JP2011203701A - Diffraction grating substrate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a diffraction grating substrate which is applicable to a diffraction grating, a plasmonic polycrystal, or the like for improving light extraction, and reduces color shift due to light diffraction.SOLUTION: The diffraction grating substrate has periodic grating structures having a pitch of 150 to 1,500 nm. Furthermore, the diffraction grating substrate has a structure where units having periodic grating structures different in at least one of pitch, height, and grating orientation are disposed at random, and it is preferable that an area of each of the units is 3 to 1,000,000 μm.

Description

  The present invention relates to a diffraction grating substrate applicable to organic EL, fluorescence, LED and the like used for displays, illumination, and the like, and an optical system using the same.

  In recent years, in order to improve the light emission efficiency of light emitting devices such as organic EL, fluorescent light, and LED, improvement of light emitting materials, lowering of voltage, improvement of light extraction efficiency, and the like have been studied.

  As a method for improving the light extraction efficiency, introduction of a light scattering layer or a low refractive index layer has been studied (for example, Patent Document 1, Patent Document 2, etc.). Furthermore, a method of increasing the light extraction efficiency by deflecting the traveling direction of light in the waveguide mode toward the light emitting device surface by utilizing light diffraction is also known (for example, Patent Document 3). In addition, a technique has been devised in which a metal periodic lattice structure or a fine particle dispersion is provided in the vicinity of the light emitting portion and the surface plasmon is excited to extract light outside with high efficiency (for example, Patent Document 4, Patent Document). 5, Non-Patent Document 1, Non-Patent Document 2, Non-Patent Document 3, Non-Patent Document 4, Non-Patent Document 5, etc.).

  Propagation type surface plasmon on a metal surface is a surface in which a polarization wave of free electrons generated by electromagnetic waves (such as visible light) incident on a conductor surface such as metal forms a transverse wave electric field on the surface. In the case of propagating surface plasmons existing on a flat metal surface, the propagating light cannot directly excite the plasmons because the propagating light dispersion line does not intersect the plasmon dispersion curve. However, if the metal surface has a periodic grating structure, the diffracted wave reflected by the grating crosses the dispersion curve of the plasmon, so the incident electromagnetic wave and the polarization wave of free electrons on the metal surface create a resonance state. (Non-Patent Document 6).

  At this time, the wave number vector of the surface plasmon has the same value as the wave number of light, and the exciton and light are coherently coupled to form a state of exciton polaritons. Polariton is a state where free-electron polarization waves and electromagnetic waves exchange energy by resonance. When the pitch and height of the periodic grating structure are substantially constant (the crystallinity of the periodic grating structure is high), the surface plasmon has one wave vector, and light with a specific incident angle and frequency (wavelength). Will come to join.

  For example, in Non-Patent Document 5, by using a periodically corrugated lattice structure to induce light and surface plasmon coupling for the light emitting layer in an organic light emitting device, the lateral transmission of emitted light and It has been proposed to prevent waveguides and increase the light output and efficiency of the structure. Theoretically, it is possible to couple up to 93% of the light emitted by the organic light emitting material in the organic EL light emitting device.

  Non-Patent Document 3 shows that the luminous efficiency of blue light by ultraviolet light excitation of a semiconductor quantum well structure is enhanced by the periodic structure of silver. Non-Patent Document 4 also shows that the luminous efficiency of the LED is enhanced by the periodic structure of silver.

JP 2008-235605 A International Publication No. 02/37568 Japanese Patent No. 3503579 Japanese Patent Laid-Open No. 2004-31350 JP 2009-158478 A

Opt. Lett., 30, 2302 (2005) Enhancement of EL through atwo-dimensional corrugated metal film bygrating-induced surface plasmon crosscoupling Appl. Phys. Lett., 93, 051106 (2008) Enhancement of surface plasmon-mediatedradiative energy transferthrough a corrugated metal cathode in organiclight-emitting devices Nature Mater., 3,601 (2004) Surface Plasmon enhanced light emittersbased on InGaN quantum wells Appl. Phys. Lett., 77, 15, 2295 (2000) Optimization of the emission characteristics of LED by SP and surface waveguide mode Appl.Phys.Lett., Vol.80, No.20, (2002) Basics of Optical Nanotechnology 35 (2003)

  It is an object of the present invention to provide a diffraction grating substrate that can be applied to a diffraction grating for improving light extraction, a plasmonic crystal, and the like, and that can reduce color shift caused by light diffraction.

  In order to solve the above problems, the present inventor has found that a color shift caused by light diffraction is reduced by using a diffraction grating having a periodic grating structure with a pitch of 150 nm to 1500 nm on the substrate. Furthermore, by arranging the units of the periodic grating structure with at least one of pitch, height, and grating orientation on the substrate at random to form a polycrystalline diffraction grating, the color shift caused by light diffraction is further reduced. I found out. Furthermore, when the substrate is a plasmonic crystal, the present inventors have found that surface plasmon resonance is used to improve the light energy extraction efficiency and to reduce the level of color shift visibility due to light diffraction. The plasmonic crystal here refers to, for example, a polycrystalline diffraction grating coated with a metal film, a flat metal film formed and then patterned. In particular, a polycrystalline concavo-convex base material in which units having a periodic lattice structure different in at least one of pitch, height, and lattice orientation are randomly provided on the surface is formed, and a metal film is coated on the polycrystalline concavo-convex substrate By doing so, it was found that a plasmonic polycrystalline substrate can be easily formed.

The diffraction grating substrate of the present invention is a substrate having a periodic grating structure with a pitch of 150 nm to 1500 nm. Further comprising pitch, a unit having at least any one is different periodic grating structure height and the grating orientation are arranged in random structure, and wherein the area of the unit is 3μm ² ~1000000μm ^2.

  In the diffraction grating substrate of the present invention, the diffraction grating substrate is preferably made of a resin.

  In the diffraction grating substrate of the present invention, the diffraction grating substrate is preferably made of metal. In this case, it can be applied as a plasmonic polycrystalline substrate.

  The diffraction grating substrate of the present invention preferably has a structure in which a metal thin film is coated on the surface of the diffraction grating substrate. In this case, it can be applied as a plasmonic polycrystalline substrate.

  In the diffraction grating substrate of the present invention, the metal periodic grating structure preferably has a height of 10 nm to 200 nm.

  In the diffraction grating substrate of the present invention, the unit shape is preferably rectangular or square.

  In the diffraction grating substrate of the present invention, the interval between the units is preferably 100 μm or less.

  In the diffraction grating substrate of the present invention, it is preferable that the deviation of the grating orientation of the metal periodic grating structure formed in each unit is 15 ° or less.

  In the diffraction grating substrate of the present invention, the metal periodic grating structure is preferably arranged in a six-way closest packed grating.

  In the diffraction grating substrate of the present invention, the metal is preferably at least one selected from metals consisting of silver, aluminum, and gold.

  In the diffraction grating substrate of the present invention, the pitch is preferably in the range of ± 200 nm of the emission center wavelength.

  The diffraction grating of the present invention can be applied to a diffraction grating for improving light extraction, plasmonic polycrystal, and the like, and can reduce color shift caused by light diffraction. In particular, when applied as a plasmonic crystal, the surface plasmon resonance can be used to improve the light emission efficiency of the light emitting device and reduce the color shift.

The electron micrograph of the plasmonic lattice board | substrate which concerns on embodiment of this invention. The electron micrograph of the plasmonic lattice board | substrate which concerns on embodiment of this invention. The schematic diagram of the plasmonic polycrystalline substrate which concerns on embodiment of this invention.

  Embodiments according to the present invention will be described in detail below.

The diffraction grating substrate of the present invention is a substrate having a periodic grating structure with a pitch of 150 nm to 1500 nm. Among them, pitch, units having at least any one is different periodic grating structure height and the grid orientation has a structure that is randomly arranged, it is preferable that the area of the unit is 3μm ² ~1000000μm ^2. There is no limitation on the material constituting the diffraction grating substrate, and any of dielectric, semiconductor, and metal can be used. In the present specification, a diffraction grating substrate made of metal is particularly called a plasmonic crystal substrate.

A plasmonic crystal substrate can be obtained, for example, by coating a metal film on a crystalline diffraction grating made of a dielectric material, or by forming a flat metal film and then patterning it, but the manufacturing method is particularly limited. There is no. The plasmonic crystal of the present invention is characterized in that it is a substrate having a metal periodic lattice structure with a pitch of 150 nm to 1500 nm. Further, the pitch, the unit having at least any one is different periodic grating structure height and the grid orientation has a structure that is randomly arranged, it is preferable that the area of the unit is 3μm ² ~1000000μm ^2. That is, a plurality of regions (units) having a metal periodic grating structure are provided on the substrate. Furthermore, a plurality of regions (units) having different periodic metal grating structures may be provided on the substrate. In order to obtain a periodic grating structure of different metals, at least one of the pitch, height, and grating direction of the metal periodic grating structure may be different. The color shift generated due to the diffraction derived from the periodic grating structure can be greatly suppressed.

  The metal periodic grating structure may be provided in any manner as long as the metal has a periodic structure. For example, the metal periodic grating structure can be provided by forming a metal film on the diffraction grating substrate on the surface. . Hereinafter, a configuration example of the diffraction grating substrate of the present invention is shown in FIGS. In FIGS. 1 and 2, a plasmonic crystal substrate will be described as an example of a polycrystalline diffraction grating substrate.

  The plasmonic crystal substrate shown in FIG. 1 has a metal periodic lattice structure. Specifically, each unit is set to a pitch of 500 nm. The plasmonic crystal substrate shown in FIG. 2 has a metal periodic lattice structure. Specifically, each unit is set to a pitch of 250 nm and a height of 180 nm.

  Furthermore, it can be provided by forming a metal film on a polycrystalline diffraction grating substrate in which regions having different periodic grating structures are randomly formed on the surface. Hereinafter, one structural example of the polycrystalline diffraction grating substrate of the present invention will be described with reference to FIG. In FIG. 3, a plasmonic polycrystalline substrate will be described as an example of a polycrystalline diffraction grating substrate.

  The plasmonic polycrystalline substrate shown in FIG. 3 has a configuration in which units having different lattice orientations and pitches of a metal periodic lattice structure are randomly arranged. Specifically, in each unit, a metal periodic lattice structure is formed in a hexagonal close-packed lattice arrangement, and four periodic lattice structures whose crystal orientations (hexagonal close-packed lattice arrangement) are different by 15 ° are randomly selected. The case where it arrange | positions to is shown. Further, the pitch is set to 450 nm, 550 nm, and 650 nm for each crystal orientation.

(unit)
In order to effectively reduce the color shift, it is preferable that adjacent units have different metal periodic grating structures (different grating orientations and / or pitches in FIG. 3). Moreover, each unit may be able to have an area capable of inducing the surface plasmon coupling, the area of each of the plurality of units, it is preferable to 3μm ² ~1000000μm ^2. The specific unit area can be determined by the size of the periodic grating structure. That is, in order to prevent the transmitted light from being transmitted and guided in the lateral direction and to increase the light output and efficiency of the structure, the number of lattices in the unit may be 5 or more in each lattice direction. For example, when the unit shape is square, the lattice shape is a square lattice, and the lattice size is 500 nm, the lower limit of the unit size (the length of each side of the unit) is 500 nm × 5 = 2500 nm. On the other hand, since it becomes easy to visually recognize each unit when the unit is larger than 1000 μm, it is preferably 1000 μm or less (in terms of area, 1 million μm ² or less).

  In addition, it is preferable to narrow the gap between the units. Specifically, the gap between the units is preferably 100 μm or less, more preferably 30 μm or less, which is difficult for humans to visually recognize. The unit shape is not particularly limited, and may be, for example, a triangle, a hexagon, or an octagon. However, since the manufacturing process can be simplified, rectangular or square units may be arranged as shown in FIG. preferable. Further, the arrangement of the units is not particularly limited, but it is preferable to arrange the units in a lattice shape in consideration of narrowing the gap between the units and the manufacturing process.

(Periodic lattice structure)
An object of the present invention is to improve the light emission efficiency of organic EL, fluorescence, LED, etc. used for display, illumination, etc. by surface plasmon. For this purpose, it is necessary to efficiently excite surface plasmon coupling in a target wavelength band with a metal periodic grating structure. A higher effect can be obtained when the metal periodic lattice structure is one-dimensional (dot / periodic structure) than when it is one-dimensional (line / space periodic structure). Further, even when the periodic grating structure is two-dimensional, the arrangement having the periodic structure in three directions (lattice crossing angle = 60 degrees, 6-way fine packing) than the arrangement having the periodic structure in two directions (lattice crossing angle = 90 degrees). (Lattice arrangement) is preferable because there are many conditions that can excite surface plasmons.

  That is, in the case of the two-dimensional 6-way close packed lattice arrangement shown in FIG. 3, since the periodic structure is produced in three directions, the lattice arrangement is the most excellent in the efficiency of resonating the diffracted light with the surface plasmon. The improvement effect is high.

(pitch)
The pitch of the periodic grating structure is preferably set to a size that is about the effective wavelength of the light emitted from the light emitting device. Therefore, the pitch is appropriately selected depending on the wavelength of the emitted light. For example, when a light-emitting device for visible light is assumed, it is in the range of 150 to 1500 nm, more preferably 400 to 1000 nm. More preferably, it is preferably approximately the same as the wavelength to be emitted (wavelength to be emitted ± 200 nm or the like), and the most preferable range is 200 to 1000 nm.

  In applications where white light is desired to be emitted, it is preferable to randomly arrange units having a red pitch, units having a green pitch, and units having a blue pitch.

(height)
The height of the periodic grating structure may be 5 to 500 nm, more preferably 10 to 200 nm, and still more preferably 20 nm to 100 nm. If it is 500 nm or less, the cause of the short circuit of an electrode does not occur easily, and if it is 5 nm or more, the efficiency of surface plasmon coupling is improved.

(Orientation of periodic grating structure)
The reference axis of the grating is arbitrarily determined, and the periodic grating structure is shifted from there to the grating crossing angle. The azimuth angle of the periodic grating structure of each unit is ¼ or less of the lattice crossing angle (for example, 15 ° or less in the case of a 6-way close packed lattice arrangement), more preferably 1/10 or less (for example, 6-way maximum) In the case of a closely packed lattice arrangement, it is preferable that the shift is 6 ° or less))) because the color shift due to light diffraction is less visible.

(Metal type)
The metal that coats the substrate having the periodic grating structure on the surface is appropriately selected depending on the target wavelength. For example, when used for an ultraviolet light emitting device, aluminum having a high frequency (plasma frequency) at which metal free electrons cannot follow the vibration of electromagnetic waves is preferable, and for a light emitting device in the visible blue to green, for example, 380 nm to 650 nm region. When used, it is preferable to use silver or aluminum exhibiting high reflectivity in the entire visible wavelength range, and it is particularly preferable to use silver having a small absolute value of the real part of the dielectric constant. In the red in the visible range, for example, 580 to 780 nm, it is preferable to use silver or gold having high reflectance in the wavelength band.

  The material used for the substrate may be a material that is substantially transparent in the target wavelength range. For example, when used for a light-emitting element and a light-emitting device for the visible range, silicon (Si) oxide, nitride, halide, carbide alone or a composite thereof, aluminum (Al), chromium (Cr), yttrium (Y), zirconia (Zr), tantalum (Ta), titanium (Ti), barium (Ba), indium (In), tin (Sn), zinc (Zn), magnesium (Mg), calcium (Ca), cerium Use of oxides, nitrides, halides and carbides of metals such as (Ce) and copper (Cu), or composites thereof (dielectrics in which other elements, simple substances or compounds are mixed in a single dielectric) Can do. Polymethyl methacrylate resin, polycarbonate resin, polystyrene resin, cycloolefin resin (COP), cross-linked polyethylene resin, polyvinyl chloride resin, polyarylate resin, polyphenylene ether resin, modified polyphenylene ether resin, polyetherimide resin, polyether Amorphous thermoplastic resins such as sulfone resin, polysulfone resin, polyether ketone resin, polyethylene terephthalate resin (PET), polyethylene naphthalate resin, polyethylene resin, polypropylene resin, polybutylene terephthalate resin, aromatic polyester resin, polyacetal Resin, polyamide thermoplastic resins and other crystalline thermoplastic resins, acrylic, epoxy and urethane UV curable resins and resin substrates such as thermosetting resins are also used Rukoto can. Moreover, it can also be set as the structure which combined organic substances, such as a resin base material, and inorganic substances, such as glass fiber, as a base material. It is also preferable from the viewpoint of mass production that a resin base material is used as the base material because it is flexible and lightweight, or a roll manufacturing method can be easily applied.

  The plasmonic crystal substrate of the present invention can be produced by nanoimprint, EB drawing, photolithography, interference exposure and the like.

  A preferred method for producing a plasmonic crystal substrate will be specifically described below with an example.

(Original plate production)
First, a substrate is prepared. As the substrate, silicon (Si), silicon oxide, glass, gallium nitride, gallium arsenide, aluminum oxide, silicon carbide, or the like can be used.

  Next, after a resist film is formed on the substrate, the resist film on the substrate is exposed using a step-and-repeat type exposure apparatus (stepper) using a mask or a reticle. The shot is repeated so that the fine patterns of unit area formed on the mask or reticle are joined (joined), and the resist on the substrate is exposed (joined by repeated exposure). Therefore, the continuous concavo-convex lattice pattern and the continuous fine pattern formed by joining the unit fine patterns are transferred to the resist. In each shot, the amount of overlap between the shots (the amount of the portion where the number of exposures becomes plural) can be arbitrarily set so that the joining is uniform. After the resist film on the substrate is exposed, development is performed by a method suitable for the resist, and then the substrate is etched to form an uneven lattice pattern.

  Here, the area of the portion where the continuous concavo-convex grid pattern is formed is preferably as large as possible for application to various applications, and the diameter of the minimum circumscribed circle of the portion where the concavo-convex lattice pattern is formed is 20 cm or more. It is preferable that it is 25 cm or more, and it is most preferable that it is 30 cm or more. This size increases the number of devices to which the plasmonic crystal substrate can be applied. On the other hand, there is no technical limitation on the upper limit of the size. For example, according to the interference exposure method, it is possible to form a pattern with a moderate periodicity over an area of 100 cm square or more. The diameter is about 150 cm. The shape of the concavo-convex lattice pattern is not particularly limited, but a dome shape or a conical shape having a good releasability is preferable.

(Transfer to resin)
Next, the shape of the obtained original plate is transferred to a resin. There is no particular limitation on the transfer method, and any method such as thermal transfer to a thermoplastic resin, transfer to a UV curable resin, or transfer to a thermosetting resin can be employed. The transfer product obtained here is a diffraction grating substrate made of a dielectric.

(Ni stamper production)
The obtained transfer film is subjected to a conductive treatment and then electroplated with nickel or the like to produce a nickel stamper. The steps of transferring to the resin and preparing the Ni stamper are not essential, but it is preferable to go through these steps in order to reduce the chance of damaging the original. In view of mass productivity, it is preferable that the Ni stamper is processed into a cylindrical shape by a technique such as welding and processed into a stamper for continuous transfer.

(Shaping)
The shape of the Ni stamper obtained as described above is transferred to a resin. There is no particular limitation on the transfer method, and any method such as thermal transfer to a thermoplastic resin, transfer to a UV curable resin, or transfer to a thermosetting resin can be used. It is preferable to use transfer to a UV curable resin from the viewpoint of reducing damage to the surface. In view of mass productivity, it is more preferable to use a roll-to-roll UV transfer technique.

(Metal thin film formation)
As a method for forming a metal thin film, a dry film forming method such as sputtering, vacuum evaporation, ion plating, and CVD and a wet film forming method such as electroless plating can be applied. However, the film thickness uniformity, reproducibility, and low material loss From the viewpoint of the above, the sputtering method is preferably used.

(Light emitter layer formation)
(A For fluorescent materials)
For the thin film forming method of fluorescent material, dry film forming methods such as vacuum deposition, sputtering, ion plating, and CVD as well as wet film forming methods such as electroless plating and solution casting can be applied. From the viewpoint of the above, it is preferable to use a dry film forming method. The fluorescent material is excited by absorbing light from the light emitting element, and converts it into light having a wavelength different from the light emission color of the light emitting element (for example, having a complementary color relationship). YAG phosphor, nitride phosphor, Other phosphors can be used. For example, nitride phosphors / oxynitride phosphors mainly activated by lanthanoid elements such as Eu and Ce, lanthanoid phosphors such as Eu, and alkalis mainly activated by transition metal elements such as Mn Earth halogen apatite phosphor, alkaline earth metal borate halogen phosphor, alkaline earth metal aluminate phosphor, alkaline earth silicate, alkaline earth sulfide, alkaline earth thiogallate, alkaline earth silicon nitride At least selected from organic and organic complexes mainly activated by lanthanoid elements such as germanate or lanthanoid elements such as Ce, rare earth aluminates, rare earth silicates or Eu Any one or more are preferable. These phosphors can use phosphors having emission spectra in yellow, red, green, and blue by the excitation light of the light-emitting element, and emission spectra in yellow, blue-green, orange, etc., which are intermediate colors between them. A phosphor having the following can also be used. By using these phosphors in various combinations, light emitting devices having various emission colors can be manufactured.

(B For organic EL)
A multilayer comprising at least three layers of an anode conductive layer, a hole injection layer, a hole transport layer, a light-emitting layer, an electron transport layer, an electron injection layer, and a cathode conductive layer on the substrate, including at least an anode conductive layer, a light-emitting layer, and a cathode conductive layer, sequentially. An organic light emitting diode element can be fabricated by stacking. Regarding the hole injection layer, hole transport layer, light emitting layer, electron transport layer, and electron injection layer, one layer may serve two or more functions, or the hole transport layer and the electron transport layer may be omitted. . A light emitting layer is necessary as a place where holes and electrons meet. The simplest system need only have a light emitting layer sandwiched between an anode conductive layer and a cathode conductive layer. A method for producing the anode conductive layer, hole injection layer, hole transfer layer, light emitting layer, electron transfer layer, electron injection layer, and cathode conductive layer used in the present invention is not particularly limited, but a general bottom emission organic light emitting diode is used as an example. The explanation is as follows. That is, the anode conductive layer and the cathode conductive layer are formed by a vacuum vapor deposition method or a sputtering method, and the hole injection layer, the hole transfer layer, the light emitting layer, the electron transfer layer, and the electron injection layer are formed by an organic vapor deposition method or a thin film coating method.

  Since lamination of each layer is performed in order from a layer close to the base material, an anode conductive layer is first formed. In the case of a bottom emission organic EL, the anode conductive layer must be transparent, and therefore, a transparent conductive material such as ITO (Indium Tin Oxide), ZnO (Zinc Oxide), or ZTO (Zinc Tin Oxide) is selected.

  Next, an aromatic amine compound or the like is formed as a hole injecting / moving layer. Aromatic amine compounds such as α-NPD and CuPc are most often used as hole transport materials because they have appropriate ionization potential and hole transport properties and are electrochemically reversible. Next, a light emitting layer is laminated. Examples of the material used alone for the light emitting layer include fluorescent dye compounds such as BBA and DTE, but holes and electron transport compounds may be doped with the fluorescent dye compound. It is preferable to use a phosphorescent material instead of a fluorescent material because the theoretical conversion efficiency is improved from about 25% to about 100%.

Next, an electron transport layer is laminated. As the electron transport layer, an oxadiol type (such as PBD) or a triazole type (such as TAZ) is used. Use of a metal complex (such as Alq ₃ ) substance is convenient because it can serve both as an electron transporting layer and a light emitting layer.

  Finally, a cathode conductive layer is laminated. The material for the cathode conductive layer is generally formed by laminating Al, Ag, an Al / Ag alloy or the like after adding a very small amount of LiF or Li-based compound. In the present invention, the periodic grating structure produced on the substrate generates diffracted light of the light emitted from the EL, and creates a resonance state with the surface plasmon of the cathode. The light emitted from the organic EL element is directed toward the base material, which is the extraction surface, and is directed toward the metal surface of the cathode, which cannot be extracted. However, the light is temporarily transferred to the energy of the surface plasmon by the plasmonic crystal on the cathode surface. And then emitted as high-intensity radiation from the cathode surface toward the extraction surface. Radiant light emitted from the cathode surface has high directivity and can improve light extraction efficiency. For this purpose, the material of the cathode conductive layer is preferably a material having a high electron transport number and a low loss (a material having a low work function). Therefore, Ag, Au, or the like is selected, or Al or the like, which is generally selected. However, the material selection is not necessarily limited to these.

  In the case of a bottom-emitting organic light-emitting diode, an anode conductive layer is first formed on the structural surface side of a transparent substrate provided with a periodic lattice structure, followed by a hole injection layer, a hole transport layer, a light-emitting layer, and an electron transport layer. Then, an electron injection layer and a cathode conductive layer are sequentially laminated to complete. By this operation, the shape of the fine irregularities of the periodic grating structure is transmitted to the cathode conductive layer, and the cathode conductive layer has the shape of a plasmonic crystal. In order for the shape to be transmitted, the thickness of each layer needs to be as thin as possible. However, these layers of the organic light emitting diode are usually formed with a thickness of about 20 to 100 nm, and there is no problem.

An example of the embodiment of the present invention will be described below. As long as the concept of the present invention is used, the target structure, configuration, and system are not necessarily limited.
[Example 1]
(Original plate production)
A Si substrate having a diameter of 300 mm was used as a wafer size, and a pattern was formed within a diameter of about 280 mm inside the substrate. The pattern was formed by a step-and-repeat exposure method using a 10 mm × 10 mm mask on which the following plurality of unit patterns were drawn. That is, in this embodiment, the pitch and the lattice orientation are different for each unit.

In-unit pitch: 530 nm, 590 nm, 650 nm
Lattice height: 50 nm
Periodic lattice shape: lattice crossing angle = 60 degrees (6-way close-packed structure)
Lattice orientation: 0 °, 15 °, 30 °, 45 °
Unit size: 50μm × 50μm
Cross-sectional shape: almost rectangular

(Replication with resin)
A glass plate having a thickness of 3 mm for the purpose of applying 0.01 mm of UV curable resin on the Si original plate on which the pattern is formed, placing PET having a thickness of 0.2 mm on the Si original plate, and further suppressing curling of the film during exposure. Was placed on the film. Then, an ultraviolet lamp having a central wavelength of 365 nm and an irradiation intensity of 1000 mJ / cm ^{2 was} irradiated from the film side for 1 minute to transfer the fine uneven grating.

(Ni stamper production)
The obtained transfer film was subjected to a conductive treatment and then electroplated with nickel or the like to produce a nickel stamper.

(UV shaping)
An ultraviolet curable resin is applied to a Ni stamper by 0.01 mm, a PET having a thickness of 0.2 mm is placed on the Ni original plate, and a glass plate having a thickness of 3 mm is placed on the film for the purpose of suppressing curling of the film during exposure. placed. Then, an ultraviolet lamp having a central wavelength of 365 nm and an irradiation intensity of 1000 mJ / cm ^{2 was} irradiated from the film side for 1 minute to transfer the fine uneven grating.

(Production of organic EL element)
An organic EL element was produced using the substrate after UV shaping. The organic EL element is made of a PET film having a substrate with irregularities. On top of that, a buffer layer, a cathode, an electron transport layer, a hole transport layer, and an anode were laminated in this order. Here, the electron transport layer also serves as the light emitting layer. The material and film thickness of each layer and the film formation method are as follows.
(1) Buffer layer: SiO ₂ 100 nm Vacuum deposition (2) Cathode: Ag 40 nm Vacuum deposition (3) Electron transport layer: Tris- (8-hydroxyquinoline) aluminum (Alq ₃ ) 40 nm Vacuum deposition (4) Hole transport layer: N, N′-diphenyl-N, N′-bis (1-naphthyl)-(1,1′-biphenyl) -4,4′-diamine (NPB) 60 nm Vacuum deposition (5) Anode: ITO 150 nm sputtering

[Comparative Example 1]
Comparative Example 1 was obtained by forming an organic EL element on a PET base material on which a flat UV curable resin was laminated by the same operation as Example 1 using a smooth Ni plate having no periodic grating structure. .

[Example 2]
An organic EL device was formed in exactly the same manner as in Example 1, using a PET film having a periodic structure in which the entire surface had the same structure, that is, no unit, and the pitch and lattice orientation of the entire surface were completely aligned. This was designated as Example 2. The pitch was 590 nm.

[Evaluation of EL intensity]
For comparison between the EL spectrum and the EL intensity, the luminance was measured with a spectral radiance meter SR-3 manufactured by Topcon Technohouse. The measurement direction was set to be perpendicular to the light emitting surface. The results are shown in Table 1. Table 1 shows values normalized by setting the Lv value of Comparative Example 1 to 1. As is clear from Table 1, it can be seen that the brightness of Example 1 and Example 2 in which unevenness is provided on the surface is high.

[Evaluation of color shift]
In the state in which each of the example and each comparative example was made to emit light, white cylindrical paper was placed around the sample, and the image projected on the paper was visually observed. As a result, in Example 1 and Comparative Example 1, the color of the entire surface was the same, whereas in Example 2, a rainbow-like color (spectrum) was observed every 120 ° in the circumferential direction. This is because in Example 2, the light emitted by diffraction originating from the periodic structure was separated for each wavelength, but there was almost no visible color shift. In Example 1, since each unit has various periods and lattice orientations, diffraction in each unit is randomized and projected onto the cloth, so that the same color is felt at a level that can be visually recognized by humans.

  The diffraction grating substrate of the present invention is suitably used as a substrate for a light emitting device such as a plasmonic polycrystalline substrate.

Claims (12)

  A diffraction grating substrate having a periodic grating structure with a pitch of 150 nm to 1500 nm. Pitch, claims unit having at least any one is different periodic grating structure height and the grid orientation has its structure arranged randomly, the area of the unit is characterized in that it is a 3μm ² ~1000000μm ² The diffraction grating substrate according to 1.   The diffraction grating substrate according to claim 1 or 2, wherein the diffraction grating substrate is made of a resin.   The diffraction grating substrate according to claim 1, wherein the diffraction grating substrate is made of metal.   4. The diffraction grating substrate according to claim 3, wherein a surface of the diffraction grating substrate is covered with a metal thin film.   6. The polycrystalline diffraction grating substrate according to claim 4, wherein the metal periodic grating structure has a height of 10 nm to 200 nm.   The diffraction grating substrate according to any one of claims 2 to 6, wherein the unit has a rectangular or square shape.   The diffraction grating substrate according to claim 2, wherein an interval between the units is 100 μm or less.   The diffraction grating substrate according to any one of claims 4 to 8, wherein a deviation of a grating orientation of the periodic metal grating structure formed in each unit is set to 15 ° or less.   The diffraction grating substrate according to any one of claims 4 to 9, wherein the metal periodic grating structure is arranged in a hexagonal close-packed grating.   The diffraction grating substrate according to any one of claims 4 to 10, wherein the metal is at least one selected from silver, aluminum, and gold.   The diffraction grating substrate according to any one of claims 1 to 11, wherein the pitch is in a range of ± 200 nm of the emission center wavelength.