another embodiment of the present invention is pressed against a surface of a laminate formed by coating. FIG. 8 is a schematic cross-sectional view when a layer is formed on the transferred material shown in FIG. 7 by a vacuum film forming method. FIG. 3 is a schematic cross-sectional view of the mold according to one embodiment of the present invention, taken along adjacent protrusions. FIG. 4 is a schematic perspective view of a mold according to another embodiment of the present invention. FIG. 4 is a schematic perspective view of a mold according to another embodiment of the present invention. 1 is a schematic cross-sectional view of an organic light-emitting diode element according to one embodiment of the present invention. It is the figure which looked at the principal part of the metallic mold concerning this embodiment from the direction perpendicular to the flat surface in plane view. It is the figure which showed typically the manufacturing method of the metal mold | die. It is the figure which showed typically the dripping process and the single particle film formation process in the manufacturing process of a metal mold | die.

  Hereinafter, each configuration will be described with reference to the drawings. In the drawings used in the following description, a characteristic portion may be enlarged for convenience in order to make the characteristic easy to understand, and the dimensional ratios and the like of each component are not necessarily the same as the actual one. The materials, dimensions, and the like illustrated in the following description are merely examples, and the present invention is not limited thereto, and can be implemented with appropriate changes without departing from the scope of the invention.

"Mold"
FIG. 1 is a perspective view schematically illustrating a mold according to one embodiment of the present invention. In the mold 10 according to one embodiment of the present invention, a plurality of flat surfaces 1a to 1n and a plurality of protrusions 2a to 2n are provided on a main surface 10A. The plurality of flat surfaces 1a to 1n are provided in a region surrounded by the nearest adjacent protrusion among the plurality of protrusions 2a to 2n. In FIG. 1, a hexagonal shape in plan view is drawn when connecting the center points of the protruding portions that are closest to each other, and a flat surface is provided in a central region thereof. The plurality of protrusions 2a to 2n are partially connected.

  FIG. 2 is a cross-sectional view cut along a plane connecting a center point of a convex portion and a center point of a flat surface of the mold according to one embodiment of the present invention. The cross section as shown in FIG. 2 is obtained as an AFM (atomic force microscope) image or a microscope image obtained by observing a cut sample with an electron microscope.

The cross section by the AFM image is a cut passing through the central point 2An of the convex portion 2n and the central point 1An of the flat surface 1n from an AFM image taken of a square region 30 to 40 times the average pitch P of the convex portions 2a to 2n. It is obtained by extracting the cross section information of the surface.
The cross section is obtained by cutting out a cross section of the mold 10 that passes through the center point 2An of the convex portion 2n using FIB (Focused Ion Beam) or the like. The microscope image of the cross section is obtained by observing the cross section with an optical microscope. If the cross-sectional shape of the mold is likely to be deformed by cutting, it is preferable to cover the surface of the convex portion with a material that can withstand the cutting or to embed the convex portion with resin or the like before cutting.

When both the cross section measured by the AFM image and the cross section observed by the microscope image are obtained, the cross section measured by the AFM image has priority. This is because the cross section measured by the AFM image is easier to obtain a predetermined cut surface and the cross sectional shape can be easily confirmed. When the protrusions 2a to 2n are regularly arranged, it is preferable that the cutting direction for obtaining the cross section be a direction along the arrangement direction of the protrusions 2a to 2n.

The center points 2Aa to 2An of the protrusions 2a to 2n are set based on the AFM measurement results. Specifically, a plurality of contour lines are drawn every 20 nm for each of the protrusions 2a to 2n in parallel with the reference plane, and the center of gravity (point determined by the x coordinate and the y coordinate) of each contour line is obtained. The average position (the position determined by the average of the x-coordinates and the average of the y-coordinates) of these center-of-gravity points is defined as the center point 2Aa-2An of each of the projections 2a-2n. The reference plane is a measurement plane after performing inclination correction from image information having an inclination measured by AFM.
The center points 1Aa to 1An of the flat surfaces 1a to 1n are set based on the AFM measurement results. Specifically, an inscribed circle inscribed in plan view is provided on each of the plurality of flat surfaces 1a to 1n. The center of this inscribed circle is defined as the center points 1Aa to 1An of the flat surfaces 1a to 1n.

  The protrusions 2a to 2n are portions protruding from the flat surfaces 1a to 1n. The flat surfaces 1a to 1n mean a region whose inclination is within ± 5 ° with respect to a plane which passes through the center of gravity of the region connecting the adjacent protrusions and is parallel to the reference plane of the AFM.

The protrusions 2 a to 2 n are two-dimensionally arranged on one surface of the mold 10. “Two-dimensionally arranged” refers to a state in which a plurality of protrusions are arranged on the same plane. The two-dimensional structure in which the plurality of protrusions are two-dimensionally arranged may be periodic or non-periodic.

The mold 10 can be suitably used when forming an uneven shape on an electrode made of a metal of an organic light emitting diode. The uneven shape contributes to extracting surface plasmons generated on the electrode surface. When the organic light-emitting diode manufactured using the mold 10 emits light in a narrow frequency band, the two-dimensional arrangement of the plurality of protrusions is preferably periodic.

As a preferred specific example of the periodic two-dimensional structure, a straight line connecting adjacent convex portions has two orientation directions and a crossing angle of 90 ° (square lattice), and a straight line connecting adjacent convex portions. Having three orientation directions and a crossing angle of 120 ° (hexagonal lattice, honeycomb lattice), and the like.

The “positional relationship where the intersection angle is 120 °” specifically refers to a relationship that satisfies the following conditions. First, a line segment L1 having a length equal to the average pitch P is drawn from one center point 2Aa in the direction of the adjacent center point 2Ab. Next, a line segment L2 having a length equal to the average pitch P is drawn from the center point 2Aa in the direction of 120 ° with respect to the line segment L1. If the center point adjacent to the center point 2Aa is within 15% of the average pitch P from the end point of each line segment L1 on the opposite side to the center point 2Aa, the intersection angle is 120 °. The positional relationship where the intersection angle is 90 degrees is defined by replacing the above description of “120 °” with “90 °”.

When the protrusions 2a to 2n are periodically arranged so as to satisfy the above relationship, the arrangement period of the protrusions 2a to 2n and the period of the surface plasmon resonate, and the light extraction efficiency in a specific frequency band increases. . When the projections 2a to 2n are arranged in a honeycomb lattice, the strength of the mold 10 is increased, and the durability when repeatedly used is particularly enhanced. The honeycomb lattice shape can be rephrased as a relationship in which the tops of the plurality of projections 2a to 2n are located at the vertices of a hexagon in plan view when viewed from a direction perpendicular to the flat surfaces 1a to 1n.

On the other hand, when the organic light-emitting diode manufactured using the mold 10 emits light in a wide frequency band or light in a plurality of different frequency bands, the two-dimensional structure of the plurality of protrusions 2a to 2n is used. The arrangement is preferably aperiodic. The “non-periodic arrangement” refers to a state in which the intervals between the centers of the protrusions 2a to 2n and the arrangement direction are not constant.

Here, the average pitch P is a distance between adjacent convex portions, and can be specifically determined as follows. Here, the adjacent convex portion means an adjacent convex portion without interposing a flat surface in FIG.
First, an AFM image is obtained for a randomly selected area on the main surface 10A of the mold 10, a square area having one side of 30 to 40 times the average pitch P. For example, when the design pitch is about 300 nm, an image of an area of 9 μm × 9 μm to 12 μm × 12 μm is obtained. Then, the adjacent distance between the convexes in the area obtained by measuring, by averaging the distance between adjacent measured to determine the average pitch P ₁ in the region. Such process performed in the same manner for the region of the same area of a total of 25 or more locations selected at random, obtaining an average pitch _{P. 1 to} P ₂₅ in each region. The average value of the average pitches P _{1 to} P _{25 in} the ₂₅ or more regions thus obtained is the average pitch P. At this time, each region is preferably selected at least 1 mm apart, more preferably 5 mm to 1 cm apart.

  The average pitch P of the projections 2a to 2n is 50 nm to 5 μm, and preferably 50 nm to 500 nm. If the average pitch of the protrusions 2a to 2n is within the above range, surface plasmons can be efficiently extracted from the metal electrode in the organic light emitting diode manufactured using the mold 10.

The protrusions 2a to 2n have a periodic structure formed of Ca to Cn for each area. As a macroscopic whole, each of the areas Ca to Cn may have an aperiodic structure. Each of the areas Ca to Cn shown in FIG. 3 is an area in which the intersection angle of the center point of each projection with respect to the center point of the flat surface is aligned in a positional relationship of 120 °. In FIG. 3, the position of the center point of each of the protrusions 2a to 2n is indicated by a circle u centered on the center point for convenience.

The mode area Q (mode value of each area area) of each of the areas Ca to Cn is preferably in the following range.
When the average pitch P is less than 500 nm, the most frequent area Q in the AFM image measurement range of 10 μm × 10 μm is preferably 0.026 μm ^{2 to} 6.5 μm ² .
When the average pitch P of less than 1μm than 500 nm, the modal area Q is in the AFM image measurement range of 10 [mu] m × 10 [mu] m, it is preferably 0.65μm ² ~26μm ^2.
When the average pitch P is 1 μm or more, the mode area Q within the 50 μm × 50 μm AFM image measurement range is preferably 2.6 μm ^{2 to} 650 μm ² .
If the most frequent area Q is within the preferable range, the periodic structure is macroscopically a polycrystalline material having a random lattice orientation, so that when the surface plasmon is converted into propagating light and radiated on the metal surface, In addition, the emission angle of the radiated light becomes random with respect to the plane direction, and the emitted light extracted from the element can be suppressed from having anisotropy.

As shown in FIG. 3, the areas Ca to Cn have random areas, shapes, and lattice orientations.
Specifically, the degree of randomness of the area preferably satisfies the following condition.
First, an ellipse having the largest area circumscribing the boundary of one area is drawn, and the ellipse is represented by the following equation (1).
X ² / a ² + Y ² / b ² = 1 (1)

When the average pitch P is less than 500 nm, the standard deviation of πab within an AFM image measurement range of 10 μm × 10 μm is preferably 0.08 μm ² or more.
When the average pitch P is 500 nm or more and less than 1 μm, the standard deviation of πab in the AFM image measurement range of 10 μm × 10 μm is preferably 1.95 μm ² or more.
When the average pitch P is 1 μm or more, the standard deviation of πab in the AFM image measurement range of 50 μm × 50 μm is preferably 8.58 μm ² or more.
If the standard deviation of πab is within a preferable range, the emission angle of the surface plasmon radiated at a predetermined angle from the metal surface to the outside of the element in the planar direction is excellent, and the emitted light has anisotropy. Can be suppressed.

Specifically, the degree of randomness of the shape of each of the areas Ca to Cn is preferably such that the ratio of a to b and the standard deviation of a / b in equation (1) are 0.1 or more. Specifically, the randomness of the lattice orientation of each of the areas Ca to Cn preferably satisfies the following condition.
First, a straight line K0 connecting the center points of any two adjacent convex portions in an arbitrary area (I) is drawn. Next, one area (II) adjacent to the area (I) is selected, and three points connecting an arbitrary convex part in the area (II) and the center points of three convex parts adjacent to the convex part are selected. Are drawn. If the straight lines K1 to K3 have angles different from each other by three degrees or more with respect to the six straight lines rotated by 60 ° with respect to the straight line K0, the lattice orientation of the area (I) and the area (II) is Different.
Of the areas adjacent to the area (I), two or more, preferably three or more, and more preferably five or more, areas whose lattice orientations are different from the lattice orientation of the area (I) are present.

At this time, the convex portion is a polycrystalline structure in which the lattice directions are uniform in each of the areas Ca to Cn, but are not macroscopically uniform. The randomness of the macroscopic lattice orientation can be evaluated by the ratio between the maximum value and the minimum value of an FFT (Fast Fourier Transform) fundamental wave. The ratio between the maximum value and the minimum value of the FFT fundamental wave is obtained by obtaining an AFM image, obtaining a two-dimensional Fourier transform image, drawing a circle away from the origin by the wave number of the fundamental wave, and calculating the maximum amplitude on this circle. The point having the largest amplitude and the point having the smallest amplitude are extracted, and are obtained as a ratio of the amplitude.
When the ratio between the maximum value and the minimum value of the FFT fundamental wave is large, the lattice orientation of the convex portions is uniform, and it can be said that the structure has high single crystallinity when the convex portions are regarded as two-dimensional crystals. Conversely, when the ratio between the maximum value and the minimum value of the FFT fundamental wave is small, the lattice orientation of the projections is not uniform, and when the projections are regarded as a two-dimensional crystal, it can be said that they have a polycrystalline structure.

  The average aspect ratio of the plurality of projections 2a to 2n is 0.01 to 1, preferably 0.05 to 0.5. The average aspect ratio means an average height H of the projections 2a to 2n with respect to an average width D of the projections 2a to 2n. If the average aspect ratio in the mold 10 is 0.01 or less, an effect of extracting surface plasmons as radiant light cannot be sufficiently obtained in an organic light emitting diode manufactured using the mold 10. On the other hand, when the average aspect ratio is 1 or more, it is difficult to form the convex portion with a predetermined curved surface described later. In addition, it is difficult to transfer the shape using the mold 10 at the time of manufacturing the organic light emitting diode.

The average aspect ratio of the protrusions 2a to 2n is measured by AFM.
First, an AFM image is obtained for one randomly selected 25 μm ² (5 μm × 5 μm) region of the main surface 10 </ ^b > A of the mold 10. Next, a line is drawn in the diagonal direction of the obtained AFM image, and the height and width of each of the plurality of convex portions 2a to 2n intersecting with the line are measured. The height of the projection means the distance from the flat surface 1a to 1n to the top of the projection, and the width of the projection means the diameter of an inscribed circle centered on the center point of the projection when viewed in plan. . Then, an average value of the height and the width of the convex portion in this region is obtained. The same processing is performed for a total of 25 areas selected at random. The average values of the average values of the heights and widths of the obtained projections for each of the 25 regions are the average height and average width. The value obtained by dividing the average height by the average width is the average aspect ratio.

80% or more of the protrusions 2a to 2n are formed by a predetermined curved surface. The ratio of the convex portions having a predetermined curved surface among the plurality of convex portions is more preferably 90% or more, and further preferably 95% or more. The predetermined curved surface is defined as follows.

FIG. 4 is a schematic cross-sectional view in which the mold is cut at an arbitrary cross-section passing through the center point of the protrusion, and one of the protrusions is enlarged. First, an arbitrary point is selected as a first point p1 from the curved surface 2B constituting the convex portion 2n. A tangent plane to the first point p1 is defined as a first tangent plane t1. A point shifted from the first point p1 toward the center point 2An of the convex portion 2n by 1/10 of the average pitch is defined as a second point p2. Here, a shift of 1/10 of the average pitch means a distance L moved in parallel with the flat surface 1 from the first point p1 toward the center point 2An. A tangent plane to the second point p2 is defined as a second tangent plane t2. At this time, the inclination angle of the second tangent plane t2 with respect to the first tangent plane t1 is defined as θ.
In any part of the curved surface 2B of the convex portion 2n, when the inclination angle θ of the second tangent plane t2 with respect to the first tangent plane t1 satisfies the relationship of 60 ° or less, the convex portion 2n can be said to be a predetermined curved surface. . The inclination angle θ is preferably within 45 °, more preferably within 30 °.

  FIG. 5 is a schematic cross-sectional view when a mold according to one embodiment of the present invention is pressed against a surface of a laminate formed by coating. The laminate 20 includes a first layer 21, a second layer 22, and a third layer 23. When the mold 10 is pressed against the third layer 23 of the laminate 20, the protrusions 2 a to 2 n of the mold 10 are first pressed against the laminate 20. Therefore, a force F1 is applied to each layer constituting the laminate 20 from the tops of the protrusions 2a to 2n toward the outer periphery. By this force F1, the material constituting each layer is also supplied to the space between the plurality of convex portions 2a to 2n of the mold 10. As a result, each of the layers constituting the laminate 20 is deformed to have a shape corresponding to the mold 10.

The force F1 applied to each layer of the laminated body 20 spreads from the tops of the pressed projections 2a to 2n toward the outer periphery without stress concentration. This is because the convex portions 2a to 2n of the mold 10 are formed of a predetermined curved surface and have a gentle shape. If the force F1 is not stress concentrated, each of the first layer 21, the second layer 22, and the third layer 23 spreads uniformly in the in-plane direction. Therefore, it is possible to prevent the respective thicknesses from becoming extremely thin.
In addition, the material of each layer is sufficiently supplied along the predetermined curved surface 2B also to the boundary 3 between the plurality of protrusions 2a to 2n of the mold 10 which is a portion where a void is likely to be formed and the flat surface. That is, it is possible to prevent the occurrence of a gap in the boundary 3.

On the other hand, FIG. 6 is a schematic cross-sectional view when a mold having no predetermined curved surface is pressed against the surface of the laminate formed by coating. The protrusion 152n of the mold 15 shown in FIG. 6 has a corner 155 whose shape changes sharply. In the corner 155, tangent planes at two points sandwiching the corner 155 do not satisfy a predetermined curved surface relationship. Therefore, the force F2 applied to each layer constituting the stacked body 20 is not uniformly distributed along the shape of the convex portion 152n, but concentrates on the vicinity of the corner portion 155. As a result, each of the first layer 21, the second layer 22, and the third layer 23 cannot uniformly spread in the in-plane direction. Therefore, each layer may be cut in the vicinity of the corner 155, or the layer thickness may be extremely thin.
In addition, a sufficient amount of material cannot be supplied to the boundary 153 between the projection 152n and the flat surface, and a gap is likely to be generated.

The layers constituting the stacked body 20 correspond to any layers constituting the organic light emitting diode. When a part of each layer constituting the organic light emitting diode is cut, there is a problem that the organic light emitting diode does not emit light or does not exhibit sufficient light emitting characteristics in the cut part. That is, by using the mold 10 according to the present embodiment, it is possible to avoid the problem that the organic light emitting diode does not emit light or does not exhibit sufficient light emission characteristics.

Returning to FIG. 5, it is preferable that the boundary 3 is also gentle in order to avoid generation of a gap between the mold 10 and the laminate 20. That is, in any of the connection portions between the protrusions 2a to 2n and the flat surface, the inclination angle of the tangent plane at a point shifted by 1/10 of the average pitch from any one point with respect to the tangent plane at any one point is within 60 °. It is preferable to satisfy the following relationship.

FIG. 7 is a schematic cross-sectional view when a mold according to another embodiment of the present invention is pressed against the surface of a laminate formed by coating. The mold 30 shown in FIG. 7 has a plurality of protrusions and a flat surface 31, and a boundary 33 between the plurality of protrusions and the flat surface 31 is connected by a predetermined curved surface. That is, even in the connection portion between the flat surface 31 and the convex portion 32n, the relationship that the inclination angle of the tangent plane at a point shifted by 1/10 of the average pitch from any one point with respect to the tangent plane at any one point is within 60 °. Fulfill. That is, the boundary portion 33 becomes gentle.

When the mold 30 shown in FIG. 7 is pressed against the stacked body 20, neither the force F1 applied from the top of the convex portion 32n toward the outer peripheral portion nor the force F3 applied near the boundary portion 33 is stress concentrated. Therefore, the material forming each layer spreads smoothly along the main surface of the mold 30. As a result, it is possible to avoid generating a gap between the mold 10 and the laminate 20 and to make the thickness of each layer of the laminate 20 uniform in the in-plane direction.

In the mold 30, to the smooth flat surface 31 and a plurality of convex portions of the boundary portion 33, the predetermined curved portion constituting a convex portion has at least one or more curved portion p _in, inflection It can be realized by satisfying both the curved surface connecting the first inflection p1 _in the flat surface 31 of the flattest surface 31 side of the part p _in is convex downward. Curved portion p _in is a collection of inflection points in the cross section of the convex portion, the portion to be changed from a convex curved surface on the convex curved surface below, or a convex curved surface on the convex curved surface below It is the part that changes. The inflection part pin is formed in a line shape along the convex part 32n _in a plan view.

The closest distance from the first inflection portion p1 _in to the flat surface 31 is preferably at least 1/10, more preferably at least 1/5 of the average pitch P of the plurality of projections. The closest distance is the distance of the narrowest part of the width between the first inflection part _p11n and the flat surface 31 when the convex part 32n is viewed in plan. If the closest distance from the first inflection portion p1 _in to the flat surface 31 is equal to or more than 1/10 of the average pitch P of the plurality of convex portions, the inclination of the boundary portion 33 can be made gentler.

Further, when the boundary portion 33 of the mold 30 is made gentle, when a layer is formed by a vacuum film forming method on an object to be transferred manufactured using the mold 30, a layer formed by the vacuum film forming method is coated. Reflectivity reflecting the shape of the transcript is enhanced.
FIG. 8 is a schematic cross-sectional view when a layer is formed on the transferred material shown in FIG. 7 by a vacuum film forming method. In the mold 30 shown in FIG. 7, the boundary 33 between the flat surface 31 and the projection 32n is gentle. Therefore, the boundary 23A of the curved surface 20A formed on the outermost surface of the laminate 20 using the mold 30 is also gentle. In general, in the portion where the shape changes sharply, the throwing power of the film-forming particles during vacuum film-forming often changes greatly. On the other hand, if the shape of the curved surface 20A including the boundary portion 23A is gentle, the throwing power of the film-forming particles does not largely change, and a uniform layer can be formed. In the transcript shown in FIG. 8, the main surface (outermost surface) 20A of the laminate 20 is gentle. Therefore, the outer surface 26B of the layer 26 formed by vacuum deposition can sufficiently reflect the shape of the main surface 20A. Here, “sufficiently reflected” does not need to completely reflect the shape formed in the stamper process. The average pitch of the projections forming the outer surface 26B of the vacuum-formed layer 26 is within ± 10% of the average pitch of the projections forming the main surface 20A, and the vacuum deposition is performed. If the average height of the projections forming the outer surface 26B of the layer 26 is within ± 10% of the average height of the projections forming the main surface 20A, the vacuum-formed layer 26 It can be said that the outer surface 26B sufficiently reflects the shape of the main surface 20A. The above-described method for measuring the average pitch P can be applied to the measurement of the average pitch here. The above-described method for measuring the average height H can be applied to the measurement of the average height.
When the vacuum-formed layer 26 is an electrode, the outer surface 26B does not need to have a shape that sufficiently reflects the shape of the main surface 20A. Even in this case, since the main surface 20A is gentle, the thickness of the layer 26 is not reduced or cut.
As a method of confirming the shapes of the curved surface 22B and the outer surface 26B, there are a cross-sectional observation using a scanning electron microscope (SEM) or a transmission electron microscope (TEM), and a three-dimensional method after removing a layer covering the observation surface. A method of observing with an electron microscope or an AFM is used.

Returning to FIG. 1, the area ratio of the flat surfaces 1a to 1n in the main surface 10A is preferably 5 to 50%, more preferably 5 to 30%. When the area ratio of the flat surfaces 1a to 1n in the main surface 10A is 5% or more, the aspect ratio of unevenness for extracting surface plasmons can be reduced in an organic light emitting diode manufactured using this mold. On the other hand, if the area ratio of the flat surfaces 1a to 1n in the main surface 10A is 50% or less, it is possible to prevent surface plasmons from being captured on the flat surface in the organic light emitting diode manufactured using this mold.

FIG. 9 is a schematic cross-sectional view of the mold according to one embodiment of the present invention, which is cut by a plane connecting centers of adjacent protrusions. More specifically, FIG. 2 is a cross-sectional view cut along a plane connecting the center points of adjacent convex portions in FIG. 1. The dotted line in FIG. 9 is an approximate curve of the projections 2a to 2n. The approximate curve can be obtained by approximating the center points 2Aa to 2An of the protrusions 2a to 2n to the vertices by a normal distribution. The boundary between the protrusions 2a to 2n and the ridge 4 is an approximate curve. Adjacent convex portions are connected by a ridge line portion 4. The center points 2Aa to 2An side of the approximate curve are the convex parts 2a to 2n, and the opposite side is the ridge line part 4.

It is preferable that the connecting portion between the ridge line portion 4 and the convex portions 2a to 2n and the connecting portion between the ridge line portion 4 and the flat surfaces 1a to 1n are connected so as to satisfy a predetermined curved surface condition. By connecting these connecting portions so as to satisfy the condition of the predetermined curved surface, the force generated when the mold 10 is pressed against the laminate can be more uniformly dispersed. That is, it is possible to suppress the layer forming the laminate that presses the mold 10 from being cut.

Further, as shown in FIG. 9, it is preferable that at least a part of the ridge line portion 4 exists on the flat surface 1n side from the convex portion 2n connecting the ridge line portion 4. That is, it is preferable that the height h of the portion of the ridge line portion 4 closest to the flat surface 1n from the flat surface 1n is lower than the height H of the convex portion 2n connecting the ridge line portion 4 from the flat surface 1n.

FIG. 13 is a plan view of a main part of the mold according to the present embodiment viewed from a direction perpendicular to a flat surface. When the height h of the ridge line portion 4 is lower than the height H of the convex portion 2n, when the mold is pressed against the transferred material, the air interposed between the mold and the transferred material via the portion is reduced. It is removed (arrow in FIG. 13). That is, uniform transfer can be performed by preventing air from being mixed into the transfer target.

In addition, as shown in FIG. 13, in plan view from a direction perpendicular to the flat surface 1n, the tops of the plurality of protrusions 2a to 2n are located at the vertices of a hexagon forming a honeycomb lattice (hexagonal lattice). In this case, the spread of the resin and the like when the mold is pressed against the transfer object becomes uniform, and the pressure can be evenly applied to the transfer object. If the pressure can be applied uniformly, for example, even if the transfer object is a thin layer, it is possible to avoid the layer being cut or the layer thickness being extremely thin.

Further, the height h from the flat surface 1n of the portion of the ridge line portion 4 closest to the flat surface 1n shown in FIG. 9 is 50 with respect to the height H of the convex portion 2n connecting the ridge line portion 4 from the flat surface 1n. % To 90%, more preferably 60 to 85%. If the height h of the ridge line portion 4 is too low, the strength of the mold decreases, and if the height h of the ridge line portion 4 is too high, the escape path of air decreases.

Up to this point, one embodiment of the present invention has been described using the mold 10 of FIG. 1 as an example, but the shape of the mold is not limited to this configuration.
FIG. 10 is a schematic perspective view of a mold according to another embodiment of the present invention. The mold 40 shown in FIG. 10 is different from the above-described mold 10 and the like in that the protrusions 42 a to 42 n are arranged apart from each other and are formed of one flat surface 41.

  In addition, for example, a configuration as shown in FIG. 11 may be used. FIG. 11 is a schematic perspective view of a mold according to another embodiment of the present invention. As shown in FIG. 11, the mold 50 has a plurality of convex portions 52a to 52n and a plurality of flat surfaces 51a to 51n. In the mold 10 shown in FIG. 1 and the mold 50 shown in FIG. 11, the positional relationship between the convex portion and the flat surface is reversed. That is, in the mold 50, the plurality of protrusions 52a to 52n are arranged in a region surrounded by the nearest flat surface among the plurality of flat surfaces 51a to 51n. In FIG. 11, a hexagon in plan view is drawn when connecting the center points of the nearest flat surfaces, and a convex portion is provided in the central region thereof. Even when the positional relationship between the plurality of protrusions 52a to 52n and the flat surfaces 51a to 51n is reversed as in the case of the mold 50, since the protrusions 52a to 52n are formed by predetermined curved surfaces, the mold 50 is In the stamping step of pressing, it is possible to prevent the layers constituting the laminate from being cut.

  A mold according to one embodiment of the present invention has a convex portion having a predetermined curved surface. Therefore, the organic light-emitting diode manufactured by using the mold 10 has no thin layer portion or no layer portion, and can efficiently extract surface plasmons.

"Mold manufacturing method"
The mold can be formed using electron beam lithography, mechanical cutting, laser lithography, laser thermal lithography, interference exposure, reduction exposure, anodization of aluminum, a method using a particle mask, or the like. In particular, the mold is preferably manufactured using a method using a particle mask. The method using a particle mask is a method in which a single particle layer film is formed on a flat surface of a mold base material as an etching mask, and then an etching process is performed. In the method using the particle mask, the base material immediately below the particles is not etched and becomes a projection.

  Hereinafter, a specific example of the method using the particle mask will be described. FIG. 14 is a diagram schematically showing a method of manufacturing a mold.

  First, a single particle film etching mask 62 composed of many particles M is formed on a base 61 (FIG. 14A). As a method for forming the single-particle film etching mask 62 on the substrate 61, for example, a method utilizing the concept of the so-called LB method (Langmuir-Blodgett method) can be used. The method for forming the single-particle film etching mask 62 includes, specifically, a dropping step of dropping a dispersion liquid in which particles are dispersed in a solvent onto a liquid surface in a water tank, and a single particle comprising particles by volatilizing the solvent. The method includes a single particle film forming step of forming the film F and a transfer step of transferring the single particle film F onto the substrate. Hereinafter, each step will be specifically described.

(Drip process and single particle film formation process)
First, a dispersion liquid is prepared by adding particles having a hydrophobic surface to a hydrophobic organic solvent including at least one of highly volatile solvents such as chloroform, methanol, ethanol, and methyl ethyl ketone. Further, as shown in FIG. 15, a water tank (trough) V is prepared, and water W is charged as a liquid (hereinafter, sometimes referred to as lower layer water) for spreading particles on the liquid surface.
Then, the dispersion liquid is dropped on the liquid surface of the lower layer water (dropping step). Then, the solvent as the dispersion medium is volatilized, and the particles are spread in a single layer on the liquid surface of the lower layer water, thereby forming a two-dimensional close-packed single particle film F (single particle film forming step). .

  As described above, when hydrophobic particles are selected, it is necessary to select a hydrophobic solvent. On the other hand, in that case, the lower layer water needs to be hydrophilic, and usually water is used as described above. By such a combination, as described later, the self-organization of the particles progresses, and a two-dimensional close-packed single particle film F is formed. However, hydrophilic particles may be selected as the particles and the solvent. In this case, a hydrophobic liquid is selected as the lower layer water.

(Transition process)
As shown in FIG. 15, the single-particle film F formed on the liquid surface in the single-particle film forming step is then transferred in a single-layer state onto the substrate 61 to be etched (transfer step). The base 61 may be flat, or may partially or entirely include a non-planar shape such as a curved surface, an inclination, and a step.

The single-particle film F can cover the surface of the base 61 while maintaining the two-dimensional close-packed state even if the base 61 is not flat. The specific method of transferring the single-particle film F onto the substrate 61 is not particularly limited. For example, as a first method, while keeping the hydrophobic substrate 61 substantially in parallel with the single-particle film F, the substrate 61 is lowered from above and brought into contact with the single-particle film F, and the hydrophobic single-particle film is both hydrophobic. The single-particle film F may be transferred to the base 61 by the affinity between F and the base 61 and transferred. In addition, as a second method, before forming the single-particle film F, the substrate 61 is arranged in a substantially horizontal direction in the lower water of the water tank in advance, and after the single-particle film F is formed on the liquid surface, the liquid surface is changed. The single-particle film F may be transferred onto the substrate 61 by gradually lowering it. According to these methods, the single particle film F can be transferred onto the base 61 without using a special device. It is preferable to employ the so-called LB trough method because even a single-particle film F having a larger area can be easily transferred onto the substrate 1 while maintaining its secondary close-packed state.

Through this transition step, the plurality of particles M are arranged in a substantially single layer on the flat surface 61a, which is one surface of the base 61. That is, the single particle film F of the particles M is formed on the flat surface 61a.

(Etching process)
The single-particle film F thus formed functions as a single-particle etching mask 62. The substrate 61 provided with the single-particle etching mask 62 on one surface is subjected to gas phase etching to process the surface (etching step).

Specifically, when the vapor phase etching is started, first, as shown in FIG. 14B, the etching gas passes through the gaps between the particles M forming the etching mask 62 and reaches the surface of the base 61, and A groove is formed in the portion. Then, the cylinder 63 appears at a position corresponding to each particle M. A groove 61m is formed between the columns 63. The groove 61m is formed at the center of three particles M arranged on an equilateral triangle by close packing. Therefore, the groove 61m is located at the vertex of a regular hexagon about the cylinder 63.

The particles M constituting the single-particle film etching mask 62 are not particularly limited, but for example, gold particles, colloidal silica particles, or the like can be used. As the etching gas, a commonly used etching gas can be used. For example, Ar, SF ₆ , F ₂ , CF ₄ , C ₄ F ₈ , C ₅ F ₈ , C ₂ F ₆ , C ₃ F ₆ , C ₄ F ₆ , CHF ₃ , CH ₂ F ₂ , CH ₃ F, C ₃ F ₈ , Cl ₂ , CCl ₄ , SiCl ₄ , BCl ₂ , BCl ₃ , BC ₂ , Br ₂ , Br ₃ , HBr, CBrF ₃ , HCl, CH ₄ , NH ₃ , O ₂ , H ₂ , N ₂ , CO, CO _{2 and the} like can be used.

These particles M and etching gas can be changed according to the substrate 61 to be etched. For example, when gold particles are selected as the particles M constituting the single-particle film etching mask 62 and a glass substrate is selected as the base 61 and they are combined with each other, the etching gas is reactive with glass such as CF ₄ and CHF _3. If a glass substrate is used, the etching rate of the gold particles becomes relatively slow, and the glass substrate is selectively etched.

Various shapes of dies as shown in FIGS. 1, 10 and 11 can obtain desired shapes by changing dry etching conditions. Further, in order to make the surface shape of the convex portion more gentle, wet etching may be used together.
The dry etching conditions include the material of the particles constituting the particle mask, the material of the original plate, the type of etching gas, the bias power, the source power, the flow rate and pressure of the gas, the etching time, and the like. The flat surface can be obtained by increasing the initial flow rate of the etching gas and gradually reducing the flow rate. In the case where a ridge portion is left as in the mold 10 shown in FIG. 1, it can be obtained by increasing the hardness of the particles used for the particle mask.

The average pitch and the like of the convex portions can be freely changed by changing the particle diameter of the particles used. When a non-periodic structure is formed using a particle monolayer film, it can be produced by using a plurality of particles having different particle diameters.

(Odd number of transfer steps)
Next, the substrate 61 shown in FIG. 14B is transferred an odd number of times. The transfer body 71 shown in FIG. Specifically, first, the produced base 61 is transferred with a resin. The surface of the obtained resin transfer product is coated with metal plating such as Ni by electroforming or the like. The coating of the metal plating increases the hardness of the transfer body 71, and enables shape adjustment and the like described later.

The top of the column 63 of the base 61 is a flat surface because it is covered with the particles M. Therefore, a flat surface 71n is formed in the transfer body 71 at a position corresponding to the column 63 of the base 61. In the transfer body 71, a protrusion 72n is formed at a position corresponding to the groove 61m of the base 61. Therefore, the convex portion 72 is located at a vertex of a regular hexagon with the flat surface 71n at the center. That is, a shape corresponding to FIG. 1 is obtained.

(Shape adjustment process)
However, a predetermined curved surface may not be formed on the surface of the transfer body 71 in some cases. For example, a corner 72a may be formed at the top of the projection 72n. The corner 72a is a portion that does not satisfy a predetermined curved surface. Therefore, the corner 72a is removed, and the outer surface of the projection 72n is formed into a predetermined curved surface. Further etching may be performed by wet etching or dry etching. Hereinafter, the case of dry etching will be specifically described.

In order to remove the corners 72a, as shown in FIG. 14D, the transfer body 71 is irradiated with plasma P generated by a plasma etching apparatus to perform physical etching.

Physical etching is different from reactive etching used in the etching process. In the reactive etching, the chemical species converted into plasma reacts with the transfer body 71, and the etching proceeds. On the other hand, in the physical etching, etching is performed by the physical force of the chemical species converted into plasma colliding with the transfer body 71. Therefore, in the physical etching, there is a variation in the etching rate between a portion where the probability of collision with the chemical species converted into plasma is high and a portion where the probability is low, and the etching has anisotropy as compared with the reactive etching. Physical etching is similar to ashing.

In a plasma etching apparatus, a chemical species that is converted into plasma between an upper electrode and a lower electrode is used. Specifically, the transfer member 71 is electrically connected to the lower potential lower electrode and the transfer member 71 is charged. The chemical species converted into plasma between the upper electrode and the lower electrode is attracted to the low-potential transfer member 71 and collides against the transfer member 71 at high speed.

At this time, if the charged transfer body 71 has a sharp portion such as the corner 72a, the charge tends to concentrate on that portion. Therefore, the plasmated chemical species are attracted to sharp points. That is, the probability that the sharp portion collides with the chemical species that has been turned into plasma than the other portions increases. If the probability of collision with the plasmatized chemical species increases, that part is etched faster than the other parts. That is, the corner 72a of the convex 72 is gradually cut to form the convex 2n having a predetermined curved surface (FIG. 14E).

  As an etching gas used for physical etching, for example, a rare gas such as argon, oxygen, or the like can be used. These gases have poor reactivity and physical etching proceeds.

Further, a reactive etching gas may be used as an etching gas used for physical etching. For example, a reactive gas such as CF ₄ or CHF ₃ can be used. In this case, the etching conditions are adjusted so that the etching due to physical collision is more remarkable than the chemical reactivity of the ion species. For example, the etching conditions are adjusted so that the potential difference between the upper electrode and the lower electrode increases. When the potential difference between the upper electrode and the lower electrode increases, the collision speed of the plasma-generated chemical species increases, and the effect of the physical etching becomes more remarkable than the effect of the reactive etching.

The physical etching is preferably performed using argon or oxygen under low pressure and high bias. Specific conditions differ depending on the apparatus, and cannot be unconditionally determined. For example, when dry etching is performed by using inductively coupled plasma (ICP), a pressure of 0.5 to 1.0 Pa and a pressure of 0.5 to 1.0. It is preferable to apply a bias of 5 W / cm ² . Even when other dry etching gas is used, it is preferable that the processing time is shortened, without greatly departing from the above range. This is because the etching speed is high and the corner 62a may be etched more than expected.

Up to this point, only the corner 72a has been described, but for example, a sharp portion may also be formed at the ridge (see FIGS. 1 and 9) between the adjacent protrusions 72n. Also in this case, the sharp portion in the ridge line is removed by the physical etching simultaneously with the corner 72a.

(Replication process)
The mold produced by the above method may be used directly as a mold, or a duplicate produced using the produced mold as an original may be used as a mold actually used. The replica can be produced by transferring the produced mold even number of times. Specifically, first, the prepared mold is transferred with a resin. The surface of the obtained transfer body is coated with metal plating such as Ni by electroforming or the like an odd number of times. By coating with the metal plating, the hardness of the transfer body is increased an odd number of times, and further transfer can be performed. Then, the transcript is further transferred an odd number of times to produce an even number of transcripts. The even-numbered transfer body has the same shape as the prepared mold. Finally, the mold is duplicated by plating a metal such as Ni on the surface of the transfer body even number of times by electroforming or the like.

  In addition, the mold 30 shown in FIG. 7 in which the boundary portions 33 between the plurality of convex portions 32n and the flat surface 31 are also connected by a predetermined curved surface can be manufactured by the following method.

For example, as a first method, there is a method of performing physical etching between the above-described etching step and the odd-numbered transfer steps. By performing physical etching between the etching step and the transfer step for an odd number of times, the top of the column 63 becomes smooth, and the shape of the concave portion of the transfer body 71n becomes smooth.

  As another method, there is a method of performing physical etching in a transfer process in a replication process. By performing the physical etching, the shape of the portion that has become the convex after the transfer can be made gentle.

"Organic light emitting diode"
FIG. 12 is a schematic cross-sectional view of the organic light-emitting diode element 100 according to one embodiment of the present invention. The organic light emitting diode element 100 includes a base 110, a first electrode 120, an organic semiconductor layer 130 including a light emitting layer 133, and a second electrode 140 in this order.
The organic semiconductor layer 130 illustrated in FIG. 12 includes a hole injection layer 131 and a hole transport layer 132 between the first electrode 120 and the light emitting layer 133 in addition to the light emitting layer 133. An electron transport layer 134 and an electron injection layer 135 are provided between them. Each of the hole injection layer 131, the hole transport layer 132, the electron transport layer 134, and the electron injection layer 135 does not necessarily have to be provided, and may be omitted. The organic light emitting diode element 100 of the present invention may further include other layers as long as the effects of the present invention are not impaired.

In the organic light emitting diode, the first electrode 120 and the second electrode 140 apply a voltage to the organic semiconductor layer 130. When a voltage is applied between the first electrode 120 and the second electrode 140, electrons and holes are injected into the light emitting layer 133, and these are combined to generate light. The generated light is directly transmitted through the first electrode 120 and extracted to the outside of the device, or is reflected once by the second electrode 140 and extracted to the outside of the device.

The second electrode 140 has a two-dimensional structure in which a plurality of protrusions 142a to 142n are two-dimensionally arranged on a surface 140A on the light emitting layer 133 side. The two-dimensional structure may be periodic or aperiodic, similar to the mold described above.
The average pitch of the plurality of protrusions 142a to 142n is 50 nm to 5 μm, and preferably 50 nm to 500 nm. The average pitch can be determined in the same manner as the average pitch in the mold. If the average pitch of the projections 142a to 142n is within this range, the energy captured as surface plasmons on the surface 140A of the second electrode, which is a metal electrode, can be efficiently radiated and extracted as light.

The average aspect ratio of the plurality of protrusions 142a to 142n is 0.01 to 1, and preferably 0.05 to 0.5. The average aspect ratio can be determined in the same manner as the average aspect ratio in the mold. If the average aspect ratio of the projections 142a to 142n on the surface on the light emitting layer side of the second electrode 140 is within this range, the energy captured as surface plasmons on the surface 140A of the second electrode, which is a metal electrode, can be efficiently used. Radiated out and can be extracted as light.

The capture of surface plasmons occurs in the following process. When light is emitted from the light-emitting molecule in the light-emitting layer 133, near-field light is generated very near the light-emitting point. Since the distance between the light emitting layer 133 and the second electrode 140 is very short, near-field light is converted into energy of a propagation type surface plasmon on the surface of the second electrode 140.
The propagation type surface plasmon on a metal surface is a compression wave of free electrons generated by an incident electromagnetic wave (such as near-field light) accompanied by a surface electromagnetic field. In the case of a surface plasmon existing on a flat metal surface, the dispersion curve of the surface plasmon does not intersect with the dispersion line of light (space propagation light). Therefore, the energy of surface plasmons cannot be extracted as light. On the other hand, if the metal surface has the two-dimensional periodic structure, the dispersion curve of the surface plasmon diffracted by the two-dimensional periodic structure intersects the dispersion curve of the spatially propagating light. As a result, the energy of the surface plasmon can be taken out of the element as radiation light.
As described above, when the two-dimensional periodic structure is provided, light energy lost as surface plasmons can be extracted. The extracted energy is radiated from the surface of the second electrode 140 as spatially propagated light. At this time, the light radiated from the second electrode 140 has high directivity, and most of the light is directed to the extraction surface. Therefore, high-intensity light is emitted from the extraction surface, and the extraction efficiency is improved.

80% or more of the plurality of protrusions 142a to 142n have a predetermined curved surface. The predetermined curved surface is defined similarly to the predetermined curved surface in the mold.

On the surface 140A of the second electrode, a flat surface 141 is formed between the plurality of protrusions 142a to 142n. The area ratio of the flat surface 141 is preferably 5% to 50%, more preferably 5% to 30%. When the area ratio of the flat surface 141 on the surface 140A of the second electrode is 5% or more, the aspect ratio of unevenness for extracting surface plasmons can be reduced. On the other hand, if the area ratio of the flat surface 141 on the surface 140A of the second electrode is 50% or less, the surface plasmon captured on the surface 140A of the second electrode can be efficiently converted into light.

The second electrode 140 is preferably made of a material whose absolute value of the real part of the complex permittivity has a large negative value, and it is preferable to select a metal material having a high plasma frequency which is advantageous for extracting surface plasmons. Examples of such a material include a simple substance such as gold, silver, copper, aluminum, and magnesium, an alloy of gold and silver, and an alloy of silver and copper. Considering the light extraction of the organic light emitting diode, a metal material having a resonance frequency over the entire visible light region is preferable, and silver or aluminum is particularly preferable. The second electrode 140 may have a stacked structure of two or more layers.
The thickness of the second electrode 140 is not particularly limited. For example, it is 20 to 2000 nm, preferably 50 to 500 nm. If the thickness is less than 20 nm, the reflectance decreases and the front luminance decreases. If the thickness is more than 500 nm, damage due to heat and radiation during film formation and mechanical damage due to film stress accumulate in a layer made of an organic material such as the organic light emitting layer 133.

  The organic semiconductor layer 130 is made of an organic material. In FIG. 12, irregularities are formed at the interface between the light emitting layer 133 and the electron transport layer 134 of the organic semiconductor layer 130 and at the interface between the electron transport layer 134 and the electron injection layer 135. This uneven shape is a shape opposite to the main surface 10 </ b> A of the mold 10. This uneven shape does not necessarily need to be formed at the interface between the light emitting layer 133 and the electron transport layer 134 of the organic semiconductor layer 130 and at the interface between the electron transport layer 134 and the electron injection layer 135. Although details will be described later in a method of manufacturing the organic light emitting diode, the uneven shape may be formed on the surface of any of the layers constituting the organic semiconductor layer on the second electrode 140 side. The layer closer to the second electrode 140 than the layer in which the uneven shape is formed has a shape that reflects the uneven shape.

The light emitting layer 133 is made of an organic light emitting material. Examples of the organic light-emitting material include Tris [1-phenylisoquinoline-C2, N] iridium (III) (Ir (piq) 3), 1,4-bis [4- (N, N-diphenylaminostylylbenzene)] (DPAVB), Dye compounds such as Bis [2- (2-benzoxazolyl) phenolato] Zinc (II) (ZnPBO) are exemplified. Further, a substance obtained by doping a fluorescent dye compound or a phosphorescent material into another substance (host material) may be used. In this case, examples of the host material include a hole transporting material and an electron transporting material.

Organic materials are generally used as materials for forming the hole injection layer 131, the hole transport layer 132, the electron transport layer 134, and the electron injection layer 135, respectively.
For example, as a material (hole injection material) constituting the hole injection layer 131, for example, a compound such as 4,4 ′, 4 ″ -tris (N, N-2-naphthylphenylamino) triphenylamine (2-TNATA) and the like can be mentioned. .
As a material (hole transport material) constituting the hole transport layer 132, for example, N, N'-diphenyl-N, N'-bis (1-naphthyl)-(1,1'-biphenyl) -4,4 ' -Diamine (NPD), copper phthalocyanine (CuPc), and aromatic amine compounds such as N, N'-Diphenyl-N, N'-di (m-tolyl) benzidine (TPD).

As a material (electron transport material) forming the electron transport layer 134 and a material (electron injection material) forming the electron injection layer 135, for example, 2,5-Bis (1-naphthyl) -1,3,4-oxadiazole Oxadiol-based compounds such as (BND), 2- (4-tert-butylphenyl) -5- (4-biphenylyl) -1,3,4-oxadiazole (PBD), Tris (8-quinolinolinato) aluminium (Alq), etc. And the like.
The overall thickness of the organic semiconductor layer including the light emitting layer 133 is usually 30 to 500 nm.

For the first electrode 120, a transparent conductor that transmits visible light is used.
The transparent conductor constituting the first electrode 120 is not particularly limited, and a known transparent conductive material can be used. For example, indium-tin oxide (Indium Tin Oxide (ITO)), indium-zinc oxide (Indium Zinc Oxide (IZO)), zinc oxide (Zinc Oxide (ZnO)), zinc-tin oxide (Zinc Tin Oxide (ZTO)) )). The thickness of the first electrode 120 is usually 50 to 500 nm.

As the base 110, a transparent body that transmits visible light is used. The material constituting the base 110 may be an inorganic material, an organic material, or a combination thereof. Examples of the inorganic material include various glasses such as quartz glass, non-alkali glass, and white plate glass, and transparent inorganic minerals such as mica. Examples of the organic material include a resin film such as a cycloolefin-based film and a polyester-based film, and a fiber-reinforced plastic material in which fine fibers such as cellulose nanofibers are mixed in the resin film.
In general, a substrate having a high visible light transmittance is used depending on the use. The transmittance is 70% or more, preferably 80% or more, and more preferably 90% or more, without giving a bias to the spectrum in the visible light range (wavelength 380 nm to 800 nm).

The thickness of each layer constituting the organic light emitting diode 100 can be measured by a spectroscopic ellipsometer, a contact type step meter, an AFM, or the like.

"Manufacturing method of organic light emitting diode"
According to one embodiment of the present invention, there is provided a method for manufacturing an organic light-emitting diode, comprising: an organic semiconductor layer including a light-emitting layer; and a second electrode on a surface of a substrate with an electrode having a transparent first electrode formed on the substrate. Is a method of manufacturing an organic light emitting diode formed by a coating step and a subsequent vacuum film forming step. Between the coating process and the vacuum film forming process, the above-mentioned mold is pressed against the outermost surface of the coating layer formed in the coating process, and a shape inverted from the shape of the main surface of the mold is formed on the outermost surface of the coating layer. A stamper step of

<Preparation process of substrate with electrode>
The substrate with electrodes forms a transparent first electrode on a transparent substrate. As the base and the first electrode, those described above can be used.
As a method of forming the first electrode on the base, a known method can be used. For example, a transparent electrode material such as ITO can be formed on a substrate by sputtering. Alternatively, a commercially available substrate with electrodes may be purchased.

<Coating process>
In the coating step, some or all of the layers constituting the organic semiconductor layer are formed by coating. In general, in the coating process, it is necessary to select a solvent for the coating solution so as not to attack each layer already formed in the previous process. Selection becomes difficult. Therefore, in the coating step, it is preferable to form up to the light emitting layer among the layers constituting the organic semiconductor layer.

As a coating method, a known method can be used, and for example, spin coating, bar coating, slit coating, die coating, spray coating, an inkjet method, or the like can be used. The coating method does not require vacuuming the environment at the time of lamination, and does not require large-scale equipment. Further, since the time for evacuation or the like is not required, the throughput for manufacturing the organic light emitting diode can be improved.

<Stamper process>
The stamper step is a method of forming a concavo-convex shape by a so-called imprint method. When a mold is pressed against the application layer formed in the application step, the application liquid constituting the application layer follows the shape of the mold. Since the coating liquid has a viscosity that can maintain the shape, the shape is maintained even after the mold is removed.
Also, even after the coating liquid is dried and evaporated, if the material forming the film formation layer has a glass transition point, by pressing the mold while heating the film formation layer to a temperature equal to or higher than the glass transition point. It is possible to give shape.

In the stamper step, the mold according to one embodiment of the present invention is pressed against the outermost layer of the coating layer formed in the coating step. The outermost layer is the last layer formed in the coating step, and is the layer farthest from the base when the coating step is completed. For example, when the light emitting layer 133 in FIG. 12 is formed by coating, the mold is pressed against the surface of the light emitting layer 133 on the side of the second electrode 140 to transfer the inverted shape of the mold.
As described above, the mold according to one embodiment of the present invention has a plurality of convex portions having a predetermined curved surface and a flat surface. Therefore, when a mold is pressed against the light emitting layer 133, the force applied to the light emitting layer 133 along a predetermined curved surface is dispersed. As a result, it is possible to avoid that the thickness of the light emitting layer 133 is extremely thin, that the light emitting layer 133 is cut off, and the like.

<Vacuum deposition process>
In the vacuum film forming step, a layer which is not formed in the coating step and the second electrode among the layers constituting the organic semiconductor layer are formed by a vacuum film forming method.
As the vacuum film formation method, a vacuum evaporation method, a sputtering method, a CVD (chemical vapor deposition) method, or the like can be used. In order to reduce damage to the organic layer, it is preferable to use a vacuum evaporation method as a vacuum film formation method.

  The vacuum film forming method has a higher reflectivity reflecting the shape of the base than the coating method. Therefore, the shape of the convex portion and the flat surface formed on the outermost layer of the coating layer in the stamper process is reflected on the layer laminated on the outermost layer of the coating layer.

In the recess formed in the outermost layer of the coating layer by pressing the mold, it is preferable that the recess and the flat surface are connected by a predetermined curved surface. That is, it is preferable that the boundary between the concave portion and the flat surface is gentle. Non-uniform thickness of the layer formed by vacuum film formation can be further suppressed.

By forming the above-described concave portion and flat surface in the outermost layer of the coating layer, a shape that is inverted from the outermost layer of the coating layer is formed on the surface of the second electrode on the light emitting layer side, as shown in FIG. This shape reflects the shape of the mold pressed in the stamper process.

Since the method for manufacturing an organic light-emitting diode according to one embodiment of the present invention includes a stamper step using a mold having a predetermined shape, desired irregularities can be easily formed on the light-emitting layer side of the second electrode. . The organic light emitting diode manufactured by this method can take out surface plasmons and obtain high light emitting characteristics.

  10, 30, 40, 50: mold, 10A: main surface, 1a to 1n, 41, 51a to 51n: flat surface, 2a to 2n, 32n, 42a to 42n, 52a to 52n: convex portion, 2Aa to 2An: Center point, 1Aa to 1An: center point, 2B: curved surface, 20: laminate, 21: first layer, 22: second layer, 23: third layer, 26: layer, 26B: outer surface, 3, 33: boundary, 4: ridge, 100: organic light emitting diode, 110: base, 120: first electrode, 130: organic semiconductor layer, 131: hole injection layer, 132: hole transport layer, 133: light emitting layer , 134: electron transport layer, 135: electron injection layer, 140: second electrode, 142a to 142n: convex portion

Claims (3)

An organic semiconductor layer including a light-emitting layer and a second electrode are formed on a surface of the substrate with an electrode having a transparent first electrode on the surface where the first electrode is formed, by a coating step and a subsequent vacuum film forming step. A method for manufacturing an organic light emitting diode to be formed,
Between the vacuum film forming step and the coating step, pressing a mold on the outermost surface of the coating layer formed in the coating step, the outermost surface of the coating layer the reverse shape of the shape of the main surface of the mold have a stamper forming a,
The mold has a flat surface on a main surface and a plurality of convex portions,
The average pitch of the plurality of protrusions is 50 nm to 5 μm, the average aspect ratio of the plurality of protrusions is 0.01 to 1,
80% or more of the plurality of protrusions have a predetermined curved surface,
When the predetermined curved surface is an arbitrary point on the predetermined curved surface as a first point and a point shifted from the first point by 1/10 of the average pitch is a second point,
A method of manufacturing an organic light emitting diode , wherein an inclination angle of a second tangent plane contacting the second point with respect to a first tangent plane contacting the first point is within 60 ° . A base, a transparent first electrode, an organic semiconductor layer including a light-emitting layer, and a second electrode, in that order;
The surface of the second electrode on the organic semiconductor layer side has a flat surface, and a plurality of protrusions protruding from the flat surface toward the base,
The average pitch of the plurality of protrusions is 50 nm to 5 μm, the average aspect ratio of the plurality of protrusions is 0.01 to 1,
80% or more of the plurality of protrusions have a predetermined curved surface,
The predetermined curved surface is defined as an arbitrary point on the predetermined curved surface as a first point, and a point shifted by 1/10 of the average pitch from the first point toward a center point of the convex portion is defined as a second point. When you make a point,
An organic light emitting diode, wherein an inclination angle of a second tangent plane contacting the second point with respect to a first tangent plane contacting the first point is within 60 °. The organic light emitting diode according to claim 2 , wherein an area ratio of the flat surface to a surface of the second electrode on the organic semiconductor layer side is 5 to 50%.

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